Climate change and the costs of survival in two species of marine crabs with contrasting abilities to compensate for environmental change

The accumulation of CO2 in the atmosphere as a result of human activities over the past 250 years is causing rapid changes in the World's oceans towards conditions not seen for millions of years. Increased atmospheric CO2 is leading to an increase in sea surface temperature (0.6C in the past 100 years) and is causing an expansion and dilution of the oceans due to increased rainfall and input of melt water from terrestrial glaciers and ice sheets. In addition, the ocean has absorbed about one third of the CO2 produced by humans since pre-industrial times. The resulting reductions in ocean pH, otherwise known as Ocean Acidification (OA) and carbonate concentrations are causing some alarm, as many marine invertebrates such as corals, echinoderms and molluscs depend on seawater carbonate sources to calcify their external shells and skeletons. Moreover, these groups are largely intolerant of environmental stress and are limited in their abilities to adjust to change. As a result they are considered to be the most sensitive to the climate-related changes expected in the oceans. Currently there is a real concern that many of these species will experience population declines and may even become extinct. This would lead to irreversible changes in the ecology of marine ecosystems by influencing community interactions and community structure.

More recently, however, it has become apparent that taxa and species normally expected to be more tolerant of the projected changes may also be under threat. This realisation has come about because of recent examination of longer term responses to OA (weeks to months) in response to multiple variables i.e. usually OA plus temperature. It is now appears that organisms that are able to compensate physiologically and buffer the changes caused by environmental disruption, may be indirectly impacted by these environmental changes because such adjustments are ultimately energetically expensive. Currently, it is unknown what will happen to these organisms over time because the energy required for compensation could be diverted away from other vital processes such as immune function and growth, leading to increased susceptibilities to disease and a reduction in growth rates. The present project aims to establish links between compensatory capacities, energy use and performance in 2 species of brachyuran crabs with differing abilities to compensate for change. First year juvenile crabs from an ecologically important and highly invasive species outside of Europe, Carcinus maenas, and a commercially important species, Cancer pagurus, will be exposed to elevated pCO2 (0.08 kPa - levels predicted by 2100) and reduced salinity (~80%) for up to 18 months. The key physiological questions are whether the 2 species will be able to adjust their physiology to continue to function optimally, and whether these adjustments are metabolically costly and can be maintained over time. The key ecological questions will be whether these costly changes compromise individual fitness and performance with the potential to compromise population size. A project studentship will run in parallel to the main project and allow us to investigate the effects of high pCO2 and low salinity on the more vulnerable larval stages of three species of brachyuran crabs, C. maenas, C. pagurus and Necora puber. The studentship will investigate changes in larval development and performance which could impact larval recruitment, and will therefore identify potential population bottlenecks.

This proposal represents the results of an on-going collaboration between researchers at Bangor and Southampton. These research teams are involved in a number of national and international OA research projects, but have identified that our limited understanding of the interaction of pCO2 and salinity, plus the lack of information on the responses of marine crustaceans to OA, is a weakness of existing research effort.

Impact Summary
As the outcome of the research will inform on the vulnerability of an ecologically important species of marine crab Carcinus maenas, and a commercially important species Cancer pagurus, the work could potentially impact on a range of end-user communities. Several potential users of the research have been identified and are detailed below. They include beneficiaries/stakeholders with a keen interest in the consequences and impacts of climate change on the natural environment and on marine species in particular.
Industry: End-user communities include the shellfish industry, commercial aquaculture concerns, and their trade associations. Specific end-users on a local scale include the Southern Inshore Fisheries and Conservation Authority (IFCA) and on the national level, New Under Ten Fishermens Association (NUTFA), The Shellfish Association of Great Britain and Seafish Industry Authority. All four associations support the sustainable development of the shellfish industry, and have a keen interest in the impact of climate change on shellfish stocks. Seafish, for example, supports the shellfish industry for a sustainable, profitable future. Shellfish (crustaceans and bivalves) landings currently account for 50% of total fish landings in the UK, and the edible crab Cancer pagurus is particularly important to the shellfish industry in Wales. For instance, edible crab landings in Wales of just over 500 tonnes were worth £1 million in 2006. The outputs from the intended research would aid towards management plans as they would inform on the survival prospects of Cancer pagurus under future changes in OA and salinity.

Government: Key government beneficiaries include Local Authorities, The Welsh Assembly Government, Welsh Assembly Government/ Fisheries, DEFRA, DECC and the Environment Agency. The research has the potential to influence and inform policy in the establishment of minimum standards for environmental protection and on common fisheries policy. More specifically, the work will be of relevance to shoreline management plans which are currently being developed by EA and local authorities by informing on species and habitats that may be vulnerable. This will lead to a better understanding on how coastal processes can be managed. More generally, the work will be used to increase our understanding and awareness of climate change issues, one of the key strategies for The Welsh Assembly Government, and feed into policy guidelines for future fisheries management.
Conservation agencies: Beneficiaries include Countryside Council for Wales, Nature England and Joint Nature Conservation Committee. The work will lead to effective implementation measures by informing on how survival prospects of the 2 crab species are affected by climate change.
Charities: The work will be of interest to local and national charities by informing on the survival prospects of two marine crab species. Local charities in Wales include those actively involved in marine conservation and the promotion of public awareness relating to UK wildlife and its natural environment. These include: North Wales Wildlife Trust, Marine Awareness North Wales, Dorset Wildlife Trust and Hampshire and Isle of Wight Wildlife Trust.
Education sector and general public: Climate change is a contemporary problem. It is very topical and therefore of wide general interest, even though recent statistics gathered by Welsh Assembly shows that less people in Wales believed in climate change in 2009 than in 2008. The outputs from the intended research can be used as a basis to raise awareness and increase understanding of the issues surrounding climate change to engage school-age children, students, and members of clubs and societies with an interest in environmental issues, as well as the wider public.

Impact Activities to engage with the key beneficiaries are provided in Pathways to Impact.