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1.
Mar Pollut Bull ; 166: 112231, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33798816

RESUMO

Long-term assessments are needed to identify water quality trends and their socio-environmental drivers for coastal management and watershed restoration. This study provides the first long-term assessment of fecal bacterial pollution in the northwestern Gulf of Mexico using enterococci data spanning the Texas coast from 2009 to 2020. The data were representative of 66 beaches, 169 stations, and over 75,000 samples. Findings demonstrate that 22 beaches are 'hotspots' of pollution and experienced enterococci levels that frequently exceeded the USEPA beach action value. Further, enterococci were correlated with time, population size, and sea level. Weak correlations detected in some counties highlight the multifactorial nature of water quality; additional factors are likely influencing enterococci levels. The correlation with sea level is concerning, as counties vulnerable to sea level rise frequently reported enterococci concentrations exceeding the beach action value. In consideration of sea level rise predictions, targeted studies are needed to pinpoint drivers of fecal pollution.


Assuntos
Praias , Qualidade da Água , Monitoramento Ambiental , Fezes , Golfo do México , Elevação do Nível do Mar , Texas , Microbiologia da Água , Poluição da Água/análise
2.
Environ Sci Technol ; 55(8): 4709-4719, 2021 04 20.
Artigo em Inglês | MEDLINE | ID: mdl-33683875

RESUMO

The multidecadal expansion of northern Gulf of Mexico continental shelf hypoxia is a striking example of the adverse effects of anthropogenic nutrient enrichment on coastal oceans. Increased nutrient inputs and widespread shelf hypoxia have resulted in numerous dissolved oxygen (DO) water quality problems in nearshore coastal waters of Louisiana. A large hydrographic dataset compiled from research programs spanning 30 years and the three-dimensional hydrodynamic-biogeochemical model CGEM (Coastal Generalized Ecosystem Model) were integrated to explore the interconnections of low DO waters across the continental shelf to nearshore coastal waters of Louisiana. Cross-shelf vertical profiles showed contiguous low DO bottom waters extending from the shelf to coastal waters nearly every year in the 30+ year time series, which were concurrent with strong cross-shelf pycnoclines. A threshold Brunt-Väisälä frequency of 40 cycles h-1 was critical to maintaining the cross-shelf subpycnocline layers and facilitating the formation of a contiguous low DO water mass. Field observations and model simulations identified periods of wind-driven bottom water upwelling lasting between several days to several weeks, resulting in both physical advection of oxygen-depleted offshore waters to the nearshore and enhanced nearshore stratification. Both the upwelling of low DO bottom waters and in situ respiration were of sufficient temporal and spatial extent to drive DO below Louisiana's DO water quality criteria. Basin-wide nutrient management strategies aimed at reducing nutrient inputs and shelf hypoxia remain essential to improving the nearshore coastal water quality across the northern Gulf of Mexico.


Assuntos
Ecossistema , Oxigênio , Golfo do México , Humanos , Hipóxia , Louisiana , Oceanos e Mares , Oxigênio/análise
3.
Ecotoxicol Environ Saf ; 214: 112098, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33662787

RESUMO

The Deepwater Horizon blowout resulted in the second-largest quantity of chemical dispersants used as a countermeasure for an open water oil spill in the Gulf of Mexico. Of which, the efficacy of dispersant as a mitigation strategy and its toxic effects on aquatic fauna remains controversial. To enhance our understanding of potential sub-lethal effects of exposure to chemically dispersed-oil, sub-adult red drum (Sciaenops ocellatus) were continuously exposed to a Corexit 9500: DWH crude oil chemically enhanced water accommodated fraction (CEWAF) for 3-days and transcriptomic responses were assessed in the liver. Differential expressed gene (DEG) analysis demonstrated that 63 genes were significantly impacted in the CEWAF exposed fish. Of these, 37 were upregulated and 26 downregulated. The upregulated genes were primarily involved in metabolism and oxidative stress, whereas several immune genes were downregulated. Quantitative real-time RT-PCR further confirmed upregulation of cytochrome P450 and glutathione S-transferase, along with downregulation of fucolectin 2 and chemokine C-C motif ligand 20. Ingenuity Pathway Analysis (IPA) predicted 120 pathways significantly altered in the CEWAF exposed red drum. The aryl hydrocarbon receptor pathway was significantly activated, while pathways associated with immune and cellular homeostasis were primarily suppressed. The results of this study indicate that CEWAF exposure significantly affects gene expression and alters signaling of biological pathways important in detoxification, immunity, and normal cellular physiology, which can have potential consequences on organismal fitness.


