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At least 415 records · Page 23Linked to original sources

USGS2000

Linkage of bioaccumulation and biological effects to changes in pollutant loads in south San Francisco Bay

The developed world has invested billions of dollars in waste treatment since the 1970s; however, changes in ecological or biological responses are rarely associated with reductions in metal pollutants. Here we present a novel, 23-yr time series of environmental change from a San Francisco Bay mudflat located 1 km from the discharge of a suburban domestic sewage treatment plant. Samples of surface sediment, the bioindicator Macoma balthica , and metals loading data were used to establish links between discharge, bioaccumulation, and effects. Mean annual Ag concentrations in M. balthica were 106 μg/g in 1978 and 3.67 μg/g in 1998. Concentrations of Cu declined from 287 μg/g in 1980 to a minimum of 24 μg/g in 1991. Declining Cu bioaccumulation was strongly correlated with decreasing Cu loads from the plant between 1977 and 1998. Relationships with bioaccumulation and total annual precipitation suggested that inputs from nonpoint sources were most important in controlling Zn bioavailability during the same period. Ecoepidemiological criteria were used to associate failed gamete production in M. balthica to a metals-enriched environment. Reproduction persistently failed between the mid-1970s and mid-1980s; it recovered after metal contamination declined. Other potential environmental causes such as food availability, sediment chemistry, or seasonal salinity fluctuations were not related to the timing of the change in reproductive capability. The results establish an associative link, suggesting that it is important to further investigate the chemical interference of Cu and/or Ag with invertebrate reproduction at relatively moderate levels of environmental contamination.

California↗

USGS1975

A river-quality assessment of the upper White River, Indiana

This report attempts to interrelate the physical, chemical, biological, esthetic, and cultural aspects of the upper White River (above Centerton, Ind.) by assessing the mass of available data. Relatively few new data were collected. The White River can be subdivided into five distinct river-quality sections. Section 1, above Winchester, drains a rural area and is affected by agricultural land use, although the river quality generally is good. Section 2, between Winchester and Muncie, is affected by urbanization at Winchester and Muncie. The river quality generally is good, although stretches near the cities occasionally have problems. Section 3, Muncie to Anderson, is polluted by urban effluent. Section 4, Anderson to Indianapolis, is further polluted (particularly at Anderson), but the river tends to recover considerably at Indianapolis, and becomes relatively clean. Section 5, below Indianapolis, is polluted. The river continues to be polluted below the project boundary. The river is affected most severely in the Indianapolis area. For example, in October 1972 the nitrogen load increased from 5.45 tons per day (4.94 tonnes per day) above Indianapolis to 18.43 tons per day (16.72 tonnes per day) below the city. Ten micrograms per kilogram of DDD, 20 micrograms per kilogram of chlordane, and 20 micrograms per kilogram of polychlorinated biphenyls were extracted from the sediments in the White River below Indianapolis. The median coliform bacteria count below Indianapolis is 360,000 colonies per 100 millilitres of water. The only benthic invertebrates found in the White River below Indianapolis are pollution-tolerant species, and very few fish are found. Conditions are similar, but to a somewhat lesser degree, below Muncie.

Indiana↗

USGS2023

Global review reveals how disparate study motivations, analytical designs, and focal ions limit understanding of salinization effects on freshwater animals

