Trade Exports Predict Regional Ballast Water Discharge by Ships in San Francisco Bay

Biological invasions often result from transfers of organisms during trade activities. In coastal ecosystems, commercial ships are a dominant source species globally, and ships’ ballast water (BW) is major focus biosecurity management policy to reduce invasions. While drives shipping patterns, diverse vessel types behaviors exist such that the quantitative relationship between BW dynamics still poorly resolved, limiting both science management. Here, we evaluated new method predict discharge using data, by explicitly considering known practices according commodity type. Specifically, estimated tonnage overseas exports volume for San Francisco Bay (SFB), California, as model system demonstrate this approach. Using extensive datasets on shipborne discharge, (a) spatial temporal patterns across nearly 20 ports in estuary 2006 2014 (b) developed predictive estimate foreign export whole estuary. Although arrivals SFB remained constant 2014, associated exported commodities more than doubled tripled. Increased resulted increased frequency per capita bulk carriers Asia tankers western Central America Hawaii, reflecting shifts direction movement. The top 11 (59% total tonnage) were transported or tankers. multivariate linear model, annual these type strong predictors bay-wide (adjusted R 2 = 0.92), creating potential past future delivery SFB. Bulk provides valuable insights into flux, since most driven behavior tank ships. data unavailable many regions time periods, whereas widely available can provide reliable proxy geographic source, which critical evaluate invasion risk.