The Interannual Changes in the Secondary Production and Mortality Rate of Main Copepod Species in the Gulf of Gdańsk (The Southern Baltic Sea)

Abstract

The main objective of this paper was description of seasonal and interannual trends in secondary production and mortality rates of the three most important Copepoda taxa in the Gulf of Gdańsk (southern Baltic Sea). Samples were collected monthly from six stations located in the western part of the Gulf of Gdańsk during three research periods: 1998–2000, 2006–2007, and 2010–2012. Production was calculated based on copepod biomass and mortality rates estimated according to vertical life table approach. Redundancy analysis was used to investigate relationship between secondary production and environmental conditions. During the entire research period there was significant interannual and seasonal variability of secondary production, mortality rate, as well as abundance and biomass anomalies. Conducted analysis revealed positive correlation between increasing temperature and production of Acartia spp. and Temora longicornis developmental stages, while older copepodites of Pseudocalanus acuspes showed almost negative correlation with temperature. The mortality rate estimations obtained for Acartia spp. were the highest in summer, while Temora longicornis peaked in spring–summer period. The lowest mortality rate estimations were noted in autumn and winter for almost all stages of investigated taxa.