Efficient and effective aquatic macroinvertebrate monitoring for rocky coasts

Rocky coasts have received less biotic monitoring than other areas, partially due to the difficulty of sampling and working in such areas. For example, divers are often used to collect benthic macroinvertebrates, resulting in high sampling costs.  We developed a more cost-effective method for monitoring macroinvertebrates in these areas, and used the data to recommend potential indicator metrics for further testing. The method, developed along Lake Superior’s rocky north shore, involves placing artificial substrates on the lake bottom for the month of August.  We deployed substrates at 8 sites (3 undisturbed and 5 disturbed) in 2005 and 2006. Data from these sites were used for methods and indicator development. We deployed substrates at an additional 5 randomly-chosen sites in 2007 to better test the indicator metrics.  Artificial substrate samples contained significantly different types of invertebrates than those found on natural substrates (either rocks sampled by divers or sand sampled by ponar dredge).  However, the use of artificial substrates helped to minimize the differences among sites due to substrate type variations. This should allow managers to better focus on differences caused by human activities rather than differences due to substrate type.