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USGS2000

Pattern and process of land loss in the Mississippi Delta: A spatial and temporal analysis of wetland habitat change

An earlier investigation (Turner 1997) concluded that most of the coastal wetland loss in Louisiana was caused by the effects of canal dredging, that loss was near zero in the absence of canals, and that land loss had decreased to near zero by the late 1990s. This analysis was based on a 15-min quadrangle (approximately 68,000 ha) scale that is too large to isolate processes responsible for small-scale wetland loss and too small to capture those responsible for large-scale loss. We conducted a further evaluation of the relationship between direct loss due to canal dredging and all other loss from 1933–1990 using a spatial scale of 4,100 ha that accurately captures local land-loss processes. Regressions of other wetland loss on canal area (i.e., direct loss) for the Birdfoot, Terrebonne, and Calcasieu basins were not significant. Positive relationships were found for the Breton (r 2 =0.675), Barataria (r 2 =0.47), and Mermentau (r 2 =0.35) basins, indicating that the extent of canals is significantly related to wetland loss in these basins. A significant negative relationship (r 2 =0.36) was found for the Atchafalaya coastal basin which had statistically lower loss rates than the other basins as a whole. The Atchafalaya area receives direct inflow of about one third of the Mississippi discharge. When the data were combined for all basins, 9.2% of the variation in other wetland loss was attributable to canals. All significant regressions intercepted the y-axis at positive loss values indicating that some loss occurred in the absence of canals. Wetland loss did not differ significantly from the coast inland or between marsh type. We agree with Turner that canals are an important agent in causing wetland loss in coastal Louisiana, but strongly disagree that they are responsible for the vast majority of this loss. We conclude that wetland loss in the Mississippi delta is an ongoing complex process involving several interacting factors and that efforts to create and restore Louisiana’s coastal wetlands must emphasize riverine inputs of freshwater and sediments.

Louisiana↗

USGS1996

Shorebird use of South Carolina managed and natural coastal wetlands

While many migrating and wintering shorebird (Charadriiformes) species face declines in quality and quantity of natural stopover sites, diked wetlands managed for shorebirds may provide supplemental habitat. We describe an integrative shorebird-waterfowl management strategy used at Tom Yawkey Wildlife Center on South Island, South Carolina, during 3 winter-spring seasons (1991-93). We compared shorebird use and invertebrate density between diked, managed wetlands and adjacent natural coastal mudflat areas. About 3,000 shorebirds overwintered each year at the site. Migration numbers peaked at 15,000-19,000 during late May. In 1991, shorebird density and absolute numbers were higher ( P < 0.05) in managed wetlands at high tide than natural mudflats at low tide. In 1993, we counted shorebird density at low tide both in managed wetlands and Mother Norton Shoals, the largest natural area. During February, shorebird frequency was higher in Mother Norton Shoals and lower in managed wetlands than expected values based on area ( P < 0.005). In contrast, from March to May, shorebird frequency was higher in managed wetlands and lower in natural mudflats than expected ( P < 0.005 for each month). Invertebrate density from March to May was generally greater in managed wetlands than at Mother Norton Shoals, which may explain shorebird preference during that time. Greater invertebrate density did not explain the pattern in February. Mean water depth in managed wetlands for each shorebird species was <5 cm except for American avocet ( Recurvirostra americana ) which used deeper water ( x̄ = 8.4 cm, SD = 4.5). Results indicate that an integrative shorebird-waterfowl management strategy provides supplemental shorebird habitat at high tide, and managed wetlands can be preferred to local natural mudflat areas at low tide.

South Carolina↗

USGSDate not supplied

Louisiana coastal wetlands: a resource at risk

Approximately half the Nation's original wetland habitats have been lost over the past 200 years. In part, this has been a result of natural evolutionary processes, but human activities, such as dredging wetlands for canals or draining and filling for agriculture, grazing, or development, share a large part of the responsibility for marsh habitat alteration and destruction. Louisiana's wetlands today represent about 40 percent of the wetlands of the continental United States, but about 80 percent of the losses. The State's wetlands extend as much as 130 kilometers inland and along the coast for about 300 kilometers. Not all the wetlands are receding; in fact some wetlands are stable, and others are growing. But, at the present net rate of wetlands loss, Louisiana will have lost this crucial habitat in about 200 years. Considerable effort has been expended, and will continue to be expended, on understanding the processes that control wetlands evolution.