Assuntos
Perciformes/fisiologia , Poluição por Petróleo , Petróleo/toxicidade , Transcriptoma/fisiologia , Poluentes Químicos da Água/toxicidade , Animais , Peixes , Perfilação da Expressão Gênica , Golfo do México , Lipídeos , Fígado/química , Poluição por Petróleo/análise , Água/análise
4.
Zootaxa ; 4903(4): zootaxa.4903.4.1, 2021 Jan 11.
Artigo em Inglês | MEDLINE | ID: mdl-33757074

RESUMO

Species and genera of Bairdiidae can be difficult to discriminate, because of the somewhat limited morphological range of the carapace and limbs and the prevalence of homeomorphy. Attention to the esophageal flapper valve, an uncalcified but relatively well sclerotized structure, may contribute to more reliable identifications. Living species of Neonesidea exhibit sufficient variability in the architecture of this structure to suggest that it may have taxonomic value. Twelve named and three new species are examined to test this premise: N. bacata, N. caraionae n. sp., N. decipiens, N. credibilis n. sp., N. forea n. sp., N. edentulata, N. gerda, N. holdeni, N. longisetosa, N. manningi, N. mediterranea, N. omnivaga, N. plumulosa, N. schulzi, N. tenera. The geographic range of N. gerda is extended across the Gulf of Mexico, while the ranges of N. longisetosa and N. dinochelata are restricted. This supplemental information helps to clarify the relationships of several poorly known species from carbonate environments of Bermuda, the Bahamas, Florida, the Gulf of Mexico, and the Caribbean.


Assuntos
Crustáceos , Animais , Região do Caribe , Golfo do México , Índias Ocidentais
5.
Mar Pollut Bull ; 166: 112214, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33711603

RESUMO

Age, growth, mortality, and polycyclic aromatic hydrocarbons (PAHs) in roughtongue bass (Pronotogrammus martinicensis) were examined in the northern Gulf of Mexico following the 2010 Deepwater Horizon oil spill. Fish (N = 1090) were collected from September 2014 to July 2015 from the Alabama Alps (54 km from the spill site) and Roughtongue Reef (111 km from the spill site). Sites were dominated by the 2010 year-class. Growth rates were significantly lower for fish from Alabama Alps compared to Roughtongue Reef (p < 0.001) and likely linked to proximity of the Mississippi River discharge. Mean total PAH ± SD was 50 ± 52.6 and ranged from 0 to 220 ppb. These PAH levels were below a 300-ppb minimum effect level and not significantly different between sites. The dominant 2010 year-class, low PAH levels, and similar growth rates to pre-spill measures indicated that the Deepwater Horizon oil spill had little effect on roughtongue bass.


Assuntos
Bass , Poluição por Petróleo , Hidrocarbonetos Policíclicos Aromáticos , Poluentes Químicos da Água , Alabama , Animais , Monitoramento Ambiental , Golfo do México , Mississippi , Poluição por Petróleo/análise , Hidrocarbonetos Policíclicos Aromáticos/análise , Poluentes Químicos da Água/análise
6.
Mar Pollut Bull ; 166: 112196, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33714777

RESUMO

The Rapid Oil Spill Hazard Assessment is presented as a demonstration of concept for a tool providing a framework for managers and planners to assess potential impact areas of oil spills. The tool consists of precomputed oil spill scenarios derived from the analysis of twenty years of modeled current data using Self-Organizing Maps to identify 16 representative patterns. These patterns were used to provide boundary conditions for hydrodynamic and wave models to generate higher resolution current fields, used to drive a Lagrangian oil particle transport model creating the most probable oil spill dispersion patterns. To demonstrate the concept, the tool is applied to the Perdido region in the western Gulf of Mexico. A total of 896 oil spill simulations were performed, considering surface and bottom spills, and were stored in a database for easy access to map arrival probabilities and times to be used in risk and vulnerability analysis.


