As exposure to coastal hazards increases there is growing interest in nature-based solutions for risk reduction. This study uses high-resolution flood and loss models to quantify the impacts of coastal wetlands in the northeastern USA on (i) regional flood damages by Hurricane Sandy and (ii) local annual flood losses in Barnegat Bay in Ocean County, New Jersey. Using an extensive database of property exposure, the regional study shows that wetlands avoided $625 Million in direct flood damages during Hurricane Sandy. The local study combines these models with a database of synthetic storms in Ocean County and estimates a 16% average reduction in annual flood losses by salt marshes with higher reductions at lower elevations. Together, the studies quantify the risk reduction ecosystem services of marsh wetlands. Measuring these benefits in collaboration with the risk modelling industry is crucial for assessing risk accurately and, where appropriate, aligning conservation and risk reduction goals.
Coastal salt marshes are highly sensitive wetland ecosystems that can sustain long-term impacts from anthropogenic events such as oil spills. In this study, we examined the microbial communities of a Gulf of Mexico coastal salt marsh during and after the influx of petroleum hydrocarbons following the Deepwater Horizon oil spill. Total hydrocarbon concentrations in salt marsh sediments were highest in June and July 2010 and decreased in September 2010. Coupled PhyloChip and GeoChip microarray analyses demonstrated that the microbial community structure and function of the extant salt marsh hydrocarbon-degrading microbial populations changed significantly during the study. The relative richness and abundance of phyla containing previously described hydrocarbon-degrading bacteria (Proteobacteria, Bacteroidetes, and Actinobacteria) increased in hydrocarbon-contaminated sediments and then decreased once hydrocarbons were below detection. Firmicutes, however, continued to increase in relative richness and abundance after hydrocarbon concentrations were below detection. Functional genes involved in hydrocarbon degradation were enriched in hydrocarbon-contaminated sediments then declined significantly (p<0.05) once hydrocarbon concentrations decreased. A greater decrease in hydrocarbon concentrations among marsh grass sediments compared to inlet sediments (lacking marsh grass) suggests that the marsh rhizosphere microbial communities could also be contributing to hydrocarbon degradation. The results of this study provide a comprehensive view of microbial community structural and functional dynamics within perturbed salt marsh ecosystems.
The emulsification of oil at the Deepwater Horizon (DWH) well head relegated a large proportion of resultant hydrocarbon plumes to the deep sea, facilitated the incorporation of oil droplets into microbial and planktonic food web, and limited the severity of direct, wetland oiling to coastal Louisiana. Nevertheless, many transient fish and invertebrate species rely on offshore surface waters for egg and larval transport before settling in coastal habitats, thereby potentially impacting the recruitment of transient species to coastal nursery habitats quite distant from the well site. We compared the utilization of salt-marsh habitats by transient and resident nekton before and after the DWH accident using data obtained from an oyster reef restoration project in coastal Alabama. Our sampling activities began in the summer preceding the DWH spill and continued almost two years following the accident. Overall, we did not find significant differences in the recruitment of marsh-associated resident and transient nekton in coastal Alabama following the DWH accident. Our results, therefore, provide little evidence for severe acute or persistent oil-induced impacts on organisms that complete their life cycle within the estuary and those that spent portions of their life history in potentially contaminated offshore surface waters prior to their recruitment to nearshore habitats. Our negative findings are consistent with other assessments of nekton in coastal vegetated habitats and bolster the notion that, despite the presence of localized hydrocarbon enrichments in coastal habitats outside of Louisiana the most severe oil impacts were relegated to coastal Louisiana and the deep sea. Analyzing all the information learned from this accident will undoubtedly provide a synthesis of what has or has not been affected in the Northern Gulf of Mexico, which when put in context with oil spill studies elsewhere should improve our ability to avert and manage the negative consequences of such accidents.
Ecosystem boundary retreat due to human-induced pressure is a generally observed phenomenon. However, studies that document thresholds beyond which internal resistance mechanisms are overwhelmed are uncommon. Following the Deepwater Horizon (DWH) oil spill, field studies from a few sites suggested that oiling of salt marshes could lead to a biogeomorphic feedback where plant death resulted in increased marsh erosion. We tested for spatial generality of and thresholds in this effect across 103 salt marsh sites spanning ~430 kilometers of shoreline in coastal Louisiana, Alabama, and Mississippi, using data collected as part of the natural resource damage assessment (NRDA). Our analyses revealed a threshold for oil impacts on marsh edge erosion, with higher erosion rates occurring for ~1-2 years after the spill at sites with the highest amounts of plant stem oiling (90-100%). These results provide compelling evidence showing large-scale ecosystem loss following the Deepwater Horizon oil spill. More broadly, these findings provide rare empirical evidence identifying a geomorphologic threshold in the resistance of an ecosystem to increasing intensity of human-induced disturbance.
Freshwater peatlands are carbon accumulating ecosystems where primary production exceeds organic matter decomposition rates in the soil, and therefore perform an important sink function in global carbon cycling. Typical peatland plant and microbial communities are adapted to the waterlogged, often acidic and low nutrient conditions that characterise them. Peatlands in coastal locations receive inputs of oceanic base cations that shift conditions from the environmental optimum of these communities altering the carbon balance. Blanket bogs are one such type of peatlands occurring in hyperoceanic regions. Using a blanket bog to coastal marsh transect in Northwest Scotland we assess the impacts of salt intrusion on carbon accumulation rates. A threshold concentration of salt input, caused by inundation, exists corresponding to rapid acidophilic to halophilic plant community change and a carbon accumulation decline. For the first time, we map areas of blanket bog vulnerable to sea-level rise, estimating that this equates to ~7.4% of the total extent and a 0.22 Tg yr(-1) carbon sink. Globally, tropical peatlands face the proportionally greatest risk with ~61,000 km(2) (~16.6% of total) lying ≤5 m elevation. In total an estimated 20.2 ± 2.5 GtC is stored in peatlands ≤5 m above sea level, which are potentially vulnerable to inundation.
