Mesotrophic to eutrophic waterbody with vascular plants

This habitat type includes lakes, pools and stretches of rivers and broad streams with very slow-flowing water, which are naturally mesotrophic to eutrophic. The water is usually clear or brown (humic) with low to moderate concentration of chlorophyll and sediments suspended in the water column. The water is normally buffered to highly buffered and rich in basic ions with a pH typically circumneutral to basic. The sediment is rich in nutrients and might be partially organic and muddy. The habitat supports dense beds of aquatic macrophytes more or less rich in species. Macrophytes can disappear when pollution causes nutrient levels to rise further and the system enters the hypertrophic state. Aquatic macrophyte growth forms include floating and submerged forms. Depending on the water depth, the successional stage and the trophic status these waters can be colonized by communities dominated by nymphaeid species (such as Nymphaea spp., Nuphar lutea, Nymphoides peltata), rooted hydrophytes (Potamogeton spp., Myriphyllum spp., Najas spp., Vallisneria spiralis), freely floating hydrophytes (Ceratophyllum spp., Utricularia spp., Hydrocharis morsus-ranae, Stratiotes aloides and Lemna spp.). Typical of pools and shallow waters are the communities dominated by aquatic species of the genus Ranunculus (syn. Batrachium) and Callitriche.

Most of the species populating this habitat type are critical to phosphorus concentrations in the water. Optimal conditions of this habitat are represented by a high nutrient content in the sediment (in the mesotrophic to eutrophic range) and a low nutrient content in the overlying water (with optimal values of phosphorus below 1 µmol/L over the growing season).

Beds of Nymphaea lotus var. thermalis in their natural distribution area are also part of this habitat. Nymphaea lotus is an East-African and Southeast-Asian species, however N. lotus var. thermalis is endemic to the thermal water of PeÅ£a River in Transylvania, Romenia.

Temporary flooded shores and emergent macrophytes stands are excluded from this habitat type and are instead included in other habitats C3.5a (Periodically exposed shores with stable, mainly eutrophic sediments with pioneer and ephemeral vegetation), C3.5b (Periodically exposed shores with stable, mainly mesotrophic sediments with pioneer and ephemeral vegetation) and C5.1a (Tall helophyte dominated freshwater vegetation), C5.1b (Small helophyte dominated freshwater vegetation).

Indicators of good quality:

• Dense beds of submerged and floating macrophytes
• Relatively high species diversity of submerged and floating macrophytes
• Absence or very low abundance of floating and submerged algae beds (FLAB)
• Low abundance of emergent species indicators of a process of succession or eutrophication (e.g. Phragmites australis, Typha spp., Sparganium spp., Glyceria maxima, Schoenoplectus spp., etc.)
• Concentrations of nutrients and chlorophyll naturally in the range of mesotrophy and eutrophy (approximately P 20-100 μg/L and chlorophyll 5-40 μg/L)
• Absence or very low abundance of exotic invasive species
• Absence or very low abundance of species indicators of hypertrophic conditions (e.g. Lemna gibba, L. minor, Spirodela polyrhiza, etc.)
• Not excessive turbidity of the water due to high chlorophyll concentrations and suspended detritus and sediments in the water column
• pH weakly acid, to circumneutral to alkalinic (usually pH 6-8)
• No excessive accumulation of organic mud and sediments. Occasionally a layer of detritus may occur in stands with Nymphaeid plants.

Note: Chemical and physical parameters are only indicative, they may change in different geographical area and climatic conditions.

Synthesis of Red List assessment

Confidence in the assessment

Pressures and threats