## 3 Results
### Mortality Rate  
Mortality rates of the investigated species were diverse thorough the research period. The result obtained for _Acartia_ spp. showed the highest mortality rates mainly in summer, although in the initial years of research a different trend was observed. In 1998, the highest mortality rate was recorded in autumn (0.4 day\({}^{-1}\)); while in 2000 and 2006 the peak mortality rate was recorded in spring. The highest rate of mortality of _Acartia_ spp. was obtained in summer 2010, with a value of 0.8 day\({}^{-1}\). Winter was characterized by lowest mortality, remaining during all years of research at a similar level: about 0.2 day\({}^{-1}\). Increased mortality rates of _T. longicornis_ were usually noted for two seasons: summer-autumn 1999, spring-summer 2007, and spring-summer 2010-2012. These values fluctuated between 0.5 day\({}^{-1}\) to 0.7 day\({}^{-1}\). However, the highest mortality rate of _T. longicornis_ was observed in spring 2006, reaching over 0.8 day\({}^{-1}\). In winter mortality remained low, not exceeding 0.2 day\({}^{-1}\). The mortality rates of _P. acuspes_ showed a very irregular distribution throughout the study period. In 1999 and 2007, two peaks were recorded, in winter and in summer. During 2006 and 2010 increased mortality of this species was observed during the summer season. Mortality rates in 2011 and 2012 remained at a similar level in all seasons (Figure 13). \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Predictors** & **T** & & & \\ \hline Distribution & normal & & & \\ Link function & identity & & & \\ GLM fitted for 12 response variables: & & & & \\ \hline
**Developmental stages** & **Type** & **R2[\%]** & **F** & \(p\) \\ \hline _Acartia_ spp\_CI & quadratic & 18.4 & 18.4 & \textless{}0.00001 \\ _Acartia_ spp\_CII & quadratic & 1.0 & 17.4 & \textless{}0.00001 \\ _Acartia_ spp\_CIII & quadratic & 20.5 & 21.0 & \textless{}0.00001 \\ _Acartia_ spp\_CIV & quadratic & 24.6 & 26.6 & \textless{}0.00001 \\ _Acartia_ spp\_CV & quadratic & 20.9 & 21.5 & \textless{}0.00001 \\ _Temon longicornis\_N_ & quadratic & 19.5 & 19.8 & \textless{}0.00001 \\ _Temon longicornis\_CI & quadratic & 12.2 & 11.3 & \textless{}0.00002 \\ _Temon longicornis\_CII & quadratic & 15.0 & 14.3 & \textless{}0.00001 \\ _Temora longicornis\_CIII & quadratic & 14.0 & 13.3 & \textless{}0.00001 \\ _Temora longicornis\_CIV & linear & 5.5 & 9.6 & 0.00229 \\ _Temora longicornis\_CV & linear & 4.3 & 7.4 & 0.00732 \\ _Pseudocalanus acuspes\_CV & quadratic & 8.3 & 7.4 & 0.00086 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Response of copepods developmental stages production to temperature (generalized linear model (GLM)). Figure 13: Mean daily mortality rates (\(\pm\) standard deviation) for (**a**) _Acartia_ spp., (**b**) _Temora longicornis_, and (**c**) _Pseudocalanus acuspes_ in the Gulf of Gdänsk during seasons of investigation. In context of mortality of individual development stages for _Acartia_ spp. (N-CV) the highest mortality was noted in the spring-summer period, and it concerned mainly the fifth copepotConsidering mortality rates, GLM plots showed a positive, linear relationship between _T. longicornis_ stages (from N to CIV), _Acartia_ spp. (CI, CII, and CIV), and temperature. Both _Acartia_ spp. CV and _T. longicornis_ CV demonstrated unimodal response along the temperature gradient, while _P. acuspes_ CV showed a negative relationship with temperature factor (Table 5, Figure 17). Figure 16: Means plot illustrating mortality distribution of _Acartia_ spp., _Temora longicornis_, and _Pseudocalanus acuspes_ developmental stages in relation to seasons. Figure 15: nMDS plot illustrating the samples ordination according to mortality rates based on the seasons factor. Horizontal mortality distribution of _Acartia_ spp. showed the highest mortality rate at the shallow station 6 in spring and at stations 6, 1, and 2 (\(>\) 0.68) in summer. In autumn, the mortality rate of _Acartia_ spp. was within the same range at all stations (0.34-0.68).