Louisiana↗

USGS1997

Tree rings record 100 years of hydrologic change within a wetland

One of the primary responsibilities of the Water Resources Division of the United States Geological Survey is to monitor the amount and quality of waters in our rivers, lakes, and wetlands. Hydrologists can evaluate these important resources in the present day, but how can they determine what conditions were like in past decades or even centuries? Moreover, are conditions part of a natural cycle or caused primarily by human activities? It is sometimes possible to answer these questions by examining the annual growth rings of trees. Each ring can be assigned an exact year of formation, and yearly differences in ring widths can be used to compare past and present conditions on a flood plain, along a river, or within a wetland. Thus, tree rings provide information that otherwise might be difficult or even impossible to obtain. Hydrology and tree growth were investigated within a small wetland in the Tully Valley of central New York, about 20 miles south of Syracuse. In late 1994 it was noted that some wetland trees were dying, and local residents reported that flow of a small stream draining the wetland seemingly increased and became more brackish since the mid to late 1980s. The wetland is about 3 miles north of an extensive salt mining operation known to have degraded local water quality, but no effects of mining had been confirmed previously near the wetland. The oldest wetland trees started to grow before the onset of mining in 1889, and thus tree-ring studies were undertaken not only to investi-gate recent hydrologic change within the wetland, but also to search for evidence of any other changes during the last 100 years.

New York↗

USGS2005

Using hydrogeomorphic criteria to classify wetlands on Mt. Desert Island, Maine – Approach, classification system, and examples

A wetland classification system was designed for Mt. Desert Island, Maine, to help categorize the large number of wetlands (over 1,200 mapped units) as an aid to understanding their hydrologic functions. The classification system, developed by the U.S. Geological Survey (USGS), in cooperation with the National Park Service, uses a modified hydrogeomorphic (HGM) approach, and assigns categories based on position in the landscape, soils and surficial geologic setting, and source of water. A dichotomous key was developed to determine a preliminary HGM classification of wetlands on the island. This key is designed for use with USGS topographic maps and 1:24,000 geographic information system (GIS) coverages as an aid to the classification, but may also be used with field data. Hydrologic data collected from a wetland monitoring study were used to determine whether the preliminary classification of individual wetlands using the HGM approach yielded classes that were consistent with actual hydroperiod data. Preliminary HGM classifications of the 20 wetlands in the monitoring study were consistent with the field hydroperiod data. The modified HGM classification approach appears robust, although the method apparently works somewhat better with undisturbed wetlands than with disturbed wetlands. This wetland classification system could be applied to other hydrogeologically similar areas of northern New England.

Maine↗

USGS2023

Selenium hazards in the Salton Sea environment—Summary of current knowledge to inform future wetland management