Assuntos
Poluição por Petróleo , Bases de Dados Factuais , Golfo do México , Hidrodinâmica , Probabilidade
7.
Mar Pollut Bull ; 166: 112256, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33735706

RESUMO

Here we report the bleached coral cover and its drivers observed at Alacranes Reef in 2015. Our results show that 2015 was an unprecedented heat stress event. However, we observed low coral bleaching, with the most substantial impact on sites with a 10-20% of coral cover with bleaching. Depth was the most relevant variable related to coral bleaching and the bleaching severity index, with deeper reefs being most affected. Further, our results show that reefs with higher structural complexity based on species composition were among the most affected. We identified that accumulated heat stress and thermal variation in the last 28 days were relevant drivers of coral bleaching. This work highlights the importance of multidimensional frameworks in assessing the spatial variation of coral bleaching, demonstrating the importance of structural habitat variables such as depth in high heat stress events and at a reef scale.


Assuntos
Antozoários , Animais , Recifes de Corais , Ecossistema , Golfo do México , Resposta ao Choque Térmico
8.
J Emerg Manag ; 19(1): 79-92, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33735438

RESUMO

The scope of policy issues surrounding emergency management remains inundated with several social and political challenges. There are specific events that cause added strain which make certain time periods for examining levels of resiliency relevant. The Deepwater Horizon oil spill represents a large-scale, technological disaster. Not only was there a loss of human life, but several community impacts also exist with the oil having spewed out into the water. Still, what impacts-ie, attitudes, beliefs, and behaviors-are associated with varying population groups that may be more vulnerable than others? Examining the connection between social capital and political trust is, thus, paramount as prior studies have documented that if resiliency networks are disrupted, there will be a lasting impact upon the community. This research extends the limited understanding of case-based perceptions of social and political vulnerability regarding disaster responsibility.


Assuntos
Desastres , Poluição por Petróleo , Capital Social , Golfo do México , Humanos , Poluição por Petróleo/efeitos adversos
9.
Mar Pollut Bull ; 165: 112092, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33556647

RESUMO

Sunken oil is often difficult to detect, and few oil spill models are designed to locate and track such oil. Therefore, the multi-modal Bayesian inferential sunken oil model, SOSim (Subsurface Oil Simulator), was expanded in this work for use during emergency response and damage assessment. Rather than requiring hydrodynamic data as input, SOSim v2 accepts available field concentration data, along with default or custom bathymetric data, for inference of the location and trajectory of sunken oil. Novel aspects include inference based on bathymetry and the Coriolis Effect, by constructing a prior likelihood function from sampled bathymetric data, scaled proportionally with field concentration data. SOSim v2 is demonstrated versus field data on the ITB DBL-152 oil spill in the Gulf of Mexico, with sensitivity analysis. Results suggest that the inferential approach presented can be effective for modeling relatively slow-moving pollutant masses such as sunken oil, when field concentration data are available.


Assuntos
Poluição por Petróleo , Teorema de Bayes , Golfo do México
10.
Mar Pollut Bull ; 165: 112025, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33571788

RESUMO

Marine snow formation and vertical transport are naturally occurring processes that carry organic matter from the surface to deeper waters, providing food and sequestering carbon. During the Deepwater Horizon well blowout, oil was incorporated with marine snow aggregates, triggering a Marine Oil Snow (MOS) Sedimentation and Flocculent Accumulation (MOSSFA) event, that transferred a significant percentage of the total released oil to the seafloor. An improved understanding of processes controlling MOS formation and MOSSFA events is necessary for evaluating their impacts on the fate of spilled oil. Numerical models and predictive tools capable of providing scientific support for oil spill planning, response, and Natural Resource Damage Assessment are being developed to provide information for weighing the ecological trade-offs of response options. Here we offer considerations for oil spill response and recovery when assessing the potential for a MOSSFA event and provide tools to enhance decision-making.


