Picture the Grand Canyon in Arizona - then place it under the sea: the Mediterranean seafloor is criss-crossed with deep submarine canyons that in sheer size put their land counterpart to shame. Rivers of dense waters flow through these canyons, their capacity varying depending on climate-induced phonomena.During such an event, the amount of water transported in 4 months from the Gulf of Lion to the deep Western Mediterranean via the Cap de Creus canyon equalled 2 years of input from all rivers draining in the Mediterranean.
How these dense shelf water cascading in the Gulf de Lion affect the population of the deep sea shrimp Aristeus antennatus, the most valuable deep-sea living resource in the Mediterranean Sea, was recently discovered by Spanish researchers. Initially, the strong currents (up to 80 cm/sec) displace shrimp populations from the normal fishing grounds, producing a temporary fishing collapse. However, the food provided by the currents soon leads to a large increase in recruitment - which results in plentiful landings of large shrimps 3-5 years after major cascading events.
These new findings resolve the paradox of a long-overexploited fishery that has not collapsed after 70 years of intense deep-sea trawling. But climate change is expected to cause a decrease of winter deep water formation in the Gulf de Lion, which in turn could decrease the frequency and intensity of dense shelf water cascading events. Without this regenerative mechanism, fishery pressure could quickly deplete the stock of Aristeus antennatus and other valuable deep-sea living resources in the area.
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For more information:
Company et al (2008) Climate influence on deep sea populations. PLoS ONE 3(1): e1431.
Eureka alert press release (Jan 15th 2008)
