Delayed upwelling alters nearshore coastal ocean ecosystems in the northern California current.
Wind-driven coastal ocean upwelling supplies nutrients to the euphotic zone near the coast. Nutrients fuel the growth of phytoplankton, the base of a very productive coastal marine ecosystem [Pauly D, Christensen V (1995) Nature 374:255-257]. Because nutrient supply and phytoplankton biomass in shelf waters are highly sensitive to variation in upwelling-driven circulation, shifts in the timing and strength of upwelling may alter basic nutrient and carbon fluxes through marine food webs. We show how a 1-month delay in the 2005 spring transition to upwelling-favorable wind stress in the northern California Current Large Marine Ecosystem resulted in numerous anomalies: warm water, low nutrient levels, low primary productivity, and an unprecedented low recruitment of rocky intertidal organisms. The delay was associated with 20- to 40-day wind oscillations accompanying a southward shift of the jet stream. Early in the upwelling season (May-July) off Oregon, the cumulative upwelling-favorable wind stress was the lowest in 20 years, nearshore surface waters averaged 2 degrees C warmer than normal, surf-zone chlorophyll-a and nutrients were 50% and 30% less than normal, respectively, and densities of recruits of mussels and barnacles were reduced by 83% and 66%, respectively. Delayed early-season upwelling and stronger late-season upwelling are consistent with predictions of the influence of global warming on coastal upwelling regions.
Barth
John A
JA
College of Oceanic and Atmospheric Sciences and Department of Zoology, Oregon State University, Corvallis, OR 97331, USA. barth@coas.oregonstate.edu
Menge
Bruce A
BA
Lubchenco
Jane
J
Chan
Francis
F
Bane
John M
JM
Kirincich
Anthony R
AR
McManus
Margaret A
MA
Nielsen
Karina J
KJ
Pierce
Stephen D
SD
Washburn
Libe
L
D000818:Animals; D018533:Biomass; D002140:California; D002244:Carbon / Q000378:metabolism; D002734:Chlorophyll / Q000737:chemistry; D000077194:Chlorophyll A; D004463:Ecology; D017753:Ecosystem; D020387:Food Chain; D008386:Marine Biology / Q000379:methods*; D049878:Mytilus; D009792:Oceans and Seas; D009922:Oregon; D010839:Phytoplankton; D013696:Temperature; D001468:Thoracica
D002734:Chlorophyll; D002244:Carbon; D000077194:Chlorophyll A