MAIN LABORATORY
The Department for Biological Assessments is part of the Main Laboratory for Water and has, for many years, been engaged in the evaluation of the ecological status / potential of surface waters based on biological quality elements. Since the implementation of the Water Framework Directive (WFD), the key legislative framework for water management across EU countries, ecological status classification has been primarily determined by biological elements, complemented by hydromorphological, physicochemical, and chemical quality indicators. This approach places living organisms at the forefront, as they integrate multiple stressors to which they are exposed in their aquatic environment, revealing long-term changes in water and habitat quality. For this reason, biological quality elements provide substantial benefits compared to conventional methods, where water quality assessments were predominantly based on physical and chemical indicators that capture only momentary pollution.
Surface water quality is classified into five categories: very good, good, moderate, poor, and bad. Very good status is defined as a biological, chemical, and hydromorphological state that is either unaffected or only minimally affected by human activities. The highest achievable status is the “reference condition,” while the prevailing conditions in such waters are known as “reference conditions.” These conditions are specific to each water type, as environmental factors and the composition of biological communities vary across regions and even locally between different water types. The assessment of water quality is based on the degree of deviation from these conditions. A “good” status signifies a “slight” deviation, while a “moderate” status indicates a “moderate” deviation, and so forth. It can therefore be said that the conditions in aquatic systems are the result of a combination of natural and anthropogenic factors.
To measure the effects of a particular stressor and to understand changes in species composition within communities, it is essential to determine the sensitivity of individual species to specific stressors. The cumulative impact of these stressors leads to changes in community structure, from a decline in the proportion of sensitive taxa to their complete disappearance, ultimately allowing for the colonisation of more tolerant species Consequently, the newly formed community may be significantly altered compared to the reference community, both taxonomically and functionally. It can be stated that, as stressors increase, communities tend to become poorer in species richness and are increasingly dominated by species that are more tolerant of deteriorating conditions and toxicity.
To ensure a reliable assessment of the ecological status of surface waters, the WFD recommends using various groups of aquatic organisms, known as biological quality elements—macrozoobenthos (benthic macroinvertebrates), phytobenthos, phytoplankton, fish, and macrophytes. The Department currently analyses three water quality elements: macrozoobenthos, phytobenthos, and phytoplankton. This process involves sample collection, sample processing, species identification, and the calculation of ecological status based on the identified organisms. The list of identified organisms from a specific monitoring station and their relative abundance serve as the foundation for all metric calculations of ecological quality.
The macrozoobenthos biological quality element comprises animals that are generally visible to the naked eye, living on substrates at the bottom of surface waters (e.g. crustaceans, snails, mussels, insects, etc.). Thanks to the well-established ecological requirements, or better yet, their responses to various environmental variables and stressors, macrozoobenthos is considered one of the best indicators of habitat and water quality in watercourses, particularly concerning organic pollution and hydromorphological alterations. Macrozoobenthos plays a crucial role in the nutrient cycling of freshwater ecosystems and represents an essential segment of the food web, as nearly all macroinvertebrates serve as a potential food source for larger organisms, such as fish and birds.
The phytobenthos biological quality element consists of algae that grow in biofilms on the surface of substrates in surface waters. It is used in assessing the ecological status of water quality due to its simple sampling process and because it is one of the first biological quality elements to respond to changes in water quality. To assign an ecological status rating based on this indicator, diatoms (siliceous algae) from the phytobenthos are analysed, as they inhabit all types of biotopes and provide a predictable response to nutrient enrichment (eutrophication), making them reliable indicators of ecological quality.
The phytoplankton biological quality element represents a highly diverse group of photosynthetic cyanobacteria and eukaryotic algae adapted to life in the open water column. It is used as an indicator of water status in lakes and very big rivers, where the development of a phytoplankton community is possible. As increased concentrations of nutrients in the water promote excessive growth of phytoplankton as a primary producer, phytoplankton serves as a good indicator of eutrophication in aquatic ecosystems.
The Department for Biological Testing currently employs eight biologists, with plans to expand its workforce. All employees are required to undergo trainings both within the Department and through external education programmes, to ensure the reliable assessment of water quality. The accuracy of organism identification is verified through international intercalibrations, where the department consistently achieves excellent results. Additionally, interlaboratory comparison tests are conducted with neighbouring countries, allowing for the exchange of analytical results from shared monitoring stations on transboundary watercourses. Beyond these activities, the department’s experts actively participate in conferences and seminars and engage in scientific research, publishing their findings in independent peer-reviewed national and international journals.