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Nearshore Ocean Ecosystems affected by delay in upwelling


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Posted by on March 30, 2007 at 14:19:54:

A collaboration of scientists recently released an analysis of the effects of upwelling on west coast nearshore coastal ocean ecosystems during the summer of 2005. The study, “Delayed Upwelling Alters Nearshore Coastal Ocean Ecosystems in the Northern California Current,” was published in the Proceeding of the National Academy of Sciences (Vol. 104, No.10, at 3719-24). During the summer of 2005, a southward shift in the jet stream was observed in the Pacific Ocean off of the west coast. In conjunction with the jet stream shift, researchers also observed a particularly significant delay in upwelling in the northern California Current Large Marine Ecosystem (CCLME).

The research team collected data from a variety of long-term physical, chemical, and biological measurements to determine the ecosystem effects of the delayed upwelling. Previous research determined that decreases in upwelling, as seen when upwelling is delayed, can lead to a decrease in nutrient supply and/or a reduction in movement of planktonic organisms and planktonic life stages. Results demonstrated: an increase in water temperature; a reduction in nutrient levels; a decrease in primary productivity; and an unusually low level of rocky inter-tidal larval recruitment. The data components combine to explain that the upwelling was delayed due to a shift in the jet stream, which delayed the characteristic delivery of nutrients and cold water, which greatly altered the availability of food sources for numerous organisms throughout the marine food web. The effects of the delayed upwelling were seen in a reduction of larval recruitment for key inter-tidal organisms as well as reproductive failures in Cassin auklets, a planktivorous seabird.

The breadth of effects from a month delay in upwelling lead the research team to hypothesize that numerous other marine organisms were negatively affected by the delay. Salmon are anadromous fish that rely heavily upon plankton as a food source during their adult life stage in the ocean. Such a large-scale reduction in food availability following the delay in upwelling off the coast of California could have had unprecedented impacts on the growth and development of adult salmon in the ocean. We devote a large amount of our resources for salmon recovery to in-stream habitat restoration (an important factor in salmon health) but should also be focusing some resources on learning more about the oceanic conditions that effect salmon population health as well, especially considering that climate scientists predict that global warming will result in stronger upwelling events whose timing will be more sporadic than their historic temporal pattern. A copy of the PNAS article is available at www.pnas.org/cgi/reprint/104/10/3719?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&fulltext=delayed+upwelling&searchid=1&FIRSTINDEX=0&resourcetype=HWCIT.



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