Quantifying susceptibility of marine invertebrate biocomposites to dissolution in reduced pH

Ocean acidification threatens many ecologically and economically important marine calcifiers. The increase in shell dissolution under the resulting reduced pH is an important and increasingly recognized threat. The biocomposites that make up calcified hardparts have a range of taxon-specific compositions and microstructures, and it is evident that these may influence susceptibilities to dissolution. Here, we show how dissolution (thickness loss), under both ambient and predicted end-century pH (approx. 7.6), varies between seven different bivalve molluscs and one crustacean biocomposite and investigate how this relates to details of their microstructure and composition. Over 100 days, the dissolution of all microstructures was greater under the lower pH in the end-century conditions. Dissolution of lobster cuticle was greater than that of any bivalve microstructure, despite its calcite mineralogy, showing the importance of other microstructural characteristics besides carbonate polymorph. Organic content had the strongest positive correlation with dissolution when all microstructures were considered, and together with Mg/Ca ratio, explained 80–90% of the variance in dissolution. Organic content, Mg/Ca ratio, crystal density and mineralogy were all required to explain the maximum variance in dissolution within only bivalve microstructures, but still only explained 50–60% of the variation in dissolution.</jats:p

Evidence for the effects of decommissioning man-made structures on marine ecosystems globally: a systematic map

Background: Many marine man-made structures (MMS), such as oil and gas platforms or offshore wind turbines, are nearing their ‘end-of-life’ and require decommissioning. Limited understanding of MMS decommissioning effects currently restricts the consideration of alternative management possibilities, often leaving complete removal as the only option in certain parts of the world. This evidence-base describes the ecosystem effects of marine MMS whilst in place and following cessation of operations, with a view to informing decision-making related to their potential decommissioning. Method: The protocol used to create this map was published a priori. Systematic searches of published, literature in English were conducted using three bibliographic databases, ten specialist organisational websites or repositories, and one search engine, up to early 2021. A total of 15,697 unique articles were identified as potentially relevant to our research questions, of which 2,230 were screened at the full-text level. Of that subset, 860 articles met all pre-defined eligibility criteria. A further 119 articles were identified through “snowballing” of references from literature reviews. The final database consists of 979 articles. For each article included, metadata were extracted for key variables of interest and coded into a database. Review findings: The vast majority of eligible articles related to the presence of MMS (96.2%), while just 5.8% considered decommissioning. Overall, articles mainly considered artificial reefs (51.5% of all articles) but increasingly oil and gas (22%), shipwrecks (15.1%) and offshore wind (13.1%). Studies were distributed globally, but the majority focused on the United States, single countries within Europe, Australia, Brazil, China, and Israel; 25 studies spanned multiple countries. Consequently, the bulk of the studies focused on the North Atlantic (incl. Gulf of Mexico, North Sea, and Mediterranean Sea) and North Pacific Oceans. A further 12 studies had a global scope. Studies in majority reported on fish (53%) and invertebrates (41%), and were disproportionately focused on biological (81%) and ecological (48%) impacts. Physico-chemical (13%), habitat (7%), socio-cultural (7%), economic (4%) and functional (8%) outcomes have received less attention. The number of decommissioning studies has been increasing since ca. 2012 but remains noticeably low. Studies mostly focus on oil and gas infrastructures in the USA (Gulf of Mexico) and Northern Europe (North Sea), covering 9 different decommissioning options. Conclusions: This systematic map, the first of its kind, reveals a substantial body of peer-reviewed evidence relating to the presence of MMS in the sea and their impacts, but with considerable bias toward biological and ecological outcomes over abiotic and socio-economic outcomes. The map reveals extremely limited direct evidence of decommissioning effects, likely driven at least in part by international policy preventing consideration of a range of decommissioning options beyond complete removal. Despite evidence of MMS impacts continuing to grow exponentially since the early 1970s, this map reveals key gaps in evidence to support best practice in developing decommissioning options that consider environmental, social and economic effects. Relevant evidence is required to generate greater understanding in those areas and ensure decommissioning options deliver optimal ecosystem outcomes

To what extent can decommissioning options for marine artificial structures move us toward environmental targets?

