Search USGS⌕ Search

SEARCH · Search USGS

Results for “Coasts”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 667 records · Page 37Linked to original sources
USGS2017

Characterization of microsatellite loci for the Gulf Coast waterdog (Necturus beyeri) using paired-end Illumina shotgun sequencing and cross-amplification in other Necturus

Amphibians are one of the most threatened groups of vertebrates (Stuart et al. 2004; Wake and Vredenburg 2008), and the application of molecular techniques to amphibian ecology and genetics has dramatically improved our ability to conserve species and populations (see Shaffer et al. [2015] for review). Microsatellites, tandem repeats of two to six nucleotides in the nuclear genome, are highly variable molecular markers that can be used to describe gene flow and genetic diversity, each of which is positively correlated with population persistence (Allendorf and Luikart 2007; Allentoft and O’Brien 2010; Avise 2004; Selkoe and Toonen 2006). Microsatellite loci have frequently been applied to studies involving terrestrial and pond breeding amphibians (Emel and Storfer 2012), but fewer studies have focused on taxa inhabiting lotic systems (Emel and Storfer 2012). For example, studies characterizing microsatellite loci are completely lacking for a group of permanently aquatic salamanders, the waterdogs and mudpuppies (Family Proteidae, Genus Necturus ) (Rafinesque 1819). The genus Necturus consists of several species of perennibranch salamanders that can be found throughout many freshwater streams, rivers, and lakes in North America (Petranka 1998). Some authorities recognize five species (Crother 2012; Petranka 1998), including the Mudpuppy ( Necturus maculosus ) (Rafinesque 1819), Gulf Coast Waterdog ( N. beyeri ) (Viosca 1937), Black Warrior Waterdog ( N. alabamensis ) (Viosca 1937), Neuse River Waterdog ( N. lewisi ) (Brimley 1924), and Dwarf Waterdog ( N. punctatus ) (Gibbes 1850). This taxonomy also recognizes two subspecies within N. maculosus , including the Common Mudpuppy ( N. m. maculosus ) and the Red River Waterdog ( N. m. louisianensis ) (Crother 2012; Petranka 1998; Schmidt 1953). Other authorities suggest that there are six or seven species within Necturus (Collins 1990; Frost 2016; Powell et al. 2016). These more diverse schemes recognize each of the aforementioned five species while also elevating the Red River Waterdog ( N. louisianensis ) (Collins 1990; Frost 2016; Powell et al. 2016; Viosca 1938) and Löding’s Waterdog ( N. lödingi or N. cf. beyeri ) (Bart et al. 1997; Guyer 2005a; Viosca 1938). Allozyme work by Guttman et al. (1990) suggests that there is at least one cryptic species of Necturus in drainages east of the Mobile Basin and south of the Alabama River, and both Bart et al. (1997) and Guyer (2005a) advise that these populations should be referred to as N. cf. beyeri . However, until range wide studies incorporating genetic and other data are published, we will follow the five species taxonomy outlined by Crother (2012) while acknowledging that certain taxa, such as N. maculosus and N. beyeri , may require systematic revision.

Herpetological Review↗
USGS1993

Spectral reflectance and canopy structure characteristics of gulf coast wetland vegetation types

Field measurements of canopy structure and species composition are related to spectral reflectance measurements taken with a radiometer over a number of marsh sites. Marsh vegetation types are discussed in terms of their characteristic canopy structure and phenology; the influence of these characteristics on spectral reflectance will be examined. Vegetation types that are discussed include Panicum hemitomon (fresh marsh) Spartina patens (brackish marsh), Spartina alterniflora and Juncus roemerianus (saline marsh). This work is part of the high resolution component of a study to develop methods to spectrally discriminate and monitor the wetlands of the gulf coast.

Louisiana↗
USGS2021

Introduced mangroves along the coast of Moloka‘i, Hawai‘i may represent novel habitats for megafaunal communities

