Wild Mussels Research Articles

Blue mussel (Mytilus edulis)-A bioindicator of marine water contamination by protozoa: Laboratory and in situ approaches.

The protozoan parasites Cryptosporidium spp., Giardia duodenalis and Toxoplasma gondii are identified as public health priorities and are present in a wide variety of environments including the marine ecosystem. The objective of this study was to demonstrate that the marine bivalve blue mussel (Mytilus edulis) can be used as a tool to monitor the contamination of marine waters by the three protozoa over time. In order to achieve a proof of concept, mussels were exposed to three concentrations of G. duodenalis cysts and Cryptosporidium parvum/T. gondii oocysts for 21days, followed by 21days of depuration in clear water. Then, natural contamination by these protozoa was sought for in wild marine blue mussels along the northwest coast of France to validate their relevance as bioindicators in the field. Our results highlighted that: (a) blue mussels bioaccumulated the parasites for 21days, according to the conditions of exposure, and parasites could still be detected during the depuration period (until 21days); (b) the percentage of protozoa-positive M. edulis varied under the degree of protozoan contamination in water; (c) mussel samples from eight out of nine in situ sites were positive for at least one of the protozoa. The blue mussel M. edulis can bioaccumulate protozoan parasites over long time periods, according to the degree of contamination of waters they are inhabiting, and can highlight recent but also past contaminations (at least 21days). Mytilus edulis is a relevant bioaccumulators of protozoan (oo)cysts in laboratory and field conditions, hence its potential use for monitoring parasite contamination in marine waters.

Investigation of microplastics in edible wild mussels from İzmir Bay (Aegean Sea, Western Turkey): A risk assessment for the consumers

The presence of microplastics (MPs) was determined in Mediterranean mussel (Mytilus galloprovincialis Lamarck, 1819) and grooved carpet shell (Ruditapes decussatus Linnaeus, 1758) together with water samples from in İzmir Bay (Aegean Sea, Western Turkey). A total of 895 MPs from Karşıyaka (Station 1), and 787 MPs from Gülbahçe (Station 2) were detected in 60 mussel samples, giving a total content of 1682 MPs. In water samples, a total of 545 MPs were detected in samples from Station 1 and 1287 MPs in samples from Station 2 (1832 MPs total). The amount of MPs in water samples was less in Station 1 than in Station 2. This difference is probably caused by Çiğli Wastewater Treatment Plant (WWTP) located near Station 1. Public health risk assessment on the consumption of the species M. galloprovincialis revealed that 70.82 items person−1 year−1 MPs through this species could enter consumers' digestive systems.

The influence of natural vs anthropogenic factors on trace metal(loid) levels in the Mussel Watch programme: Two decades of monitoring in the Spanish Mediterranean sea

The spatial distribution and temporal trends of trace metals (i.e. Cd, Cu, Hg, Pb and Zn) and a metalloid (i.e. As) along the Spanish Mediterranean coast from 1993 to 2013 are presented with a new estimation of their background levels monitored using wild mussels. Over a 20 years period, yearly mussel monitoring was undertaken with a rigorous field sampling protocol using 3 pooled samples strategy (3 x n = 80, with 8 mussels in the 3.0 to 3.9 size categories at each site), obtained in the pre-spawning period (May–June) to minimize biological factors and seasonal variability, which is a fundamental element of the international programme. Spatial distribution was characterized every 5 years and temporal trends were determined in 11 locations. The main aims of the present long term study are to evaluate the environmental status of different coastal locations regarding trace metal levels and follow the evolution of these levels over time after the implementation of regulatory measures. Regarding spatial distribution, the highest values for Cd, Cu, Hg and Pb were found close to known highly anthopogenic cities or shipyard areas. However, As and Zn did not strictly follow this pattern, showing natural increased concentrations in the Levantine Balearic and Strait of Gibraltar-Alboran Sea demarcations respectively. These distributions are associated with the conjunction of two geological formation inputs (Massif Central in France and Iberian Pyritic Belt in Spain) and the oceanographic conditions in the adjacent coastal area. In the case of temporal trends, metal concentrations decreased significantly over time in most stations, confirming the effectiveness of the regulatory measures and prohibitions established under European legislation. Concentrations of Pb were above the established thresholds for human consumption in only 12–14% of the sampling areas. With the information obtained for this study, we estimate background concentrations and propose new Background Assesment Criteria (BAC) for the Spanish Mediterranean coast as a threshold criterion: 1.62 mg/kg d.w. for Cd, 8.75 mg/kg d.w. for Cu, 0.202 mg/kg d.w. for Hg and 2.83 mg/kg d.w. for Pb.Exceptions should exist for As and Zn, for which there should be different levels in each demarcation, due to the geological, hydrological and oceanographic peculiarities of the Spanish coast. For the Levantine-Balearic demarcation, the proposed background concentrations are 117 mg/kg d.w. for As and 200 mg/kg d.w. for Zn., whereas in the Strait of Gibraltar-Alboran Sea demarcation, they are 27.5 mg/kg d.w. for As, and 471 mg/kg d.w. for Zn. This work demonstrates the vital importance of defining the background levels of metal(loid)s at a regional or subregional level because, for areas not affected by anthropogenic causes which have high values as the result of natural processes, this would avoid the risk of constantly surpassing the levels proposed in directives.

