International Journal of Marine Science, 2024, Vol.14, No.1, 29-39 http://www.aquapublisher.com/index.php/ijms 37 Five video transects (zone A; zone B; zone C; zone D; zone E) were systematically selected to encompass a spectrum of complexity within the habitat. The objective was to procure a comprehensive array of images and videos depicting the surrounding environment, aiming to capture a diverse spectrum of species. These zones are delineated as follows: A) Central core HCAR, B) Interior of the central core HCAR, C) Individual HCAR, D) Interior of individual HCAR, and E) Sandy bottom hosting C. racemosa (Figure 2A; Figure 2B; Figure 2C; Figure 2D). While the water column was evaluated in some cases, the data was not included in the analysis. Notably, video images were acquired from October to August at seasonal intervals (autumn, spring, and summer) to study temporal abundance variations across seasonal and spatial scales. Scuba divers meticulously captured video footage both within and outside the AR area throughout these seasons, although winter recordings were absent due to adverse sampling conditions. Species identification was conducted using the comprehensive Froese and Pauly (2019) web database. For illustrative purposes, an example of fish species identification can be found (Figure 4). A sequence of approximately 5-second video intervals was established to facilitate quantification and comparative analysis of fish assemblage descriptors. To manage large fish counts, observations exceeding 20 were capped (Tessier et al., 2004; Condal et al., 2012). Trophic level determination focused only on species identifiable at the genus and species levels. Figure 4 Examples of images for fish species identification Note: Pomadasys incisus (A), Mullus surmulletus (B), Diplodus sargus (C), Dipludus vulgaris (D), Serranus cabrilla (E), Molamola (F) Community parameters per video interval sample included total fish count, distinct fish species count, fish species abundance, computation of Shannon-Weaver Diversity Index (H’). In accordance with the methodologies outlined by Shannon and Weaver and Krebs, the computation of the Shannon-Weaver Diversity Index (H') involved several steps, with each H' calculated for every 5-second video interval. Initially, data collection encompassed recording the presence of species in video intervals. Subsequently, proportions of individuals for each species were calculated by dividing the number of individuals of a species by the total number of individuals observed across all species within each 5-second interval. These proportions were then subjected to natural logarithm transformation to handle the continuous nature of the diversity measure. Multiplying each proportion by its corresponding natural logarithm yielded values, which were summed across all species to obtain a cumulative value. Finally, the negative Shannon-Weaver Index was derived by multiplying the sum by -1, resulting in the Shannon-Weaver Diversity Index (H'). This approach facilitated a detailed assessment of species diversity dynamics over time, with higher H' values indicating greater diversity within each interval. In addition, we investigated the trophic structure of the ecosystem by determining the Trophic Level per species (TL) following the framework established by Pauly and Watson (2005). This involved assessing the position of each species in the food web based on its feeding habits and interactions. Both the Mean Trophic Level across all recorded data and the Weighted Mean Trophic Level, which takes into account the frequency of each species occurrence, were computed. These trophic level calculations provide insights into the energy flow and trophic relationships within
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