Mesozooplankton diversity as ecological indicator of the anthropogenic influence: a study case in two subantarctic bays

BIANCALANA, F.; HOFFMEYER, M.S.; BERASATEGUI, A.A.; DUTTO, M.S.; KOPPRIO, G.

Figueira da Foz, Portugal

Simposio; ECSA 47 Symposium; 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 assemblages 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 salinity, temperature and chlorophyll a measures were obtained from 22 and 7 sampling stations 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. In autumn-winter, Ctenocalanus citer, Oithona similis and Halicarcinus planatus dominance values were between 25-45%, in both bays. In spring-summer, the taxa with higher dominance values (19-39%) were Podon leuckarti, Acartia tonsa and Bryozoa. Eurytemora americana presented up to 10 % of dominance and was 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 inversely related to those of diversity in both bays. Concerning the spatial diversity variation in UB, the lowest and the highest values were mainly located close to the coast in autumn-winter and in spring-summer, respectively. A non defined spatial pattern of diversity was observed in GB. Differences on both seasonal and spatial patterns of diversity are related to different conditions of circulation, winds, depths, 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.