Physiological effects of global climate change on common British marine invertebrates

Abstract

Abstract: Climate change is likely to have profound effects on marine animals due to the predicted increases in water temperature and acidity. Many studies have examined the effects of these elevated temperatures and decreased pH at the extreme temperatures expected in the summer season, but few studies have investigated how climate change may affect animals in the winter. In this study, we investigate the effects of both winter and summer temperatures on the growth rates, body composition and metabolic rate of four species of intertidal marine invertebrates: two calcified (common mussel - Mytilus edulis and edible periwinkle – Littorina littorea) and two non-calcified (beadlet anemone – Actinia equina and sea squirts – Ascidiella aspersa) species. Samples divided to two groups, one group exposed to winter temperature condition and the second group exposed to summer temperature condition. Following a period of acclimatization during which temperature was gradually increased and pH decreased, animals were exposed to the predicted climatic conditions of 2050 (TR 2050) and 2100 (TR 2100) for six weeks. During the study period, the mortality rates were monitored as well as growth rates by taking body weight, buoyant weight and body morphometrics (length and Width). At the end of experiments, body composition were measured by taking water content, dry shell and dry body weight weight, fat content and C:N ratio. In addition, metabolic rates were measured using a closed-system respirometry. During the experiments, seawater parameters such as acidity, temperature, salinity and dissolved oxygen were measured. The results of the experiments found that there was a significant increase in mortality of A. aspersa at the higher temperatures and water acidity in winter. Furthermore, growth rates of A. equina and A. aspersa were significantly reduced at TR 2050. On the other hand, it was observed that the C:N ratio of L. littorea was significantly increased at TR 2050 and that metabolic rate was significantly higher at TR 2100. However, under summer conditions, L. littorea there was a significant decrease in buoyant weight at TR 2050. While there was no mortality amongst A. equina, a significant reduction growth was found at elevated temperature and decreased pH level. The results in this study indicate that inter-species responses to environmental changes are likely to differ but also that the inter-species response will also vary depending on the season and life stage of the animal.