Functional Changes in Littoral Macroinvertebrate Communities in Response to Watershed-Level Anthropogenic Stress

Watershed-scale anthropogenic stressors have profound effects on aquatic communities. Although several functional traits of stream macroinvertebrates change predictably in response to land development and urbanization, little is known about macroinvertebrate functional responses in lakes. We assessed functional community structure, functional diversity (Rao’s quadratic entropy) and voltinism in macroinvertebrate communities sampled across the full gradient of anthropogenic stress in Laurentian Great Lakes coastal wetlands. Functional diversity and voltinism significantly decreased with increasing development, whereas agriculture had smaller or non-significant effects. Functional community structure was affected by watershed-scale development, as demonstrated by an ordination analysis followed by regression. Because functional community structure affects energy flow and ecosystem function, and functional diversity is known to have important implications for ecosystem resilience to further environmental change, these results highlight the necessity of finding ways to remediate or at least ameliorate these effects

Widespread retreat of coastal habitat is likely at warming levels above 1.5 °C

Several coastal ecosystems—most notably mangroves and tidal marshes—exhibit biogenic feedbacks that are facilitating adjustment to relative sea-level rise (RSLR), including the sequestration of carbon and the trapping of mineral sediment. The stability of reef-top habitats under RSLR is similarly linked to reef-derived sediment accumulation and the vertical accretion of protective coral reefs. The persistence of these ecosystems under high rates of RSLR is contested. Here we show that the probability of vertical adjustment to RSLR inferred from palaeo-stratigraphic observations aligns with contemporary in situ survey measurements. A defcit between tidal marsh and mangrove adjustment and RSLR is likely at 4 mm yr−1 and highly likely at 7 mm yr−1 of RSLR. As rates of RSLR exceed 7 mm yr−1, the probability that reef islands destabilize through increased shoreline erosion and wave over-topping increases. Increased global warming from 1.5 °C to 2.0 °C would double the area of mapped tidal marsh exposed to 4 mm yr−1 of RSLR by between 2080 and 2100. With 3 °C of warming, nearly all the world’s mangrove forests and coral reef islands and almost 40% of mapped tidal marshes are estimated to be exposed to RSLR of at least 7 mm yr−1. Meeting the Paris agreement targets would minimize disruption to coastal ecosystems

Aquatic invasive species: general trends in the literature and introduction to the special issue

Invasion rates are increasing worldwide and most are due to the actions of humans. Deliberate introductions, escapes, and hitchhiking with global commerce transport species to other continents. While most species fail to thrive or have minor impacts on their new ecosystems, the large number of introductions has led to numerous problems. Aquatic invasive species are particularly pervasive and may cause food web disruption, biodiversity loss, and economic harm. Biological invasions appear in an increasing number of publications in the aquatic and general ecology literature. This special issue of Hydrobiologia includes 31 papers on aquatic invasive species and the factors that influence their dispersal and success, along with their impacts. Ecosystems include freshwater ponds, lakes and reservoirs, small streams and large rivers, and coastal marine systems. Study regions occur in temperate, as well as less-studied tropical and sub-tropical regions of four different continents. We discuss the dynamics of invasive species research in the current literature and provide a brief overview of the contributions to this issue

Natural Resources Research Institute Technical Report

The original version of this report (published April 2020) contained a calculations error; this revised version (published June 2020) has been corrected.Beavers (Castor canadensis) play a substantial role in coastal Lake Superior ecosystems, as the creation of beaver dams and ponds results in riparian habitat that can be vastly different from habitats before beaver activity (Naiman et al. 1988, Rosell et al. 2005). Beaver dams can influence water temperatures, flow regimes, channel morphology, and sediment dynamics (Gurnell 1998, Pollock et al. 2003, Westbrook et al. 2006, Burchsted et al. 2010, Bouwes et al. 2016). Understanding where beavers are likely to build dams and ponds has many practical implications for resource managers and citizens. Current climate models have predicted an increase in the prevalence of extreme precipitation events that may cause an increase in erosion and flooding events in the North Shore (Herb et al. 2016). Beaver dams have been shown to mitigate the downstream effects of high-precipitation events by reducing stream energy and increasing water retention time (Law et al. 2016, Puttock et al. 2017, Karran et al. 2017); their presence in the North Shore may be an important natural mechanism for minimizing impacts from natural hazards. But they also may have an adverse effect on fisheries, particularly steelhead (Oncorhynchus mykiss) and brook trout (Salvelinus fontinalis) (Johnson-Bice et al. 2018), leading to controversy within coastal communities and complex management decisions. The goal of this study was to create a model that predicts potential beaver dam locations based on existing habitat characteristics, stream gradient, and stream power and flow estimates. Building from an existing data set that includes spatial information of beaver-created wetlands within five North Shore watersheds, we also conducted a rapid assessment of water and sediment storage contained within beaver ponds across the North Shore. The key deliverables of this project are: ● An interactive online map showing historic and potential beaver dam locations ● Estimates of water and sediment storage in North Shore beaver wetlands ● A downloadable spatial database of existing and predicted beaver dam locations, with FGDC-compliant metadata ● This report describing methods, results, and interpretations These products will be important for resource managers that make land-use decisions based on current and future hydrologic and sediment pathways in Lake Superior tributaries

