Geology topics

Allison H. Roy

Publications and source records attributed to Allison H. Roy.

At least 55 records · Page 3Linked to original sources

USGS2022

Urbanization and stream ecology: Moving the bar on multidisciplinary solutions to wicked urban stream problems

Decades of research on the effects of urbanization on stream ecology have shown that urban stream problems are inherently wicked. These problems are wicked in the sense that they are difficult to solve because information is incomplete, changing, or conflicting and because finding potential solutions often requires input from stakeholders who can have conflicting and competing values. The 5 th Symposium on Urbanization and Stream Ecology (SUSE5) in February 2020 brought together diverse perspectives from scientists, managers, practitioners, and local communities. Participants at SUSE5 discussed the state of the science in urban stream ecology and worked through in-depth case studies in teams to tackle complex real-world problems in urban stream management. The papers in this special series on urbanization and stream ecology include empirical research studies and synthesis papers sparked by discussions at SUSE5 and advance multidisciplinary solutions to wicked urban stream problems.

Freshwater Science↗

USGS2022

Stream macroinvertebrate reintroductions: A cautionary approach for restored urban streams

Macroinvertebrate assemblages often remain depauperate in physically restored urban streams despite efforts to improve habitat conditions and increase species abundance and diversity. The lack of biological recovery may be due to a lack of a natural, nearby source of colonists, and this has inspired researchers and practitioners to reintroduce macroinvertebrates in otherwise restored urban streams to jump start the recovery process. However, without standardized guidelines that describe reintroduction best practices, some reintroduction programs may create additional problems (e.g., disease spread, genetic homogenization, population loss). To reduce these risks and limit a potential waste of resources, a cautionary approach is warranted. In this paper we summarize current stream reintroduction knowledge and detail best practices for aquatic macroinvertebrate reintroduction in restored urban streams. We provide criteria that managers can use to determine whether reintroduction is appropriate and demonstrate how researchers can use reintroduction as a tool to test hypotheses regarding factors limiting recolonization. We provide guidance for how to set clear reintroduction goals, select donor sites, determine the number of organisms required, establish reintroduction frequency and timing, and overcome challenges associated with monitoring. This framework can help managers create more successful reintroduction programs that can benefit urban stream restoration.

Freshwater Science↗

USGS2022

Evaluation of host fishes for the Brook Floater (Alasmidonta varicosa) from populations in Massachusetts and Maine, USA

The Brook Floater ( Alasmidonta varicosa ) mussel is globally vulnerable and has disappeared from much of its historical range. Information on Brook Floater host fish use is needed for ecological and conservation purposes, but previous laboratory studies provide conflicting results. We evaluated host fish use by Brook Floater from populations in Massachusetts and Maine, USA. We conducted three experiments using a total of 10 fish species from six families, and we estimated glochidial attachment rate and juvenile metamorphosis rate. Across fish species, attachment ranged from 51.0% to 84.6% and metamorphosis ranged from 4.9% to 80.9%. Fish species and inoculation density (viable glochidia/mL) only weakly predicted attachment, and the number of glochidia that attached to fish did not affect metamorphosis rate. Juvenile metamorphosis was successful on all fish species tested, supporting evidence that Brook Floater is a host generalist. Fish species was an important factor in predicting metamorphosis rates in all experiments. The highest metamorphosis was on Slimy Sculpin ( Cottus cognatus ) (80.9% ± 2.6 SD) and Brook Trout ( Salvelinus fontinalis ) (71.6%), but metamorphosis on Brook Trout varied according to source and was lowest on hatchery-raised fish (12.8% ± 0.3 SD). These data contribute to our understanding of the life history of Brook Floater by identifying potential host fishes, and our results can inform propagation efforts for this species in the northeastern USA.

