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USGS2004

The Blackwater NWR inundation model. Rising sea level on a low-lying coast: land use planning for wetlands

The Blackwater National Wildlife Refuge (BNWR), on the Eastern Shore of Chesapeake Bay (figure 1), occupies an area less than 1 meter above sea level. The Refuge has been featured prominently in studies of the impact of sea level rise on coastal wetlands. Most notably, the refuge has been sited by the Intergovernmental Panel on Climate Change (IPCC) as a key example of 'wetland loss' attributable to rising sea level due to global temperature increase. Comparative studies of aerial photos taken since 1938 show an expanding area of open water in the central area of the refuge. The expanding area of open water can be shown to parallel the record of sea level rise over the past 60 years. The U.S. Fish and Wildlife Service (FWS) manages the refuge to support migratory waterfowl and to preserve endangered upland species. High marsh vegetation is critical to FWS waterfowl management strategies. A broad area once occupied by high marsh has decreased with rising sea level. The FWS needs a planning tool to help predict current and future areas of high marsh available for waterfowl. 'Wetland loss' is a relative term. It is dependant on the boundaries chosen for measurement. Wetland vegetation, zoned by elevation and salinity (figure 3), respond to rising sea level. Wetlands migrate inland and upslope and may vary in areas depending on the adjacent land slopes. Refuge managers need a geospatial tool that allows them to predict future areas that will be converted to high and intertidal marsh. Shifts in location and area of coverage must be anticipated. Viability of a current marsh area is also important. When will sea level rise make short-term management strategies to maintain an area impractical? The USGS has developed an inundation model for the BNWR centered on the refuge and surrounding areas. Such models are simple in concept, but they require a detailed topographic map upon which to superimpose future sea level positions. The new system of LIDAR mapping of land and shallow water surfaces has solved this problem. Our team has developed a detailed LIDAR map of the BNWR area at a 30 centimeter (ca. 1 ft) contour interval (figure 2). The new map allows us to identify the present marsh vegetation zones and to predict the location and area of future zones on a decade-by- decade basis over the next century at increments of sea level rise on the order of 3 cm/decade (ca. 1 inch). We have developed two scenarios for the model. The first is a steady-state model that uses the historic rate of sea level rise of 3.1 mm/yr to predict marsh areas. The second is a 'global warming' scenario utilizing a conservative IPCC model with an exponentially-increasing rate of sea level rise. Under either scenario, the BNWR is progressively inundated with an expanding core of open water. Although their positions change in the future, the areas of intertidal marsh as well as those of the critical high marsh remain fairly constant until the year 2050. Beyond that time, the low-lying land surface is overtopped by rising sea level and the area is dominated by open water. Our model suggests that wetland habitat in the Blackwater area might be maintained and sustained through a combination of public and private preservation efforts through easements in combination with judicious Federal land acquisition into the predicted areas of suitable marsh formation - but for only the next 50 years. Beyond that time much of this area will become open water.

Open-File Report↗

USGS2007

Finding the Exotic Faucet Snail (Bithynia tentaculata): Investigation of Waterbird Die-Offs on the Upper Mississippi River National Wildlife and Fish Refuge

Beginning in 2002, there have been major waterbird die-offs every spring and fall in Lake Onalaska (Navigation Pool 7 of the Upper Mississippi River) located near La Crosse, Wisconsin. This area is part of the Upper Mississippi River National Wildlife and Fish Refuge (UMR Refuge) and lies within the Mississippi Flyway, through which an estimated 40 percent of the continent's waterfowl migrate. Through the 2006 spring migration, total mortality on the UMR Refuge was estimated at 22,000 to 26,000 birds, primarily American coots (Fulica americana) and lesser scaup (Aythya affinis). Two trematodes (Sphaeridiotrema globulus and Cyathocotyle bushiensis) that use the exotic faucet snail (Bithynia tentaculata) as an intermediate host were found to infect and kill the waterbirds. The faucet snail was introduced into the United States from Europe in the late 1800s. Because Lake Onalaska is a major spring and fall stop-over area for waterfowl in the Mississippi Flyway, concerns were raised that the snail and trematodes may be spreading to other waterfowl stop-over areas on the river. Exploratory sampling for faucet snails was conducted in 2005 and 2006 in navigation Pools 4-9 (excluding Pool 5a which is located between Pools 5 and 6), 11, and 13. Infected snails were found in all the sampled pools except Pool 6. To our knowledge, these are the first records of faucet snails and associated trematodes beyond those found in Pool 7, Lake Onalaska. Waterbird die-offs are becoming a UMR Refuge-wide problem. Information obtained through research and monitoring, including the identification of the origin of infections in snails and birds and the role various environmental factors have on this process, should help guide managers to develop effective mitigation and control measures.

