Near-surface phytoplankton distribution in the western Intra-Americas Sea: The influence of El Nino and weather events

摘要

The space-rime variation of phytoplankton pigments in the western Intra-Americas Sea (IAS), in the vicinity of the island of Cuba, is examined using digital images obtained with the Coastal Zone Color Scanner sensor flown aboard the Nimbus 7 satellite from 1978 to 1986. The results are compared to historical in situ hydrographic observations. A marked seasonality in pigment concentration was observed in waters around Cuba, with an average of 0.07 mg m(-3) in summer (April-September) and 0.13 mg m-3 during winter (October-March). The range of variation in pigment concentration was larger in the Gulf of Mexico relative to the western Caribbean Sea. We identified four biogeographical areas on the basis of groups of pixels with similar patterns of time variability. These are area I: southwest of Cuba, Yucatan Channel, and Florida Strait; area II: central Gulf of Mexico; area III: east of Cuba; and area IV: central Caribbean Sea, south of Jamaica and Hispaniola. Two major meteorological events led to anomalies in the seasonal cycle of pigment concentrations. During El Nino-Southern Oscillation (ENSO) of 1982-1983, positive anomalies were observed in the pigment concentration in the western IAS during winter months. This was associated with intense mixing of the water column by higher-frequency and stronger winds associated with cold fronts. ENSO 1952-1983 therefore had a fertilizing effect on the IAS region. Another positive anomaly was observed in 1980-1981, a non-ENSO period that featured higher hurricane and extratropical low-pressure activity. [References: 61]