Chlamys Islandica Research Articles

Late Pleistocene boreal molluscs in the Gulf of Cadiz: Past and current oceanographic implications

Remains of molluscs were collected from the seafloor on the north-eastern margin of the Gulf of Cadiz, between 300 and 1000 m water depth, using different sampling methods (e.g. dredging, trawling and box-coring), during several deep-sea expeditions. Samples contained a suite of species which nowadays mostly occur northwards of the English Channel, together with other widespread species. Species now locally extinct in the Gulf of Cadiz and restricted to northern latitudes, which unequivocally indicate a faunal shift, include the gastropods Buccinum undatum, Colus gracilis, Liomesus ovum and Neptunea antiqua, the bivalves Arctica islandica, Chlamys islandica, Modiolus modiolus, Mya truncata and Nuculana pernula and the scaphopod Antalis entalis. These species represent “Boreal Guests” of marked palaeoclimatic significance, some of which are reported for the first time in the Gulf of Cadiz. The boreal species collected were mostly large (>5 cm) whereas smaller boreal species were extremely scarce, probably winnowed away by strong bottom currents. The pteropod Limacina retroversa, at present restricted to water masses northwards of the Iberian Peninsula but widespread in Mediterranean sediments of the last glaciation, was also recorded. Accelerator mass spectrometry (AMS) 14C dates obtained from nine specimens of molluscs ranged between 26.1 and 14.6 kyr B.P., thus confirming their attribution to a last glacial assemblage. The abundance of these molluscan remains in the present Mediterranean Outflow Water pathway could be explained if this outflow was reduced in intensity or more likely shifted to a deeper level, leaving the upper slope in contact with suitable Atlantic intermediate waters. The findings of Boreal Guests in the Gulf of Cadiz document the continuity of the faunal shift which is well-known in the Mediterranean basin. Species still living in the Gulf of Cadiz and the Alboran Sea nevertheless account for 84.6% of specimens among the larger species.

Adding fish waste to the diet of Iceland scallop Chlamys islandica: effects on feeding and reproductive ability

Organic enrichment from fish farming may impact benthic species and habitats in adjacent areas. Norwegian salmon farming is continuously growing, but, due to area conflicts and severe sea-lice problems in the western areas, growth of the industry is focused in the northern areas. Knowledge is scarce on how an increase in fish farming will impact Arctic and subarctic species and habitats. One such species is the Iceland scallop Chlamys islandica, distributed from the Lofoten Islands in Nordland County to the Varangerfjord in Troms and Finnmark County. To study the impact of fine-particle fish faeces on feeding and reproductive ability in adult Iceland scallop, particles <41 µm of finfish waste were added to the diet. Effects were tested via short-term (weeks) feeding studies using 2 diets, 100% cultured algal species and a 50% mix of algae and fish waste. In addition, a 100% fish waste diet was used to study longer-term effects on reproductive ability (months). Feeding (% particle clearance and feeding rate) on the microalgae diet tended to be higher than that on the diet containing fish waste, but the difference was significant only in 2 out of 4 cases. We did not find any effect of diets on reproductive ability (gonad development and fatty acid profiles) of scallops. Lack of knowledge on sufficient food levels for gonad maturation in this species may have affected the results. We suggest that future work includes the transplant of scallops from a reference site to fish production sites and that investigations begin immediately after spawning early in scallop gonad development.

Insights into coastal phytoplankton variations from 1979 to 2018 derived from Ba/Ca records in scallop shells (Chlamys islandica) from a fishing ground in the northern Gulf of St. Lawrence

Bivalve growth is affected by phytoplankton quality and availability, but long-term, coastal environmental time series related to these parameters are often lacking. Therefore, it is crucial to develop methods to accurately quantify trends in phytoplankton dynamics over time. This would be especially important for the fished scallop beds in the northern Gulf of St. Lawrence, where landings sharply declined since the early-2000s. Over the past decade, many studies have highlighted the potential of Ba/Ca ratios in bivalve shells as an environmental proxy for phytoplankton dynamics. This study presents records of Ba/Ca ratios in 31 young Chlamys islandica shells sampled in the Mingan Archipelago from 1979 to 2018. The Ba/Ca master chronology showed a decreasing trend since 2002, which could reflect changes in local phytoplankton bloom taxonomic composition, and coincides with the aforementioned decline in scallop landings. Investigations of environmental controls on barium incorporation into the shells highlight the importance of bottom, nutrient-rich waters to support diatom production or export in this fishing area. The use of such high-resolution seasonal records extracted from bio-archives may identify essential environmental mechanisms that will then assist with the development of an ecosystem-based fishery management strategy.