Vibrio spp. in Wild and Farmed Mytilus galloprovincialis along the Algerian Mediterranean Coast: Evidence of V. cholerae 01 Serotype Ogawa

ABSTRACT Two hundred and eighty samples of wild and farmed Mytilus galloprovincialis, harvested along the Algerian Mediterranean coast, were processed for the occurrence of Vibrio spp. The mussels were sampled monthly in 2018, in conjunction with the Algerian cholera outbreak that occurred in August. Overall, 33 strains of V. cholerae and 18 strains of V. fluvialis were isolated from 34 wild mussels sampled between July and September. A strain of V. cholerae O1 serotype Ogawa was found in a wild sample of mussels collected after the cholera outbreak. The results confirm the role of mussels as vector for V. cholerae.

Adaptive Differences in Gene Expression in Farm-Impacted Seedbeds of the Native Blue Mussel Mytilus chilensis.

The study of adaptive population differences is relevant for evolutionary biology, as it evidences the power of selective local forces relative to gene flow in maintaining adaptive phenotypes and their underlying genetic determinants. However, human-mediated hybridization through habitat translocations, a common and recurrent aquaculture practice where hybrids could eventually replace local genotypes, risk populations’ ability to cope with perturbations. The endemic marine mussel Mytilus chilensis supports a booming farming industry in the inner sea of Chiloé Island, southern Chile, which entirely relies on artificially collected seeds from natural beds that are translocated to ecologically different fattening centers. A matter of concern is how farm-impacted seedbeds will potentially cope with environmental shifts and anthropogenic perturbations. This study provides the first de novo transcriptome of M. chilensis; assembled from tissue samples of mantles and gills of individuals collected in ecologically different farm-impacted seedbeds, Cochamó (41°S) and Yaldad (43°S). Both locations and tissue samples differentially expressed transcripts (DETs) in candidate adaptive genes controlling multiple fitness traits, involved with metabolism, genetic and environmental information processing, and cellular processes. From 189,743 consensus contigs assembled: 1,716 (Bonferroni pvalue ≤ 0.05) were DETs detected in different tissues of samples from different locations, 210 of them (fold change ≥ | 100|) in the same tissue of samples from a different location, and 665 (fold change ≥ | 4|) regardless of the tissue in samples from a different location. Site-specific DETs in Cochamó (169) and Yaldad (150) in candidate genes controlling tolerance to temperature and salinity shifts, and biomineralization exhibit a high number of nucleotide genetic variants with regular occurrence (frequency > 99%). This novel M. chilensis transcriptome should help assessing and monitoring the impact of translocations in wild and farm-impacted mussel beds in Chiloé Island. At the same time, it would help designing effective managing practices for conservation, and translocation traceability.