Maine, Massachusetts↗

USGS2021

Homeowners’ willingness to adopt environmentally beneficial landscape practices in an urbanizing watershed

Streams in urbanizing watersheds often experience low flows in summer due to increased water use for residential landscaping and decreased base flow as impervious land cover limits aquifer recharge. Environmentally beneficial landscape practices that save water and infiltrate runoff have the potential to provide multiple ecological benefits including reducing stress on urban streams, but can face opposition by local homeowners. Thus, this study explored attitudes toward landscape water conservation including the barriers and motivations that exist to adoption of water conserving landscape practices by residents in the Ipswich River watershed north of Boston, Massachusetts that experiences seasonal water shortages. The study used a mail-out and on-line survey with images of different water conserving landscape practices (including rain gardens and native plantings) and questions about homeowners’ watering practices, likelihood of adopting these landscape practices, and attitudes towards environmental issues in the region, including existing water policies to restrict use. The results showed that residents (n=265) were aware of existing water shortages and supportive of water conservation policies. Their willingness to adopt water conserving landscape practices was influenced by aesthetic preference with more support for practices that appeared neat rather than those that appeared unkempt. Barriers to residential adoption of these landscape practices included concern about disease-carrying pests and the perceived cost of landscape change. Knowledge about the environment, as operationalized by membership in a local watershed association, as well as educational attainment and income were significant variables in predicting aesthetic preferences and willingness to adopt landscape practices. Promoting widespread adoption of water conserving landscape practices will require local community support and educational initiatives about the multiple-benefits of these practices, including potential long-term cost savings for homeowners. Residential landscape design and management, however, is only part of overarching policy changes that must be implemented to address water conservation in urbanizing watersheds.

Massachusetts↗

USGS2021

Hydrology of annual winter water level drawdown regimes in recreational lakes of Massachusetts, United States

Annual winter water level drawdown (WD) is a common lake management strategy to maintain recreational value by controlling nuisance macrophytes and preventing ice damage to shoreline infrastructure in lakes of the northeastern United States. The state of Massachusetts provides general guidelines for lake managers to implement and practice WDs. However, WD management reporting is not required and as such empirical water level records are scarce, making it difficult to assess guideline adherence and link these management actions to littoral habitat conditions. We monitored water levels bihourly in 18 lakes with ongoing WD regimes and 3 non-drawdown lakes over 3–4 yr. Our results show an interlake drawdown magnitude gradient of 0.07–2.66 m with intralake consistency across years. Corresponding WD magnitudes generated exposure of 1.3–37.6% for entire lakebeds and 9.2–71.1% for littoral zones. WD durations averaged 171 d and ranged widely from 5 to 246 d. Longer recession and refill phase durations and faster recession rates were moderately to strongly correlated with drawdown magnitudes. WDs were predominantly initiated prior to the state of Massachusetts 1 November starting guideline (83.1%) and refilled to summer reference levels after the recommended date of 1 April (70.6%). To minimize ecological impacts while still meeting recreational goals, WD performance guidelines may require a more fine-scale approach that integrates local hydrogeomorphic features and the presence of WD-sensitive littoral biotic assemblages. However, climate change model projections of warmer and wetter winters in the Northeast indicate increasing uncertainty for WD as an effective and worthwhile macrophyte control tool.

Massachusetts↗

USGS2021

Daily patterns of river herring (Alosa spp.) spawning migrations: Environmental drivers and variation among coastal streams in Massachusetts

The timing of life history events in many plants and animals depends on the seasonal fluctuations of specific environmental conditions. Climate change is altering environmental regimes and disrupting natural cycles and patterns across communities. Anadromous fishes that migrate between marine and freshwater habitats to spawn are particularly sensitive to shifting environmental conditions and thus are vulnerable to the effects of climate change. However, for many anadromous fish species the specific environmental mechanisms driving migration and spawning patterns are not well understood. In this study, we investigated the upstream spawning migrations of river herring Alosa spp. in 12 coastal Massachusetts streams. By analyzing long-term data sets (8–28 years) of daily fish counts, we determined the local influence of environmental factors on daily migration patterns and compared seasonal run dynamics and environmental regimes among streams. Our results suggest that water temperature was the most consistent predictor of both daily river herring presence–absence and abundance during migration. We found inconsistent effects of streamflow and lunar phase, likely due to the anthropogenic manipulation of flow and connectivity in different systems. Geographic patterns in run dynamics and thermal regimes suggest that the more northerly runs in this region are relatively vulnerable to climate change due to migration occurring later in the spring season, at warmer water temperatures that approach thermal maxima, and during a narrower temporal window compared to southern runs. The phenology of river herring and their reliance on seasonal temperature patterns indicate that populations of these species may benefit from management practices that reduce within-stream anthropogenic water temperature manipulations and maintain coolwater thermal refugia.