Open-File Report↗

USGS1968

Ground-water exploration in the Bosque del Apache Grant, Socorro County, New Mexico

Test drilling along the Rio Grande in the Bosque del Apache Grant in Socorro County, New Mexico has shown that the area is hydrologically complex and that the quality of the ground water varies from saline to fresh within short distances both laterally and vertically. Nearly all of the riverside land in the Grant is occupied by the migratory waterfowl refuge of the Bosque del Apache National Wildlife Refuge. Potable and near-potable water is obtained from 12 wells in this area that tap sand and gravel, and the wells are capable of yielding 1,000 gallons per minute or more. Stallion Range Center, a military installation on the White Sands Missile Range, about 15 miles east of =he waterfowl refuge, needs about 100,000 gallons per day of potable water. Potable water in large quantities is not known to be available at a location closer to the Center than the refuge area. The Fish and Wildlife Service, which operates the waterfowl refuge, gave permission to White Sands Missile Range to test drill and to develop a supply well in certain areas along the Rio Grande outside the managed lands of the refuge. The U.S. Geological Survey was then asked by White Sands Missile Range to choose locations for test drilling and to monitor drilling and testing of the wells. Between 1963 and 1967 test wells were drilled and a suitable location for a supply well as found. The well would be about 250 feet deep and would tap a body of potable water that is about 100 feet in thickness and is thought to underlie an area of at least 5 square miles. This report contains diagrammatic sections that show the lateral and vertical relation of waters of different quality along the Rio Grande in a part of the Bosque del Apache Grant. Basic data are given in tables; they include records of 7 test wells and 12 high-yield supply wells, and 52 chemical analyses of ground water from the wells.

Open-File Report↗

USGS2011

Vegetation of Lacassine National Wildlife Refuge, Louisiana-Recent plant communities with comparison to a three-decade-old survey

Shifts in plant community composition and structure can affect the quality of habitat for wildlife species. Lacassine National Wildlife Refuge in southwestern Louisiana was established in 1937 with a primary goal of providing habitat for wintering waterfowl species. A large freshwater impoundment constructed on the refuge to improve waterfowl habitat value was completed in 1943. About 10 years after construction was completed, staff at the refuge became concerned that emergent vegetation cover was increasing in the impoundment over time while open water areas, which are critical as foraging and resting areas for waterfowl, were decreasing. To document vegetation change over time, we collected information on plant community species composition for comparison to similar data collected in 1973. A total of 84 sampling plots was established in 2006 within the impoundment to coincide as closely as possible to plots sampled in the earlier study. Plant species composition and cover were recorded at each plot in the summers of 2006 and 2007. Change between sampling events separated by more than three decades was determined by comparing the frequency of occurrence of 20 species identified in 1973 to their frequency in 2006 and 2007. Interannual variation was determined by comparing plot data between 2006 and 2007. In plots dominated by emergent vegetation, it was found that Bacopa caroliniana, Eleocharis equisetoides, Leersia hexandra, Panicum hemitomon, and Sagittaria lancifolia were significantly less frequent in 2006 and 2007 than in 1973. The frequency of Brasenia schreberi, Cabomba caroliniana, Nitella gracilis, and Nymphoides aquatica was significantly lower in 2006 and 2007 than in 1973 in plots dominated by floating-leaved plants, submersed plants, or open water. In 2007, Hydrocotyle sp. and Sacciolepis striata were more frequent than in 1973 in emergent vegetation plots, and Utricularia sp. was more frequent in submersed or open-water plots. We documented interannual variation by an increase in species richness, the Shannon diversity index, and evenness of species distribution within plots in 2007 compared to 2006. The total cover by species did not differ between years, but the frequency of seven species was greater in 2007 compared to 2006 while the frequency of unvegetated surface was lower. Results indicated that the occurrence of some species varied between both 2006 and 2007 and 1973, but the lack of complete data from the 1973 study limits confidence in this conclusion. The interannual variation documented between 2006 and 2007 may be due to several factors, including a response to weather conditions or to recovery from the impacts of Hurricane Rita, which impacted Lacassine National Wildlife Refuge in the fall of 2005 and likely raised salinity levels in the impoundment. More information is needed to determine if the interannual variation identified in the plant communities of Lacassine National Wildlife Refuge between 2006 and 2007 was unusual or represents normal variation.

