Composition and structure of phytoplankton communities in coastal environments with anthropogenic disturbance (Patagonia, Argentina)

Abstract

The purpose of this study is to review as well as to compare environmental and phytoplankton data collected from coastal Patagonian ecosystems (Argentina) located at different latitudes and exposed not only to freshwater discharges (Chubut river in Chubut province, Deseado river in Santa Cruz province, Pipo and Olivia rivers in Tierra del Fuego province) but also to urban, industrial, and port activities related to the main cities on the Patagonian coast. The data analyzed were collected during the spring, summer, and fall of 1993, 1994, and 2001. The presence of Bacillariophyta, the dominant phylum in most environments, is the main characteristic of the composition and structure of phytoplankton community in the study area. A total of 127 taxa were identified, 9 of which are known to be potentially toxic species. Taxa richness was found to be highest in Nueva and Engaño Bays, the order of abundance being 106 cells L-1 in the majority of the environments of our study area. Blooms of Alexandrium tamarense and Pseudo-nitzschia cf. pseudodelicatissima were recorded in Nueva Bay in the summer of 1993, whereas blooms of Skeletonema costatum were recorded in Deseado Ría in the fall of 1994. Maximum biomass was recorded in Ushuaia Bay with 10 μg/L Chl a. N:P ratios indicated nitrogen limitation in the majority of the environments analyzed. Changes in the structure of the microalgal community, bloom occurrence, and the presence of organisms indicating environmental alterations associated with eutrophication events in the coastal zones could all be bioindicators of changes in water quality and incipient eutrophication processes in the studied environments.