Spatio-temporal trace element fingerprinting of king scallops (Pecten maximus) reveals harvesting period and location

Effects of H2O2 pretreatment on the elemental fingerprints of bivalve shells and their implications for the traceability of geographic origin

The fraudulent mislabelling of seafood geographic origin has been growing due to complex supply chains and growing consumer demand. To address this issue, seafood traceability tools, such as those based on elemental fingerprints (EF) of bivalve shells, have been successfully used to confirm their harvesting location. However, despite the usefulness of these methodologies, there is still room for optimization. Therefore, this study evaluated the effects of a routine procedure during bivalve shells preparation for ICP-MS analysis - their pretreatment with H2O2 to remove organic components. More specifically, the present study evaluated the effects of H2O2 on i) the elemental fingerprints of shells of two bivalve species (Ruditapes philippinarum and Cerastoderma edule) from four different locations over the north-western and the western Iberian coast, and ii) their influence on the accuracy of models (based on the EF of shells) used to confirm the geographic origin of these species. Significant differences were observed between untreated and pretreated shells of R. philippinarum (p within location ranging from 0.0001 to 0.0011) and C. edule (p ranging from 0.0001 to 0.0007 for C. edule) for both their elemental fingerprints as a whole and several individual elements. The accuracy of the models employed to determine the origin of the two bivalve species, using i) untreated shells, ii) pretreated shells, and iii) both pretreated and untreated shells grouped per location, was high, with the models accurately predicting the geographic origin of 100, 90 and 95% of R. philippinarum and 95, 100 and 95% of C. edule, respectively. These results show that the shifts in the EF of bivalve shells promoted by treating them with H2O2 prior to ICP-MS analysis did not affect the accuracy of the models used to confirm the geographic origin of both bivalve species. Therefore, the need to pre-treat bivalve shells with H2O2 can be dismissed in future studies addressing the traceability of bivalves when using ICP-MS, thus contributing to reducing environmental impacts and economic costs associated with this procedure, as well as the time required to obtain results.

Reading the biomineralized book of life: expanding otolith biogeochemical research and applications for fisheries and ecosystem-based management

Chemical analysis of calcified structures continues to flourish, as analytical and technological advances enable researchers to tap into trace elements and isotopes taken up in otoliths and other archival tissues at ever greater resolution. Increasingly, these tracers are applied to refine age estimation and interpretation, and to chronicle responses to environmental stressors, linking these to ecological, physiological, and life-history processes. Here, we review emerging approaches and innovative research directions in otolith chemistry, as well as in the chemistry of other archival tissues, outlining their value for fisheries and ecosystem-based management, turning the spotlight on areas where such biomarkers can support decision making. We summarise recent milestones and the challenges that lie ahead to using otoliths and archival tissues as biomarkers, grouped into seven, rapidly expanding and application-oriented research areas that apply chemical analysis in a variety of contexts, namely: (1) supporting fish age estimation; (2) evaluating environmental stress, ecophysiology and individual performance; (3) confirming seafood provenance; (4) resolving connectivity and movement pathways; (5) characterising food webs and trophic interactions; (6) reconstructing reproductive life histories; and (7) tracing stock enhancement efforts. Emerging research directions that apply hard part chemistry to combat seafood fraud, quantify past food webs, as well as to reconcile growth, movement, thermal, metabolic, stress and reproductive life-histories provide opportunities to examine how harvesting and global change impact fish health and fisheries productivity. Ultimately, improved appreciation of the many practical benefits of archival tissue chemistry to fisheries and ecosystem-based management will support their increased implementation into routine monitoring.