Scientific Investigations Report↗

USGS2012

Effects of a drawdown on plant communities in a freshwater impoundment at Lacassine National Wildlife Refuge, Louisiana

Disturbance is an important natural process in the creation and maintenance of wetlands. Water depth manipulation and prescribed fire are two types of disturbance commonly used by humans to influence vegetation succession and composition in wetlands with the intention of improving wildlife habitat value. A 6,475-hectare (ha) impoundment was constructed in 1943 on Lacassine National Wildlife Refuge in southwest Louisiana to create freshwater wetlands as wintering waterfowl habitat. Ten years after construction of the impoundment, called Lacassine pool, was completed, refuge staff began expressing concerns about increasing emergent vegetation cover, organic matter accumulation, and decreasing area of open water within the pool. Because the presence of permanent standing water impedes actions that can address these concerns, a small impoundment within the pool where it was possible to manipulate water depth was created. The 283-ha subimpoundment called Unit D was constructed in 1989. Water was pumped from Unit D in 1990, and the unit was permanently reflooded about 3 years later. Four prescribed fires were applied during the drawdown. A study was initiated in 1990 to investigate the effect of the experimental drawdown on vegetation and soils in Unit D. Four plant community types were described, and cores were collected to measure the depth of the soil organic layer. A second study of Unit D was conducted in 1997, 4 years after the unit was reflooded, by using the same plots and similar sampling methods. This report presents an analysis and synthesis of the data from the two studies and provides an evaluation of the impact of the management techniques applied. We found that plant community characteristics often differed among the four communities and varied with time. Species richness increased in two of the communities, and total aboveground biomass increased in all four during the drawdown. These changes, however, did not persist when Unit D was reflooded; by 1997, species richness and aboveground biomass were equivalent to values before the drawdown. The change in waterfowl food value of the plant communities during the drawdown varied; it did not change in two communities, increased in one, and decreased in one. A consistent pattern noted was that waterfowl food value was higher in communities that contained open water than in those dominated by emergent plants, both soon after the drawdown was initiated in Unit D and 4 years after reflooding. A reduction in depth of the soil organic layer became apparent 20 months after drawdown was initiated, and this reduction persisted in 1997, 4 years after reflooding. A separate 2003 study on soil characteristics in Lacassine pool found that the depth to the clay layer was lower in Unit D than in the rest of the pool. We were not able to establish a cause-and-effect relation between any changes noted and the fact water levels in the unit were drawn down because the initial study in 1990 did not include control plots. Changes in vegetation and soil organic layer depth identified in Unit D may have occurred in the surrounding Lacassine pool habitat as well. Similarly, we were unable to form any conclusions about the effect of the prescribed fire treatments because there was no information on which plots were burned. Because of the known relation between anaerobic soil conditions and reduced decomposition of organic matter, however, it is likely that the drawdown in Unit D resulted in an increased decomposition rate and a reduction in the depth of the soil organic layer.

Louisiana↗

USGS1990

Reconnaissance investigation of water quality, bottom sediment, and biota associated with irrigation drainage in the Salton Sea area, California, 1986-87

Water, bottom sediment, and biota were sampled during 1986 and 1987 in the Salton Sea area to determine concentrations of trace elements and pesticides as part of the Department of Interior Irrigation Drainage Program. The sampling sites (12 water, 15 bottom sediment, and 5 biota) were located in the Coachella and Imperial Valleys. The focus of sampling was to determine the current or potential threat to the wildlife of the Salton National Wildlife Refuge from irrigation projects sponsored or operated by the Department of the Interior. Results of the investigation indicate that selenium is the major element of concern. Elevated concentrations of selenium in water were restricted to tile-drain effluent. The maximum selenium concentration of 300 microg/L was detected in a tile-drain sample, and the minimum concentration of 1 microg/L was detected in a composite sample of Salton Sea water. The median selenium concentration was 19 microg/L. In contrast to the water, the highest bottom-sediment selenium concentration of 3.3 mg/kg was in a composite sample from the Salton Sea. The selenium detected in samples of waterfowl and fish also are of concern, but, to date, no studies have been done in the Salton Sea area to determine if selenium has caused adverse biological effects. Concentrations of boron and manganese were elevated in tile-drain samples throughout the Imperial Valley. Boron concentrations in migratory waterfowl were at levels that could cause reproduction impairment. Elevated concentrations of chromium, nickel, and zinc were detected in the Whitewater River , but they were not associated with irrigation drainage. Organochlorine pesticide residues were detected in bottom sediment throughout the study area at levels approaching those measured more than 10 years ago. More detailed studies would be needed to determine if these residues are affecting the waterfowl. (USGS)