Quaternary marine and continental shales in the western United States are sources of selenium that can be loaded into the aquatic environment through mining, agricultural, and energy production processes. The mobilization of selenium from shales through agricultural irrigation has been recognized since the 1930s; however, discovery of deformities in birds and other wildlife using agricultural habitats during the 1980s spurred studies to determine the extent and effects of the contamination. Through these early studies, researchers determined that biota in the Salton Sea drainage basin was at risk from legacy selenium contamination in the Colorado River watershed. The Salton Sea and its surrounding managed and unmanaged wetlands provide vital inland habitat and trophic support for diverse assemblages of resident and migratory wildlife, and understanding regional selenium hazards for these trust species is a priority for many Federal and State agencies. The modern Salton Sea is a shallow, landlocked saline lake in Riverside and Imperial Counties (not shown) of California that is sustained by irrigation return and perennial river inflow. Changes in water transfer agreements under the 2003 Quantification Settlement Agreement (QSA) have resulted in reduced irrigation flow, declining lake levels, and the evolution of unmanaged wetlands in areas where drains and rivers no longer reach the Salton Sea. These wetlands provide additional habitat for some species of concern, but their potential to increase selenium hazards for trust species is largely unknown. From the 1980s to 2020, efforts to document selenium contamination and effects throughout the region have resulted in a considerable amount of selenium data from the Salton Sea and its surrounding drainage basin; however, no long-term (greater than 20 years), consistent sampling program has been established, and all data have been collected by different entities using a variety of protocols and analytical techniques. This lack of coordination has been previously documented in regional management plans and has led to difficulty in reliably assessing selenium hazards in the Salton Sea environment. This report provides a summary of the available disparate selenium information collected from water, sediment, and biota in the Salton Sea region since the 1980s and to identify data gaps that need to be filled to understand the potential effects of selenium on species of concern, including federally endangered desert pupfish ( Cyprinodon macularius ) and Yuma Ridgway’s Rail ( Rallus obsoletus yumanensis; formerly Yuma Clapper Rail, Rallus longirostris yumanensis ). Available data from the Salton Sea drainage basin show that water from the Colorado River has the lowest selenium concentration of all surface water sources. All other surface water flowing into the Salton Sea has elevated selenium concentrations due to evaporation and evapotranspiration that occurs in agricultural fields and associated water delivery infrastructure or leaching of selenium from irrigated farmland soils. The Salton Sea has lower selenium concentrations because of various biogeochemical processes that recycle selenium into the sediment or volatilize it to the atmosphere; however, these mechanisms are not well defined, and it is not clear if selenium cycling will change in response to possible changes in the oxidation state of the Salton Sea bottom waters as water levels decline. Agricultural drains have the highest average selenium concentrations, but few drains have been sampled since changes in irrigation practices have occurred (due to the 2003 QSA). Groundwater selenium concentrations are variable; some wells south of the Salton Sea have selenium concentrations as high as 300 micrograms per liter (µg/L), whereas selenium concentrations are below detection in other wells. Groundwater and surface-water geothermal discharge zones around the margins of the Salton Sea and in unmanaged wetlands have not been studied in detail, and published selenium measurements are not available for these surface features. Selenium concentrations in the sediment of the Salton Sea drainage basin are highest in wetland particulate organic matter and the Salton Sea lakebed, indicating that removal of selenium from the water to the sediment has been a primary mechanism for keeping selenium concentrations low in the water column. Sediment selenium concentrations in wetlands are lower than in the Salton Sea but higher than inflowing drains and rivers, indicating the lentic wetland sites also may be important sinks for selenium because of biogeochemical processes. Sediment selenium data have not been collected in agricultural drains since changes in irrigation practices occurred (due to the 2003 QSA), and it is unknown if selenium sequestration from the water column has changed in these systems. We divided biological data into broad taxonomic categories, including primary producers, invertebrates, herpetofauna, mammals, fishes, and birds to facilitate evaluation of selenium concentrations and spatiotemporal trends observed in the Salton Sea. Overall, selenium concentrations were substantially greater in algae samples compared to all vascular plant samples combined. Median selenium concentrations in several invertebrate taxa (Chironomidae, Formicidae, Corixidae, Corbiculidae and Nereididae, and Decapoda) exceeded the maximum suggested dietary threshold of 3.0–4.0 micrograms per gram (µg/g) dry weight (dw) for predators consuming invertebrates in aquatic food webs. The greatest number of samples were collected from fish, and selenium distributions among species and locations showed that the range for most samples was lower than the U.S. Environmental Protection Agency selenium criterion for aquatic life (8.5 µg/g dw whole body, 11.3 µg/g dw fillets). The median selenium concentrations for whole body fish were below the selenium criterion in most locations, except for bairdiella ( Bairdiella icistia ) from the Salton Sea and irrigation drains, a few individual tilapia spp. (family Cichlidae, including genera Tilapia, Oreochromis , and their hybrids) from the river and river outlets, and several western mosquitofish ( Gambusia affinis ) and sailfin molly ( Poecilia latipinna ) from irrigation drain outlets. For avian samples combined among years and locations, median selenium concentrations in livers from all families except waders and Ibis (family Threskiornithidae) were higher than levels expected to cause selenium toxicosis (10–20 µg/g dw), and all median egg concentrations were above or near 6.0 μg/g dw, which is a conservative threshold value for reproductive impairment. Most knowledge gaps we identified for water, sediment, and biota were interrelated, and the use of integrated approaches to address knowledge gaps can provide greater insight into the drivers behind selenium hazards. Integrated water, sediment, and biota studies could help identify cost-effective management solutions that serve multiple purposes. A comprehensive analysis of the hydrology, biogeochemistry, and food-web processes in wetlands and other habitats can inform predictive models to identify drivers of selenium bioavailability, uptake from the environment and subsequent trophic transfer, ultimately forming the basis for experimental habitat management manipulations to minimize selenium hazards to wildlife. Furthermore, a comprehensive, long-term sampling and analytical laboratory plan would enable comparison of data among different entities that are sampling at the Salton Sea. Such efforts are well suited to help fill knowledge gaps that preclude understanding of selenium hazards and future management options for biota using Salton Sea habitats, including newly formed wetlands throughout the region. All data compiled for this report are available in two U.S. Geological Survey data releases: Groover and others (2022) for water and sediment samples and De La Cruz and others (2022) for biological samples. The data releases include all publicly available data for selenium concentrations in water, sediment, and biological samples collected in and around the Salton Sea, including the Coachella and Imperial Valleys. The data releases also include previously unpublished data.