Global salinization of freshwaters is adversely affecting biotic communities and ecosystem processes. We reviewed six decades (1960–2020) of literature published on animal responses to increased salinities across different taxonomic and ecological contexts and identified knowledge gaps. From 585 journal articles, we characterized 5924 responses of mollusks, crustaceans, zooplankton, non-arthropod invertebrates (NAI), insects, fishes, and amphibians to salinization. Insects and fishes were the most studied taxa; Na + and Cl − were the most studied ions − . Collectively, concentrations of the ions examined typically spanned five orders of magnitude. Species' invasiveness was a key motivation for studying mollusks, crustaceans, and fishes; threats of urbanization and road salts were key motivations for studying NAI, zooplankton, and amphibians. Laboratory studies were more common than field studies for most taxa. Focal life stages in laboratory studies varied widely but juveniles and adults were represented similarly in field studies. Studies of mollusks, NAI, and crustacean focused on adults; studies of zooplankton, insects, fishes, and amphibians focused on juveniles. Organismal- and population-level responses measuring solute uptake, internal chemistry, body condition, or ion concentrations predominated laboratory studies; population- and assemblage-level responses measuring abundance, spatial distribution, or assemblage composition predominated field studies. Negative responses to salinization predominated but positive and unimodal responses were apparent across all taxa and organizational levels. Key topics for further research include a) salinity responses by more taxa, b) responses to especially toxic ions (i.e., potassium, bicarbonate, sulfate, magnesium), c) mechanisms causing positive and unimodal responses, d) traits underpinning responses, e) effects transcending organizational levels, f) ion-specific response thresholds, and g) interactions between salinity and other stressors. Our review suggests inter-taxa variation in sensitivity to salinization reflects occurrence of certain biological traits, including gill-breathing, semi-permeable skin, multiple life stages, and limited mobility. We propose a traits-based framework to predict salinization sensitivity from shared traits. This evolutionary approach could inform management aimed at preventing or reducing adverse impacts of freshwater salinization.

Science of the Total Environment↗

USGS2007

Persistent near-bottom aggregations of mesopelagic animals along the North Carolina and Virginia continental slopes

Submersible observations during four missions over the North Carolina and Virginia continental slopes (184–900 m) documented the occurrence of large aggregations of mesopelagic fishes and macronektonic invertebrates near or on the bottom. Aggregated mesopelagics formed a layer up to tens of meters deep positioned from a few centimeters to 20 m, usually <10 m, above the substrate. Aggregations were numerically dominated by microvores, notably the myctophid fish Ceratoscopelus maderensis and the penaeid shrimp Sergestes arcticus . Consistently present but in relatively lower numbers, were mesopelagic predators, including the paralepidids Notolepis rissoi and Lestidium atlanticum , the eel Nemichthys scolopaceus , the stomiid fishes Chauliodus sloani and Stomias boa ferox , and squids Illex spp. Near-bottom aggregations do not appear to be an artifact due to attraction to the submersible. Based on submersible observations in three areas in 4 years spanning a decade, near-bottom aggregations of midwater organisms appear to be a geographically widespread and persistent phenomenon along the continental slope of the southeastern US Aggregations may exploit areas of enhanced food resources at the bottom.

North Carolina, Virginia↗

USGS2003

The relationships among three habitat scales and stream benthic invertebrate community structure

1. The relationships between three habitat scales and lotic invertebrate species composition were investigated for the 15 540 km 2 Yakima River basin in south-central Washington, U.S.A. 2. The three spatial scales were sample (the sampled riffle), reach (a length of ten–twenty stream widths) and segment (a length of stream of nearly uniform slope and valley form having no change in stream order). 3. Physical variables were highly correlated between scales and expressed a relationship between altitude, basin form and small-scale physical structure. 4. Multiple discriminant function analyses indicated that segment- and reach-scale variables discriminated among species-defined groups better than sample-scale variables. 5. Species composition varied along a complex altitudinal gradient of changing basin form and resultant land use. 6. There was no clear relationship between species richness and altitude on a site basis. However, when viewed at the basin scale, maximum richness was observed at the transition between montane and valley sites.

Freshwater Biology↗

USGS2016

Potential utility of environmental DNA for early detection of Eurasian watermilfoil ( Myriophyllum spicatum )

