Benthic foraminifera assemblages as elemental pollution bioindicator in marine sediments around fish farm (Vrgada Island, Central Adriatic, Croatia)

Benthic foraminifera as bio-indicators of natural and anthropogenic conditions in Roscoff Aber Bay (Brittany, France)

Living benthic foraminifera, known as environmental bio-indicators of both natural and anthropogenic conditions in marine environments, were investigated in the coastal environment of Roscoff Aber Bay (Brittany, France). Eight sampling sites subject to natural variations (freshwater inputs, tides) and/or anthropogenic impacts (pollution, eutrophication) were studied over four seasons in 2021-2022 (November, February, May, August). We sought to understand the spatial distribution of foraminiferal populations within and between sampling sites over the different seasons and to identify sensitive species and those tolerant to anthropogenic impacts. To this end, sedimentary and biogeochemical characteristics of the sediments were examined by measuring grain size, temperature, oxygen, salinity, pH, environmental pigment concentration (chl a and phaeopigments), total organic carbon (TOC), isotopic ratios of carbon (δ13C), nitrogen (δ15N) and sulfide (δ34S), and chl a fluorescence. Considering these parameters as potential driving factors, four environments were distinguished among the sampling sites: open water, terrestrial, oligotrophic and eutrophic. These showed an increasing gradient of organic supply as well as very different microbial activities, highlighted by carbon and sulfide isotopic ratios. Foraminiferal population study revealed the dominant species characterising these main environments. The lowest abundance but highest diversity of foraminifera was found in the harbour site, associated with the dominance of Haynesina germanica, suggesting this species is tolerant to eutrophic environments and anthropogenic impacts. Open water was dominated by Ammonia beccarii and Elphidium crispum, while Quinqueloculina seminula was the most abundant species in the site with the greatest terrestrial influence. Interestingly, the observed organic enrichment of the harbour due to anthropogenic activities (fisheries, waste deposits, etc.) does not seem to significantly affect foraminiferal diversity. Overall, the benthic foraminiferal species in Roscoff Aber Bay appear to be an excellent proxy for marine environmental conditions under various natural and anthropogenic influences.

Pollution level assessment, source apportionment, and health hazards of heavy metals and rare earth elements in the sediment core from the coast of Karachi, Pakistan

Evaluating the elemental composition of sediment cores is essential for understanding environmental changes, including depositional variations, soil formation processes, and human influences. Such investigations offer insights into the biological, geochemical, and industrial impacts on sediment quality and the health of marine ecosystems. This study evaluates the pollution levels and their sources along the coast of Karachi, Pakistan, as well as the effects of pollution on human and ecological health. The core sediment's elemental composition was determined by Neutron Activation Analysis. The mean values in mg/kg of the elements are Al (34800), As (11.15), Ba (371), Br (18.40), Ca (118850), Ce (41.43), Co (10.29), Cr (62.41), Cs (5.27), Eu (0.80), Fe (22855), Hf (2.43), K (11210), La (20.84), Lu (0.26), Mg (21750), Mn (416), Na (8350), Nd (18.92), Rb (66.35), Sb (1.04), Sc (8.31), Se (8.23), Sm (3.88), Sn (17.05), Ta (0.77), Th (7.17), U (3.96), V (71.80), Yb (1.28) and Zn (581). Various pollution indices were used to assess the pollution level of these elements in the sediment core. Statistical tools like Pearson's correlation matrix and Factor analysis were utilized for source apportionment of these elements. Source apportionment showed the sources of heavy metals and rare earth elements are Ship breaking facilities, different types of refuse effluents carried by the Malir river into the sea and the geology of the area. Carcinogenic and non-carcinogenic health hazards associated with exposure to toxic metals were also calculated. The ecological risk factor and sediment quality index showed As and Zn may harm the marine environment. In conclusion, this study found that the sediment of Karachi's coast is polluted with high levels of As, Br, Ca, Cr, Sn, and Zn; with As, Cr and Zn posing a threat to the marine ecology as well as human health.

