Coral recruitment, thermal stress and coral reef community structure in St. John, US Virgin Islands by Puerto Rico Sea Grant

Project Title: Coral recruitment, thermal stress and coral reef community structure in St. John, US Virgin Islands

Date: 30 September 2008

Investigators and affiliation:

Project Number: R-101-1-06

(1) Peter J. Edmunds PhD, Department of Biology, California State University, 18111 Northridge, CA 91330 (PI) Contact: Phone: 818.677.2502, e-mail: peter.edmunds@csun.edu

(2) Daniel H. Green BS, Department of Biology, California State University, 18111 Northridge, CA 91330 (graduate student supported to complete the majority of the research)

Dates covered (1) Original Grant: 1 May 2006 – 30 April 2008 (2) No cost extension: 1 May 2008 – 30 September 2008

A. Executive Summary

Objectives. The objectives of this award were: (1) to assess the extent to which spatio-temporal variation in coral recruitment along the south coast of St. John maps on to variation in seawater temperature, (2) assess the role of thermal stress in determining the success of juvenile corals, and (3) develop educational outreach activities pertaining to the project in the VI. All three objectives have been fulfilled, notably by:

• Describing a high degree of spatio-temporal variation in coral recruitment along the south coast of St. John, with high densities of recruits to the east, low densities to the west, and a significant and inverse relationship with the daily variation in seawater temperature.

• Showing that the two common substratum types in St. John – igneous and carbonate rock – differ slightly in temperature, and are associated with small differences in coral growth and photophysiology. While these differences have considerable biological value they are unlikely to explain a large amount of variability in coral recruitment in this location.

• Developing a strong outreach program involving a K-12 educator, the instruction of “eco-camps” for children from Caribbean island nations, the creation of a lesson plan and field guide suitable for children, and the development of strong ties between CSUN and a local high school in California.

Advancement of the field. The significance of this project lies in its ability to establish links between ecological processes – coral recruitment and post-settlement success – and decadal-scale dynamics of coral reefs along the south coast of St. John. In contrast to the expectation of broadly similar coral recruitment over a spatial scale of 10 km, this study reveals strong spatial heterogeneity that is highly clina l, repeatable over 2 years, and related strongly to a physical gradient of variability in seawater temperature. This is the first study to demonstrate that the daily variability in seawater temperature is inversely related to coral recruitment, with more recruits occurring in locations with multiple stable thermal regimes. In addition to addressing variation in pre-settlement and settlement events, this study provides a rare example of an investigation of the effects of substratum choice for the success of juvenile corals. Surprisingly, while their settlement location has de tectable effects, these do not lead to fitness consequences as assessed by mortality.

Research Impact. At this stage of the project, less than a month after the final data have been collected, it is impossible to know what kind of higher order “societal/scientific benefits” will accrue. Such effects are likely to become clear with the passage of time, the appraisal of manuscripts arising from this work as they pass through review, and the career paths of the principal players involved with this project. However, at this stage it is likely that the present work will: (a) have important implications for the management of coral reef resources though the VI National Park in the Virgin Islands, (b) scientific infrastructure within the United States through the effective training of graduate students, (b) contribute to the development of local environmental policies designed to protect reefs and reduce sedimentation, and (c) enhance K-12 education through the forging of strong ties between CSUN, K-12 educators, schools, and local children.

Other important impacts or products (1) Students and teachers supported (note, D. Green, N. Formel, and C. Didden benefited directly from UPR-SG funds that supported the work they were involved in; the remaining personnel benefited indirectly from UPR-SG support, for example from sharing housing supported in part, from UPR-SG funds).

i. Daniel H. Green – graduate student primarily responsible for this project. Thesis topic “Spatio-temporal variation in coral recruitment along the south coast of St. John, USVI” (graduation expected 12/2008). E-mail: daniel.green.669@csun.edu

ii. Mairead E. Maheigan – graduate student who assisted with fieldwork in St. John. Thesis topic “Spatial scale of morphological variation of the corals Pocillopora verrucosa and Porites porites” (graduated 6/2007). E-mail: oceancat79@hotmail.com

iii. Hollie M. Putnam – graduate student who assisted with fieldwork in St. John. Thesis topic “The effects of temperature fluctuations on coral physiology” (graduated 6/2008). E-mail: hollieputnam@gmail.com

iv William Goldenheim graduate student who assisted with fieldwork in St. John. Thesis topic “The effects of flow and temperature on the photophysiology of reef corals” (graduated expected 2010). E-mail: wgoldenheim@gmail.com

v. Nicholas Colvard graduate student who assisted with fieldwork in St. John. Thesis topic “The effect of reef substratum in modulating light fields around corals and their effect of photophysiology” (graduated expected 2010). E-mail: ncolvard@msn.com

vi. Caitlin Cameron – new graduate student who assisted with fieldwork in St. John. Thesis topic TBA. E-mail: Caitlin_Cameron@umit.maine.edu

vii. Nathan Formel – undergraduate student (Puerto Rico resident) who assisted with fieldwork. Undergraduate honors thesis topic “The effect of mangrove forest proximity on percent coral and algae cover in Lameshur Bay, St John, US Virgin Islands.” E-mail: formel.n@neu.edu

viii. Lianne Jacobson undergraduate student who assisted with St. John fieldwork. E-mail: jacobson.l@neu.edu

ix. Craig Didden – K-12 educator who assisted with outreach activities in St. John and California. E-mail: diddenc2003@yahoo.com

(2) Conference Proceedings – talks

2008 Colvard N, Edmunds PJ. Coral reef invertebrate benthic assemblages in St. John, US Virgin Islands and southern Taiwan. TaiwanAmerica Cooperative Coral Research Workshop, Kenting, Taiwan.

2008 Edmunds PJ. The comparative demographic of two scleractinian corals on a shallow Caribbean reef. ICRS, Fort Lauderdale, FL

2007 Green DH, Edmunds PJ. The effects of temperature in mediating spatio-temporal variation in coral recruitment along the south coast of St. John, US Virgin Islands. Association of the Marine Laboratories of the Caribbean, St. Thomas, USVI

2007 Green DH, Edmunds PJ. Detecting spatial variation in coral recruitment associated with temperature along the southern coast of St. John, US Virgin Islands. CSUN Student Research and Creative Works Symposium, Northridge, CA.

2007 Green DH, Edmunds PJ. Exploring variation in coral recruitment through temperature along the southern coast of St. John, US Virgin Islands. Western Society of Naturalists, Ventura, CA.

2006 Edmunds PJ. Decadal-scale monitoring of the coral reefs in Lameshur Bay, St. John: patterns of change, causal processes, and likely outcomes. Presentation at the 40th anniversary of the Virgin Islands Ecological Resource Station, St. John, USVI.

(3) Conference Proceedings – posters

2008 Green, DH. Edmunds PJ. Investigating spatial variation in coral recruitment with respect to temperature along the southern coast of St. John, US Virgin Islands. ICRS, Fort Lauderdale, FL

2007 Colvard N, Edmunds PJ. Decadal-scale changes in population density of non-scleractinian invertebrates on a Caribbean reef. Western Society of Naturalists, Ventura, CA

2007 Didden C, Edmunds PJ. Variation in the population dynamics of juvenile Caribbean corals over 10 km of coast. Western Society of Naturalists, Ventura, CA

2007 Green DH, Edmunds PJ. The effects of temperature in mediating spatio-temporal variation in coral recruitment along the south coast of St. John, US Virgin Islands. Benthic Ecology Meetings, Atlanta, Georgia.

2006 Green, DH, Edmunds PJ (2006) A decadal shift in the relative abundance of corals on Caribbean reefs that favors a weedy species. Western Society of Naturalists, Redmond, Washington State.

