Composition and potential grazing impact of salp assemblages off Baja California during the 1997–1999 El Niño and La Niña

Salps off Baja California (BC) showed substantial changes during El Niño of 1997–1998 and La Niña of 1998–1999. Salps were particularly abundant during the warm phase and showed a decreasing trend after the transition to cool conditions (October 1998). Salp swarms (>1 salp m–3) were present throughout the study period, with the exception of October 1999 and October 2000. They appeared more frequently S of Punta Baja (30°N). The most abundant species wasThalia orientalisfollowed bySalpa fusiformis.T. orientalisdecreased in abundance from winter 1998 to autumn 1999, whileS. fusiformisshowed a strong increase during the development and establishment of La Niña (autumn 1998 and winter 1999). Other species (T. rhomboides,T. cicar,Cyclosalpa strongylenteron,C. polae,S. cylindricaandRitteriella amboinensis) associated with warmer waters were present off the southernmost part of the BC peninsula. They were probably advected into the area from the SSW by an intensified coastal poleward jet that characterized the El Niño peak in the area. Estimates of carbon ingestion from daily rations ofThaliaspp. andS. fusiformisindicated that swarms required from 100% of the daily primary production and phytoplankton biomass. Fecal pellet production of swarms of these species was estimated at between