Response of Benthic Foraminifera to Organic Matter Quantity and Quality and Bioavailable Concentrations of Metals in Aveiro Lagoon (Portugal)

Abstract

This work analyses the distribution of living benthic foraminiferal assemblages of surface sediments in different intertidal areas of Ria de Aveiro (Portugal), a polihaline and anthropized coastal lagoon. The relationships among foraminiferal assemblages in association with environmental parameters (temperature, salinity, Eh and pH), grain size, the quantity and quality of organic matter (enrichment in carbohydrates, proteins and lipids), pollution caused by metals, and mineralogical data are studied in an attempt to identify indicators of adaptability to environmental stress. In particular, concentrations of selected metals in the surficial sediment are investigated to assess environmental pollution levels that are further synthetically parameterised by the Pollution Load Index (PLI). The PLI variations allowed the identification of five main polluted areas. Concentrations of metals were also analysed in three extracted phases to evaluate their possible mobility, bioavailability and toxicity in the surficial sediment. Polluted sediment in the form of both organic matter and metals can be found in the most confined zones. Whereas enrichment in organic matter and related biopolymers causes an increase in foraminifera density, pollution by metals leads to a decline in foraminiferal abundance and diversity in those zones. The first situation may be justified by the existence of opportunistic species (with high reproduction rate) that can live in low oxic conditions. The second is explained by the sensitivity of some species to pressure caused by metals. The quality of the organic matter found in these places and the option of a different food source should also explain the tolerance of several species to pollution caused by metals, despite their low reproductive rate in the most polluted areas. In this study, species that are sensitive and tolerant to organic matter and metal enrichment are identified, as is the differential sensitivity/tolerance of some species to metals enrichment.

Possible Functions of Biomineralization of Some Textulariid (Foraminifera) Species of the Nw Iberian Margin

“…The pore water sedimentary pH, and TOC values of Station 7 at the Ria de Aveiro, were based on Martins et al (2015b).…”

“…Arenoparrella mexicana is dominant or common in coastal transitional areas with low salinity occurring for instance in mangrove swamps and marshes (Debenay, 2012;Martins et al, 2015b). The wall of this species (Fig.…”

Living benthic Foraminifera from the Saquarema lagoonal system (Rio de Janeiro, southeastern Brazil)

“…The residual fraction in each sieve was dried at 50°C and the Foraminifera were removed from the remaining sediment by flotation in trichloroethylene, using the difference in density (Martins et al 2015a). All stained Foraminifera were picked out from the sample, identified, and counted under stereoscopic microscopic at 80× magnification.…”

“…In the last decades, Foraminifera have been widely used as a proxy to describe the quality of coastal environments (Laut et al 2011;Martins et al 2013Martins et al , 2015a. Foraminifera are commonly used as bioindicators because their short life cycles offer insight into rapid environmental changes (Murray 2006).…”

“…Sediment characteristics are one of the principal determinants of their distribution; benthic Foraminifera live more abundantly in silty and clayey sediments. However, Foraminifera are also can be influenced by sediment pollution (Bhalla & Nigam 1986;Alve & Olsgard 1999;Frontalini & Coccioni 2008;Martins et al 2013Martins et al , 2014Martins et al , 2015a. The aim of this study is to characterize the living benthic foraminiferal assemblages on surface sediments from the SLS in order to serve as a background to future ecological and paleoecological studies, as well as contribute to research on the biodiversity and distribution of Foraminifera throughout Brazilian coastal lagoons.…”