(4) Publications

Green DH, Edmunds PJ. Spatio-temporal variation in coral recruitment and its association with temperature in St. John, USVI. Marine Ecology Progress Series (in prep) Green DH, Edmunds PJ, Pochon X, Gates RD. The effects of substratum type on the growth, mortality, and photophysiology of juvenile corals in St. John, US Virgin Islands. Journal of Experimental Marine Biology and Ecology (in prep)

2008 Rogers CS (and 25 others including PJ Edmunds). Ecology of coral reefs in the US Virgin Islands. P 303-373. In: Riegl BM, Dodge RE (eds) Coral reefs of the USA (contains material supported by this grant).

2008 Green DH, Edmunds PJ, Carpenter RC. Increasing relative abundance of Porites astreoides on Caribbean reefs mediated by an overall decline in coral cover. Marine Ecology Progress Series 359:1-10

(5) Outreach deliverables

2008 Edmunds PJ, Didden C, Maheigan, L Allen-Requa. A lesson plan in coral reef ecology (downloadable at http://www.csun.edu/%7Embgsclub/edmunds.html)

2008 Edmunds PJ, Colvard N. A brief guide to marine invertebrates that are common on reefs in St. John.

Matching funds

Matching funds were provided for this project in the form of release time to Edmunds and Teaching Assistantships (TA) to Green. Release time was provided to Edmunds as a part of a negotiated policy that recognizes the workload associated with large research grants. In short, during this award CSUN provided 6 units of release time to complete research on funded projects in the Caribbean, of which 20% was used in the completion of the present research. This effort corresponded to ≈$5, 267/y ($10,534 for the duration of this award). TA positions are provided to eligible graduate students as a means to provide support while meeting the teaching obligations within the depar tment. During this award, Green received 11 TA positions amounting to $14,200 In addition to employment positions, Green received multiple stipends from CSUN and one academic award (California Pre-doctoral scholarship) which paid for national and international conference attendance and registration, totaling to a sum of ≈$6,000.

New extramural funds (total value - $23k [secured], $448k [pending])

(1) NSF-REU ($6,000) award in 2007 for a project addressing the long-term dynamics of reef-associated invertebrates in St. John, USVI. (awarded to N. Colvard).

(2) NSF-REU ($6,000) award in 2008 for a project addressing the underwater light field, POM, and plankton in the seawater flowing over the reefs of St. John (awarded to L. Jacobson).

(3) CSUN ($5,000) award in 2006 for a project addressing the genetic diversity of algal symbionts in tropical reef corals. Title “Assessing the genetic diversity of the algal symbionts of reef corals in St. John.”

(4) CSUN ($6,000) award in 2008 for a project addressing the needs for speedy analysis of data from St. John in order to support a competitive renewal proposal to NSF. Title “Long-term coral community dynamics in St. John, USVI: critical data analyses for an NSF renewal grant.”

(5) NSF-LTREB ($448k, pending) proposal (submitted 9 July 2008) to fund a 5 year extension of the existing long-term analysis of coral community dynamics (decision due by December 2008). Title “Long-term coral reef community dynamics in St. John USVI: 1987-2019.”

B. Final Report Narrative

A brief statement of the problem

Biome degradation has become a common trend on a global scale (Woodruff 2001), with coral reefs providing one of the highest profile examples of the potential consequences of such degradation (Hughes et al. 2003, Pandolfi et al. 2005). Disturbances are a routine part of the long-term dynamics of coral communities (Connell 1978), but in recent years disturbances affecting coral reefs have become more severe and have been dominated by disturbances of anthropogenic origin (Brown 1997, Buddemeier et al. 2004). Faced with these assaults, many reefs have lost a substantial fraction of their coral cover (Bellwood et al. 2004), and their community structure has changed so drastically that arguably “pristine” reefs were lost more than 300 years ago (Jackson 1997), and the prognosis for those remaining is poor (Knowlton 2001). Not surprisingly then, coral reef degradation is common in the near-shore habitats of Puerto Rico and the US Virgin Islands (Rogers et al. 2008). In areas adjacent to coastal development, the declines often can be attributed to local disturbances, but losses in locations less affected by anthropogenic disturbances such as in St. John, US Virgin Islands (e.g., Edmunds 2002, Rogers et al. 2008) illustrate the impacts of pervasive and large-scale phenomena that effectively are driven by events occurring elsewhere. Both local- and large-scale phenomena can result in extensive coral death, but only the former can be regulated with relative ease through resource management.

The most conspicuous signs of coral reef degradation are the declines in cover of corals, losses of reef fishes, and increases in macroalgae (Hughes 1994, Hughes et al. 2003, Bellwood et al. 2004). Together, these events have caused a drastic phase change in coral reef community structure (Bellwood et al. 2004), which is sufficient to challenge the ability of coastal resources to fulfill their “traditional” ecological, economic, and engineering functions. In other words, coral reefs that have undergone a phase change to algal dominance have a restricted capacity to support biodiversity, coastal fisheries, and tourist-based economies, and moreover, the reduced rates of accretion limit their capacity to provide coastal protection from the damaging effects of storms. In response to the degradation of coral reefs, marine protected areas (MPAs) have proliferated with the objective to protect marine resources through the management of human activities. The resource management decisions are based, in large part, on the scientific analyses of natural resources, with these analyses heavily biased towards the quantification of coral cover. Typically, declining coral cover is construed as “bad” and increases as “good” (Hughes & Tanner 2000).

However, while the loss of coral cover provides a conspicuous sign of habitat degradation, coral cover can be misleading with regards to the “condition” of the reef. For instance, on Jamaican reefs that have long been the proverbial “poster child” of reef degradation (Aronson & Precht 2001), stabilization of coral cover following an earlier loss was not an indication of improving conditions, rather it served to hide an impending demographic collapse (Hughes & Tanner 2000); my research from St. John has revealed a similar situation for one study reef on the south shore (Edmunds & Elahi 2007). The critical factor in the assessment of reef condition from coral cover is that changes in coral reef community structure, as assessed from such data, has a limited capacity to illuminate the mechanistic basis of the changes. Without such information, it is impossible to design effective management strategies, or to project (sensu Caswell 2001) how the reef might change in the future. The goal of this project was to augment a decadal-scale analysis of reefs in St. John (US Virgin Islands) with a mechanistic study designed to address two processes that are critical in determining the present day (and future) condition of the reefs:

(I) to what extent does the spatio-temporal variability of coral recruitment map onto variability in seawater temperature, and (II) what role is played by thermal stress in determining the post -settlement success of juvenile corals?

Additionally, the project sought to

(III) develop K-12 outreach activities to strengthen and support the societal impacts of the project, specifically by impacting in positive ways the educational environment in the VI and in CA.

These two research objectives have foundations in, yet provide a clear extension from, the 22 -year context of ecological change on the reefs of St. John that has been provided by my larger project in St. John. Both objectives were fully supported by the UPR-SG award, and this project has added a new dimension with explanatory power to the ongoing studies. The objectives are described in more detail below:

I. Determining the spatio-temporal variation in coral recruitment along the south coast of St. John with a view to testing for an effect of seawater temperature and indirectly the role of larval supply (as assessed by recruitment to tiles) and post-settlement success in determining the distribution of reef corals.

Rationale: Eight years of annual censuses of juvenile corals demonstrates that their distribution is unrelated to the distribution of adult corals (Edmunds 2000), and their density, growth and mortality are related to varying aspects of seawater temperature (Edmunds 2004). While these results are important, they have to be interpreted within the context of involving juvenile colonies that range in size from ≈2 mm to 40 mm diameter. This size was selected based on field logistics that necessitated finding enough “objects” (i.e., small corals) through surveys of natural surfaces to determine patterns in coral distribution. With this methodology, it is nearly impossible to see true coral recruits (which are ≤ 2mm diameter) because of the complexity of the natural surfaces. While work with juvenile corals has been valuable, by definition it excludes events that affect early life history stages, and which probably are very important (Caley et. al. 1996). In this portion of the research, settlement tiles have been deployed as natural substrata to “sample” the available coral larvae and explore spatio-temporal patterns in their variability. Specifically, the following questions have been addressed:

Q1 How does the density and taxonomic composition of coral recruits vary among locations?

