CADIC   02618
CENTRO AUSTRAL DE INVESTIGACIONES CIENTIFICAS
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Changes on sediment accumulation rates within NW Mediterranean submarine canyons caused by bottom trawling activities
Autor/es:
PUIG, P.; MASQUÉ, P.; MARTÍN, J.; PARADIS, S.; JUAN, X.; TORO, M.; PALANQUES, A.
Lugar:
SORRENTO
Reunión:
Taller; 47th International Workshop of the Mediterranean Science Commission (CIESM); 2015
Institución organizadora:
CIESM
Resumen:
The physical disturbance of the marine
sedimentary environments by commercial bottom trawling is a matter of concern. The
direct physical effects of this fishing technique include scraping and
ploughing of the seabed and increases of the near-bottom water turbidity by
sediment resuspension. However, the quantification of the sediment that has
been resuspended by this anthropogenic activity over years and has been
ultimately exported across the margin remains largely unaddressed. The analysis
of sediment accumulation rates from sediment cores collected along the axes of
several submarine canyons in the Catalan margin (northwestern Mediterranean)
has allowed to estimate the contribution of this anthropogenic activity to the
present-day sediment dynamics. 210Pb chronologies, occasionally
supported by 137Cs dating, indicate a rapid increase of sediment
accumulation rates since the 1960-70s, in coincidence with a strong impulse in
the industrialization of the trawling fleets of this region. Such increase has
been associated to the enhanced delivery of sediment resuspended by trawlers from
the shelves and upper slope regions towards the canyon?s interior, and to the rapid
technical development at that time, in terms of engine power and gear size.
This change has been observed in La Fonera (or Palamós) Canyon at depths
greater than 1700 m, while in other canyons it is restricted to shallower
regions (~1000 m in depth) closer to fishing grounds. Two sampling sites from
La Fonera and Foix submarine canyons that exhibited high sediment accumulation
rates (0.6-0.7 cm y-1) were reoccupied several years after the first
chronological analyses. These two new cores reveal a second and more rapid
increase of sediment accumulation rates in both canyons occurring circa 2000
and accounting for values >2 cm y-1. This second change at the
beginning of the XXI century has been attributed to a preferential displacement
of the trawling fleet towards slope fishing grounds surrounding submarine
canyons, and also to technical improvements in trawling vessels, presumably
related to subsidies and aids provided by the European Commission to the
fishing industry.