Effects of mountaintop removal coal mining on the diversity and secondary productivity of Appalachian rivers

Land cover change often alters the chemical regime and reduces the diversity of sensitive taxa in downstream aquatic ecosystems. The consistently elevated ionic strength associated with surface coal mines has been implicated in extirpating sensitive taxa throughout many Appalachian streams. We quantified secondary production at three sites spanning a gradient of mining impacts in the Mud River (West Virginia, U.S.A.) by sampling macroinvertebrates monthly from 2012 to 2013. Not only do we observe significant changes in aquatic insect community structure driven by the loss of sensitive taxa in mined watersheds, but we show that these losses translate directly to depressed biomass throughout the year becoming most apparent when pollutant concentrations rise during summer baseflow. These distinct seasonal patterns result in threefold decreases in total insect production and EPT production ∼1-km downstream of an unmined reach. Farther downstream, where pollutant concentrations are much higher, total annual productivity is similar to the unmined reach, but suffers from a 31% loss of taxa comprising production and altered timing of that production. Mayflies were the insects most notably affected by the chemical alteration. Whereas mayflies accounted for ∼14% of total production in our upstream, unmined site, they only accounted for 0.2% of production at the most impacted site. We conclude that elevated ionic strength depresses insect production by preventing sensitive taxa from completing their life cycles in mining-impacted streams. Because surface coal mining dominates the Central Appalachian landscape, such altered production patterns are likely a common landscape feature impacting regional food webs

Taxa Abundance and Site Data

This file contains both species abundance data and site-level data (e.g. watershed characteristics, water chemistry, habitat scores) for 218 sites analyzed in our paper

Data from: From a line in the sand to a landscape of decisions: a Hierarchical Diversity Decision Framework (HiDDeF) for estimating and communicating biodiversity loss along anthropogenic gradients

1. In setting water quality criteria, managers must choose thresholds for stressors that are protective of aquatic biodiversity. Setting such thresholds requires making implicit judgments about the degree of biodiversity loss that managers are willing to accept. 2. We present a new modeling approach, the Hierarchical Diversity Decision Framework model (HiDDeF) that explicitly communicates the sensitivity of water quality benchmarks to these implicit judgements. We apply HiDDeF to a dataset of stream macroinvertebrate abundances across 218 sites in southwestern West Virginia, USA where alkaline mine drainage increases streamwater conductivity and leads to the loss of sensitive taxa throughout regional river networks. 3. By integrating responses of individual taxa within a flexible hierarchical framework, HiDDeF reliably predicts macroinvertebrate assemblages across the full range of conductivities observed in the training dataset but requires only a fraction of the sites required in previous studies. HiDDeF results suggest that the current conductivity benchmark (300 μS/cm) for regional streams translates to 50% loss in abundance for at least one-quarter of regional macroinvertebrate taxa. 4. HiDDeF produces a “decision landscape” that allows decision makers to assess sensitivity of proposed benchmarks to their choice of protective level. HiDDeF allows users to investigate both individual and community level responses to environmental gradients and generates output that includes a comprehensive summary of uncertainty in model parameters

Not all pavements lead to streams: Variation in impervious surface connectivity affects urban stream ecosystems

Watershed urbanization leads to chemical and thermal pollution of urban streams and significant declines in aquatic biodiversity. Most investigators have focused on variation in total watershed impervious surface cover (ISC) as the primary driver of urban stream degradation. We asked instead whether the degree of connectivity between ISC and urban stream channels alters its effect. We compared 7 streams in the Raleigh–Durham metropolitan area of the southeastern USA that drained watersheds with similar amounts of pavement (ISC 5 7–16% of watershed area) but spanning a wide range of hydrologic connectivity between these pavements and their receiving streams via both subsurface (pipe density range: 1.1–6.9 km/km2) and surface (road density range: 5.8–10.7 km/ km2) flowpaths. Despite draining watersheds with similarly low levels of development, these 7 streams exhibited remarkable variability in their hydrologic and thermal regimes and varied in their macroinvertebrate diversity from a low of only 11 taxa to a high of 22. Both macroinvertebrate community composition and the tissue concentrations of Cu, Pb, and Zn in 3 stream invertebrate taxa (Cambaridae, Tipulidae, and Hydropsychidae) found across all sites were correlated with watershed hydrologic connectivity. These results suggest that the connectivity of ISC may drive considerable variation in the magnitude of ecosystem degradation associated with the same level of watershed development, with less connected or disconnected impervious surfaces having proportionally lower negative effects on aquatic organisms

