Vigo is leading a pioneering project in Spain to determine the risks and effects that climate change is already causing in Galician shellfish banks and whose ultimate objective is to develop a prediction system that alerts the guilds to the arrival of heat waves and floods. The study also aims to know the effect of these extreme episodes on resources, so that the guilds and the Xunta could adopt solutions adapted to each situation and avoid mortalities.
The study has national funding -177,870 euros until 2017- and is coordinated by Professor of Zoology Elsa Vázquez. Two experts from the American University of South Carolina, Sally Woodin and David Wethey, and five brotherhoods of the province -Redondela, Carril, Campelo and Cambados- also collaborate, in addition to having the support of the Consellería do Mar. Woodin and Wethey are experts in mathematical models and lead a project funded by NASA to study the effects of global warming in areas around the planet that exploit their shellfish resources: “Galicia is one of the few areas with historical data and we have been collaborating with them for several years.”
In Galicia, what is already happening with climate change, and what the IPCC predicts, is an increase in torrential rains and heat waves. According to Vázquez, the clam can withstand heat peaks and drops in salinity, but maintaining these conditions for a long time produces massive mortality. One hypothesis is that each of the species will be affected differently, since they live in different areas of the bank. Thus, the greatest mortality due to heat will affect the Japanese clam, since it is buried at a shallower depth. The consequences also vary depending on physiological evolution, as detected by the shellfishers themselves, who know that when the fine clam is reproducing, it dies immediately if a heat wave occurs.
The prediction model will be based on current temperature and salinity data and on mathematical models, in the style of Meteogalicia. In order to develop these models, the EcoCost group will develop experiments over the next two years with the three types of clam of commercial interest -fina, slug and Japanese clam – both in the sands and in the laboratories of the Toralla Marine Science Station (Ecimat). The aim is to find out the mortality and the effects on the vital functions that extreme events have on each of these species. On the one hand, the biologists study the mortality and growth of the clams in boxes located in the sands, where temperature and salinity are measured with CTD devices. The first clams were seeded in July and sampling will be carried out monthly and every time a flood or heat wave occurs. The effects will also be studied in the laboratory, where both water and air temperature and salinity will be modified to simulate the extreme events that can occur at each time of the year, while mortality and sublethal effects such as the consequences on reproduction, growth or the stress level of individuals will be studied. To do this, biologists will measure oxygen consumption, study the gonads and proteins that are generated in episodes of stress, evaluate feeding rates and even detect the movement of the clams while they are buried in the sand, thanks to a system of pressure sensors and electrodes developed by Woodin and Wethey, which allows the stress level of the bivalve to be known without removing it from its environment. These experiments have already begun at the Toralla Marine Science Station (Ecimat), where the group has isothermal chambers where the tides, heat waves and torrential rains that occur in the natural environment are simulated.
With the results obtained, the temperature and salinity threshold that each species can withstand in the different stages of its evolution will be known. Combining these results with mathematical models of oceanographic prediction, it will be possible to predict the percentage of mortality in a given bank 5 or 7 days in advance and even whether these changes will cause the bank to move from the intertidal to the subtidal zone in the long term, anticipates Vázquez.