Assuntos
Poluição por Petróleo , Poluentes Químicos da Água , Carbono , Sedimentos Geológicos , Golfo do México , Poluição por Petróleo/análise , Poluentes Químicos da Água/análise
11.
Mar Pollut Bull ; 165: 112078, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33581570

RESUMO

When spilled oil collects at depth, questions as to where and when to dispatch response equipment become daunting, because such oil may be invisible by air, and underwater sensing technology is limited in coverage and by underwater visibility. Further, trajectory modeling based on previously recorded flow field data may show mixed results. In this work, the Bayesian model, SOSim, is modified to locate and forecast the movement of submerged oil, with confidence bound, by inferring model parameters based on any available field concentration data and the output of one or more deterministic trajectory models. Novel aspects include specification of a prior likelihood function, and generation of results in 3-D from data in the 2-D density space of the isopycnal layer containing oil. The model is demonstrated versus data collected following the Deepwater Horizon spill. This new inferential modeling approach appears complimentary to deterministic methods when field concentration data are available.


Assuntos
Poluição por Petróleo , Teorema de Bayes , Previsões , Golfo do México
12.
J Environ Manage ; 284: 112019, 2021 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-33540198

RESUMO

Fertilizers and manure applied to cropland to increase yields are often lost via surface erosion, soil leaching, and runoff, increasing nutrient loads in surface and sub-surface waters, degrading water quality, and worsening the 'dead zone' in the Gulf of Mexico. We leverage spatial and temporal variation in agricultural practices and precipitation events to examine how these factors affect stream total phosphorus (TP) concentrations and loads in the Sugar River (Wisconsin), recently listed as impaired. To perform our analysis, we first collected water quality data from 1995 to 2017 from 40 sites along the Sugar River and its tributaries. Starting in 2004, three dairy farms expanded to become concentrated animal feeding operations (CAFOs) in this watershed. We then estimated how time of year, stream position, discharge volume, and proximity to the newly expanded CAFOs affected TP concentrations and loads. Total P concentrations, which ranged from 0.02 to 1.4 mg/L and often exceeded the EPA surface water standard of 0.1 mg/L, increased with increases in stream discharge and proximity to dairy operations, peaking in early spring to mid-summer coincident with extreme precipitation events. Our empirical analysis also shows that TP concentrations downstream from the newly permitted CAFOs increased by 19% relative to upstream concentrations. When examining total daily phosphorus loads (concentration × discharge) from this 780 km2 watershed, we found that loads ranged from 5.88 to 4801 kg. Compared to upstream TP loads, those downstream from the CAFOs increased by 91% after the expansions - over four times that of concentration increases - implying that the rate of downstream phosphorus transfer has increased due to CAFO expansion. Our results argue for standards that focus on loads rather than concentrations and monitoring that includes peak events. As agriculture intensifies and extreme rainfall events become more frequent, it becomes increasingly important to limit soil and TP runoff from manure and fertilizer. Siting CAFOs carefully, limiting their size, and improving farming practices in proximity to CAFOs in spring and early summer could considerably reduce nutrient loads.


Assuntos
Monitoramento Ambiental , Fósforo , Agricultura , Animais , Golfo do México , Fósforo/análise , Movimentos da Água , Wisconsin
13.
Mar Pollut Bull ; 164: 112076, 2021 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-33529879

RESUMO

Following the Deepwater Horizon oil spill of 2010, large amounts of biodegraded oil (petrocarbon) sank to the seafloor. Our objectives were to 1) determine post-spill isotopic values as the sediments approached a new baseline and 2) track the recovery of affected sediments. Sediment organic carbon δ13C and Δ14C reached a post-spill baseline averaging -21.2 ± 0.9‰ (n = 129) and -220 ± 66‰ (n = 95). Spatial variations in seafloor organic carbon baseline isotopic values, 13C and 14C, were influenced by river discharge and hydrocarbon seepage, respectively. Inverse Distance Weighting of surface sediment Δ14C values away from seep sites showed a 50% decrease in the total mass of petrocarbon, from 2010 to 2014. We estimated a rate of loss of -2 × 109 g of petrocarbon-C/year, 2-11% of the degradation rates in surface slicks. Despite the observed recovery in sediments, lingering residual material in the surface sediments was evident seven years following the blowout.


