Understanding effects of changes in land use, environmental parameters, habitat characteristics on the Great Basin aquatic invertebrates using ecological stoichiometric theory

Many freshwater ecosystems in the Great Basin have undergone dramatic alteration over the past decades due to groundwater withdrawal, water diversion and changes in land use. These changes have affected benthic food web dynamics by altering the availability of chemical key elements for primary and secondary producers, by loss of biodiversity and extinction of endemic species. However, only few studies are available that addresses the link between changes in land use, habitat characteristics and its effects on benthic macroinvertebrates (BMI) communities comprehensively and little attention has been given to integrating physiochemical aspects to link ecosystem functions. This dissertation analyzes the link between BMI communities and their habitat characteristics in the Walker River and in diverse spring ecosystems in the Great Basin by using ecological stoichiometry and secondary production assessment as tools and provides a knowledge base that can be used in stream and spring protection and restoration, respectively. The dissertation includes three separate studies that are organized into three chapters that are being prepared for peer reviewed publication. In the first study, multiple regression analysis followed by corrected Akaike\u27s Information Criterion (AICc) was used to determine predictor variable(s) that best explains the elemental composition of basal food resources (seston and periphyton) and BMI along an elevation gradient and land use type in the Walker River in California and Nevada. The elemental composition of basal food resources are best explained by land use and associated differences in soluble reactive phosphorus (SRP),dissolved organic carbon (DOC), and stream water nitrogen (N): phosphorus (P) ratios. In contrast, BMI elemental stoichiometry was correlated to taxonomic identity and body mass. Therefore, both parameters should always be taken into account when addressing land use effects on resource-consumer stoichiometry. Consumer-resource elemental imbalances in this study were less pronounced than those reported from the nutrient-poor streams. However, high spatial and temporal variability in food source elemental composition obscured clear spatial pattern in elemental imbalances between nutrient-poor upstream sites and nutrient-rich downstream sites. Results from this study suggest that applying ecological stoichiometry is a useful tool to better understand the elemental dynamics of food components particularly in Great Basin watersheds with highly variable physiochemical conditions that such as Walker River. The second project analyzed the link between the ecological health of BMI communities and habitat characteristics along the Walker River. Biotic indices indicated a shift in BMI communities towards species-poor assemblages with few dominant taxa from upstream to downstream parts of Walker River. Further, the Hilsenhoff Biotic Index (HIB) indicated an increase in the dominance of pollutant-tolerant taxa at downstream parts of Walker River. These shifts in the BMI community composition were related to spatial changes in substrate size, stream width, stream temperature, SRP, and Total Suspended Solids (TSS). Further, secondary production of Baetis mayflies, one of the most common genera in Walker River, was estimated between two sites differing in water quality to assess effects of nutrient enrichment on Baetis density, biomass and secondary production. Although mean individual body mass of Baetis was lower at the nutrient enriched site, secondary production was higher most likely due to the combination of higher growth rates and higher densities. Based on these results I recommend that factors influencing nutrients, discharge, and stream temperature are the most important parameter to consider Walker River restoration.Further, the results from this study can be used to assess the success of stream restoration by documenting changes in BMI communities and secondary production. In the third study, spring-dwelling snails and their potential food source were collected from twenty-three springs from the eastern part of the Great Basin to provide a basic understanding about the link of the snail\u27s elemental composition to taxonomy, basal food resources and habitat characteristics. The results showed that body% phosphorus (P) of snails was highly variable among the four major snail families whereas body% nitrogen (N) and % carbon (C) varied less. Differences in the body elemental composition among the same species collected from multiple springs indicate that aquatic snails can deviate from strict homeostasis. The body %P content in snails belonging to Pyrgulopsis collected from warm springs (water temperature \u3e 20ºC)was significantly lower compared to those collected from cold springs. Further, elemental imbalances between snails and there potential food sources were significantly higher in warm springs compared to cold springs. These results indicating that water temperature is an important factor that constraints food web dynamics in long-term stable ecosystems, such as springs. Basic understanding about food web dynamics in Great Basin springs is not only important to determine further consequences on the nutrient cycling in ecosystems with strong temperature gradients. It can also be used to predict consequences of human alterations on the food web dynamic in these long-term stable ecosystems

