This study reports the first evidence of the occurrence of perfluoroalkyl acids (PFAAs) in commonly consumed seafood from the coastal area of Bangladesh. Fifteen target PFAAs in 48 seafood samples (5 finfish and 2 shellfish species) were measured by HPLC-MS/MS. The results were comparable with other studies worldwide, particularly from China, Spain, Sweden, and USA. The majority of monitored PFAAs did not show clear seasonal variation. However, seafood from the southeast area (Coxs Bazar and Chittagong) showed relatively higher levels of PFAAs. Moreover, the dietary exposure assessment revealed that the daily intakes of PFAAs via seafood consumption were far less than the health-based guidelines, indicating low health risk for the Bangladeshi coastal residents."

The combined effects of emerging pollutants and ocean acidification (OA) on marine organisms and marine ecosystems have attracted increasing attention. However, the combined effects of tralopyril and OA on marine organisms and marine ecosystems remain unclear. In this study, Crassostrea gigas (C. gigas) were exposed to tralopyril (1 μg/L) and/or OA (PH = 7.7) for 21 days and a 14-day recovery acclimation. To investigate the stress response and potential molecular mechanisms of C. gigas to OA and tralopyril exposure alone or in combination, as well as the effects of OA and/or tralopyril on bivalve biomineralization and marine carbon cycling. The results showed that the combined toxicity was between that of acidification and tralopyril alone. Single or combined exposure activated the general stress defense responses of C. gigas mantle, affected energy metabolism and biomineralization of the organism and the carbon cycle of the marine ecosystem. Moreover, acidification-induced and tralopyril-induced toxicity showed potential recoverability at molecular and biochemical levels. This study provides a new perspective on the molecular mechanisms of tralopyril toxicity to bivalve shellfish and reveals the potential role of tralopyril and OA on marine carbon cycling.

Harmful algal blooms (HABs) are recurrent in the NW Patagonia fjords system and their frequency has increased over the last few decades. Outbreaks of HAB species such as Alexandrium catenella, a causal agent of paralytic shellfish poisoning, and Protoceratium reticulatum, a yessotoxins producer, have raised considerable concern due to their adverse socioeconomic consequences. Monitoring programs have mainly focused on their planktonic stages, but since these species produce benthic resting cysts, the factors influencing cyst distributions are increasingly gaining recognition as potentially important to HAB recurrence in some regions. Still, a holistic understanding of the physico-chemical conditions influencing cyst distribution in this region is lacking, especially as it relates to seasonal changes in drivers of cyst distributions, as the characteristics that favor cyst preservation in the sediment may change through the seasons. In this study, we analyzed the physico–chemical properties of the sediment (temperature, pH, redox potential) and measured the bottom dissolved oxygen levels in a “hotspot” area of southern Chile, sampling during the spring and summer as well as the fall and winter, to determine the role these factors may play as modulators of dinoflagellate cyst distribution, and specifically for the cysts of A. catenella and P. reticulatum. A permutational analysis of variance (PERMANOVA) showed the significant effect of sediment redox conditions in explaining the differences in the cyst assemblages between spring-summer and fall-winter periods (seasonality). In a generalized linear model (GLM), sediment redox potential and pH were associated with the highest abundances of A. catenella resting cysts in the spring-summer, however it was sediment temperature that most explained the distribution of A. catenella in the fall-winter. For P. reticulatum, only spring-summer sediment redox potential and temperature explained the variation in cyst abundances. The implications of environmental (physico-chemical) seasonality for the resting cysts dynamics of both species are discussed.

Freshwater cyanobacteria produce highly toxic secondary metabolites, which can be transported downstream by rivers and waterways into the sea. Estuarine and coastal aquaculture sites exposed to toxic cyanobacteria raise concerns that shellfish may accumulate and transfer cyanotoxins in the food web. This study aims to describe the competitive pattern of uptake and depuration of a wide range of microcystins (MC-LR, MC-LF, MC-LW, MC-LY, [Asp3]-MC-LR/[Dha7]-MC-LR, MC-HilR) and nodularins (NOD cyclic and linear) within the common blue mussel Mytilus edulis exposed to a combined culture of Microcystis aeruginosa and Nodularia spumigena into the coastal environment.Different distribution profiles of MCs/NODs in the experimental system were observed. The majority of MCs/NODs were present intracellularly which is representative of healthy cyanobacterial cultures, with MC-LR and NOD the most abundant analogues. Higher removal rate was observed for NOD (≈96%) compared to MCs (≈50%) from the water phase. Accumulation of toxins in M. edulis was fast, reaching up to 3.4 μg/g shellfish tissue four days after the end of the 3-days exposure period, with NOD (1.72 μg/g) and MC-LR (0.74 μg/g) as the dominant toxins, followed by MC-LF (0.35 μg/g) and MC-LW (0.31 μg/g). Following the end of the exposure period depuration was incomplete after 27 days (0.49 μg/g of MCs/NODs). MCs/NODs were also present in faecal material and extrapallial fluid after 24 h of exposure with MCs the main contributors to the total cyanotoxin load in faecal material and NOD in the extrapallial fluid. Maximum concentration of MCs/NODs accumulated in a typical portion of mussels (20 mussels, ≈4 g each) was beyond greater the acute, seasonal and lifetime tolerable daily intake. Even after 27 days of depuration, consuming mussels harvested during even short term harmful algae blooms in close proximity to shellfish beds might carry a high health risk, highlighting the need for testing.

