Abundance of adults and late copepodites (III-V) of Eurytemora americana in Bahía Ushuaia (Beagle Channel): influence of temperature and chlorophyll-a conditions along two annual cycles

BERASATEGUI A.A.; HOFFMEYER, M.S; PRESTA ML.; CAPITAÑO F

Bernardino Rivadavia Natural Sciences Museum- Buenos Aires

Conferencia; Marine and Freshwater invasive species (MFIS-Argentina); 2016

Aquatic ecosystem, Health & Management Society

Eurytemora americana is an herbivorous copepod native in some northern hemisphere?s estuaries. In Argentina, it has been reported as invader in the Bahía Blanca Estuary where develops a planktonic pulse during winter-early spring, partially excluding the native copepod Acartia tonsa. After this, it remains as diapause eggs in bottom sediments. In Bahía Ushuaia (Beagle Channel), previous studies suggest that E. americana could be present along the year being more abundant in coasts with anthropogenic impact. However, knowledge about its population dynamics is very scarce in this bay. We analyzed the abundance seasonal variation of E. americana adults and copepodites (III-V) related to the variability of temperature and chlorophyll-a conditions. Samples were collected monthly (March 2006-February 2008) with a 200-μm mesh plankton net at a coastal site. Abundance showed a marked seasonal pattern. Maxima values were registered in summer (574.19 ind.m-3-30,687.03 ind.m-3) and minima in winter (1.45 ind.m-3 and 2.92 ind.m-3). Mature males and females were found in most of the studied months. Percentage of ovigerous females and females carrying spermathophores were always higher than 65%, except for April and June 2006 when they were not found. Highest abundances were associated with maximum values of chlorophyll-a during early spring and late summer. A positive correlation was found between copepodites abundance and temperature. Presence of ovigerous females along the entire seasonal cycle suggests that population is able of reproducing in a broad range of environmental conditions (temperature: 4.8-12.6ºC, chlorophyll-a: 0.015-1.29μg.L-3). The co-occurrence of these females with copepodites could indicate that this population maintains by subitaneous eggs. Future studies exploring the presence of diapause eggs in bottom sediments and the use of a smaller pore mesh net to optimize the capture of first larval stages would complement this preliminary approach.