Trace element concentrations in reef associated sediments of Koswari Island, Gulf of Mannar biosphere reserve, southeast coast of India

Dietary intake of trace elements from commercially important fish and shellfish of Thoothukudi along the southeast coast of India and implications for human health risk assessment

The concentrations of eight trace elements (chromium, cobalt, copper, zinc, arsenic, cadmium, mercury and lead) in14 commercially important fish and shellfish collected from Thoothukudi along the southeast coast of India was investigated using inductively coupled plasma mass spectrometry in order to assess the health risks associated with their consumption. The concentration of trace elements ranged from 0.001 to 39.5 μg/g. The estimated weekly intake of cadmium in seven fish and shellfish (0.0081-0.0996 mg/kg body weight) were above the provisional tolerable weekly intake set by the Joint FAO/WHO Expert Committee on Food Additives. The risk assessment analysis indicated that there was non- carcinogenic risk upon lifetime consumption of rock crab, C. natator (TTHQ >1) and carcinogenic risks upon lifetime consumption of S. jello, P. semisulcatus, P. sanguinolentus C. natator, Uroteuthis duvaceli, Sepia pharaonis and Cistopus indicus due to cadmium exposure indicating a potential health risk to the exposed consumers.

Metal accumulation and biomineralisation of coastal and mangrove-associated molluscs of Palk Bay, Southeastern India

The present study aimed to determine metal accumulation levels in tissue and biomineralisation in shells of 20 species of molluscs (13 gastropods and 7 bivalves) from Palk Bay, India. In most cases, metal concentrations in the tissues were higher than in the shells of the same species collected from same location, meaning that in many cases biomineralisation factors of metal ratios were <1. The highest biomineralisation factor for Cd was detected in Melampus sincaporensis (3.72 ± 0.1) from the Thondi mangrove, for Pb in Cerithidea cingulata (2.51 ± 0.17) from the Vattanam mangrove, for Cu in Melampus sincaporensis (0.88 ± 0.2) from the Thondi mangrove, and for Zn in Cerithidea cingulata (0.93 ± 0.3) from the Devipattinam mangrove. In most cases, metal concentrations were higher than reported in previous studies but were within the maximum limits stated by national and international regulatory agencies. Variations in the biomineralisation factor of metal ratios among the molluscan species likely stems from variations in bioaccumulation efficiency, selectivity of individual organisms, and availability of metals in the mangrove and coastal environments.

Heavy metal concentrations in the macroalgae, seagrasses, mangroves, and crabs collected from the Tuticorin coast (Hare Island), Gulf of Mannar, South India

This study investigates the concentration of heavy metals in the macroalgae, seagrasses, mangroves, and crabs collected from Hare Island, Gulf of Mannar Marine Biosphere Reserve. The concentration of heavy metals ranged between 0.06 (Hg)-259 (Fe) μg/g in macroalgae, 0.09 (Pb)-377 (Fe) μg/g in seagrasses, 0.112 (Cd)-122 (Fe) μg/g in mangroves, and 0.11 (Cd) -240 (Fe) μg/g in crabs. The levels of heavy metals in the analyzed samples were found below the maximum residual limits (MRLs) prescribed by various National and International agencies. The result suggests that exposure to the analyzed metals through macroalgae consumption does not cause potential health risks to consumers (target hazard quotient (THQ), estimated exposure dose (EED), and hazard index (HI) <1). Hence, this study concludes that macroalgae that grow in the Gulf of Mannar regions are safe for human consumption and are suitable to prepare food supplements and bioceutical products.

