Pinnularia is a fresh water alga more specifically a type of Bacillariophyta (diatom).
Pinnularia is a predominantly fresh-water alga, usually found in ponds and moist soil. They can also be found in springs, estuaries, sediments, and oceans. Members of this genus are most commonly found in 40cm (1¼ ft) of water, at 5°C (40 °F).
(From: Wikipedia, July 2015)