Assessment of long-term phosphorus retention in an integrated constructed wetland treating domestic wastewater
- Environmental science and pollution research international
- Published almost 6 years ago
Due to the nature of the phosphorus (P) removal mechanisms associated with constructed wetlands, the sustainability of P treatment is usually of high interest. As a result, a 4-year dataset from a typical multi-celled integrated constructed wetland (ICW) located at Glaslough in Co. Monaghan, Ireland was evaluated to determine the effects of long-term P loadings and hydrological inputs on P treatment. The ICW was intensively monitored year-round from February 2008 through March 2012 for total P and molybdate reactive phosphate (MRP). Domestic wastewater was loaded at 16.4 ± 0.96 g m(2) year(-1) for total P and 11.2 ± 0.74 g m(2) year(-1) for MRP. Average mass reductions over the monitoring period were 91.4 and 90.1 %, respectively. The area-based kinetic coefficients (K (20)) of 11.8 for total P and 15.6 m year(-1) for MRP indicated a high area-specific retention rate. The ICW appeared to have a sustained capacity for P adsorption and retention, but the treatment was influenced mainly by external hydrological inputs and fluctuations in wastewater loadings. Linear regression analyses showed a reduction in mass retention of both total P and MRP with increased effluent flow volumes. Monthly mass reductions exceeded 90 % when the effluent flow volumes were less than 200 m(3) day(-1). When monthly effluent flow volumes exceeded 200 m(3) day(-1), nonetheless, mass reductions became highly variable. Designs and management of ICW systems should adopt measures to limit external hydrological loadings in order to maintain sufficient P treatment.
The accumulation and distribution of lead and chromium was tested in a laboratory-scale constructed wetland (CW) inoculated with metal-tolerant bacteria. Two non-inoculated systems also were evaluated, one planted and the other unplanted. Mass balances indicated that 57% of chromium input was accumulated into inoculated CW after 151 days of operation. The distribution was similar in support media and vegetation, in which 78% was transferred to aerial part. Similarly Pb was accumulated 29% in the support media and 39% in vegetation, which was distributed 52% in rhizome and 48% in aerial part. Significantly lower amounts of heavy metals were accumulated in non-inoculated systems than in the inoculated wetlands (p<0.005). In addition, a markedly higher proportion of chromium in aerial vegetation and of lead in the suspended fraction of the effluent was exhibited, which raises a subsequent recovery of the metal by harvest and settling, respectively. Results indicate that CW inoculated with metal-tolerant bacteria might be a suitable option for treating wastewater with content of lead and chromium.
To improve the performance efficiency of subsurface constructed wetlands (CWs), a variety of media have been tested. Recently, there has been a rising interest in biochar. This research aims to develop the effectiveness of sand media amended with biochar and two plants species (Melaleuca quinquenervia and Cymbopogon citratus) in removing phosphorus from sewage effluent in CWs. The experimental design consisted of vertical flow (VF) mesocosms with seven media treatments based on the proportions of biochar in the sand media which ranged from 0 to 25% by volume. During the first 8months, the mesocosms were loaded with secondary clarified wastewater (SCW) then septage was used for the remaining 8months. Inflow and outflow were monitored for total phosphorus (TP) and PO4-P. Plants were harvested at the end of the experiment and TP biomass was determined. Removal efficiencies of TP in the mesocosms loaded with SCW and septage ranged from 42 to 91% and 30 to 83%, respectively. Removal efficiencies of PO4-P ranged from 43 to -92% and 35 to 85% for SCW and septage, respectively. The results revealed that the sand media performed better than the biochar-amended media; increasing the proportion of biochar in the media decreased removal efficiency of phosphorus. However, after flushing due to major rain event, there was no significant difference between sand and sand augmented with 20% biochar. Total plant P ranged from 1.75g in the 20% biochar mesocosm to 2.10g in the sand only mesocosm. Plant uptake of P, at least in part, may be accredited for the better P removal efficiency in the sand media compared to the biochar-amended media.
Microcystis population and microcystin (MC) dynamics were investigated in western Lake Erie coastal wetlands and downstream beach water. A three-dimensional (3-D) model was developed to quantify how Microcystis population size and structure affect MCs.
Microorganisms play important roles in the reduction of organic and inorganic pollutants in constructed wetlands used for the treatment of polluted surface water. However, the diversity and structure of microbial community in surface water constructed wetland system remain poorly known. The present study was made to characterize bacterial and archaeal communities in a surface water constructed wetland using Illumina high-throughput sequencing. The diversity and structure of both bacterial and archaeal communities illustrated a remarkable spatiotemporal variation. Archaeal communities showed lower richness and diversity than bacterial communities. Bacterial diversity decreased with increasing wetland layer depth. A variety of bacterial phyla or candidate divisions were found in wetland bacterial communities, including Proteobacteria, Chloroflexi, Firmicutes, Acidobacteria, Bacteroidetes, Nitrospirae, Actinobacteria, Spirochaetae, Planctomycetes, Chlorobi, Deferribacteres, Cyanobacteria, OP8, WS3, TA06, and OP11, while Proteobacteria, Chloroflexi, and Firmicutes were the major bacterial groups. Euryarchaeota and Thaumarchaeota dominated wetland archaeal communities.