Tuesday, May 27, 2008
238

Bryophytes and macroinvertebrates, disturbance and recovery in streams: An experiment

Brian C.L. Shelley, Biology, The College of New Jersey, 2000 Pennington Road, Ewing, NJ 08628

Bryophytes can be important in streams and influence the distribution of benthic macroinvertebrates. This influence may be important when considering how macroinvertebrates respond to, and recover from disturbance, including flow disturbances which rearrange benthic substrates and reduce bryophyte cover. This experiment was designed to study how bryophytes influence macroinvertebrates and their recovery from an artificial disturbance in three low-order streams. Initially, rocks were sampled to estimate the standing crop of epilithon and bryophytes, and the density of macroinvertebrates. Next, rocks were scrubbed with a brush to simulate a disturbance, marked and placed in each stream. The position of each rock was monitored to quantify the impacts of subsequent disturbances. After 12 and 24 months, rocks were sampled to assess recovery. Recovery was incomplete for both bryophytes and macroinvertebrates, even after 2 years, while epilithon increased relative to initial levels. Some macroinvertebrate taxa were especially slow to recover, never approaching pre-manipulation densities, while other taxa became more prevalent. For example, the caddisfly <i>Brachycentrus</i> sp., which was common on moss-covered rocks before the manipulation in Moccasin Brook (mean 1233 ind. m<sup>-2</sup>, all but disappeared. Water pennies (<i>Psephenus</i> sp.) on the other hand often became more common. Clearly, bryophytes influence macroinvertebrates and may provide refugia during minor events. But recovery from disturbance is slow when bryophyte cover has been reduced due to disturbance. It may take years for the bryophytes to fully recover, and this slow recovery will likely have a significant influence on macroinvertebrates found in streams where bryophytes are common.


Web Page: bryophytes, macroinvertebrates, recovery