Q2 What is the nature of the relationship between the density of coral recruits and seawater temperature?

II. Testing the role of thermal stress in determining the mortality patterns of juvenile corals along the south coast of St. John.

Rationale: A decade of analysis of the dynamics of juvenile corals in St. John reveals that they die at rates that are unusually high compared to other Caribbean locations (Edmunds 2000). This has demographic implications for the local populations and moreover, suggests that there are apparently hidden sources of coral mortality in this relatively pristine location. Serendipitous observation in 2003 suggested that the high mortality of new recruits might be caused by the warming of the igneous substratum (which dominates the shallow water in this location). Quantitative analyses in August 2004 confirmed that the rock is ≈ 0.6 oC warmer than the surrounding seawater in the late afternoons in August. Furthermore, the dark-adapted quantum yield (a measure of photosynthetic performance) of juvenile corals on igneous rock is slightly depressed compared to corals on limestone in the late afternoon, suggesting that the “health” of these corals might be compromised by thermal stress. In this portion of the research, juvenile corals from multiple genera on both igneous and carbonate rock were sampled for photosynthetic performance and mortality in the winter and summer in order to address the following hypotheses:

Ho: Photosynthetic performance and mortality of juvenile corals are independent of substratum type and season.

Ha: Photosynthetic performance and mortality of juvenile corals are affected by substratum type and season. Juvenile corals have reduced photosynthetic performance and higher mortality on igneous compared to carbonate substrata, and these effects are most acute during the warmest period of the year.

III) Developing K-12 outreach activities to strengthen and support the societal impacts of the project, specifically by impacting in positive ways the educational environment in the VI and in CA.

Rationale: numerous Federal and State agencies have emphasized the need to improve science education in the US through hands-on experiences for students and teachers. When the present proposal was funded (May 2006), a strong (but poorly funded) outreach component of the research was already in place. This was expanded through the inclusion of a K-12 educator on the summer field trip in 2006 and 2007, the instruction of “eco-camps” for children from Caribbean island nations, instruction by Edmunds and his graduate students at Viewpoint School in CA, the creation of a lesson plan and other educational material, and the inclusion of HS students in research opportunities through the analysis of color images in CA. Together, these activities have expanded the impact of the UPR-SG portion of the project far beyond the completion of the research agenda and the training of graduate students.

A brief history of the last 5 years of my research in St John

The research supported by the current UPR-SG award has been a stand-alone effort to address two important

Fig. 1. Map showing the location of the study sites in Great Lameshur Bay and its environs. Y and T refer to the Yawzi and Tektite sites that were established in 1987, and the numbers refer to the 6 random sites established in 1992. Six additional sites were established at ≈5 m depth in 1994 to quantify coral recruitment. Ditleff Point (to the W) and Ram Head (to the E) mark the limit of recent efforts (since 2006) to quantify coral recruitment on a larger spatial scale.

questions, which provide a new insight into the processes driving the patterns of change in coral reef community structure. Additionally, they address UPR-SG Challenge #8 (maintenance of local fish habitats), and the UPR-SG Key Thematic Areas (promoting coral reef monitoring and habitat mapping, and contributing to regional expertise). The current project is also a key component of a much larger effort to address decadal scale changes in the coral reef community structure along the south shore of St. John. With the conclusion of the summer 2008 field season, supported in part with the present award, this project now consists of 22 years of continuous ecological data in annual increments, and therefore is one of the longest running time-series analyses of Caribbean coral reefs. To fully evaluate the impact of UPR-SG investment in the present project, it is important to place it in the context of what has gone before, particularly over the last 5 years, which benefited from additional funding from the NSFLTREB program.

The present project began in 1987 with annual photographic sampling of Yawzi (9 m), Tektite (14 m), and was augmented in 1992 by 6 randomly selected sites (Fig. 1), as well as surveys of the juvenile coral population (from 1994). In the most recent 5 years of the this project (2002-present), coral cover at the random sites has remained low (<8%) and has continued to vary in an idiosyncratic manner (Edmunds 2002). The reef at Yawzi has continued to deteriorate, and at Tektite, bleaching and disease reversed nearly 17 y of increases in coral cover in the 2005 bleaching event (Miller et al. 2006, Donner et al. 2007, Lesser 2007) (Fig. 2). The changes at Yawzi and Tektite were unexpected, first, because a population model suggested that severe losses of the dominant coral, Montastraea annularis , at Yawzi would take ≈50 y (Edmunds & Elahi 2007), and yet they were already underway ≈1 y after the prediction was published. Second, gradual increases in coral cover at Tektite had suggested that this deeper site might serve as a refugium (sensu Pielou 1979) from which corals might “seed” nearby areas (Edmunds 2002); this assertion now seems to be incorrect, given the loss of coral between 2003 and 2006 (Fig. 2).

The analysis of the population dynamics of juvenile corals (< 4 cm diam) has been an importan t part of this project since 1994, and the surveys have revealed striking temporal variation in both population density (e.g., mean densities of 12 to 22 corals m-2), and growth rates (Fig. 3). The detection of both of these patterns has been insightful, as further research has shown that the density effects are associated positively with seawater temperature (Edmunds 2004), putatively because of the stimulatory effect of temperature on larval development (O’Conner et al. 2007).

Fig. 2. Time-series analyses of coral cover (mean ± SE, n ≈30 quadrats/y) spanning 20 y at (A) Tektite, and (B) Yawzi, both located within Great Lameshur Bay (Fig. 1), and dominated by the framework building coral Montastraea annularis. Up until recently, the two reef areas had followed different trajectories, even though they are separated by only ≈1 km. Beginning in 2003 however, and accelerating during 2005/2006 (when region-wide coral mortality occurred), the cover at Tektite began to decline, and may have initiated a loss similar to that which began 18 y ago at Yawzi. By August 2007, cover at Yawzi had fallen to ≈6%, and at Tektite it was ≈ 18%.

Fig. 3. Growth of juvenile corals (change in diameter) over a decade on shallow reefs in St. John. Rates are pooled among taxa, and expressed as realized rate (actual change in size regardless of sign), and potential rates (only increases in size).

Growth rates vary among years, in part because of variation in seawater temperature (Edmunds 2006).

Further analysis of the growth of juvenile corals (Fig. 3) revealed that the variation is associated with a change in growth scaling (i.e., how growth covaries with size), with growth switching from positive allometry in cool and variable years, to isometric in warmer and stable years (Fig. 4) (Edmunds 2006). Experimental work in Moorea demonstrated that temperature can cause a change in growth scaling for juvenile corals (Edmunds 2008). Thus, the empirical relationship between temperature and scaling, together with evidence that temperature has warmed significantly in this locality (Edmunds 2006), illustrates a potentially important means of biophysical coupling through which global climate change (GCC) can drive changes in coral communities. The role played in the relationship by the variability in temperature is interesting (Fig. 4), as a recent large study has also identified the importance of variation (i.e., SD) in temperature (rather than the rate of increase) in causing thermal bleaching in east Africa (McClanahan et al. 2007). For a longer time scale, a meta analysis of the growth rates of juvenile corals, which included studies dating to 1970 (and earlier) as well as data from the present study, suggests that the growth rates of this important life stage may have declined 34% over the last 32 years, perhaps as a result of GCC (Edmunds 2008). This important finding would have gone unnoticed without decadal-scale data in a hypothesis-driven framework such as can be provided by the present long-term project.