Considering the harmful and irreversible consequences of many biological invasions, early detection of an invasive species is an important step toward protecting ecosystems (Sepulveda et al. 2012). Early detection increases the probability that suppression or eradication efforts will be successful because invasive populations are small and localized (Vander Zanden et al. 2010). However, most invasive species are not detected early because current tools have low detection probabilities when target species are rare and the sampling effort required to achieve acceptable detection capabilities with current tools is seldom tractable (Jerde et al. 2011). As a result, many invasive species go undetected until they are abundant and suppression efforts become costly. Novel DNA-based surveillance tools have recently revolutionized early detection abilities using environmental DNA (eDNA) present in the water (Darling and Mahon 2011, Bohmann et al. 2014). In brief, eDNA monitoring enables the identification of organisms from DNA present and collected in water samples. Aquatic and semiaquatic organisms release DNA contained in sloughed, damaged, or partially decomposed tissue and waste products into the water and molecular techniques allow this eDNA in the water column to be identified from simple and easy-tocollect water samples (Darling and Mahon 2011). Despite limited understanding of the production, persistence, and spread of DNA in water (Barnes et al. 2014), eDNA monitoring has been applied not only to invasive species (Jerde et al. 2011), but also to species that are rare, endangered, or highly elusive (Spear et al. 2014). However, most eDNA research and monitoring has focused on detection of invertebrates and vertebrates and less attentionhas been given to developing eDNA techniques for detecting aquatic invasive plants. Eurasian watermilfoil (EWM; Myriophyllum spicatum L.) is an invasive species for which improved early detection would be particularly helpful. Advanced EWM invasions have negative impacts on native biodiversity, recreational boating, fishing, and other types of aquatic tourism (e.g., Eiswerth et al. 2000). On a broader scale, EWM can also be harmful to man-made aquatic infrastructure, such as hydroelectric dams. If an EWM invasion can be detected in an early stage where eradication is still a possibility, many of these negative consequences can be limited or prevented altogether (e.g., Madsen et al. 2002). The purpose of this research was to develop and validate a traditional polymerase chain reaction (PCR) assay for the detection of pure and hybridized EWM DNA using both laboratory and field experiments. We performed a pilot experiment in outdoor tanks to determine the basic functionality and sensitivity of the assay. Following this initial test, we collected field samples from Michigan and Montana lakes with and without known EWM populations. Taken together, our findings suggest that eDNA techniques have potential to be a useful strategy for the early detection of EWM.

Journal of Aquatic Plant Management↗

USGS2002

Evaluation of the effects of turbulence on the behaviour of migratory fish

The fundamental influence of fluid dynamics on aquatic organisms is receiving increasing attention among aquatic ecologists. For example, the importance of turbulence to ocean plankton has long been a subject of investigation (Peters and Redondo 1997). More recently, studies have begun to emerge that explicitly consider the effects of shear and turbulence on freshwater invertebrates (Statzner et al. 1988; Hart et al. 1996) and fishes (Pavlov et al. 1994, 1995). Hydraulic shear stress and turbulence are interdependent natural hydraulic phenomena that are important to fish, and consequently it is important to develop an understanding of how fish sense, react to, and perhaps utilize these phenomena under normal river flows. The appropriate reaction to turbulence may promote movement of migratory fish (Coutant 1998) or prevent displacement of resident fish. It has been suggested that one of the adverse effects of flow regulation by hydroelectric projects is the reduction of normal turbulence, particularly in the headwaters of reservoirs, which can lead to disorientation and slowing of migration (Williams et al. 1996; Coutant et al. 1997; Coutant 1998). On the other hand, greatly elevated levels of shear and turbulence may be injurious to fish; injuries can range from removal of the mucous layer on the body surface to descaling to torn opercula, popped eyes, and decapitation (Neitzel et al. 2000a,b). Damaging levels of fluid stress, such turbulence, can occur in a variety of circumstances in both natural and man-made environments. This report discusses the effects of shear stress and turbulence on fish, with an emphasis on potentially damaging levels in man-made environments. It defines these phenomena, describes studies that have been conducted to understand their effects, and identifies gaps in our knowledge. In particular, this report reviews the available information on the levels of turbulence that can occur within hydroelectric power plants, and the associated biological effects. Furthermore, this report describes an experimental apparatus designed to test the effect of turbulence on fish, and defines its hydraulics. It gives the results of experiments in which three different fish species were exposed to representative levels of turbulence in the laboratory.

