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At least 217 records · Page 12Linked to original sources
USGS1982

Aquatic biology in Nederlo Creek, southwestern Wisconsin

This report presents the results of biologic investigations by the U.S. Geological Survey and the Wisconsin Department of Natural Resources during a study of hydrology and water quality in a small drainage basin in the "Driftless Area" of southwest Wisconsin. The investigation included aquatic macrophytes, periphytic and planktonic algae, benthic invertebrates, and trout population dynamics during 1967-78. The aquatic community is diverse and reasonably stable with little indication of environmental disturbance. Aquatic macrophyte population (dominated by Ranunculus aquatilis L., Veronica catenata Penn., and Nasturtium offlcinale) varies little from spring to fall. Periphytic and planktonic algae are predominantly diatoms, with the genus Achnanthes dominating both communities. Most genera of planktonic algae originate in the periphyton, but some true planktonic algae were identified. The benthic invertebrate population is dominated by Trichoptera and is a major food source for trout and forage fish. Biotic index values calculated from benthic invertebrate data indicate that water quality is very good to excellent. The trout population is low and represents only a small part of the total fish population both in biomass and numbers. Brown trout are usually stocked annually in the spring to enhance sport fishing, but by fall most trout are wild. The major environmental factors limiting trout population seem to be insufficient cover, insufficient pool depth and volume, and small spawning areas. The wild trout population is highly dependent on spawning success the previous fall.

Wisconsin↗
USGS1991

[Book review] Seabirds of Hawaii: Natural history and conservation

This volume is a rather odd contribution, a hybrid between an academic work and a popular book, and both suffers and benefits from these attributes. The 18 chapters are divided into four parts that deal with the environment and humans (3 chapters and ca. 12% of the text), comparative biology of Hawaiian seabirds (5 chapters, 26%), treatments of Hawaiian seabird groups by family (7 chapters, 34%), and conservation (3 chapters, 16%). At the end of the book are an appendix of common and scientific names for plants, birds, mammals, fish, and a few invertebrates; a 6-page "selected" bibliography with pertinent references for each chapter; and an index.

The Auk↗
USGS2023

Bathymetric, hydrodynamic, biological, and water-quality characteristics of a nearshore area of the Laguna Madre near South Padre Island, Texas, 2021–22

A variety of data were collected by the U.S. Geological Survey, in cooperation with the City of South Padre Island, to better understand the physical and biological habitat in Tompkins Channel and adjacent seagrass beds in the lower Laguna Madre, Texas, where the construction of berms has been proposed in the City of South Padre Island’s Shoreline Master Plan. These berms would be used to create living shorelines, defined as shorelines that “connect the land and water to stabilize the shoreline, reduce erosion, and provide ecosystem services, like [maintaining] valuable habitat, that enhances coastal resilience.” Bathymetric surveys show variability in the lagoon depth within the study area and clearly delineate the relatively shallow bay from the deeper Tompkins Channel. There were seasonal patterns in daily mean tidal water-surface elevations, with higher mean tides in the fall and spring and lower mean tides in the winter and summer. Seasonal differences in mean tidal water-surface elevations were primarily caused by astronomical forces. Shorter-term (daily and weekly) variations in tidal water-surface elevations were produced by meteorological forcing resulting from high- and low-pressure systems, the passage of fronts, local storms, and tropical storms. The tide driven currents typically were toward the north-northwest during flood tide or toward the south-southeast during ebb tide, roughly parallel to the general South Padre Island shoreline orientation. Prevailing water current velocity (current speed and direction) indicates that there usually is a net inflow into the lower Laguna Madre from the Gulf of Mexico and a net outflow at locations north of the study area. The overall seagrass density was generally lowest in the northeast section of the transect. Areas of low seagrass density were also most commonly observed close to the channel edge of the transect. Overall, Syringodium filiforme was considerably more abundant than Thalassia testudinum and Halodule wrightii . Amphipods from the families Ampithoidae and Melitidae were the most abundant benthic invertebrates, followed by gastropods in the family Calyptraeidae. Higher abundances of benthic invertebrates were recorded at sites farther away from Tompkins Channel than at sites closer to it, perhaps because of the sensitivity of these organisms to disturbances caused by erosional forces in the channel. Changes in water-quality measured during a 2-day survey were consistent with patterns observed in prior studies, indicating biological processes likely play an important role in the physicochemical environment of the study area. Collectively, the data provide baseline information that can be used as reference conditions prior to any shoreline enhancement activities in the lower Laguna Madre.