A Histopathological–Biochemical Health Assessment of Blue Mussel Mytilus edulis

Aquaculture of the blue mussel Mytilus edulis in the Gulf of Maine is a growing industry at a time when wild mussel populations are threatened by a rapidly changing ocean. Intertidal mussel beds have largely disappeared in the region raising concerns over the long-term viability of mussel farming. Histology and lipid fatty acid analysis were used to assess gametogenesis, energy investment, and pathology of farmed mussels collected twice monthly for three years in Casco Bay, ME. Energy investment in reproduction and storage differed significantly between years, suggesting interannual variability. Wet weight of fatty acids such as DHA and EPA corresponded to pre-spawning periods, when gonad tissue was most abundant. Overall, pathology assessment showed low levels of common pathogens, parasites, and cellular abnormalities. The survey did, however, reveal high levels of oocyte atresia, a probable indicator of physiological or environmental stress from unfavorable spawning conditions. In addition, the presence of the potentially damaging digenetic trematode Proctoeces maculatus was documented using histology, marking the northernmost detection in the Northwest Atlantic and a likely climate-driven range expansion. These trends may signal a challenging future for blue mussels in the Gulf of Maine. Forward-looking farm mitigation practices informed by these results should be developed to ensure future sustainability of this industry.

Organochlorine compounds and polycyclic aromatic hydrocarbons in mussels from Ria de Vigo (the Northern Spanish coast). Current levels and long-term trends (2010–2019). Relationship with human pressures

OCs (organochlorine compounds), such as PCBs (polychlorinated biphenyls) and OCPs (organochlorine pesticides), and PAHs (polycyclic aromatic hydrocarbons) were determined in wild and raft mussels collected in several stations from Ría de Vigo during the period 2010–2019. The concentration levels of ΣPCBs ΣDDs (sum of pp’-DDE and pp’-DDD metabolites) and ΣPAHs ranged from 22.1, 2.63 and 7.55 ng g−1 to 58.0, 6.89 and 25.2 ng g−1 dry weight, respectively. The concentrations of isomers of PCBs in mussel were in the order hexachlorobiphenyls > pentachlorobiphenyls > tetrachlorobiphenyls > trichlorobiphenyls. PCBs 153 and 138 were the most abundant in all samples. Pp’-DDE was the predominant metabolite (70.8% of ΣDDs). The main PAHs in decreasing order of abundance were CHR > BbF > BaA > IcdP. Three biological parameters: lipid content, shell length and condition index have also been investigated. Univariate techniques confirmed that levels of many compounds presented significant relation (p<0.05) with two of the biological parameters (shell length and condition index). In the case of lipid content, only PCB180 congener was significantly related. Multivariate techniques of data exploration such as Principal Component Analysis (PCA) showed that spatial distribution of PCBs, OCPs and PAHs levels appeared in the studied samples and was justified by local human pressures. Temporal trends (linear regressions) showed a decrease, mainly of OCs levels, along the period 2010–2019.

Trace elements risk assessment for consumption of wild mussels along South Africa coastline

The study aimed to contribute to the scarce data on concentrations in the soft tissue of wild mussels growing in coastal cities of South Africa. The intake of 26 micro and macroelements was estimated. The mass fractions of sample sets from 8 sites along the South African coast from the West (Port Nolloth) to the East (Durban) were studied by neutron activation analysis at the Joint Institute for Nuclear Research (Russia). The following elements were identified as potentially hazardous due to high consumption risks: Al, Cr, Co, Zn, As, and I at stations in the Cape Town area (Waterfront, Hout Bay) and Durban. The mean concentrations of these elements among all individuals were 208, 0.8, 0.46, 60, 2.6, and 11 ppm of wet weight, respectively. In the studied mussels, the concentrations of Cr, Zn, As, and Se (ranging between 0.2−2.8, 14–290, 1.6−4.6, and 0.31−2.4 ppm of wet weight, respectively) exceeded maximum permissible levels for fish products. The weekly consumption of more than 250 g of fresh mussels per person could increase the risk for human health by potential intake of such elements as Al, As, and I.

Occurence and Variability of Domoic Acid in Mussel (Mytilus galloprovincialis) Samples from the Golden Horn Estuary, Sea of Marmara (Turkey).