Mangrove forests are prevalent along tropical/subtropical coastlines and provide valuable ecosystem services including coastline stabilization, storm impact reduction, and enhanced coastal productivity. However, mangroves were absent from the Hawaiian Islands and their introduction to Moloka‘i in 1902 has provided an opportunity to examine their unique influence on coastal landscapes. Previous studies indicate an inability of native detritivores to utilize tannin-rich substrates, yielding poor cycling of mangrove-derived detritus in Hawaiian tidal zones. We hypothesize that in addition to altering detrital inputs, introduced mangroves facilitate the persistence of introduced species in the Hawaiian coastal zone by providing novel habitat for juvenile megafauna. To determine whether mangrove-dominated tidal zones harbor megafaunal assemblages distinct from open sandflats, we sampled in two mangrove (M1 and M2) and two adjacent sandflat (S1 and S2) sites along the southern coast of Moloka‘i, where the most mature mangrove forests occur in Hawai‘i. There were no statistical differences in total abundances between M1 and M2 or S1 and S2; therefore, results from individual deployments were pooled across the sites in order to conduct between-habitat (mangrove vs. sandflat) comparisons. Our mangrove study site had significantly higher abundances of megafauna, including several shrimp and crab species, compared to the sandflat site. The community composition within the mangrove site differed from the sandflat site, including higher abundances of non-native mangrove crabs ( Scylla serrata ), as well as native fish Bathygobius cocosensis and crustaceans ( Thalamita crenata , Palaemon pacificus , P. debilis ) than in the sandflat site, indicating that the mangrove site may provide niches for both invasive and native species. In addition, mean body length for several similar species was smaller in the mangrove site than in the sandflat site, suggesting that these mangroves may be providing a habitat for juvenile species. While our study was spatially limited to two mangrove and two adjacent sandflat sites, our results suggest that introduced mangroves in Moloka‘i may support small-bodied, native, and non-native megafauna, influencing coastal Hawaiian trophic dynamics. Our case study provides a baseline for megafaunal fish and invertebrate communities present prior to non-native mangrove removal as well as for monitoring potential community changes following expansion of mangrove habitats due to climate change.

Hawaii↗
USGS1974

Yachats Basalt: An upper Eocene differentiated volcanic sequence in the Oregon Coast Range

The name Yadials Basalt is proposed for a sequence of largely subacrial basalt flows and breccias and associated dikes of late Eocene age that arc exposed along the central Oregon coast. These volcanic rocks, which have a maximum thickness of 750 m, are underlain by marine siltstonc of late Eocene age and overlain by marine siltstone and basaltic sandstone, also of late Eocene age. The siltstone contains a foraminiferal fauna indicative of a moderately deepwatcr marine environment, indicating that local uplift preceded the extrusion of the flows and local subsidence followed. The Yachats Basalt varies widely in composition. Although the bulk of the extrusive rocks and dikes arc basalt, some grade in composition to basaltic andcsite and andcsite; a few dikes are rhyodacitic. Most of the rocks arc porphyritic with phcnocrysts of labradorite and less commonly augite and olivine. Typical flow rock contains 50 percent SiO 2 and are characterized by high alumina, alkali, titania, and phosphate content. The wide range in composition and porphyritic character of the Yachats Basalt and the abundance of multiple dikes suggest that the magma that produced these rocks was differentiated in the upper crust before extrusion. The Yachats Basalt, and correlative upper Eocene volcanic rocks in western Oregon and Washington, lie along a generally north-trending belt. The predominance of normal faulting in western Oregon and Washington and on the adjacent continental shelf during post mid-late Eocene time suggests that the volcanics were extruded along a zone of tensional rifting. They do not appear to be related to conventional plate models for continental margins that arc characterized by deep trenches flanked by island arcs.

Oregon↗
USGS1976

Fission-track ages of sphene and apatite of granitic rocks of the Salinian block, Coast Ranges, California

Fission-track ages have been determined on apatite and sphene from granitic rocks of the Salinian block, California Coast Ranges. The 26 age determinations on sphene range between 68 and 93 m.y. The 24 age determinations on apatite have a greater variation, ranging from 3 to 74 m.y. None of the fission-track ages appear to reflect times of intrusion. The Pinnacles volcanic field of Miocene age apparently has thermally affected apatite ages in the central Gabilan and eastern Santa Lucia Ranges. Reduced apatite ages in the area between the Farallon Islands and the Monterey Peninsula may also be the result of Miocene volcanic activity, but the evidence is less conclusive. Fission-track ages on sphene correlate closely with previously determined potassium-argon ages on hornblende and biotite but show an unexplained "bimodal" age distribution, the ages in the Gabilan and Santa Lucia Ranges being slightly, but consistently, lower (avg 75 m.y.) than the ages for terrane to the north and south (avg 85 m.y.) The overall pattern of the sphene and apatite fission-track ages, distinctly different from that of the central Sierra Nevada, may be a "fingerprint" of correlative value in locating the parent terrane of the "ripped-off" Salinian block.

