Macroflora in the watercourses of Saaremaa Island (Estonia)

The study focused on 40 reaches of 29 short narrow shallow watercourses on Saaremaa Island. The floristic list covers 68 taxa of vascular plants, including 14 species of true or obligate water plants, 18 taxa of amphibious plants, and 36 taxa of terrestrial plants. The article presents differences in the frequency of vascular plants between the watercourses of Saaremaa and mainland Estonia. Three taxa of macroalgae were new to Estonia. Ranunculus aquatilis, Berula erecta, and Alisma plantago-aquatica preferred a higher content of nitrogen compounds. However, Lemna minor, Veronica anagallis-aquatica, and Agrostis stolonifera var. prorepens preferred a higher content of phosphorous compounds. Cladophora rivularis preferred both higher nitrogen and phosphorous compounds in water. Potamogeton natans and Equisetum fluviatile preferred softer sediments, and Ulothrix zonata preferred relatively low pH values.