Density data for Lake Ontario benthic invertebrate assemblages from 1964 to 2018

Benthic invertebrates are important trophic links in aquatic food webs and serve as useful bioindicators of environmental conditions because their responses integrate the effects of both water and sediment qualities. However, long-term data sets for benthic invertebrate assemblages across broad geographic areas are rare and, even if collected, historic data sets are often not readily accessible. This data set provides densities of benthic macroinvertebrates for all taxa collected during lake-wide surveys in Lake Ontario, a Laurentian Great Lake, from 1964 to 2018. This information resulted from surveys funded by the governments of the United States and Canada to investigate the status and changes of Lake Ontario benthic community. Of the 13 lake-wide benthic surveys conducted in Lake Ontario over the course of 54 yr, we were able to acquire taxonomic data to the species level for 11 of the surveys and data to the group level for the other two surveys. Density data are provided for taxa representing the Annelida, Arthropoda, Mollusca, Cnidaria, Nemertea, and Platyhelminthes phyla. Univariate and multivariate analyses revealed that the compositional structure of Lake Ontario invertebrate assemblages differed markedly by depth and were also significantly altered by the Dreissena spp. invasion in early 1990s. The introduction of invasive dreissenids has changed the community historically dominated by Diporeia, Oligochaeta, and Sphaeriidae, to a community dominated by quagga mussels and Oligochaeta. Considering the rarity of long-term benthic data of high taxonomic resolution in lake ecosystems, this data set could be useful to explore broader aspects of ecological theory, including effects of different environmental factors and invasive species on community organization, functional and phylogenetic diversity, and spatial scale of variation in community structure. The data set could also be useful for studies on individual species including abundance and distribution, species co-occurrence, and how the patterns of dominance and rarity change over space and time. Use of this data set for academic or educational purposes is encouraged as long as the data source is properly cited using the title of this Data Paper, the names of the authors, the year of publication, the journal name, and the article number

Conservation of freshwater bivalves at the global scale: diversity, threats and research needs

Bivalves are ubiquitous members of freshwater ecosystems and responsible for important functions and services. The present paper revises freshwater bivalve diversity, conservation status and threats at the global scale and discusses future research needs and management actions. The diversity patterns are uneven across the globe with hotspots in the interior basin in the United States of America (USA), Central America, Indian subcontinent and Southeast Asia. Freshwater bivalves are affected by multiple threats that vary across the globe; however, pollution and natural system (habitat) modifications being consistently found as the most impacting. Freshwater bivalves are among the most threatened groups in the world with 40% of the species being near threatened, threatened or extinct, and among them the order Unionida is the most endangered. We suggest that global cooperation between scientists, managers, politicians and general public, and application of new technologies (new generation sequencing and remote sensing, among others) will strengthen the quality of studies on the natural history and conservation of freshwater bivalves. Finally, we introduce the articles published in this special issue of Hydrobiologia under the scope of the Second International Meeting on Biology and Conservation of Freshwater Bivalves held in 2015 in Buffalo, New York, USA.This work was supported by FCT—Foundation for Science and Technology, Project 3599—Promote the Scientific Production and Technological Development and Thematic 3599-PPCDT by FEDER as part of the project FRESHCO: multiple implications of invasive species on Freshwater Mussel co-extinction processes (Contract: PTDC/AGRFOR/1627/2014). FCT also supported MLL under Grant (SFRH/BD/115728/2016)

Sizing mudsnails: Applying superpixels to scale growth detection under ocean warming

