The contribution of man-made ditches to the regional stream biodiversity of the new river watershed in the Florida panhandle

摘要

The role of ditches as reservoirs for or contributors to regional diversity has rarely been assessed. In this study, we aimed (1) to assess the effect of ditches on aquatic faunal assemblages of first order streams and (2) to assess the extent to which the animal communities in altered streams that are crossed by ditches resembled those found in nearby natural streams. We examined the fauna of four different aquatic habitats of the New River watershed in the Florida Panhandle: (1) natural streams, (2) altered streams, (3) ditches that cross the altered streams, and (4) ditches that do not cross the altered streams, sampling these habitats in three geographically distinct sites and visiting each location three times during a summer. Ditches did not have the same environmental features as streams and as a result their faunal community did not completely mimic those of natural streams. Streams contained 50% less aquatic vegetation and more canopy cover, while natural streams were more acidic than any other habitat. The connected altered stream and ditch habitats contained the highest biodiversity, while natural streams contained the lowest. Our ordination of taxonomic composition did not reveal any significant differences between habitats. However, natural streams were more likely to contain Hyalella spp., Oligochaetes, and Palaemonetes spp. than other sites, yet did not contain Baetidae spp., Naucorida spp., Trepobate spp., Dolomedes okefinokensis, Leptolucania ommata, or any Centrarcids. These results indicate the importance of ditches within this system as a reservoir for and contributor to regional stream biodiversity and this finding should be taken into consideration by managers for the conservation of the regional freshwater biodiversity.