Caroline C. Arantes | USGS Science

USGS2025

Assessing policy effectiveness trends in nonindigenous aquatic species introduction in the Ohio River basin

Aquatic invasive species (AIS) create costly, detrimental effects when established. Recognition of this in the United States reached a threshold in 1990 with the federal passage of the Nonindigenous Aquatic Nuisance Prevention and Control Act. This act created six regional panels, the national Aquatic Nuisance Species Task Force, and incentivized state-level AIS planning. The management of the Ohio River basin fell under the Mississippi River Basin Panel and the state-led Mississippi Interstate Cooperative Resource Association, which developed a joint action plan in 2010 to prevent, contain, and manage AIS. All Ohio River basin states besides West Virginia created aquatic nuisance species plans between 1999 and 2021. This study aims to utilize the best available data, the USGS Nonindigenous Aquatic Species (NAS) database, to examine how legislative and planning milestones have influenced the rate of new AIS arrivals and the spread of existing and new AIS. Arrival and spread of AIS were assessed at the HUC-8 scale (8-digit hydrological unit code) along the Ohio, Wabash, Cumberland, Alleghany, Monongahela, and Tennessee rivers. A near-linear increase in new AIS across all rivers was determined. Most AIS species (35–55%) did not spread beyond the HUC they were first detected in, while less than 10% spread to all HUCs in a river. The findings indicate no clear correlation between legislative and planning milestones and changes in AIS spread. More work could help to fill data gaps in detecting and monitoring AIS through coordinated local and regional programs, as expanding the quality and quantity of data collection efforts can improve understanding of AIS dynamics, assessments of management effectiveness, and inform future policy. Future work could expand the analysis to evaluate the effectiveness of policy and planning programs in reducing AIS, considering the variability in on-the-ground approaches and spread prevention efforts across states.

Alabama, Georgia, Illinois, Indiana, Kentucky, Mis↗

USGS2023

Can spatial food web subsidies associated with river hydrology and lateral connectivity be detected using stable isotopes?

During and following lateral connections, aquatic organisms residing in the river channel may assimilate material from sources imported from oxbows, and oxbow residents may consume and assimilate material imported from the channel. Hydrology, lateral connectivity, and stable isotope ratios of fishes and mussels were analyzed for evidence of spatial food web subsidies between the active channel and oxbow lakes in the floodplain of the Guadalupe River, Texas. During surveys conducted between March 2016 and April 2017, fish, mussel, periphyton, seston, and riparian plant samples were collected in and around two oxbows and adjacent channel sites for analysis of stable isotope ratios. Biplots of δ 13 C and δ 15 N were graphed for basal sources and specimens of six common fish species, four sunfish species ( Lepomis spp. combined), and two mussel species (Unionidae combined) captured from oxbows and the channel. Within each graph, polygons were drawn to indicate the space occupied by animals that could have assimilated feasible combinations of source materials originating from either oxbows or the river channel. Based on positions of animals within source polygons, riparian C4 grasses were not an important source of organic matter supporting biomass of fishes and mussels within the channel or oxbows. Overall, 84% of organisms had isotopic signatures consistent with assimilation of in situ sources, but also 76% of all organisms were inconclusive with regards to cross-habitat exchanges. Outliers that may have assimilated ex situ source material were observed for only 4% of 313 organisms from oxbows and 9% of 232 organisms from the channel, and some but not all of these cases followed high flow pulses that connected oxbows for extended periods. Several issues that compromise inferences from stable isotope analysis were identified, and estimation of spatial food web subsidies in fluvial systems could be enhanced by analyzing additional biomarkers, such as isotopic ratios of other elements and compound-specific stable isotopes, as well as additional sources, time-specific biotracers, and experimental approaches that directly track movement of sources and organisms in spatially structured food webs.

Texas↗