20–0.25 day−1 for CI, CII, and CIV. After autumn 2006 the mortality rate has fallen to about 0.05 for CI, CII and CIII, and low values persisted for winter 2007. For IV copepodite stage mortality gradually increased until the summer of 2007 and reached a maximum of 0.33 day−1. During the summer–autumn 2007 for CII there was an inverse relation than in 2006. Daily mortality rate has

increased over the period of 2007, while in 2006 it was declining ( Fig. 4). For CV there was a significant increase in mortality rates between the winter and spring to 0.46 day−1 in 2006 and it falls in summer to 0.18 day−1. In subsequent periods, the trend also indicates a greater increase in mortality in the spring and summer, and autumn and winter daily mortality rates decline. T. longicornis CI ( Fig. 4) showed highest mortality values in winter 2006 (0.24 day−1),

which decreases in the autumn of the same year, CP-868596 order and in the spring of 2007 (0.19 day−1) and then decreases until the fall of 2007. Similarly, for CIII during both years mortality rate rose in the spring, and then decreased in the autumn. Between autumn 2006 and spring 2007 mortality rates for CI, CIII and CIV could not be calculated. For CV during the winter and spring of 2006 mortality of 0.05–0.10 day−1 was observed, and reached maximum value in autumn (0.34 day−1). In 2007 maximum mortality rate was recorded in Fulvestrant the spring (0.35 day−1). Due to relatively scarce data for Pseudocalanus sp. in many cases mortality rates could not be calculated. For example mortality rates of CI stage are marked only in the spring for both 2006 and 2007, with a similar value of about 0.20 day−1. Similarly CII shows the mortality rate at 0.10 day−1 during the spring, summer 2006 and summer 2007. Highest mortality rates for CIV were observed in the summer of 2006 (>0.80 day−1), and then decreased in autumn to 0.33 day−1. In 2007 mortality rate increased till summer (>0.70 day−1) and then again decreased in autumn to a value of approximately 0.40 day−1. Mortality rates of investigated species were significantly Diflunisal different between series of seasons in 2006 and 2007 (Mann–Whitney U test, p > 0.05); furthermore the correlation coefficient

for Acartia spp. morality rates and water temperature was r = 0.7 (p < 0.05), r = 0.8 (p < 0.05) for T. longicornis and r = 0.8 (p < 0.05) for Pseudocalanus sp.; however, due to calculations being made on seasonal data and overall low number of calculated mortality data results may be prone to errors. Copepod biomass estimates may be biased by the low numbers of sampled stations, relatively long intervals between series and advective transport (Aksnes and Blindheim, 1996) as well as the difference in the sampling gear used by other authors. It is also clear that a 2-year study period was too short to demonstrate long-term trends. However, analyses of the long-term biomass dynamics in Central Baltic deep basins (Dippner et al., 2000, Kornilovs et al.