California↗

USGS2002

Water quality and aquatic communities of upland wetlands, Cumberland Island National Seashore, Georgia, April 1999 to July 2000

Cumberland Island is the southernmost and largest barrier island along the coast of Georgia. The island contains about 2,500 acres of freshwater wetlands that are located in a variety of physical settings, have a wide range of hydroperiods, and are influenced to varying degrees by surface and ground water, rainwater, and seawater. In 1999-2000, the U.S. Geological Survey, in cooperation with the National Park Service, conducted a water-quality study of Cumberland Island National Seashore to document and interpret the quality of a representative subset of surface- and ground-water resources for management of the seashore's natural resources. As part of this study, historical ground-water, surface-water, and ecological studies conducted on Cumberland Island also were summarized. Surface-water samples from six wetland areas located in the upland area of Cumberland Island were collected quarterly from April 1999 to March 2000 and analyzed for major ions, nutrients, trace elements, and field water-quality constituents including specific conductance, pH, temperature, dissolved oxygen, alkalinity, tannin and lignin, and turbidity. In addition, water temperature and specific conductance were recorded continuously from two wetland areas located near the mean high-tide mark on the Atlantic Ocean beaches from April 1999 to July 2000. Fish and invertebrate communities from six wetlands were sampled during April and December 1999. The microbial quality of the near-shore Atlantic Ocean was assessed in seawater samples collected for 5 consecutive days in April 1999 at five beaches near campgrounds where most recreational water contact occurs. Ground-water samples were collected from the Upper Floridan aquifer in April 1999 and from the surficial aquifer in April 2000 at 11 permanent wells and 4 temporary wells (drive points), and were analyzed for major ions, nutrients, trace elements, and field water-quality constituents (conductivity, pH, temperature, dissolved oxygen, and alkalinity). Fecal-coliform bacteria concentrations were measured, but not detected, in samples collected from two domestic water-supply wells. During the 12-month period from April 1999 to March 2000 when water-quality and aquatic-community samples were collected, rainfall was 12.93 inches below the 30-year average rainfall. Constituent concentrations were highly variable among the different wetlands during the study period. Rainfall and tidal surges associated with tropical storms and hurricanes substantially influenced water quantity and quality, particularly in wetland areas directly influenced by tidal surges. Although surface waters on Cumberland Island are not used as sources of drinking water, exceedances of U.S. Environmental Protection Agency primary and secondary standards for drinking water were noted for comparative purposes. A nitrate concentration of 12 milligrams per liter in one sample from Whitney outflow was the only exceedance of a maximum contaminant level. Secondary standards were exceeded in 26 surface-water samples for the following constituents: pH (10 exceedances), chloride (8), sulfate (5), total dissolved solids (4), iron (2), fluoride (1), and manganese (1). The total-dissolved-solids concentrations and the relative abundance of major ions in surface-water samples collected from wetlands on Cumberland Island provide some insight into potential sources of water and influences on water quality. Major-ion chemistries of water samples from Whitney Lake, Willow Pond, and South End Pond 3 were sodium-chloride dominated, indicating direct influence from rainwater, salt aerosol, or inundation of marine waters. The remaining wetlands sampled had low total-dissolved-solids concentrations and mixed major-ion chemistries--North Cut Pond 2A was magnesium-sodium-chloride-sulfate dominated and Lake Retta and the two beach outflows were sodium-calcium-bicarbonate-chloride dominated. The higher percent calcium and bicarbonate in some wetlands sugg

Georgia↗

USGS2002

Water-quality and ground-water hydrology of the Columbia/Eagle Bluffs Wetland Complex, Columbia, Missouri— 1992-99

In an effort to restore riverine wetlands along the Missouri River, the Missouri Department of Conservation constructed the 2,700-acre Eagle Bluffs Conservation Area. The primary water source for managing 1,200 wetland acres on the Eagle Bluffs Conservation Area is treated effluent received from a 91-acre constructed wastewater-treatment wetland operated by the city of Columbia, Missouri. The combined areas of the Eagle Bluffs Conservation Area and the wastewater-treatment wetland are termed the Columbia/Eagle Bluffs Wetland Complex. The U.S. Geological Survey, in cooperation with the Missouri Department of Conservation and the city of Columbia, Missouri, collected samples quarterly from August 1992 to March 1999 from a monitoring network that included 33 ground-water sites and 4 surface-water sites to establish a baseline pre-effluent data set and to provide post-effluent data for trend analysis. Changes in major chemical constituent concentrations have been observed at several sampling locations between pre- and post-effluent data. Analysis of post-effluent time-series water-quality data indicates changes occurred in sodium, potassium, calcium, sulfate, and chloride concentrations at 13 sites. These changes can be correlated to the beginning of the operation of the wastewater-treatment wetland. The concentrations of these major chemical constituents plot on the mixing continuum between pre-effluent ground water as one end member and the treated effluent as the other end member. At ground water sites that had changes in concentrations, the relative percentage of treated effluent in the ground water, assuming chloride is conservative, ranged from 11 to more than 100 percent. At ground-water sites, few changes were noted in fecal indicator bacteria, nutrients, trace constituents, total and dissolved organic carbon, and organic constituents. Other than changes in boron concentrations at one ground-water site, these changes could not be directly correlated to the operation of the treatment wetland or the management of the Eagle Bluffs Conservation Area. After the treatment wetland began operation, improvement in the water quality in Perche Creek was observed. With respect to fecal indicator bacteria and nutrient concentrations, the water quality of water discharging from the Eagle Bluffs Conservation Area was improved relative to the water entering the area. Persistent ground-water highs have been observed beneath the Eagle Bluffs Conservation Area and wastewater-treatment unit 1 following the flooding of the wetland areas. These ground-water highs occur during the fall and winter months when ground- and surface-water levels are high and during the spring and summer months when the water levels are lower. The Missouri River stage had a strong effect on the water levels in the aquifer during pre-effluent conditions, but the effect has been lessened by the ground-water high.

Missouri↗

USGS2000

Characterization of rainfall-runoff response and estimation of the effect of wetland restoration on runoff, Heron Lake Basin, southwestern Minnesota, 1991-97

The U.S. Geological Survey (USGS), in cooperation with the Minnesota Department of Natural Resources and the Heron Lake Watershed District, conducted a study to characterize the rainfall-runoff response and to examine the effects of wetland restoration on the rainfall-runoff response within the Heron Lake Basin in southwestern Minnesota. About 93 percent of the land cover in the Heron Lake Basin consists of agricultural lands, consisting almost entirely of row crops, with less than one percent consisting of wetlands. The Hydrological Simulation Program – Fortran (HSPF), Version 10, was calibrated to continuous discharge data and used to characterize rainfall-runoff responses in the Heron Lake Basin between May 1991 and August 1997. Simulation of the Heron Lake Basin was done as a two-step process: (1) simulations of five small subbasins using data from August 1995 through August 1997, and (2) simulations of the two large basins, Jack and Okabena Creek Basins, using data from May 1991 through September 1996. Simulations of the five small subbasins was done to determine basin parameters for the land segments and assess rainfall-runoff response variability in the basin. Simulations of the two larger basins were done to verify the basin parameters and assess rainfall-runoff responses over a larger area and for a longer time period. Best-fit calibrations of the five subbasin simulations indicate that the rainfall-runoff response is uniform throughout the Heron Lake Basin, and 48 percent of the total rainfall for storms becomes direct (surface and interflow) runoff. Rainfall-runoff response variations result from variations in the distribution, intensity, timing, and duration of rainfall; soil moisture; evapotranspiration rates; and the presence of lakes in the basin. In the spring, the amount and distribution of rainfall tends to govern the runoff response. High evapotranspiration rates in the summer result in a depletion of moisture from the soils, substantially affecting the rainfall-runoff relation. Five wetland restoration simulations were run for each of five subbasins using data from August 1995 through August 1997, and for the two larger basins, Jack and Okabena Creek Basins, using data from May 1991 through September 1996. Results from linear regression analysis of total simulated direct runoff and total rainfall data for simulated storms in the wetland-restoration simulations indicate that the portion of total rainfall that becomes runoff will be reduced by 46 percent if 45 percent of current cropland is converted to wetland. The addition of wetlands reduced peak runoff in most of the simulations, but the reduction varied with antecedent soil moisture, the magnitude of the peak flow, and the presence of current wetlands and lakes. Reductions in the simulated total and peak runoff from the Jack Creek Basin for most of the simulated storms were greatest when additional wetlands were simulated in the North Branch Jack Creek or the Upper Jack Creek Subbasins. In the Okabena Creek Basin, reductions in simulated peak runoff for most of the storms were greatest when additional wetlands were simulated in the Lower Okabena Creek Subbasin.

Minnesota↗

USGS1978

Hydrology of the Nevin Wetland near Madison, Wisconsin

The 120-acre Nevin wetland at the south edge of Madison, Wis., is a discharge area of the local ground-water system. A hydrologic unit composed of drift and the upper part of an underlying sandstone sequence provides ground-water inflow. Ground water enters as springflow and as leakage upward through the organic wetland soils. The average annual water budget for the wetland was based on the 3 years 1974 through 1976. Although 1976 and 1975 were years of more than average precipitation, and 1976 was a year of less than average precipitation, the 3-year average precipitation was only slightly less than the long-term average. Inflow was composed of direct precipitation (7 percent), surfacewater inflow from the adjacent uplands (h percent), and ground-water inflow (89 percent). Ground-water inflow included springflow, upward leakage, and flow from artesian wells used in the Nevin State Fish Hatchery and discharged as effluent. Outflow was composed of streamflow (92 percent) and evapotranspiration (8 percent). The amount of water stored in the organic soils varied by only 1 inch during the study. Some ground water flowed beneath the wetland but did not discharge within the study area. Nutrients were contained in ground-water inflow, surface-water inflow, and precipitation. Ninety-five percent of the nitrogen that entered the wetland (1974 through 1976) entered in ground-water inflow, which included the hatchery discharge. Two percent was from precipitation, and 3 percent entered in surface-water inflow. Sixty-six percent of the phosphorus input was from ground water, 31 percent from surface water, and 3 percent from precipitation. Some nutrients were retained because only 79 percent as much nitrogen and 93 percent as much phosphorus left the wetland in streamflow as entered it. Sediment was also retained. Only 20 percent as much sediment (1974 through 1976) left the wetland in streamflow as entered it. Sediment was deposited where surface-water inflow from upland areas flowed onto the wetland surface and along stream channels. Inflows and outflows are quantified, and nutrient and sediment sources are identified, with the result that the effect of proposed land-use changes in the basin can be evaluated. Land-use practices that affect the wetland include drainage, urbanization, and water-supply development. Additional ground-water supplies can be obtained in the basin, but springflow and upward leakage of ground water through the organic soils will decrease.

Wisconsin↗

USGS1989

Effects of highway runoff on the quality of water and bed sediments of two wetlands in central Florida

Results of a study of the effects of highway runoff on the chemical quality of water and bed sediments of a cypress wetlands and a freshwater marsh in central Florida indicate that detention of the runoff prior to release into the wetland reduces concentrations of automobile-related chemicals in the water and bed sediments in the wetland. Detention of highway runoff for the cypress wetland occurs in a 68-ft by 139-ft detention pond, and in a 12-ft by 25 ft trash retainer for the freshwater marsh. The analysis of the chemical data for water and bed sediments indicates that many of the observed differences in chemistry are due to the difference in detention facilities. Water quality generally improved from the inlet to the outlet of both wetlands. Only inlet and outlet data were collected at the cypress wetland, and these showed a reduction in concentrations through the wetland. Spatial data collected at the freshwater marsh indicated that constituent concentrations in water generally decreased with distance from the inlet. Results of analysis of variance of grouped data for 40 water quality variables at the freshwater marsh inferred that 26 of the 40 variables tested were significantly different among five general locations within the wetland: inlet, outlet, near, intermediate, and far sites (with respect to the inlet). Results from this study indicate that detention structures, larger than the trash retainer at the freshwater marsh, may cause sufficient sorption and settling of substances contained in highway runoff to minimize the transport and deposition of some undesirable chemicals into wetlands. (USGS)

Water-Resources Investigations Report↗

USGS1996

The effects of flow-path modification on water-quality constituent retention in an urban stormwater detention pond and wetland system, Orlando, Florida

Changes in constituent retention in a wet stormwater-detention pond and wetland system in Orlando, Florida, were evaluated following the 1988 installation of a flow barrier which approximately doubled the flow path and increased detention time in the pond. The pond and wetland were arranged in series so that stormwater first enters the pond and overflows into the wetland before spilling over to the regional stream system. Several principal factors that contribute to constituent retention were examined, including changes in pond-water quality between storms, stormwater quality, and pond-water flushing during storms. A simple, analytical pond-water mixing model was used as the basis for interpreting changes in retention efficiencies caused by pond modification. Retention efficiencies were calculated by a modified event-mean concentration efficiency method using a minimum variance unbiased estimator approach. The results of this study generally support the hypothesis that changes in the geometry of stormwater treatment systems can significantly affect the constituent retention efficiency of the pond and wetland system. However, the results also indicate that these changes in efficiency are caused not only by changes in residence time, but also by changes in stormwater mixing and pond water flushing during storms. Additionally, the use of average efficiencies as indications of treatment effectiveness may fail to account for biases associated with sample distribution and independent physical properties of the system, such as the range and concentrations of constituents in stormwater inflows and stormwater volume. Changes in retention efficiencies varied among chemical constituents and were significantly different in the pond and wetland. Retention efficiency was related to inflow concentration for most constituents. Increased flushing of the pond after modification caused decreases in retention efficiencies for constituents that concentrate in the pond between storms (dissolved solids) and increases in retention efficiency for constituents that settle out of pond and wetland storage between storms. The greatest increase in retention efficiencies in the detention pond was observed for total lead, which increased from 19 percent before modification to 73 percent after modification. However, retention efficiencies for nutrients for nutrients and suspended constituents decreased in the wetland after modification. This was probably because of the flushing of accumulated sediments as a result of a change in flow path through the wetland. As a result, the overall effect of modification on the system (pond and wetland retention efficiencies combined) was a reduction in retention efficiency for all but two constituents (total zinc and total ammonia nitrogen).