Water-Resources Investigations Report↗

USGS2017

Could changes in the agricultural landscape of northeastern China have influenced the long-distance transmission of highly pathogenic avian influenza H5Nx viruses?

In the last few years, several reassortant subtypes of highly pathogenic avian influenza viruses (HPAI H5Nx) have emerged in East Asia. These new viruses, mostly of subtype H5N1, H5N2, H5N6, and H5N8 belonging to clade 2.3.4.4, have been found in several Asian countries and have caused outbreaks in poultry in China, South Korea, and Vietnam. HPAI H5Nx also have spread over considerable distances with the introduction of viruses belonging to the same 2.3.4.4 clade in the U.S. (2014–2015) and in Europe (2014–2015 and 2016–2017). In this paper, we examine the emergence and spread of these new viruses in Asia in relation to published datasets on HPAI H5Nx distribution, movement of migratory waterfowl, avian influenza risk models, and land-use change analyses. More specifically, we show that between 2000 and 2015, vast areas of northeast China have been newly planted with rice paddy fields (3.21 million ha in Heilongjiang, Jilin, and Liaoning) in areas connected to other parts of Asia through migratory pathways of wild waterfowl. We hypothesize that recent land use changes in northeast China have affected the spatial distribution of wild waterfowl, their stopover areas, and the wild-domestic interface, thereby altering transmission dynamics of avian influenza viruses across flyways. Detailed studies of the habitat use by wild migratory birds, of the extent of the wild–domestic interface, and of the circulation of avian influenza viruses in those new planted areas may help to shed more light on this hypothesis, and on the possible impact of those changes on the long-distance patterns of avian influenza transmission.

Frontiers in Veterinary Science↗

USGS2017

Body mass, wing length, and condition of wintering ducks relative to hematozoa infection

Waterfowl managers lack information regarding factors that may be reducing the positive response of waterfowl body condition to habitat improvements. Protozoan blood parasites (i.e., hematozoa) are commonly found in birds and have been related to reduced body mass, wing length, and body condition. We studied relationships between 12 measures of hematozoa infection and body mass, wing length, and body mass divided by wing length (i.e., body condition index [BCI]) of the five most common duck species (northern pintail [ Anas acuta ], mallard [ A. platyrhynchos ], green-winged teal [ A. crecca ], American wigeon [ A. Americana ], northern shoveler [ A. clypeata ]) wintering in the Central Valley of California during October 2006-January 2007. After accounting for variation due to species, age-sex cohort, Central Valley region, and month; wing length, body mass, and BCI were found to be negatively related to infection by Leucocytozoon and by "any hematozoa" but not related to infection by only Plasmodium or Haemoproteus , or coinfections of greater than one genera or parasite haplotype (albeit, few ducks had Plasmodium or Haemoproteus infection or coinfections). Evidence of a negative relationship with infection was stronger for body mass and BCI than for wing length and indicated that the relationships varied among species, age-sex cohorts, regions, and months. Compared to uninfected ducks, hematozoa-infected duck body mass, wing length, and BCI was -1.63% (85% CI = -2.79%- -0.47%), -0.12% (-0.41%- +0.17%), and -1.38% (-2.49%- -0.26%), respectively. Although, seemingly small, the -1.63% difference in body mass represents a large percentage (e.g., 38% for northern pintail) of the observed increase in wintering duck body mass associated with Central Valley habitat improvements. Because infection prevalence and relationship to body condition might change over time due to climate or other factors, tracking hematozoa infection prevalence might be important to inform and accurately assess the effect of conservation programs designed to improve waterfowl body condition.