The occurrence and variability of domoic acid (DA) levels in wild Mytilus galloprovincialis samples, compared with the Pseudo-nitzschia spp. abundance and particulate DA (pDA) concentrations in relation to the environmental changes in the Golden Horn Estuary, Turkey from October 2018 to September 2019. Biotoxin analysis were performed by high-performance liquid chromatography with diode-array detection (HPLC-DAD). DA concentrations in particulate matter (pDA) and mussel samples were found between 0.090-0.685µg L-1 and 0.905-2.413µgg-1, respectively. Accumulation of DA in wild mussel samples could be the result of the increasing tendency of P.nitzschia spp. abundances between April and May. Maximum DA levels were detected in particulate matter when the salinity was measured as the lowest in May. Thus, it can be said that the DA production was driven by the significant salinity decrease in the GHE. This is the first attempt regarding the presence of DA in M. galloprovincialis samples collected from Turkish coasts.

Salt-Laden Winter Runoff and Freshwater Mussels; Assessing the Effect on Early Life Stages in the Laboratory and Wild Mussel Populations in Receiving Waters

The widespread use of road salt for winter road maintenance has led to an increase in the salinity of surface water in many seasonally cold areas. Freshwater mussels have a heightened sensitivity to salt, which is a concern, because many Canadian mussel species at risk have ranges limited to southern Ontario, Canada’s most road-dense region. This study examined the effect of winter road runoff on freshwater mussels. The impact of two bridges that span mussel habitat in the Thames River watershed (Ontario, Canada), the second most species-rich watershed for mussels in Canada, were studied. During a winter melt event, bridge runoff, as well as creek surface water surrounding the bridges were collected. Chloride concentrations in samples from bridge deck and tile drains varied (99–8250 mg/L). In general, survival of Lampsilis fasciola glochidia exposed to those samples reflected chloride levels (e.g. 84% at 99 mg/L; 0% at 8250 mg/L), although potassium (60 mg/L) may have at least contributed to toxicity in one sample. Serial dilution exposures with the two most toxic runoff samples revealed 48-h glochidia EC50s of 44% (McGregor Creek Tile Drain) and 26% (Baptiste Creek Deck Drain). During the melt event, the chloride concentrations in creek surface waters downstream of the bridges ranged from 69 to 179 mg Cl−/L; effects on glochidia (viability 77–91%) exposed to those waters was minimal. There were no live mussels surrounding one bridge (Baptiste Creek), likely due to poor habitat. At the other targeted bridge (McGregor Creek), fewer mussels were found close (< 100 m up- or downstream) to the bridge than further (> 200 m) away. However, other contributing factors, including agriculture, were present at both study areas.

Considering the use of subadult and juvenile mussels for mussel reef restoration

Widespread resource extraction and habitat degradation have severely reduced functionally important subtidal mussel reefs globally. While methods for restoring oyster reefs are becoming increasingly well‐established, the development of techniques for the effective restoration of mussel reefs remain in their infancy and face biological and logistical challenges. This study investigated the potential use of subadult and juvenile green‐lipped mussels (Perna canaliculus) for mussel reef restoration with the aim of understanding factors related to subadult and juvenile mussel survival after transfer to the seafloor. Small‐scale (m2) field experiments were conducted subtidally in a New Zealand harbor to assess subadult and juvenile mussel survival after translocation to soft‐sediment seafloor, the efficacy of biodegradable substrate to support reef development, and whether juvenile mussel survival was related to changes in seeding density. Results demonstrated survival of cultured subadult and juvenile mussels after transfer to soft‐sediment seafloor only when completely protected from mobile predators. Attachment to biodegradable substrate alone was insufficient to prevent the loss of cultured juvenile mussels, while ~80% of wild subadult mussels survived translocation to the seafloor without predator protection—indicating a certain level of resilience. Changes in seeding density failed to prevent loss of cultured juvenile mussels. This study supports further consideration for incorporating cultured subadult and juvenile mussels into restoration, provided subadult and juvenile mussels can be protected until they become established as adults.