Massachusetts↗

USGS2021

Annual winter water-level drawdowns influence physical habitat structure and macrophytes in Massachusetts, USA, lakes

Annual wintertime water-level drawdowns are a common management strategy in recreational lakes; however, few studies have estimated their relative impact on lake littoral habitat among a set of typically co-occurring anthropogenic stressors including lakeshore development and herbicide application. Within 21 Massachusetts, USA lakes that represented a drawdown magnitude gradient (0.07–2.26 m), we assessed depth-specific littoral habitat (coarse wood, sediment, macrophytes) at two sites adjacent to forested or developed shorelines. Using generalized linear mixed models, we found coarse wood abundance and branching complexity was not correlated with drawdown magnitude but was primarily explained by the presence of lakeshore development. Drawdown magnitude was negatively correlated with silt cover and positively correlated with coarse substrate cover, with effects further varying by depth (0.5 m vs. 1 m). Macrophyte biomass and biovolume were negatively correlated with drawdown magnitude with effects also varying by depth for biomass. Macrophyte taxa with annual longevity strategies (e.g., Najas flexilis ) and amphibious growth forms increased in biomass proportions with drawdown magnitude. Distance-based redundancy analyses suggested macrophyte taxa composition was driven by drawdown magnitude, coarse substrate, alkalinity, water transparency, and herbicide use. These results suggest the importance of water quality and depth on macrophyte assemblage responses to winter drawdowns and the potential to develop drawdown-tolerant macrophyte assemblages. Altogether, understanding the unique impacts of anthropogenic stressors on littoral zone habitat across heterogeneous environmental lake conditions can help minimize impacts to lake ecological integrity while maintaining recreational value.

Massachusetts↗

USGS2021

Feeling the squeeze: Adult run size and habitat availability limit juvenile river herring densities in lakes

Maximum densities of juvenile river herring (Alewife Alosa pseudoharengus and Blueback Herring A. aestivalis ) vary among freshwater lakes, likely due to densities of adult spawners. Differences in habitat availability and lake water quality may also contribute to variation in juvenile river herring productivity between populations, yet these relationships have not been tested across a large geographic scope. In this study we investigated relationships between juvenile river herring densities and (1) spawning adult river herring densities, (2) lake habitat availability, and (3) lake water quality in 29 freshwater lakes in the northeastern USA. Purse seines were used at night to sample juvenile river herring monthly in June–August 2014 and 2015, with concurrent collection of lake-specific physical (e.g., lake surface area, mean depth, depth to thermocline), chemical (e.g., nitrogen, phosphorus, dissolved organic carbon [DOC]), and biological (chlorophyll a , adult spawning density) data. Spawning adult density (number of adults per surface area of lake) explained 66.6% of the variation in juvenile densities using a generalized additive model. Juvenile densities increased with increasing adult density, peaking at roughly 1,000 adults/ha, and then declined at higher adult densities, suggesting a limit to carrying capacity in juvenile production. Linear mixed-effects models revealed that differences in water quality and habitat across lakes explained additional variation in juvenile densities. Specifically, DOC was negatively related to juvenile densities, suggesting that DOC limits the amount of suitable, well-oxygenated epilimnion habitat available to juvenile river herring in late summer. Our results can be used to help understand expected juvenile production based on adult density within a lake, to inform expectations about juvenile growth and survival, and to understand the mechanisms for how changes in habitat availability and water quality affect river herring populations.

Connecticut, Maine, Massachusetts, New Hampshire, ↗

USGS2021

Impacts of small dams on stream temperature

Small, surface-release dams are ubiquitous features of the landscape that typically slow water flow and decrease canopy cover through impounded reaches, potentially increasing stream temperatures. However, reported effects of small dams on water temperature are variable, likely due to differences in landscape and dam characteristics. To quantify the range of thermal effects of small dams, we deployed continuous temperature loggers for one to four years at 30 dam sites across a range of environmental settings throughout Massachusetts (USA). Most dams (67%) warmed downstream waters, with August mean temperatures 0.20–5.25 °C higher than upstream. Downstream temperatures cooled with increased distance from the dam at 68% of sites, such that the warmest temperatures were observed closest to the dam. Where there was both a significant downstream warming effect and cooling pattern (seven sites), elevated temperatures persisted for an average of 1.31 km downstream of the dam. Dams with impoundments that caused the greatest relative widening of the stream channel and those on coldwater streams had the most warming, while streams with short dams in forested watersheds cooled most quickly downstream of the dam. Flow had a homogenizing effect on water temperatures at over half of the sites, whereby summer thermal impacts were more pronounced (e.g., more warming, faster cooling rates) under periods of lower flows. Downstream warming may reduce habitat for coldwater fishes and invertebrates, particularly where dams shift coldwater/coolwater habitat to warmwater. These results suggest that dam removal may mitigate elevated stream temperatures and increase ecosystem resilience in the face of a changing climate via restoration of critical coldwater habitats.

