Queen Scallop Aequipecten Opercularis Research Articles

The queen scallop Aequipecten opercularis: A slow domoic acid depurator?

Domoic acid (DA) is a dangerous phycotoxin produced by several strains of diatoms of the genus Pseudo-nitzschia, and responsible for Amnesic Shellfish Poisoning (ASP) in humans. The increasingly intense ASP-outbreaks along the English Channel over the last three decades have forced persistent harvest closures of economically important and highly contaminated bivalve stocks exhibiting slow DA-depuration rates, like the king scallop Pecten maximus. Under this scenario, other pectinid species, such as the queen scallop Aequipecten opercularis have been empirically proposed as alternative resources to redress the high economic losses due to the banning of the exploitation of P. maximus. Nevertheless, the kinetics of DA depuration in A. opercularis have not been assessed so far, and its direct extraction after ASP-episodes could represent a serious threat to public health. Hence, the main objective of this work was to estimate the DA-depuration rate in the digestive gland (DG) of naturally contaminated scallops A. opercularis after a toxic Pseudo-nitzschia australis bloom subjected to experimental depuration in the laboratory for 30 days. This study also intended to go further in the knowledge about the anatomical distribution of DA in scallop tissues, and corroborate the implications of autophagy in DA-sequestration in the DG of this species as recently hypothesized. In the DG, the DA-depuration rate (0.018 day−1) suggested that even with toxin burdens as low as 40 mg⋅kg−1 in the DG, queen scallops may remain contaminated for about 70 days, thus longer under intensely contamination scenarios. The subcellular analyses corroborated DA-sequestration mainly through late-autophagy within residual bodies in the DG, without differences in the frequencies of anti-DA labeled residual bodies across the entire depuration process. These results revealed that A. opercularis cannot be considered a fast DA-depurator, and represent a baseline knowledge for decision-making about harvesting natural beds of queen scallops after toxic Pseudo-nitzschia blooms. The findings of this work also represent a cornerstone for further research to accelerate DA-depuration in this species.

Effect of Dietary Supplementation with Lactiplantibacillus plantarum I On Queen Scallop Aequipecten opercularis Under Simulated Climate Change Conditions

Abstract This study examined the effects of dietary supplementation of queen scallop Aequipecten opercularis with an indigenous strain of lactic acid bacteria (LAB), Lactiplantibacillus plantarum I, previously isolated from its digestive tract, on gut microbial populations and growth rates during cultivation under simulated climate change conditions (pH 7.8, T = 16 ± 2 °C). After one month of feeding, the results showed a noticeable reduction in aquaculture diseases causing pathogens while maintaining sufficient viable Lpb. plantarum I cells. A higher pH and temperature resulted in higher growth rates, measured by the weight and length of scallops, compared to the control group. The results obtained shed light on the influence of the addition of lactic acid bacteria on the growth of bivalve mollusks under normal and climate change conditions, and provide control of pathogenic microorganisms. In the context of climate change, host-pathogen interactions need to be recognized and put under control by applying natural solutions to minimize the environmental footprint.

Distribution of metals in the queen scallop Aequipecten opercularis during a transplant experiment: Metal rich granules as drivers of Pb bioaccumulation

The queen scallop Aequipecten opercularis accumulates high concentrations of lead (Pb) in its tissues, what has led to the interruption of this fishery in some extraction areas in Galicia (NW Spain). This study follows the dynamics of bioaccumulation of Pb and other metals in this species, the tissue distribution and the subcellular partitioning in selected organs, in order to understand the mechanisms that provoke the high Pb levels reached in its tissues and to increase our knowledge about metal bioaccumulation dynamics in this species. Scallops originating from a clean area were exposed in cages in two places in the Ría de Vigo (one shipyard and a less impacted location) and 10 individuals were collected every month over a three months period. Metal bioaccumulation and metal distribution in several organs, including gills, digestive gland, kidneys, muscle, gonad and remaining tissues, was studied. The results showed that scallops accumulated similar levels of Cd, Pb and Zn at both sites, while Cu and Ni showed an opposite pattern at the shipyard, with Cu concentrations increasing around 10 times and Ni decreasing during the 3 months of exposure. The preferential organs for metal accumulation were the kidneys for Pb and Zn, the digestive gland for Cd, both organs for Cu and Ni, and the muscle for As. Subcellular partitioning of kidney samples additionally showed an extraordinary ability to accumulate Pb and Zn at very high concentrations in kidney granules, a fraction that accounted for 30 to 60 % of Pb in soft-tissues. It is concluded that Pb bioaccumulation in kidney granules is the mechanism responsible for the high levels of Pb observed in this species.