Graphical abstract

Multi-mineral fingerprinting analysis of the Chinese mitten crab (Eriocheir sinensis) in Yangcheng Lake during the year-round culture period

Chinese mitten crabs (Eriocheir sinensis), originating from Yangcheng Lake, are valuable aquatic products in China. To characterize changes in nutrients in this species in Yangcheng Lake during the year-round culture period, the contents of ten mineral elements in the third pereiopod were evaluated. Principal component analysis revealed that mineral elements changed substantially in the first three months. Thereafter, the elemental "fingerprint" stabilized, and samples could not be accurately distinguished. This pattern was supported by linear discriminant analysis and self-organizing map analysis. These results demonstrate that a long period of time is required for element characteristics to stabilize, suggesting that short-term breeding is insufficient to obtain the natural elemental "fingerprint." In addition, our findings provide a basis for verifying the origin of Chinese mitten crab and other aquatic taxa in Yangcheng Lake.

Assessing the elemental fingerprints of cockle shells (Cerastoderma edule) to confirm their geographic origin from regional to international spatial scales

Geographic origin is directly linked to the quality and commercial value of bivalves. The globalization of the seafood trade and the increasing number of fraudulent practices in the bivalves industry has prompted consumers to become increasingly aware on the geographic origin of the seafood they consume. To enhance consumers' confidence and allow authorities to effectively enforce regulations and contain risks that threaten public health, fast and accurate tools must be made available to confirm claims along the trade chain on the geographic origin of bivalves. In the present study the efficiency of using the elemental fingerprints of a small-homogenized subsample of the shell of common cockles (Cerastoderma edule) to confirm their harvesting location is evaluated at different spatial scales: i) regional (along the Galician coast (Spain) - Espasante, Barallobre, Rio Anllóns, Camariñas, Muros, Noia, Carril, Grove, Combarro, Placeres, Moaña, and Baiona), ii) national (along the Portuguese coast - Ria de Aveiro, Óbidos lagoon, Tagus estuary, Sado estuary and Ria Formosa), and iii) international (along the Northeast Atlantic coast - Hejeltefjorden (Norway), Nykobing Mors (Denmark), Sylt (Germany), Slikken van Viane (Netherlands), Roscoff (France), Plymouth (England), Swansea (Wales), Ria de Aveiro (Portugal) and Oualidia (Morocco). Results confirm that elemental fingerprints of bivalve shells are significantly different among locations and that they can be successfully used with high accuracy to discriminate the geographic origin of cockles at all spatial scales surveyed (97.2% at regional scale, 99.3% at national scale and 100% at international scale). Overall, elemental fingerprints of a small-homogenized subsample of the shell showed to be a replicable, low cost and fast tool to reliably trace the place of origin of cockles sampled at different spatial scales, with success rate of discrimination directly increasing with distance between collection sites.

Mollusk shell alterations resulting from coastal contamination and other environmental factors

Effects of contamination on aquatic organisms have been investigated and employed as biomarkers in environmental quality assessment for years. A commonly referenced aquatic organism, mollusks represent a group of major interest in toxicological studies. Both gastropods and bivalves have external mineral shells that protects their soft tissue from predation and desiccation. These structures are composed of an organic matrix and an inorganic matrix, both of which are affected by environmental changes, including exposure to hazardous chemicals. This literature review evaluates studies that propose mollusk shell alterations as biomarkers of aquatic system quality. The studies included herein show that changes to natural variables such as salinity, temperature, food availability, hydrodynamics, desiccation, predatory pressure, and substrate type may influence the form, structure, and composition of mollusk shells. However, in the spatial and temporal studies performed in coastal waters around the world, shells of organisms sampled from multi-impacted areas were found to differ in the form and composition of both organic and inorganic matrices relative to shells from less contaminated areas. Though these findings are useful, the toxicological studies were often performed in the field and were not able to attribute shell alterations to a specific molecule. It is known that the organic matrix of shells regulates the biomineralization process; proteomic analyses of shells may therefore elucidate how different contaminants affect shell biomineralization. Further research using approaches that allow a clearer distinction between shell alterations caused by natural variations and those caused by anthropogenic influence, as well as studies to identify which molecule is responsible for such alterations or to determine the ecological implications of shell alterations, are needed before any responses can be applied universally.