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2.3 Status of quality elements
Ecological status is determined for rivers, lakes, transitional and coastal water bodie based on biological quality elements and supporting physico-chemical and hydromorphological quality elements.
Textbox: Biological quality elements and supporting quality elements
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Phytoplankton are free floating microscopic algae, which are very sensitive to the level of nutrients in a given water body. Phytoplankton may cause the water to become green, brown or red, depending on the dominant species. Phytoplankton consist of many different groups of algae, e.g. green algae, diatoms, dinoflagellates, as well as the potentially toxic cyanobacteria that may create blooms in nutrient enriched lakes, and cause problems for use of the water for drinking water supply and recreation. |
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Aquatic benthic flora comprises phytobenthos and macrophytes in rivers and lakes, and macroalgae and angiosperms in coastal and transitional waters. Aquatic flora is particularly susceptible to elevated nutrient concentrations in the water. Phytobenthos are small algae that grow on rocks and other substrates, including bacterial tufts and coats if the water body is enriched with organic matter from waste water. Aquatic plants (macrophytes and angiosperms) grow mainly on soft substrate in shallow waters in rivers, lakes and transitional and coastal waters, while large algae (macroalgae) grow on rocky substrate along the shores of coastal and transitional waters. |
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Benthic invertebrates are small animals that inhabit the bottom, as well as nearshore areas of streams, rivers, lakes, coastal and transitional waters. They include e.g. aquatic insects, crustaceans, snails and mussels. Benthic invertebrates are a key source of food for fish. Benthic invertebrates are susceptible to many different pressures, such as organic enrichment causing oxygen deficiencies, alterations of habitats, acidification, fine-sediments, and inputs from agricultural pesticides. |
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Fish are particularly susceptible to hydromorphological pressures, revealing impacts of river bank constructions, large flow fluctuations, water abstraction, inadequate shelters beneath roots and poorly structured water beds. Such habitat alterations affect the fish abundance, their species composition or age structure. In addition, salmon and many other fish species that migrate from the sea to river headwaters to spawn are dependent on river continuity. Hence, changes in fish composition and abundance often reveal lost river continuity (e.g. due to barriers or dams). Fish are also very sensitive to acidification. |
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Hydromorphological elements support the biological elements. They generally consist of 1) the hydrological regime (e.g. quantity and dynamics of water flow and connection to groundwater bodies) and 2) the morphological conditions (e.g. depth and width variation, structure and substrate of the bed, and structure of the riparian zone). In rivers, it also includes river continuity (i.e. presence of barriers and dams or other transversal structures). |
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Physico-chemical quality elements support the biological quality elements. They generally consist of 1) light and thermal conditions, 2) oxygenation conditions, 3) salinity, 4) nutrient conditions, and 5) river basin specific pollutants (RBSPs). For rivers and lakes, they also include acidification status. |
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Previous comments
With regard to the physico-chemical quality elements, it would be helpful to add a sentence explaining that the boundary values for these quality elements are set by MS and that these can vary substantially from one MS to another MS.
First line: bodie--> bodies
it is suggested to be added what it is in italics
...... Fish are particularly susceptible to hydromorphological pressures, revealing impacts of interruptions of longitudinal continuity, river bank constructions, large flow fluctuations, water abstraction, inadequate shelters beneath roots and poorly structured water beds.
Textbox: Biological quality elements and supporting quality elements
It should be made clearer which the biological quality elements and which supporting elements are.
"Fish are particularly susceptible to hydromorphological pressures, revealing impacts of river bank constructions."
The main hydromorphological alteration in big rivers is the loss of rapids due to raised water levels by damming, for example salmon and trout require rapids habitat for spawning.
Hydromorpholigcal elements
As dams are also a kind of barriers, it is proposed to delete "dams".