Organotin compounds (OTs) in surface sediments, bivalves and algae from the Russian coast of the Barents Sea (Kola Peninsula) and the Fram Strait (Svalbard Archipelago).

Organotin pollution in components of benthic ecosystems was investigated in 2019 in the Barents Sea (South shore, Kola Peninsula) and the Fram Strait (Icefjord, Svalbard Archipelago). Six species of organotin compounds (OTs), including monobutyltin, dibutyltin, tributyltin, tetrabutyltin, triphenyltin and tricyclohexyltin, were measured in the surface sediments, bivalve molluscs (Ciliatocardium ciliatum, Macoma calcarea, Chlamys islandica) and macrophyte algae (Saccharina latissima, Palmaria palmata, Ulvaria obscura, Fucus serratus, Fucus distichus). The results obtained showed moderate contamination of the studied samples with OTs. The total content of six tin compounds was in the ranges 35-139ngg-1, 13-108ngg-1 and 2.9-75ngg-1 (dry weight) in the samples of sediments, bivalves and algae, respectively. In most cases, the concentrations of tributyltin in bottom sediments and mollusc tissues did not exceed the established international regulations. The degradation indices analysis of butyl tin derivatives indicated the active transformation of tributyltin and tetrabutyltin in bottom sediments and macrophyte algae and the accumulation of these compounds in the soft tissues of molluscs. The sediment and mollusc concentrations of OTs measured in this study were comparable to those reported for other areas of the Arctic region.

A case report and statewide surveillance of “weak meat” condition of Alaska weathervane scallops, Patinopecten caurinus, linked to a recently identified pathogenic parasite, Merocystis kathae (Apicomplexa: Aggregatidae)

Weathervane scallop, Patinopecten caurinus, the largest scallop species in the world, is distributed from northern California, U.S.A., to the Bering Sea, and is only commercially harvested in Alaska. The fishery is considered well managed by the State of Alaska (U.S.A) Department of Fish and Game (ADF&G) and federal government, with many precautionary measures in place to avoid overharvest. There have been episodic declines in some management areas due to unknown causes. Fishermen also encounter scallops with abnormal adductor muscles, a condition colloquially termed “weak meat”, characterized by the retention of muscle when shucked, an obvious darkened discoloration, and/or an abnormal texture making the product unacceptable for marketing. A similar syndrome in Atlantic sea scallops, Placopecten magellanicus, described as “gray meat”, occurs in the eastern U.S. and Canada, and proposed causes include senescence, loss of bioenergetics due to chronic infestations, or a synergism of these factors. Recently a severe apicomplexan infection was found to cause a gray meat condition in Iceland scallops, Chlamys islandica, and the collapse of that stock. This parasite was subsequently detected in Atlantic sea scallops with the gray meat condition off the U.S. East Coast. Studies that followed identified the parasite as Merocystis kathae, previously described from the common whelk, Buccinum undatum, more than 100 years ago. In 2015 Bering Sea fishermen reported weak meat in their catch, so samples were submitted to ADF&G for diagnosis. Adductor muscles from all affected scallops had many large foci of an apicomplexan associated with necrosis, fibrosis, and muscular atrophy. Given the reduced quality, marketability, and possibly fitness of affected scallops, we performed a survey to estimate prevalence, intensity, and geographic distribution of this apicomplexan in Alaskan weathervane scallops. We sampled 180 scallops, from individual beds within each of the three major geographically broad scallop areas in Alaska. Overall prevalence was about 82%, ranging from 69 to 100% by district. Overall mean infection intensity, based on the number of parasite foci/section, was about 9 (range of 5–29, by location), with scallops from the Bering Sea and Southwest Kodiak being most severely infected. Molecular analyses confirmed that the Alaskan parasite is M. kathae, i.e., the same apicomplexan that caused the collapse of Icelandic scallops and a suspected cause for gray meat and mass mortality of Atlantic sea scallops in northeast North America.