The impact of mussel seed fishery on the dynamics of wild subtidal mussel beds in the western Wadden Sea, The Netherlands

For the cultivation of mussels, wild stocks of juveniles are harvested to collect mussel seed as starting material for the culture. These wild stocks are found in the sublittoral western Wadden Sea (NL). After summer spat fall, fisheries in Autumn on newly formed beds is carried out in areas that have the risk of washing away due to storms, or are vulnerable for starfish predation. These wild beds are considered as relatively unstable. On remaining more stable wild beds, seed fishery is carried out in next Spring. As the Wadden Sea is a nature conservation area, mussel seed fisheries is only allowed if no negative impacts on the nature management objectives can be expected. Seed fishery impacts were addressed in an extensive study including effects on sediment composition, macrobenthos and epifauna. In this paper we describe the effects of mussel seed fisheries on the development of the mussel stocks with and without fisheries in 39 pairwise studied impact and control plots.Stocks on seed beds in areas of the sublittoral Western Wadden Sea that are known as unstable, show a large decline within one year after settlement, also when there is no seed fishery. Harvesting seed on more stable beds in Spring results in a statistical significant reduction in stock size, which lasts for a period of two years after the first fishery. For the longer term, there is a gradual decline of the mussel stocks on all studied plots. On three out of the 39 plots, mussel biomass showed a large increase, both on control and impact parts. Also these mussel beds declined and eventually disappeared. A difference in life expectancy of fished and unfished beds was not demonstrated.It is concluded that sublittoral beds gradually disappear, also without fisheries. As a consequence, new recruitment is of critical importance for the long-term survival of sublittoral mussel beds. As we found no significant difference between recruitment on fished and control parts, there are no indications for negative impacts of seed fishery on new recruitment.

Digestive gland microbiome of Pleurobema cordatum: mesocosms induce dysbiosis

ABSTRACT Herein, we characterized the digestive gland (‘gut’) bacterial community (microbiome) of the Ohio pigtoe, Pleurobema cordatum (Rafinesque, 1820), using 16S rRNA gene sequencing. Two populations were compared: wild P. cordatum (n = 5) from the Tennessee River and P. cordatum (n = 9) relocated to artificial mesocosms and exposed to various thermal regimes for 2 weeks. We also characterized the bacterial communities from the habitat (water and sediment) of these wild and mesocosm-held populations. The gut microbiome of wild P. cordatum was dominated by members of the bacterial phylum Tenericutes (72%). By contrast, the gut microbiome of mesocosm-held P. cordatum was dominated by members of the bacterial phylum Proteobacteria (64%). We found no temperature-associated difference in the gut microbiome of mesocosm-held P. cordatum. The bacterial communities of water and sediment from the Tennessee River were diverse and distinct from those of the studied mussels. By contrast, the bacterial communities of water and sediment in the mesocosms were dominated by Proteobacteria. These results suggest that when the studied mussels were moved into artificial rearing environments, their gut microbiome shifted to reflect that of their habitat (i.e. an increase in Proteobacteria). Moreover, the abundance of Tenericutes (also previously reported in other unionids) was reduced from 72% in wild mussels to 3% in mesocosm-held mussels. As a result, we think that mesocosm-held P. cordatum became dysbiotic, which could explain the observed wasting syndrome and associated trickling mortalities in captive P. cordatum.

Modelling mussel (&amp;lt;i&amp;gt;Mytilus spp.&amp;lt;/i&amp;gt;) microplastic accumulation

Abstract. Microplastics (MPs) are a contaminant of growing concern due to their widespread distribution and interactions with marine species, such as filter feeders. To investigate the MPs accumulation in wild and cultured mussels, a dynamic energy budget (DEB) model was developed and validated with the available field data of Mytilus edulis (M. edulis, wild) from the North Sea and Mytilus galloprovincialis (M. galloprovincialis, cultured) from the northern Ionian Sea. Towards a generic DEB model, the site-specific model parameter, half-saturation coefficient (Xk), was applied as a power function of food density for the cultured mussel, while for the wild mussel it was calibrated to a constant value. The DEB-accumulation model simulated the uptake and excretion rate of MPs, taking into account environmental characteristics (temperature and chlorophyll a). An accumulation of MPs equal to 0.53 particles per individual (fresh tissue mass 1.9 g) and 0.91 particles per individual (fresh tissue mass 3.3 g) was simulated for the wild and cultured mussel after 4 and 1 years respectively, in agreement with the field data. The inverse experiments investigating the depuration time of the wild and cultured mussel in a clean-from-MPs environment showed a 90 % removal of MPs load after 2.5 and 12 d respectively. Furthermore, sensitivity tests on model parameters and forcing functions highlighted that besides MPs concentration, the accumulation is highly dependent on temperature and chlorophyll a of the surrounding environment. For this reason, an empirical equation was found, directly relating the environmental concentration of MPs, with the seawater temperature, chlorophyll a, and the mussel's soft tissue MPs load.

