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.

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

Background. Copepods are the 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 terms of their role in the marine food web, it is important to know how the environmental variability affects the population of Copepoda. Methods. The study of the zooplankton community in the south-eastern Baltic Sea conducted during a 24-month survey (January 2010 to November 2011) resulted in 24 invertebrate species identified (10copepods, 7cladocerans, 4rotifers, 1ctenophore, Fritillaria borealis and Hyperia galba). Data were collected at two stations located on the open-sea deep-water station – the Gdańsk Deep (54o50’φN, 19o19’λE) and in the western, inner part of the Gulf of Gdańsk (54o32’ φN, 18o48.2 ’λE). Vertical hauls were carried out using two nets: a Copenhagen net with an inlet diameter of 50 cm and a mesh diameter of 100 µm (in 2010) and WP-2 net from KC Denmark with an inlet diameter of 57 cm and a mesh diameter of 100 µm (in 2011). Results. The paper describes seasonal changes in the abundance and biomass of Copepoda, taking into account the main Baltic calanoid copepod taxa (Acartia spp., Temora longicornis and Pseudocalanus sp.). They usually represented the main component of zooplankton. The average number of Copepoda at station P1 during the study period of 2010 was 3913 ind.m-3 (SD 2572) and their number ranged from 1184 ind. m-3 (in winter) to 6293 ind.m-3 (in spring). One year later, the average count of copepods was higher, i.e. 11 723 ind. m-3 (SD 6980) and ranged from 2351 ind. m-3 (in winter) to 18 307 ind.m-3 (in summer). Their average count at station P2 in 2010 was 29 141 ind. m-3 ranging from 3330 ind.m-3 (in March) to 67 789 ind. m-3 (in May). The average count of copepods in 2011 was much lower – 17 883 ind./m3 and ranged from 1360 ind./m3 (in April) to 39 559 ind./m3 (in May). Discussion. The environment of pelagic animals changes with the distance from the shore and with the sea depth. Although the qualitative structure of zooplankton is almost identical with that of the coastal waters, the quantitative structure changes quite significantly. The maximum values of zooplankton abundance and biomass were observed in the summer season, both in the Gdańsk Deep and the inner part of the Gulf of Gdańsk. Copepoda dominated in the composition of zooplankton for almost the entire duration of the research.. Quantitative taxonomic composition of Copepoda at station P1 (the Gdańsk Deep) was different compared to station P2 (the western, inner part of the Gulf of Gdańsk) due to a high percentage of a crustacean preferring waters with lower temperature and higher salinity – Pseudocalanus sp.

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

Background. Copepods are the 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 terms of their role in the marine food web, it is important to know how the environmental variability affects the population of Copepoda. Methods. The study of the zooplankton community in the south-eastern Baltic Sea conducted during a 24-month survey (January 2010 to November 2011) resulted in 24 invertebrate species identified (10copepods, 7cladocerans, 4rotifers, 1ctenophore, Fritillaria borealis and Hyperia galba). Data were collected at two stations located on the open-sea deep-water station – the Gdańsk Deep (54o50’φN, 19o19’λE) and in the western, inner part of the Gulf of Gdańsk (54o32’ φN, 18o48.2 ’λE). Vertical hauls were carried out using two nets: a Copenhagen net with an inlet diameter of 50 cm and a mesh diameter of 100 µm (in 2010) and WP-2 net from KC Denmark with an inlet diameter of 57 cm and a mesh diameter of 100 µm (in 2011). Results. The paper describes seasonal changes in the abundance and biomass of Copepoda, taking into account the main Baltic calanoid copepod taxa (Acartia spp., Temora longicornis and Pseudocalanus sp.). They usually represented the main component of zooplankton. The average number of Copepoda at station P1 during the study period of 2010 was 3913 ind.m-3 (SD 2572) and their number ranged from 1184 ind. m-3 (in winter) to 6293 ind.m-3 (in spring). One year later, the average count of copepods was higher, i.e. 11 723 ind. m-3 (SD 6980) and ranged from 2351 ind. m-3 (in winter) to 18 307 ind.m-3 (in summer). Their average count at station P2 in 2010 was 29 141 ind. m-3 ranging from 3330 ind.m-3 (in March) to 67 789 ind. m-3 (in May). The average count of copepods in 2011 was much lower – 17 883 ind./m3 and ranged from 1360 ind./m3 (in April) to 39 559 ind./m3 (in May). Discussion. The environment of pelagic animals changes with the distance from the shore and with the sea depth. Although the qualitative structure of zooplankton is almost identical with that of the coastal waters, the quantitative structure changes quite significantly. The maximum values of zooplankton abundance and biomass were observed in the summer season, both in the Gdańsk Deep and the inner part of the Gulf of Gdańsk. Copepoda dominated in the composition of zooplankton for almost the entire duration of the research.. Quantitative taxonomic composition of Copepoda at station P1 (the Gdańsk Deep) was different compared to station P2 (the western, inner part of the Gulf of Gdańsk) due to a high percentage of a crustacean preferring waters with lower temperature and higher salinity – Pseudocalanus sp.

