Biological attributes refer to the number and types of organisms that inhabit a waterway.
The poorer the quality of water, the fewer the number and types of organisms that can live in it. Justicia americana in Wheeling Creek. Photo courtesy of Dr. Ben Stout. When assessing water quality, it is also important to look at the quality of organisms that live in a waterway. Some species are more sensitive to chemical and physical changes in their habitat than other species.