Study of the Impact of Lactiplantibacillus plantarum I on the Health Status of Queen Scallop Aequipecten opercularis

The objective of this research was to isolate and identify lactic acid bacteria living in the digestive tract of the queen scallop Aequipecten opercularis and further test it as a probiotic culture on the growth of the bivalve during one month in captivity. Classic microbiological techniques (API and MALDI TOF) were used and four different strains of Lactiplantibacillus and one Lactococcus were identified and further analyzed, namely: Lactiplantibacillus plantarum I, Lactiplantibacillus plantarum 1, Lactiplantibacillus plantarum 2, Lactococcus lactis, and Lactiplantibacillus brevis. The isolated cultures were further tested for the highest antimicrobial activity towards the most common marine pathogens and survival at different temperatures and pH levels. The strain Lactiplantibacillus plantarum I had the best results, with the highest antimicrobial activity (77–85% pathogen growth inhibition) and the best safety standards showing no antibiotic resistance, and no ability to synthesize biogenic amine and degrade red blood cells. Considering all the abovementioned characteristics, the strain Lpb. plantarum I was further tested on the growth and health status of the bivalve Aequipecten opercularis during a month of cultivation in captivity. The results showed that the incorporation of Lpb. plantarum I led to a decrease in the quantity of test microorganisms in the bivalve and an increase in both the growth rate weight and growth rate length of the queen scallop A. opercularis. Furthermore, the scallops fed with the algae culture + Lpb. plantarum I gained significantly higher meat yield (33.15 ± 2.63%) compared with the control scallops fed only with the algae culture (29.66 ± 2.87%). To conclude, the results from this research indicate that including Lpb. plantarum I as a dietary supplement could enhance growth performance and serve as a feasible approach to reduce pathogen levels while cultivating A. opercularis in captivity.

Commercial Quality, Biological Indices and Biochemical Composition of Queen Scallop Aequipecten opercularis in Culture

Market demand for scallops has considerably increased in recent decades. Although natural populations of scallops are vulnerable, the queen scallop, Aequipecten opercularis, can represent a possible alternative to at-risk species. The aim of this study was to determine the effect of seawater parameters on the commercial quality, biological indices and nutritional quality of the scallop A. opercularis in 1900 L tanks in ex situ conditions. The condition index (CI) and meat yield (MY) peaked in autumn (89.92% and 40.29%, respectively). The muscle index (MI) showed the highest peak during the winter season (5.96%), while the gonadosomatic index (GSI) (34.06%) peaked in the spring months. Protein content (6.89–9.56 g/100 g), lipids (2.58–2.79 g/100 g) and carbohydrates (0.12–0.33 g/100 g) varied during the study period. Seasonal fluctuations in seawater temperature and pH negatively influenced the CI, MY and protein and lipid content, while positively affecting carbohydrate and moisture content. The most suitable period of the year for the consumption of the scallop A. opercularis was found to be the winter and spring periods, when the scallops achieved their highest nutritional value. It can be stated from this study that queen scallops in the Adriatic Sea have a high nutritional quality and that they can be proposed for higher human consumption.

Effects of material composition and face block exposure on the long-term (2014-2018) colonisation of an intertidal RECIF Artificial Reef in the Bay of Seine

An experimental artificial reef (AR) with the incorporation of crushed seashells of the queen scallop Aequipecten opercularis was initiated on the intertidal zone of the Bay of Seine in the framework of the INTERREG IVa RECIF project for a everyone year monitoring observations from March 2014 to April 2018. Three block types were operated: eco-friendly material with 20% or 40% of crushed queen scallop shells, and ordinary concrete made from natural aggregates. On the seven blocks analysed at the end of the experiment in 2018, 74 taxa including 32 sessile and 42 motile fauna have been accounted; no difference of taxonomic richness was observed between material and immersion time. The sessile fauna was identified for the six external faces of two blocks aged of four years: horizontal above face (FAB), horizontal below Face (FBE), face oriented offshore (FOF), face oriented inshore (FIN), vertical face oriented west (FEW) and vertical face oriented east (FEA). FBE showed higher taxonomic richness and abundance than the other block faces. FAB exposed to the light showed the lowest abundances. Our observations showed the efficiency of such AR on the intertidal zone accessible at each spring tide, which was easier to survey than in the subtidal zone, where divers must be mobilised to sample blocks.

