Coronavirus Information for the UC San Diego Community

Our leaders are working closely with federal and state officials to ensure your ongoing safety at the university. Stay up to date with the latest developments. Learn more.

Climate-ecosystem change off southern California: Time-dependent seabird predator-prey numerical responses

TitleClimate-ecosystem change off southern California: Time-dependent seabird predator-prey numerical responses
Publication TypeJournal Article
Year of Publication2015
AuthorsSydeman WJ, Thompson S.A, Santora J.A, Koslow JA, Goericke R, Ohman MD
JournalDeep-Sea Research Part Ii-Topical Studies in Oceanography
Date Published2015/02
Type of ArticleArticle
ISBN Number0967-0645
Accession NumberWOS:000350921700014
Keywordscurrent system; diet; food-web; Krill; long-term trends; marine ecosystems; Mesopelagic fish; Negative binomial models; northeast pacific; Northern anchovy; ocean climate; Rockfish; seabirds; stratification; Time series; top predators; trophic levels; Upwelling; variability

Climate change may increase both stratification and upwelling in marine ecosystems, but these processes may affect productivity in opposing or complementary ways. For the Southern California region of the California Current Ecosystem (CCE), we hypothesized that changes in stratification and upwelling have affected marine bird populations indirectly through changes in prey availability. To test this hypothesis, we derived trends and associations between stratification and upwelling, the relative abundance of potential prey including krill and forage fish, and seabirds based on the long-term, multi-disciplinary CalCOFI/CCE-LTER program. Over the period 1987 through 2011, spring and summer seabird density (all species combined) declined by similar to 2% per year, mostly in the northern sector of the study region. Krill showed variable trends with two species increasing and one deceasing, resulting in community reorganization. Nearshore forage fish, dominated by northern anchovy (Engraulis mordax) as well as offshore mesopelagic species, show declines in relative abundance over this period. The unidirectional decline in springtime seabird density is largely explained by declining nearshore fish abundance in the previous season (winter). Interannual variability in seabird density, especially in the 2000s, is explained by variability in krill abundance. Changes in the numerical responses of seabirds to prey abundance correspond to a putative ecosystem shift in 1998-1999 and support aspects of optimal foraging (diet) theory. Predator-prey interactions and numerical responses clearly explain aspects of the upper trophic level patterns of change in the pelagic ecosystem off southern California. (C) 2014 Elsevier Ltd. All rights reserved.

Student Publication: