The USGS Nonindigenous Aquatic Species Database (NAS; nas.er.usgs.gov) is a comprehensive tool for demonstrating where and when nonindigenous species have been sighted across the U.S. Information in the database is used for state-level invasive species management plans, to focus monitoring efforts, for public education, predictive modeling, and for avoiding unintentional introductions during inter-basin water transfers.
Our project represents the first attempt to utilize the NAS Database within the context of a Landscape Conservation Cooperative conservation blueprint. A significant amount of effort during the past year was dedicated to determining the most appropriate use of these data for the purposes of identifying the mechanisms and patterns of aquatic species invasions. Descriptive analyses were first undertaken to characterize the spatial and temporal characteristics of the South Atlantic LCC subset of NAS data.
There are approximately 13,000 records in the USGS NAS Database. Since the 1850s, 282 aquatic species have been introduced into over 6,000 unique locations in the South Atlantic LCC where they are considered non-native, almost half of which are from outside North America (Figure 1). The list of species includes freshwater and marine species, aquatic vertebrates and invertebrates, as well as aquatic plants. Nearly 150 of the 282 species are fish species. Two-thirds of these species are transplants from their historic native ranges in other parts of North America.
On a decadal time-scale, the rate of increase in the total number of nonindigenous species observed in the South Atlantic LCC followed an exponential function between the period from 1850-1980 (Figure 2). A linear trend in the number of new nonindigenous species sightings in the South Atlantic LCC (50 new species recorded per decade) has occurred from 1980-2010. If this trend continues, sightings of 46 new aquatic species in the South Atlantic LCC will be reported during the period from 2010 – 2020.
It is intuitive that where people live or congregate, there are introductions of non-indigenous species. Figure 3 shows the number of species recorded in each of the hydrologic units (HU) overlaying its percentage of urbanization. We performed the Kruskal-Wallis statistical test to further examine differences in the numbers of records, the number of species, and the numbers of records per species for USGS 8-digit hydrologic units (National Watershed Boundary Dataset; http://nhd.usgs.gov/wbd.html) classified as urban, non-urban, coastal, and inland. We performed the same tests on HUs classified according to the presence/absence of reservoirs located anywhere within the HU or on its boundary. These analyses show significant increase in the number of species reported in urban HUs relative to those classified as rural, and in HUs with reservoir contact relative to those without reservoir contact. The total numbers of records were also found to differ significantly in urban versus rural HUs and in HUs with reservoir contact compared to those without reservoir contact. The results of these tests match with our team’s experience with NAS data from other regions, though this is the first time quantitative comparisons have been applied across multiple locations. The implications of these findings are still being explored.