Bonneville Power Administration Report↗

USGS2022

Potential effects of energy development on environmental resources of the Williston Basin in Montana, North Dakota, and South Dakota—Species of conservation concern

The ecosystems of the Williston Basin provide direct and indirect benefits to society. These benefits include carbon sequestration, flood control, nutrient rich soils for agricultural productivity, and habitat for wildlife. This chapter’s main focus is on the effects of energy development on species that occupy the ecosystems in the Williston Basin. We compiled a list of documented species of conservation concern that are of most interest to Federal regulators and resource managers. Species of concern were either listed as endangered or threatened under the Endangered Species Act or listed by States as species of concern in Natural Heritage Program checklists or State Wildlife Action Plans. All told, we determined that 357 species of concern likely occupy the Williston Basin. These species represented seven different taxonomic groups: plants (native and nonnative), terrestrial invertebrates, birds, mammals, reptiles and amphibians, and fish and mussels. We reviewed the existing scientific information pertaining to potential effects of energy development on these taxonomic groups. Currently, little is known about the abundance and distribution of many of these species. But some information exists that may be useful in predicting the potential effects of energy development on certain taxonomic groups. Most of this information has been developed through scientific research focused on effects to mammal and bird populations. Effects to other taxonomic groups seems to be understudied. In general, it seems that disturbances and modifications associated with development have the potential to negatively affect a wide range of species; however, many studies produce uncertain results because they are not designed to compare populations before and after energy development takes place. Most of these studies also do not monitor resources over multiple years and thus cannot detect population trends. Likewise, there are few examples of landscape-scale assessments of the cumulative effects of energy development that could be used for species or habitat management purposes. We suggest that more research needs to be completed to measure potential effects to a broad range of species in multiple taxonomic groups. This may require also developing some understanding about the basic ecology of many of the species covered in this report. In concert with this more basic research, we also suggest that more comprehensive assessments of potential negative cumulative effects across the Williston Basin should be developed in an effort to guide more strategic management of biological resources.

Montana, North Dakota, South Dakota↗

USGS2017

Effects of the biopesticide Zequanox® on reproduction and early development of the fathead minnow ( Pimephales promelas )

The biopesticide, Zequanox®, is registered for dreissenid mussel control in open water systems in the United States. Previous toxicity trials with nontarget organisms, including several young-of-the-year fish species and invertebrates, demonstrated selectivity of Zequanox for dreissenid mussels, but data are lacking on the treatment-related effects on reproduction and early life stage development of fish. The present study evaluated the effects of Zequanox on spawning and early life stages of the fathead minnow, Pimephales promelas , after exposure to the maximum approved concentration [100 mg active ingredient (AI)/L] and exposure duration (8h) for open water application. The results showed no significant treatment-related effect of Zequanox on survival, condition, or cumulative egg production (21 d) in adult fathead minnow. Eggs (≤24 h old) exposed to Zequanox developed to the eyed-stage at a similar rate to that of untreated eggs. Additionally, Zequanox did not have a significant effect on survival and growth (90 d) of newly hatched larvae (≤24-h old). Zequanox may be an option for control of dreissenid mussels in localized open water habitats where concerns exist regarding reproduction and recruitment of cyprinids and related species.