Texas↗
USGS2012

Polar bear and walrus response to the rapid decline in Arctic sea ice

The Arctic is warming faster than other regions of the world due to positive climate feedbacks associated with loss of snow and ice. One highly visible consequence has been a rapid decline in Arctic sea ice over the past 3 decades - a decline projected to continue and result in ice-free summers likely as soon as 2030. The polar bear ( Ursus maritimus ) and the Pacific walrus ( Odobenus rosmarus divergens ) are dependent on sea ice over the continental shelves of the Arctic Ocean's marginal seas. The continental shelves are shallow regions with high biological productivity, supporting abundant marine life within the water column and on the sea floor. Polar bears use sea ice as a platform for hunting ice seals; walruses use sea ice as a resting platform between dives to forage for clams and other bottom-dwelling invertebrates. How have sea ice changes affected polar bears and walruses? How will anticipated changes affect them in the future?

Alaska↗
USGS2020

Physical and chemical stressors on algal, invertebrate, and fish communities in 14 Milwaukee area streams, 2004–2013

In 2004, the U.S. Geological Survey (USGS) began sampling 14 wadable streams in urban or urbanizing watersheds near Milwaukee, Wisconsin. The overall goal of the study is to assess the health of the aquatic communities in the Milwaukee Metropolitan Sewerage District planning area to inform current and future watershed management. In addition to collection of biological data on aquatic communities, physical and chemical data were also collected to evaluate effects of potential environmental stressors on the aquatic communities. This fact sheet summarizes the primary results of the study from 2004 to 2013. Detailed information is described in Scudder Eikenberry and others (2020a), and all data are available in Scudder Eikenberry and others (2020b; https://doi.org/10.5066/P9FWMODL ).

Wisconsin↗
USGS2022

Geomorphology shapes relationships between animal communities and ecosystem function in large rivers

Understanding how the Earth's surface (i.e. ‘nature's stage') influences connections between biodiversity and ecosystem function (BEF) is a central objective in ecology. Despite recent calls to examine these connections at multiple trophic levels and at more complex and realistic scales, little is known about how landscape structure shapes BEF relationships among animal communities in nature. We coupled high-resolution habitat mapping with extensive field sampling to quantify connections among the geophysical habitat templet, invertebrate assemblages and secondary production in two large North American riverscapes. Patterns of sediment size governed invertebrate assemblage structure, with particularly strong effects on composition, richness and taxonomic and functional diversity. These relationships propagated to drive positive relationships between biodiversity and secondary production that were modified by scale, context-dependencies and anthropogenic modification. Finally, leveraging spatially-explicit descriptions of geophysical and biological properties, we uncovered distinct and nested spatial scales of biodiversity and secondary production, and suggest that multiple geophysical processes simultaneously influence these patterns at different scales. Together, our findings advance our understanding of relationships between the physical templet and patterns of BEF, and help to predict how perturbations to the Earth's surface may propagate to influence biodiversity and energy flux through food webs.

Oikos↗
USGS2009

Impact of wildfire on levels of mercury in forested watershed systems: Voyageurs National Park, Minnesota