California↗
USGS2025

Potential for co-production of lithium and geothermal resources in the Gulf Coast

Lithium brine extractions and geothermal resource developments often are not economically viable as standalone projects, but they May become cost effective when the potential for both resources exist within the same reservoir. Subsurface datasets were analyzed to identify areas in the U.S. Gulf Coast region with potential for lithium brine and geothermal heat recovery. Temperature, lithium brine content, and reservoir quality data for thirty-four depositional units were evaluated using spatial analysis to interpret high-grade areas where both resources likely coexist. For sedimentary geothermal systems, potential resource areas are sorted by resource grade: as low temperature (<90°C, direct use potential), moderate temperature (90–150°C, direct use and electricity generation), and high temperature (>150°C, primarily electricity generation). Lithium resources were defined by Li lithium brine concentrations in parts per million (ppm): low potential (<100ppm), moderate potential (100–200ppm), and high potential (>200ppm). Reservoir quality affects the viability of both resources and is evaluated using interpreted lithofacies that describe the depositional environments of each unit. Using the results, a series of play fairway analysis maps were generated to support regional evaluations of lithium and geothermal resources and to identify areas of interest for detailed, prospect-scale studies.

Alabama, Florida, Georgia, Louisiana, Mississippi,↗
USGS2025

Evaluating the potential of co-located non-petroleum energy resources in the Gulf Coast using play fairwayaAnalysis

Geological resources critical to the energy transition, such as sedimentary geothermal, carbon storage potential, and lithium in brines, commonly struggle for economic feasibility as stand-alone developments but can have greater viability when the potential for more than one of these resources exist within the same reservoir or stacked in different stratigraphic intervals. There may also be instances where development of one resource inhibits development of others and decisions need to be made on how to best prioritize the use of those resources in the subsurface. Subsurface data sets were analyzed and integrated to evaluate the distribution of non-petroleum energy and related resources in the onshore and nearshore U.S. Gulf Coast. Temperature, pressure, brine composition (lithium content), and reservoir quality data for thirty-four depositional units have been compiled and visualized to high-grade areas where multiple resource opportunities likely coexist. For sedimentary geothermal, possible resource areas are defined as low potential (<90°C), moderate potential (90–150°C), and high potential (>150°C). For CO 2 storage, high potential areas exhibit supercritical CO 2 conditions less than 80% of the fracture gradient. Areas with pore pressure between 80% and 100% of the fracture gradient are considered to exhibit moderate potential and areas where the fracture gradient is equal to or greater than 100% are assigned low potential. Lithium resources in brines were defined by lithium concentrations as low potential (<100ppm), moderate potential (100-200ppm), or high potential (>200ppm). Reservoir quality affects the viability of all three of these resources and is evaluated using depositional environment maps of each unit. The resulting play fairway maps can be used for regional scale screening evaluations of these resources and to identify areas of interest where more detailed, prospect-scale studies can be undertaken.

Gulf Coast↗
USGS1986

Habitat Suitability Index Models: Northern pintail (gulf coast wintering)

A review and synthesis of existing information were used to develop a model for evaluating wintering habitat quality for northern pintail (Anas acuta) along the Gulf of Mexico coast. The model is scaled to produce an index between unsuitable habitat) and 1.0 (optimal habitat). Habitat suitability index models are designed for use with the Habitat Evaluation Procedures previously developed by the U.S. Fish and Wildlife Service. Guidelines for model application and techniques for measuring model variables are provided.

FWS/OBS↗
USGS2014

Multiscale habitat selection of wetland birds in the northern Gulf Coast

The spatial scale of habitat selection has become a prominent concept in ecology, but has received less attention in coastal ecology. In coastal marshes, broad-scale marsh types are defined by vegetation composition over thousands of hectares, water-level management is applied over hundreds of hectares, and fine-scale habitat is depicted by tens of meters. Individually, these scales are known to affect wetland fauna, but studies have not examined all three spatial scales simultaneously. We investigated wetland bird habitat selection at the three scales and compared single- and multiscale models. From 2009 to 2011, we surveyed marsh birds (i.e., Rallidae, bitterns, grebes), shorebirds, and wading birds in fresh and intermediate (oligohaline) coastal marsh in Louisiana and Texas, USA. Within each year, six repeated surveys of wintering, resident, and migratory breeding birds were conducted at > 100 points ( n = 304). The results revealed fine-scale factors, primarily water depth, were consistently better predictors than marsh type or management. However, 10 of 11 species had improved models with the three scales combined. Birds with a linear association with water depth were, correspondingly, most abundant with deeper fresh marsh and permanently impounded water. Conversely, intermediate marsh had a greater abundance of shallow water species, such as king rail Rallus elegans, least bittern Ixobrychus exilis, and sora Porzana carolina. These birds had quadratic relationships with water depth or no relationship. Overall, coastal birds were influenced by multiple scales corresponding with hydrological characteristics. The effects suggest the timing of drawdowns and interannual variability in spring water levels can greatly affect wetland bird abundance.