Water-Resources Investigations Report↗

USGS2018

Site-scale disturbance best predicts moss, vascular plant, and amphibian indices in Ohio wetlands

Loss of wetland habitats and their associated biological communities is a major environmental concern. Quality assessment indices (QAIs) and indices of biological integrity (IBIs) are useful for assessing the responses of taxa to wetland habitat quality and land use in the surrounding landscape. We synthesized the results of our previous predictive modeling studies of five IBIs and QAIs for communities of mosses, vascular plants, and amphibians in forested and emergent wetlands in Ohio (USA). Overall, the single best predictor of these indices was a metric that estimated site-scale (i.e., within the wetland boundaries) substrate and habitat development, alteration, and disturbance. The second most important predictor was a metric that assessed site-scale wetland plant community types and quality, degree of interspersion, and microtopography. Landscape-scale variables better predicted moss and amphibian indices than either vascular plant index. Our results indicate that applying management practices that reduce the effects of site-scale anthropogenic disturbances and increase habitat complexity, such as creating forested buffers surrounding wetlands, increasing wetland contiguity, and creating hummocks and tussocks may simultaneously enhance amphibian, vascular plant, and moss communities in forested and emergent wetlands. Such a focused strategy may enable management agencies to more effectively apportion resources for wetland restoration and construction projects.

Ecological Restoration↗

USGS2023

A prioritization protocol for coastal wetland restoration on Molokaʻi, Hawaiʻi

Hawaiian coastal wetlands provide important habitat for federally endangered waterbirds and socio-cultural resources for Native Hawaiians. Currently, Hawaiian coastal wetlands are degraded by development, sedimentation, and invasive species and, thus, require restoration. Little is known about their original structure and function due to the large-scale alteration of the lowland landscape since European contact. Here, we used 1) rapid field assessments of hydrology, vegetation, soils, and birds, 2) a comprehensive analysis of endangered bird habitat value, 3) site spatial characteristics, 4) sea-level rise projections for 2050 and 2100 and wetland migration potential, and 5) preferences of the Native Hawaiian community in a GIS site suitability analysis to prioritize restoration of coastal wetlands on the island of Molokaʻi. The site suitability analysis is the first, to our knowledge, to incorporate community preferences, habitat criteria for endangered waterbirds, and sea-level rise into prioritizing wetland sites for restoration. The rapid assessments showed that groundwater is a ubiquitous water source for coastal wetlands. A groundwater-fed, freshwater herbaceous peatland or “coastal fen” not previously described in Hawaiʻi was found adjacent to the coastline at a site being used to grow taro, a staple crop for Native Hawaiians. In traditional ecological knowledge, such a groundwater-fed, agro-ecological system is referred to as a loʻipūnāwai (spring pond). Overall, 39 plant species were found at the 12 sites; 26 of these were wetland species and 11 were native. Soil texture in the wetlands ranged from loamy sands to silt and silty clays and the mean % organic carbon content was 10.93% ± 12.24 (sd). In total, 79 federally endangered waterbirds, 13 Hawaiian coots (‘alae keʻokeʻo; Fulica alai ) and 66 Hawaiian stilts (aeʻo; Himantopus mexicanus knudseni ), were counted during the rapid field assessments. The site suitability analysis consistently ranked three sites the highest, Kaupapaloʻi o Kaʻamola, Kakahaiʻa National Wildlife Refuge, and ʻŌhiʻapilo Pond, under three different weighting approaches. Site prioritization represents both an actionable plan for coastal wetland restoration and an alternative protocol for restoration decision-making in places such as Hawaiʻi where no pristine “reference” sites exist for comparison.

Hawaii↗

USGS2015

The challenges of remote monitoring of wetlands

Wetlands are highly productive and support a wide variety of ecosystem goods and services. Various forms of global change impose compelling needs for timely and reliable information on the status of wetlands worldwide, but several characteristics of wetlands make them challenging to monitor remotely: they lack a single, unifying land-cover feature; they tend to be highly dynamic and their energy signatures are constantly changing; and steep environmental gradients in and around wetlands produce narrow ecotones that often are below the resolving capacity of remote sensors. These challenges and needs set the context for a special issue focused on wetland remote sensing. Contributed papers responded to one of three overarching questions aimed at improving remote, large-area monitoring of wetlands: (1) What approaches and data products are being developed specifically to support regional to global long-term monitoring of wetland landscapes? (2) What are the promising new technologies and sensor/multisensor approaches for more accurate and consistent detection of wetlands? (3) Are there studies that demonstrate how remote long-term monitoring of wetland landscapes can reveal changes that correspond with changes in land cover and land use and/or changes in climate?