Effect of cage culture on sedimentary heavy metal and water nutrient pollution: Case study in Sansha Bay, China

The aquaculture area in China's coastal waters has increased rapidly from 6000 km2 in 1990 to 22,000 km2 in 2020. Despite extensive research regarding the effect of coastal aquaculture on water and sediment pollution, evaluating the quantitative relationship between aquaculture and pollutants remains challenging. Sansha Bay, the world's largest cage aquaculture base for Pseudosciaena crocea, is a typical enclosed bay used for investigating aquaculture pollution. A cage culture database is established from 2000 to 2020 in Sansha Bay. Meanwhile, 236 sediment samples from 3 sediment cores and 67 water samples from 4 transects are obtained from the bay for experiments. The main indicators are five nutrients (NO3-, SiO32-, PO43-, NH4+, and NO2-) in the water samples, the grain size, the heavy metal (Zn, Cu, Pb, Cr, Cd, and As) content, and the 210Pb radioactivity in sediment samples. Based on data obtained and a new calculation method, the annual increment in Zn, Cu, As, Cd, Pb, and Cr contents in the cultured zone is shown to increase by 2137 %, 1881 %, 506 %, 300 %, 202 %, and 118 % in 2000-2018, respectively, as compared with the levels in a noncultured zone. The activities of the cage culture increased NO3- by 9 %, PO43- by 30 %, NH4+ by 115 %, and NO2- by 232 %, compared with natural conservative mixing processes, such as the mixing of SiO32-, in 2020. A novel quantitative approach with broad applicability is proposed to evaluate the magnitude of anthropogenically induced environmental contamination. The effectiveness of the proposed technique is demonstrated through a case study conducted in Sansha Bay, China.

Assessment of potentially toxic elements in water and sediments in the drainage network of Lake Mariout, Egypt

The present work investigated the distribution and assessment of potentially toxic elements (PTEs) in the water and surface sediments of both Qalaa and Umum Drains. The water samples were taken from eighteen sampling sites covering the downstream part of the two drains before reaching Lake Mariout Main Basin (LMMB) and Lake Mariout Fishery Basin (LMFB) during the summer period. The samples collected were analyzed for Cu, Cd, Zn, Co, Ni, Mn, Fe and Al. Pollution loading index (PLI), enrichment factor (EF), contamination factor (CF), Geo accumulation index (Igeo) and sediment quality guidelines (SQGs) were calculated as a criterion of possible contamination. Qalaa Drain is characterized by a low pH value of 6.93 compared to the other waters in the studied areas. The lowest Cl was always recorded in the water of Qalaa Drain with an average of 0.65 g Cl/L. The water of Umum Drain, LMMB and LMFB are continually aerated with O2 concentration, compared to the Qalaa drain, which constantly carries H2S. The outcomes revealed that the concentrations of the dissolved metals are at suitable levels according to U.S. Environmental Protection Agency (USEPA). Fe and Al are the two abundant metals in the sediment of the four studied areas. The order of abundance of the metals in the sediments of the present study areas was Fe > Al > Zn > Mn > Cu > Ni > Co > Cd. For the sediments, only cadmium and zinc concentrations in all sites during the study period exceeded the average shale rock concentration. According to the examined indices, the level of contamination in Qalaa Drain ranges from considerable to extremely high. Additionally, the four examined regions have higher Cu and Zn contents than SQGs.

Distribution Patterns of Benthic Foraminifera in Fish Farming Areas (Corsica, France): Implications for the Implementation of Biotic Indices in Biomonitoring Studies

Corsican marine aquaculture is one of the highest contributors of fish production in France, which may result in environmental perturbations caused by organic matter (OM) accumulation under fish farms and impacting natural communities. This study aimed to (1) characterise the environmental conditions at two different fish farms, (2) monitor the response of benthic foraminiferal species to this activity, and (3) assess the accuracy of existing foraminiferal biotic indices. In 2017, sea floor sediment was sampled in transects from two Corsican fish farms for living foraminiferal and sedimentary analyses. Four indices were calculated and compared: exp(H′bc), Foram-AMBI, Foram Stress Index and TSI-Med. A significant increase in total organic carbon (TOC) has been shown, mainly below the fish cages. Communities were characterized by a shift from high density, opportunistic and tolerant species under the cages to lower densities and more sensitive species further away. According to their distribution patterns along the TOC gradient, we propose to update the ecological group classification of seven species to improve Foram-AMBI’s accuracy and sensitivity: Triloculina oblonga and Quinqueloculina lamarckiana to Ecological Group (EG) I; Rosalina bradyi to EGIII; and Bolivina dilatata, Bulimina aculeata and Quinqueloculina stalkeri to EGIV. We recommend prioritising the use of TSI-Med and Foram-AMBI with the updated list to assess ecological quality in coastal waters of the Mediterranean Sea.