The presence of Apicomplexan parasites in king scallops (Pecten maximus) in Scottish waters

The king scallop (Pecten maximus) is a commercially important species found around the United Kingdom coast. The association of an Apicomplexan-like parasite with mass mortality of Icelandic scallop (Chlamys islandica) in Iceland and the presence of identical parasites in king scallop (Pecten maximus) and queen scallop (Aequipecten opercularis) in Scotland raised serious concerns regarding the health of Scottish king scallops. Marine Scotland Science (MSS) conducted a survey in 2016 to assess the prevalence and the intensity of parasite infection in king scallops. King scallops were collected and sampled during the annual scallop dredge surveys in the Shetland Isles and the east and west coast of Scotland. The king scallop adductor muscle was macroscopically examined and tissue imprints taken to grade the intensity of infection. The parasite was present in the majority of the king scallops sampled in all surveyed areas: Shetland Isles 87.1%, east coast 76.0% and west coast of Scotland 64.1%. However, the parasitic infestations were light in intensity with the majority of the king scallops graded as 1 (≤20 zoites per microscopic field). No macroscopic changes in the adductor muscle were observed and histopathology examination revealed minor localized fiber degeneration of adjacent fibers to parasite clusters. The results suggested the parasite to be widespread around the Scottish coast and it appears to be able to live within the king scallop at low intensity of infection without causing significant downgrade of the adductor muscle (in terms of colour or texture) or mortality. The partial genome sequence of the parasite in king scallops from Scottish waters was identical to the one reported by Kristmundsson and Freeman (2018) in the Icelandic scallop in Icelandic waters.

Rhythms during the polar night: evidence of clock-gene oscillations in the Arctic scallopChlamys islandica

Arctic regions are highly impacted by climate change and are characterized by drastic seasonal changes in light intensity and duration with extended periods of permanent light or darkness. Organisms use cyclic variations in light to synchronize daily and seasonal biological rhythms to anticipate cyclic variations in the environment, to control phenology and to maintain fitness. In this study, we investigated the diel biological rhythms of the Arctic scallop, Chlamys islandica, during the autumnal equinox and polar night. Putative circadian clock genes and putative light perception genes were identified in the Arctic scallop. Clock gene expression oscillated in the three tissues studied (gills, muscle, mantle edge). The oscillation of some genes in some tissues shifted from daily to tidal periodicity between the equinox and polar night periods and was associated with valve behaviour. These results are the first evidence of the persistence of clock gene expression oscillations during the polar night and might suggest that functional clockwork could entrain rhythmic behaviours in polar environments.

Partial characterization of the lipidome of the cold-water scallop, Chlamys islandica.

Fingerprinting of the main lipid components of the digestive gland of the Icelandic scallop-Chlamys islandica-has been performed by ultra-high-performance liquid chromatography coupled with time of flight high-resolution mass spectrometry, UHPLC-HRMS/ToF. This method allowed the identification of 224 lipids, including phosphatidylcholines (PC), plasmanyl (PC-O)/plasmenyl (PC-P) phosphatidylcholines, lyso-phosphatidylcholines (LPC), and their plasmanyl/plasmenyl forms (LPC-O/LPC-P). Diacylglycerols (DG), triacylglycerols (TG), and cholesteryl esters (CE) were the neutral lipids (NL) analyzed. While all of the lipids showed a strong seasonal dependence in terms of quantity, only NLs presented significant qualitative changes. Principal component analysis (PCA) of TG and DG profiles evidenced a prevalence of low unsaturated TGs and DGs in spring, which were replaced by species with a higher degree of unsaturations in summer. In autumn, long and highly unsaturated TGs constitute the lipid fraction of the digestive gland of the scallop, while DG species offer a mixed profile. This study contributes to the characterization and the elucidation of the lipidome of Chlamys islandica and provides baseline data for further study of the effects of pollutants on the lipidome of the Icelandic scallop, often used as a sentinel species in biomonitoring programs.

