Woodchip bioreactors (WBs) are a promising technology capable of decreasing nitrate concentration in subsurface (tile) drainage system (SDS) effluent. Although they are effective in removing nitrate, little is known regarding the potential impact on microbes and antimicrobial resistance (AMR) in subsurface drainage waters. Therefore, the main objective of this study was to measure how bioreactors influence microbial concentrations and AMR concentrations in tile drainage water with different flow conditions and microbial communities. A column study was conducted to simulate an existing, field denitrifying woodchip bioreactor. Four synthetic waters were spiked with different combinations of microbes isolated from the influent of a field-scale bioreactor and pumped through the columns during the experiment. Steady and wet-dry flow conditions were examined. The results of this work demonstrated the potential for denitrifying bioreactors to reduce E. coli concentrations within SDSs under different flow conditions, which expands the potential benefits of WBs. However, the results also illustrated that WBs have the potential to increase phenotypic antibiotic-resistant microbes in the subsurface drainage waters. Applying different microbial communities had significant effects on culturable microbial concentrations, as columns receiving more microbes with a greater diversity had a greater increase in culturable microbial concentrations. A statistically significant and consistent increase in phenotypic AMR concentrations was also found within woodchip bioreactors after assessing the sensitivity of recovered isolates to five different antibiotics. Additional laboratory and future in-field studies are warranted to improve the prediction of pathogen removal and AMR changes in tile drainage water, as well as to support the development of an effective design for microbial contaminant removal from waters passing through denitrifying bioreactors.
•Biological and edaphic filters influenced community assembly post reclamation.•Young and old well pads had different plant trait composition from reference.•Old well pads had high introduced species and low trait functional diversity (FDQ).•Old well pads may be considered in an arrested successional state.•Short, native, xeric species with large seeds should be sown on future sites.
•CaO particle size is the most important treatment efficiency parameter.•Removal of sea urchins lead to recovery of kelp forests and associated fauna.•Gonad content in remaining sea urchins increase to commercial levels within 1–2 y.•Habitat structure must be considered when planning a management strategy.
In this study, we compared the early fish colonization of three types of artificial reefs deployed in the coastal waters of Saba and a Eustatius in the Caribbean: reef balls (R), layered cakes and piles of locally obtained basaltic rock. As an indicator of performance, three fish assemblage parameters (abundance, biomass, species richness) were measured using underwater visual censuses at 11 months post-deployment and 4 months after restoration from hurricane damage. All artificial reef plots showed higher values for fish abundance, biomass and species richness than control plots covered by bare sand, which shows that artificial reefs can locally enhance the fish assemblage. However, the effect differed among artificial reef plots. Fish abundance was 3.8 times higher on the layered cake plots compared to the reef ball plots, while fish biomass was 4.6 times higher. Rock pile plots had intermediate values. Species richness did not differ significantly among different artificial reef plots. Three-dimensional modelling revealed that layered cakes had a smaller gross volume, shelter volume and total surface area than reef balls. The availability of multiple small shelters in the layered cake design appeared to be more relevant than other physical parameters, as the layered cake plots had higher fish abundance than the reef balls plots. We concluded that on Saba and St. Eustatius, layered cake plots performed better than reef ball plots after one year of colonization. Rock pile plots, made of local volcanic rock, showed an intermediate performance, and were 4-10 times cheaper to construct. If observed differences are consistent with other locations and persist during further colonization, current efforts to deploy reef balls could better be allocated to deploy artificial reef structures with a higher shelter density.
Hazards in coastal ecosystems, such as flooding and land loss, demand natural and nature-based solutions from local communities due to the protective and non-protective services they provide when compared with traditionally engineered approaches. In this context, natural solutions are those that consider conserving existing habitats whereas nature-based solutions are those created by humans. These solutions support important coastal ecosystem functions, such as nutrient uptake, fisheries habitat, soil carbon storage, and surge attenuation. Our main research questions were: (1) Based on community engagement, what are the possible natural and nature-based solutions to address coastal hazards in Breton Sound Estuary, Louisiana? and (2) How do these community co-designed nature-based solutions support various ecosystem functions? To help answer these questions, we leveraged the competency group methodology to incorporate the local needs and traditional ecological knowledge of community stakeholders into collaborative ecosystem modelling. In total, fifteen members regularly met five times over an eight-month period to design nature-based solutions to address coastal hazards. Two nature-based solutions, created marshes and restored ridges, were identified most frequently by the competency group (>75% occurrence) in a final survey. Associated ecosystem functions of the identified solutions were assessed with simulation models to determine future ecosystem functions of nutrient uptake, fisheries habitat, soil carbon storage, and surge attenuation after 20 years. By adding created marshes to an ecosystem, our model results indicate slight increases in nutrient uptake, likely increases to fisheries habitat and soil carbon storage capacity, as well as storm surge attenuation in some areas following ridge restoration. Quantifying these ecosystem functions with management actions has been limited and is needed to assess how natural and nature-based solutions impact local communities and resource users. This novel approach to modeling ecosystem-based solutions through a collaborative modeling process with researchers and residents can be applied elsewhere to assess the viability of natural and nature-based solutions.
