February 1st to 5th 2016
Olhão, Portugal
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Long-term changes in the occurrence of intertidal seaweeds in NW Iberia

Scientific Exhibition
Future Oceans
Wednesday, February 3, 2016 -
18:30 to 20:00

Piñeiro-Corbeira, C. 1 Barreiro, R. 2 Cremades, J. 3

1University of A Coruña; Facultad de Ciencias; Departamento de Biología Vegetal, Animal y Ecología
2University of A Coruña; Facultad de Ciencias; Departamento de Biología Vegetal, Animal y Ecología
3University of A Coruña; Facultad de Ciencias; Departamento de Biología Vegetal, Animal y Ecología

Recent surveys of the European Atlantic coastline have revealed changes in the composition of seaweed assemblages that may be linked to global change over the last years. Nonetheless, the intricate coastal profile of Atlantic Europe and the large upwelling system off western Iberia suggest that the susceptibility to global change may be different from one region to another. In particular, NW Iberia has been an important omission because no study has systematically evaluated long-term changes in a large number of species. Here, we assessed the changes in the occurrence of 33 perennial seaweeds in NW Iberia by surveying 36 intertidal sites in 1998-99 and in 2014. We found a significant decline in the average number of species per site, particularly in semi-exposed and semi-sheltered sites, that involved red and brown algae alike. Although most of the species were less frequent in 2014, the largest drops involved kelps, fucales, and some carrageenan-producing red algae. Parallel analyses of environmental data revealed significant upward trends in sea surface temperature, near-surface air temperature (summer only) and, strong waves (frequency). In agreement with a weakening of the Iberian upwelling, nitrate and phosphate concentrations showed statistically significant, but very mild, downward trends. Our results agree with similar studies of subtidal assemblages in other regions of the European Atlantic, suggesting that the drivers of these changes may be likewise ubiquitous. Further surveys will be required to tell global from local impacts, and long-term trends from transitory fluctuations. Nonetheless, the regular monitoring of intertidal perennial seaweeds seems as a cost-effective tool for this job.
keywords: 
NW Iberia; Global change; Intertidal; Perennial seaweeds

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