In vivo31P-MRS of muscle bioenergetics in marine invertebrates: Future ocean limits scallops' performance

ObjectDynamic in vivo31P-NMR spectroscopy in combination with Magnetic Resonance Imaging (MRI) was used to study muscle bioenergetics of boreal and Arctic scallops (Pecten maximus and Chlamys islandica) to test the hypothesis that future Ocean Warming and Acidification (OWA) will impair the performance of marine invertebrates. Materials & methodsExperiments were conducted following the recommendations for studies of muscle bioenergetics in vertebrates. Animals were long-term incubated under different environmental conditions: controls at 0 °C for C. islandica and 15 °C for P. maximus under ambient PCO2 of 0.039 kPa, a warm exposure with +5 °C (5 °C and 20 °C, respectively) under ambient PCO2 (OW group), and a combined exposure to warmed acidified conditions (5 °C and 20 °C, 0.112 kPa PCO2, OWA group). Scallops were placed in a 4.7 T MR animal scanner and the energetic status of the adductor muscle was determined under resting conditions using in vivo31P-NMR spectroscopy. The surplus oxidative flux (Qmax) was quantified by recording the recovery of arginine phosphate (PLA) directly after moderate swimming exercise of the scallops. ResultsMeasurements led to reproducible results within each experimental group. Under projected future conditions resting PLA levels (PLArest) were reduced, indicating reduced energy reserves in warming exposed scallops per se. In comparison to vertebrate muscle tissue surplus Qmax of scallop muscle was about one order of magnitude lower. This can be explained by lower mitochondrial contents and capacities in invertebrate than vertebrate muscle tissue. Warm exposed scallops showed a slower recovery rate of PLA levels (kPLA) and a reduced surplus Qmax. Elevated PCO2 did not affected PLA recovery further. ConclusionDynamic in vivo31P-NMR spectroscopy revealed constrained residual aerobic power budgets in boreal and Arctic scallops under projected ocean warming and acidification indicating that scallops are susceptible to future climate change. The observed reduction in muscular PLArest of scallops coping with a warmer and acidified ocean may be linked to an enhanced energy demand and reduced oxygen partial pressures (PO2) in their body fluids. Delayed recovery from moderate swimming at elevated temperature is a result of reduced PLArest concentrations associated with a warm-induced reduction of a residual aerobic power budget.

Structure and long-term dynamics of zoobenthos communities in the areas of scallop Chlamys islandica beds at Kola Peninsula

Current state of zoobenthos in the areas of scallop Chlamys islandica beds in the southern Barents Sea and eastern White Sea (Voronka) is described. The scallop stock is ex­ploited there with the landing by specialized vessels, without separation of catch, so bycatch of other species is considerable. As the result, significant changes occurred in structure of benthic communities during the times of scallop fishery. To assess the fishery effect, species composition of benthos, its dominant species and trophic structure is considered separately for 4 regions with different degree of exploitation. Dynamics of zoobenthos abundance is traced over the last 25 years. Changes in trophic structure of the benthic community at Cape Svyatoy Nos (southern Barents Sea) are analyzed in details. Although up to ¼ of its total biomass is presented by carnivorous species and the biomass of C. islandica has decreased, the portion of sestonophages has increased in this community. Recently a recovery of zoob­enthos is observed in its southern part, supposedly because of the animals redistribution from adjacent areas unaffected by fishery. On the contrary, extremely low biomass of zoobenthos, in particular scallop, is observed in the northern part of the community. Biomass of benthos in the Voronka area is high, but it is formed mainly by mussels. There is concluded that more than a decade is required for full recovery of the scallop stock and accompanying zoobenthos communities to the native state.

