Biological Consequences of the 1975 El Niño

摘要: The weak El Nino event of 1975 had a clearly defined effect on the biological productivity southeastern tropical Pacific. During February and March 1975, warm (27°C) water low salinity (33.5 parts per thousand) nutrient content extended south across equator east Galapagos Islands, replacing nutrient-rich normally supplied by equatorial upwelling. Equatorial primary production was less than 0.2 gram carbon square meter day, one-fifth normal value. At maximum development event, coastal region Peru continued to have strong nearshore upwelling with values greater 2.5 grams although zone high confined 250-kilometer-wide band, one-half its width. effects were short-lived; in April May begun reestablish levels production.