Quantifying abundance trends and environmental effects on a population of queen scallop Aequipecten opercularis targeted by artisanal fishers in a coastal upwelling area (Ría de Arousa, NW Spain) using a Bayesian spatial model

Queen scallop Aequipecten opercularis, is exploited by small-scale trawlers in separated aggregations along the east Atlantic coast and the Mediterranean Sea. However, population performance is poorly known. Here, we combine official information and on-board observers’ data over two decades to study the fishery ecology of an aggregation occurring in a coastal upwelling system (Ría de Arousa, NW Spain). Annual landings fluctuated around a mean of 170 tons while beam trawlers declined at a rate of 11 vessels per decade. A hurdle Bayesian spatial model fitted to observers’ catch and effort data showed that the probability of occurrence and abundance of the species increased with fishing effort and decreased in sandy bottoms. Moreover, abundance increased with upwelling intensity and decreased with continental runoff and along the fishing season. Furthermore, occurrence was higher in the inner part of the embayment while abundance increased in the central channel. The predicted index of standardized abundance correlated with the trend in landings, and year-to-year fluctuations in abundance were negatively and positively related to upwelling intensity and net primary production, respectively, during the spawning and settlement period.

RNA-Seq Transcriptome Profiling of the Queen Scallop (Aequipecten opercularis) Digestive Gland after Exposure to Domoic Acid-Producing Pseudo-nitzschia.

Some species of the genus Pseudo-nitzschia produce the toxin domoic acid, which causes amnesic shellfish poisoning (ASP). Given that bivalve mollusks are filter feeders, they can accumulate these toxins in their tissues. To elucidate the transcriptional response of the queen scallop Aequipecten opercularis after exposure to domoic acid-producing Pseudo-nitzschia, the digestive gland transcriptome was de novo assembled using an Illumina HiSeq 2000 platform. Then, a differential gene expression analysis was performed. After the assembly, 142,137 unigenes were obtained, and a total of 10,144 genes were differentially expressed in the groups exposed to the toxin. Functional enrichment analysis found that 374 Pfam (protein families database) domains were significantly enriched. The C1q domain, the C-type lectin, the major facilitator superfamily, the immunoglobulin domain, and the cytochrome P450 were among the most enriched Pfam domains. Protein network analysis showed a small number of highly connected nodes involved in specific functions: proteasome components, mitochondrial ribosomal proteins, protein translocases of mitochondrial membranes, cytochromes P450, and glutathione S-transferases. The results suggest that exposure to domoic acid-producing organisms causes oxidative stress and mitochondrial dysfunction. The transcriptional response counteracts these effects with the up-regulation of genes coding for some mitochondrial proteins, proteasome components, and antioxidant enzymes (glutathione S-transferases, thioredoxins, glutaredoxins, and copper/zinc superoxide dismutases).

Repeatability of escape response performance in the queen scallop (Aequipecten opercularis)

In order for natural selection to operate, physiological and behavioural traits must exhibit both inter-individual variability and intra-individual consistency (i.e. repeatability) in performance. In this study, we describe individual variation and temporal repeatability in the escape responses of the queen scallop, Aequipecten opercularis, and determine whether individuals exhibited consistently high or low rankings in different aspects of the escape response. Five measures of individual performance were recorded on four occasions (days 0, 2, 7 and 28), providing proxies for sensory acuity (response latency), immediate and sustained swimming performance (burst and average clap rates), and swimming endurance (total number of claps and total time spent clapping). All components of the escape response exhibited significant inter-individual variability (all P<0.0001). Escape response latency, burst clap rate, total number of claps and total duration spent clapping maintained significant repeatability over 28 days (all P<0.016). Average clap rate was repeatable in the short term (2 days, P<0.0001) but repeatability declined by 28 days (P=0.097). Concordance analysis indicated that individuals maintained the same performance rankings over time for each component of the escape response (all P<0.001). In addition, some individuals ranked as consistently high or low performers across response latency, burst and average clap rate, and total number of claps. An individual's ability to evade predators through the provision of an escape response of an appropriate magnitude, subject to physiological, behavioural and organismal constraints, will have clear fitness-related consequences.

