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

Lidia Dzierzbicka-Głowacka,Paula Prątnicka,Anna Lemieszek,Maja Musialik-Koszarowska,Maria Iwona Żmijewska,Maciej Janecki,Marcin Kalarus

doi:10.3390/app9102039

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.

Highlights

The Baltic Sea is a unique ecosystem, and due to its inland character, large drainage area, and limited exchange of sea water with the Atlantic it is very sensitive to ongoing natural and anthropogenic changes
Higher water temperature leads to shorter generation time and smaller body size of copepods, causing individuals to reach reproductive age quicker, and causing rapid increases in density [31]
When estimating the rate of secondary production of these copepods, we used a Di function that takes into account the individual temperature optimums

Summary

Introduction

The Baltic Sea is a unique ecosystem, and due to its inland character, large drainage area, and limited exchange of sea water with the Atlantic it is very sensitive to ongoing natural and anthropogenic (climate change, pollution, eutrophication, and overfishing) changes. The coastal zone is especially vulnerable, and in similarity to other regions of the Baltic Sea, exhibits little variety in the number of animal species, which is the result of eutrophication and the degradation of the environment. It is considered among the marine habitats with the highest biological productivity. It plays an important ecological role by offering a variety of habitat types for many species, giving shelter to animals, and functioning as nursery areas and feeding grounds for many marine fishes and crustaceans.

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