Heavy metal concentration in reef-associated surface sediments, Hare Island, Gulf of Mannar Marine Biosphere Reserve (southeast coast of India): The first report on pollution load and biological hazard assessment using geochemical normalization factors and hazard indices

In this study, reef-associated surface sediment samples were collected from Hare Island in the Gulf of Mannar Marine Biosphere Reserve, Bay of Bengal and analyzed for heavy metal concentration. The sediment quality was evaluated based on the geochemical, biological, and ecological hazard indices. The mean concentration of heavy metals in the sediments ranged from 0.02 (Cd) to 26,262.87 mg/kg (Fe). Except for Cd and Hg, all other elements were found to be below the sediment quality guidelines and contamination level. The biological and ecological hazard (BEHI) revealed that most sediment samples (80%) fell under the low-risk category with 9% probability of toxicity to the marine flora and fauna. The overall contamination level of heavy metals in Hare Island suggested that the sediment could be grouped under low-risk category. Hence, this study recommends the need for a routine monitoring program in this region to maintain a clean and sustainable ecosystem in future.

Microplastic and heavy metal distributions in an Indian coral reef ecosystem

The current study focuses on the occurrence and characteristics of microplastics (MPs) and spatial distribution and pollution status of heavy metals in the water and sediments of the coral reef ecosystems associated with the Tuticorin and Vembar groups of islands in the Gulf of Mannar, southeast India. Mean abundance of MPs varies from 60 ± 54 to 126.6 ± 97 items/L in water and from 50 ± 29 to 103.8 ± 87 items/kg in sediment. Water and sediment samples from the Tuticorin islands contain higher MP concentrations than the Vembar islands. The highest MP were observed in the mainland samples, while MP distributions in the shoreward direction i.e. towards the islands closely reflect those of the mainland (p < 0.05). Polyethylene is the most common polymer, with fibers (1-3 mm) being the most abundant form in water and fragments (3-5 mm) being the most abundant in sediment. Pollution indices such as enrichment and contamination factors indicate moderate contamination of sediments by Zn, Hg, Cd, Pb and Ni. Heavy metal associated with MPs are greater than those in sediments, and this indicates that MP may be a source of metal pollution or that metals from the sediment preferentially partition to MPs. SEM analysis highlights the presence of cracks, protrusions and depositions on the surface of many MPs, indicating partial degradation. EDAX frequently showed the presence of Zn, Cd, Pb, Ni and Fe associated with MP surfaces. This study offers an insight into the level of MPs and associated elements that filter feeding corals in the region are exposed to current.

Geochemical Composition of the Lomé Lagoon Sediments, Togo: Seasonal and Spatial Variations of Major, Trace and Rare Earth Element Concentrations

The concentrations of major, trace (TE), and rare earth (REE) elements and their seasonal and spatial distribution were studied on the fine fraction (<63 µm) of the sediments of the Lomé lagoons (West Lake, East Lake, and Lake Bè). The sediments were collected on a total of nine sampling sites (three per Lake) during two campaigns (dry season and rainy season). The quality of the sediments was assessed on the basis of the enrichment factor (EF) and the labile or non-residual fraction (NRF) in relation to the values recommended for the quality of the sediments (Sediment Quality Guidelines, SQG). The distribution of rare earth elements shows enrichments in light rare earths superior to those of heavy rare earth elements during any season. Positive Ce anomalies are less noticeable and less variable between seasons than Eu anomalies. La/Yb ratios are positively correlated with the percentage of Al and Fe oxides and with the percentage of fine fractions. The main bearing phases of rare earth elements are, therefore, Al and Fe oxides and the finest fractions of the sediments. The concentrations of trace elements vary little, according to the seasons, but show strong variations from one element to another. The degrees of enrichment obtained are moderate for Bi, Cr, Ga, Mo, Pb, Sn, and Zn (1.5 < EF < 5) to significant for As, Cd, and Sb (5 < EF < 20) for all sites of Lake Bè. For the sites of West Lake, the degrees of enrichment obtained are moderate for As, Cd, Cu, Mo, and Pb (1.5 < EF < 5) to a significance for As, Bi, Cd, Pb, Sb, Sn, and Zn (5 < EF < 20). Only the East Lake sites show high degrees of enrichment for elements such as Sb and Sn (20 < EF < 40). Trace elements (TE) such as As, Cd, Cu, and Ni have total concentrations within the range of variation of the SQG concentrations (particularly Probable Effect Level (PEL) and Effect Range Median (ERM)), whereas Cr, Pb, and Zn total concentrations are higher. The ranking of priority sites with respect to the sediment contamination is determined according to ERM and PEL quotients in relation to the probability of toxicity for benthic organisms. For almost all the sites, the priority is lowest to medium-low with regard to As, Cd, and Cu and medium-high (Cr and Ni) to highest (Pb and Zn), particularly for the East and West Lakes. Moreover, the NRF can represent significant percentages of the total TE concentrations: 5% to 15% for As, Bi, Ni, V, Mo, and Sc, 15% to 25% for Co, Cu, and Sr, 25% to 40% for Pb and Zn and, lastly, 47% to 55% for Cd.