Remote Sensing↗

USGS2024

Influence of four veterinary antibiotics on constructed treatment wetland nitrogen transformation

The use of wetlands as a treatment approach for nitrogen in runoff is a common practice in agroecosystems. However, nitrate is not the sole constituent present in agricultural runoff and other biologically active contaminants have the potential to affect nitrate removal efficiency. In this study, the impacts of the combined effects of four common veterinary antibiotics (chlortetracycline, sulfamethazine, lincomycin, monensin) on nitrate-N treatment efficiency in saturated sediments and wetlands were evaluated in a coupled microcosm/mesocosm scale experiment. Veterinary antibiotics were hypothesized to significantly impact nitrogen speciation (e.g., nitrate and ammonium) and nitrogen uptake and transformation processes (e.g., plant uptake and denitrification) within the wetland ecosystems. To test this hypothesis, the coupled study had three objectives: 1. assess veterinary antibiotic impact on nitrogen cycle processes in wetland sediments using microcosm incubations, 2. measure nitrate-N reduction in water of floating treatment wetland systems over time following the introduction of veterinary antibiotic residues, and 3. identify the fate of veterinary antibiotics in floating treatment wetlands using mesocosms. Microcosms containing added mixtures of the veterinary antibiotics had little to no effect at lower concentrations but stimulated denitrification potential rates at higher concentrations. Based on observed changes in the nitrogen loss in the microcosm experiments, floating treatment wetland mesocosms were enriched with 1000 μg L −1 of the antibiotic mixture. Rates of nitrate-N loss observed in mesocosms with the veterinary antibiotic enrichment were consistent with the microcosm experiments in that denitrification was not inhibited, even at the high dosage. In the mesocosm experiments, average nitrate-N removal rates were not found to be impacted by the veterinary antibiotics. Further, veterinary antibiotics were primarily found in the roots of the floating treatment wetland biomass, accumulating approximately 190 mg m −2 of the antibiotic mixture. These findings provide new insight into the impact that veterinary antibiotic mixtures may have on nutrient management strategies for large-scale agricultural operations and the potential for veterinary antibiotic removal in these wetlands.

Toxics↗

USGS2019

Wetland biomass and productivity in Coastal Louisiana: Base line data (1976-2015) and knowledge gaps for the development of spatially explicit models for ecosystem restoration and rehabilitation initiatives

Coastal Louisiana host 37% of the coastal wetland area in the conterminous US, including one of the deltaic coastal regions more susceptible to the synergy of human and natural impacts causing wetland loss. As a result of the construction of flood protection infrastructure, dredging of channels across wetlands for oil/gas exploration and maritime transport activities, coastal Coastal Louisiana hosts 37% of the coastal wetland area in the conterminous US, including one of the deltaic coastal regions more susceptible to the synergy of human and natural impacts causing wetland loss. As a result of the construction of flood protection infrastructure, dredging of channels across wetlands for oil/gas exploration and maritime transport activities, coastal Louisiana has lost approximately 4900 km2 of wetland area since the early 1930s. Despite the economic relevance of both wetland biomass and net primary productivity (NPP) as ecosystem services, there is a lack of vegetation simulation models to forecast the trends of those functional attributes at the landscape level as hydrological restoration projects are implemented. Here, we review the availability of peer-reviewed biomass and NPP wetland data (below and aboveground) published during the period 1976–2015 for use in the development, calibration and validation of high spatial resolution (<200 m × 200 m) vegetation process-based ecological models. We discuss and list the knowledge gaps for those species that represent vegetation community associations of ecological importance, including the long-term research issues associated to limited number of paired belowground biomass and productivity studies across hydrological basins currently undergoing different freshwater diversions management regimes and hydrological restoration priorities.

Louisiana↗

USGS2025

Wetland ecohydrology

Ecohydrology emphasizes the interactions between ecological and hydrological patterns and processes in wetlands. Given that wetlands are fundamentally defined by prolonged saturation or flooding of land, an ecohydrological perspective is implicit in wetland ecology. In this review, we provide examples of how variation in hydrologic processes in space and time influences wetland ecosystems in temperate riparian zones, inland temperate wetlands, and subtropical monsoonal wetlands. Because wetland ecosystems are highly impacted by anthropogenic change, an understanding of ecohydrological processes in wetlands will be critical for future conservation and restoration of wetlands in a changing world.

Book chapter↗