Multifactorial Analysis of Environmental Metabolomic Data in Ecotoxicology: Wild Marine Mussel Exposed to WWTP Effluent as a Case Study.

Environmental metabolomics is a powerful approach to investigate the response of organisms to contaminant exposure at a molecular scale. However, metabolomic responses to realistic environmental conditions can be hindered by factors intrinsic to the environment and the organism. Hence, a well-designed experimental exposure associated with adequate statistical analysis could be helpful to better characterize and relate the observed variability to its different origins. In the current study, we applied a multifactorial experiment combined to Analysis of variance Multiblock Orthogonal Partial Least Squares (AMOPLS), to assess the metabolic response of wild marine mussels, Mytilus galloprovincialis, exposed to a wastewater treatment plant effluent, considering gender as an experimental factor. First, the total observed variability was decomposed to highlight the contribution of each effect related to the experimental factors. Both the exposure and the interaction gender × exposure had a statistically significant impact on the observed metabolic alteration. Then, these metabolic patterns were further characterized by analyzing the individual variable contributions to each effect. A main change in glycerophospholipid levels was highlighted in both males and females as a common response, possibly caused by oxidative stress, which could lead to reproductive disorders, whereas metabolic alterations in some polar lipids and kynurenine pathway were rather gender-specific. This may indicate a disturbance in the energy metabolism and immune system only in males. Finally, AMOPLS is a useful tool facilitating the interpretation of complex metabolomic data and is expected to have a broad application in the field of ecotoxicology.

The PAH body burdens and biomarkers of wild mussels in Port Phillip Bay, Australia and their food safety implications

Wild Mediterranean mussels (Mytilus galloprovincialis) were collected from 10 coastal sites of Port Phillip Bay, Australia, and 16 types of Polycyclic aromatic hydrocarbons (PAHs) in their bodies were measured. Also, mussels from 4 of the 10 sites were sampled and the activities of Metallothioneins (MTs), superoxide dismutase (SOD), glutathione S-transferase (GST), and Ethoxyresorufin -o- deethylase (EROD) in the gills were tested. The results demonstrated spatial variation of different PAHs in mussels, which differed from trace metal accumulations to mussels reported in previous studies. Besides, the results of SOD, GST, and EROD showed highly similar features among mussels from all the sites while the results of MTs appeared to be different. The estimation of possible excessive cancer risks caused by wild mussel consumption using the results in this study demonstrated that the PAHs in wild mussels in Port Phillip Bay is a moderate concern for consumers.

Northward establishment of the mediterranean mussel Mytilus galloprovincialis limited by changing climate

Throughout Europe the blue mussel Mytilus edulis is dominant in the north while the Mediterranean mussel Mytilus galloprovincialis prevails in the south. Studies from the 1970s to the late 2000′s documented the northward range expansion of M. galloprovincialis in Europe and predicted this trend to continue with climate change. The objectives of this study were to sample predominantly wild mussels (n = 1459) at twenty-four Irish intertidal sites over a seven year period and at three Welsh sites to investigate (a) the abundance and distribution of Mytilus spp., identified molecularly by polymerase chain reaction (PCR), and (b) compare with historical observations, at Irish sites where M. galloprovincialis was observed to be more abundant than M. edulis. Mussels were sampled more than once at certain sites to investigate if there was a temporal effect. The findings of this study indicated that M. edulis was consistently the most abundant species, followed by hybrids and M. galloprovincialis. At certain sites, hybrids were detected while M. galloprovincialis was absent. This finding may indicate transient M. galloprovinicialis populations or input from individuals subtidally. One factor that may be of importance was the anomalous cold winter “polar snaps” (2010 and 2011) that occurred during this study. In addition, heavy precipitation events and subsequent increased freshwater loading in bays and estuaries also occurred during this time period. Future warming climate scenarios have been predicted to facilitate the northwards establishment of M. galloprovincialis, however, nearshore meteorological extremes may have an impact in its larval settlement, establishment and subsequent reproductive output.

Diseases and parasites of wild and cultivated mussels along the Patagonian coast of Argentina, southwest Atlantic Ocean.

