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Baltic Associated Investigators: Related Time Series: Zooplankton samples were collected within the Baltic Sea HELCOM Combine Monitoring Programme. The Maritime Branch of the Institute of Meteorology and Water Management is responsible for collecting the samples along the southern coast of the Baltic Sea (in the Polish EEZ), however, over those thirty years, zooplankton was analyzed by several experts working in various institutions. The dataset started in 1979. In 1986 the location of the Southern Gotland Basin station was slightly changed. Data from years 1998 and 2000-2001 are still missing. Frequency of sampling varied in time (3-6 time per year) but the spring and summer conditions can be described for each year. Samples were taken following the guidelines of the Manual for Marine Monitoring in the COMBINE Programme of HELCOM (especially Annex C-7: Mesozooplankton) which means that the vertical hauls of the WP-2 net with 100 µm mesh size were used. Stratified samples (all presented here) were collected in the layers from the bottom to the halocline (included); from the top of halocline to the thermocline (included); and from the top of thermocline to the surface. Preservation (4% formaldehyde solution) as well as sub-sampling and lab analyses were carried out according to the HELCOM guidelines. Total abundance and biomass is presented for the last nine years only (2002-2010) as the earlier data are being still verified. A strong year-to-year variation in the abundance of Temora and Acartia is observed. Their relative abundance in copepods is increasing due to the significant decrease of Pseudocalanus. Acknowledgements Presented data were collected within the Polish National Monitoring Programme and permission to demonstrate them was granted by the Chief Inspector of Environmental Protection ( https://www.gios.gov.pl/) |