Aquatic invasive species: challenges for the future

Humans have effectively transported thousands of species around the globe and, with accelerated trade; the rate of introductions has increased over time. Aquatic ecosystems seem at particular risk from invasive species because of threats to biodiversity and human needs for water resources. Here, we review some known aspects of aquatic invasive species (AIS) and explore several new questions. We describe impacts of AIS, factors limiting their dispersal, and the role that humans play in transporting AIS. We also review the characteristics of species that should be the greatest threat for future invasions, including those that pave the way for invasions by other species (“invasional meltdown”). Susceptible aquatic communities, such as reservoirs, may serve as stepping stones for invasions of new landscapes. Some microbes disperse long distance, infect new hosts and grow in the external aquatic medium, a process that has consequences for human health. We also discuss the interaction between species invasions and other human impacts (climate change, landscape conversion), as well as the possible connection of invasions with regime shifts in lakes. Since many invaders become permanent features of the environment, we discuss how humans live with invasive species, and conclude with questions for future research

Aquatic invasive species: introduction to the Special Issue and dynamics of public interest

Aquatic invasive species research has been surging in popularity, with the number of papers published in Hydrobiologia doubling since the previous decade. We overview contributions to the current Special Issue, including new studies on introduction and establishment, traits distinguishing high-impact invaders and their impacts, interactions between AIS and other human stressors as well as new developments in management. In addition, we analyze public interest in invasive species using 17 years of data (2004–2020) on absolute search volumes from Google extracted using Keywords Everywhere app. In particular, we analyze trends in searches for invasive species in general, several high-impact AIS, as well as the popularity of invasive species searches contrasted with other commonly recognized ecological problems in aquatic ecosystems. During the available search period, search volume for invasive species in general has increased and compared favorably with other ecological issues, whereas search volume patterns for high-impact AIS were species-specific and often exceeded search volumes for the general keyword. Public engagement is critical for all aspects of AIS research and management, and analysis of search volumes can be used to gauge, sustain and diversify this engagement

Watershed Land Use and Local Habitat: Implications for Habitat Assessment

Our understanding of anthropogenic stressor effects on wetland biota and ecosystem processes would benefit from better defined relationships between landscape and local stressors. We assessed the connection between watershed land use and local habitat and local disturbance in Great Lakes coastal ecosystems across a full range of anthropogenic stress. In addition, we identified dominant structuring variables, described redundancy, and assessed the relative influence of local versus watershed scale features on local habitat quality with on-site assessments conducted at 143 sample sites. Associations between habitat variables and watershed stressors were found, but only a small proportion of variation was explained. Overall, watershed agriculture was a stronger predictor of local habitat variables than was development. Variance partitioning revealed that disturbance and land use accounted for more variance in habitat than spatial factors or wetland type. This indicates that local and watershed-scale assessments are discrete approaches that document stress at different hierarchical scales and an assumed direct connection between watershed stress and local habitat and disturbance is an over-simplification. Therefore, assessments of stress should include both watershed scale and on-site habitat assessments. Furthermore, these results indicate that local scale mitigation/restoration could minimize negative impacts of changing land use

Effects of human land use on avian functional and taxonomic diversity within the upland coastal zone of the North American Great Lakes

Breeding birds in North America’s eastern and boreal forests have experienced significant population declines in recent decades due largely to habitat loss. The North American Great Lakes coastal zone provides critical stopover and breeding habitat for millions of migratory and resident birds with diverse life history traits. Extensive human land use in this region has resulted in significant forest loss. To understand how functional and taxonomic diversity of breeding bird communities have been affected by agriculture and urbanization in this region, we calculated measures of functional diversity, Shannon’s diversity index, and species richness along a gradient of human land use intensity. We analyzed bird survey data collected at 2982 locations within 1 km of the shoreline where upland forest was the dominant habitat. We used hierarchical partitioning to determine the extent to which spatial confounding factors (i.e., broad climatic and biogeographic gradients across the five Great Lakes) accounted for observed differences in diversity measures, and then used fourth-corner analysis to describe the relationship between species, functional traits, and land cover types. Although spatial confounding factors accounted for some variation, functional evenness, species richness, and Shannon’s diversity index declined significantly with increasing human land use. Species negatively associated with increasing human land use were those that eat primarily invertebrates by foraging on foliage or bark (75%) and species categorized as long-distance migrants (58%), which suggests increased vulnerability of forest-dependent species to habitat modification and reductions in habitat availability. Functional evenness declined with increasing human land use, while other measures of functional diversity (functional dispersion and Rao’s quadratic entropy) remained relatively constant. Understanding the disconnect between functional and taxonomic diversity of bird assemblages and quantifying the degree of resilience of functional community properties is critical for predicting long-term effects of both habitat loss and ecological restoration on biodiversity and ecosystem function