Assuntos
Poluição por Petróleo , Poluentes Químicos da Água , Monitoramento Ambiental , Sedimentos Geológicos , Golfo do México , Hidrocarbonetos/análise , Poluição por Petróleo/análise , Poluentes Químicos da Água/análise
14.
Mar Pollut Bull ; 164: 112074, 2021 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-33540275

RESUMO

The Deepwater Horizon oil spill of 2010 brought the ecology and health of the Gulf of Mexico to the forefront of the public's and scientific community's attention. Not only did we need a better understanding of how this oil spill impacted the Gulf of Mexico ecosystem, but we also needed to apply this knowledge to help assess impacts from perturbations in the region and guide future response actions. Phytoplankton represent the base of the food web in oceanic systems. As such, alterations of the phytoplankton community propagate to upper trophic levels. This review brings together new insights into the influence of oil and dispersant on phytoplankton. We bring together laboratory, mesocosm and field experiments, including insights into novel observations of harmful algal bloom (HAB) forming species and zooplankton as well as bacteria-phytoplankton interactions. We finish by addressing knowledge gaps and highlighting key topics for research in novel areas.


Assuntos
Poluição por Petróleo , Poluentes Químicos da Água , Animais , Ecossistema , Golfo do México , Fitoplâncton , Poluentes Químicos da Água/toxicidade
15.
Aquat Toxicol ; 233: 105773, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33610857

RESUMO

The 2010 Deepwater Horizon (DWH) crude oil spill, among the largest environmental disasters in U.S. history, affected numerous economically important fishes. Exposure to crude oil can lead to reduced cardiac function, limiting oxygen transport, ATP production, and aerobic performance. However, crude oil exposure is not the only stressor that affects aerobic performance, and increasing environmental temperatures are known to significantly increase metabolic demands in fishes. As the DWH spill was active during warm summer months in the Gulf of Mexico, it is important to understand the combined effects of oil and temperature on a suite of metabolic parameters. Therefore, we investigated the effects of 24h crude oil exposure on the aerobic metabolism and hypoxia tolerance of red drum (Sciaenops ocellatus) following 3 week chronic exposure to four ecologically relevant temperatures (18 °C, 22 °C, 25 °C, 28 °C). Our results show that individuals acclimated to higher temperatures had significantly higher standard metabolic rate than individuals at lower temperatures, which resulted in significantly decreased critical oxygen threshold and reduced recovery from exercise. As predicted, crude oil exposure resulted in lower maximum metabolic rates (MMR) across the temperature range, and a significantly reduced ability to recover from exercise. The lowest temperature acclimation showed the smallest effect of oil on MMR, while the highest temperature showed the smallest effect on exercise recovery. Reduced respiratory performance and hypoxia tolerance are likely to have meaningful impacts on the fitness of red drum, especially with climate-induced temperature increases and continued oil exploration in the Gulf of Mexico.


Assuntos
Perciformes/fisiologia , Poluição por Petróleo/análise , Petróleo/toxicidade , Hidrocarbonetos Policíclicos Aromáticos/toxicidade , Respiração/efeitos dos fármacos , Temperatura , Poluentes Químicos da Água/toxicidade , Animais , Metabolismo Energético/efeitos dos fármacos , Golfo do México , Água do Mar/química
16.
J Parasitol ; 107(1): 59-73, 2021 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-33535234

