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Gettysburg College

Publication Date

Spring 2022

Program Name

Panama: Tropical Ecology, Marine Ecosystems, and Biodiversity Conservation

Abstract

Coral reefs are important marine ecosystems, as they support biodiversity and generate buffer zones, yet their abundance is incredibly limited globally. One of the main threats that coral reefs face is excessive macroalgal coverage, which limits sunlight from reaching corals, and thus, limits the energy that can reach them. Parrot fish (Scaridae) are keystone herbivores, as they consume macroalgae growing on corals, which aids in reef survivability. While there is previous research on the abundances, sizes, and feeding habits of Scaridae species in the Caribbean, there is no published research on how community structure and feeding preferences of parrot fishes differ within coral reef ecosystems of varying substrate composition. This study assesses the community structure and feeding preferences of Scaridae in the fringing and barrier reefs, reefs of differing substrate composition, of Anmardub Island in Guna Yala, Panama. To determine the substrate composition of fringing and barrier reefs, percent coverages of sand, algae, sponge, dead coral, fire coral, coral rubble, hard coral, and soft coral, were quantified using a 1m2 threaded quadrat along 6 30x1m belt transects at varying depth levels (0-2.0m, 2.1-4.0m, 4.1-6.0m) in each reef. These transects were placed 30m away from each other, and parallel to the shore. Using these same transects, visual censuses were conducted, in which Scaridae species within 1m of either side of the transects had their densities, size proportions (0-10.0cm, 10.1-20.0cm, 20.1cm+), and proportions of coral species consumption, recorded. Across all depth levels, the fringing reef has significantly higher percentages of sand coverage, t(62)=4.33, p<.001; t(60)=7.78, p<.001; t(59)=4.27, p<.001, and dead coral coverage, t(59)=6.47, p<.001; t(59)=8.72, p<.001; t(59)=4.30, p<.001, while the barrier reef has significantly higher percentages of hard coral coverage, t(116)=3.13, p=.0022; t(118)=8.03, p<.001, at the 0-2.0m and 2.1-4.0m depth levels. Thus, the barrier reef is generally healthier and more consistent than the fringing reef. Scaridae species densities differ significantly between fringing and barrier reefs at the 0-2.0m depth level, X2 (4, N=184,164)=52.70, p<.001, as there are significantly higher densities of Scarus iseri and Sparisoma rubripinne in the fringing reef, and significantly higher densities of Nicholsina usta, Sparisoma aurofrenatum, and Sparisoma viride in the barrier reef. Across all depths of fringing and barrier reefs, there is a weak positive correlation between substrate variability and Scaridae species diversity, R2=.0057, F(5)=.023, p=.89. There is also a significant difference in Scaridae coral species consumption proportions across all depth levels, X2 (3, N=140,54)=66.55, p<.001; X2 (4, N=20,47)=53.07 p<.001; X2 (6, N=76,94)=108.74, p<.001, as significantly higher proportions of Scaridae consume macroalgae and algal turf on dead coral in the fringing reef, while significantly higher proportions of Scaridae consume macroalgae on coral rubble and Porites porites in the barrier reef. Based on these results, we can conclude that there is a relationship between coral reef substrate composition and Scaridae species densities at the 0-2.0m depth level, and across all depth levels, a relationship between coral reef substrate composition and Scaridae diversity and feeding preferences.

Disciplines

Environmental Indicators and Impact Assessment | Latin American Studies | Oceanography | Research Methods in Life Sciences | Terrestrial and Aquatic Ecology | Zoology

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