Biological Impacts Item 5

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El Nino's effect on the Southern California marine system.

Item 5  30-MAR-1998 15:39 Susan E Yoder (syoder)

Hi, this is Sue Yoder again.  I attended an interesting conference last saturday regarding long-term changes in marine systems in Southern California, hosted by the Wrigley Institute.  Some interesting information was presented on how El Nino's can affect species abundance in our region.  

The marine realm of Southern California lies in a transitional area where the cold California current moving downcoast from Alaska meets the warm subtropical waters moving upcoast.  This is one reason why we have a high diversity of marine life.  It also means that changes in oceanic circulation in the Eastern Pacific can have immediate impacts locally, and the system is dynamic.  

Since 1976, the oceanic system has changed off our coast.  Surface water temperatures are somewhat warmer...about 1 1/2 degrees C I think.  We have also seen a precipitous decline in Zooplankton abundance, and some warm water tropical species are increasing in abundance while species that are more adapted to the California current cold temperature are in decline. Is this connected with Global Warming?  None are sure at this time.  

So where does the El Nino come into this picture?  It seems to act a stressor on the cold water adapted species, hastening there demise in the face of this more longer term oceanic change.  Our kelp forest for example grows best in cold waters because they are more nitrate rich (there is an inverse relationship between water temperature and dissolved nitrate in the ocean).  El Nino storms not only rip the holdfasts from their grip on the rocky bottom, they are warmer and more sterile of nitrates.  Our kelp forest usually recovers from such event by recruiting new young kelp plants.  But recruitment after El Ninos has been low lately, and the growth rate of giant kelp is also down. Giant Kelp has disappeared below Punta Bresario and is less abundant on its old sites in the Southern California.  

Giant Kelp (Macrocystis) is a keystone species in the Southern California region, providing food and shelter for a large diversity of marine life, a true underwater forest.  El Ninos appear to be hastening its demise in the face of these new oceanic conditions.

5:1) 01-APR-1998 19:53 Cathleen Cannon (ccannon)

  The effect El Nino is having on the kelp forest is of great interest to me, as I live and teach in Northern California.  (I also LOVE our biologically diverse coast.)
  I do not know what you mean when you say "...recruiting  new kelp plants."  What does it mean to recruit if you are a Kelp??                      Thanks,        Cathleen

5:2) 06-APR-1998 00:00 Charlene I. Branch (cbranch)

Since there are several studies for biological changes on the coast are there more through out the US past the Rockies?  Our bird migration was early this year and the eagles appear to be nesting further south.

5:3) 08-APR-1998 16:09 Susan E Yoder (syoder)

Recruitment is a population biologists term for population growth, which can occur by migration or by reproduction.  In this case it means reproduction.  

I do not know what studies are being done in the Eastern US.  You might contact the Raptor Research Group associated with US Fish and Wildlife for more information on eagles.

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