California↗

USGS2012

Bird use of fields treated postharvest with two types of flooding in Tulare Basin, California

We surveyed birds on grain and non-grain fields in the Tulare Basin of California treated post-harvest with two types of flooding that varied in duration and depth of water applied (Flooded-type fields [FLD]: <1 cm-1.5 m for >1 week; Irrigated-type fields [IRG]: <1-15 cm water for <1 week at a time). Our goal was to compare use of these field types by birds to guide habitat conservation in the region. During 19 August-6 December 2005, we counted a total of 80,316 birds during 23 surveys of 5 FLD (4 wheat, 1 alfalfa) fields and 8,225 birds during 38 surveys of 33 IRG (23 cotton, 4 tomato, 3 wheat, 1 alfalfa, 1 oat, 1 fallow) fields. We recorded 14 waterfowl (13 duck, 1 goose), 29 other waterbird (coots, shorebirds, grebes, pelicans, herons, egrets, gulls, terns), and 14 non-waterbird (passerines, raptors, and vultures) species on FLD fields compared to 5 duck, 14 other waterbird, and 9 non-waterbird species on IRG fields. Species composition differed by field type; waterfowl (FLD vs. IRG, 16.2% vs. 1.3%) and other waterbirds (80.4% vs. 71.6%) comprised a greater percentage and non-waterbirds (3.5% vs. 27.1%) a lower percentage of birds on FLD than on IRG fields. The modeled density estimate of waterfowl was 108 times greater on FLD than IRG fields and 7.4 times greater on grain than non-grain fields. The density estimate of other waterbirds was 11.8 times greater on FLD than IRG fields and 4.4 times greater on grain than non-grain fields. The density estimate of non-waterbirds was 14.3 times greater on grain than non-grain fields but did not differ by flood type. Long duration (i.e., >1 week) flooding increased waterbird use of grain fields in the Tulare Basin more than in the northern Central Valley. Thus, even though water costs are high in the Tulare Basin, if net benefit to waterbirds is considered, management programs that increase availability of FLD-type fields (especially grain) in the Tulare Basin may be a cost-effective option to help meet waterbird habitat conservation goals in the Central Valley of California.

California↗

USGS2012

Relative value of managed wetlands and tidal marshlands for wintering northern pintails

Northern pintail Anas acuta (hereafter, pintail) populations have declined substantially throughout the western US since the 1970s, largely as a result of converting wetlands to cropland. Managed wetlands have been developed throughout the San Francisco Bay estuaries to provide wildlife habitat, particularly for waterfowl. Many of these areas were historically tidal baylands and plans are underway to remove dikes and restore tidal action. The relationship between tidal baylands and waterfowl populations is poorly understood. Our objective was to provide information on selection and avoidance of managed and tidal marshland by pintails. During 1991–1993 and 1998–2000, we radio-marked and relocated 330 female pintails (relocations, n =11,574) at Suisun Marsh, the largest brackish water estuary within San Francisco Bay, to estimate resource selection functions during the nonbreeding months (winter). Using a distance-based modeling approach, we calculated selection functions for different ecological communities (e.g., tidal baylands) and investigated variation explained by time of day (day or night hours) to account for differences in pintail behavior (i.e., foraging vs. roosting). We found strong evidence for selection of managed wetlands. Pintails also avoided tidal marshes and bays and channels. We did not detect differences in selection function between day and night hours for managed wetlands but the degree of avoidance of other habitats varied by time of day. We also found that areas subjected to tidal action did not influence the selection of immediately adjacent managed wetlands. If current management goals include providing habitat for wintering waterfowl populations, particularly pintail, then we recommend wildlife managers focus tidal restoration on areas that are not currently managed wetland and/or improve conditions in areas of managed wetlands to increase local carrying capacities

California↗

USGS2008

Biological and societal dimensions of lead poisoning in birds in the USA

The ingestion of spent lead shot was known to cause mortality in wild waterfowl in the US a century before the implementation of nontoxic shot regulations began in 1972. The biological foundation for this transition was strongly supported by both field observations and structured scientific investigations. Despite the overwhelming evidence, various societal factors forestalled the full transition to nontoxic shot for waterfowl hunting until 1991. Now, nearly 20 years later, these same factors weigh heavily in current debates about nontoxic shot requirements for hunting other game birds, requiring nontoxic bullets for big game hunting in California Condor range and for restricting the use of small lead sinkers and jig heads for sport-fishing. As with waterfowl, a strong science-based foundation is requisite for further transitions to nontoxic ammunition and fishing weights. Our experiences have taught us that the societal aspects of this transition are as important as the biological components and must be adequately addressed before alternatives to toxic lead ammunition, fishing weights, and other materials will be accepted as an investment in wildlife conservation.

