Macrophytes in Streams and Rivers
by
Eugene P. Macri Jr.

Macrophytes are larger plants found in streams and rivers that you can see with you naked eye. There are many types including submersed, emergent, floating attracted and unattached.  Macrophytes like algae are important because of photosynthesis and the production oxygen in the stream.  Macrophytes also furnish substrates for macroinvertebrate and algal communities.

These plants also furnish habitat for fish and other stream dwellers.  Unfortunately, most aquatic science text books in my estimation have vastly underestimated just how important macrophytes are in a stream or river.  This is especially true in spring creeks where macrophytes control patterns, cycles, sedimentation, nutrient dynamics and habitat requirements whether these streams are English Chalk Streams or Pennsylvania Limestone Springs. Macrophytes absorb and release nutrients, toxins and chemicals from the stream. Studies have shown that various submerged macrophytes are different in how they cycle nutrients and in their decomposition patterns. In some streams aquatic macrophytes load large quantities of Nitrogen and Phosphorous and hold these nutrients til they are released rapidly in autumn.

In many spring creeks macrophytes may increase water levels during specific seasons of the year. Macrophytes are often the "ecological engineers" of a stream.

In America for some reasons most state fish and game agencies and DEPs have no idea how macrophytes function and how important they are. The best understanding of macrophytes appear to be the English Riverkeepers on the Chalkstreams.  They also have perhaps the best understanding of substrates (photo below shows English Riverkeepers working on a Stream).

In England the Riverkeepers maintain and modify the macrophytes for their stream types.  In America this is seldom done and to put it bluntly and we are way behind in understanding these plants and their influence on stream and river dynamics. Macrophytes come in many familiar forms like algae, moss, cressbeds, and many flowering plants.