Particulate suspended matter concentrations in the Bahía Blanca Estuary, Argentina: implications for the development of phytoplankton blooms.

GUINDER, V. A.; POPOVICH C. A; HELBLING, W. E.; PERILLO. G. M. E.

Instituto Argentino de Oceanografía (IADO) Bahía Blanca, Argentina

Congreso; Science and management of estuaries and coasts: A tale of two hemispheres; 2008

IADO

The inner zone of the Bahía Blanca Estuary is turbid and strongly affected by tidal energy and winds that result in a high concentration of suspended sediment. The phytoplankton community is mostly characterized by diatoms and had recurrent winter-early spring blooms.  Sampling of total particulate suspended matter (PSM), particulate organic matter (POM) and light extinction coefficient (k) in the water column were fortnightly measured, and weekly during the blooming period, in a fixed station from January 2007 to February 2008. Phytoplankton abundance, biomass and chlorophyll a concentrations were also measured. The POM concentrations were significantly correlated with the phytoplankton biomass (Spearman’s correlation: 0.701, p < 0.01) and both, POM and biomass, had maximal values during winter (21.8 mg/L and 393.5 µgC/L, respectively) and mid summer (24.3 mg/L and 407.0 µgC/L, respectively) with cellular abundances up to 8 x106 cells/L and chlorophyll a up to 24.55 µg/L. On the other hand, PSM concentrations and k values were significantly correlated (Spearman’s correlation = 0.731, p < 0.01) and they showed relatively lower values during the phytoplankton maximal biomass values. During winter, PSM and k reached minimal values (23.6 mg/L and 0.17 m-1, respectively), that were significantly less (Mann-Whitney test, both p < 0.01) than their respective annual mean of 77.6 mg/L and 2.94 m-1. Our results suggest that the diminution of PSM concentrations in the water column with a concomitant increase in the penetration of solar radiation seems to be one of the factors necessary for the phytoplankton blooms to occur.   Key words: Particulate suspended matter, light availability, phytoplankton bloom, temperate estuary Exposición oral