Management of Biological Invasions↗

USGS2017

Octocoral diseases in a changing ocean

Octocorals (Cnidaria, Octocorallia) constitute a geographically widely distributed and common group of marine invertebrates commonly referred to as “soft-corals,” “sea fans,” “horny corals,” “sea feathers,” and “sea plumes.” They are found from shallow coastal habitats to mesophotic and abyssal depths. Octocorals are important members of most Atlantic-Caribbean, Indo-Pacific, and Mediterranean coastal and mesophotic reef communities; however, information about their susceptibility to diseases, predation, and competition, and their relationship with changing environmental conditions is limited. At least 19 diseases have been observed in at least 42 common octocoral species throughout their range. Twelve of these have been reported in the wider Caribbean (CA), one in Brazil (BR), two in the Mediterranean (ME), one in the Eastern Pacific (EP), and three in the western Pacific (WP). Pathogenic and/or environmental causes have been identified for eight diseases, including viruses, terrestrial fungi, protozoans, bacteria and cyanobacteria, filamentous algae, parasitic copepods, and high temperature. Only a few of the suspected pathogens have been tested with Koch’s postulates. At least eight disease outbreaks have led to extensive octocoral mortalities in the CA, ME, BR, and EP with detrimental ecological consequences. The fungal disease Aspergillosis has produced the highest mortalities in the CA and the EP. Other fungi, protozoans, and the bacterium Vibrio coralliilyticus were identified as potential causes of the death of millions of colonies in two Mediterranean disease outbreaks. Bacterial and fungal agents seemed to be responsible for the mass mortalities in Brazil and the WP. Most outbreaks in all regions were linked to high thermal anomalies associated with climate change, which seems to be the major driver. Other biological stressors such as predation and/or competition produce injuries that may contribute to the spread of infections and mortality. Overfishing of common predators could lead to population explosions of octocoral-feeding species that produced mass mortalities in some Caribbean localities. Our lack of knowledge of causes and pathogenesis of octocoral diseases parallels that of hard corals. New diseases are being described almost every year concomitant with increasing seawater temperatures. The ecological and economic consequences could be significant, with drastic changes in the seascape of shallow coral reefs and other coastal marine habitats and reduction of their ecological services. Given our limited knowledge, our best options for recovery of octocorals and coral reefs in general include sound management of coastal fisheries, development and tourism; reduction of land- and sea-based pollution; and abating effects of climate change.

Book chapter↗

USGS2024

Diet of Dermatemys mawii, an aquatic turtle that relies heavily on terrestrial vegetation

Dermatemys mawii is a critically endangered freshwater turtle endemic to Central America. In the wild, these turtles are thought to be wholly herbivorous as adults and feed on a variety of vegetation; however, no studies have quantitatively assessed potential dietary differences based on biotic and abiotic factors. The purpose of our study was to describe and quantify the wild diet of D. mawii and assess differences based on habitat, maturity, and sex. We evaluated the stomach contents of 66 turtles legally harvested by local hunters for personal consumption throughout the country of Belize. Percent volume (by displacement) and percent frequency of each stomach item were used to calculate an index of relative importance (IRI). One algal and 6 plant families contributed to an overall diet composition consisting of leaves, flowers, stems, seedpods, seeds, and fruit. Rocks and invertebrates were also consumed, although we believe these to be incidental consumption. The leaves of the riparian tree Inga edulis were present in 73.1% of turtle stomachs and accounted for almost half of the total volume of all stomach contents combined. We used Spearman rank correlation coefficients to test the null hypothesis that there was no correlation in the rankings of stomach items (i.e., there were differences) when comparing turtles by habitat, age, and sex. There were significant differences in the ranking of food items between river and lagoon habitats, with lagoon turtles relying heavily on the algae Nitella sp.; however, the stomach contents from both habitats were equally diverse (H rivers = 1.68, H lagoons = 1.64). There were no differences in IRIs between adults and juveniles or between males and females. Our results emphasize the importance of habitat in D. mawii diet selection and the importance of leaves from riparian plants species that are shed into their aquatic habitats.

Chelonian Conservation and Biology↗

USGS2002

Influence of the proximity and amount of human development and roads on the occurrence of the red imported fire ant in the lower Florida Keys

We examined the influence of both the proximity and extent of human developments and paved roads on the presence of the predatory, non-indigenous, red imported fire ant (Solenopsis invicta). This species was inadvertently introduced into the United States at the port of Mobile, Alabama, around 1930 and rapidly spread to many southeastern states, including Florida. More recently, S. invicta colonized the Florida Keys, an area with a high proportion of rare and endemic vertebrate and invertebrate species. We placed bait transects in transitional salt-marsh, pineland, and hardwood hammocks on 13 of the lower Florida Keys and compared habitat type, the shortest distance of the bait transect to a development or road, and area of development and roads 50, 70, 100, and 150 m around each bait transect for areas with and without red imported fire ants. Red imported fire ants were detected on 21 of the 80 transects and were equally abundant in all habitat types. While all of the development and road variables differed significantly between bait transects with and without red imported fire ants, transects that were closest to roads and that had the largest amount of development within a 150 m radii had the highest probability of presence of red imported fire ants. Recovery efforts for endangered species in areas invaded by red imported fire ants should include analyses of the cumulative impacts of roads and developments in areas near protected lands. ?? 2002 Elsevier Science Ltd. All rights reserved.