Modelling the environmental footprint of sea bream cage aquaculture in relation to spatial stocking design

Aquaculture is one of the fastest growing industries in global food production, which raises the need for adopting holistic planning in the allocation of fish farm locations dedicated to aquaculture in the context of an ecosystem approach. The future development and expansion of aquaculture will strongly depend on the availability of space to develop the industry in a sustainable manner, or in finding ways to reduce the environmental impact at existing locations. This study assesses the possibility of reducing the impact of aquaculture farming by optimizing on the spatial stocking design of three generations of caged fish. Three spatial stocking scenarios were analyzed using simulated numerical experiments. The analysis was performed using emission estimates and by modelling the dispersion and deposition of organic matter on the seabed with concomitant effects on oxygen concentration. Emissions were estimated according to fish growth predictions, energy requirements, body chemical composition, daily meal requirements (industrial feed), and proximate chemical composition of the feed in a sea bream fish farm. The simulation results show that an optimized spatial stocking design of fish cages can significantly reduce the environmental footprint while simultaneously allowing for an increase in annual fish production and optimal utilization of the farming site. Additionally, our findings suggest that carrying capacity of the farming site based only on the annual maximum biomass of harvested fish does not give optimal production estimates and may contribute to underestimating the productive capacity of cage fish farms.

Living (stained) foraminifera in the Lesser Syrtis (Tunisia): influence of pollution and substratum

Foraminifera are protozoans with biomineralized tests that can be successfully used as a low cost monitoring tool to assess the health status of marine environments. Living benthic foraminiferal assemblages can provide essential information on natural and/or anthropogenic stresses and provide baseline conditions for studies on fossil material. Several studies have highlighted the negative impact of phosphate treatment industries along the Gulf of Gabes (Lesser Syrtis, Tunisia) on the marine environment. However, only a few studies, based on living (stained) benthic foraminifera, are presently available to assess environmental and/or ecological conditions in this Gulf. Thirty-eight surface sediment samples were quantitatively investigated to identify the dominant living benthic foraminiferal species and potential pollution-sensitive and stress-tolerant species. One-hundred and sixty-one species were identified, and grouped into seven clusters representing different environments within the Gulf. These groups represent polluted settings (Cluster A and B), polluted environments characterized by physicochemical variability (Cluster C), seagrass meadows and “pristine” sites (Cluster D and E) and the region subjected to major industrial impact (Cluster F). The final outlier Cluster, identified the foraminifera barren and all shallow coastal stations. A SIMPER analysis helped identify species with clear and fast responses to environmental perturbations (Ammonia tepida, Amphistegina lessonii, Brizalina striatula, Bulimina marginata, Buliminella elegantissima, Eggereloides scaber, Peneroplis perutusus, Rosalina macropora, Rosalina villardeboana, Trochammina inflata). A comparison with the measured geochemical parameters (TOC, phosphorus in the sediments and heavy metal concentrations in the seawater) has shown that the benthic foraminiferal assemblages are mainly linked to phosphorus, TOC, As and Cd pollution. We also provide here the first compilation of the identified living species in the Lesser Syrtis, their synonyms and digital images of important species.

Environmental quality assessment of the fish farms' impact in the Monastir Bay (eastern of Tunisia, Central Mediterranean): a benthic foraminiferal perspective

Offshore fish farms have been active inside the Monastir Bay, Hammemet Gulf for over 10 years, but their environmental impact is still unknown. This study focuses on the evaluation of the fish farming activity impact in the Monastir Bay as revealed by geochemical and benthic foraminiferal data. Samples were collected around three fish cages at different water depths. Total organic carbon (TOC) and total phosphate (TP) in the sediment show higher values beneath the fish cages and decrease proportionally with distance from the cages. Living foraminiferal assemblages around fish farms are dominated by stress-tolerant species with higher abundances of Ammonia tepida, Rosalina bradyi, Elphidium crispum, and Peneroplis planatus. On the basis of our results, A. tepida and Quinqueloculina seminula are confirmed to be tolerant to elevated nutriment content, while Ammonia parkinsoniana seems to be more sensitive to organic enrichment. We also test the Foram-AMBI that is revealed to be a very promising tool by which evaluating the ecological quality status of marine sediment. The results of the present study confirm the suitability of living benthic foraminifera as bioindicators of organic enrichment induced by aquaculture activities.