Margolisiellaislandica sp. nov. (Apicomplexa: Eimeridae) infecting Iceland scallop Chlamys islandica (Müller, 1776) in Icelandic waters

Wild Iceland scallops Chlamys islandica from an Icelandic bay were examined for parasites. Queen scallops Aequipecten opercularis from the Faroe Islands and king scallops Pecten maximus and queen scallops from Scottish waters were also examined. Observations revealed heavy infections of eimeriorine parasites in 95–100% of C. islandica but not the other scallop species. All life stages in the apicomplexan reproduction phases, i.e. merogony, gametogony and sporogony, were present. Trophozoites and meronts were common within endothelial cells of the heart’s auricle and two generations of free merozoites were frequently seen in great numbers in the haemolymph. Gamonts at various developmental stages were also abundant, most frequently free in the haemolymph. Macrogamonts were much more numerous than microgamonts. Oocysts were exclusively in the haemolymph; live mature oocysts contained numerous (>500) densely packed pairs of sporozoites forming sporocysts.Analysis of the 18S ribosomal DNA revealed that the parasite from C. islandica is most similar (97.7% identity) to an unidentified apicomplexan isolated from the haemolymph of the giant clam, Tridacna crocea, from Japan. Phylogenetic analyses showed that the novel sequence consistently grouped with the Tridacna sequence which formed a robust sister clade to the rhytidocystid group.We propose the name Margolisiella islandica sp. nov., referring to both type host and type locality.

Colonization of an artificial reef in south-west England—ex-HMS ‘Scylla’

An ex-Royal Navy frigate, HMS ‘Scylla’, was placed on the seabed in Whitsand Bay, south Cornwall on 27 March 2004. After five years, the reef supported a mature steel wreck community. The colonization of the reef showed wide fluctuations in species abundance in the first two years but, by 2006, most species that dominated or characterized the reef after five years had settled. Significant colonization events included settlement of barnacles, tubeworms and hydroids within a month and remarkably high settlements of the sea urchin Psammechinus miliaris and the queen scallop Aequipecten opercularis in the first year together with starfish Asterias rubens, solitary sea squirts and ephemeral algae. The plumose anemone Metridium senile, a characteristic species of wrecks, arrived in late summer 2004 but the widely distributed dead man's fingers Alcyonium digitatum was not observed until spring 2005. Wrasse were slow to colonize the reef but were established in small numbers by the end of 2007. Sea fans, Eunicella verrucosa, were first observed in August 2007. The species count for the reef stood at 263 taxa by the end of March 2009. The inside of the reef remained poorly colonized even after five years. Areas coated with tributyltin (TBT) antifouling paint only had colonization where the paint had flaked-off or on non-toxic paint markings, but with some indication that colonization may be occurring by a very few species especially near to non-TBT areas. Many species characteristic of natural reefs had not settled and neither do they occur on older wrecks including branching axinellid sponges, some cushion sponges and the yellow cluster anemone Parazoanthus axinellae. The artificial reef developed a community that was distinctly different to nearby natural rock reefs and such artificial structures should not be considered as a replacement for damaged or destroyed natural habitats.

Single nucleotide polymorphism for population studies in the scallops Aequipecten opercularis and Mimachlamys varia

This study reports the first set of SNP markers for the queen scallop Aequipecten opercularis and the black scallop Mimachlamys varia. SNPs were identified in genomic regions amplified by PCR using primers designed for introns of conserved genes by direct sequencing of PCR products. The frequency of SNPs in the two species was around one every 100 bp. Four SNPs in A. opercularis and two in M. varia were genotyped in 317–327 queen scallops and 168 black scallops sampled in Spanish and Irish populations, using an approach based on a single-base extension reaction with mass-modified terminators. The SNPs characterized provided new estimates of genetic variation in the two scallops and constitute a complementary set of genetic markers for population studies in these exploited species.

