Freshwater ecosystems are heavily impacted by multiple stressors, and a freshwater biodiversity crisis is underway. This realization has prompted calls to integrate global freshwater ecosystem data, including traditional taxonomic and newer types of data (e.g., eDNA, remote sensing), to more comprehensively assess change among systems, regions, and organism groups. We argue that data integration should be done, not only with the important purpose of filling gaps in spatial, temporal, and organismal representation, but also with a more ambitious goal: to study fundamental cross-scale biological phenomena. Such knowledge is critical for discerning and projecting ecosystem functional dynamics, a realm of study where generalizations may be more tractable than those relying on taxonomic specificity. Integration could take us beyond cataloging biodiversity losses, and toward predicting ecosystem change more broadly. Fundamental biology questions should be central to integrative, interdisciplinary research on causal ecological mechanisms, combining traditional measures and more novel methods at the leading edge of the biological sciences. We propose a conceptual framework supporting this vision, identifying key questions and uncertainties associated with realizing this research potential. Our framework includes five interdisciplinary "complementarities." First, research approaches may provide comparative complementarity when they offer separate realizations of the same focal phenomenon. Second, for translational complementarity, data from one research approach is used to translate that from another, facilitating new inferences. Thirdly, causal complementarity arises when combining approaches allows us to "fill in" cause-effect relationships. Fourth, contextual complementarity is realized when together research methodologies establish the wider ecological and spatiotemporal context within which focal biological responses occur. Finally, integration may allow us to cross inferential scales through scaling complementarity. Explicitly identifying the modes and purposes of integrating research approaches, and reaching across disciplines to establish appropriate collaboration will allow researchers to address major biological questions that are more than the sum of the parts.

Synthesis centers are a form of scientific organization that catalyzes and supports research that integrates diverse theories, methods and data across spatial or temporal scales to increase the generality, parsimony, applicability, or empirical soundness of scientific explanations. Synthesis working groups are a distinctive form of scientific collaboration that produce consequential, high-impact publications. But no one has asked if synthesis working groups synthesize: are their publications substantially more diverse than others, and if so, in what ways and with what effect? We investigate these questions by using Latent Dirichlet Analysis to compare the topical diversity of papers published by synthesis center collaborations with that of papers in a reference corpus. Topical diversity was operationalized and measured in several ways, both to reflect aggregate diversity and to emphasize particular aspects of diversity (such as variety, evenness, and balance). Synthesis center publications have greater topical variety and evenness, but less disparity, than do papers in the reference corpus. The influence of synthesis center origins on aspects of diversity is only partly mediated by the size and heterogeneity of collaborations: when taking into account the numbers of authors, distinct institutions, and references, synthesis center origins retain a significant direct effect on diversity measures. Controlling for the size and heterogeneity of collaborative groups, synthesis center origins and diversity measures significantly influence the visibility of publications, as indicated by citation measures. We conclude by suggesting social processes within collaborations that might account for the observed effects, by inviting further exploration of what this novel textual analysis approach might reveal about interdisciplinary research, and by offering some practical implications of our results.

The lower Columbia River (Washington and Oregon, USA) has been heavily invaded by a large number of planktonic organisms including the invasive copepod Pseudodiaptomus forbesi and the planktonic juveniles of the invasive clam, Corbicula fluminea. In order to assess the ecological impacts of these highly abundant invaders, we developed a multivariate auto-regressive (MAR) model of food web dynamics based upon a 12-year time-series of plankton community and environmental data from the Columbia River. Our model results indicate that plankton communities in the lower Columbia River are strongly impacted by the copepod P. forbesi at multiple trophic levels. We observed different ecological effects across different life stages of P. forbesi, with nauplii negatively impacting ciliates and autotrophs, and copepodite stages negatively impacting Daphnia and cyclopoid copepods. Although juvenile C. fluminea were highly abundant in the summer and autumn of each year, our best fit MAR model did not show significant C. fluminea impacts. Our results illustrate the strong ecological impact that some zooplankton invaders may cause within rivers and estuarine systems, and highlight the need for further research on the feeding ecology of the planktonic life-stage of C. fluminea. Overall, our study demonstrates the manner in which long-term, high resolution data sets can be used to better understand the ecological impacts of invasive species among complex and highly dynamic communities.

