Summary
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.
Microbial community composition and diversity change along chemical gradients, leading to the expectation that microbial community information might provide new gradient characterizations. Here we ...examine stream bacteria composition and diversity along a strong chemical gradient in Central Appalachian streams. Coal mining in the region generates alkaline mine drainage (AlkMD), causing dramatic increases in conductivity, alkalinity, sulfate and metals sufficient to degrade stream macrobiota communities throughout the ecoregion. In this study, we examined the relationship between water and biofilm chemistry and biofilm bacteria taxonomic composition in streams where active and reclaimed surface coal mines occupied 0-96% of watershed surface area. We incubated wood veneers in each stream site for 4 months to develop biofilms on similar substrates. We sampled water chemistry at the time of deployment and collection, and after 1 month. Following incubation, we collected biofilms for microbial and chemical characterization. Microbial composition was determined by pyrosequencing 16S rRNA amplicons. Biofilm subsamples were analyzed by inductively coupled plasma mass spectrometry to determine metal concentrations. Our results show that microbial community composition differed significantly between AlkMD-exposed and AlkMD-unexposed sites, and that compositional dissimilarity increased with AlkMD loading. Diversity was not correlated with pH or extent of upstream mining, but instead correlated with biofilm concentrations of Cd, Mn, Zn and Ni. Within mined sites, the extent of upstream mining was negatively correlated with taxonomic richness. Despite major compositional shifts, functional capacity predicted with PICRUSt (Phylogenetic Investigation of Communities by Reconstruction of Unobserved States) correlated with mining in only 3 of 43 level-2 KEGG (Kyoto Encyclopedia of Genes and Genomes) Orthology groups.
Fragmented forests contain natural edges, including riparian zones, and anthropogenic edges. Edges generally have lower plant density and fewer large trees than forest interior. Riparian edges, ...however, contain gap-specialist trees yielding leaves with high protein content, providing primates with important resources. We examined mantled howler monkeys’ behavioral responses to riparian and anthropogenic edges at La Suerte Biological Research Station (LSBRS), Costa Rica. We predicted the monkeys would spend more time resting and feeding and less time traveling, and be less spatially cohesive, in both anthropogenic and riparian edges compared to forest interior due to lower resource abundance in edges, and in anthropogenic compared to riparian edge due to higher leaf quality in riparian zones. From 2017 to 2020, we collected data across forest zones on activity and spatial cohesion patterns via focal sampling, recording data every 2 min. Howler monkeys were significantly more likely to rest and significantly less likely to travel in both anthropogenic and riparian edges compared to forest interior; however, there were no differences between these edge types. There were significantly more monkeys within a 5-m radius of focal subjects in both anthropogenic and riparian edges compared to forest interior, but no differences between these edge types. While prior research found no differences across zones when only anthropogenic edge and forest interior were compared, results of this study demonstrate that howler monkeys at LSBRS modify their activity patterns in anthropogenic and riparian edge zones compared to forest interior, highlighting the importance of focusing on both natural and anthropogenic edge zones to fully understand primates’ behavioral responses in fragmented landscapes.
With the majority of primates living close to forest edges, it is imperative to understand how edges affect primate distribution and behaviour. Definitions of edge, however, vary across studies, with ...many defining edge
a priori
and few explicitly measuring the depth of edge influence (DEI). In this study, we aimed to functionally define edge for mantled howler monkey (
Alouatta palliata
) distribution and howling behaviour in a fragmented rainforest. We surveyed howler monkey locations (walking 11 line transects a total of 253 times in May-August 2015 and 2016) and howling behaviour (584 observation hours across May-August 2017 and 2018) throughout the forest fragment and fit our data to several candidate models to estimate DEI. We found howler monkeys farther from anthropogenic edge and closer to river edge than expected by a random distribution of locations. We estimated DEIs for howl bout rate (bouts/hour), howl bout length, and howling rate per bout (howls/minute per bout) that were different to those used in previous work at this site, suggesting that
a priori
definitions of edge used in prior work were likely too small to detect edge effects and the methods used provide a more accurate picture of how edges impact these monkeys. Our results provide an example of how using different edge definitions can alter research findings, showing that mathematical methods of determining DEI are warranted. This mathematical approach to examining behavioural edge effects can be applied more broadly across primates to help us better understand how primates respond to edges.
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.
Summary
When 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.
We present a new modelling approach, the hierarchical diversity decision framework (HiDDeF) that explicitly communicates the sensitivity of water quality benchmarks to these implicit judgments. We apply HiDDeF to a data set of stream macroinvertebrate abundances across 218 sites in south‐western West Virginia, USA, where alkaline mine drainage increases streamwater conductivity and leads to the loss of sensitive taxa throughout regional river networks.
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 data set but requires only a fraction (~10%) of the sites required in previous studies. HiDDeF results suggest that the current conductivity benchmark (300 μS cm−1) for regional streams translates to 50% loss in abundance for at least one‐quarter of regional macroinvertebrate taxa.
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.
Environmental agencies across the United States have searched for adequate methods to assess anthropogenic impacts on the environment. Biological assessments, which compare the taxonomic composition ...of an aquatic assemblage to relevant biocriteria, have surfaced as an effective method to assess the ecological integrity of US waterbodies. In this study, bioassessment data were collected and analyzed in conjunction with physical habitat and chemical stressor data for streams and rivers within the San Diego basin from 1998 through 2005. Physical stressors such as sediment loading, riparian destruction, and in-stream habitat homogenization affect many locations in the region. However, physical habitat measures alone were found to frequently overestimate the biological integrity of streams in the region. Many sites within the San Diego Basin, although unaffected by physical stressors, continue to exhibit low biological integrity scores. Sites with low biological integrity tend to possess higher specific conductance and salinity compared to sites with high biological integrity. We suggest that one possible reason for these differences is the source water used for municipal purposes.
In this study, bioassessment data collected between 1998 and 2005 were synthesized and analyzed for streams and rivers throughout the San Diego Hydrologic Region to provide a spatial and temporal ...context for the results of several monitoring projects conducted between 1998 and 2005 and to ascertain the applicability of the Southern California benthic macroinvertebrate index of biological integrity (SoCal B-IBI) to the region’s streams. The water quality of the sites studied in the region, as reflected by temporal and spatial analyses of SoCal B-IBI scores, was found to be quite poor. When streams were analyzed individually most showed stable scores over the time frame of the study with some showing better scores in the fall. Spatially, scores were found to be better farther away from the coast in the upstream reaches of the watersheds. This study further explored the applicability of the SoCal B-IBI to a focused geographic region by demonstrating the necessity of each component metric to the assignment of biological condition. Although all component metric scores were deemed to be necessary, the percent intolerant individuals score had a more significant effect in driving impairment. The analysis of the component metrics of the SoCal B-IBI provides useful insights to the changes in scores among and between the sampled sites in the region’s watersheds. Based on this study, natural resource management agencies responsible for managing water quality should incorporate regular measures of biological integrity into their water quality programs to ascertain regional and temporal trends.
•We mentees of Dr. Bernhardt review the major findings from her research program.•We highlight how hydrologic connectivity alters ecosystem structure and function.•Dr. Bernhardt elevates ...interdisciplinarity in the hydrologic sciences.•Dr. Bernhardt is exceptionally dedicated to service, engagement, and mentorship.
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.
Not all pavements lead to streams Baruch, Ethan M.; Voss, Kristofor A.; Blaszczak, Joanna R. ...
Freshwater science,
09/2018, Volume:
37, Issue:
3
Journal Article
Peer reviewed
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 = 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.
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