Size and age-dependent changes of escape response to predator attack in the Queen scallop Aequipecten opercularis

Physiological fitness and exercise capacity decrease with age in humans and rodents, a finding for which, among other causes, the decline of cellular and especially mitochondrial functions with age is held responsible. We investigated changes of escape response to predator attacks in swimming scallops (Aequipecten opercularis) with size using the natural predator Asterias rubens. Aequipecten opercularis swim mainly to avoid predators and a decrease in swimming abilities would increase risk of capture and lower survival. The queen scallop A. opercularis is a very active, epibenthic species with a short lifespan of 8–10 years and a shell height up to 90 mm in the investigated fishing ground around the Isle of Man. No difference in clap rate was found between smaller and bigger A. opercularis individuals, but differences were found in swimming mode (jumping and swimming) and valve opening and closure behaviour between the two size groups in response to predator attack. Smaller individuals showed less jumping movements and closed valves more often and remained closed for longer time than bigger animals. The difference in swimming behaviour is discussed in respect to size and age-dependent changes in morphology and cellular physiology as well as interactions of different main predators (sea stars, crabs) with the different size classes.

Environmental correlates of large-scale spatial variation in the δ13C of marine animals

Carbon stable isotopes can be used to trace the sources of energy supporting food chains and to estimate the contribution of different sources to a consumer's diet. However, the δ 13C signature of a consumer is not sufficient to infer source without an appropriate isotopic baseline, because there is no way to determine if differences in consumer δ 13C reflect source changes or baseline variation. Describing isotopic baselines is a considerable challenge when applying stable isotope techniques at large spatial scales and/or to interconnected food chains in open marine environments. One approach is to use filter-feeding consumers to integrate the high frequency and small-scale variation in the isotopic signature of phytoplankton and provide a surrogate baseline, but it can be difficult to sample a single consumer species at large spatial scales owing to rarity and/or discontinuous distribution. Here, we use the isotopic signature of a widely distributed filter-feeder (the queen scallop Aequipecten opercularis) in the north-eastern Atlantic to develop a model linking base δ 13C to environmental variables. Remarkably, a single variable model based on bottom temperature has good predictive power and predicts scallop δ 13C with mean error of only 0.6‰ (3%). When the model was used to predict an isotopic baseline in parts of the overall study region where scallop were not consistently sampled, the model accounted for 76% and 79% of the large-scale spatial variability (10 1–10 4 km) of the δ 13C of two fish species (dab Limanda limanda and whiting Merlangus merlangius) and 44% of the δ 13C variability in a mixed fish community. The results show that source studies would be significantly biased if a single baseline were applied to food webs at larger scales. Further, when baseline δ 13C cannot be directly measured, a calculated baseline value can eliminate a large proportion of the unexplained variation in δ 13C at higher trophic levels.

Cis-4,7,10,trans-13–22∶4 fatty acid distribution in phospholipids of pectinid species Aequipecten opercularis and Pecten maximus

The distribution of cis-4,7,10,trans-13-docosatetraenoic (c4,7,10,t13-22:4), a peculiar FA previously isolated in the glycerophospholipids of some pectinid bivalves, was investigated in glycerophospholipid classes and subclasses of separated organs (gills, mantle, gonads, and muscle) of the queen scallop Aequipecten opercularis and the king scallop Pecten maximus. Plasmalogen (Pls) and diacyl + alkyl (Ptd) forms of serine, ethanolamine, and choline glycerophospholipids were isolated by HPLC and their FA compositions analyzed by GC-FID. PIs and Ptd forms of serine glycerophospholipids (PlsSer and PtdSer), and to a lesser extend the Pls form of ethanolamine glycerophospholipids (PlsEtn), were found to be specifically enriched with c4,7,10,t13-22:4. This specificity was found to decrease in the tested organs in the following order: gills, mantle, gonad, and muscle. In gills, c4,7,10,t13-22:4 was shown to be the main unsaturated FA of serine glycerophospholipids in both Pls and Ptd forms (23.8 and 19.4 mol%, respectively, for A. opercularis, and 21.0 and 26.2 mol% for P. maximus). These results represent the first comprehensive report on the FA composition of plasmalogen serine subclass isolated from pectinid bivalves. The specific association of the PlsSer with the c4,7,10,t13-22:4 for the two pectinid species can be paralleled to the specific association of the PlsSer with the non-methylene interrupted (NMI) FA and 20:1 (n-11) observed in mussels, clams, and oysters (Kraffe, E., Soudant, P., and Marty, Y. (2004) Fatty Acids of Serine, Ethanolamine and Choline Plasmalogens in Some Marine Bivalves, Lipids 39, 59-66.) This, led us to hypothesize a similar functional significance for c4,7,10,t13-22:4, NMI FA, and 20:1 (n-11) associated with PlsSer subclass of bivalves.