Switching from fossil fuels to renewable energy is key to international energy transition efforts and the move toward net zero. For many nations, this requires decommissioning of hundreds of oil and gas infrastructure in the marine environment. Current international, regional and national legislation largely dictates that structures must be completely removed at end-of-life although, increasingly, alternative decommissioning options are being promoted and implemented. Yet, a paucity of real-world case studies describing the impacts of decommissioning on the environment make decision-making with respect to which option(s) might be optimal for meeting international and regional strategic environmental targets challenging. To address this gap, we draw together international expertise and judgment from marine environmental scientists on marine artificial structures as an alternative source of evidence that explores how different decommissioning options might ameliorate pressures that drive environmental status toward (or away) from environmental objectives. Synthesis reveals that for 37 United Nations and Oslo-Paris Commissions (OSPAR) global and regional environmental targets, experts consider repurposing or abandoning individual structures, or abandoning multiple structures across a region, as the options that would most strongly contribute toward targets. This collective view suggests complete removal may not be best for the environment or society. However, different decommissioning options act in different ways and make variable contributions toward environmental targets, such that policy makers and managers would likely need to prioritise some targets over others considering political, social, economic, and ecological contexts. Current policy may not result in optimal outcomes for the environment or society

Developing expert scientific consensus on the environmental and societal effects of marine artificial structures prior to decommissioning

This work was supported by the UK Natural Environment Research Council and the INSITE programme [INSITE SYNTHESIS project, grant number NE/W009889/1].Thousands of artificial (‘human-made’) structures are present in the marine environment, many at or approaching end-of-life and requiring urgent decisions regarding their decommissioning. No consensus has been reached on which decommissioning option(s) result in optimal environmental and societal outcomes, in part, owing to a paucity of evidence from real-world decommissioning case studies. To address this significant challenge, we asked a worldwide panel of scientists to provide their expert opinion. They were asked to identify and characterise the ecosystem effects of artificial structures in the sea, their causes and consequences, and to identify which, if any, should be retained following decommissioning. Experts considered that most of the pressures driving ecological and societal effects from marine artificial structures (MAS) were of medium severity, occur frequently, and are dependent on spatial scale with local-scale effects of greater magnitude than regional effects. The duration of many effects following decommissioning were considered to be relatively short, in the order of days. Overall, environmental effects of structures were considered marginally undesirable, while societal effects marginally desirable. Experts therefore indicated that any decision to leave MAS in place at end-of-life to be more beneficial to society than the natural environment. However, some individual environmental effects were considered desirable and worthy of retention, especially in certain geographic locations, where structures can support improved trophic linkages, increases in tourism, habitat provision, and population size, and provide stability in population dynamics. The expert analysis consensus that the effects of MAS are both negative and positive for the environment and society, gives no strong support for policy change whether removal or retention is favoured until further empirical evidence is available to justify change to the status quo. The combination of desirable and undesirable effects associated with MAS present a significant challenge for policy- and decision-makers in their justification to implement decommissioning options. Decisions may need to be decided on a case-by-case basis accounting for the trade-off in costs and benefits at a local level.Publisher PDFPeer reviewe

Developing expert scientific consensus on the environmental and societal effects of marine artificial structures prior to decommissioning

Thousands of artificial (‘human-made’) structures are present in the marine environment, many at or approaching end-of-life and requiring urgent decisions regarding their decommissioning. No consensus has been reached on which decommissioning option(s) result in optimal environmental and societal outcomes, in part, owing to a paucity of evidence from real-world decommissioning case studies. To address this significant challenge, we asked a worldwide panel of scientists to provide their expert opinion. They were asked to identify and characterise the ecosystem effects of artificial structures in the sea, their causes and consequences, and to identify which, if any, should be retained following decommissioning. Experts considered that most of the pressures driving ecological and societal effects from marine artificial structures (MAS) were of medium severity, occur frequently, and are dependent on spatial scale with local-scale effects of greater magnitude than regional effects. The duration of many effects following decommissioning were considered to be relatively short, in the order of days. Overall, environmental effects of structures were considered marginally undesirable, while societal effects marginally desirable. Experts therefore indicated that any decision to leave MAS in place at end-of-life to be more beneficial to society than the natural environment. However, some individual environmental effects were considered desirable and worthy of retention, especially in certain geographic locations, where structures can support improved trophic linkages, increases in tourism, habitat provision, and population size, and provide stability in population dynamics. The expert analysis consensus that the effects of MAS are both negative and positive for the environment and society, gives no strong support for policy change whether removal or retention is favoured until further empirical evidence is available to justify change to the status quo. The combination of desirable and undesirable effects associated with MAS present a significant challenge for policy- and decision-makers in their justification to implement decommissioning options. Decisions may need to be decided on a case-by-case basis accounting for the trade-off in costs and benefits at a local level