Testing the “storage effect” for Montastraea annularis – through which long-lived organisms store the effects of infrequent successful recruitment (Warner & Chesson 1985) – was an important goal of the last 5 years of effort. A size-based demographic model for M. annularis was developed, using parameter values harvested from the photoquadrats in 5 y intervals, and used to project the population under various scenarios of perturbation. The results revealed that the population of M. annularis at Yawzi Point is not viable under a storage effect scenario (Edmunds & Elahi 2007). Indeed, the population is projected to decline further, regardless of recruitment, unless the high rates of fission and mortality of adult colonies can be reversed. The prediction of local extirpation of this species within 50 y (Edmunds & Elahi 2007) may have been optimistic (Fig. 2).

Fig. 4. Relationship between the scaling exponent for growth (b) in juvenile corals and multivariate seawater temperature (derived from a principal components analysis of 6 temperature metrics). Growth scaling switches from positive allometry (b > 1) in cool and thermally variable years, to isometry (b = 1) in warm and stable years Edmunds 2006).

Given the changes in coral cover that have occurred in St. John and elsewhere in Caribbean, several researchers have asked how these changes might affect the colony sizefrequency distribution (Bak & Meesters 1998; Hughes & Tanner 2000). The question is important, as small colonies are subject to high rates of mortality, and corals are under strong selective pressure to grow out of this risky size class (Jackson 1977). As large colonies often undergo partial mortality and fission (Hughes & Jackson 1980), they can transition down the range of size classes and again be exposed to high risks of mortality. Determining whether such a trend has occurred in St. John was an objective of the last 5 years, and has been addressed for three species. Montastraea annularis provides an example of a species where a positive size-frequency distribution has become prominent (Edmunds & Elahi 2007), and it is likely that the growing abundance of small colonies has contributed to the susceptibility of mass mortality events, such as those occurring in 2005. The trend is less clear however, for two other species, with one (Porites astreoides) demonstrating a positively skewed size-frequency distribution, which has persisted for decades (Green et al.

Fig 5. Aerial image of the S coast of St. John (www.google.earth.com) showing the location of the 10 sites were settlement tiles and temperature loggers were located from August 2006 – August 2008

2008), and the other (Diploria strigosa) maintaining a normal distribution.

Analyses of the population dynamics of P. astreoides and D. strigosa began in 2004 to test the hypothesis that brooding corals are increasing in abundance relative to broadcasting corals on Caribbean reefs. While testing this hypothesis has been time consuming, the first results reveal that: (1) these 2 species are resilient to the present assaults on corals reefs, and (2) the results for P. astreoides (a brooder) and D. strigosa (a broadcaster) do not support the hypothesis that life history strategy affects the success of corals on contemporary reefs. Clearly however, with 1 replicate for each life history, this conclusion should be considered preliminary, particularly since there is evidence that P. astreoides has increased in relative abundance throughout the Caribbean (Green et al. 2008).

Methods used

Objective I: Analysis of coral recruitment

This objective was addressed by deploying settlement plates at ten sites (n = 15 site-1) at ≈ 7 m depth between Ram Head (to the east of Cabritte Horn) and White Point (Fig. 1, 5). Some of these sites are adjacent to areas I have been monitoring since 1992. Unglazed terracotta tiles (10 x 10 cm) were used, and were seasoned in seawater >6 months prior to deployment. To obtain a continuous record of seawater temperature at each site, Hobo brand “Aquapro” data logger were secured to the substratum near the settlement tiles. The loggers were cross-calibrated with one another prior to deployment to ensure that instrument artifacts did not confound the detection of among site variation in temperature signals.

Based on preliminary trials, the tiles were bolted directly to dead rock (carbonate) substratum on a stainless steel stud epoxied into a hole drilled in the rock (Fig. 6). In this configuration, the tiles were held ≈1 cm above the substratum on a spacer to create a cryptic habitat known to favor coral recruits (Birkeland et al. 1981). The initial placement of tiles took place in August 2006, and the tiles were exchanged every six months for two years (Jan 2007, Aug 2007, Jan 2008, Aug 2008). At each of these intervals, the data loggers were retrieved, downloaded and returned to the field. Upon collecting, all tiles were carefully inspected in the lab using a dissecting microscope, and all coral recruits scored and identified to genus.

Each site consisted

(15 after August

This experiment was designed as a factorial contrast between sites (fixed factor I) and times (random factor II), with the density of coral recruits as a dependent variable in an ANOVA. To test for a relationship between temperature and recruitment, a multiple regression technique was employed using the 10 sites as statistical replicates, recruitment rate as the dependent variable, and aspects of the temperature records (mean monthly, SE, max, min, modal) as independent variables.

Objective II: Temperature and thermal stress in juvenile corals

This objective was addressed by sampling juvenile corals for mortality and photophysiology on igneous and carbonate substrata in the winter (January) and summer (August). Mortality was assessed by marking corals with tags secured to the adjacent substratum, and censusing the corals for condition

Fig. 6. A representative placement of settlement tiles at one of the study sites along the south coast of St. John (4-5 m depth).

of 10

2007) settlement tiles in cluster together with one temperature logger.

Fig. 7. Our K-12 educator (C. Didden, supported with a stipend from the UPR-SG award) has lead our efforts at conservation and marine biology instruction for children from Caribbean island nations. Here, Mr Didden (in the hat) leads an ecology activity on the beach of Lameshur Bay.

(alive versus dead) at each survey interval. Additionally, photophysiological performance was evaluated using PAM fluorometry as measured with a Diving-PAM. This technique allowed for the nondestructive, in situ assessment (i.e., the corals did not have to be removed from the substratum or collected) of photosynthetic efficiency (as light- and dark- adapted quantum yield), and the relationship between Electron Transfer Rate (ETR) in PSII (a functional equivalent of Carbon fixed) and irradiance.

The analysis of the effects of substratum and season on dark-adapted quantum yield was designed as a factorial experiment to contrast the effect of substratum type (fixed factor I) and season (fixed factor II) using ANOVA. The effect of season and substratum on mortality was assessed with contingency table analyses.

Objective III: Developing K-12 outreach activities to strengthen and support the societal impacts of the project, specifically by impacting in positive ways the educational environment in the VI and in CA.

Four approaches have been used to achieve this goal. First, a K-12 educator (Craig Didden) has been included in the summer field trips of 2005-2007. The chief objective of this participation has been to work with children participating in “eco-camps” (see http://www.islands.org/viers/2008EcoCamps.htm) in order to provide instruction in ecology, reef biology, and conservation biology (Fig. 7). Such instruction has typically taken place in the coastal lab or on the beach, and has involved topics as diverse as plankton ecology, coral identification, and ecological sampling techniques. Second, the K-12 educator has been involved in an independent research project to address spatial variation in coral recruitment around the coast of St. John. To date, this project has generated a poster presentation at a regional conference in the western US (see below). Third, we have worked with the K-12 educator and his school to create a meaningful research opportunity for high school students. This has taken the form of analysis of color images from the project in St. John with the goal of quantifying the changes in invertebrate abundance over the last 22 years. This project has been closely linked with the REU project for 2007, and a joint publication is anticipated with an early 2009 submission. Finally, two educational deliverables have been created, one in the form of a high school lesson plan, the other in the form of a waterproof “flip book” for use while snorkeling to identify common invertebrates in St. John.

Fig. 8. Representative data for Aug 2006January 2007 that shows a decline in coral recruits from the east (e.g., Ram Head (Fig. 5) to the west (Dittlef Point). This gradient has been repeated in the fouth other sampling intervals.

Results and findings (please see the end of the document for abstracts of the results)

Objective I: Analysis of coral recruitment

The analyses of coral recruitment along the south coast of St. John have spanned 2 years in four sampling periods with samples collected from 10 sites. The four sampling periods provided replicate assessments from two time periods in each year (August and January), with the temperature records providing an assessment of seasonal variation, and the recruitment providing two time points in one year (the bracketing of true seasonal intervals – such as sampling in the middle of the summer and winter – prevents the analyses from truly characterizing seasonal variation). The analyses of the settlement tiles revealed coral recruits at mean densities of ca. 0.5-3 recruits tile-1, with a striking and repeatable trend of declining densities from the east to the west

Fig. 9. Sample recording of seawater temperature of one of the study site over three days in January 2008. Importantly, the data reveal a strong diurnal variation of ≈0.5oC.

