hornwort and common frogbit float at surface in shallow freshwater river, dirty water filled with detritis, algae on a sunny day

air algae aquatic background balance biotope bubble ceratophyllum challenge clear climate coldwater common concept contrast current day demersum detritis dirty disaster ecology ecosystem environment environmental europe european filled float floating flora flow fragile freshwater frog frogbit gravel green hornwort human impact lake leaf litter moderate nature organic particles plant podillya ray river root sbit season shallow stem still stream summer sun sunny sunshine surface temperate threat ukraine underwater vegetation vulnerable water wet wild wonder