Mesozooplankton diversity as ecological indicator of the anthropogenic influence: A study case in two subantartic bays

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

Figueira da Foz, Portugal

Congreso; ECSA 47; 2010

MESOZOOPLANKTON DIVERSITY AS ECOLOGICAL INDICATOR OFTHE ANTHROPOGENIC INFLUENCE:A STUDY CASE IN TWOSUBANTARCTIC BAYSBiancalana, F. (1,*), Hoffmeyer, M.S. (1), Berasategui, A.A. (1), Dutto, M.S. (1) and Kopprio, G.(2)IADO-CONICETZMT*Corresponding author biancaf@criba.edu.arThis study focused on the use of specific diversityas ecological indicator of the variation of mesozooplankton assemblagesrelated 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 22and 7 sampling stations inUB 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 planatusdominance 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 dominanceand wasparticularly 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 relatedto those of diversity in both bays. Concerningthe spatial diversity variationin UB, the lowest and the highest values were mainly located close tothe coast in autumn-winter and in spring-summer, respectively. A nondefined spatial pattern of diversitywas observedin GB.Differences on both seasonal and spatialpatterns of diversityarerelated to different conditions of circulation, winds, depths, presenceand distribution of Macrocystis forests, density and diversity of benthos, environmental variables (chlorophyll a, salinity and temperature) and the anthropogenic influence. The results ofthis 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 zoneswith human disturbance and eutrophicationsymptoms and others more relatedwith waters free of pollution.