Gymnodimine A has been found in mollusks obtained along the whole northern coast of Spain from April 2017 to December 2019. This is the first time that this toxin is detected in mollusks from the Atlantic coast of Europe. The prevalence of the toxin was, in general, low, being detected on average in approximately 6% of the obtained samples (122 out of 1900). The concentrations recorded were also, in general, low, with a median of 1.3 μg kg⁻¹, and a maximum value of 23.93 μg kg⁻¹. The maxima of prevalence and concentration were not geographically coincident, taking place the first at the easternmost part of the sampled area and the second at the westernmost part. In most cases (>94%), gymnodimine A and 13-desmethyl spirolide C were concurrently detected, suggesting that Alexandrium ostenfeldii could be the responsible producer species. The existence of cases in which gymnodimine A was detected alone suggests also that a Karenia species could also be involved. The geographical heterogeneity of the distribution suggests that blooms of the producer species are mostly local. Not all bivalves are equally affected, clams being less affected than mussels, oysters, and razor clams. Due to their relatively low toxicity, and their low prevalence and concentration, it seems that these toxins do not pose an important risk for the mollusk consumers in the area.

A systematic investigation into bioaccessible heavy metals in shellfish Crassostrea ariakensis, Chlamys farreri, and Sinonovacula constricta from coastal cities Shenzhen, Zhoushan, Qingdao, and Dandong was carried out to assess the potential health risk to residents in coastal regions in China. The bioaccessible fractions of heavy metals were (μg‧g⁻¹): Zn (0.63–15.01), Cu (0.10–12.91), Cd (0.01–0.64), As (0.11–0.33), Cr (0.07–0.12), Pb (0.01–0.03). The bioaccessibilities of heavy metals were Cr 61.86%, inorganic As (iAs) 60.44%, Pb 55.74%, Cu 46.83%, Zn 28.16%, and Cd 24.99%. As for child and adult, the bioaccessibility-corrected estimated daily intakes were acceptable and the non-carcinogenic risks posed by heavy metals were not obvious. The carcinogenic risks posed by bioaccessible heavy metals at the fifth percentile were 10-fold higher than the acceptable level (10⁻⁴), with iAs and Cd to be the major contributors, regardless of child or adult. The probabilistic estimation showed the low risk of shellfish consumption, which was verified by higher values of maximum allowable consumption rate and monthly meals at the 95 percentile; while some control of consumption rate and monthly meals was necessary for reducing heavy metal exposure of most shellfish samples, except for the safe consumption of S. constricta for both child and adult in Qingdao and Shenzhen, China.

Metal release into the environment from anthropogenic activities may endanger ecosystems and human health. However, identifying and quantifying anthropogenic metal bioaccumulation in organisms remain a challenging task. In this work, we assess Cu isotopes in Pacific oysters (C. gigas) as a new tool for monitoring anthropogenic Cu bioaccumulation into marine environments. Arcachon Bay was taken as a natural laboratory due to its increasing contamination by Cu, and its relevance as a prominent shellfish production area. Here, we transplanted 18-month old oysters reared in an oceanic neighbor area into two Arcachon Bay mariculture sites under different exposure levels to continental Cu inputs. At the end of their 12-month long transplantation period, the oysters’ Cu body burdens had increased, and was shifted toward more positive δ⁶⁵Cu values. The gradient of Cu isotope compositions observed for oysters sampling stations was consistent with relative geographic distance and exposure intensities to unknown continental Cu sources. A binary isotope mixing model based on experimental data allowed to estimate the Cu continental fraction bioaccumulated in the transplanted oysters. The positive δ⁶⁵Cu values and high bioaccumulated levels of Cu in transplanted oysters support that continental emissions are dominantly anthropogenic. However, identifying specific pollutant coastal source remained unelucidated mostly due to their broader and overlapping isotope signatures and potential post-depositional Cu isotope fractionation processes. Further investigations on isotope fractionation of Cu-based compounds in an aqueous medium may improve Cu source discrimination. Thus, using Cu as an example, this work combines for the first time a well-known caged bivalve approach with metal stable isotope techniques for monitoring and quantifying the bioaccumulation of anthropogenic metal into marine environments. Also, it states the main challenges to pinpoint specific coastal anthropogenic sources utilizing this approach and provides the perspectives for further studies to overcome them.

