Anna Lemieszek

Modeling of egg production by Temora longicornis from the Southern Baltic Sea including salinity

The paper presents modeling of egg production (Egg — no. of eggs female−1 d−1) by Temora longicornis in the changing environmental conditions of the southern Baltic Sea (Gdańsk Deep). It is hypothesized that the food-saturated rate of egg matter production is equivalent to the specific growth rate of copepods. Based on the findings from the south-western Baltic Sea, Egg of T. longicornis is evaluated as a function of food concentration, temperature and salinity over a wide range of these parameters. Subsequently, the rate of reproduction during the seasons in the Gulf of Gdańsk is determined. According to our calculations, values of Egg reach ca 11 eggs per day in April and decline strongly in June-July, while the second smaller peak in reproduction occurs in September, ca 8 eggs per day. Our results suggest that egg production rates of T. longicornis depend not only on food concentration and temperature, but also on salinity, which is a masking factor in the Baltic Sea.

Seasonal changes in the abundance and biomass of copepods in the south-eastern Baltic Sea in 2010 and 2011

Background Copepods are major secondary producers in the World Ocean. They represent an important link between phytoplankton, microzooplankton and higher trophic levels such as fish. They are an important source of food for many fish species but also a significant producer of detritus. In the terms of the role they play in the marine food web, it is important to know how environmental variability affects the population of copepods. Methods The study of the zooplankton community in the south-eastern Baltic Sea conducted during a 24-month survey (from January 2010 to November 2011) resulted in the identification of 24 invertebrate species (10 copepods, seven cladocerans, four rotifers, one ctenophore, one larvacean, and one amphipod). Data were collected at two stations located in the open sea waters of the Gulf of Gdansk: the Gdansk Deep (P1) (54°50′N, 19°19′E) and in the western, inner part of the Gulf of Gdansk (P2) (54°32′N, 18°48.2′E). The vertical hauls were carried out with the use of two kinds of plankton nets with a mesh size of 100 µm: a Copenhagen net (in 2010), and a WP-2 net (in 2011). Results The paper describes the seasonal changes in the abundance and biomass of copepods, taking into account the main Baltic calanoid copepod taxa (Acartia spp., Temora longicornis and Pseudocalanus sp.). They have usually represented the main component of zooplankton. The average number of copepods at the P1 Station during the study period of 2010 was 3,913 ind m−3(SD 2,572) and their number ranged from 1,184 ind m−3 (in winter) to 6,293 ind m−3(in spring). One year later, the average count of copepods was higher, at 11,723 ind m−3(SD 6,980), and it ranged from 2,351 ind m−3(in winter) to 18,307 ind m−3(in summer). Their average count at P2 Station in 2010 was 29,141 ind m−3, ranging from 3,330 ind m−3(in March) to 67,789 ind m−3(in May). The average count of copepods in 2011 was much lower at 17,883 ind m−3, and it ranged from 1,360 ind m−3 (in April) to 39,559 ind m−3 (in May). Discussion The environmental conditions of the pelagic habitat change in terms of both depth and distance from the shore. Although the qualitative (taxonomic) structure of zooplankton is almost identical to that of the coastal waters, the quantitative structure (abundance and biomass) changes quite significantly. The maximum values of zooplankton abundance and biomass were observed in the summer season, both in the Gdansk Deep and in the inner part of the Gulf of Gdansk. Copepods dominated in the composition of zooplankton for almost the entire time of the research duration. Quantitative composition of copepods at the P1 Station differed from the one at P2 Station due to the high abundance of Pseudocalanus sp. which prefers colder, more saline waters.

Long-term changes in the total development time of Copepoda species occurring in large numbers in the Southern Baltic Sea – numerical calculations

Abstract The study presents changes in the total development time of Copepoda species, i.e. Pseudocalanus sp., Temora longicornis and Acartia spp. occurring in large numbers in the Southern Baltic Sea. The following factors were taken into account: temperature, salinity and concentration of food. The presented research involved simulations with greenhouse gas emissions scenarios A1B and B1. The analysis was performed for naupliar and copepodid stages combined together, and the results present the total development time of organisms from the naupliar stage to the adult form. The calculations were carried out using numerical methods based on the experimental data available in the literature.

Population dynamics of the main copepod species in the Gulf of Gdansk (the Southern Baltic Sea): abundance, biomass and production rates

Abstract The aim of this study was to describe the production biomass and abundance dynamics of the major Baltic calanoid copepods (Acartia spp., Temora longicornis and Pseudocalanus sp.) in the Gulf of Gdansk (the southern Baltic Sea) during a three-year period from March 2010 to December 2012. The data were collected at six stations located in the western part of the gulf. Acartia spp. was the most abundant taxon throughout the study period. The observed differences in the weighted mean depth for the investigated species were >2 m between nauplii and adults of Acartia spp., >5 m between nauplii and adults of Temora longicornis and 3 m between nauplii and younger copepodites of Pseudocalanus sp. The highest values of the secondary production rates were determined for Acartia spp. - almost 17.55 mg C m-2 d-1 (summer 2011), while Temora longicornis reached 3.80 mg C m-2 d-1 in spring 2010 and Pseudocalanus sp. had the highest secondary production values in summer 2011 - about 1.28 mg C m-2 d-1.