RESUMO

Cardicola Short, 1953 is the most speciose aporocotylid genus (35 species) and includes marine and estuarine species of fish blood flukes that infect "higher ray-finned fishes" (Euteleostei). Several clades within Cardicola are recovered in phylogenetic analyses of the large subunit ribosomal DNA (28S), but morphological synapomorphies for those nucleotide-based clades remain elusive. The type species, Cardicola cardiocola (Manter, 1947) Short, 1953, has not been recollected in 73 yr and the original description was incomplete; making a genus revision challenging because of the ambiguous systematic position of its type species. Herein, we redescribe C. cardiocola by using the holotype (USNM 1337732) and new specimens collected from the type host, jolthead porgy, Calamus bajonado (Sparidae), from nearby the type locality. It differs from its congeners by the combination of having a body that is 5 times longer than wide, an anterior sucker with concentric rows of spines, 2-6 tegumental body spines per row, an esophageal gland that is 22-43% of the esophageal length, a testis that is 3-5 times longer than wide and that fills the intercecal space, a vitelline duct connecting to the anterior aspect of the oötype, an ascending uterus that lacks any coil, a descending uterus yielding a single coil, an obvious cirrus sac separated by constriction from the seminal vesicle, a tegumental protrusion surrounding the terminal end of cirrus sac, and a male genital pore that is posterior to the remainder of the genitalia. We also describe a new congener infecting the heart of yellowedge grouper, Hyporthodus flavolimbatus (Serranidae), from the Gulf of Mexico. It differs from its congeners by the combination of having an anterior sucker that does not extend beyond the anterior body margin, 2-5 tegumental body spines per row, posterior ceca that are 9 times length of the anterior ceca and that lack any coil, a testis that is 3 times longer than wide and that does not fill the intercecal space, an ovary that is >60% of the body width, a vitelline duct that connects to the anterior aspect of the oötype, a uterus that is >10% of the body width and that extends posterior to all genitalia, and a rounded posterior body margin. It is the first species of Cardicola to be described from a grouper (Serranidae). The 28S and internal transcribed spacer 2 phylogenetic analyses recovered the new species as a distinct lineage within the clade of Cardicola spp.


Assuntos
Bass/parasitologia , Doenças dos Peixes/parasitologia , Trematódeos/classificação , Infecções por Trematódeos/veterinária , Animais , Teorema de Bayes , Doenças dos Peixes/epidemiologia , Florida/epidemiologia , Golfo do México/epidemiologia , Coração/parasitologia , Filogenia , Prevalência , Trematódeos/anatomia & histologia , Trematódeos/genética , Infecções por Trematódeos/epidemiologia , Infecções por Trematódeos/parasitologia
17.
Ecotoxicology ; 30(2): 311-322, 2021 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-33447940

RESUMO

As apex predators, blacktip sharks (Carcharhinus limbatus) are highly susceptible to biomagnified mercury (Hg) particularly in the Gulf of Mexico (GOM), which is known to contain fishes and invertebrates with elevated Hg levels. Blacktip sharks occur in the GOM year-round and are heavily fished both commercially and recreationally, but little is known about how Hg affects the species. In this study, blood, muscle, liver, and kidney samples were collected from neonatal (n = 57) and juvenile (n = 13) blacktip sharks in Charlotte Harbor, Florida. Hg concentrations in neonates and juveniles were found to be elevated in muscle (mean ± SE = 0.59 ± 0.23 mg kg-1), liver (0.39 ± 0.29 mg kg-1), kidney (0.56 ± 0.25 mg kg-1), and blood (0.059 ± 0.041 mg kg-1) compared to other local shark species and conspecifics from other areas. Blood plasma chemistry, hematology, and liver histology were evaluated to assess the relationship between Hg and tissue damage. Plasma chemistry parameters alanine aminotransferase (ALT) and phosphorus (PHOS) were not correlated with tissue Hg or liver condition index. Hematological effects were also not correlated with tissue Hg. However, melanomacrophage presence and lipid deposition, evaluated as part of histopathological analysis, were found to exhibit a statistically significant association with concentrations of Hg in tissue and ALT levels. These results suggest that Hg exposure potentially had a negative effect on the livers of the blacktip sharks evaluated in the present study.


Assuntos
Mercúrio , Tubarões , Animais , Florida , Golfo do México , Humanos , Recém-Nascido , Mercúrio/análise , Mercúrio/toxicidade , Músculos/química
18.
Environ Manage ; 67(2): 384-397, 2021 02.
Artigo em Inglês | MEDLINE | ID: mdl-33432500

