Foraminiferal assemblage and reef check census in coral reef health monitoring of East Brazilian margin

Abstract

Human activity is changing environmental conditions on a global scale. Among the ecosystems that are affected by human activities, coral reefs are among the most prominent. In Brazil, the coral reefs of the Corumbau Marine Extractive Reserve (CMER) and Abrolhos National Marine Park (ANMP) in Bahia state have some of the highest coral cover in the South Atlantic Ocean. Hard coral cover, algal cover, and foraminiferal population distribution patterns were used to assess the coral reef benthic environments, and define a background that can be used in worldwide comparisons in future studies. To compare these two monitoring approaches in different coral reef environments, relative frequency data for occurrence of hard coral and algal cover, using point-intercept transects as proposed by the Reef Check protocol, and foraminiferal samples were collected from Corumbau (nearshore) and Abrolhos (offshore) in April 2005. The foraminiferal assemblage was evaluated using the FORAM index (FI — Foraminifera in Reef Assessment and Monitoring), which provides a numeric diagnosis of suitability of benthic habitat to support calcifying organisms that host algal symbionts, originally developed for Caribbean reef areas. Coral cover in the surveyed areas, both in Corumbau and in Abrolhos, ranged from 13% to 37%, while high foraminiferal diversities (H') were found in all stations. Dominance of symbiont-bearing taxa of Amphistegina lessonii and Archaias angulatus only occurred at two shallow stations, Mato Verde and Siriba, both in Abrolhos, where FI > 4.00. Stations located in Corumbau and Abrolhos had FI values < 4.00. Q-mode cluster analysis showed that foraminifers have specific preferences for physical conditions, especially hydrodynamics and light availability, which influence the FI index. Although coral cover in these areas can be considered good by regional standards, foraminifer analysis showed that the benthic system was unfavorable for symbiont-bearing foraminiferal species at most stations. This discrepancy reveals that the FI must be used with caution in areas other than the northwestern Atlantic and Caribbean where it was developed, and that some coral species can thrive in muddier conditions than can most symbiont-bearing foraminifers.