Health environmental assessment of the coral reef-supporting Tamandaré Bay (NE, Brazil)

• Textularia associated with total phosphorus and fine grain size show fluvial influence in the embayment;
• FORAM and FORAM STRESS INDICES diagnose a biodiversity hotspot site for conservation initiatives;
• Both FI and FSI show winter as the worst condition for symbiont-bearing foraminifera.
• Favorable conditions for calcification are present in the central transect under the influence of a no-take zone.

This study aimed to assess spatial and temporal ecosystem health variability of coral reefs in the Tamandaré open embayment, located in Northeast Brazil, Southwest Atlantic Ocean, using water and sediment parameters and benthic foraminifera as bioindicators. Sediment samples were collected during the summer and winter of 2005 at the reef base, generally built over beachrock structures. The FORAM index (FI, a foraminiferal functional group, community-based water quality assessment), and the FORAM Stress Index (FSI, which is more related to ecological affinities than to functional groups and assesses sediment or substrata quality) together with geochemical data were interpreted using uni- and multi-variate analysis. This is the first application of FSI outside of Mediterranean waters. The dominance of the Quinqueloculina and Textularia, along with negligible numbers of living specimens, low counts of symbiont-bearing foraminifera (and thus low FI), high turbidity and high phosphorus concentrations confirm the anthropogenic influence of river inputs. All parameters suggest that the water and sediment of the Tamandaré embayment are marginal for coral population settlement, although the FSI, which presents higher values at unpolluted ecosystems, suggests more sustainable conditions during summer than winter, as found for FI. The FI indication of marginal environmental health is not in agreement with the FSI and the currently stable coral population found over the underlying beachrock, especially at the established no-take zone where good conditions have been described. The central transect, influenced by the no-take zone, presents the most favorable sedimentary sector for conservation initiatives, as indicated by foraminifera and other variables, preferentially on the summer season due to low river discharge of sediments. Local scientific- and community-based coral conservation initiatives have improved ecosystem health.

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