The study of environmental communication originated as a diverse multidisciplinary field encompassing a wide array of communicator perspectives. However, as the field evolved, mass media and journalism became its perceived scholarly focus. As a result, environmental communication processes may be less well-understood across other settings, such as scientific and research institutions, non-governmental organizations, and federal agencies. To understand how communicators describe their goals, ethics, and strategies within these contexts, we conducted a three-part study of researchers and practitioners working on environmental issues in the Washington, DC, region between October 2019 and January 2020. Employing Q methodology, we identified four distinct perspectives: capacity-builders, translators, policy and decision-supporters, and cultural changemakers. Each of these perspectives is associated with a different range of goals, ethics, and strategic approaches. We describe graduate educational competencies for each of the perspectives and discuss implications for the design of communication research to meet practitioners' needs.

Climate warming impacts ecosystems through multiple interacting pathways, including via direct thermal responses of individual taxa and the combined responses of closely interacting species. In this study, we examined how warming and infection by an oomycete parasite (Saprolegnia) affect the dominant zooplankter of Russia's Lake Baikal, the endemic copepodEpischurella baikalensis. We used a combination of laboratory experiments, long-term monitoring data, and population modeling. Experiments showed a large difference in the thermal optima of host and parasite, with strong negative effects of warm temperatures onE. baikalensissurvival and reproduction and a negative effect ofSaprolegniainfection on survival.Saprolegniainfection had an unexpected positive effect onE. baikalensisreproductive output, which may be consistent with fecundity compensation by females exposed to the parasite. Long-term monitoring data suggested thatSaprolegniainfections were most common during the warmest periods of the year. Population models, parameterized with experimental and literature data, correctly predicted the timing ofSaprolegniaepizootics, but overestimated the negative effect of warming onE. baikalensispopulations. Models suggest that diel vertical migration may allowE. baikalensisto escape the negative effects of increasing temperatures and parasitism and enableE. baikalensisto persist in the face of moderate warming of Lake Baikal. Our results contribute to understanding of how warming and parasitism interact to affect the pelagic ecosystems of cold lakes and oceans and how the consequences of these interacting stressors can vary seasonally, spatially, and interannually.

Among its many impacts, climate warming is leading to increasing winter air temperatures, decreasing ice cover extent, and changing winter precipitation patterns over the Laurentian Great Lakes and their watershed. Understanding and predicting the consequences of these changes is impeded by a shortage of winter-period studies on most aspects of Great Lake limnology. In this review, we summarize what is known about the Great Lakes during their 3-6 months of winter and identify key open questions about the physics, chemistry, and biology of the Laurentian Great Lakes and other large, seasonally frozen lakes. Existing studies show that winter conditions have important effects on physical, biogeochemical, and biological processes, not only during winter but in subsequent seasons as well. Ice cover, the extent of which fluctuates dramatically among years and the five lakes, emerges as a key variable that controls many aspects of the functioning of the Great Lakes ecosystem. Studies on the properties and formation of Great Lakes ice, its effect on vertical and horizontal mixing, light conditions, and biota, along with winter measurements of fundamental state and rate parameters in the lakes and their watersheds are needed to close the winter knowledge gap. Overcoming the formidable logistical challenges of winter research on these large and dynamic ecosystems may require investment in new, specialized research infrastructure. Perhaps more importantly, it will demand broader recognition of the value of such work and collaboration between physicists, geochemists, and biologists working on the world's seasonally freezing lakes and seas.

Millions of lakes worldwide are distributed at latitudes or elevations resulting in the formation of lake ice during winter. Lake ice affects the transfer of energy, heat, light, and material between lakes and their surroundings creating an environment dramatically different from open-water conditions. While this fundamental restructuring leads to distinct gradients in ions, dissolved gases, and nutrients throughout the water column, surprisingly little is known about the resulting effects on ecosystem processes and food webs, highlighting the lack of a general limnological framework that characterizes the structure and function of lakes under a gradient of ice cover. Drawing from the literature and three novel case studies, we present the Lake Ice Continuum Concept (LICC) as a model for understanding how key aspects of the physical, chemical, and ecological structure and function of lakes vary along a continuum of winter climate conditions mediated by ice and snow cover. We examine key differences in energy, redox, and ecological community structure and describe how they vary in response to shifts in physical mixing dynamics and light availability for lakes with ice and snow cover, lakes with clear ice alone, and lakes lacking winter ice altogether. Global change is driving ice covered lakes toward not only warmer annual average temperatures but also reduced, intermittent or no ice cover. The LICC highlights the wide range of responses of lakes to ongoing climate-driven changes in ice cover and serves as a reminder of the need to understand the role of winter in the annual aquatic cycle.