(Fig. 7). At all sites, the dominant taxa coral that recruit to the tiles belong to the families Poritidae, Faviidae, Agariciidae, and Siderastreidae; notably, individuals from the family Acropora were virtually absent, and only one individual was found on one plate during one sampling period

The analysis of the seawater temperature at the 10 sites revealed that the mean temperature was indistinguishable among the 10 sites, yet all the sites displayed a strong diurnal warming trend (Fig. 9) that varied in magnitude among sites. This variation has proved to be valuable in addressing likely causes of the among-site variation in coral recruitment, in large part because of the statistically significant inverse relationship between recruitment and the daily variation in seawater temperature (Fig. 10). Currently, we are evaluating the full data set (with the final data collected in August 2008) for a similar relationship, and considering the spectrum of processes that could generate such a relationship.

Objective II: Temperature and thermal stress in juvenile corals

Analyses of juvenile corals on igneous and carbonate substrata along the south coast of St. John have revealed some effects of the substratum type on coral success, but the effects are unlikely to be sufficiently strong to lead to strong selective value of growing on igneous or carbonate rock. The analyses of the temperature of the rock types reveals strong signals of diurnal warming (up to 0.5 oC d-1), with the igneous rock warmer by 0.1 – 0.2 oC at about noon in comparison to carbonate rock at the same depth. Additionally, the igneous rock warms more rapidly than the carbonate rock as the sun rises. The growth response of juvenile corals to the type of rock they settle on appears to depends on the time year, with a significant difference between rock types between August and January (the warmest time of year) but not between January and August; juvenile corals grow up to 38% faster on igneous versus carbonate rock. Although growth normally has strong selective value in tropical reef corals, these differences do not translate to differences in mortality between rock types. Over each sampling period, the mortality rates of juvenile corals ranged from 5-30 % 6 mo-1 on both igneous and carbonate rocks.

The analyses of photophysiology were conducted to gain insight into the likely causes of the differences of growth rate of juvenile coral on igneous and carbonate rock. These analyses were completed only for juvenile Porites astreoides (one of the most common taxa of juvenile corals encountered in St. John), and they revealed that the maximum dark adapted quantum yield of PSII was similar between corals on each rock surface, although photosynthesis appeared to be impaired at high irradiances to a greater extent in corals located on igneous rock compared to carbonate rock. This impairment was conspicuous in the plots of Electron Transfer Rate (ETR, a measure of photosynthesis that is closely related to the capacity to fix carbon) versus irradiance, notably in a strong depression (downward deflection) of ETR at high irradiances.

The Symbiodinium taxa in juvenile corals were identified for 3 colonies of Porites astreoides on each of igneous and carbonate rock surfaces. Together, these analyses identified 63 DNA sequences corresponding to a diversity Symbiodinium ITS2 types belonging to clade A. These sequences corresponded to 9 distinct Symbiodinium signatures, of which A4 and A4a were the most common; statistical analyses revealed that the majority of genetic variation (96.5%) was associated among colony variation, regardless of substratum type, and only 3.5% was associated with the rock type they were growing on. Thus, these data do not support the hypothesis that the substratum effects on growth and photophsyiology (described above) were caused by differences in Symbiodinium alone; instead, it is more likely that the differences are associated with cnidarian host effects. An unexpected outcome of this analysis is the demonstration of the importance of Clade A Symbiodinium in juvenile colonies of this species in St. John. In light of the rising abundance of this taxon throughout the Caribbean (Green et al. 2008), and recent evidence that Clade A algae are at a “parasitic end” of a parasite-mutualist symbiosis gradient that describes the relationship between corals and their Symbiodinium (Stat et al. 2008), it is tempting to speculate that the recent success of P. astreoides is related to their unusual (parasitic) Symbiodinium

12 outreach activities

The principle deliverables from these activities are described above, but importantly, we have established a framework to support further activities of a similar nature over the coming years. Thus, we have achieved long lasting societal impacts by strengthening the representation of marine science topics in the K-12 educational agendas of both the Virgin Islands and California.

Objectives accomplished or not and why

Objective I: Analysis of coral recruitment

Fig. 10. Scatterplot displaying the relationship between density of coral spat per tile by site, and the mean daily variation in seawater temperature for the Aug ’06-Jan ’07 period. Strikingly, the two are inversely correlated.

We have fully met our objectives in this portion of the research, having deployed settlement tiles and temperature loggers at 10 sites along the south coast of St. John since August 2006. The project involved sampling the tiles every ≈6 months with exchanges and temperature loggers taking place in January 2007, August 2007, January 2008, and August 2008. At each sampling interval, 10-15 tiles were replaced and screened for coral recruits on all surfaces; the recruits were identified to genus and counted.

The objectives of these analyses were to test for variation in taxonomic composition of coral recruits along the south shore of St. John, and then test for a statistical association between the density of coral recruits and aspects of seawater temperature. The outcomes have revealed that: (1) the recruiting corals were mostly in the genera Poritidea, Faviidae, Agaricidae, and Siderastreidae, and this taxonomic assemblage was similar at all sites, (2) the overall density of coral recruits varied from ≈0.7 ± 0.2 recruits tile-1 to 1.5 ± 0.4 recruits tile-1, and there was a strong and repeatable trend for recruitment to decline from the east to the west; as many as 3.6 ± 1.8 recruits tile-1 were found at eastern sites, but as few as 0 recruits tile-1 at western sites; and (3) coral recruitment is related significantly and negatively to the daily range in seawater temperature along the coast of St. John; highest recruitment occurred where the variation in seawater temperature was the lowest (i.e., to the east).

Objective II: Temperature and thermal stress in juvenile corals

We have met our project goal by testing through mensurative analyses the effects of temperature on the biology of juvenile corals. Our analyses have extended over the duration of the UPR-SG award, and have quantified the thermal regime of the rock substratum (carbonate versus igneous), as well as the growth, mortality, and photophysiology of juvenile corals on each surface. Significantly, we have been able to step significantly beyond the original scope of the award by developing a fledgling collaboration with Dr. Ruth Gates (University of Hawaii, http://www.hawaii.edu/HIMB/Faculty/gates.html) to analyze the genetic identity of the algal symbionts in juvenile corals on either rock type. To date, seed support from CSUN ($6k) has been used to analyze the genetic identity of the algae in 6 Porites astreoides colonies, and the results have identified a relatively high diversity of algal symbionts; currently it seems unlikely that specific algae are associated with corals on specific surfaces.

Objective III: Developing K-12 outreach activities

While we have met many of the objectives of this portion of the research, the progress has been slower than anticipated and has allowed us to identify significant hurdles that we must now solve in order to realize the full potential of the outreach component of our activities. The principle hurdles have come from: (a) a better realization of the financial costs of outreach activities (teacher stipends and graduate RA), and the necessity to secure more significant funds to support the involvement of a broader cross section of the lab and K-12 community, (b) the challenges for “outsiders” to “breaking in” to the K-12 community in a West Indian island community, and (c) the difficulties of creating meaningful

research opportunities in the area of Caribbean reef ecology for high school students in California.

Discussion of project impacts and products

(a) Impacts. This project has had significant impacts in four areas:

Time-series analyses of coral community structure. The objectives of the present award were clearly focused on the analysis of coral recruitment and the success of juvenile corals, but the project achieves greater significance by its placement against the backdrop of 22 years on continuous coral reef monitoring, and its contribution to this effort. The time-series analyses have been ongoing in this location since 1987, and this grander project has been conceived to quantify patterns of change and test hypotheses that have the potential to identify processes with influential roles in causing these changes. In this context, the present work contributes significantly to a more profound understanding of the events taking place on the reefs in the northeastern Caribbean.