The influence of anthropogenic edge effects on primate populations and their habitat in a fragmented rainforest in Costa Rica

When a forest is fragmented, this increases the amount of forest edge relative to the interior. Edge effects can lead to loss of animal and plant species and decreased plant biomass near forest edges. We examined the influence of an anthropogenic forest edge comprising cattle pasture, coconut plantations, and human settlement on the mantled howler (Alouatta palliata), white-faced capuchin (Cebus capucinus), Central American spider monkey (Ateles geoffroyi), and plant populations at La Suerte Biological Research Station (LSBRS), Costa Rica. We predicted that there would be lower monkey encounter rate, mean tree species richness, and diameter at breast height (DBH) in forest edge versus interior, and that monkeys would show species-specific responses to edge based on diet, body size, and canopy height preferences. Specifically, we predicted that howler monkeys would show positive or neutral edge effects due to their flexible folivorous diet, large body size, and preference for high canopy, capuchins would show positive edge effects due to their diverse diet, small body size, and preference for low to middle canopy, and spider monkeys would show negative edge effects due their reliance on ripe fruit, large body size, and preference for high upper canopy. We conducted population and vegetation surveys along edge and interior transects at LSBRS. Contrary to predictions, total monkey encounter rate did not vary between the forest edge and forest interior. Furthermore, all three species showed neutral edge effects with no significant differences in encounter rate between forest edge and interior. Interior transects had significantly higher mean tree species richness than edge transects, and interior trees had greater DBH than edge trees, although this difference was not significant. These results suggest that forest edges negatively impact plant populations at La Suerte but that the monkeys are able to withstand these differences in vegetation

In search of microbial indicator taxa: shifts in stream bacterial communities along an urbanization gradient

A majority of environmental studies describe microbiomes at coarse scales of taxonomic resolution (bacterial community, phylum), ignoring key ecological knowledge gained from finer-scales and microbial indicator taxa. Here, we characterized the distribution of 940 bacterial taxa from 41 streams along an urbanization gradient (0%–83% developed watershed area) in the Raleigh-Durham area of North Carolina (USA). Using statistical approaches derived from macro-organismal ecology, we found that more bacterial taxa were classified as intolerant than as tolerant to increasing watershed urbanization (143 vs 48 OTUs), and we identified a threshold of 12.1% developed watershed area beyond which the majority of intolerant taxa were lost from streams. Two bacterial families strongly decreased with urbanization: Acidobacteriaceae (Acidobacteria) and Xanthobacteraceae (Alphaproteobacteria). Tolerant taxa were broadly distributed throughout the bacterial phylogeny, with members of the Comamonadaceae family (Betaproteobacteria) presenting the highest number of tolerant taxa. Shifts in microbial community structure were strongly correlated with a stream biotic index, based on macroinvertebrate composition, suggesting that microbial assemblages could be used to establish biotic criteria for monitoring aquatic ecosystems. In addition, our study shows that classic methods in community ecology can be applied to microbiome datasets to identify reliable microbial indicator taxa and determine the environmental constraints on individual taxa distributions along environmental gradients

At the Interfaces of the Hydrologic Sciences: Connecting Water, Elements, Ecosystems, and People Through the Major Contributions of Dr. Emily Bernhardt

In this paper, we describe the major contributions of Professor Emily Bernhardt to the hydrologic sciences. Dr. Bernhardt’s work addresses how carbon, nutrient, and contaminant dynamics respond to a wide range of environmental perturbations that alter hydrologic dynamics within and connectivity among ecosystems. Her research leverages intensive and extensive field sampling, experimental manipulations, macroscale data harmonization and exploration, and continental to global-scale synthesis activities to uncover key drivers and patterns of the impacts human perturbations have on water and elemental cycles. Dr. Bernhardt’s research program is defined by her ability to ask questions and use approaches that explicitly consider connectivity and interfaces in a variety of ways. Here, we highlight significant contributions from Dr. Bernhardt’s work, organized by connectivity, interfaces, and interactions among and across (1) elemental cycles, (2) ecosystems, (3) watersheds, (4) scales, and (5) disciplines. We conclude with a section on Dr. Bernhardt’s impact on the hydrologic sciences and beyond through her exceptional dedication to mentorship, engagement, and service