Aquatic plants in the Suså
Aquatic plants are important for the quality of a stream. They create a dynamic stream and serve as hiding places for fish and other streamfauna (invertebrates). It is an environmental goal to have as large a diversity in aquatic plants as possible.
In the late 19th century the Suså was a good stream for aquatic plants. That has since changed. In 1896 there were registered 17 different pondweed species. Nowadays there is only six left.
The main reason for the reduction in number of species is the increased amount of nutrients in the waterways. The most sensitive species are quickly displaced if the nutrient levels become too high. It is a phenomenon seen all over the country. Another, but less significant, reason for the decline in number of species, is intensive weed cutting and other waterway maintenance in the 20th century.
When aquatic plants disappear, the stream becomes dominated by sand and tall amphibious plants that grow from the banks and into the stream. It is plants like bur-reed that begins to take over and fill up the entire waterway.
Even if the nutrient levels in the stream is reduced it is difficult to get extinct species to establish themselves in the stream again. Seeds need to be available, and if they are not already present in the ground, they must be transported by birds and other animals moving between locations. Seeds can attach themselves to feathers, pelts and legs, or if they have been eaten through droppings.
To improve the diversity in aquatic plants in the Suså, two things can be done. One is to create and improve habitats suitable for these sensitive species. And two, is to assist the natural process by manually reintroducing them to the stream.
Pondweed species in the Suså
• Fennel Pondweed (Potamogeton pectinatus)
• Curled Pondweed (Potamogeton crispus)
• Broad-leaved Pondweed (Potamogeton natans)
• Shining Pondweed (Potamogeton lucens)
• Perfoliate Pondweed (Potamogeton perfoliatus)
• Long-stalked Pondweed (Potamogeton praelongus)
• Small Pondweed (Potamogeton pusillus)
• Blunt-leaved Pondweed (Potamogeton obtusifolius)
• Lesser Pondweed (Potamogeton panormitanus)
• Fen Pondweed (Potamogeton coloratus)
• Various-leaved Pondweed (Potamogeton gramineus)
• Red Pondweed (Potamogeton alpinus)
• Sharp-leaved Pondweed (Potamogeton acutifolius)
• Grass-wrack Pondweed (Potamogeton compressus)
• Flat-stalked Pondweed (Potamogeton friesii)
• Hairlike Pondweed (Potamogeton trichoides)
• Slender Pondweed (Potamogeton filiformis)