Book chapter↗

USGS1984

Persistence of Pasteurella multocida in Nebraska wetlands under epizootic conditions

Gleason Basin, a marsh located in the western part of the Rainwater Basin in Nebraska, was selected during the 1980 spring waterfowl migration as a study site to determine the presence and persistence of virulent Pasteurella multocida . Avian cholera mortality in migratory waterfowl using the Basin increased during a 2-wk period of a die-off beginning the first week of March when 2,409 carcasses were collected from the marsh. Study sites within the marsh were established for sampling water associated with and not associated with intact and scavenged carcasses. Isolations of virulent P. multocida were made from five of six study sites associated with either intact or scavenged carcasses for 3 days and from three of five non-carcass-associated study sites for 2 days. Recovery of these bacteria from this environment suggested a possible source of infection for susceptible waterfowl using the contaminated site.

Nebraska↗

USGS1984

[Book review] The wildfowl of Britain and Europe

Of about 140 extant species of waterfowl in the world, 54 occur in the western Pale- arctic. In this, his most recent book, Ogilvie introduces the reader to the waterfowl of Europe including occasional visitors and introduced species. Although written primarily for laymen, ornithologists will find the book informative but should not expect a major treatise on European waterfowl. The text is drawn primarily from Volume I of "The hand-book of the birds of Europe, North Africa, and the Middle East: the birds of the Western Palearctic," of which the author was an editor.

The Auk↗

USGS1983

[Book review] Ducks, geese and swans of North America

This is the 3rd edition of the classic work "The Ducks, Geese and Swans of North America," which was first published in December 1942. The original edition was authored by Francis C. Kortright with color plates by T. M. Shortt. An authoritative reference on North American waterfowl for many years, the book had become outdated as a result of major advances in the field of waterfowl biology. The need to update the 1st edition culminated in the publication in 1976 of a 2nd edition authored by Frank Bellrose. Readers interested in comparing features of the 1976 edition with other major recent works on North American waterfowl by P. A. Johnsgard and R. S. Palmer should read Weller (1977, Auk 94: 173).

The Auk↗

USGS1988

The St. Clair River and Lake St. Clair, Michigan: an ecological profile

The St. Clair River and Lake St. Clair form a part of the connecting channel system between Lake Huron and Lake Erie. This report synthesizes existing information on the ecological structure and function of this ecosystem. Chapters include descriptions of climatology, hydrology, and geology of the region; biological characteristics; ecological relationships; and commercial and recreational uses, as well as discussions of management considerations and issues. The St. Clair system provides valuable habitat for migratory waterfowl and fish spawning and nurseries, and contains some of the most extensive emergent wetlands in the region. The system is used for navigation, municipal and industrial waste disposal, recreational boating, fishing and waterfowl hunting. Allowing for multiple human uses while maintaining important waterfowl and fish populations is the greatest challenge facing managers of this system.

Biological Report↗

USGS1988

The Detroit River, Michigan: an ecological profile

A part of the connecting channel system between Lake Huron and Lake Erie, the Detroit River forms an integral link between the two lakes for both humans and biological resources such as fish, nutrients, and plant detritus. This profile summarizes existing scientific information on the ecological structure and functioning of this ecosystem. Topics include the geological history of the region, climatic influences, river hydrology, lower trophic-level biotic components, native and introduced fishes, waterfowl use, ecological interrelationships, commercial and recreational uses of the river, and current management issues. Despite urbanization, the river still supports diverse fish, waterfowl, and benthic populations. Management issues include sewer overflows; maintenance dredging for navigation and port activities; industrial discharges of potentially hazardous materials; and wetland, fishery, and waterfowl protection and enhancement.