1. The expansion of scientific image data holds great promise to quantify individuals, size distributions and traits. Computer vision tools are especially powerful to automate data mining of images and thus have been applied widely across studies in aquatic and terrestrial ecology. Yet marine benthic communities, especially infauna, remain understudied despite their dominance of marine biomass, biodiversity and playing critical roles in ecosystem functioning. 2. Here, we disaggregated infauna from sediment cores taken throughout the spring transition (April-June) from a near-natural mesocosm setup under experimental warming (Ambient, +1.5 degrees C, +3.0 degrees C). Numerically abundant mudsnails were imaged in batches under stereomicroscopy, from which we automatically counted and sized individuals using a superpixel-based segmentation algorithm. Our segmentation approach was based on clustering superpixels, which naturally partition images by low-level properties (e.g., colour, shape and edges) and allow instance-based segmentation to extract all individuals from each image. 3. We demonstrate high accuracy and precision for counting and sizing individuals, through a procedure that is robust to the number of individuals per image (5-65) and to size ranges spanning an order of magnitude (40k individuals and revealed overall growth in response to springtime warming. 4. We illustrate that image processing and segmentation workflows can be built upon existing open-access R packages, underlining the potential for wider adoption of computer vision tools among ecologists. The image-based approach also generated reproducible data products that, alongside our scripts, we have made freely available. This work reinforces the need for next-generation monitoring of benthic communities, especially infauna, which can display differential responses to average warming

Novel trophic interaction between lake sturgeon (Acipenser fulvescens) and non-native species in an altered food web

Lake sturgeon (Acipenser fulvescens) were once abundantly distributed throughout the Laurentian Great Lakes. However, widespread overharvesting and habitat degradation has diminished their numbers. The lower Niagara River contains one of the few remnant lake sturgeon populations in New York State. This study determined the diet of adult lake sturgeon and quantified their trophic position in a food web dominated by non-native species. Stomach content analysis assessed recent diet, and stable isotope analysis (δ 15 N and δ 13 C) of blood and fin tissue quantified trophic position and carbon source over varying time scales. Two non-native species dominated the diet of lake sturgeon — the amphipod Echinogammarus ischnus (62% by number) and the round goby (Neogobius melanostomus) (44% by mass). Stable isotope analysis revealed that round goby was the primary contributor to the long-term (i.e., fin) average diet, whereas short-term (i.e., blood) diet was more diverse. In contrast with findings from other systems, we found that adult lake sturgeon in the lower Niagara River were primarily piscivorous, actively targeting live fish prey. The recovery of this population is potentially supported by the high availability of energetically rich but non-native food resources

Food depletion regulates the demography of invasive dreissenid mussels in a stratified lake

Lake stratification produces sharp gradients in temperature and pelagic resources which have cascading effects on the traits of aquatic populations, including invasive species and their ecosystem impacts. We study the consequences of such common environmental gradients on the demography of quagga mussels, one of the world’s most aggressive invasive species. Coupling a series of in situ experiments with a biophysical model of the pelagic community, we quantify mussel growth and recruitment in littoral vs. profundal benthic habitats of eastern Lake Erie. We found that both severe food depletion and cold temperatures in the hypolimnion during summer stratification cause mussels to grow twice as slowly and currently inhibit recruitment in profundal compared to littoral habitats. Together with the high biomass and large mean mussel size found in long‐term monitoring surveys in the profundal habitats, our results imply that mussels successfully colonizing profundal habitats have relatively long lifespans with low growth rates, and therefore lower productivity, compared to mussels in shallow areas. Consequently, the bulk of dreissenid biomass in Lake Erie and other Great Lakes found in the vast but resource‐poor profundal habitats may have very limited impacts on epilimnetic communities compared to mussels in littoral areas. By contrast, mussels in profundal habitats strongly reduce food availability to hypolimnetic communities throughout the year. Thus, our results explain how the ecosystem impacts of sessile freshwater invaders are likely to vary among habitats and lakes depending on the relative size of profundal populations and the extent of stratification.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/146606/1/lno10924_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/146606/2/lno10924.pd

Recent and future distribution of the alien Chinese pond mussel Sinanodonta woodiana (Lea, 1834) on the European continent

