ECOSYSTEM OF MYSTERY FIELD FINAL EXAM INFO Introduction: You and your partners are owners/operators of a limnological consulting company that offers physical, chemical and biological testing services and lake management planning expertise to clients seeking information and advice for formulating and implementing resource management plans. You have been approached by the Mystery Lake Association (MLA) to study and evaluate the condition of Mystery Lake and make some specific recommendations regarding the MLAʼs desire to improve lake clarity and evaluate the status of the popular fishery there (See attached letter). The keys to this assignment are: (1) Effective planning of your sampling process for you to be able to adequately describe the trophic state of Mystery Lake; (2) The ability to properly and efficiently operate field sampling equipment and conduct laboratory analysis of samples; (3) The ability to effectively summarize and appropriately interpret the data that your study generates to diagnose the condition of the lake; (4) The ability to use that data and your diagnosis to make appropriate management recommendations. Perhaps the most difficult of those things is #3. For example, you should be able to do more than simply graph an oxygen profile, you should also be able to interpret/describe how that profile gives you insight into the lakeʼs productivity by looking a variation in oxygen saturation from morning to afternoon, from season to season, and from top to bottom. The following sections describe the process and product of this assignment. This project is worth 30% of your semester grade.
Background Planning: do this in advance of your scheduled field work!!!! Talk to me if you need clarification of any of this!!! Before going out into the field you will be given this packet of information. The packet contains: • This cover letter • A letter from Allan Ingram, the Executive Director of the Mystery Lake Association • Background information on the lake (including maps and a variety of historical data) You should get together with your partner(s) to discuss what information you think you need to succeed with this assignment. What data will you collect in the field? Where? Why? What things will you need to do in the laboratory? What do you need to bring back from the field in order to complete that laboratory analysis? Is there any “library” or other background research that you can (should) do in order to get a complete picture of the lake and its surrounding environment? You should be sure to: • locate on the planning map the sites where you are going to sample and the depths at which you want to sample, • decide on what you are going to sample at each site. Are you bringing any material back to the lab or just collecting field observations? • know why you are taking a certain measurement or sample (you will need to know this for your writeup). • donʼt forget to make qualitative observations about the condition of and landuse in the watershed, as well as making observations about the composition and extent of the littoral zone of the lake. No discussion of your results will be complete (i.e., deserving of an “A”) without considering the following: Think about all of the elements of limnology that we have studied thus far this year: a) the relationship of abiotic variables to lake productivity, b) the relationship of the watershed to the lake, c) the interrelationships of organisms within the lake d) the changes that occur on a daily basis, a seasonal basis, and from place to place in the lake. The things that I am “testing” you on here is, therefore: How can you maximize your understanding of that preceding group of things with data that you can collect or research? What sorts of variables do you need to observe? You can demonstrate an added level of sophistication by your ability to make inferences about unmeasured variables based on Page 1 of 2
your understanding of the empirical relationship between particular factors (e.g., % agriculture in the watershed, secchi transparency, and chlorophyll a concentration). The bottom line is this: you are being asked to make a diagnosis of a lakeʼs trophic state. You may need to do some internet/library research on that topic to determine what sort of “metrics” are often used to quantify what will always be (to some extent) a subjective decision. In the end, you should be able to: (a) describe precisely what a parameter is and how it is measured, (b) interpret the significance of any given measurement/observation with regard to productivity, and (c) place that measurement and your interpretation of it in the appropriate seasonal context (i.e., we are taking a “snapshot” of the lake in NOVEMBER...how might the things you are measuring (and thus your diagnosis) be different if you were making these same observations at the peak of summer?
Analysis: Your group is responsible for analysis of all data/samples that you have collected. That includes collating all field data from “scratch” sheets into an Excel spreadsheet for distribution to all group members. If possible you should conduct analysis of water samples for common ions before Thanksgiving, but that may not be possible in all cases. Given that, you are also responsible for preparing/preserving samples for analysis after Thanksgiving Break. • Your group will be responsible for conducting: a plankton enumeration chemical analysis for common ions (pH, CO32=, Ca2+, Cl-) Chlorophyll a quantification I will make laboratory time available for all of these tasks after break (either during class time, or in the evenings). You are expected to be able to know how to conduct these analyses at this point & are allowed to use notes & handouts. I will only troubleshoot and/or answer questions about these procedures at a cost of points to your group.
The Write Up: The writeup will be due in lieu of a Final Exam. This writeup represents the culminating analysis of all of the skills that you have been developing over the course of the semester – field, lab, data summarization and presentation, and writing, in addition to assessing your grasp of the essential course content. I will give you more complete details regarding the format of the report when we return from break, but for your planning purposes you should know: • The format is basically that of the field reports you have written to date. • The most significant part of the report will be how you use your observations to make a plausible diagnosis of the trophic state of Mystery Lake – you should be able marshal as much data as possible to support that diagnosis and you should be able to introduce as many relevant, supporting lines of reasoning as possible. • The absolute length of the report is not the issue – the quality of your data presentation, the clarity of your argument, and the “correctness” of your understanding of limnological principles is. • You will be asked to make a management recommendation with a specific target in mind. That target might be continuing to manage the lake as a fishery, or trying to reduce weed growth, or changing the trophic state of the lake, or some other specific goal. You will be expected to rely on your data, your knowledge of limnological theory, and background research to arrive at that recommendation. As with the background preparation, you should feel free to discuss your write-up with other members of your team to help improve your insight, or check your conclusions or arguments but each individual member of the team is expected to turn in their own final “consultants” report. That report must be in your own words, not those of other group members, but it may reflect a consensus of opinion in the diagnostic/recommendation aspects of your paper. Raw data may (must?) be shared among group members, but any summarization (statistical calculations, tables, graphs, charts) must be your own work. Violations of trust with regard to these requirements to complete your own work will result in failure on this project, and may also result in disciplinary action.
