THE STATE OF THE CALIFORNIA CURRENT, 2007-2008: LA NINA CONDITIONS AND THEIR EFFECTS ON THE ECOSYSTEM

Citation:
McClatchie, S, Goericke R, Koslow JA, Schwing FB, Bograd SJ, Charter R, Lo WWN, Hill K, Gottschalck J, L'Heureux M, Xue Y, Peterson WT, Emmett R, Collins C, Gaxiola-Castro G, Durazo R, Kahru M, Mitchell BG, Hyrenbach KD, Sydeman WJ, Bradley RW, Warzybok P, Bjorkstedt E.  2008.  THE STATE OF THE CALIFORNIA CURRENT, 2007-2008: LA NINA CONDITIONS AND THEIR EFFECTS ON THE ECOSYSTEM. California Cooperative Oceanic Fisheries Investigations Reports. 49:39-76.

Date Published:

Nov

Keywords:

birds, current system, marine, recruitment, rockfish sebastes, sardine sardinops-sagax

Abstract:

The state of the California Current system (CCS) between Oregon and Baja California is summarized in this report, covering spring of 2007 to winter/spring 2008. The 2006-07 period began with moderate El Nino conditions which decayed rapidly in early 2007. By summer 2007, a moderate-to-strong La Nina had developed. The North Pacific sea surface temperature (SST) anomalies displayed a negative pattern of Pacific Decadal Oscillation with below-normal SSTs in the California Current and Gulf of Alaska consistent with this pattern. The region experienced anomalously strong southward coastal winds, leading to positive anomalies of the West Coast upwelling index, in Strong contrast with 2005. The 2007 upwelling season also began early (in contrast to delayed onset in 2005 and 2006) and remained unseasonably strong through May. The cumulative upwelling for the 2007 season was greater than normal in the southern portion of the California Current system. Despite the La Nina conditions, nitrate and chlorophyll concentrations off Oregon were about average in 2007. On the other hand, copepod biomass rebounded strongly in 2006 after the exceptionally low biomass in 2005, and copepod species richness in 2006 was low, also indicating transport Of sub-arctic water into the northern California Current in 2006-07, which is relatively productive but low in diversity. Anomalously high salinities at 200 in depth were also observed during CalCOFI and IMECOCAL cruises off Southern and Baja California. In the CalCOFI area, where there has been a general trend toward a deepening mixed layer, the mixed layer responded to this year's La Nina conditions by shoaling. Nitrate (but not silicate and phosphate) concentrations in the mixed layer were anomalously high, but chlorophyll concentrations were about average, except for spring 2007, which was one of the lowest values on record. Spring chlorophyll a concentrations are notably variable during La Ninas. In the northern California Current, forage fish and predatory fish abundance remained low in 2007. In the southern California Current, Pacific sardine (Sardinops sagax) larval abundance was relatively high and distributed in relation to the inner edge of the California Current and the edge of an eddy. Northern anchovy (Engraulis mordax) larvae were relatively low in abundance, apparently related to a large downwelling feature. Reproductive success of all six seabirds monitored on Farallon Island was recovering slowly this year, following the previous two disastrous seasons. However, cluster analysis indicated that reproductive success is still relatively low. The cold-water planktivorous auklets (Ptychoramphus aleuticus) continued to be found at high densities in Southern waters. Overall, the transition in 2007 to La Nina conditions appeared to contribute to average to above average productivity in the California Current, but the physical, chemical, and biological (phytoplankton, zooplankton, Fish, and seabird) indices of productivity were far from consistent.

Notes:

n/a

Website