The alien freshwater mussel Sinanodonta woodiana (Lea, 1834) has rapidly spread throughout Europe over the past decades. This species can cope with a broad range of environmental conditions and has a high reproductive capacity making S. woodiana a successful invader. Due to its negative effects on native freshwater mollusk communities and parasitized fish it is critical to identify suitable habitats where S. woodiana may persist and how these habitats may be altered under future climate projections. We applied multivariate ordination methods to analyze the space-time relationship and a maximum entropy approach (MaxEnt) to predict the recent (1970–2000) and future (2041–2060 and 2081–2100) distribution of S. woodiana using environmental and climate variables for the European continent. After first sightings in 1979 there were only a few new locations and findings which increased unevenly and exponentially to a maximum of about 100 new locations per year followed by decline during the last few years. Under recent climate condition, 2.3% of European watersheds are predicted as highly suitable habitat for S. woodiana and located in the temperate climate zone between 40°N and 60°N. Suitable habitat was associated with lowland watersheds characterized by fluviatile deposits and agriculture. Elevation, the distance between water bodies, land cover and mean temperature of the coldest quarter were the main factors influencing the modeling results. For future climate scenarios, highly suitable habitat increased to 2.4% by the middle of this century and decreased to 2.2% by the end of the century under the ‘least radiative forcing’ scenario. For the intermediate and high radiative forcing in 2050 and 2100, highly suitable habitat decreased to 2.2% and 1.7% and to 2.2% and 2.2%, respectively. Results from our study can be used as a baseline to better understand potential invasion pathways, identify high risk areas, and to initiate early detection and rapid response strategies

The Lower Havel River Region (Brandenburg, Germany): A 230-Year-Long Historical Map Record Indicates a Decrease in Surface Water Areas and Groundwater Levels

Instrumental data show that the groundwater and lake levels in Northeast Germany have decreased over the past decades, and this process has accelerated over the past few years. In addition to global warming, the direct influence of humans on the local water balance is suspected to be the cause. Since the instrumental data usually go back only a few decades, little is known about the multidecadal to centennial-scale trend, which also takes long-term climate variation and the long-term influence by humans on the water balance into account. This study aims to quantitatively reconstruct the surface water areas in the Lower Havel Inner Delta and of adjacent Lake Gülpe in Brandenburg. The analysis includes the calculation of surface water areas from historical and modern maps from 1797 to 2020. The major finding is that surface water areas have decreased by approximately 30% since the pre-industrial period, with the decline being continuous. Our data show that the comprehensive measures in Lower Havel hydro-engineering correspond with groundwater lowering that started before recent global warming. Further, large-scale melioration measures with increasing water demands in the upstream wetlands beginning from the 1960s to the 1980s may have amplified the decline in downstream surface water areas

The Lower Havel River Region (Brandenburg, Germany): A 230-Year-Long Historical Map Record Indicates a Decrease in Surface Water Areas and Groundwater Levels

Instrumental data show that the groundwater and lake levels in Northeast Germany have decreased over the past decades, and this process has accelerated over the past few years. In addition to global warming, the direct influence of humans on the local water balance is suspected to be the cause. Since the instrumental data usually go back only a few decades, little is known about the multidecadal to centennial-scale trend, which also takes long-term climate variation and the long-term influence by humans on the water balance into account. This study aims to quantitatively reconstruct the surface water areas in the Lower Havel Inner Delta and of adjacent Lake Gülpe in Brandenburg. The analysis includes the calculation of surface water areas from historical and modern maps from 1797 to 2020. The major finding is that surface water areas have decreased by approximately 30% since the pre-industrial period, with the decline being continuous. Our data show that the comprehensive measures in Lower Havel hydro-engineering correspond with groundwater lowering that started before recent global warming. Further, large-scale melioration measures with increasing water demands in the upstream wetlands beginning from the 1960s to the 1980s may have amplified the decline in downstream surface water areas