Massachusetts↗

USGS2020

Understanding effects of small dams on benthic metabolism and primary production in temperate forested streams

Dams can alter the chemical and physical conditions of downstream environments by increasing stream temperatures, altering nutrient limitation, reducing flow variability, and reducing fine sediment deposition. However, little is known about how fundamental stream ecosystem processes like productivity and respiration respond to dams. Nutrient diffusing substrates were installed in three dam streams and three control streams to evaluate the effect of dams on benthic gross primary productivity (GPP), respiration (R), and chlorophyll α production. Dam streams were an average of 5.6 °C warmer than control streams but GPP, R and chlorophyll α were not different between control and dam streams. Phosphorus enrichment increased heterotrophic R relative to controls (~1.8×) but not autotrophic GPP, R or chlorophyll α. Stream nutrient concentrations and nutrient limitation of heterotrophic R were similar in dam and control streams, suggesting that the dams had limited effects on nutrient transport downstream. Autotrophic GPP, R and chlorophyll α were limited by light and varied within and across streams, potentially masking our ability to detect differences caused solely by dams. Dams may alter stream ecosystem function but consideration of other factors associated with and independent of dams is critical for predicting ecosystem responses to dams.

Fundamental and Applied Limnology↗

USGS2019

Evaluating the effects of barriers on Slimy Sculpin movement and population connectivity using novel sibship-based and traditional genetic metrics

Population genetics-based approaches can provide robust and cost-effective ways to assess the effects of potential barriers, including dams and road-stream crossings, on the passage and population connectivity of aquatic organisms. Determining the best way to apply and modify genetic tools for different species and situations is essential for making these genetics-based approaches broadly applicable to fisheries and aquatic habitat management. Here, we used multiple genetic approaches to assess the movement and population structure of Slimy Sculpin Cottus cognatus at two road-stream crossings in Michigan and one dam in Massachusetts, USA. We captured and genotyped individual sculpin and assessed movement and population connectivity by using (1) a sibship-based approach, where the presence and proportional distribution of siblings on either side of a barrier indicates population connectivity and the possible direction of movement (i.e., presumed movement from higher to lower proportions), and (2) two Bayesian genetic assignment approaches (STRUCTURE and BayesAss) to identify migrants across potential barriers based on individual population assignment probabilities. We also used traditional genetic metrics to assess within-population genetic variation and among-population genetic divergence. At all three locations, we found evidence for sculpin movement across the potential barrier based on sibship reconstruction, but small family sizes limited the ability of this approach to provide robust estimates of the rate and direction of movement. At two sites, a lack of genetic differentiation between above- and below-barrier populations limited the effectiveness of the genetic assignment methods for identifying possible migrants. At the third site, reduced upstream allelic diversity and effective number of breeders resulted in high genetic differentiation (FST) between above- and below-barrier populations, and both sibship and genetic assignment methods provided strong evidence of limited connectivity and bias against upstream movement. Overall, combining approaches and metrics may help overcome the limitations of any one method and maximize the value of datasets for genetics-based monitoring and assessment.

Massachusetts, Michigan↗

USGS2019

Effects of stream temperature and substrate type on emergence patterns of Plecoptera and Trichoptera from northeastern United States headwater streams

