A THREATENED SPECIES OF NORTHEASTERN TIGER BEETLE, CINCINDELA DORSALIS DORSALIS AS AN INDICATOR OF BEACH HEALTH

The Northeastern Beach Tiger Beetle, Cicindela dorsalis dorsalis, is listed as federally threatened under the Endangered Species Act. Current population data of C. d. dorsalis show that many populations are in decline on sandy beaches along the U.S. east coast and that anthropogenic shoreline modifications are destroying the remaining habitat. By law, beetle abundance at a site can prohibit coastal development or the use of an erosion control device. Our research tested the hypotheses that the presence or absence of C. d. dorsalis is an indicator of beach health and that shoreline modifications lead to declines in beetle populations.

One of the largest populations of C. d. dorsalis occurs on beaches along Smith Point, Virginia in the Chesapeake Bay. This region contains about thirty percent of the C. d. dorsalis population. Consequently, the survival of the species depends, in part, on its protection at this site. Since 1937, the north end of the study area has eroded more than 100 m, most likely due to updrift bluff armoring. In June, 2001 the U.S. Army Corps of Engineers placed approximately 11,900 m³ of inlet dredge material on the highly eroded north end of Smith Point beach which allowed us to examine the impact of the nourishment project on beetle populations. Empirical data of beach width, beach slope, shoreline changes, grain size, beach saturation, pore water salinity, and beach compaction show that the beetles prefer relatively saturated, less saline, finer-grained, and wide beaches. Additionally, the beach fill helped to increase the beetle population at the impact site, as well as to attract an additional marsh beetle species, C. marginata, due to the silty nature of the beach fill. These results are expected to provide guidance on establishing and maintaining "healthy" beaches to coastal managers and planners.