Benthic foraminifera geochemistry as a monitoring tool for heavy metal and phosphorus pollution - A post fish-farm removal case study

Benthic foraminiferal community structure and its response to environmental factors revealed using high-throughput sequencing in the Zhoushan Fishing Ground, East China Sea

Benthic foraminifera are excellent tools for monitoring marine environments and reconstructing paleoenvironments. This study investigated the structure and diversity of benthic foraminiferal communities in 20 superficial sediment samples obtained from the Zhoushan Fishing Ground (ZFG) using high-throughput sequencing based on small subunit ribosomal DNA and RNA amplification. The results revealed Rotaliida as the most dominant group, with spatial heterogeneity in foraminiferal distribution. Total benthic foraminiferal communities exhibited higher species richness and diversity compared to active communities. While heavy metal pollution in the ZFG was moderate, areas with elevated concentrations of heavy metals exhibited low diversity and richness in foraminiferal communities. Total foraminiferal community structure was primarily influenced by factors such as water depth and Hg, Pb, Cd, and Zn levels. Notably, Hg levels emerged as a critical factor impacting the structure and diversity of the active foraminiferal community. The dominant species, Operculina, exhibited tolerance toward heavy metal pollution.

Lead and cadmium exposure alters shell morphogenesis in a single-chambered, agglutinated foraminiferan protist

Changes to calcareous foraminiferal shell morphology are well documented in heavy metal-polluted marine environments, however less is known about how these toxicants affect agglutinated foraminifera, particularly single-chambered (monothalamid) species. Here we used an agglutinated monothalamic foraminifer, Astrammina rara, to study shell morphogenesis during exposure to lead (Pb) and cadmium (Cd). Isolated cell bodies incubated with artificial sediment and control, Pb-, or Cd-spiked artificial seawater constructed new agglutinated shells in four weeks. Time-lapse recordings showed normal motile behavior during treatments. SEM imaging of reconstructed shells, however, revealed dramatic deformations in the bioadhesive of Pb-exposed shells, and less so in Cd-exposed shells. ICP-MS analysis of the isolated shells showed elevated levels of Pb, but not Cd, in the bioadhesive of treated specimens, indicating that the two metals exert their effects differentially. These findings show that certain agglutinated foraminifera may be useful indicator species in studies of heavy metal-polluted benthic marine environments.

130 years of heavy metal pollution archived in the shell of the intertidal dog whelk, Nucella lapillus (Gastropoda, Muricidae)

Heavy metals in coastal waters are a great environmental concern in the North Sea since the middle of the 20th century. Regulatory efforts have led to a significant reduction in atmospheric and water-transported heavy metals. Still, high concentrations of these in sediments remain a risk for ecosystems, requiring close monitoring. Here, we investigated the applicability of Nucella lapillus museum collections as a tool for targeted tracking of chronic anthropogenic heavy metal pollution. We analysed the concentration ratios of the common heavy metals Cu, Cd, Pb, and Zn in relation to Ca in N. lapillus shells collected from the Dutch and Belgian intertidal zone over the last 130 years. We found that shell Cu/Ca and Zn/Ca concentration ratios remained remarkably constant, whereas Pb/Ca concentration trends were closely aligned with emissions of leaded petrol in Europe. Our results suggest that N. lapillus provides a suitable Pb pollution archive of the intertidal zone.

Establishing Baseline Assessment Levels for Monitoring Coastal Heavy Metals Using Foraminiferal Shells: A Case Study from the Southeastern Mediterranean

One of the challenges in monitoring the marine coastal environments is quantifying the magnitude and duration of pollution events. This study introduces a new concept of defining heavy metal (HM) baseline assessment levels (BALs) in coastal environments using foraminiferal shells. We demonstrated the potential of this approach by examining a nature reserve along the Mediterranean coast of Israel. Our previous investigation of this site in 2013–2014 using foraminiferal single-chamber LA-ICPMS created a large dataset consisting of HM measurements of two species, Lachlanella and Pararotalia calcariformata. This database was used to establish the BAL of Zn, Cu and Pb, associated with anthropogenic sources. In February 2021, a significant tar pollution event affected the entire Mediterranean coast of Israel, derived from an offshore oil spill. This event provided a unique opportunity to test the applicability of the foraminiferal BAL by comparing it to whole-shell ICPMS measurements of the two species collected in winter and summer 2021. Results reveal a significant increase (2–34-fold) in the three HMs between 2013–2014 and 2021, with Pb/Ca displaying the most prominent increase in both species. This suggests a possible linkage between the oil spill event and the significantly elevated metal/Ca ratios in 2021.