Floating-leaved plants thrive in low salinity bays

Nymphaeid plants have their own requirements for where they can grow: the water must be almost fresh and there must be no waves. Therefore, these plants are commonly found in inland waters, but also in sheltered bays of coastal river mouths and estuaries.

Since the stems of nymphaeid plants’ leaves must reach the surface of the water, they only thrive in fairly shallow water, less than four meters deep. In areas deeper than this, floating-leaf plants are replaced by submerged-leaf (elodeid) aquatic plants. In very shallow water, aerial plants (helophyte) such as common reed (Phragmites australis), cattails or bulrush (Typha spp.) and bulrush or tule (Schoenoplectus spp.) take over.

Familiar and spectacular aquatic plants

The most common floating plants are the yellow water-lily, brandy-bottle, or spadderdock (Nuphar lutea) and the white waterlily, European white water lily or white nenuphar (Nymphaea alba). They are perennial plants that overwinter as rhizomes and grow a new shoot that reaches the water’s surface every summer.

Other plants characteristic of the floating plant community are the bur-reeds, especially the European bur-reedor unbranched bur-reed, floating bur-reed or narrowleaf bur-ree and least bur-reed or small bur-reed (Sparganium emersum, S. angustifolium and S. natans). The habitat characterized by floating plants commonly grow, among others, watermilfoils (Myriophyllum spp.) and pondweeds (Stuckenia pectinata, Potamogeton spp.) and often also arrowhead, duck potato, swamp potato, tule potato, or wapato. (Sagittaria spp.).

Habitat of least concern

Bottoms characterized by nymphaeids occur along the entire coast of Finland. However, the habitat is most common in the estuaries of the Bay of Bothnia and the eastern Gulf of Finland, due to the low salinity of these waters.

Floating leaf plants react to eutrophication in different ways, but for the most part they tolerate increased nutrients well. As eutrophication continues, it is possible that the species composition within the habitat will change: the species will begin to shift towards species that are more tolerant of turbid and nutrient-rich waters. In general, water turbidity is not as critical for floating leaf plants as it is for submerged leaf plants, where all their photosynthetic leaves are located below the water surface.

The habitats characterized by floating leaf plants are assessed as habitats of least concern, i.e. the habitat is not endangered and, according to current knowledge, is not at risk of becoming endangered. Severe eutrophication and coastal dredging may cause local losses.

Species in habitats characterized by floating leaved plants

Yellow water-lily (Nuphar lutea)

European white water-lily (Nymphaea alba)

Arrowhead (Sagittaria spp.)

European bur-reed (Sparganium emersum)

Floating bur-reed (Sparganium an­gustifolium)

Small bur-reed (Sparganium natans)

Watermilfoils (Myriophyllum spp.)

Pondweeds (Stuckenia pectinata, Potamogeton spp.)