Organic matter that is washed onto shore, or “wrack”, is an important component of shoreline ecosystems and often represents accumulations of material produced in adjoining terrestrial and aquatic habitats.  It provides habitat for invertebrates, which attract birds and other predators, and provides a source of soil organic matter and nutrients to the upland terrestrial communities.  However, wrack along freshwater shorelines has not been studied extensively, and shoreline modification continues without taking into account this essential ecosystem element.  We investigated the decomposition rates and invertebrate communities of wrack on four different types of Hudson River shorelines: two natural (sandy and rocky) shorelines and two human made (riprap and cribbing) shorelines.   

Results/Conclusions

We found a significantly faster decay rate and a lower density of invertebrates on cribbing shoreline, while decay and invertebrate density on riprap were similar to that of the rocky shoreline.  The sandy shoreline had the highest invertebrate population numbers.  Invertebrate diversity was higher on sandy, rocky, and riprap shorelines than on cribbing shorelines. As managers seek to restore and protect shorelines from future sea level rise, this study suggests that cribbing may not be the best restoration strategy for increasing the ecological value of the shoreline.