IADO   05364
INSTITUTO ARGENTINO DE OCEANOGRAFIA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
MICROZOOPLANKTON AS AN IMPORTANT TROPHIC MODULATOR OF PHYTOPLANKTON PRODUCTION IN A HIGHLY TURBID AND EUTROPHIC ESTUARY IN SOUTH AMERICA
Autor/es:
LÓPEZ ABBATE, M.C., BARRÍA DE CAO, M.S., GUINDER, V. A., PETTIGROSSO, R. E. Y HOFFMEYER, M. S.
Lugar:
Figueira da Foz
Reunión:
Simposio; Estuarine & Coastal Sciences Association, Integrative tools and methods in assessing ecological quality in estuarine and coastal systems worldwide (ECSA 47); 2010
Institución organizadora:
Institute of Marine Research (IMAR, University of Coimbra) y Centre of Oceanography (CO, University of Lisbon)
Resumen:
Estuaries are productive marine-coastal environments that are crucial points for the development of diverse human activities. This poses potential impacts for those ecosystems, such as nutrient enrichment that generally leads to changes in the dynamics of local food webs. The Bahía Blanca Estuary (BBE) is a highly turbid and eutrophic environment that holds a rich biological community. The microzooplankton has been perceived as highly abundant and mainly represented by tintinnids and aloricate ciliates. Thus, it is expected that microzooplankton plays a key role in the control of phytoplankton standing crop in the estuary. Here, we estimated the grazing impact of microzooplankton through the dilution technique, in two areas of the BBE with different nutrient loading and during contrasting seasons as for hydrographic conditions and chlorophyll-a concentration; winter and spring. The sampling stations were located in the inner-intermediate area of the estuary; the station with high nutrient loading (HN) was severely affected by the main city sewage discharge whereas the other station (LN) was situated in a less affected tidal channel with significant lower nutrient concentrations. Phytoplankton was always dominated by small diatoms and showed higher biomass during winter. In HN, the phytoplankton growing rate (k) was higher than in LN in both seasons. Tintinnids were usually the dominant consumers, although aloricate ciliates were important in HN. The microzooplankton grazing rates (g) were moderate to high (ranged between 0.7 – 1.4 d-1) with maximum values in HN, and followed phytoplankton growth. Conversely, the consumer diversity tended to be lower at HN, probably related to extremely high nutrient levels that might affect the development of some protists. The grazing rates were comparable with those found in other productive temperate estuaries worldwide. Our results showed that microzooplankton represents an important link in the trophic web of the BBE, presenting significant grazing rates on phytoplankton standing crop during winter and spring. Further detailed studies on nutrient ratios dynamics, species-specific interactions and grazing pressure should be carried out to disentangle direct and indirect effects of microzooplankton grazing on phytoplankton structure and their potential cascading effects throughout the pelagic food web.