OCEAN ACIDIFICATION AND WARMING IMPACTS ON NATIVE AND NON-NATIVE SHELLFISH: A MULTIDISCIPLINARY ASSESSMENT

This study was financed with the aid of a PhD studentship from the University of Plymouth, and relevant scientific conferences attendance funded by The Marine Biological Association of the UK, the British Ecological Society, Plymouth Marine Science Education Foundation, and University of Plymouth Doctoral Training Centre. List of accepted publications: Lemasson, A.J., Fletcher, S., Hall-Spencer, J.M., and A.M., Knights. 2017 “Linking the biological impacts of ocean acidification on oysters to changes in ecosystem services: A review”. Journal of Experimental Marine Biology and Ecology. 492, 49-62. 10.1016/j.jembe.2017.01.019 Lemasson, A.J., Kuri, V., Hall-Spencer, J.M., Fletcher, S., Moate, R. and A.M., Knights. 2017 “Sensory qualities of oysters unaltered by a short exposure to combined elevated pCO2 and temperature”. Frontiers in Marine Science. 4:352. doi: 10.3389/fmars.2017.00352Ocean acidification and warming have been shown to affect a wide range of marine organisms and impact assemblages and ecosystems. Many of the species experiencing negative biological effects provide valuable ecosystem services, yet it is unclear how these biological effects will affect ecosystem services provision. This thesis aimed to appraise the consequences of ocean acidification and warming on important shellfish species, from physiology to provision of ecosystem services, using a multidisciplinary approach. The responses to ocean acidification and warming of two ecologically and commercially important species of oysters – the native European Flat oyster Ostrea edulis, and the non-native Pacific oyster Magallana gigas – were assessed in laboratory mesocosms following long-term exposures to a range of scenarios predicted for 2050 and 2100. Oysters provide numerous ecosystem services, including improvement of water quality, reef formation, and food provision, but are at risks from ocean acidification and other stressors due to negative impacts occurring at multiple life-stages and threatening reef maintenance and functioning (Chapter 1). The physiology of adult oysters appeared susceptible to ocean acidification and warming, with evident sub-lethal effects (Chapter 2). Magallana gigas experienced a greater degree of stress than O. edulis, displaying increased Standard Metabolic Rate, reduced Clearance Rate, and poorer Condition Indices. Reductions in Clearance Rates of M. gigas are especially concerning and may have important ecological impacts by limiting their ability to improve water quality in the future. The physiological changes experienced by individual oysters held important implications for the functioning of the reefs through changes in predation resistance. Again, M. gigas appeared to undergo more pronounced changes than O. edulis, displaying increased muscle strength but weakened shell strength. These changes are expected to alter its susceptibility to predators and influence community level interactions. Both O. edulis and M. gigas also underwent important changes to their biochemical composition with trends for impoverished nutritional quality, which holds direct implications on the provision of sea food. In particular, M. gigas contained lower lipid, carbohydrate, and protein levels, but higher contaminant concentration (copper); this change holds concerns for both future food security and future food safety. It was apparent that the physiological stress experienced (Chapter 2), led to significant energy reallocation from somatic growth to metabolism by depleting energetic reserves (Chapter 4), at the detriment of its nutritional quality. No negative effects on the eating quality of M. gigas (appearance, aroma, texture, taste, and overall acceptability) were recorded following a short-term exposure to ocean acidification and warming (Chapter 5), which was considered positive for the aquaculture sector. In order to secure future food provision and economic revenue, the UK aquaculture industry might need to reconsider its management strategy in the future, and encourage the production and consumption of O. edulis, in addition to the already popular M. gigas. It is clear that the impacts of ocean acidification and warming on oysters are multifaceted and occurring at multiple scales and levels of organisation. The risks to oysters and oyster reefs appear species-specific; in the UK, introduced M. gigas may be more vulnerable than native O. edulis. To secure benefits and minimise costs related to the management of introduced species, these findings could be integrated into the current management and conservation measures in place for these species and the reefs they can form