Among the seafood used globally, shellfish consumption is in great demand. The utilization of these shellfish such as prawn/shrimp has opened a new market for the utilization of the shellfish wastes. Considering the trends on the production of wealth from wastes, shrimp shell wastes seem an important resource for the generation of high value products when processed on the principles of a biorefinery. In recent years, various chemical strategies have been tried to valorize the shrimp shell wastes, which required harsh chemicals such as HCl and NaOH for demineralization (DM) and deproteination (DP) of the shrimp wastes. Disposal of chemicals by the chitin and chitosan industries into the aquatic bodies pose harm to the aquatic flora and fauna. Thus, there has been intensive efforts to develop safe and sustainable technologies for the management of shrimp shell wastes. This review provides an insight about environmentally-friendly methods along with biological methods to valorize the shrimp waste compared to the strategies employing concentrated chemicals. The main objective of this review article is to explain the utilization shrimp shell wastes in a productive manner such that it would be offer environment and economic sustainability. The application of valorized by-products developed from the shrimp shell wastes and physical methods to improve the pretreatment process of shellfish wastes for valorization are also highlighted in this paper.

Microplastics debris (<5 mm) are increasingly abundant in the marine environment, therefore, potentially becoming a growing threat for different marine organisms. Through aquatic animals, these can enter in the human food chain, and can be perceived as a risk for consumers’ health.Different studies report the presence of particles in marketable shellfish including the world wide commercially grown Pacific oyster Magallana gigas (Thunberg, 1793). The aim of this study is to examine the potential risk of microplastics entering in the human food chain through this shellfish species, investigating the dynamics of the uptake, egestion (faeces) and rejection (pseudofaeces) of microplastics in Pacific oysters under controlled conditions.M. gigas collected from a farm in the San Teodoro lagoon (Italy), were exposed to 60 fluorescent orange polystyrene particles L⁻¹ of known sizes (100, 250 and 500 μm). The uptake of each particle size was 19.4 ± 1.1%, 19.4 ± 2% and 12.9 ± 2% respectively. After exposure M. gigas were left to depurate for 72 h, during which 84.6 ± 2% of the particles taken up were released whilst 15.4 ± 2% were retained inside the shell cavity. No microplastic particles were found in the animals’ soft tissues.The results of this study, suggest that depuration is an effective method to reduce presence of large microplastic particles, in the size range 100–500 μm, in M. gigas. Importantly, the data suggests that the burden that could theoretically be up taken by consumers from these shellfish is negligible when compared to other routes.

Harmful microalgal blooms are a threat to aquatic organisms, ecosystems and human health. Toxic dinoflagellates of the genus Alexandrium are known to produce paralytic shellfish toxins and to release bioactive extracellular compounds (BECs) with potent cytotoxic, hemolytic, ichtyotoxic and allelopathic activity. Negative allelochemical interactions refer to the chemicals that are released by the genus Alexandrium and that induce adverse effects on the physiology of co-occurring protists and predators. Releasing BECs gives the donor a competitive advantage that may help to form dense toxic blooms of phytoplankton. However BECs released by Alexandrium minutum are uncharacterized and it is impossible to quantify them using classical chemical methods. Allelochemical interactions are usually quantified through population growth inhibition or lytic-activity based bioassays using a secondary target organism. However these bioassays require time (for growth or microalgal counts) and/or are based on lethal effects. The use of pulse amplitude modulation (PAM) fluorometry has been widely used to assess the impact of environmental stressors on phytoplankton but rarely for allelochemical interactions. Here we evaluated the use of PAM and propose a rapid chlorophyll fluorescence based bioassay to quantify allelochemical BECs released from Alexandrium minutum. We used the ubiquitous diatom Chaetoceros muelleri as a target species. The bioassay, based on sub-lethal effects, quantifies allelochemical activity from different samples (filtrates, extracts in seawater) within a short period of time (2 h). This rapid bioassay will help investigate the role of allelochemical interactions in Alexandrium bloom establishment. It will also further our understanding of the potential relationship between allelochemical activities and other cytotoxic activities from BECs. While this bioassay was developed for the species A. minutum, it may be applicable to other species producing allelochemicals and may provide further insights into the role and impact of allelochemical interactions in forming dense algal blooms and structuring marine ecosystems.