Understanding of the dynamics of coral recruitment in St. John. To date, my research in St. john has focused on the community dynamics of adult corals and the population biology of juvenile corals (colonies ≤ 40 mm diameter). These efforts have been valuable in understanding both the long-term changes on the reefs in this location, plus some of the mechanisms that have been driving the change. However, the work has been unable to address the role of larval supply and recruitment on coral community structure. The present project has contributed a highly valuable new insight into the ecology of these reefs, notably by addressing spatio-temporal variation in coral recruitment and the effects of substratum choice on coral success.

Graduate/Undergraduate training. The effective training of graduate students in research is the foundation of the scientific prominence of the United States in the globally-oriented workforce of the 21st Century. Moreover, the introduction of talented young minds to the opportunities for biological research in the northeastern Caribbean, notably St. John, is critical to ensure the creation of scientific workforce capable and willing to meet the environmental, scientific, and education needs of the region. The present project has had major impacts in both of these areas through the training of graduate students and undergraduate students (both from the mainland and Puerto Rico).

Community outreach activities. Over the last two years we have built a strong program that engages K-12 educators and children in the scientific agenda of this award.

(b) Products. The principle scientific products of this project include (refer to executive summary for further details):

• 3 peer reviewed publications (1 published, 2 in prep)

• 1 book chapter

• 5 talks at national/international conferences

• 4 posters at national/international conferences

• 1 MS thesis that is directly related to this project (plus, 4 others that have been supported indirectly)

• outreach deliverables: 1 lesson plan and 1 field guide

Recommendations

In light of the results of this project, and their implications against a 22-y backdrop of time series analyses in this location, the following recommendations appear appropriate:

1. Further analyses of patterns of coral recruitment are required to distinctively identify meaningful patterns from random noise. While the results of this study are valuable, it is clear that there is substantial variation among years that currently we have little ability to understand. In order to better understand the processes driving the dynamics of shallow reefs in the US Virgin Islands, it will be critical to understand the causes and consequences of annual variation in coral recruitment.

2. The detection of a strong westerly gradient in coal recruitment along the south shore of St. John raises important issues regarding the management of coral reef resources in the VI National Park. The

significance lies in two implications that are not mutually exclusive. First, the gradients raise the possibility that the reefs of south coast of St. John are more strongly supported by an eastern “source population” of coral recruits that currently is recognized. While it is unknown where this might be, or how far away, the possibility that recruitment to the reefs of St. John is linked closely to the health and fecundity of corals in, for example, the British Virgin Islands (that are to the E/NE) has important implications for local resource management in St. John. Second, the likelihood that areas along the south coast of St. John are sites of unusually strong coral recruitment (notably eastern sites in the lee of southerly projecting headlands) has important implications for the possibility of targeting small areas of reef for stronger protection.

3. The present analyses of the effects of substratum type (igneous versus carbonate) on reef corals, while identifying some effects of substratum on coral success, has not provided the powerful insights to the causes of successful recruitment that were anticipated. Clearly however, the death of small corals in St. John continues to be an important factor shaping the coral community structure of shallow reefs. Further studies of the factors determining the success of coral recruits are likely to be highly insightful.

4. The impacts of the outreach activities of the present project on K -12 education in both the Virgin Islands and California have been substantial and highly positive. However, our experience over the last few years has revealed that: (a) progress is exceedingly slow because of the need to build relationships with the local communities (teachers, parents, and children), and (b) the full capacity to influence K-12 education by research projects such as the one completed here will only be achieved through greater financial support, notably to fund teacher and graduate student involvement through stipend and assistantship support.

Bibliography

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Donner SD, Knutson TR, Oppenheimer M (2007) Model-based assessment of the role of human induced climate change in the 2005 Caribbean coral bleaching event. Proc Nat Acad Sci USA 104: 5483-5488

Edmunds PJ (2000) Patterns in the distribution of juvenile corals and coral reef community structure in St. John, US Virgin Islands. Mar Ecol Prog Ser 202:113-124.

Edmunds PJ (2002) Long-term dynamics of coral reefs in St. John US Virgin Islands. Coral Reefs 21: 357-367.

Edmunds PJ (2004) Juvenile coral population dynamics track rising seawater temperature on a Caribbean reef. Marine Ecology Progress Series 269: 111-119.

Edmunds PJ (2006) Temperature-mediated transitions between isometry and allometry in a colonial modular invertebrate. Proceedings of the Royal Society of London B 273: 2275-2281

Edmunds PJ (2008) Seawater temperature mediates growth scaling in juvenile scleractinian corals. Marine Biology 154: 153-162

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Abstracts of work from this award

1. International Coral Reef Society (2008) [poster]

INVESTIGATING SPATIAL VARIATION IN CORAL RECRUITMENT WITH RESPECT TO TEMPERATURE ALONG THE SOUTHERN COAST OF ST. JOHN, US VIRGIN ISLANDS

Green, D.H. & P.J. Edmunds

Studying the effects of physical environmental factors on scleractinian corals has been popularized by the increased frequency of thermal bleaching, however few studies have documented the effect of temperature on coral recruitment. The goals of this study were to test for kilometer-scale variation in seawater temperature and coral recruitment on the southern coast of St. John, US Virgin Islands, and to explore the extent to which temperature might be influencing coral recruitment. To measure temperature and recruitment, a logging thermistor and settlement tiles were deployed at 5-6 m depth at 10 sites in August 2006. Thermistors and settlement tiles were replaced and analyzed every six months in order to capture seasonal variation in biological and physical events. The two sampling periods occurring between August 2006 and July 2007 revealed strong east-to-west relationships in temperature and densities of coral recruits, which is likely a result of the prevailing westward water current. In both sampling periods, the abundance of coral recruits differed significantly among sites, with mean densities declining from ≈ 1.7 recruits tile-1 in the east, to ≈ 0.4 recruits tile-1 in the west. Seawater temperature also varied significantly among sites over both sampling periods, and this effect was reflected in greater daily variation in temperature at western sites compared to eastern sites. Together, through a significant negative correlation between daily variation in temperature and coral recruitment, these results suggest that small-scale variations in temperature are associated with the rate of coral recruitment in St. John. If this relationship applies to larger spatial scales, then it might provide insights into the causes of variation in coral recruitment throughout the Caribbean.

2. Association of the Island Marine Labs of the Caribbean (2007) [talk]

CORAL RECRUITMENT ALONG THE SOUTHERN COAST OF ST. JOHN, US VIRGIN ISLANDS: THE INFLUENCE OF TEMPERATURE IN MEDIATING SPATIO -TEMPORAL VARIATION

Green, D.H. & P.J. Edmunds

Studying the effects of temperature on scleractinian corals has been popularized by the increase in thermal bleaching events, but few studies have documented the effects of temperature on scleractinian larval settlement and postsettlement success. The goal of this study is to test for the effects of kilometer-scale variation in temperature on the recruitment of scleractinian corals. Experiments were initiated to quantify seawater temperature as well as the recruitment and post-settlement success of corals along the south coast of St. John, US Virgin Islands. To measure variation in temperature and recruitment, logging thermistors and settlement tiles were deployed at 5-6 m depth at 10 sites, and juvenile corals were tagged on limestone and granite substrata, both of which are common subtidally in St. John, to determine growth and mortality. Preliminary experiments in August 2006 revealed that granite was up to 0.5 oC warmer than limestone during the afternoon, and therefore it was hypothesized that juvenile corals would suffer greater thermal stress on the former compared to the latter. Thermistors, settlement tiles, and tags were deployed in August 2006, and the first census occurred in January 2007. Additional surveys will occur at 6-month intervals in order to capture seasonal effects in the factors mediating coral recruitment and post-settlement success. The preliminary results from the first surveys reveal (1) small-scale variations in seawater temperature that appear be associated with rates of coral recruitment, and (2) patterns of post-settlement success that appear to be mediated by substratum type (i.e., granite versus limestone).

