Diversidade funcional das assembleias de peixes em praias tropicais com diferentes graus de morfodinamismo

Abstract

Beaches are a major influencer in the distribution and composition of fish species, and this is mainly due to the actions of winds, waves and tidal amplitude. Fish assemblages in places with great exposure to waves have a lower species richness, and this is due to the turbidity of the waves acting as a filter, while more protected places will have a greater number of species, through rocky shores, serving as a barrier against the impacts of the waves. In northeastern Brazil, we found a range classified as mesotidal, which is important for the beach structure. The aim of the present study is to analyze how the functional attributes are distributed across the different types of exposure degree of the beaches, in different degrees of hydrodynamics. To answer the following questions: 1) Does wave exposure affect the functional and taxonomic diversity of fish assemblages? 2) What are the main environmental variables that explain the variation in functional diversity between beaches?. Samplings were carried out in northeastern Brazil on nine beaches according to their degree of exposure (Tide-dominated Beaches: Coqueirinho, Camurupim, and Curva do Pontal; Maré Modified: Bessa, Pontal and Formosa; Wave-dominated Beach: Campina , Intermares and Cabo Branco). Fish were collected using a beach seine trawl, where environmental variables (salinity, depth, transparency, and temperature) and morphodynamics (wave height, wave frequency, time waveforms and sediment types). Eight functional attributes were selected, taking into account locomotion and diet, through fish morphology with a digital caliper and use of a literary reference. To analyze the environmental variables with the degree of exposure, a (PERMANOVA) was used, the same was done for the community between the beaches, a posteriori a pair-wise was made between the environmental and abundance between the beaches. To analyze the functional diversity, the indices of functional richness (FRich), Functional uniformity (FEve) and functional redundancy (FRed) were used. Then, the correlation between the functional attributes and the environmental variables was verified through the RLQ analysis. We used the CWM (Community-Weighted Mean) to find out which traits were most prevalent on each beach. In total, 118 species of fish were caught on the beaches. Our results showed that higher abundances and functional diversity were recorded on beaches dominated and modified by the tides. To analyze the functional diversity, the indices of functional richness (FRich), Functional uniformity (FEve) and functional redundancy (FRed) were used. Then, the correlation between the functional attributes and the environmental variables was verified through the RLQ analysis. We used the CWM (Community-Weighted Mean) to find out which traits were most prevalent on each beach. In total, 118 species of fish were caught on the beaches. Our results showed that higher abundances and functional diversity were recorded on beaches dominated and modified by the tides. In addition, the traits were quite distinct in each type of beach, where it was observed that tidal dominated beaches are associated by individuals with a compressiform body and lanceolate caudal fins, in addition to a zoobenthivorous diet, which help us to have a greater interaction with height. and wave time; On the other hand, at beaches with lower hydrodynamics, individuals were associated with a sagittiform body shape.