Land-use proxies for aquatic species introductions in the Laurentian Great Lakes

Abstract

Many nonindigenous aquatic species (NAS) adversely impact ecosystems, human health, and the economy of the Laurentian Great Lakes region. Targeted prevention and eradication efforts in response to early detection of NAS can be both cost advantageous and effective at preventing further spread or establishment. To help inform the process of priority site selection for early detection monitoring, I developed and evaluated land-use metrics of three prominent anthropogenic introduction pathways (commercial maritime traffic, recreational maritime traffic, and live release from urban areas). Logistic and linear regression analyses were conducted between species presence or species richness and introduction pathway intensity for 23 NAS over a five-decade period (1970 - 2013) to explain the apparent spatio-temporal patterns of historic aquatic invasions. The probability of NAS sightings increased with increasing city size, commercial maritime trips, and marina size for all NAS, decade, and pathway combinations. Of the land-use metrics evaluated, city population size was the best model factor and potential proxy of both NAS presence and richness, even for NAS introduced through ballast water discharge. The importance of commercial maritime traffic to NAS presence and richness may have been underrepresented due to rapid secondary spread of planktonic NAS away from port locations prior to detection. Nonetheless, city population size, total commercial maritime trips, and marina size may be reasonable proxies for propagule pressure given the significant relationships between these specific pathway metrics and NAS sightings and richness, and as such, are applicable to the development of early detection monitoring programs in the Laurentian Great Lakes.