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November 09, 2009 AAA Limnological Consultants, Inc. 11 Interlaken Rd. Lakeville, CT 06039 Dear Director of Field Science and Consulting: I am writing you on behalf of the Mystery Lake Association. We have observed an apparent steady decline in lake quality over the past number of years and are in the initial stages of the planning process to develop and effective management plan for Mystery Lake and its watershed. We would like to contract you to perform a diagnostic survey of Mystery Lake and prepare a report of results that would assist us in making some management decisions.
MLA MYSTERY LAKE ASSOCIATION 000 CRYPTO LANE MYSTIC, CT 01010 WWW.?.ORG
Our concerns are these: we are recording more complaints from homeowners around the lake and people using the town beach. These individuals have begun to complain about water clarity. They say that the water is often greenish and/or murky. While there have been no complaints about “swimmer’s itch,” there are many complaints about how “weedy” the lake has become. The number of people commenting that the lake “just isn’t a nice place to swim anymore” is on the rise. Furthermore, the popular fishery has begun to show signs of decline. Talks with fishermen at the boat launch indicate that while they are still catching fish, the average size of the fish seems to be getting smaller. The “Trophy Bass” the lake was known for are infrequently caught these days. The number of small “pan fish” (perch, bluegill sunfish, etc…) has risen dramatically and while these are fun for the kids to catch, the sport fishermen aren’t much interested. We are contemplating asking the state DEP to start a trout stocking operation, but we wonder if the lake in its current state could support such a fishery, and we also wonder what the effects of that stocking might be on the lake. It is unclear to us if the problems we describe above are related to one another, or if there is even a solution to them. We know that the first step is developing a clearer picture of the physical, chemical, and biological processes operating in Mystery Lake. We look forward to contracting with you to carry out the survey/management recommendation we need to help us address our concerns. Sincerely,
Allan Ingram Executive Director, Mystery Lake Association
Mystery Pond Watershed Shaded area drains directly to Mystery Pond (Area: 4541 acres) Lake Area: 211 acres Unshaded area drains to Long Pond first, then become inflow to Mystery Pond
Main Watershed Landuse Mystery Pond Landuse Landuse Type
Mystery Pond Indirect
Mystery Pond Direct
Subsidary Watershed Landuse Long Pond Landuse
Grasses and Agriculture Deciduous Forest Coniferous Forest Developed Water Forested Wetland Non-forested Wetland Utility Right of Way Turf and Grass Barren Land
1851 1530 482 274 208 106 59 18 13 2
Grasses and Agriculture Deciduous Forest Coniferous Forest Water Developed Forested Wetland Turf and Grass Non-forested Wetland Utility Right of Way Barren Land
1078 627 385 246 212 151 79 39 5 1
Mystery Pond Bathymetry Sharon, CT
MYSTERY LAKE FISHERIES ASSESSMENT Mystery Lake is inhabited by a wide variety of fish species. In the lake, largemouth bass, bluegill sunfish, common sunfish, and yellow perch are abundant. Brown bullhead, white sucker, golden shiner, red-breasted sunfish, and rock bass are common. Smallmouth bass, calico bass, redfin pickerel and chain pickerel tend to be fairly scarce. There is no currently self-sustaining population of trout in the lake. Mystery Lake is a relatively shallow body of water, having an average depth of only 22 feet. Because the deeper cold waters of the lake are limited in volume and tend to be deficient in dissolved oxygen during the summertime, those waters are not capable of supporting fish. Because of those anoxic conditions in the cold bottom water, Mystery Lake is not suitable for cold-water species such as trout. Instead, it is better managed as a warm water fishery. Present regulations on this fishery include a slot limit restriction and a six fish daily creel limit on all bass species. Yellow perch, bluegill sunfish and largemouth bass have an average to below average growth rate in Mystery Lake. Growth rates for those species could be increased by controlling the dense growth of aquatic weeds. Removal of some macrophytes would appreciably reduce escape cover for bluegill sunfish and yellow perch, making them more available for forage for bass. With an increased food supply, the growth rates of bass should improve. Growth for perch and bluegills would likewise improve since there would be fewer individuals competing for the limiting food supply. Although some weed removal would be beneficial, it would not be advisable from a fisheries standpoint to remove all aquatic macrophytes. Some patches of vegetation are necessary to provide habitat structure, zooplankton refugia and spawning areas.
ADDITIONAL PHYSICAL DATA ABOUT MYSTERY LAKE Watershed Area: 7,364 acres (4541 draining directly, 2823 draining indirectly (through Long Pond)) Surface Area: 201 acres Mean Depth: 22 feet Max Depth: 33 feet Volume: 192,600,000 cubic feet Estimated Water Retention Time: 135 days