Identifying past petroleum exploration related drill cutting releases and influences on the marine environment and benthic foraminiferal communities, Goliat Field, SW Barents Sea, Norway

The present multiproxy investigation of marine sediment cores aims at: 1) Identifying dispersion of petroleum exploration related drill cutting releases within the Goliat Field, Barents Sea in 2006/07 and 2) Assessing past and present influence of drill cuttings on the marine environment. The cores were recovered 5, 30, 60, 125 and 250m from the drill site in the eastward downstream direction. Downstream dispersion of drill cuttings is evaluated by examining sediment grain size distribution and barium (Ba), heavy metal, total organic carbon and sulphur concentrations. Dispersion of drill cuttings was limited to <125m east from the drill site. Influence of drill cutting releases on the marine environment is assessed via microfaunal analysis of primarily calcareous benthic foraminifera. The findings suggest contemporaneous physical smothering at ≤30m from the drill site, with a natural fauna reestablishing after drilling cessation indicating no long-term effect of drill cutting releases.

Predicting the Ecological Quality Status of Marine Environments from eDNA Metabarcoding Data Using Supervised Machine Learning

Monitoring biodiversity is essential to assess the impacts of increasing anthropogenic activities in marine environments. Traditionally, marine biomonitoring involves the sorting and morphological identification of benthic macro-invertebrates, which is time-consuming and taxonomic-expertise demanding. High-throughput amplicon sequencing of environmental DNA (eDNA metabarcoding) represents a promising alternative for benthic monitoring. However, an important fraction of eDNA sequences remains unassigned or belong to taxa of unknown ecology, which prevent their use for assessing the ecological quality status. Here, we show that supervised machine learning (SML) can be used to build robust predictive models for benthic monitoring, regardless of the taxonomic assignment of eDNA sequences. We tested three SML approaches to assess the environmental impact of marine aquaculture using benthic foraminifera eDNA, a group of unicellular eukaryotes known to be good bioindicators, as features to infer macro-invertebrates based biotic indices. We found similar ecological status as obtained from macro-invertebrates inventories. We argue that SML approaches could overcome and even bypass the cost and time-demanding morpho-taxonomic approaches in future biomonitoring.

Effect of abalone farming on seawater movement and benthic foraminiferal assemblage of Zostera marina in the inner bay of Wando, South Korea

Tidal current survey as well as geochemical and benthic foraminiferal analyses of sediment cores were conducted in an abalone farm and a Zostera bed to understand the degree to which the abalone farm facilities installed along a channel in a shallow sea affect the benthic environment and ecology. In the abalone farm, Ammonia beccarii-Pseudoparrella naraensis-Elphidium somaense-Rosalina globularis-Trochammina hadai and P. naraensis-E. somaense-A. beccarii-T. hadai assemblages appeared owing to an increase in the total nitrogen content from the biodeposits. The Zostera bed consisted of A. beccarii-P. naraensis-Buccella frigida-T. hadai assemblage owing to the gradual expansion of a brackish shallow-water environment by the rapidly decreasing current speed, and it may have flourished. Moreover, the total sulfur, Zn, Cr, and Cu contents in the sediments decreased remarkably more than those of the pre-abalone farming did, caused by the vigorous activity of Zostera marina physiology.

Accurate assessment of the impact of salmon farming on benthic sediment enrichment using foraminiferal metabarcoding

Assessing the environmental impact of salmon farms on benthic systems is traditionally undertaken using biotic indices derived from microscopic analyses of macrobenthic infaunal (MI) communities. In this study, we tested the applicability of using foraminiferal-specific high-throughput sequencing (HTS) metabarcoding for monitoring these habitats. Sediment samples and physico-chemical data were collected along an enrichment gradient radiating out from three Chinook salmon (Oncorhynchus tshawytscha) farms in New Zealand. HTS of environmental DNA and RNA (eDNA/eRNA) resulted in 1,875,300 sequences that clustered into 349 Operational Taxonomic Units. Strong correlations were observed among various biotic indices calculated from MI data and normalized fourth-root transformed HTS data. Correlations were stronger using eRNA compared to eDNA data. Quantile regression spline analyses identified 12 key foraminiferal taxa that have potential to be used as bioindicator species. This study demonstrates the huge potential for using this method for biomonitoring of fish-farming and other marine industrial activities.