Estuaries and Coasts↗
USGS2021

Amplified impact of climate change on fine-sediment delivery to a subsiding coast, Humboldt Bay, California

In Humboldt Bay, tectonic subsidence exacerbates sea-level rise (SLR). To build surface elevations and to keep pace with SLR, the sediment demand created by subsidence and SLR must be balanced by an adequate sediment supply. This study used an ensemble of plausible future scenarios to predict potential climate change impacts on suspended-sediment discharge (Q ss ) from fluvial sources. Streamflow was simulated using a deterministic water-balance model, and Q ss was computed using statistical sediment-transport models. Changes relative to a baseline period (1981–2010) were used to assess climate impacts. For local basins that discharge directly to the bay, the ensemble means projected increases in Q ss of 27% for the mid-century (2040–2069) and 58% for the end-of-century (2070–2099). For the Eel River, a regional sediment source that discharges sediment-laden plumes to the coastal margin, the ensemble means projected increases in Q ss of 53% for the mid-century and 99% for the end-of-century. Climate projections of increased precipitation and streamflow produced amplified increases in the regional sediment supply that may partially or wholly mitigate sediment demand caused by the combined effects of subsidence and SLR. This finding has important implications for coastal resiliency. Coastal regions with an increasing sediment supply may be more resilient to SLR. In a broader context, an increasing sediment supply from fluvial sources has global relevance for communities threatened by SLR that are increasingly building resiliency to SLR using sediment-based solutions that include regional sediment management, beneficial reuse strategies, and marsh restoration.

California↗
USGS2018

Setting up and configuring a total station: Version 1.0: Southeast coast network standard operating procedure 1.2.17

The following standard operating procedure (SOP) outlines the process for setting up and configuring a total station to collect accurate x, y, and z coordinate data. Total stations allow accurate spatial data to be collected and tied to a permanent benchmark. These data can be used to detect small geomorphic changes between site surveys. Many different types of total stations and surveying gear are available, and newer models will be available in the future. This SOP outlines basic steps for using the Trimble S6 robotic total station and the TSC3 data collector. These instructions do not cover detailed care and maintenance of the Trimble S6 robotic total station or the TSC3 data collector.

Southeast Coast Network Standard Operating Procedu↗
USGS2026

Expansion trends and impacts of Phragmites australis on the Louisiana Gulf Coast

Invasive plant species pose substantial threats to ecosystem integrity by disrupting ecosystem processes, reducing biodiversity, and complicating restoration and management efforts. Non-native lineages of Phragmites australis are invasive in wetlands across parts of North America, causing declines in the diversity of native wetland plants and disrupting biogeochemical cycles. Despite recognition of these effects, important knowledge gaps remain regarding the spatiotemporal dynamics, environmental drivers, and consequences of Phragmites expansion for native communities. Here, we examined long-term data from the Louisiana Coastwide Reference Monitoring System (CRMS), collected from 2006 to 2023 and spanning 390 sites across nine basins, to quantify basin-specific Phragmites cover trajectories and evaluate their associations with co-occurring native plant cover and soil properties. Louisiana supports both long-established noninvasive and (since ~2000) invasive European P. australis lineages, but CRMS cannot distinguish them; thus, our basin-level trajectories reflect species-level cover dynamics that may integrate lineage-specific turnover. Phragmites dynamics varied markedly among basins over the study period: Phragmites cover decreased in the Mississippi River Delta (initially >25%), whereas the Calcasieu-Sabine, Mermentau, Teche-Vermilion, and Terrebonne basins, each starting with <5%, exhibited positive expansion trends. The remaining four basins maintained low and stable Phragmites cover (<5%) over the study period. These distinct basin-level trajectories may reflect basin-to-basin differences in a hydrogeomorphic setting and associated sediment and nutrient inputs. In basins with positive expansion trends, Phragmites cover was associated with decreases in native plant cover. Overall, Phragmites expansion was positively associated with higher soil nutrients, lower pH, and higher salinity, highlighting key environmental factors that could inform targeted management to prevent or mitigate its expansion. Although Phragmites cover remains low in most basins (<10%), expansion in several basins suggests the value of basin-specific early-warning monitoring to maintain native plant cover and associated ecosystem functions. Our two-step framework offers a transferable monitoring template that integrates Phragmites cover trends (expanding/stable/declining), concurrently measured native plant cover, and key soil and pore-water indicators to flag emerging hotspots and prioritize adaptive management in other estuarine and deltaic systems.