The timing and spatial distribution of aquatic insect emergence is linked to the abiotic and biotic environment in streams. Studies of aquatic insect emergence are needed to generate baseline data to identify potential shifts in phenology and habitat-related emergence with global change. The purpose of this study was to 1) compare the timing of Plecoptera (stonefly) species emergence between two streams with different thermal regimes and 2) characterize the distribution of emerging Plecoptera and Trichoptera (caddisflies) from wood, rock, gravel, and sand substrates in five forested, headwater streams. Emergence timing and duration varied among Plecoptera species, with Ostrocerca albidipennis (Walker) (Plecoptera: Nemouridae) emerging only in May and four species in the genus Leuctra (Plecoptera: Leuctridae) collectively emerging throughout the summer (May to September). We observed earlier emergence of Amphinemura nigritta (Provancher) (Plecoptera: Nemouridae) and a longer total emergence period for Leuctra ferruginea (Walker) (Plecoptera: Leuctridae) in the stream with ~1.5°C warmer temperatures, which suggested that some insects may experience phenological shifts in streams with subtle differences in temperature. The abundance of plecopteran and trichopteran taxa emerging from wood was generally greater than for gravel or sand, and sand was the least preferred emergence substrate. The results suggest that human actions that decrease large wood and increase fine sedimentation may decrease habitat quality for many insect larvae and limit preferred emergence substrates.

Massachusetts↗

USGS2019

Annual winter water level drawdowns limit shallow-water mussel densities in small lakes

Regulated water level fluctuations alter the physical, chemical, and biological environments in lakes. However, few studies have measured the effects of repeated annual winter drawdowns on freshwater mussel populations (Bivalvia: Unionida), and it is unknown whether drawdowns permanently constrain mussel populations to deeper depths or are resilient to the annual disturbance. We quantified mussel densities during normal water levels and their mortality after the initiation of drawdown in lakes with annual winter (December–March) water level drawdown regimes that have existed for several decades. We used systematic quadrat sampling and visual snorkel surveys to estimate the number of live mussels at the surface and buried, and shell length in six drawdown and three control lakes at exposed (0.5-m) and unexposed (1-m) depths during winter drawdown. We also estimated mortality of mussels along the exposed lakebed for nine drawdown lakes. Study lakes were dominated by Elliptio complanata and Pyganodon cataracta . During normal water levels, mussel densities were much lower in drawdown lakes than control lakes at 0.5-m depths. When mussels were present in drawdown lakes at 0.5-m depths, they were often burrowed in the substrate and smaller than buried mussels in control lakes. At unexposed 1-m depths, mussel densities were primarily explained by geographic region (western versus central Massachusetts), and found higher densities in drawdown lakes compared to control lakes. Mussel mortality after a single drawdown event in nine drawdown lakes was not correlated with drawdown magnitude or rate. Concordance of shell length-frequency distributions between dead and buried living mussels in drawdown lakes suggests annual mortality of colonising individuals, which are typically small and presumably of young cohorts. Annual winter drawdowns still limit densities of E. complanata and P. cataracta in shallow-water habitats in the following autumn (September–October) after 4–5 months of potential recovery, and hence constrain their distribution in lakes exposed to drawdowns. The development of sustainable water level management practices will be essential to minimise impacts to native mussel populations.

Massachusetts↗

USGS2019

Larger body size and earlier run timing increase alewife reproductive success in a whole lake experiment

Environmental conditions can influence biological characteristics like phenology and body size with important consequences for organismal fitness. Examining these fitness consequences under natural conditions through genetic pedigree reconstruction offers a lens into potential population responses to changing environments. Over three years (2013-2015), we introduced adult alewife (Alosa pseudoharengus), anadromous, iteroparous clupeids, into one Massachusetts (USA) lake to complete the first detailed examination of this species’ mating system and assess relationships between body size, reproductive timing, and seasonal reproductive success. We reconstructed pedigrees using 15 microsatellites and genotypes from all possible parents and samples of naturally produced offspring within four months of hatching. Within each of the three study years, spawning adults had multiple mates and spawned multiple times. Larger females that arrived earlier had higher reproductive success. Declining body size and altered migration timing over time, through an influence on reproductive success, can influence population vital rates and productivity.

Massachusetts↗

USGS2018

Precision and relative effectiveness of a purse seine for sampling age-0 river herring in lakes