Identification of Mytilus spp. and Pecten maximus in Irish Waters by Standard PCR of the 18S rDNA Gene and Multiplex PCR of the 16S rDNA Gene

Two molecular protocols for the identification of mussel and scallop have been developed using specific primers targeting the mitochondrial 16S ribosomal DNA gene and the nuclear 18S ribosomal DNA gene. Primers for the mitochondrial 16S ribosomal DNA gene in multiplex polymerase chain reaction (PCR) protocols yielded diagnostic DNA fragments for the mussels Mytilus edulis, Mytilus galloprovincialis, and the hybrid Mytilus edulis/galloprovincialis (335 bp), the king scallop Pecten maximus (382 bp) and the black scallop Mimachlamys varia (398 bp). DNA from the queen scallop Aequipecten opercularis showed no consistent PCR amplification of the 16S rDNA gene. Primers for the nuclear 18S rDNA gene in standard PCR protocols yielded similar-sized, diagnostic DNA fragments (approx. 190 bp) for the mussels Mytilus edulis, Mytilus galloprovincialis, and the hybrid Mytilus edulis/galloprovincialis, the king scallop Pecten maximus, the black scallop Mimachlamys varia, and the queen scallop Aequipecten opercularis. Both protocols have been tested with Mytilus spp., P. maximus, and 6 other bivalve species from a wide range of locations in Irish and European waters. Cross reaction of the specific primers with DNA template from any of the 6 other bivalve species was not observed. Rapid DNA extraction using FTA Card technology and the16S rDNA primers allowed for the detection of at least 10 mussel larvae in a subsample of natural plankton.

Interspecific and geographical variations of trace element concentrations in Pectinidae from European waters

Cd, Cu and Zn were analysed in the organs and tissues of the three scallop species from the Bay of Biscay, the variegated Chlamys varia L., the queen scallop Aequipecten opercularis L. and the common scallop Pecten maximus L. for interspecific comparisons. In P. maximus the greatest concentrations of Cd and Cu were found in the digestive gland, whereas the two other species showed similar levels of Cd between digestive gland and kidneys and higher renal Cu concentrations. However, the digestive gland of all Pectinidae species contained from 75% to 93% and 52% to 74% of the total body burdens of Cd and Cu, respectively. Whatever the species, kidneys displayed the highest Zn concentrations, which therefore contained from 53% to 97% of the total body burden of this metal. Also using reported results, ratios between the concentrations in the digestive gland and that in the kidneys discriminated two groups of Pectinidae: (1) the Pecten group ( P. maximus, P. jacobeus and Adamussium colbecki) with a Cd ratio ⩾ 4, a Cu ratio ⩾ 1 and a Zn ratio >20 × 10 −3; (2) the Chlamys group with a Cd ratio ⩽ 1, a Cu ratio ⩽ 1 and a Zn ratio ⩽ 6 × 10 −3. However, no differences in the detoxification processes in the digestive gland were found between groups in this study. 72–80% of the total Cd was found to be soluble, probably bound to metalloproteins such as metallothioneins, while Cu and Zn were mainly found associated to the insoluble fraction of the digestive gland cells whatever the species. Queen scallops from the Faroe Islands were also considered to examine variations of the metal concentrations due to the geographical origin. In this northern area, queen scallops displayed Cd concentrations 2, 4 and 6 times higher in kidneys, muscle and digestive gland, respectively, compared to those from the Bay of Biscay. Consequently, the Cd concentrations in the whole soft parts of the queen scallops were more than 6 times higher in the Faroe Islands than in the Bay of Biscay. In contrast to Cd, both Cu and Zn concentrations in the whole soft parts were 2 times lower in the Faroe Islands, suggesting lower bioavailability of these essential elements.