Atmospheric deposition of mercury to remote lakes in mid-continental and eastern North America has increased approximately threefold since the mid-1800s (Swain and others, 1992; Fitzgerald and others, 1998; Engstrom and others, 2007). As a result, concerns for human and wildlife health related to mercury contamination have become widespread. Despite an apparent recent decline in atmospheric deposition of mercury in many areas of the Upper Midwest (Engstrom and Swain, 1997; Engstrom and others, 2007), lakes in which fish contain levels of mercury deemed unacceptable for human consumption and possibly unacceptable for fish-consuming wildlife are being detected with increasing frequency. In northern Minnesota, Voyageurs National Park (VNP) (fig. 1) protects a series of southern boreal lakes and wetlands situated on bedrock of the Precambrian Canadian Shield. Mercury contamination has become a significant resource issue within VNP as high concentrations of mercury in loons, bald eagle eaglets, grebes, northern pike, and other species of wildlife and fish have been found. The two most mercury-contaminated lakes in Minnesota, measured as methylmercury in northern pike ( Esox lucius ), are in VNP. Recent multidisciplinary U.S. Geological Survey (USGS) research demonstrated that the bulk of the mercury in lake waters, soils, and fish in VNP results from atmospheric deposition (Wiener and others, 2006). The study by Wiener and others (2006) showed that the spatial distribution of mercury in watershed soils, lake waters, and age-1 yellow perch ( Perca flavescens ) within the Park was highly variable. The majority of factors correlated for this earlier study suggested that mercury concentrations in lake waters and age-1 yellow perch reflected the influence of ecosystem processes that affected within-lake microbial production and abundance of methylmercury (Wiener and others, 2006), while the distribution of mercury in watershed soils seemed to be partially dependent on forest disturbance, especially the historic forest fire pattern (Woodruff and Cannon, 2002). Forest fire has an essential role in the forest ecosystems of VNP (Heinselman, 1996). Because resource and land managers need to integrate both natural wildfire and prescribed fire in management plans, the potential influence of fire on an element as sensitive to the environment as mercury becomes a critical part of their decisionmaking. A number of recent studies have shown that while fire does have a significant impact on mercury at the landscape level, the observed effects of fire on aquatic environments are highly variable and unpredictable (Caldwell and others, 2000; Garcia and Carrigan, 2000; Kelly and others, 2006; Nelson and others, 2007). Caldwell and others (2000) described an increase in methylmercury in reservoir sediments resulting from mobilization and transport of charred vegetative matter following a fire in New Mexico. Krabbenhoft and Fink (2000) attributed increases in total mercury concentrations in young-of-the-year fish in the Florida Everglades to release of mercury resulting from peat oxidation following fires. A fivefold increase in whole-body mercury accumulation by rainbow trout ( Oncorhynchus mykiss ) following a fire in Alberta, Canada, apparently resulted from increased nutrient concentrations that enhanced productivity and restructured the food web of a lake within the fire’s burn footprint (Kelly and others, 2006). For this study, we determined the short-term effects of forest fire on mercury concentrations in terrestrial and aquatic environments in VNP by comparing and contrasting mercury concentrations in forest soils, lake waters, and age-1 yellow perch for a burned watershed and an adjacent lake, with similar samples from watersheds and lakes with no fire activity (control watersheds and lakes). The concentration of total mercury in whole, 1-year-old yellow perch serves as a good biological indicator for monitoring trends in methylmercury concentrations in food webs of lakes in North America (Wiener and others, 2007). With a limited gape, age-1 yellow perch that hatched the previous year and resided in a lake for 1 year feed largely on zooplankton and small benthic invertebrates. Thus, age-1 yellow perch provide a baseline for methylmercury concentrations for individual lakes that can be compared across spatial areas. The nine appendixes that accompany this report contain the complete datasets for soils, lake waters, and age-1 yellow perch collected for this study. This report uses data from these three media to provide a framework for evaluating short-term effects of fire on mercury in forested soils and possible effects of the mobilization of mercury from soils on lake water quality and aquatic health.

Minnesota↗
USGS2007

Characterization of habitat and biological communities at fixed sites in the Great Salt Lake basins, Utah, Idaho, and Wyoming, water years 1999-2001