Biological Conservation↗

USGS2015

Diet of yellow-billed loons ( Gavia adamsii ) in Arctic lakes during the nesting season inferred from fatty acid analysis

Understanding the dietary habits of yellow-billed loons ( Gavia adamsii ) can give important insights into their ecology, however, studying the diet of loons is difficult when direct observation or specimen collection is impractical. We investigate the diet of yellow-billed loons nesting on the Arctic Coastal Plain of Alaska using quantitative fatty acid signature analysis. Tissue analysis from 26 yellow-billed loons and eleven prey groups (nine fish species and two invertebrate groups) from Arctic lakes suggests that yellow-billed loons are eating high proportions of Alaska blackfish ( Dallia pectoralis ), broad whitefish ( Coregonus nasus ) and three-spined stickleback ( Gasterosteus aculeatus ) during late spring and early summer. The prominence of blackfish in diets highlights the widespread availability of blackfish during the early stages of loon nesting, soon after spring thaw. The high proportions of broad whitefish and three-spined stickleback may reflect a residual signal from the coastal staging period prior to establishing nesting territories on lakes, when loons are more likely to encounter these species. Our analyses were sensitive to the choice of calibration coefficient based on data from three different species, indicating the need for development of loon-specific coefficients for future study and confirmation of our results. Regardless, fish that are coastally distributed and that successfully overwinter in lakes are likely key food items for yellow-billed loons early in the nesting season.

Alaska↗

USGS2022

Environmental filtering controls soil biodiversity in wet tropical ecosystems

The environmental factors controlling soil biodiversity along resource gradients remain poorly understood in wet tropical ecosystems. Aboveground biodiversity is expected to be driven by changes in nutrient availability in these ecosystems, however, much less is known about the importance of nutrient availability in driving soil biodiversity. Here, we combined a cross-continental soil survey across tropical regions with a three decades' field experiment adding nitrogen (N) and phosphorus (P) (100 kg N ha −1 y −1 and 100 kg P ha −1 y −1 ) to Hawai'ian tropical forests with contrasting substrate ages (300 and 4,100,000 years) to investigate the influence of nutrient availability to explain the biodiversity of soil bacteria, fungi, protists, invertebrates and key functional genes. We found that soil biodiversity was driven by soil acidification during long-term pedogenesis and across environmental gradients, rather than by nutrient limitations. In fact, our results showed that experimental N additions caused substantial acidification in soils from Hawai'i. These declines in pH were related to large decreases in soil biodiversity from tropical ecosystems in four continents. Moreover, the microbial activity did not change in response to long-term N and P additions. We concluded that environmental filtering drives the biodiversity of multiple soil organisms, and that the acidification effects associated with N additions can further create substantial undesired net negative effects on overall soil biodiversity in naturally tropical acid soils. This knowledge is integral for the understanding and management of soil biodiversity in tropical ecosystems globally.

Hawai'i↗

USGS2016

Detecting significant change in stream benthic macroinvertebrate communities in wilderness areas