INVESTIGATIONS INTO THE REPRODUCTIVE BIOLOGY AND LARVAL ECOLOGY OF TWO NON-NATIVE ASCIDIANS, CORELLA EUMYOTA AND ASTEROCARPA HUMILIS, IN UK WATERS

Asterocarpa humilis and Corella eumyota are two ascidians native from the southern hemisphere identified on UK shores in recent years. They are atypical species that although being solitary brood their larvae. Little is known regarding their reproductive behaviour in their introduced range and how their reproductive and larval traits facilitate the populations’ establishment. Here, three experiments were conducted to assess their reproductive seasonality, fecundity and larval ecology; additionally comparisons were made with another solitary brooding species, Dendrodoa grossularia, three typical solitary broadcast-spawning species, Ciona intestinalis, Molgula socialis and Ascidiella aspersa, and three colonial brooding species, Botrylloides violaceus, Botryllus schlosseri and Diplosoma listerianum. A. humilis brooded larvae throughout the year. A. humilis and C. eumyota released larvae for the entire duration of the experiment (February to July).Throughout the season, the average fecundity for C. eumyota was 398.22 offspring.g-1, and 221.96 offspring.g-1 for A. humilis. They displayed high fecundities more similar to broadcast-spawning species than brooding species. Larval dispersal and settlement behaviours were linked to the species’ reproductive strategy. Solitary brooders, including A. humilis and C. eumyota, showed short dispersal distances and preferences for shaded and sheltered substrates, this behaviour potentially reduces post-settlement mortality and promotes population build- up. The ability of C. eumyota and A. humilis to reproduce over a long period of the year, added to their high fecundity and larval behaviour promoting aggregation, allows for a facilitated process of population build-up. This study demonstrates that C.eumyota and A. humilis are efficient invaders whose reproductive traits enable their success.In collaboration with The Marine Biological Association of the U

Seawater carbonate chemistry and fitness and morphology of native oyster Ostrea edulis and invasive Magallana gigas

Ocean acidification and warming (OAW) pose a threat to marine organisms, with particular negative effects on molluscs, and can jeopardize the provision of associated ecosystem services. As predation is an important factor shaping populations in the marine environment, the ability of organisms to retain traits valuable in predation resistance under OAW may be decisive for future population maintenance. We examine how exposure to seawater temperature (control: 16.8°C and warm: 20°C) and atmospheric pCO2 (ambient [400], 750, and 1000 ppm) conditions affects traits linked to predation resistance (adductor muscle strength and shell strength) in two ecologically and economically important species of oysters (Magallana gigas and Ostrea edulis) and relate them to changes in morphometry and fitness (condition index, muscle and shell metrics). We show that O. edulis remained unimpacted following exposure to OAW scenarios. In contrast, the adductor muscle of M. gigas was 52% stronger under elevated temperature and 750 ppm pCO2, and its shell was 44% weaker under combined elevated temperature and 1000 ppm pCO2. This suggests greater resistance to mechanical predation toward the mid-21st century, but greater susceptibility toward the end of the century. For both species, individuals with more somatic tissue held an ecological advantage against predators; consequently, smaller oysters may be favoured by predators under OAW. By affecting fitness and predation resistance, OAW may be expected to induce shifts in predator-prey interactions and reshape assemblage structure due to species and size selection, which may consequently modify oyster reef functioning. This could in turn have implications for the provision of associated ecosystem services