Habitat and biological communities were sampled at 10 sites in the Great Salt Lake Basins as part of the U.S. Geological Survey National Water-Quality Assessment program to assess the occurrence and distribution of biological organisms in relation to environmental conditions. Sites were distributed among the Bear River, Weber River, and Utah Lake/Jordan River basins and were selected to represent stream conditions in different land-use settings that are prominent within the basins, including agriculture, rangeland, urban, and forested. High-gradient streams had more diverse habitat conditions with larger substrates and more dynamic flow characteristics and were typically lower in discharge than low-gradient streams, which had a higher degree of siltation and lacked variability in geomorphic channel characteristics, which may account for differences in habitat. Habitat scores were higher at high-gradient sites with high percentages of forested land use within their basins. Sources and causes of stream habitat impairment included effects from channel modifications, siltation, and riparian land use. Effects of hydrologic modifications were evident at many sites. Algal sites where colder temperatures, less nutrient enrichment, and forest and rangeland uses dominated the basins contained communities that were more sensitive to organic pollution, siltation, dissolved oxygen, and salinity than sites that were warmer, had higher degrees of nutrient enrichment, and were affected by agriculture and urban land uses. Sites that had high inputs of solar radiation and generally were associated with agricultural land use supported the greatest number of algal species. Invertebrate samples collected from sites where riffles were the richest-targeted habitat differed in species composition and pollution tolerance from those collected at sites that did not have riffle habitat (nonriffle sites), where samples were collected in depositional areas, woody snags, or macrophyte beds. Invertebrate taxa richness, pollution tolerance, and trophic interactions at riffle and nonriffle sites responded differently to environmental variables. Fish communities were assessed in relation to the designated beneficial use for aquatic life for each site. Fish-community sites in basins where agriculture and urbanization were prevalent consistently had poorer conditions than sites with forest and rangeland uses. Warm temperatures appear to be limiting most native fish species, and more introduced, warm-water fish species were present at sites with warmer temperatures. Ranges of environmental conditions where native species were present or absent were identified. The farthest-upstream site in each of the three basins had better ecological condition overall, as indicated by the integrity of habitat and the presence of more sensitive algae, invertebrate, and fish species than were observed at sites downstream. The farthest-downstream site in each of the three basins showed the poorest ecological condition, with more tolerant organisms present, degraded habitat and water-quality conditions, and a high degree of effects from agriculture, grazing, and urbanization. Of the mid-basin sites, the site most affected by urbanization had more degraded biological condition than the agricultural indicator site of similar basin size.

Idaho, Utah, Wyoming↗
USGS2013

Comparing mechanisms of host manipulation across host and parasite taxa

Parasites affect host behavior in several ways. They can alter activity, microhabitats or both. For trophically transmitted parasites (the focus of our study), decreased activity might impair the ability of hosts to respond to final-host predators, and increased activity and altered microhabitat choice might increase contact rates between hosts and final-host predators. In an analysis of trophically transmitted parasites, more parasite groups altered activity than altered microhabitat choice. Parasites that infected vertebrates were more likely to impair the host’s reaction to predators, whereas parasites that infected invertebrates were more likely to increase the host’s contact with predators. The site of infection might affect how parasites manipulate their hosts. For instance, parasites in the central nervous system seem particularly suited to manipulating host behavior. Manipulative parasites commonly occupy the body cavity, muscles and central nervous systems of their hosts. Acanthocephalans in the data set differed from other taxa in that they occurred exclusively in the body cavity of invertebrates. In addition, they were more likely to alter microhabitat choice than activity. Parasites in the body cavity (across parasite types) were more likely to be associated with increased host contact with predators. Parasites can manipulate the host through energetic drain, but most parasites use more sophisticated means. For instance, parasites target four physiological systems that shape behavior in both invertebrates and vertebrates: neural, endocrine, neuromodulatory and immunomodulatory. The interconnections between these systems make it difficult to isolate specific mechanisms of host behavioral manipulation.

Journal of Experimental Biology↗
USGS1977

Limnological studies of the major streams in Chester County, Pennsylvania

The major streams in Chester County, Pennsylvania were studied to determine their environmental state, and to relate this condition to land- use patterns. A biological numerical rating system on a scale of 1 to 10 was developed to classify stream conditions. One indicates extremely toxic conditions and 10 balanced biological conditions. The majority of the streams studied had ratings between 4 and 8, indicating they were experiencing varying degrees of enrichment and/or sediment deposition. The streams with high numerical ratings were generally found in rural and agricultural areas. Streams with low numerical rating were found mostly in areas near waste treatment facilities or industry. Large changes in the numerical rating of a stream were related to changes in land-use patterns. Relationships were developed between dissolved solids concentrations and the biological numerical ratings of the streams. Streams with ratings from 6 to 10 had dissolved solids concentrations of approximately 100 mg/L. At ratings of 5 to 1, the dissolved solids concentrations increased progressively from 122 to 310 mg/L. Chemical data for the streams were related to the dominant orders of benthic invertebrates. The stoneflies were found to be the most sensitive to high levels of chemical constituents. The trueflies, mayflies, and caddis flies showed a wide tolerance to various chemical constituents.