RESUMO

Tidal marshes are increasingly vulnerable to degradation or loss from eutrophication, land-use changes, and accelerating sea-level rise, making restoration necessary to recover ecosystem services. To evaluate effects of restoration planting density and sea-level rise on ecosystem function (i.e., nitrogen removal), we restored three marshes, which differed in elevation, at Weeks Bay National Estuarine Research Reserve, Alabama, USA and planted them with Juncus roemerianus sods at 0, 25, 50, 75, or 100% initial cover. We simulated future sea level using passive weirs that increased flooding during low tide. Because additional species emerged shortly after transplantation, we also tested for treatment effects on community structure. In all marshes, species richness increased following restoration, regardless of treatments, while relative abundances of new species tended to increase with increasing initial cover. Plant percent cover increased with increasing initial cover in all marshes, with similar vegetated cover at 50, 75, and 100% after 3 years in the highest elevation marsh. Porewater dissolved inorganic nitrogen concentrations ([DIN]) decreased with increasing initial cover in all marshes, and were significantly lower in 50, 75, and 100% treatments than 0 or 25% after 1 year. Furthermore, [DIN] was similarly low among 50, 75, and 100% treatments when elevation capital was highest. These results suggest that intermediate initial cover (50%) can recover plant cover and promote nitrogen removal when elevation capital is adequate at relatively lower labor and material costs than planting at higher cover, thereby maximizing restoration outcomes in the face of low to moderate sea-level rise.


Assuntos
Ecossistema , Áreas Alagadas , Alabama , Golfo do México , Elevação do Nível do Mar
19.
Environ Sci Technol ; 55(3): 1566-1575, 2021 02 02.
Artigo em Inglês | MEDLINE | ID: mdl-33432817

RESUMO

Demand for biofuel production driven by the Renewable Fuel Standard (RFS2) has coincided with increased land in corn production and increasing nitrogen (N) loss to the Gulf of Mexico. Diversifying cropland with perennial energy crops (miscanthus and switchgrass) may reduce N loss and improve water quality. However, the extent of these benefits depends on the mix of biomass feedstocks (corn stover, perennials) incentivized by the RFS2 and the extent to which energy crops displace N-intensive row crops. We developed an integrated economic-biophysical model to quantify the water quality impacts of three potential policy scenarios that provided corn ethanol at levels before the RFS2 (RFS1 baseline); 15 billion gallons of corn ethanol (corn ethanol only); or 16 billion gallons of cellulosic ethanol in addition to corn ethanol (corn + cellulosic ethanol). Our results showed that economically optimal locations for perennial energy crop production were distributed across idle cropland with lower intrinsic N loss than active cropland. We found stover removal incentivized by the RFS2 offset N loss benefits of perennial energy crops. This finding suggests that targeted incentives for N loss reduction are needed to supplement the RFS2 to induce displacement of N-intensive row crops with energy crops to reduce N losses.


Assuntos
Rios , Qualidade da Água , Biocombustíveis , Golfo do México , Mississippi , Padrões de Referência , Zea mays
20.
PLoS One ; 16(1): e0243478, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33395404

RESUMO

This study provides regional-scale data on drivers of horseshoe crab (Limulus polyphemus) presence along the northcentral Gulf of Mexico coast and has implications for understanding habitat suitability for sparse horseshoe crab populations of conservation concern worldwide. To collect baseline data on the relationship between environmental factors and presence of horseshoe crabs, we surveyed four sites from the Fort Morgan peninsula of Mobile Bay, Alabama (AL) to Horn Island, Mississippi (MS). We documented number, size and sex of live animals, molts, and carcasses as metrics of horseshoe crab presence and demographics for two years. Data were compared to in situ and remotely sensed environmental attributes to assess environmental drivers of occurrence during the time of study. Overall, greater evidence of horseshoe crab presence was found at western sites (Petit Bois and Horn Islands) compared to eastern sites (Dauphin Island, Fort Morgan peninsula), mediated by a combination of distance from areas of high freshwater discharge and interannual variation in weather. Higher sex ratios also were found associated with higher occurrence, west of Mobile Bay. Land cover, particularly Bare Land and Estuarine Emergent Wetland classes that are common to western sites, was most predictive of live animal and to some extent carcass occurrence. Our findings suggest that small-scale variation in habitat quality can affect occurrence of horseshoe crabs in sparse populations where density is not a limiting factor. Data from molts and carcasses were informative to supplement live animal data and may be useful to enhance ecological assessment and support conservation and management in regions with sparse populations.


Assuntos
Meio Ambiente , Caranguejos Ferradura/fisiologia , Animais , Baías , Tamanho Corporal , Clima , Geografia , Golfo do México , Caranguejos Ferradura/anatomia & histologia , Modelos Lineares , Rios , Razão de Masculinidade , Inquéritos e Questionários , Fatores de Tempo
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