Sewage released from lakeside development can introduce nutrients and micropollutants that can restructure aquatic ecosystems. Lake Baikal, the world's most ancient, biodiverse, and voluminous freshwater lake, has been experiencing localized sewage pollution from lakeside settlements. Nearby increasing filamentous algal abundance suggests benthic communities are responding to localized pollution. We surveyed 40-km of Lake Baikal's southwestern shoreline from 19 to 23 August 2015 for sewage indicators, including pharmaceuticals, personal care products, and microplastics, with colocated periphyton, macroinvertebrate, stable isotope, and fatty acid samplings. The data are structured in a tidy format (a tabular arrangement familiar to limnologists) to encourage reuse. Unique identifiers corresponding to sampling locations are retained throughout all data files to facilitate interoperability among the dataset's 150+ variables. For Lake Baikal studies, these data can support continued monitoring and research efforts. For global studies of lakes, these data can help characterize sewage prevalence and ecological consequences of anthropogenic disturbance across spatial scales.

Grazing by microzooplankton has been shown to significantly impact freshwater cyanobacteria blooms; however, the contribution of rotifers to the overall effect of microzooplankton grazing is not well understood. We conducted monthly microzooplankton community grazing (dilution) experiments June-October 2019, concurrent with incubations of field-collected rotifers feeding upon the natural assemblage of microplankton prey < 75 mu m in Vancouver Lake (Washington State, USA), a lake annually affected by cyanobacteria blooms. Our results showed that just days after a large bloom, the microzooplankton community grazing impact on phytoplankton biomass was exceptionally high (> 1000% d(-1)), yet the impact by rotifers was low (< 1% d(-1)). As the bloom diminished in September and October, the grazing impact of rotifers increased dramatically, specifically consuming substantial dinoflagellate (<= 574%) and ciliate (<= 382%) biomass daily. Analysis of rotifers in Vancouver Lake during these months showed the presence of large, carnivorous Asplanchna spp., which indicates multi-trophic grazing dynamics within the rotifer assemblage. We conclude that non-rotifer micro-grazers (i.e., ciliates) were likely responsible for the initial dissipation of cyanobacteria just after the bloom peak, while rotifers primarily removed micro-grazers later in autumn. This study highlights the trophic roles of micro-grazers in controlling harmful cyanobacteria blooms and quantifies the specific grazing contributions of rotifers.

Mountain lakes experience interannual variability in spring snowpack and ice cover that can lead to differences in physical, chemical, and biological properties in the succeeding summer. Lake studies that capture extreme years of snow and ice would be useful to understand and anticipate effects of climate change, but such data are rare for remote mountain lakes. Monitoring of lakes in Olympic, North Cascades, and Mount Rainier National Parks from 2007 to 2018 allowed us to examine limnological differences along interannual and elevation-driven climate gradients that included unusually high (2011-2012) and 100-yr record low (2015) snowpack years. Years with lower spring snowpack had earlier ice-out. Across lakes, our analysis suggested an average of 0.075 degrees C lake warming per day of lost ice duration (0.525 degrees C per week), giving rise to other ecosystem changes linked to temperature such as lower dissolved oxygen, higher total dissolved N, higher chlorophyll, and higher abundance of cladoceran zooplankton. Conversely, in years with higher snowpack and a shorter ice-free season, lakes were colder and clearer (1 m deeper Secchi depth for every 1 m May snow water equivalent), with more dilute ions as well as lower algal biomass and zooplankton abundance. These results add to evidence that changes in snowpack or ice-out dates alter mountain lake ecology through multiple processes associated with hydrology, terrestrial-aquatic connection, water temperature, productivity, ion composition, and plankton communities.