Pennsylvania↗
USGS2024

Lack of strong responses to the Pacific marine heatwave by benthivorous marine birds indicates importance of trophic drivers

The Pacific marine heatwave (PMH) of 2014-2016 was an intense, long-lasting environmental disturbance expressed throughout the north Pacific. While dramatic consequences of the PMH on pelagic food webs have been well documented, effects on nearshore food webs, i.e., those based on macroalgae primary productivity, benthic invertebrate intermediate consumers, and specialized benthivorous top predators including some marine birds, are not well understood. We conducted summer and winter coastline surveys in two National Parks in the northern Gulf of Alaska from 2006 – 2022. We evaluated changes in abundance of benthivorous marine birds in relation to the heatwave, after accounting for effects of season and region. We also evaluated changes in abundance of nearshore benthic invertebrate prey data to allow specific consideration of a prey-based mechanism for effects of the PMH across food webs. We found that benthivorous marine birds, consisting largely of sea ducks and shorebirds, did not show a strong response to the PMH, unlike significant effects demonstrated by piscivorous birds in pelagic biomes. Unlike extreme reductions in quantity and quality of forage fish documented in other studies, we found that common benthic invertebrate prey abundance remained relatively stable, with only minor increases or decreases, in association with the PMH. Our results support the hypothesis that food availability has a strong mediating effect of the PMH on upper trophic levels across food webs. These findings show how a large-scale environmental perturbation affects biological communities through trophic pathways, provides insight into ecosystem resiliency, and can inform management strategies in the face of persistent climate change.

Alaska↗
USGS1996

Effects of the eruptions of Mount St. Helens on physical, chemical, and biological characteristics of surface water, ground water, and precipitation in the Western United States

Over 120 publications that describe the 1980 eruption effects of Mount St. Helens on rivers, lakes, and the Columbia River estuary are reviewed. Water-quality changes ranged from minor, short-lived effects, to totally altered drainage basins and newly created lakes. Turbidity increased; concentrations of cations, anions, and dissolved organic carbon increased. Migrating fish were adversely affected; benthic-invertebrate populations changed. Ground-water levels rose near the Cowlitz River. Precipitation effects included transient, but increased specific conductance and decreased pH.

Water Supply Paper↗
USGS2011

Nearshore biological communities prior to the removal of the Elwha River dams: Chapter 6 in Coastal habitats of the Elwha River, Washington--biological and physical patterns and processes prior to dam removal

Increases in sediment delivery to coastal waters are expected following removal of dams on the Elwha River, Washington, potentially increasing sediment deposition on the seafloor and suspended sediment in the water column. Biological communities inhabiting shallow, subtidal depths (3–18 m) near the mouth of the Elwha River, between the west end of Freshwater Bay and the base of Ediz Hook, were surveyed in August and September 2008, to establish baselines prior to dam removal. Density was estimated for 9 kelp taxa, 65 taxa of invertebrates larger than 2.5 cm any dimension and 24 fish taxa. Density averaged over all sites was 3.1 per square meter (/m 2 ) for kelp, 2.7/m 2 for invertebrates, and 0.1/m 2 for fish. Community structure was partly controlled by substrate type, seafloor relief, and depth. On average, 12 more taxa occurred where boulders were present compared to areas lacking boulders but with similar base substrate. Four habitat types were identified: (1) Bedrock/boulder reefs had the highest kelp density and taxa richness, and were characterized by a canopy of Nereocystis leutkeana (bull kelp) at the water surface and a secondary canopy of perennial kelp 1–2 m above the seafloor; (2) Mixed sand and gravel-cobble habitats with moderate relief provided by boulders had the highest density of invertebrates and a taxa richness nearly equivalent to that for bedrock/boulder reefs; (3) Mixed sand and gravel-cobble habitats lacking boulders supported a moderate density of kelp, primarily annual species with low growth forms (blades close to the seafloor), and the lowest invertebrate density among habitats; and (4) Sand habitats had the lowest kelp density and taxa richness among habitats and a moderate density of invertebrates. Uncertainties about nearshore community responses to increases in deposited and suspended sediments highlight the opportunity to advance scientific understanding by measuring responses following dam removal.