Экология и распределение исландского гребешка Chlamys islandica (Bivalvia, Pectinidae) в Кольском заливе (Баренцево море)

Экология и распределение исландского гребешка Chlamys islandica (Bivalvia, Pectinidae) в Кольском заливе (Баренцево море)

Comparison of Three Methods for Aging the Iceland Scallop Chlamys islandica

The Gilbert Bay (GB) Marine Protected Area (MPA) on the southeastern coast of Labrador was established in 2005 to protect a resident population of Atlantic cod (Gadus morhua). Commercial dredging for Iceland scallops (Chlamys islandica) in the bay was permitted to continue under MPA regulations, but was excluded from areas of cod spawning. The average size of Iceland scallops harvested in GB is smaller than in the Strait of Belle Isle approximately 150 km to the south. Local fishermen have suggested this is due to slow growth, and this prompted the present study to test the hypothesis that Iceland scallops grow more slowly in GB than in the Strait of Belle Isle. Scallop growth was parameterized as change in shell height with age. Three methods of aging individual scallops were used: interpreting external growth rings on the shell, counting growth increments on the calcareous portion of the shell hinge ligament, and counting internal shell layer growth zones. Counting ligament growth increments and internal shell layer growth zones gave similar estimates of age. In comparison, interpreting external growth rings on the shell underestimated the age of individual scallops. If the ligament method and the internal shell layer method of aging are accurate (scallops of known-age were not examined), scallops in GB require eleven years of growth to recruit to the fishery (attain a shell height of 60 mm). This is substantially longer than the 6-y period estimated using the external growth rings method of aging. Growth rate parameters of Iceland scallops in GB, the Strait of Belle, and in the Nuuk area of West Greenland were found to be similar. The relatively small shell size of scallops presently harvested in GB is not due to anomalous growth, but more likely attributable to repeated dredging of scallop beds in the past and removal of the larger individuals.

In the darkness of the polar night, scallops keep on a steady rhythm.

Although the prevailing paradigm has held that the polar night is a period of biological quiescence, recent studies have detected noticeable activity levels in marine organisms. In this study, we investigated the circadian rhythm of the scallop Chlamys islandica by continuously recording the animal’s behaviour over 3 years in the Arctic (Svalbard). Our results showed that a circadian rhythm persists throughout the polar night and lasts for at least 4 months. Based on observations across three polar nights, we showed that the robustness and synchronicity of the rhythm depends on the angle of the sun below the horizon. The weakest rhythm occurred at the onset of the polar night during the nautical twilight. Surprisingly, the circadian behaviour began to recover during the darkest part of the polar night. Because active rhythms optimize the fitness of an organism, our study brings out that the scallops C. islandica remain active even during the polar night.

First evidence of marine diesel effects on biomarker responses in the Icelandic scallops, Chlamys islandica.

The decrease of ice cover in polar areas is expected to lead to an increase in ship traffic. In this context, the risk associated with exposure of the aquatic environment to oil-related chemicals from spills and/or accidental fuel discharges from ships will increase in the near future, potentially causing negative impacts on sensitive Arctic species. This study investigated for the first time the biomarker responses of the Icelandic scallops (Chlamys islandica) to marine diesel exposure. Antioxidant response, neurotoxic effect, gonad maturation, and lipid content were assessed in male and female scallops, Chlamys islandica after a 7-day exposure to marine diesel. At the end of exposure, results showed an inhibition of acetylcholinesterase activity in Icelandic scallops exposed to high concentration of diesel. At the end of exposure, results showed an increase in naphthalene residues in hemolymph, together with an inhibition of AChE activity in Icelandic scallops exposed to high concentration of diesel. In addition, alteration of the escape capacity was observed suggesting effects on behavior responses. Overall, this study contributes to the better knowledge of physiological effects of marine diesel in Arctic marine organisms.

Biological effects of mechanically and chemically dispersed oil on the Icelandic scallop (Chlamys islandica)

This study aimed to simulate conditions in which dispersant (Dasic NS) might be used to combat an oil spill in coastal sub-Arctic water of limited depth and water exchange in order to produce input data for Net Environmental Benefit Analysis (NEBA) of Arctic and sub-Arctic coastal areas. Concentration dependent differences in acute responses and long-term effects of a 48h acute exposure to dispersed oil, with and without the application of a chemical dispersant, were assessed on the Arctic filter feeding bivalve Chlamys islandica. Icelandic scallops were exposed for 48h to a range of spiked concentrations of mechanically and chemically dispersed oil. Short-term effects were assessed in terms of lysosomal membrane stability, superoxide dismutase, catalase, gluthatione S-transferases, glutathione peroxidases, glutathione reductase, glutathione, total oxyradical scavenging capacity, lipid peroxidation and peroxisomal proliferation. Post-exposure survival, growth and reproductive investment were followed for 2 months to evaluate any long-term consequence. Generally, similar effects were observed in scallops exposed to mechanically and chemically dispersed oil. Limited short-term effects were observed after 48h, suggesting that a different timing would be required for measuring the possible onset of such effects. There was a concentration dependent increase in cumulative post-exposure mortality, but long-term effects on gonadosomatic index, somatic growth/condition factor did not differ among treatments.