A histological survey of the commercially edible mussels Mytilus platensis and M. chilensis from wild and cultivated populations along the coast of Patagonia, Argentina (42°00' to 54°47'S), was carried out to determine their health status. Diagnostic results included 3 types of inflammatory responses (infiltrative, nodular, and encapsulation), disseminated neoplasia disease, 2 abnormal reproductive conditions (gonadal atresia and intersex), prokaryotic inclusions, protozoans, and metazoans. Pathogen prevalence and infection intensity among mussels of different sampling sites and between those of wild and cultivated populations were compared. Inflammatory responses were recorded in all mussels from all sites, while disseminated neoplasia only occurred in the most southern cultivated M. chilensis. Intracellular prokaryotic inclusions were broadly distributed in the mussels from both northern and southern Patagonian coasts. Ciliates showed the highest prevalence among wild mussels from the colder waters of Bahía Brown. Turbellaria were recorded at higher prevalence in cultured mussels (41.7%), and trematode metacercariae occurred exclusively in intertidal wild mussels. None of the parasites found appears to be a problem to the fishery or farming, although disseminated neoplasia should be monitored. In addition, we found that mytilid species coexisting with M. platensis (Aulacomya atra and Perumytilus purpuratus) at one location shared the same pathological conditions and parasites, which differed from those of M. platensis at a distant locality. These results suggest that pathological conditions and parasites were influenced more by ecological habitat factors than by the species of mussels present, based on similar parasite assemblages found among closely related mytilid hosts in the same geographical area.

First report of signs of infection by Coccomyxa-like algae in wild blue mussels, Mytilus spp., in the Gulf of Maine (USA, Maine).

In August 2019, visual inspection of intertidal zones of the Gulf of Maine (ME, USA) revealed young and adult wild blue mussels, Mytilus spp., in Alley Bay (Jonesport area) with the distinctive L-shaped shell deformity (LSSD) and green spots (GS) in the mantle and adductor muscle. LSSD is a characteristic sign of current or previous mussel infection by photosynthetic unicellular alga from the group Coccomyxa, while GS are algal colonies. Based on these findings, this study represents the first report of infection signs by pathogenic Coccomyxa-like algae in mussels from the coastal waters of the Northeastern United States, providing a base for future large scale monitoring of the alga in the region.

Short-term variations of platinum concentrations in contrasting coastal environments: The role of primary producers

Short-term variations of Pt concentrations and primary production indicators were compared in three contrasting coastal sites during spring bloom: (i) the Gironde Estuary mouth (SW France), (ii) the semi-enclosed Arcachon Bay (SW France), and (iii) the urbanized Genoa Harbor (NW Italy). At each site, surface seawater sampling and physical-chemical measurements were combined to study diel cycles (over 25 h) of dissolved Pt concentrations in seawater (PtD) and master variables reflecting primary production activity (chlorophyll-a, phaeopigments, and particulate organic carbon, POC concentrations). Plankton nets were used in all sites, providing for the first time plankton Pt concentrations (PtPK) over a whole diel cycle (Gironde Estuary mouth) and spot sampling (Arcachon Bay and Genoa Harbor) in the coastal zone. Bivalves (wild oysters or mussels), reflecting organisms at higher trophic levels, were also collected at all sites. The POC/Chl-a ratios in the collected particulate material suggested high contribution of phytoplankton to the particulate matter in the productive Gironde Estuary mouth. At this site, phytoplankton activity partly controlled Pt cycling and particle/dissolved Pt partitioning during daytime. During the night, zooplankton grazing may release Pt into the dissolved phase. These processes are partly masked by external factors such as tide or local Pt sources, especially in more confined and/or urbanized coastal water bodies such as the Arcachon Bay and the Genoa Harbor. Platinum levels in plankton and bivalves from these contrasting sites along the Atlantic and Mediterranean coasts tended to reflect the general Pt levels in seawater. These results clearly suggest that (i) Pt contamination of coastal waters and marine organisms has become a common feature in urbanized sites and (ii) Pt transfer to the marine food chain starts at the basic level of primary producers. By concentrating Pt (Bioconcentration Factor: BCF ~ 104), phytoplankton may serve as a biomonitor to assess Pt contamination in coastal environments.