Washington↗
USGS2010

Evaluation of aquatic biota in relation to environmental characteristics measured at multiple scales in agricultural streams of the Midwest: 1993-2004

This study evaluated the relations between algal, invertebrate, and fish assemblages and physical environmental characteristics of streams at the reach, segment, and watershed scale in agricultural settings in the Midwest. The 86 stream sites selected for study were in predominantly agricultural watersheds sampled as part of the U.S. Geological Survey's National Water-Quality Assessment Program. Species abundance and over 130 biological metrics were used to determine which aspects of the assemblages were most sensitive to change at the three spatial scales. Digital orthophotograph-based riparian land use/land cover was used for analyses of riparian conditions at the reach and segment scales. The percentage area of different land-use/land-cover types was also determined for each watershed. Out of over 230 environmental characteristics examined, those that best explained variation in the biotic assemblages at each spatial scale include the following: 1) reach: bank vegetative cover, fine silty substrate, and open canopy angle; 2) segment: woody vegetation and cropland in the 250-m riparian buffer, and average length of undisturbed buffer; and 3) watershed: land use/land cover (both total forested and row crop), low-permeability soils, slope, drainage area, and latitude. All three biological assemblages, especially fish, correlated more with land use/land cover and other physical characteristics at the watershed scale than at the reach or segment scales. This study identifies biotic measures that can be used to evaluate potential improvements resulting from agricultural best-management practices and other conservation efforts, as well as evaluate potential impairment from urban development or other disturbances.

Midwest↗
USGS2011

Aquatic ecology of the Elwha River estuary prior to dam removal: Chapter 7 in Coastal habitats of the Elwha River, Washington--biological and physical patterns and processes prior to dam removal

The removal of two long-standing dams on the Elwha River in Washington State will initiate a suite of biological and physical changes to the estuary at the river mouth. Estuaries represent a transition between freshwater and saltwater, have unique assemblages of plants and animals, and are a critical habitat for some salmon species as they migrate to the ocean. This chapter summarizes a number of studies in the Elwha River estuary, and focuses on physical and biological aspects of the ecosystem that are expected to change following dam removal. Included are data sets that summarize (1) water chemistry samples collected over a 16 month period; (2) beach seining activities targeted toward describing the fish assemblage of the estuary and migratory patterns of juvenile salmon; (3) descriptions of the aquatic and terrestrial invertebrate communities in the estuary, which represent an important food source for juvenile fish and are important water quality indicators; and (4) the diet and growth patterns of juvenile Chinook salmon in the lower Elwha River and estuary. These data represent baseline conditions of the ecosystem after nearly a century of changes due to the dams and will be useful in monitoring the changes to the river and estuary following dam removal.

Washington↗
USGS1983

Reconnaissance of surface-water resources in the Kobuk River basin, Alaska, 1979-80

Surface water data were collected at selected sites in the Kobuk River Basin in northwest Alaska in August 1979 and April 1980. In August 1979, frequent heavy rains caused abnormally high flows in the basin; unit runoff values, computed from discharge measurements at 25 sites, ranged from 0.08 to 12.2 cu ft/sec/sq mi. Mean unit runoff for August computed from 13 years of record at a stream gaging station on the Kobuk River ranged from 1 to 3 cu ft/sec/sq mi. Unit runoff computed from discharge measurements made at eight sites in April 1980 ranged from 0 to 0.30 cubic feet per second per square mile. These values are in reasonable agreement with those derived from the record at the gaging station. High-water marks of maximum evident floods and evidence of ice-affected flooding were found at near bankfull stages at 17 sites on the Kobuk River and its tributaries. Computed unit runoff for the maximum evident floods generally decreases with increasing drainage area. Unit runoff ranges from about 50 to 75 cu ft/sec/sq mi for drainage areas < 1,000 sq mi to < 25 cu ft/sec/sq mi for larger areas. Field determinations were made of water temperature, pH, alkalinity, dissolved-oxygen concentration, and specific conductance, and discharge was measured at about 40 stream sites and one spring. Water samples for laboratory analysis of dissolved inorganic constituents and biological samples were collected in August 1979. Water quality data indicate that the surface waters would be acceptable for most uses; they are a calcium bicarbonate type having dissolved-solids concentrations between 50 and 140 milligm/liter. The pristine nature of the waters is also indicated by the overall diversity and composition of its benthic invertebrate community. A more highly mineralized (about 550 milligm/liter dissolved solids) sodium bicarbonate water flows from Reed River Hot Spring. (USGS)

