Abstract
Rigorous evaluation of ballast water management systems (BMWSs) at land-based test facilities requires that water used in testing meets minimum concentrations of dissolved and particulate material, for example, using the criteria in the U.S Environmental Technology Verification (ETV) Program's protocol for testing of BWMSs. Here, uptake water (challenge water) can be augmented with compounds to meet these benchmarks. In this study, we evaluated materials used to supplement dissolved organic matter (DOM), particulate organic matter (POM), and mineral matter (MM) used to achieve challenge water criteria. To determine the additives' contributions to DOM and POM pools, the mass yields of Camellia sinesis (decaffeinated iced tea) extract and humic matter were calculated at different temperature and salinities. Additionally, the response of ambient organisms to these additives was measured in mesocosm experiments, in which changes in organism concentrations were measured after a 5-d holding time. Living organisms were grouped into three size classes: ≥50 µm (nominally zooplankton), ≥10 to <50 µm (nominally protists), and <10 µm (measured as culturable, aerobic, heterotrophic bacteria). Significant differences in concentrations between control and treatment mesocosms after 5 d were not detected for organisms in the ≥10 to <50 µm or the ≥50 µm size classes. However, bacterial concentrations increased significantly in mesocosms augmented with exogenous materials. Thus, direct impacts (or indirect impacts through increased bacterial concentrations) were not apparent among organisms in the two largest size classes. Finally, a literature review of DOM, POM, and total suspended solids concentrations in coastal waters was conducted. It revealed that the challenge water concentrations outlined in the ETV protocol are at the middle to upper range of concentrations observed in coastal and estuarine water. The mean DOM and POM concentrations in this data set typically fell short of the ETV minimum requirements, and more data are needed to fully assess the suitability of these requirements.
Highlights
An important introduction pathway for aquatic alien species is the growing trade of wildlife for ornamental purposes (Padilla and Williams 2004; Strecker et al 2011; Masin et al 2014)
The presence of the North American Marmorkrebs (Procambarus fallax f. virginalis) in European inland waters is entirely driven by ongoing propagule pressure from the ornamental trade
In line with related research, the probability of Marmorkrebs release was largely affected by gross domestic product and human population density, i.e. predictors very likely related to the density of Marmorkrebs owners, whereas environmental suitability was mostly influenced by minimum temperature and the availability of lentic habitats, which was indirectly assessed by terrain slope
Summary
An important introduction pathway for aquatic alien species is the growing trade of wildlife for ornamental purposes (Padilla and Williams 2004; Strecker et al 2011; Masin et al 2014). This study links a maximum-entropy model that forecasts the probability of Marmorkrebs introduction based on socio-economic predictors to an updated species distribution model based on environmental predictors in order to explore the risk of further Marmorkrebs establishment in Europe.
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