Seasonal Succession Patterns of Phytoplankton in the Bahía Blanca Estuary (Argentina)

Abstract

The Bahía Blanca estuary is a shallow, well mixed and highly turbid ecosystem. The phytoplankton is dominated by diatoms with Thalassiosira the major genus in number of species and numerical abundance. A longterm investigation was conducted from 1978 to 1991 including measurements of phytoplankton composition and abundance and environmental factors. Principal Components Analysis (PCA), applied to two periods of four years (1978Ϫ1981 and 1988Ϫ1991) corroborated the pattern of seasonal distribution in Bahia Blanca estuary; a winter-early spring bloom as the most important event in the annual cycle. This bloom was initiated usually in late-June and extended through September. Seasonal patterns of nutrient concentrations showed a decline coinciding with the diatom bloom and peaks of high concentrations in late summer and autumn. According to the long term observations on phytoplankton and the PCA results, the most important phytoplankton taxa in Bahía Blanca estuary exhibited one of three types of seasonal patterns: very recurrent, winter-early spring blooming species, which included Thalassiosira curviseriata, T. anguste-lineata, T. pacifica, Chaetoceros spp., Skeletonema costatum; species present year-round, e. g. non-blooming species Thalassiosira hendeyi and Paralia sulcata; species with peaks of abundance in late-spring or summer, and presenting more seasonal and interannual variability including phytoflagellates, and the diatoms Cerataulina pelagica and Guinardia delicatula.

Phytoplankton-aloricate ciliate community in the Bahía Blanca Estuary (Argentina): seasonal patterns and trophic groups

“…Water samples were filtered through a Whatman GF/C to study dissolved inorganic nutrients and POM and were frozen until they could be analyzed. Levels of nitrate (NO 3 -), nitrite (NO 2 -), phosphate (PO 4 3-) and silicate were determined in accordance with the methods of TREGUER; LE CORRE (1975), GRASSHOFF et al (1983), EBERLEIN;KATTNER (1987) andTECHNICON® (1973), respectively, using a Technicon AA-II Autoanalyzer.…”

“…Taking into account that in this environment the dominant phytoplankton species form chains during the winter bloom and also that their cell ranges vary significantly around 20 µm GAYOSO, 1999), it is difficult to separate the nannoplanktonic and microplanktonic fractions as in the traditional classification of SIEBURTH et al (1978). In this study, therefore, we have used a relatively high value to establish the limit between the two fractions of phytoplankton under study.…”

“…In this estuary a mixed zooplankton assemblage dominated by the copepod Acartia tonsa showed its maximum abundance in summer (January-March) and the low densities during the phytoplankton bloom (June-August) (HOFFMEYER, 2004). A decrease in the grazing pressure is one of the mechanisms associated with phytoplankton blooms (GAYOSO, 1999) and might help to explain the presence of large-sized ciliates in winter.…”

“…Some quantitative studies have been carried out on the ciliates of the Bahía Blanca Estuary (BARRIA DE CAO, 1992;BARRIA DE CAO et al, 1997;PETTIGROSSO et al, 1997;BARRIA DE CAO, 2007), but in this area, however, no information is available about the seasonal patterns and trophic relationships of the aloricated planktonic ciliates. On the other hand, long-term phytoplankton studies indicate that a diatom winter-early spring bloom is a recurrent feature in the annual cycle and represents the most important event for the production of biomass (GAYOSO, 1998(GAYOSO, , 1999MARCOVECCHIO, 2008).…”

Long-term changes in phytoplankton phenology and community structure in the Bahía Blanca Estuary, Argentina

“…All published phytoplankton data (Gayoso 1989(Gayoso , 1998(Gayoso , 1999Pettigrosso and Popovich 2009;Popovich 1997Popovich , 2004Popovich and Gayoso 1999;Popovich and Marcovecchio 2008;Popovich et al 2008a) were compiled to compare the phytoplankton annual pattern observed in the period 2006-2008 with the one previously described in the estuary.…”