3. Benthic Ecology Meetings (2007) [poster]

THE EFFECTS OF TEMPERATURE IN MEDIATING SPATIO-TEMPORAL VARIATION IN CORAL RECRUITMENT ALONG THE SOUTH COAST OF ST. JOHN, US VIRGIN ISLANDS

Green,

D.H. & P.J. Edmunds

4. CSUN Student Research and Creative Works Symposium 2007 [talk]

Green, D.H. & P.J. Edmunds

The goals of this study were first, to test for kilometer-scale variation in seawater temperature and coral recruitment on the southern coast of St. John, and second, to explore the extent to which temperature might account for variation coral recruitment. Two sampling periods occurred between August 2006 and July 2007, and both revealed strong east-to-west relationships in temperature and densities of coral recruit, which is likely a result of the net westward motion of the prevailing water currents. The abundance of coral recruits differed significantly among sites situated along this gradient, with mean densities declining from ≈1.7 recruits tile-1 in the east, to ≈0.4 recruits tile-1 in the west, during both sampling periods. Seawater temperature also varied significantly among sites over both sampling periods. These results suggest that small-scale variations in seawater temperature may be associated with the rate of coral recruitment among locations on the southern coast of St. John.

5. Western Society of Naturalists 2007 [talk]

EXPLORING VARIATION IN CORAL RECRUITMENT THROUGH TEMPERATURE ALONG THE SOUTHERN COAST OF ST. JOHN, US VIRGIN ISLANDS

Green, D.H. & P.J. Edmunds

Studying the effects of environmental factors, such as temperature, on scleractinian corals has been popularized by the increased frequency of bleaching, however few studies have documented these effects on scleractinian recruitment. The goals of this study were to test for kilometer-scale variation in seawater temperature and coral recruitment on the southern coast of St. John, US Virgin Islands, and to explore to the extent to which temperature might affect coral recruitment. To measure temperature and recruitment, a logging thermistor and settlement tiles were deployed at 5-6 m depth at 10 sites in August 2006. The thermistors and settlement tiles were replaced and analyzed every six months in order to capture seasonal variation in biological and physical events. The two sampling periods occurring between August 2006 and July 2007 revealed a strong east-to-west relationship in temperature and recruit densities, which probably is a result of the prevailing water currents. The abundance of coral recruits differed significantly among sites, with mean densities declining from ≈ 1.7 recruits tile-1 in the east, to ≈ 0.4 recruits tile-1 in the west, during both sampling periods. Seawater temperature also varied significantly among

sites over both sampling periods, and this effect was attributed to greater daily variation in temperature at western sites compared to eastern sites. Together, these results suggest that small-scale variations in seawater temperature may be associated with the rate of coral recruitment among locations on the southern coast of St. John.

6. Western Society of Naturalists 2007 [poster]

VARIATION IN THE POPULATION DYNAMICS OF JUVENILE CARIBBEAN CORALS OVER 10 KM OF COAST

Craig Didden and Peter Edmunds

Testing for scale dependence of ecological patterns is an important objective on coral reefs where community structure varies over multiple spatio-temporal scales. Because of the importance of coral recruitment, the scale dependence of this process has attracted considerable attention, and here we ask to what extent does spatial variation affect our conclusions regarding coral community dynamics developed from a few kilometers of coast in St. John (USVI)? Over the last decade, our research has revealed an association between coral recruitment and temperature, and evidence that early life stages of corals now grow more slowly than they did 30 years ago. To expand the scale of this work, in 2006, juvenile corals were tagged at 8 sites to measure growth and mortality, and in 2007, the population density was assessed at 10 sites spanning ≈10 km of coast. The results reveal that growth rates were low (≤6.2 mm/y) relative to historic figures, and that among sites, mean growth rates ranged from 2.1-6.2 mm/y, mortality ranged 7-36%/y, and densities ranged 0.8-4.6 corals/0.25 m2. Although there were significant differences among sites in growth and density, overall the dynamics of juvenile corals were relatively similar on a scale of 1 km and a scale of 10 km. Significantly, the slow growth rates at all sites underscores the likelihood that juvenile corals are growing more slowly than they did in the 1970’s.

7. Western Society of Naturalists 2006 [talk]

A DECADAL SHIFT IN THE RELATIVE ABUNDANCE OF CORALS ON CARIBBEAN REEFS THAT FAVORS A WEEDY SPECIES

Green, D.H. & P.J. Edmunds

Against a backdrop of a 30 y decline in coral cover throughout the Caribbean, there is evidence that some "weedy" corals - like Porites astreoides - may have increased in relative abundance. In this study, P. astreoides population at six sites throughout the region were quantified in 2003-04 to determine the contribution of this species to presentday coral cover and, through a comparison with historic data, to test for decadal-scale changes in its relative abundance. The analysis of coral community structure shows that most sites were characterized by <15% coral cover, of which 16-72% was P. astreoides that was present at low densities (< 3 colonies 0.25 m2) with 85% of the colonies < 100 cm2 in size and probably sexually immature. Historical data collected throughout the Caribbean in the 1970's, 1980's, and the early 1990's reveal the now well-known region-wide decline in absolute coral cover, but also suggest that the relative percent cover of P. astreoides has increased from < 20% in the 1970's to ~50% in 2003-04. Together, these results provide some of the first quantitative evidence that Caribbean reefs are undoing striking changes in coral species assemblages as the overall coral cover declines.

Thesis abstracts

1. Mairead Maheigan (graduated June 2007)

SPATIAL SCALE OF MORPHOLOGICAL VARIATION OF THE CORALS POCILLOPORA VERRUCOSA AND PORITES PORITES

In recent years it has become evident that biological processes must be analyzed at multiple spatial scales to investigate how results may change across scales, which is often non-linear. Phenotypic plasticity in scleractinian corals has been studied widely, however the degree to which it exhibits spatial scale dependence has not been explored. My primary objective was to determine if coral morphology varies among traits and across spatial scales. To test for spatial scales of morphological variation, skeletal traits of two corals Pocillopora verrucosa , in French

Polynesia, and Porites porites in the Virgin Islands were quantified across spatial scales. The experimental design was constructed to exploit a nested ANOVA, in which all the factors were random and nested by spatial scale. To estimate which skeletal traits of P. verrucosa contributed most to overall variation in coral shape, principal components analysis (PCA) was used to define the multivariate morphology and to collapse the data into fewer variables that explained the majority of the variance. Nine skeletal traits were quantified in 160 colonies of P. verrucosa across two shores. To test for spatial scale dependence, principal components (PC) then were tested across spatial scales. Our findings show that 2 PC’s, which were associated with 2 different spatial scales, explain 45% of the variation in morphology. Firstly, corallum dimensions (highest correlation coefficients in PC 1), exhibited significant variation at a spatial scale of 100’s of meters. Second, verrucae and corallite morphology (highest correlation coefficients in PC 2), varied significantly at a smaller scale of 10’s of meters (the greatest explained variance (76%-84%) of both PC’s was associated with the smallest spatial scale - individual colonies). To test for spatial scale associations of morphological variation in P. porites, colonies were sampled along ~10 km of the southern coast of St. John. Corallum traits were quantified in 140 colonies, and traits were found to differ between sites. In both species of coral some skeletal traits were highly conserved and did not exhibit much variation, and other traits were highly variable. These studies provide evidence that the magnitude of morphological variation is not consistent among skeletal traits and spatial scales for P. verrucosa or P. porites. Following the quantification of morphological traits, a skeletal trait of P. verrucosa, small projections called verrucae, was subjected to controlled flow speeds in a flume to explore the functional significance of this trait. Shear velocities around and above verrucae were experimentally estimated, at two flow speeds, to test if verrucae influence rates of mass transfer at the coral surface. Our results suggest that verrucae do not influence shear velocities, and thus are unlikely to affect mass transfer on the scale of our experiment. These findings were consistent with previous studies that indicate that small skeletal features may be less important than larger skeletal attributes in determining shear velocities above corals.

