Bioerosion by microbial euendoliths in benthic foraminifera from heavy metal-polluted coastal environments of Portovesme (south-western Sardinia, Italy)

Abstract

Abstract.A monitoring survey of the coastal area facing the industrial area of Portoscuso-Portovesme (south-western Sardinia, Italy) revealed intense bioerosional processes. Benthic foraminifera collected at the same depth (about 2 m) but at different distances from the pollution source show extensive microbial infestation, anomalous Mg/Ca molar ratios and high levels of heavy metals in the shell associated with a decrease in foraminifera richness, population density and biodiversity with the presence of morphologically abnormal specimens. We found that carbonate dissolution induced by euendoliths is selective, depending on the Mg content and morpho-structural types of foraminiferal taxa. This study provides evidences for a connection between heavy metal dispersion, decrease in pH of the sea-water and bioerosional processes on foraminifera.

Interpretation of coastal sediment quality based on trace metal and PAH analysis, benthic foraminifera, and toxicity tests (Sardinia, Western Mediterranean)

“…These studies revealed high concentrations of Hg, Cd, Pb, and Zn that correspond to low species diversity, low population density and more frequent abnormal specimens. The foraminiferal assemblages recognised by Cherchi et al (2009Cherchi et al ( , 2012 appear very similar to those retrieved in the PS4 sample.…”

“…Cluster A includes stations characterised by a lower content of contaminants (PAH and trace metals), whereas Cluster B (most polluted) comprises samples located mainly in the harbour areas of La Maddalena (LM6, LM7), S. Stefano (LM8, LM9), Calasetta (PS4) and Porto Torres (PT2, PT3, PT4), which are characterised by high levels of contaminants, muddy sediments and low values of biotic indices. The stressed environmental conditions in the southwestern area of Sardinia (Portoscuso-Portovesme) have also been highlighted in previous studies (Cherchi et al, , 2012 through analysis of the biotic indices of foraminifera tests and chemical analysis of the sediments (Schintu et al, 2009). These studies revealed high concentrations of Hg, Cd, Pb, and Zn that correspond to low species diversity, low population density and more frequent abnormal specimens.…”

Spatial distribution of benthic foraminifera in the Lagos Lagoon (Nigeria): Tracing the impact of environmental perturbations

“…The finding is in accordance with a recent study, that revealed FN numbers ranging from 0.6 to 45.8 g -1 in the most polluted area harbor areas [9]. Low foraminiferal abundances were also recorded from other sites impacted by oil discharges (PAH's) and heavy metals [68,[71][72][73][74] and commonly goes hand in hand with a decrease in species richness [48,50]. In severely polluted but regularly flushed harbor areas, where rates of seawater exchange are high and water residence time remains short, high diversity assemblages, composed of both marine, brackish and marginal marine biotas, continue to be promoted [75].…”

Dead sands: bioerosion of alien foraminiferal shells in a Mediterranean seagrass meadow

“…ecosystems, e.g., through abiotic dissolution (e.g., (Green et al, 1993)) and bioerosion (e.g., (Cherchi et al, 2012)), transformation of the shells into lime mud, i.e., the important matrix of both recent and ancient calcareous sediments (e.g., (Debenay et al, 1999)), etc. Here, while the abiotic dissolution and mechanical damage contributed only little, the majority (>70%) of the substrate shells showed at least some signs of bioerosion, with 13% being highly bioeroded.…”