Biological Report↗

USGS1991

Wigeongrass ( Ruppia maritima ): a literature review

Wigeongrass (Ruppia maritima L.) is a submersed macrophyte of nearly cosmopolitan distribution and worldwide importance as a waterfowl food. Unfortunately, the plant no longer inhabits vast areas disturbed by human activities. Taxonomic status of the plant is uncertain, especially in North America. In mild climates, in habitats subject to environmental extremes, the plant behaves as an annual (vegetation perishes), or as a perennial in deeper, more stable habitats (some vegetative parts grow year round). Drupelets (seeds) provide a mechanism for wigeongrass to survive periods of drought and excessive water salinity. These sexual propagules can be washed ashore or carried by birds or fish for long distances.Wigeongrass mostly occurs in temporarily to permanently flooded mesohaline-hyperhaline estuarine wetlands, but it also occurs inland in fresh to hypersaline palustrine and lacustrine wetlands. Most populations inhabit warm, relatively unpolluted, and well lit waters <2.0 m deep where fetches and wave action are not great. The species is probably best adapted to stable water levels but can tolerate significant water level fluctuations, including periodic exposure in tidal areas. Robust growth occurs in areas of slow current. Wigeongrass is alone among the submersed North American angiosperms in tolerance to high salinity, but it is likely at a competitive disadvantage among specialist taxa in soft or acidic waters. The species grows in nearly all common bottom substrates, but growth is favored by aerobic and low H 2 S conditions. Turbidity frequently limits wigeongrass growth in waters overlying easily suspendible bottom substrates.Wigeongrass often occurs in monotypic stands, yet grows with many other submersed and emergent macrophytes. Dominance in certain wetlands sometimes alternates with dominance by other submersed macrophytes as salinities, seasonal temperature cycles, or other environmental factors change. The shading effect of metaphytic, planktonic, or epiphytic algae often reduces production.Wigeongrass and its detritus provide food and cover for a large invertebrate biota, although direct consumption of the living plants is minimal. Wigeongrass beds in coastal wetlands are heavily used by fish. The plant is recognized worldwide as an important food of migrant and wintering waterfowl, wading birds, and shorebirds. In subtropical climates, wintering waterfowl can quickly consume entire stands.Propagation and management of wigeongrass has occurred for nearly 60 years in the southern and eastern United States. During the seventies and eighties, sophisticated water level and salinity management techniques have been developed to encourage growth of the plant.Future research should concentrate on determining the means to reduce light-limiting turbidity in many wetland types; understanding the ways in which human activities on and near wetlands affect wigeongrass production; and developing reliable and predictable techniques to stimulate wigeongrass production by water level manipulations and other means in different environmental settings. Trophic interactions and the effects of biomanipulation of fish populations in managed wigeongrass habitat--now little understood--also require more study.

Fish and Wildlife Research↗

USGS1989

Prairie basin wetlands of the Dakotas: a community profile

This description of prairie basin wetlands of the Dakotas is part of a series of community profiles on ecologically important wetlands of national significance. The shallow wetlands of the Dakotas form the bulk of the portion of the Prairie Pothole Region lying within the United States. This region is famous as the producer of at least half of North America's waterfowl and an unknown, but large, proportion of other prairie-dwelling marsh and aquatic birds.The wetlands described here lie in relatively small, shallow basins that vary greatly in their ability to maintain surface water, and in their water chemistry, which varies from fresh to hypersaline. These wetlands occur in a wide variety of hydrological settings, in an area where annual and seasonal precipitation varies greatly in form and amount. Thus the presence of surface water in these wetlands is largely unpredictable. Superimposed on these phenomena are the effects of a variety of land uses, including pasture, cultivation, mechanical forage removal, idle conditions and burning. All those factors greatly affect the plant and animal communities found in these basins.This profile covers lacustrine and palustrine basins with temporarily flooded, seasonally flooded, and semipermanently flooded water regimes. Basins with these water regimes compose about 90% of the basins in the Prairie Pothole Region of the Dakotas. This profile outlines the wetland subsystems, classes and subclasses that occur in these basins, and provides a useful reference to their geologic, climatic, hydrologic, and pedologic setting.Detailed information on the biotic environment of the wetlands dealt with in this profile will be useful to scientists and resource managers. Special recognition is paid to the macrophyte and invertebrate communities, which have dynamic qualities found in few other of the world's wetland ecosystems.The most noteworthy animal inhabitants of these basins are waterfowl, which are a resource of international concern. Because of the importance of this resource, much research on the habitat use and feeding ecology of breeding waterfowl has been conducted in the region. These topics receive special attention in this profile.The Prairie Pothole Region is a major world supplier of cereal grains. Consequently, wetlands in the region are often drained for crop production or otherwise cropped when water conditions permit. These practices degrade the value of wetlands for most species of wildlife and conflict with the aims of conservationists. The subject of human uses and impacts to prairie wetlands is thus an important part of this profile.

Biological Report↗