Water-Resources Investigations Report↗
USGS2005

An evaluation of effects of groundwater exchange on nearshore habitats and water quality of western Lake Erie

Historically, the high potentiometric surface of groundwater in the Silurian/Devonian carbonate aquifer in Monroe County, MI resulted in discharge of highly mineralized, SO 4 -rich groundwater to the Lake Erie shoreline near both Erie State Game Area (ESGA) and Pointe Mouillee State Game Area (PMSGA). Recently, regional groundwater levels near PMSGA have been drawn down as much as 45 m below lake level in apparent response to quarry dewatering. From August to November of 2003, we conducted preliminary studies of groundwater flow dynamics and chemistry, shallow lake water chemistry, and fish and invertebrate communities at both sites. Consistent with regional observations, groundwater flow direction in the nearshore at ESGA was upward, or toward Lake Erie, and shallow nearshore groundwater chemistry was influenced by regional groundwater chemistry. In contrast, at PMSGA, the groundwater flow potential was downward and lake water, influenced by quarry discharge seeping downward into nearshore sediments, produced a different lake and shallow groundwater chemistry than at ESGA. Although the invertebrate and young fish community was similar at the two sites, taxonomic groups tolerant of degraded water quality were more prevalent at PMSGA. Sensitive taxa were more prevalent at ESGA. We propose a conceptual model, based on well-described models of groundwater/seawater interaction along coastal margins, to describe the interconnection among geologic, hydrologic, chemical, and biological processes in the different nearshore habitats of Lake Erie, and we identify processes that warrant further detailed study in the Great Lakes.

Lake Erie↗
USGS2025

Arsenic accumulation in Sonora Mud Turtles (Kinosternon sonoriense) in an unusual freshwater food web

Montezuma Well is an unusual fishless, spring-fed, desert wetland in central Arizona. Water in the wetland is naturally enriched with > 100 µg/l dissolved geogenic arsenic (As) and supports a simple aquatic food web dominated by a small number of endemic invertebrate species that achieve high abundances. Previous studies of As among various environmental compartments and organisms in Montezuma Well did not include omnivorous Sonora Mud turtles ( Kinosternon sonoriense ) despite their potential importance in the As cycle by virtue of their substantial biomass and role as top predators. We measured As concentrations in water, sediment, and organisms (macrophytes, amphipods, insects, leeches, and turtles) representing a range of trophic levels in order to document the importance of turtles at the apex of the Montezuma Well food web and in the As cycle. Concentrations of As in turtles varied according to tissue type. The greatest values (up to 26.77 mg/kg dry weight) were in the scutes of 1 of our oldest turtles (31.5 yrs). These elevated concentrations may be due to the affinity of As to react with sulfur in the keratin of scutes, and therefore might reflect duration of exposure in long-lived turtles. Although As concentrations generally tend to decrease when moving up to higher trophic levels in a food web, our results were different. Relatively elevated concentrations reported in sediments by us and a previous study declined in plant samples as expected. Amphipod concentrations increased but then decreased again in 3 of their invertebrate predators. Arsenic concentrations in endemic leeches were extremely elevated with a mean value of 72.2 mg/kg. The mean concentration of As in turtles was 7.08 mg/kg across tissue types and was greater than the plants or invertebrates they eat, with the notable exception of leeches, which have been proposed to be part of their diet.

Arizona↗