The monitoring of concentrations of contaminants is divided in two subsections: trend monitoring and periodic survey. For trend monitoring observations are made at fixed stations, the coordinates of which have been determined in advance. Objective of the survey is to identify changes in concentrations of heavy metals, as well as priority and other harmful substances and compounds, including radionuclides in water, sediments and/or tissues of biological organisms for substances with observed concentrations above or significantly above the prescribed background level. Sampling is performed once in a year. Sampling time for radionuclides in August, for other contaminants in June August. In the frame of periodic survey monitoring of sediment and biota contamination with harmful substances is carried out once in 6 years within the reference period of the monitoring programme, with an aim to obtain an overview of the levels of priority and other harmful (hazardous) compounds and substances and their spatial distribution. Sampling time in June to August. Sampling method and/or kind of samples: sediments Kajak Sediment Core sampler, layers 1.5 cm; mussels Macoma balthica (Van Veen grab) and Mytilus edulis (divers) fish tissues from Perca fluviatilis (coastal waters), Clupea harengus (open water)

Observations are made at fixed stations, the coordinates of which have been determined in advance. Observations are made in the same points as for the monitoring of soft-bottom zoobenthos. For the sampling HELCOM standard Van Ween grab is used. For neurotoxic and oxidative stress markers (accordingly acetylcholinesterase (AChE) inhibition, activity of glutathione S transferase (GST) and catalase (CAT)) as well as for the heavy metals presence indicator (concentration of metallothionein (MT)) in bivalve molluscs Limecola balthica (called also Macoma balthica) 3 times in a year in May, August and November. For the analysis substrate is filtered through the net with mesh size 9 mm and c.a. 50 individuals with size > 14 mm are collected in each station. GST, CAT, MT is determined in digestive gland, but AChE in foot tissue of Limecola balthica. Testing methods: Neurotoxic stress biomarker acetylcholinesterase inhibition (AchE) is measured using the Elman method (Elman et al., 1961) modified and adapted to the microplate reader (Bocquene and Galgani, 1998). The glutational-S-transferase activity of the oxidative stress biomarker (GST) is measured according to the Habig method (1974) modified for the microplate reader, while the catalase activity (CAT) according to the methods developed by Claiborne (1985) and Aebi (1974). The concentration of metalothionein (MT) is determined by the Viarengo (1997) method. For the reproductive function/malformations of benthic amphipods Monoporeia affinis sampling is performed once in a year in winter (January-February) using HELCOM standard Van Ween grab. At least 50 alive fertilized females from each station are used for the analysis of quality of embryo development, where the number of embryos, the stage of development and their state of development are identified: the development of embryos, deformation, magnified embryos or embryos without visible visual disturbance, undeveloped, unfertilised or dead eggs, or the whole bag of eggs. This method ensures that the effects of pollution are identified and it is recommended that embryos be used for such analysis at their later stages of development (e.g. development stages 3-7 where deformation of embryos can be seen better).

Observations are carried out using available satellite images.