Annual dynamics of benthic foraminiferal populations in the Tramandaí-Armazém Lagoon, southern Brazil

Eduarda Pacheco Martins,Cristianini Trescastro Bergue,Karlos Guilherme Diemer Kochhann

doi:10.1590/2675-2824069.20-331epm

Abstract

Abstract Modern coastal environments are considered highly selective and dynamic, not only due to the natural variability of physical and chemical parameters, but also because of anthropogenic contamination. Our study aims to identify environmental and/or anthropogenic factors influencing benthic foraminiferal abundances over a period of one year in the Tramandai-Armazem Lagoon, southern Brazil. Assemblages were composed exclusively of agglutinated species assigned to the genera Trochammina, Trochamminita, Ammotium, Haplophragmoides and Miliammina. Total abundances varied throughout the year, reaching the highest values during the wetter months of March and July, when living and dead assemblages became dominated by Ammotium salsum. This pattern is likely related to salinity fluctuations due to changes in freshwater input that, consequently, affected the amount of organic matter (e.g., phytodetritus) brought into the lagoon by surrounding drainages. To assess the impact of anthropogenic pollution, we evaluated total relative abundances of deformed tests in the Tramandai-Armazem Lagoon. Relative abundances of deformed tests were the highest during the months of January and March, when contaminant (e.g., sewage) discharge was probably increased due to the seasonal population growth in the region.

Highlights

Benthic foraminifera are distributed globally in the marine realm, from estuarine areas to abyssal plains, reflecting the remarkable abundance and diversity of this group of organisms
Assemblages are composed of Ammotium salsum, Haplophragmoides wilberti, Miliammina earlandi, Trochammina inflata and Trochamminita salsa (Figure 2; Table 1)
The benthic foraminiferal community monitored between October 2018 and September 2019 presented large variations in total abundances (Table 1)

Summary

Introduction

Benthic foraminifera are distributed globally in the marine realm, from estuarine areas to abyssal plains, reflecting the remarkable abundance and diversity of this group of organisms. Since benthic foraminifera are sensitive to natural (e.g., salinity, temperature, pH, food availability) and anthropogenic (trace elements concentration) changes, they are extensively applied as bioindicators of environmental quality (Schönfeld et al, 2012). This application of benthic foraminifera was developed in the 1960’s and increased in popularity. Benthic foraminifera from coastal areas respond to environmental changes by changing density and diversity, structure of assemblages and/or morphology of tests (Murray, 1991).

Methods

Results

Discussion

Conclusion