hornwort and common frogbit float at surface in shallow freshwater river, dirty water filled with detritis, organic particles

air aquatic background balance biotope bubble ceratophyllum challenge clear climate coldwater contrast current demersum disaster ecology ecosystem environment environmental europe european floating flora flow fragile frog gravel green ground human impact lake leaf litter moderate nature plant podillia ray root sbit season snail stem still stream substrate sun sunshine temperate ukraine underwater vegetation vulnerable water wet wild wonder