Stock assessments for anadromous river herring, collectively Alewife Alosa pseudoharengus and Blueback Herring A. aestivalis , lack adequate demographic information, particularly with respect to early life stages. Although sampling adult river herring is increasingly common throughout their range, currently no standardized, field‐based, analytical methods exist for estimating juvenile abundance in freshwater lakes. The objective of this research was to evaluate the relative effectiveness and sampling precision of a purse seine for estimating densities of age‐0 river herring in freshwater lakes. We used a purse seine to sample age‐0 river herring in June–September 2015 and June–July 2016 in 16 coastal freshwater lakes in the northeastern USA. Sampling effort varied from two seine hauls to more than 50 seine hauls per lake. Catch rates were highest in June and July, and sampling precision was maximized in July. Sampling at night (versus day) in open water (versus littoral areas) was most effective for capturing newly hatched larvae and juveniles up to ca. 100 mm TL. Bootstrap simulation results indicated that sampling precision of CPUE estimates increased with sampling effort, and there was a clear threshold beyond which increased effort resulted in negligible increases in precision. The effort required to produce precise CPUE estimates, as determined by the CV, was dependent on lake size; river herring densities could be estimated with up to 10 purse‐seine hauls (one‐two nights) in a small lake (<50 ha) and 15–20 hauls (two‐three nights) in a large lake (>50 ha). Fish collection techniques using a purse seine as described in this paper are likely to be effective for estimating recruit abundance of river herring in freshwater lakes across their range.

North American Journal of Fisheries Management↗

USGS2018

Impacts of tidal road-stream crossings on aquatic organism passage

ivers and streams are highly vulnerable to fragmentation from roads due to their prevalence in the landscape. Road-stream crossings are far more numerous than other anthropogenic barriers such as dams; these crossing structures (culverts, bridges, fords, and tide gates) have been demonstrated to impede the passage of aquatic organisms. However, road-stream crossings vary widely in the extent to which they serve as a barrier. It is important to identify barrier severity to facilitate prioritization of restoration activities, since proactively addressing all structures is not feasible. In 2015 the North Atlantic Landscape Conservation Collaborative (LCC) funded a project managed by the North Atlantic Aquatic Connectivity Cooperative (NAACC) to develop a unified protocol for assessing aquatic road-stream crossings focusing on aquatic connectivity. The NAACC relied on rapid field-based assessments, which have been shown to be a useful tool for gathering information necessary for prioritization. However, the rapid assessment protocol developed from the NAACC initiative is not applicable to tidal crossings as it does not address two-directional flow, daily water depth fluctuations, or many of the species likely present in coastal habitats. The goal of this report is to provide the background necessary to create guidelines and rapid assessment tools for assessing risk posed to aquatic organism passage at tidal crossings. To accomplish these goals, this report identifies species present in tidally influenced coastal wetlands, the unique traits they may display that puts them at risk for detrimental impact from impeded passage, and passage threats unique to tidal crossings that are not addressed by protocols designed for non-tidal systems. Species lists were compiled through literature reviews and discussions with regional researchers and managers familiar with coastal ecosystems or fish passage concerns. Life history traits, environmental sensitivities, and movement patterns for each species were compiled to build a database that can be queried to identify species that are highly vulnerable to impeded passage at tidal crossings (Available at: https://umass.box.com/s/w5mhokxjxshyxmr7si2v0gzcypcitu9d ). These risk factors for species, combined with passage threats associated with specific crossing characteristics are discussed in this report. The species list is thorough enough to provide a baseline summary of the types of threats experienced by aquatic organisms at tidal road-stream crossings, but it is not exhaustive. Unique ecosystems, species assemblages, management goals, and prioritization models may require different approaches and solutions. Thus, care must be taken to ensure that assessment tools are appropriate to a project’s target species, habitats, and scale.

