doi:10.3723/ut.37.029 Underwater Technology, Vol. 37, No. 1, pp. 29–33, 2020
A simple in situ labelling approach and adequate tools for photo and video quadrats used in underwater ecological studies Bernabé Moreno Laboratorio de Ecología Marina, Universidad Científica del Sur, Lima 15067, Peru
Technical Briefing
www.sut.org
Received 23 December 2019; Accepted 25 February 2020
Abstract Ecological studies use quadrats to gather qualitative (1/0) and quantitative (density and surface coverage) information in terrestrial and marine sciences. Depending on the spatiotemporal scale of the assessment, this could be a pilot or a monitoring survey. For monitoring surveys, it is necessary to develop a code for the quadrat itself (in situ labelling), for the digital file (ex situ codification), and ideally, for both. The design of the quadrat used for these studies must accomplish ergonomics through certain specifications such as: made of highly resistant material; negative-buoyant but lightweight; anticorrosive (specially for marine environments); able to stay positioned on seafloor habitat; and compatible with the in situ labelling technique. The present paper is a comparison of quadrats of different materials and widths, including the implementation of an in situ and ex situ codification technique. Recommendations are made after several test hours sampling with quadrats. Keywords: scientific diving, NaGISA, underwater imaging, benthic ecology
1. Introduction Quadrats are widely used in terrestrial (Adler et al., 2007) and marine ecological studies (Iken and Konar, 2003) as they enable collection of standardised data at locations; comparison between sites subjected to (dis)similar environmental settings; and construction of extensive time series through monitoring efforts. Quadrat analysis includes assessing quantitative values of species or functional groups, which are key for punctual evaluations and in particular long-term assessments. In marine subtidal ecosystems, when functionality is prioritised over species identification, non-destructive methodologies * Contact author. Email address: 8ernabemoreno@gmail.com
are used to obtain information in a way that avoids collection of the whole macrobenthic community within the area (Peirano et al., 2016; Balazy et al., 2018). Incorporating a less invasive approach into classic photo and video transects has enabled efficient assessments of marine ecosystems (e.g. Beijbom et al., 2015; Bryant et al., 2017). Subtidal sampling protocols particularly designed for long-term evaluations require the ability for replicates and transects to be tracked, for which some sort of codification is necessary. This labelling can be done a) in situ, by using the quadrat itself to show certain codes, and b) during the data download by renaming files (Fig 1); however, ideally both methods are used. It is important to ensure an adequate labelling system for postprocessing image data in software such as VidAna (Hedley, 2003) or CPCe (Kohler and Gill, 2006). There are several standardised quadrat designs (e.g. Cook et al., 2013); some have been developed for specific camera attachments that allow the quadrat to be placed directly onto the camera for more automatic framing (Van Rein et al., 2011; Beijbom et al., 2015; Ashton et al., 2017). The camera-quadrat combination is useful for exhaustive monitoring; however, it is not adequate for environmental conditions such as strong currents, high turbidity and varying seafloor topography. When using a photo or video quadrat it is important to maintain the linearity on the straight lines (Fig 2). Good buoyancy is required from the diver, and the quadrat should not move once positioned over the benthos. The weight effect (opposite to the buoyant force) must be considered in order to manufacture a quadrat that is resistant and heavy enough to remain in place, but light enough to transport without additional help (e.g. other diver
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