Restorative function of offshore longline mussel farms with ecological benefits for commercial crustacean species.

Offshore ocean aquaculture is expanding globally to meet the growing demand for sustainable food production. At the United Kingdom's largest longline mussel farm, we assessed the potential for the farm to improve the habitat suitability for commercially important crustaceans. Modelled distribution patterns (GAM & GLM) predicted the low complexity seabed beneath the mussel farm was 34-94 % less suitable for European lobster (Homarus gammarus) and brown crab (Cancer pagurus) than nearby rocky reefs. The mussel farm operations, however, contributed large amounts of living mussels and shell material to the seabed. Acoustic telemetry revealed that H.gammarus remained within the farm for between 2 and 283 days using both the farm anchors and areas of seabed dominated by fallen mussels for refuge. In contrast, C. pagurus movements showed no affinity to either the farm infrastructure or benthic habitat under the farm. Stable isotope analysis indicated a high dietary niche overlap in C. pagurus and H. gammarus (67.8 and 84.6 %) between the mussel farm (mixed muddy sediment) and nearby rocky reef. Our mixed-methods suggest that the mussel farm augments structural complexity on the seabed providing refuge and similar feeding opportunities for lobster and crab as their typical habitat on rocky reefs. Longline mussel farms can deliver profound biodiversity-positive effects through biogenic augmentation of degraded habitat for commercial species and potential for co-benefits to local fisheries.

Phenomics enables measurement of complex responses of developing animals to global environmental drivers.

Phenomics offers technological advances for high-dimensional phenotyping, facilitating rapid, high-throughput assessment of physiological performance and has proven invaluable in global research challenges including drug discovery and food security. However, this rapidly growing discipline has remained largely inaccessible to the increasingly urgent challenge of assessing organismal functional sensitivity to global change drivers. Here, we investigate the response of an ecologically important marine invertebrate to multiple environmental drivers using Energy Proxy Traits (EPTs), a new approach for measuring complex phenotypes captured on video as a spectrum of energy levels across different temporal frequencies in fluctuating pixel values. We imaged three developmental stages of the common prawn Palaemon serratus at different salinities and temperatures, and measured EPTs and heart rate, a major proxy of physiological performance in ectotherms present across stages. Significant interactions were detected between temperature, developmental stage and salinity in frequency-specific energy levels. Despite cardiac activity being a significant contributor to the EPT spectra, treatment interactions were different from those observed on EPTs, highlighting additional phenotypic drivers of EPTs. Elevated temperature resulted in a shift of the EPT spectra towards higher frequency signals, indicating a reallocation of resources within the phenome. Using a non-linear dimensionality reduction, we interrogated the responses of EPT spectra in high-dimensional space. We discovered complex developmental-stage specific sensitivities, highlighting both the complexity of phenotypic responses, and the limits of using univariate approaches with pre-selected traits to assess responses to multiple global environmental drivers. EPTs are a high-dimensional, transferrable method of phenotyping, and are therefore highly relevant to addressing the current limitations of traditional methods of phenotyping applied to assessing biological sensitivity to drivers of global change. We predict that EPTs will become an important tool for indiscriminate phenotyping, transferrable between species, developmental stages and experimental designs.

In vitro avian bioaccessibility of metals adsorbed to microplastic pellets.

Microplastics are known to be associated with co-contaminants, but little is understood about the mechanisms by which these chemicals are transferred from ingested plastic to organisms. This study simulates marine avian gastric conditions in vitro to examine the bioaccessibility of authigenic metals (Fe, Mn) and trace metals (Co, Pb) that have been acquired by polyethylene microplastic pellets from their environment. Specifically, different categories of pellet were collected from beaches in Cornwall, southwest England, and exposed to an acidified saline solution of pepsin (pH âˆ¼ 2.5) at 40 °C over a period of 168 h with extracted metal and residual metal (available to dilute aqua regia) analysed by ICP-MS. For Fe, Mn and Co, kinetic profiles consisted of a relatively rapid initial period of mobilisation followed by a more gradual approach to quasi-equilibrium, with data defined by a diffusion model and median rate constants ranging from about 0.0002 (µg L-1)-1 h-1 for Fe to about 7 (µg L-1)-1 h-1 for Co. Mobilisation of Pb was more complex, with evidence of secondary maxima and re-adsorption of the metal to the progressively modified pellet surface. At the end of the time-courses, maximum total concentrations were 38.9, 0.81, 0.014 and 0.10 µg g-1 for Fe, Mn, Co and Pb, respectively, with maximum respective percentage bioaccessibilities of around 60, 80, 50 and 80. When compared with toxicity reference values for seabirds, the significance of metals acquired by microplastics from the environment and exposed to avian digestive conditions is deemed to be low, but studies of a wider range of plastics and metal associations (e.g. as additives) are required for a more comprehensive risk assessment.

The impact of potting for crustaceans on temperate rocky reef habitats: Implications for management.

Multi-use marine protected areas (MPAs) are increasingly designated towards achieving global conservation targets. To develop effective management, the impact of permitted activities must be understood. Potting for shellfish occurs on temperate rocky reefs globally with impact not fully quantified. This UK-based study used underwater video to quantify (a) benthic condition of rocky reefs, (b) mechanisms of potting interaction and (c) true footprint of potting. Assemblages in static gear areas were more indicative of a healthy reef than those in mixed gear areas. Damage was recorded during pot hauling, but the area of damage was not the entire pot haul path. 25-30% of individuals were damaged (commonly through tissue abrasion) or removed. Notably, damage occurred to some long-lived, slow growing taxa raising concerns over impacts. Potting is more destructive than previously thought and managers must balance ecology with social and economic considerations to determine what level of impact is acceptable.

Adsorption of trace metals to plastic resin pellets in the marine environment.

Plastic production pellets collected from beaches of south west England contain variable concentrations of trace metals (Cr, Co, Ni, Cu, Zn, Cd and Pb) that, in some cases, exceed concentrations reported for local estuarine sediments. The rates and mechanisms by which metals associate with virgin and beached polyethylene pellets were studied by adding a cocktail of 5 µg L(-1) of trace metals to 10 g L(-1) pellet suspensions in filtered seawater. Kinetic profiles were modelled using a pseudo-first-order equation and yielded response times of less than about 100 h and equilibrium partition coefficients of up to about 225 ml g(-1) that were consistently higher for beached pellets than virgin pellets. Adsorption isotherms conformed to both the Langmuir and Freundlich equations and adsorption capacities were greater for beached pellets than for virgin pellets. Results suggest that plastics may represent an important vehicle for the transport of metals in the marine environment.