Is an Apicomplexan Parasite Responsible for the Collapse of the Iceland Scallop (Chlamys islandica) Stock?

Due to the total and unexpected collapse of the Iceland scallop, Chlamys islandica, stocks around Iceland during the 2000s, a commercial fishing ban has been imposed on this valuable resource since 2003. Following the initial identification of an apicomplexan parasite in the scallops, a long-term surveillance program was established to evaluate the effect of the parasite on the population. The infections were highly prevalent in all shell sizes throughout the study. However, the parasite only impacts mature scallops where they cause severe macroscopic changes, characterized by an extensively diminished and abnormally coloured adductor muscle. A highly significant relationship was observed between infection intensity and gonad and adductor muscle indices. The first four years of the study, were characterized by high infection intensity and very poor condition of the adductor muscle and gonads, whilst during subsequent years, infections gradually decreased and the condition of the scallops improved. Histopathological changes were restricted to the presence of apicomplexan zoites which were widely distributed, causing varying degrees of pathology in all organs. In heavy infections, muscular and connective tissues were totally necrotized, destroying significant parts of numerous organs, especially the adductor muscle, digestive gland and gonads. The progression of the disease was in good synchrony with the mortality rates and the subsequent decline observed in the scallop stock and recruitment indices. Our findings strongly suggest that the apicomplexan parasite played a major role in the collapse of the Iceland scallop stock in Breidafjordur. In addition to causing mortality, the infections significantly impact gonad development which contributes further to the collapse of the stock in the form of lower larval recruitment. Furthermore, compelling evidence exists that this apicomplexan pathogen is causing serious disease outbreaks in other scallop populations. Similar abnormal adductor muscles and the parasite itself have been identified or observed in association with other mass mortality events in several different scallop species and commercial stocks in the northern hemisphere.

Biomarker modulation associated with marine diesel contamination in the Iceland scallop (Chlamys islandica).

The decrease of ice cover in the Arctic will lead to an increase of ship traffic in the upcoming decades. Consequently, oil pollution is expected. In this context, the goals of this study were to evaluate the biological impact of marine diesel contamination and, on this basis, to determine analytical tools of interest (biomarkers) for future biomonitoring of diesel spills. Using a 7-day contamination protocol, this study investigated biochemical modulations in the digestive gland of the Iceland scallop (Chlamys islandica). Incorporation of contaminants was verified assessing haemolymph metabolites. Results showed a response of glutathione-S-transferase to contamination suggesting detoxification processes and the suitability of such a tool for diesel spill biomonitoring. The lack of modulation of superoxide dismutase activity and lipid peroxidation suggests no oxidative stress and the unsuitability of these molecular tools for biomonitoring.

Environmental effects monitoring at the Terra Nova offshore oil development (Newfoundland, Canada): Program design and overview

An environmental effects monitoring (EEM) program was developed by Suncor (formerly Petro-Canada) in 1997/98 to assess effects of the Terra Nova offshore oil and gas development on the receiving environment. The Terra Nova Field is located on the Grand Banks approximately 350km southeast of Newfoundland (Canada), at approximately 100m water depth. The EEM program was developed with guidance from experts in government, academia and elsewhere, and with input from the public. The EEM program proposed by Suncor was accepted by Canadian regulatory agencies and the program was implemented in 2000, 2001, 2002, 2004, 2006, 2008 and 2010, with pre-development sampling in 1997. The program continues to be implemented every two years. EEM includes an assessment of alterations in sediment quality through examination of changes in sediment chemistry, particle size, toxicity and benthic invertebrate community structure. A second component of the program examines potential effects on two species of commercial fishing interest: Iceland scallop (Chlamys islandica) and American plaice (Hippoglossoides platessoides). Chemical body burden for these two species is examined and taste tests are performed to assess the presence of taint in edible tissues. Effects on American plaice bioindicators are also examined. A final component of the program assesses potential effects of the Terra Nova development on water quality and examines water column chemistry, chlorophyll concentration and physical properties. The papers presented in this collection focus on effects of drill cuttings and drilling muds on the seafloor environment and, as such, report results on sediment quality and bioaccumulation of drilling mud components in Iceland scallop and American plaice. This paper provides information on drilling discharges, an overview of the physical oceanography at the Terra Nova Field, and an overview of the field program designed to assess environmental effects of drilling at Terra Nova.