Louisiana↗
USGS2021

Piping plovers demonstrate regional differences in nesting habitat selection patterns along the U.S. Atlantic coast

Habitat studies that encompass a large portion of a species’ geographic distribution can explain characteristics that are either consistent or variable, further informing inference from more localized studies and improving management successes throughout the range. We identified landscape characteristics at Piping Plover nests at 21 sites distributed from Massachusetts to North Carolina and compared habitat selection patterns among the three designated U.S. recovery units (New England, New York–New Jersey, and Southern). Geomorphic setting, substrate type, and vegetation type and density were determined in situ at 928 Piping Plover nests (hereafter, used resource units) and 641 random points (available resource units). Elevation, beach width, Euclidean distance to ocean shoreline, and least-cost path distance to low-energy shorelines with moist substrates (commonly used as foraging habitat) were associated with used and available resource units using remotely sensed spatial data. We evaluated multivariate differences in habitat selection patterns by comparing recovery unit-specific Bayesian networks. We then further explored individual variables that drove disparities among Bayesian networks using resource selection ratios for categorical variables and Welch’s unequal variances t-tests for continuous variables. We found that relationships among variables and their connections to habitat selection were similar among recovery units, as seen in commonalities in Bayesian network structures. Furthermore, nesting Piping Plovers consistently selected mixed sand and shell, gravel, or cobble substrates as well as areas with sparse or no vegetation, irrespective of recovery unit. However, we observed significant differences among recovery units in the elevations, distances to ocean, and distances to low-energy shorelines of used resource units. Birds also exhibited increased selectivity for overwash habitats and for areas with access to low-energy shorelines along a latitudinal gradient from north to south. These results have important implications for conservation and management, including assessment of shoreline stabilization and habitat restoration planning as well as forecasting effects of climate change.

Connecticut, Delaware, Maryland, Massachusetts, ne↗
USGS2024

Management implications of habitat selection by whooping cranes (Grus americana) on the Texas coast

Effective habitat management for rare and endangered species requires a thorough understanding of their specific habitat requirements. Although machine learning models have been increasingly used in the analyses of habitat use by wildlife, the primary focus of these models has been on generating spatial predictions. In this study, we used machine learning models in combination with simulated management actions to guide planning and inform managers. We used data from 61 whooping cranes ( Grus americana ) tagged with GPS telemetry collars between 2009 and 2018 near Aransas National Wildlife Refuge in coastal Texas. We included variables based on topography, land use classification, vegetation height, plant phenology, drought, storm surge events, and both wild and prescribed fires. We then built models at multiple scales: population level, home range level, and roosting and daytime within home range level. We simulated responses to the two primary management actions used to enhance whooping crane habitat on Aransas National Wildlife Refuge: prescribed fire and removal of woody vegetation. At the population and home range scales, land use classification variables had the highest importance values, whereas the combined elevation and bathymetry layer was the most important predictor at both roosting and daytime within home range scales. Our findings revealed that the effects of fire, although generally modest, varied spatially. Areas dominated by estuarine wetlands exhibited higher predicted use within the first months after a fire, whereas those dominated by palustrine wetlands were more likely to be avoided in the immediate postfire years. Our simulation of vegetation removal identified the areas on Aransas National Wildlife Refuge where whooping cranes were predicted to benefit the most if vegetation were removed. These techniques can be used by other researchers wanting to examine and predict the effects of potential management actions on target species habitat.

Texas↗
USGS2019

Evaluation of environmental DNA surveys for identifying occupancy and spatial distribution of Pacific Lamprey (Entosphenus tridentatus) and Lampetra spp. in a Washington coast watershed