A major challenge in the biological monitoring of stream ecosystems in protected wilderness areas is discerning whether temporal changes in community structure are significantly outside of a reference condition that represents natural or acceptable annual variation in population cycles. Otherwise sites could erroneously be classified as impaired. Long-term datasets are essential for understanding these trends, to ascertain whether any changes in community structure significantly beyond the reference condition are permanent shifts or with time move back to within previous limits. To this end, we searched for long-term (>8 years) quantitative data sets of macroinvertebrate communities in wadeable rivers collected by similar methods and time of year in protected wilderness areas with minimal anthropogenic disturbance. Four geographic areas with datasets that met these criteria in the USA were identified, namely: McLaughlin Nature Reserve in California (1 stream), Great Smoky Mountains National Park in Tennesse-North Carolina (14 streams), Wind River Wilderness Areas in Wyoming (3 streams) and Denali National Park and Preserve in Alaska (6 streams). Two statistical approaches were applied: Taxonomic Distinctness (TD) to describe changes in diversity over time and non-metric multidimensional scaling (MDS) to describe changes over time in community persistence (Jaccards Index) and community stability (Bray–Curtis Index). Control charts were used to determine if years in MDS plots were significantly outside a reference condition. For Hunting Creek, TD showed three years outside natural variation which could be attributed to severe hydrological events but years outside the natural-variation funnel at sites in other geographical areas were inconsistent and could not be explained by environmental variables. TD identified simulated severe pollutant events which caused the removal of entire invertebrate assemblages but not simulated water temperature shifts. Within a region, both MDS analyses typically identified similar years as exceeding reference condition variation, illustrating the utility of the approach for identifying wider spatial scale effects that influence more than one stream. MDS responded to both simulated water temperature stress and a pollutant event, and generally outlying years on MDS plots could be explained by environmental variables, particularly higher precipitation. Multivariate control charts successfully identified whether shifts in community structure identified by MDS were significant and whether the shift represented a press disturbance (long-term change) or a pulse disturbance. We consider a combination of TD and MDS with control charts to be a potentially powerful tool for determining years significantly outside of a reference condition variation.

Alaska, California, North Carolina, Tennesse, Wyom↗

USGS2003

Relations of biological indicators to nutrient data for lakes and streams in Pennsylvania and West Virginia, 1990-98

The Clean Water Action Plan of 1998 provides a blueprint for federal agencies to work with states, tribes, and other stakeholders to protect and restore the Nation's water resources. The plan includes an initiative that addresses the nutrient-enrichment problem of lakes and streams across the United States. The U.S. Environmental Protection Agency (USEPA) is working to set nutrient criteria by nationwide nutrient ecoregions that are an aggregation of the Omernik level III ecoregions. Because low levels of nutrients are necessary for healthy streams and elevated concentrations can cause algal blooms that deplete available oxygen and kill off aquatic organisms, criteria levels are to be set, in part, using the relation between chlorophyll a and concentrations of total nitrogen and total phosphorus. Data from Pennsylvania and West Virginia, collected between 1990 and 1998, were analyzed for relations between chlorophyll a , nutrients, and other explanatory variables. Both phytoplankton and periphyton chlorophyll a concentrations from lakes and streams were analyzed separately within each of the USEPA nutrient ecoregions located within the boundaries of the two states. These four nutrient ecoregions are VII (Mostly Glaciated Dairy), VIII (Nutrient Poor, Largely Glaciated Upper Midwest and Northeast), IX (Southeastern Temperate Forested Plains and Hills), and XI (Central and Eastern Forested Uplands). Phytoplankton chlorophyll a concentrations in lakes were related to total nitrogen, total phosphorus, Secchi depth, concentration of dissolved oxygen, pH, water temperature, and specific conductivity. In nutrient ecoregion VII, nutrients were not significant predictors of chlorophyll a concentrations. Total nitrogen, Secchi depth, and pH were significantly related to phytoplankton chlorophyll a concentrations in nutrient ecoregion IX. Lake periphyton chlorophyll a concentrations from nutrient ecoregion XI were related to total phosphorus rather than total nitrogen, Secchi depth, and pH. In all cases, Secchi depth was inversely related to the chlorophyll a concentrations in a lake. Nutrient ecoregion VIII had too few samples for any type of analysis. Streams within the different nutrient ecoregions had many variables that were significantly related to periphyton chlorophyll a concentrations. These variables consisted of total nitrogen, total phosphorus, drainage area, percent forest cover, several macroinvertebrate indices, pH, basin slope, total residue, total suspended solids, and water temperature. Nutrients were not significantly related to periphyton chlorophyll a in streams within nutrient ecoregions VII or IX but were in nutrient ecoregion XI. Drainage area, percent forest cover, and several invertebrate indices were significant variables in nutrient ecoregion VII. Percent forest cover and several invertebrate indices had a negative relation with chlorophyll a concentrations in these streams. Percent forest cover and basin slope had a negative effect on periphyton in nutrient ecoregion IX streams. Light availability was more critical to periphyton growth in streams than nutrients. Ecoregion XI had enough samples to do seasonal analyses. Summer-season periphyton chlorophyll a concentrations in nutrient ecoregion XI streams were positively related to total phosphorus and drainage area but negatively related to percent forest cover. Summer-season phytoplankton in streams was related to different variables within the same nutrient ecoregion. Both total nitrogen and total phosphorus were positively related with chlorophyll a concentrations as well as basin slope, total residue, and total suspended solids but negatively related to pH. The winter stream phytoplankton chlorophyll a concentrations were related to water temperature only.