Seasonal changes in the abundance and biomass of copepod in the southwestern Baltic Sea in 2010 and 2011

Background. Copepods are the 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 terms of their role in the marine food web, it is important to know how the environmental variability affects the population of Copepoda. Methods. The study of the zooplankton community in the south-western Baltic Sea conducted during a 24-month survey (January 2010 to November 2011) resulted in 24 invertebrate species identified (10copepods, 7cladocerans, 4rotifers, 1ctenophore, Fritillaria borealis and Hyperia galba). Data were collected at two stations located on the open-sea deep-water station – the Gdańsk Deep (54o50’φN, 19o19’λE) and in the western, inner part of the Gulf of Gdańsk (54o32’ φN, 18o48.2 ’λE). Vertical hauls were carried out using two nets: a Copenhagen net with an inlet diameter of 50 cm and a mesh diameter of 100 µm (in 2010) and WP-2 net from KC Denmark with an inlet diameter of 57 cm and a mesh diameter of 100 µm (in 2011). Results. The paper describes seasonal changes in the abundance and biomass of Copepoda, taking into account the main Baltic calanoid copepod taxa (Acartia spp., Temora longicornis and Pseudocalanus sp.). They usually represented the main component of zooplankton. The average number of Copepoda at station P1 during the study period of 2010 was 3913 ind.m-3 (SD 2572) and their number ranged from 1184 ind. m-3 (in winter) to 6293 ind.m-3 (in spring). One year later, the average count of copepods was higher, i.e. 11 723 ind. m-3 (SD 6980) and ranged from 2351 ind. m-3 (in winter) to 18 307 ind.m-3 (in summer). Their average count at station P2 in 2010 was 29 141 ind. m-3 ranging from 3330 ind.m-3 (in March) to 67 789 ind. m-3 (in May). The average count of copepods in 2011 was much lower – 17 883 ind./m3 and ranged from 1360 ind./m3 (in April) to 39 559 ind./m3 (in May). Discussion. The environment of pelagic animals changes with the distance from the shore and with the sea depth. Although the qualitative structure of zooplankton is almost identical with that of the coastal waters, the quantitative structure changes quite significantly. The maximum values of zooplankton abundance and biomass were observed in the summer season, both in the Gdańsk Deep and the inner part of the Gulf of Gdańsk. Copepoda dominated in the composition of zooplankton for almost the entire duration of the research.. Quantitative taxonomic composition of Copepoda at station P1 (the Gdańsk Deep) was different compared to station P2 (the western, inner part of the Gulf of Gdańsk) due to a high percentage of a crustacean preferring waters with lower temperature and higher salinity – Pseudocalanus sp.

Survival and dispersal variability of pelagic eggs and yolk-sac larvae of central and eastern baltic flounder (Platichthys flesus): application of biophysical models

A hydrodynamic model coupled with a Lagrangian particle tracking technique was utilized to simulate spatially and temporally resolved long-term environmentally related (i) size of habitat suitable for reproduction, (ii) egg/yolk-sac larval survival, (iii) separation of causes of mortality, and (iv) connectivity between spawning areas of Baltic flounder with pelagic eggs. Information on reproduction habitat requirements and mortality sources were obtained from field or laboratory studies. In our modelling study we only quantified physical processes generating heterogeneity in spatial distribution of eggs and yolk-sac larvae, as e.g. predation is not accounted for. The spatial extent of eggs and larvae represented as modelled particles is primarily determined by oxygen and salinity conditions. The reproduction habitat most suitable was determined for the Gdansk Deep, followed by the Bornholm Basin. Relatively low habitat suitability was obtained for the Arkona Basin and the Gotland Basin. The model runs also showed yolk-sac larval survival to be to a large extent affected by sedimentation. Eggs initially released in the Arkona Basin and Bornholm Basin are strongly affected by sedimentation compared with those released in the Gdansk Deep and Gotland Basin. Highest relative survival of eggs occurred in the Gdansk Deep and in the Bornholm Basin. Relatively low survival rates in the Gotland Basin were attributable to oxygen-dependent mortality. Oxygen content had almost no impact on survival in the Arkona Basin. For all spawning areas mortality caused by lethally low temperatures was only evident after severe winters. Buoyancy of eggs and yolk-sac larvae in relation to topographic features appear as a barrier for the transport of eggs and yolk-sac larvae and potentially limits the connectivity of early life stages between the different spawning areas.