Heavy metals accumulation in seagrasses collected from Palk Bay, South-eastern India

Metals such as Cd, Pb, Cu and Zn were analysed in five seagrass species from five locations of the Palk Bay coast of south-eastern India. The maximum Cd concentration (2.83 ± 0.08 μg g^-1) was recorded in Syringodium isoetifolium on the Mallipattinam coast in the post-monsoon season, and the Cu (29.54 ± 1.03 μg g^-1) in Enhalus acoroides of the Thondi coast during monsoon season. The maximum concentrations of Pb (3.12 ± 0.14 μg g^-1) and Zn (52.66 ± 0.88 μg g^-1) were observed in S. isoetifolium and Cymodoceae rotundata on the Devipattinam and Karangadu coasts, respectively, during the monsoon season. The metal concentrations obtained in different seagrass species varied significantly among species, and no clear monsoon season had a clear effect on the accumulation of heavy metals in the investigated seagrass species. S. isoetifolium has higher capacity for Cd and Pb accumulation than other tested seagrass species.

Spatial variation of trace element concentration and contamination assessment in the coral reef sediments of Lakshadweep Archipelago, Indian Ocean

Surface sediments were collected from the shore and lagoons of Kavaratti, Kadmat and Agatti islands of Lakshadweep Archipelago and analysed for trace element concentration. The sediment contamination was assessed on the basis of geochemical, biological hazard and ecological risk indices. Except Cd and Pb, all the other trace elements selected for the study were below the contamination level. Compared to Kadmat, Kavaratti and Agatti were more polluted and the pollution was pronounced in lagoons than shore. Population pressure, untreated sewage, diesel based power generation, shipping and tourism activities contribute to sediment contamination. Statistical analysis revealed the association of trace elements with sedimentary characteristics due to anthropogenic sources.

A preliminary study on coastal debris in Nallathanni Island, Gulf of Mannar Biosphere Reserve, Southeast coast of India

Nine sampling stations were fixed to carry out the preliminary investigation on coastal debris from Nallathanni island, Gulf of Mannar Biosphere Reserve, Southeast coast of India. The coastal debris were separated and identified using hand picking, visual identification and microscopic studies. The coastal areas of the study region were less dominated by micro plastic contamination. The coastal debris was dominated by polyethylene bottles and fibrous fishnet materials. The distribution of the coastal debris along the coastal region is chiefly controlled by winnowing action of sea waves and Aeolian action along the berm region.

A baseline study on the concentration of trace elements in the surface sediments off Southwest coast of Tamil Nadu, India

Forty two surface sediment samples were collected in order to document baseline elemental concentration along the Southwest coast of Tamil Nadu, India. The elements detected were Manganese (Mn), Zinc (Zn), Iron (Fe), Copper (Cu), Nickel (Ni) and Lead (Pb). The concentration of Fe and Mn was primarily controlled by the riverine input. The source of Pb and Zn is attributed to leaded petrol and anti-biofouling paints. The calculated index (EF, Igeo and CF) suggests that the sediments of the study area are significantly enriched with all elements except Pb. The contamination factor showed the order of Mn>Zn>Fe>Cu>Ni>Pb. The sediment pollution index (SPI) revealed that the sediments belonged to low polluted to dangerous category. The correlation matrix and dendrogram showed that the elemental distribution was chiefly controlled by riverine input as well as anthropogenic activity in the coast.