Distribution of phytoplankton pigments and particulate organic carbon in the coastal waters of Visakhapatnam (Bay of Bengal)

Abstract

Phytoplankton pigments and particulate organic carbon (POC) revealed temporal and spatial variations in the coastal waters of Visakhapatnam. Chlorophyll-a (chl-a) and POC exhibited major peaks in pre and postmonsoon seasons which were attributed to higher planktonic production as a result of upwelling in the former, and favourable marine conditions in the latter. The integral mean concentration (IMC) of chl-a showed a decreasing trend from coast to offshore indicating higher fertility near the coast. A subsurface maximum (10-20 m depth) was observed with chl-a and POC coinciding with the biomass.maximum. Lower ratios of chl-b, chl-c and phaeopigments with chl-a suggested their healthy physiological state. Detritus (carbon) in POC ranged from 90.8 to 97.5% indicating its dominance over living phytoplankton carbon.