THE EFFECTS OF TEMPERATURE FLUCTUATIONS ON CORAL PHYSIOLOGY

An organism’s response to the physical environment is determined by its immediate abiotic surroundings, which can have significant spatio-temporal variability. Multi-year examination of seawater temperatures on coral reef communities in the lagoon of Moorea, French Polynesia, and the fringing reefs of Nanwan Bay, Taiwan, revealed a strong pattern of diurnal thermal fluctuations of up to 4.5 ºC and 9 ºC, respectively. Repeated experiments were carried out in Moorea in April and May of 2006 and 2007 in order to determine the effects of large diurnal fluctuations in temperature on the physiology of the scleractinian coral host and its symbiotic dinoflagellates in the genus Symbiodinium . In 2006, exposure of the common reef corals Pocillopora meandrina and Porites rus to extreme fluctuations in temperature, ~6 ºC every 12 h, resulted in significant declines in maximal dark-adapted quantum yield (FV/FM) and Symbiodinium density when compared to a steady ambient treatment. In 2007, exposure of Pocillopora meandrina and Porites rus to diurnal fluctuations in temperature (26 – 30 ºC), compared to three steady temperature treatments, resulted in a decrease in the Symbiodinium density of corals in response to treatment. Importantly, symbiont density showed significantly greater reductions in the fluctuating treatment than in corals exposed to the steady treatments. However, a measure of holobiont performance - skeletal growth - remained stable in all treatments. The effects of thermal variability also were studied on the reef corals in Taiwan in 2007. Here, both adults and larvae of the common brooding corals Pocillopora damicornis and Seriatopora hystrix were used to examine ontogenetic variability in the response of reef corals to fluctuating temperatures. In addition, a time series examination of the physiology of freshly-collected P. damicornis larvae from sequential release days was conducted to test the hypothesis that coral larvae differ physiologically with time spent in the maternal polyp. The results of this time series study revealed that three parameters - FV/FM, Symbiodinium density, and larval size - differed with day of release. The largest differences were seen in the variation in Symbiodinium density and larval size. Following exposure to steady temperatures, FV/FM of coral larvae were significantly reduced (~53% on average) compared to the FV/FM of adults. However, in the fluctuating treatment, FV/FM was only reduced ~36% on average when compared to adult values. Together these results show that large fluctuations in the thermal environment can have detrimental effects on coral physiology depending on the duration of extreme fluctuations and the amplitude of the temperature signals. Nonetheless, corals respond in an extremely flexible manner revealing that they are able to acclimatize to thermally heterogeneous environments.

Hollie Putnam (graduated June 2008)

1. Research opportunity for high school students in California

See http://www.viewpoint.org/Default.asp?bhcp=1

Research Opportunity for Outstanding High School Students in Caribbean Coral Reef Ecology

Project Overview

Coral reefs have long been recognized as a unique biome harboring a higher diversity of animal and plants than is found in virtually any other ecosystem. They also play critical roles in supporting coastal fisheries, shoreline protection, “bio-prospecting” (the search for medically important compounds), and a burgeoning tourism industry worth billions of dollars annually. Unfortunately however, the wide range of goods and services provided by reefs is seriously threatened by the death of corals, with the recent losses leading some scientists to predict that corals reefs may become extinct within the current century. The major research goals of coral reef scientists now are to understand the causes of reef decline, to predict how reefs will change in the coming century, and make recommendations to improve the management of the reefs remaining.

One critical tool in the fight to understand coral reef death is the analysis of coral community structure over time, which frequently is described as “coral reef monitoring”. Because the changes occurring are acting over many years, and the coral architects of these ecosystems live for decades or centuries, it is essential that monitoring extend over decadal scales and resolve the fate of individual coral colonies. Since the most recent period of coral loss began in the early 1980’s, monitoring has proliferated throughout the world, and the basic patterns of change in coral cover now are well understood. Far less is known however, about the processes driving these changes.

The United States has coral reef resources in Hawaii, the south Pacific, Florida, and the Virgin Islands, and monitoring projects are underway in each location. One of the longest-running of these has been taking place in the US Virgin Islands where scientists from the US National Park Service and California State University, Northridge (CSUN) have been measuring the change in coral cover on the reefs of St. John since 1987. This location provide a unique opportunity to study changes on coral reefs because much of the island is protected by a national park, and much of the adjacent land is free of urban development. Thus, changes on these reefs are likely to reflect the natural history of the Caribbean as a whole, rather than the effects of local pollution. Despite the absence of local disturbances, more than half of the coral has died in St. John over the last 20 years, and the future for some of the most important reef-building corals is grim; in as little as 50 years at least one important coral species may become locally extinct.

Research by scientists at CSUN has generated a 21-year history of the reefs in St. John through a photographic record of permanently marked study plots. Together, these plots provide more than 8,000 images that can be used to answer critical questions regarding shifts in abundance of corals, invertebrates, and algae. This unique archive provides opportunities to explore changes in abundance of a diversity of organisms, and here we seek highly motivated high school students to work on such projects under the guidance of university faculty (Dr. Peter Edmunds) and a science teacher at Viewpoint High School (Mr. Craig Didden).

Chief Scientist

Dr. Edmunds has served as the chief scientist on this project for 21 years, and currently he is a Professor at CSUN where he has worked since 1992. His work in St. John began in 1987 with an analysis of the effects of bleaching,

but has been sustained for more than two decades with annual expeditions staffed with graduate students, undergraduates, teachers, and colleagues. Since inception, this project has generated nearly 20 peer-reviewed science publications, and currently is funded through the National Science Foundation and the University of Puerto Rico, Sea Grant Program. The ongoing funding has supported a strong component of broader outreach activities, and through this mechanism, two teachers from Viewpoint School – Mr. Craig Didden and Mr. Mark McLaughlin –have spent 1-2 weeks each year working with the research team in St. John. The objectives of this involvement has been to extend the societal impact of Federally funded research, and contribute at an early academic stage to the scientific training of the American workforce.

Teacher Involvement and Relationship with Viewpoint High School

Teachers from Viewpoint School have been working with Dr. Edmunds since 2004. They have engaged in classroom and field research in the Virgin Islands, and used this unique opportunity to integrate aspects of the science curriculum at Viewpoint School with the research activities of a local university. Collaborative efforts between university faculty and teachers have been used to achieve three goals: (1) to develop lesson plans in coral reef ecology for use in California schools, (2) to provide hands-on research opportunities to enhance the capacity of California teachers as science instructors, and (3) to work together with university faculty and graduate students to provide ecology instruction to K-12 children in the Virgin Islands.

Our goal here is to provide meaningful training in marine ecology research to high school students. The nature of this involvement will vary among student participants, notably depending on their commitments to science careers and ability to participate in research on a weekly basis. Potential research projects include analyses of the abundance of key invertebrates species over 20 years, determination of the population structure of species over time, and the comparison of results in St. John with those obtained in other locations. Students selected for this opportunity would work closely with Mr. Didden at Viewpoint School to analyze images dating to 1987, complete monthly visits to CSUN to work with Dr. Edmunds, and attend customized workshops and seminars to enhance the understanding of the research question. A capstone experience will be created through participation in a regional science conference where the high school students will present their research findings.

The Research Opportunity

We are seeking students with a strong interest in biological sciences to conduct research using 21 years of data from our monitoring project in St. John, USVI. An ideal student would have a history of strong performance in science, a passion for natural history, and a strong motivation for a science career. Moreover, they must be able to spend 2-3 hours/week on this research, and be able to visit CSUN for mentoring and training in the research lab of Dr. Edmunds.

Contacts

If you are interested in the opportunities for research described above, please contact Mr Craig Didden at Viewpoint School (cdidden@viewpoint.org), or Dr. Peter Edmunds at CSUN (peter.edmunds@csun.edu).