Examination of body burden and taint for Iceland scallop (Chlamys islandica) and American plaice (Hippoglossoides platessoides) near the Terra Nova offshore oil development over ten years of drilling on the Grand Banks of Newfoundland, Canada

This paper presents results of analyses of body burdens of metals and hydrocarbons, and taste tests for taint, in Iceland scallop and American plaice performed as part of the Environmental Effects Monitoring (EEM) program for the Terra Nova offshore oil development (Grand Banks of Newfoundland, Canada). Scallop and plaice were collected in a Study Area located within approximately 1km of drill centres at Terra Nova and in a Reference Area located approximately 20km from the development. Samples were collected in 1997 to establish a baseline, and from 2000 to 2010, during drilling periods. Scallop adductor muscle tissue was contaminated with >C10–C21 aliphatic hydrocarbons resembling the drilling fluid in the synthetic drilling mud (SBM) used at Terra Nova in 2000, 2002 and 2004, but contamination of adductor muscle was not noted in 2006, 2008 and 2010. The maximum concentration in muscle was 28mg/kg wet weight, noted in 2002. Scallop viscera was contaminated with hydrocarbons resembling drilling fluid in SBMs near drill centres in all EEM years except 2010. Viscera contamination with >C10–C21 hydrocarbons gradually decreased from a maximum of 150mg/kg in 2000, to a maximum of 27mg/kg in 2008; all values were below the laboratory reporting detection limit of 15mg/kg in 2010. Therefore, evidence from both muscle and viscera indicates a decrease in tissue hydrocarbon contamination in recent years. Barium, another major constituent in drilling muds, has not been noted in scallop adductor muscles at concentrations above the reporting detection limit, but barium was detected in viscera in baseline and EEM years. The maximum concentration of barium in viscera during baseline sampling was 8mg/kg. The maximum concentration in EEM years (29mg/kg) was noted in 2000. The maximum concentration in 2010 was 25mg/kg. The concentration of metals other than barium in scallop tissues was similar between the Terra Nova Study Area and the Reference Area. Hydrocarbons resembling the fluid in SBMs were noted in one American plaice liver sample collected near drill centres in 2000. Otherwise, there has been no evidence of project-related metals or hydrocarbon contamination in plaice liver or fillet samples. There has been no evidence of taint (off-taste) for scallop adductor muscle and plaice fillet tissue in baseline or EEM years. Combined with a parallel study on fish bioindicators at Terra Nova that showed that fish health at Terra Nova was similar to that at the Reference Area (Mathieu et al., 2011), these results indicate little to no detectable biological effects on Iceland scallop and American plaice as a result of Terra Nova activities.

A simple method to reduce the risk of cadmium exposure from consumption of Iceland scallops (Chlamys islandica) fished in Greenland

This paper studied the levels and organ distribution of the toxic heavy metal cadmium in scallops from unpolluted Greenlandic waters. The scallops had an average cadmium concentration of 2.93±0.94μg/g wet weight in the total soft tissues and no concentration dependent effect was found for gender or size (both p>0.05). The kidney was the primary organ for cadmium accumulation with a mean of 226.2±111.7μg/g wet weight, and despite the small weight of the kidney, it appeared as the principal contributor of cadmium with 92% of the total cadmium body burden. The cadmium concentrations in the total soft tissues far exceeded the EU-limit of 1μg/g wet weight for cadmium in bivalves. Based on this, selective evisceration of the cadmium-rich kidney and digestive gland during processing can be regarded as a reliable measure to be taken in order to reduce the cadmium content of scallops used for human consumption.