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STUDY OF MESOZOOPLANKTON DIVERSITY AS ECOLOGICAL INDICATOR OF THE ANTHROPOGENIC INFLUENCE IN TWO SUANTARCTIC BAYS
BIANCALANA, F.; HOFFMEYER, M. S.; BERASATEGUI, A. ; KOPPRIO, G. A.
Figueira da Foz
Simposio; Integrative tools and methods in assessing ecological quality in estuarine and coastal systems worldwide; 2010
IMAR-Institute of Marine Research (U.Coimbra) and CO-Centre of Oceanography (U.Lisbon)
This study focused on the use of specific diversity as ecological indicator of the variation of mesozooplankton assemblage related to the anthropogenic influence in Ushuaia Bay (UB) and Golondrina Bay (GB) (Beagle Channel, Argentina). Sampling was carried out every three months from August 2004 to June 2005. Mesozooplankton samples and measures of salinity, temperature and chlorophyll a were obtained from 22 and 7 in UB and GB, respectively. Species diversity was calculated using the Shannon-Wiener index. Seasonally, the diversity decreased in autumn-winter and increased in spring-summer. The dominance presented an opposite pattern. Ctenocalanus citer, Oithona similis and Halicarcinus planatus dominance values were between 25-45% in autumn-winter in both bays. In spring-summer, the taxa with higher dominance values (19-39%) were Podon leuckarti, Acartia tonsa and Bryozoa. The presence of Eurytemora americanastood out, which presented up to 10 % of dominance, particularly associated with a coastal zone with a certain degree of eutrophication in UB. Diversity values ranged from 1.23 (Station 2-winter) to 4.20 (station 14-autumn) in UB and from 0.93 (station 4-winter) to 3.85 in spring and summer (station 5 and 2, respectively) in GB. Dominance values were inversed to those of diversity in both bays. Concerning spatial diversity variation, in UB the lowest values were mainly located close to coast in autumn-winter and the highest values in spring-summer. In GB, a defined spatial pattern of diversity was not observed. Differences on both seasonal and spatial patterns of diversity seem to be related to different conditions of circulation, winds, depths, the presence and distribution of Macrocystis forests, density and diversity of benthos, environmental variables (chlorophyll a, salinity and temperature) and the anthropogenic influence. The results of this study allow us to determine, through the use of diversity as an ecological indicator, the existence of different mesozooplanktonic taxa associations with a certain degree of endemism or indicator value, in zones with human disturbance and eutrophication symptoms and others more related with waters free of pollution.