Symbiont-bearing foraminifera as health proxy in coral reefs in the equatorial margin of Brazil.

Abstract

Coral communities worldwide are progressively more stressed by anthropogenic activities that increase fluxes of sediment and other pollutants to nearshore areas. Some nearshore coral reef environments off the Equatorial margin of Brazil, including Pirangi and Maracajaú, Rio Grande do Norte (RN, Brazil), seem to be under human-induced stress. However, the horizontal extent of this stress, its effects, and assessment of the environmental response depend on the hydrodynamic conditions (circulation and deposition patterns), sedimentary facies, and the availability of biological indicators. We investigate two Brazilian live reefal corals' communities by examining seven photosymbiont-bearing species (PSB) of Foraminifera, Amphisorus hemprichii, Amphistegina gibbosa, Archaias angulatus, Borelis schlumbergeri, Heterostegina antillarum, Peneroplis carinatus, and Laevipeneroplis proteus, using numerical analysis FORAM Index (FI), grain size, and particulate organic and inorganic carbonate. Here, we show that coarse sand fraction followed by fine sand fraction and high hydrodynamics plays an important role in transportation and deposition of sediments and foraminiferal tests in the study area. According to FI results, conditions at Pirangi are not suitable for coral reef growth. Maracajaú has sites that are suitable for coral reef growth and sites where coral could not survive after a stress event. We need long-term assessments to improve our knowledge of the distribution and ecological importance of Brazilian reef-dwelling foraminifers and to extend the application of FI to monitoring management plans of the Pirangi and Maracajaú National Marine Parks by providing a first insight into the biodiversity patterns and a reliable tool of the reconstruction of paleo reef health.