Cooperator Science Series↗

USGS2018

Brook Floater rapid assessment monitoring protocol

The Brook Floater ( Alasmidonta varicosa ) is a small (<100 mm), stream dwelling freshwater mussel (Family: Unionidae) from Atlantic Slope drainages in the eastern U.S. (Nedeau 2008). Brook Floater have dramatically contracted in distribution over recent decades, and there is limited evidence of recruitment in most locations, despite minimal effort to document population status (Wicklow et al., 2017). Brook Floater is listed as a Species of Greatest Conservation Need (SGCN) throughout its range in the United States (state-listed as imperiled or critically imperiled in all 15 states), has been extirpated from two states (Rhode Island and Delaware) and was recently petitioned for Federal listing in 2011 (Wicklow et al. 2017). Currently, there is a U.S. Fish and Wildlife (USFWS) Species Status Assessment underway to determine if federal listing under the Endangered Species Act is warranted. Brook Floater is also listed as a species of special concern in Canada, the northern extent of its range. In 2016, a state wildlife grant was awarded to develop range-wide conservation initiatives and strategies, including the development of rapid assessment and long-term monitoring techniques, in addition to developing conservation strategies to improve its probability of persistence in the future. The purpose of this protocol is to describe and facilitate a rapid approach to estimating Brook Floater occupancy to better understand the factors that influence Brook Floater distribution. Occupancy estimation approaches allow for estimation of species occupancy (; percent area occupied) within some scale of interest (for our purposes, the watershed), while simultaneously estimating species detection probability (p; the probability of finding an organism, if present). Occupancy estimation has been used with many wildlife taxa and is essential for understanding the presence or absence of wildlife in a particular area while accounting for imperfect detection (i.e., p<1; MacKenzie et al. 2004, Shea et al. 2013, Wisniewski et al. 2013, Pandolfo et al. 2016, MacKenzie 2016). This approach does not rely on existing information about species presence or absence to select sites. Occupancy estimation operates on a robust probabilistic framework of randomly selected sites to infer what proportion of sites are occupied. Occupancy estimation also incorporates imperfect detection (p <1; i.e., animals are cryptic and elusive; observers have varying experience searching, etc.; MacKenzie et al. 2003). For example, two mussel species that occupy a site might have two very different detection histories, as determined by revisiting a site and using the same methods on repeated visits to find both species. See hypothetical results here: Visits 1 2 3 4 5 Mussel species A 1 1 1 0 1 Mussel species B 0 0 0 1 0 (1 = detected, 0=not detected) Both of these mussel species occupy this site, yet Mussel A was detected in 4 out of 5 visits (high p) and Mussel B was detected in 1 out of 5 visits (low p) with the methods used to survey this site. Covariates may explain differences in detection between species or visits. Organisms may be: 1) present and not observed, 2) present and unavailable for capture (i.e., buried in sediment), or 3) not present at the site. Occupancy estimation uses repeated visits of randomly selected sites to build species detection histories (i.e., 1, 0, 1) to simultaneously estimate occupancy () and p. Typically, repeated visits are discrete sampling events and are more time consuming because each site requires >3 separate visits. In our rapid assessment protocol, we use multiple independent observers searching longitudinal lanes to estimate detection in a single site visit as opposed to multiple discrete visits. Below are hypothetical results of occupancy by observer: Independent Observers 1 2 3 4 5 Mussel species A 1 1 0 1 1 Mussel species B 1 0 0 1 0 (1 = detected, 0=not detected) Objectives: The objectives of this rapid assessment survey approach are to guide collection of data that can be used to: A. Estimate the occupancy of Brook Floater within watersheds. B. Estimate the effects of reach- and watershed-scale habitat features on Brook Floater occurrence. C. Understand how survey covariates (e.g., surveyor experience) influence detection of Brook Floater. While this protocol explicitly targets collection of Brook Floater, it is likely that the methods can be adapted for occupancy surveys of other stream-dwelling freshwater mussel species.

Cooperator Science Series↗

USGS2017

Ecological impacts of winter water level drawdowns on lake littoral zones: A review

Freshwater littoral zones harbor diverse ecological communities and serve numerous ecosystem functions that are controlled, in part, by natural water level fluctuations. However, human alteration of lake hydrologic regimes beyond natural fluctuations threaten littoral zone ecological integrity. One type of hydrologic alteration in lakes is winter water level drawdowns, which are frequently employed for hydropower, flood control, and macrophyte control, among other purposes. Here, we synthesize the abiotic and biotic responses to annual and novel winter water level drawdowns in littoral zones of lakes and reservoirs. The dewatering, freezing, and increased erosion of exposed lakebeds drive changes in the littoral zone. Shoreline-specific physicochemical conditions such as littoral slope and shoreline exposure further induce modifications. Loss of fine sediment decreases nutrient availability over time, but desiccation may promote a temporary nutrient pulse upon re-inundation. Annual winter drawdowns can decrease taxonomic richness of macrophytes and benthic invertebrates and shift assemblage composition to favor taxa with r-selected life history strategies and with functional traits resistant to direct and indirect drawdown effects. Fish assemblages, though less directly affected by winter drawdowns (except where there is critically low dissolved oxygen), experience negative effects via indirect pathways like decreased food resources and spawning habitat. We identify eight general research gaps to guide future research that could improve our understanding about the complex effects of winter drawdowns on littoral zone ecology.

Aquatic Sciences↗