Megafauna
A large number of studies have found climate change-related changes in the abundance, spatial range and phenology of numerous marine organisms over recent decades and a certain amount of movement of sea birds and cetaceans in the Atlantic. This indicator includes cetacean and sea bird species in the Bay of Biscay, and integrates estimates of their abundance and spatial distribution.
- Ocean warming has caused changes in the abundance, distribution, phenology and reduction in size of numerous marine species over the last few decades.
- The maintenance and analysis of the time series of the sea bird and cetacean community in the Bay of Biscay will make it possible to assess the current impact of climate change on these vulnerable communities.
Relationship of the indicator to climate change
Global ocean warming over the last few decades has increased interest in studying how rising temperatures are affecting the spatio-temporal patterns of marine communities. A large number of studies have found climate change-related changes in the abundance, spatial range and phenology of numerous marine organisms over recent decades (Poloczanska et al., 2013), and a certain amount of movement of sea birds and cetaceans in the north-east Atlantic (Luczak et al., 2011, Hemery et al., 2007).
The sea bird community time series is not yet long enough to capture climate variability and its impact on the sea bird community. Meanwhile, the evolution of the abundance and distribution of common dolphins (Delphinus delphis) in the Bay of Biscay between 1994 and 2018 was specifically studied using data from these surveys and external collaborations to explore its possible relationship with ocean warming (Astarloa et al., 2021). To this end, the density of the species and the centre of gravity of its distribution in the Bay of Biscay were estimated and the effect of three sets of potential variables (climatic indices, oceanographic conditions and prey biomass) was analysed with a vector autoregressive spatial model (VAST) that takes different sampling efforts resulting from the combination of multiple datasets into account. The results showed that the abundance of common dolphins increased significantly in the Bay of Biscay during the study period. These changes were mainly explained by climate indices such as the North Atlantic Oscillation (NAO) and the biomass of prey species, while sea temperature was less important.
Sea birds and cetaceans in the Bay of Biscay.
The Bay of Biscay megafauna census has been carried out since 2013 and provides time series data on the community of sea birds and cetaceans to study the impact of climate change on these apex predator communities.
The JUVENA oceanographic campaign takes place every September with the aim of assessing the European anchovy population and the abundance of other pelagic species in the Bay of Biscay (Boyra et al., 2013). Since 2013, apex predators have been sighted by a team of three experienced observers, following the distance sampling methodology (Buckland et al. 2001): 2 observers at a time search for cetaceans and sea birds ahead of the bow at an angle of 180° from a single observation platform at a height of 7.5 m above sea level.
Astarloa, A., M. Louzao, J. Andrade, L. Babey, S. Berrow, O. Boisseau, T. Brereton, G. Dorémus, P. G. H. Evans, N. K. Hodgins, M. Lewis, J. Martinez-Cedeira, M. L. Pinsky, V. Ridoux, C. Saavedra, M. B. Santos, J. T. Thorson, J. J. Waggitt, D. Wall, and G. Chust. 2021. The Role of Climate, Oceanography, and Prey in Driving Decadal Spatio-Temporal Patterns of a Highly Mobile Top Predator. Frontiers in Marine Science 8.
Hemery, G., D'amico, F., Castege, I., Dupont, B., D'elbee, J., Lalanne, Y., and Mouches, C. (2007). Detecting the impact of oceano-climatic changes on marine ecosystems using a multivariate index: The case of the Bay of Biscay (North Atlantic-European Ocean). Global Change Biology 14, 1-12.
Luczak, C., Beaugrand, G., Jaffre, M., and Lenoir, S. (2011). Climate change impact on Balearic shearwater through a trophic cascade. Biol Lett 7, 702-705.
Poloczanska, E. S., C. J. Brown, W. J. Sydeman, W. Kiessling, D. S. Schoeman, P. J. Moore, K. Brander, J. F. Bruno, L. B. Buckley, M. T. Burrows, C. M. Duarte, B. S. Halpern, J. Holding, C. V. Kappel, M. I. O’Connor, J. M. Pandolfi, C. Parmesan, F. Schwing, S. A. Thompson, and A. J. Richardson. 2013. Global imprint of climate change on marine life. Nature Climate Change 3:919-925.