Surveys of environmental DNA (eDNA) have become an important and multifaceted tool for monitoring and identifying distributions and occupancy of aquatic species. This tool is attractive because it is powerful, easy to apply, and provides an alternative to traditional field survey methods. However, validating eDNA survey methods against traditional field survey methods is warranted prior to their application. We used eDNA and electrofishing to survey 10 sites in 3 tributaries of the Chehalis River, Washington, to infer distribution and occupancy of Entosphenus tridentatus and Lampetra spp. Both methods produced similar detection rates for E . tridentatus , and Lampetra spp. were detected at slightly greater frequency with eDNA in the Black River and Skookumchuck River. Within each of the three tributaries, eDNA concentration was negatively related to sample distance from the Chehalis River mainstem for E . tridentatus but not for Lampetra spp., which indicates E . tridentatus and Lampetra spp. may be distributed differently within tributaries. Application of lamprey eDNA data to a multiscale occupancy model indicated high probability of detecting eDNA in water samples and quantitative PCR (qPCR) assays. Broad distribution and high detection of E. tridentatus and Lampetra spp. suggest robust populations inhabit the Chehalis River basin. Our findings suggest eDNA surveys may be comparable to electrofishing for informing lamprey occupancy and distributions. Such sampling is efficient and cost‐effective and we anticipate that eDNA surveys will become a valuable tool in addressing key research and monitoring needs for conservation and restoration of lampreys in general.

Washington↗
USGS2009

Sediment storage and transport in Pancho Rico Valley during and after the Pleistocene-Holocene transition, Coast Ranges of central California (Monterey County)

Factors influencing sediment transport and storage within the 156??6 km 2 drainage basin of Pancho Rico Creek (PRC), and sediment transport from the PRC drainage basin to its c. 11000 km 2 mainstem drainage (Salinas River) are investigated. Numeric age estimates are determined by optically stimulated luminescence (OSL) dating on quartz grains from three sediment samples collected from a 'quaternary terrace a (Qta)' PRC terrace/PRC-tributary fan sequence, which consists dominantly of debris flow deposits overlying fluvial sediments. OSL dating results, morphometric analyses of topography, and field results indicate that the stormy climate of the Pleistocene-Holocene transition caused intense debris-flow erosion of PRC- tributary valleys. However, during that time, the PRC channel was backfilled by Qta sediment, which indicates that there was insufficient discharge in PRC to transport the sediment load produced by tributary-valley denudation. Locally, Salinas Valley alluvial stratigraphy lacks any record of hillslope erosion occurring during the Pleistocene-Holocene transition, in that the alluvial fan formed where PRC enters the Salinas Valley lacks lobes correlative to Qta. This indicates that sediment stripped from PRC tributaries was mostly trapped in Pancho Rico Valley despite the relatively moist climate of the Pleistocene-Holocene transition. Incision into Qta did not occur until PRC enlarged its drainage basin by c. 50% through capture of the upper part of San Lorenzo Creek, which occurred some time after the Pleistocene-Holocene transition. During the relatively dry Holocene, PRC incision through Qta and into bedrock, as well as delivery of sediment to the San Ardo Fan, were facilitated by the discharge increase associated with stream-capture. The influence of multiple mechanisms on sediment storage and transport in the Pancho Rico Valley-Salinas Valley system exemplifies the complexity that (in some instances) must be recognized in order to correctly interpret terrestrial sedimentary sequences in tectonically active areas. ?? 2009 John Wiley & Sons, Ltd.

Earth Surface Processes and Landforms↗
USGS2016

Methane emissions from oceans, coasts, and freshwater habitats: New perspectives and feedbacks on climate

Methane is a powerful greenhouse gas, and atmospheric concentrations have risen 2.5 times since the beginning of the Industrial age. While much of this increase is attributed to anthropogenic sources, natural sources, which contribute between 35% and 50% of global methane emissions, are thought to have a role in the atmospheric methane increase, in part due to human influences. Methane emissions from many natural sources are sensitive to climate, and positive feedbacks from climate change and cultural eutrophication may promote increased emissions to the atmosphere. These natural sources include aquatic environments such as wetlands, freshwater lakes, streams and rivers, and estuarine, coastal, and marine systems. Furthermore, there are significant marine sediment stores of methane in the form of clathrates that are vulnerable to mobilization and release to the atmosphere from climate feedbacks, and subsurface thermogenic gas which in exceptional cases may be released following accidents and disasters (North Sea blowout and Deepwater Horizon Spill respectively). Understanding of natural sources, key processes, and controls on emission is continually evolving as new measurement and modeling capabilities develop, and different sources and processes are revealed. This special issue of Limnology and Oceanography gathers together diverse studies on methane production, consumption, and emissions from freshwater, estuarine, and marine systems, and provides a broad view of the current science on methane dynamics of aquatic ecosystems. Here, we provide a general overview of aquatic methane sources, their contribution to the global methane budget, and key uncertainties. We then briefly summarize the contributions to and highlights of this special issue.

Limnology and Oceanography↗