Nursery-area function of maerl grounds for juvenile queen scallops Aequipecten opercularis and other invertebrates

The services provided by coastal ecosystems such as mangrove forests and sea-grass beds are becoming increasingly recognised, yet the functional role of maerl beds has not been ad- dressed. Maerl forms highly biodiverse habitats composed of loose-lying coralline red algae which build up over thousands of years. These carbonate-rich deposits occur in photic areas with strong water movement; they have a widespread global distribution yet remain one of the most overlooked shallow-water marine habitats, with little known about the ecosystem services maerl may provide. Our diving research in Scotland has shown that pristine live maerl (PLM) grounds fulfil nursery area prerequisites for commercial populations of queen scallops Aequipecten opercularis and other inver- tebrates, such as the soft clam Mya arenaria, the sea urchins Psammechinus miliaris and Echinus escu- lentus, and the starfish Asterias rubens, more effectively than impacted dead maerl and other common substrata. The complex architecture of maerl beds attracts high densities of these juvenile inverte- brates, which use PLM grounds as nursery areas in preference to adjacent substrata. Considering its global distribution, it is highly likely that ecosystem services provided by maerl are considerable. Maerl is easily damaged and killed by a variety of human activities, yet its protection would maintain vital nursery area function, benefiting commercial fishery yields and, pivotally, regional biodiversity.

Damage sustained by epibenthic invertebrates discarded in the Nephrops fishery of the Clyde Sea area, Scotland

The Clyde Sea Nephrops fishery produces ca. 25 000 t y −1 discards with invertebrates accounting for up to 90% of the number of animals discarded. Trawling and handling of the (by-)catch often results in physical injury, the extent of which was previously unknown. Damage sustained by invertebrate discards was assessed following commercial trawling (of 62–270 min duration) and sorting on deck. Brittlestars Ophiura ophiura were most vulnerable with 100% incurring damage, followed by squat lobsters Munida rugosa (57%) and starfish Astropecten irregularis (56%). Harder-shelled species such as hermit crabs Pagurus bernhardus and queen scallops Aequipecten opercularis sustained fewer injuries (14 and 2%, respectively). Shell chipping, loss and damage of limbs were the most frequent types of injury incurred. The severity and frequency of damage was mainly correlated with species-specific morphological and behavioural characteristics. Vessel type, tow duration and animal size had a major influence on damage to the epibenthic invertebrates caught. While damage may potentially be repaired, survival is adversely affected and sublethal effects might significantly impair fitness of frequently trawled individuals and populations.

The shell of the Queen Scallop Aequipecten opercularis (L.) as a promising tool for palaeoenvironmental reconstruction: evidence and reasons for equilibrium stable-isotope incorporation

The Queen Scallop Aequipecten opercularis has been an important part of the marine fauna of the northeast Atlantic region since the Miocene, and is a suitable candidate for palaeoenvironmental studies using stable isotopes. Modern shells were investigated to determine if carbonate is precipitated in isotopic equilibrium in this species, and to confirm that growth continues through the year. Specimens of A. opercularis were cultured under monitored semi-natural conditions over an autumn/winter period, and the analyses of these specimens were supplemented with isotope data from preserved indigenous North Sea specimens. The results indicated that the cultured specimens grew in relatively low temperatures, that oxygen isotopes of shell-exterior carbonate were precipitated in isotopic equilibrium, and that a large proportion of the ambient temperature range was recorded in shell carbonate. The indigenous North Sea specimens exhibited a good correspondence to predicted oxygen isotope values for summer; the isotopic record related to winter was, however, somewhat truncated due to growth decelerations in the specimens. Carbon isotopes of shell-exterior carbonate were calculated as being derived primarily from external sources, and showed comparatively little influence from metabolically derived carbon; this suggests that carbon isotopes were at least close to equilibrium with ambient waters. The limited incorporation of metabolic products suggests that A. opercularis would be a good monitor of changing carbon isotope ratios in seawater-dissolved inorganic carbon. The occurrence of equilibrium shell precipitation is explained using a `pteriomorph shell-calcification model', which proposes that transport of ions through the periostracum caused the composition of the extrapallial fluid to be effectively the same as seawater. Carbonate secretion is, therefore, not influenced significantly by biological (vital) effects.