Water-Resources Investigations Report↗

USGS2016

Observations of recruitment and colonization by tunicates and associated invertebrates using giant one-meter 2 recruitment plates at Woods Hole, Massachusetts

Large recruitment plates measuring 1 × 1 m were deployed over an 18-month period from September 2013 to March 2015 for the purpose of documenting recruitment and colonization processes of marine invertebrate species at Woods Hole, Massachusetts. Each side of two plates was subdivided into 16 subareas (25 × 25 cm), and an observational strategy was developed whereby, at approximately two-week intervals, a different subarea was cleaned. Using this approach, we were able to photographically document species recruitment and growth interactions. Water temperature records from the site show that steady warming and cooling between 3 and 20° C changed at a mean rate of 0.2 ° C d -1 . However, temperature changes during the coolest and warmest parts of the temperature cycle were highly variable. In 2014, between the first and last occurrence of 0° C, temperatures were ≤0° C 15 percent of the time, but in 2015 temperatures were ≤0° C 93 percent of the time. In 2014, between the first and last occurrence of 21° C, temperatures were ≥21° C 88 percent of the time, and this warm period correlated with the disappearance of the hydroid Ectopleura crocea , the solitary tunicates Ascidiella aspersa and Ciona intestinalis , and the 2013 generation of Botrylloides violaceus . In Woods Hole, large plates provided enough space to accommodate both fast- and slow-colonizing species, resulting in the establishment of a diverse assemblage that was observed over a long time period. The most successful colonizing species had relatively long reproductive and recruitment periods, grew rapidly, repelled settlement onto their surfaces by larvae of any species, defended themselves against overgrowth by any species, overwintered, and lived a long time. Of the three dominant species observed in this study, the colonial tunicates Didemnum vexillum and Botrylloides violaceus had these qualities; the encrusting colonial bryozoan Schizoporella unicornis had all but one, it grew more slowly than the others. Barnacles constituted the only biological substrate that was effectively colonized by other species, both by larval recruitment and overgrowth. In Woods Hole, after a substrate had become fully colonized, there was very little opportunity for new recruitment or colony growth until new substrate opened after the death of colonies and individuals and the disappearance of biogenic structures such as amphipod tubes. An understanding of colonization processes utilized by invasive species allows prediction of their potential effects on ecosystems in areas where they are not yet present.

Massachusetts↗

USGS2017

Asynchrony in craniomandibular development and growth in Enhydra lutris nereis (Carnivora: Mustelidae): Are southern sea otters born to bite?

Weaning represents a major ontogenetic dietary shift in southern sea otters ( Enhydra lutris nereis ), as juveniles must transition from depending on mother’s milk to independently processing hard-shelled invertebrates. When the skulls of juveniles have reached sufficient maturity to transition to a durophagous diet remains to be investigated. Here, we conducted a comprehensive analysis of skull development and growth and sexual dimorphism using geometric morphometric approaches in 204 southern sea otter skulls. We found that southern sea otters of both sexes exhibit dramatic changes in cranial and mandibular shape and size over ontogeny. Although the majority of these changes occur in the pup stage, full development and growth of the skull does not occur until well after weaning. We hypothesize that the slower maturation of the crania of newly weaned juveniles serves as a handicap by constraining jaw adductor muscle size, biting ability and feeding on hard-shelled prey. In our analysis of sexual dimorphism, we found significant sexual shape and size dimorphism in adult craniomandibular morphology that arose through differences in developmental and growth rates and duration. We postulate that males are selected to attain mature crania faster to presumably reach adult biting ability sooner, gaining a competitive advantage in obtaining food and in male–male agonistic interactions.

Biological Journal of the Linnean Society↗