Variação espaço-temporal da macrofauna bentônica da zona entremarés da Resex da praia do Canto Verde, Beberibe - Ceará

Abstract

Sandy coastlines are dynamic environments where the physical structure of the habitat is determined by the interaction between sand, waves, and tides. The state of Ceará has extensive stretches of sandy beaches along the coast, however, studies related to the benthic ecology of these environments are still scarce and recent. The influence of beach morphodynamics and seasonal rainfall variations on the composition and distribution of the benthic macrofauna of Canto Verde beach was evaluated semiannually from October 2015 to December 2018. The height and wave period, particle size, temperature, salinity, rainfall and tidal extension were recorded, and morphodynamic indexes were calculated for beaches: Dean (Ω), Relative Tide Length (RTR) and Beach Index (BI). Macrofauna was characterized as density, richness and MSR (richness in each transect). The Canto Verde beach varied between two morphodynamic types - low tide terrace and low tide bar/rip, influenced by the variations between rainy and dry periods, which modify the currents pattern and the contribution of sediment on the beach. The polychaete Hesionura sp. and the bivalve Donax striatus contributed to the formation of the groups of samples in the dry and rainy periods, respectively. This result may be related to several factors, such as population characteristics of each species (reproduction and recruitment) and environmental (food availability and beach morphodynamic conditions). The sediment grain size, rainfall, and RTR index together determined the differences in the structure of the benthic macrofauna of Canto Verde beach. The present study revealed that the ecosystemic characteristics of Canto Verde beach fluctuate temporarily with current regional climatic variations and appear to be little affected by mesoscale phenomena already evident in some beaches of the coast of Ceará. The continuity of this study is of great relevance for a systematic evaluation of the conditions of the beach and its associated macrofauna aiming at the detection and understanding of the changes in the biota, as well as to the basis of management plans to mitigate their causes and adaptation to its effects, should they occur.