Nathan J. Smucker

Use of diatoms to assess agricultural and coal mining impacts on streams and a multiassemblage case study

Abstract We developed and tested a species-level Bray–Curtis (BC) similarity to reference index and a genus-level diatom model affinity (DMA) index to quantify agricultural and acid mine drainage (AMD) impacts on streams in the Western Allegheny Plateau of southeastern Ohio. Decreased similarity to references sites was found in impaired streams, and diatom metrics further indicated how assemblages were impacted. Sites identified by index scores as impaired had significantly greater conductivity, PO4-P, Ca2+, Mg2+, Na+, Cl−, % pasture in the upstream watershed, and forest fragmentation than minimally impaired sites (p < 0.05). Percent acidophilic diatoms significantly increased with reduced alkalinity caused by mining impacts (p < 0.01). Relative abundances of species indicating low P and N status decreased with increased pasture and row crops in upstream watersheds (p < 0.01), whereas abundance of motile diatoms increased (p < 0.01). In a case study, diatom, macroinvertebrate, and fish assemblages were compared among 18 sites in a single watershed (6 sites along an AMD impact gradient, 6 NaOH-treated AMD sites, and 6 sites with no mining impacts). All assemblages indicated severe impairment by AMD, but fish were least useful because they were absent from 5 of the 6 sites. Macroinvertebrates indicated unimpaired conditions at treated sites, but fish signaled potential problems (lower than expected biomass and presence of deformities) despite high species richness and index of biotic integrity scores. Diatom indices indicated significant impairment at AMD and treated sites (p < 0.01). Diatom metrics and indices very effectively signaled agricultural and mining impacts at the regional scale and were especially useful in the case study because they provided finer resolution of AMD effects and additional information of ecological importance missed by or in conflict between macroinvertebrate and fish assemblages. The DMA and BC indices responded similarly to stressors at the regional scale, but BC more effectively signaled impacts at the watershed scale. However, DMA was an effective assessment tool that might be used more easily than BC by novice phycologists and watershed groups because it requires less taxonomic expertise. If implemented in future watershed or regional studies, diatom indices could greatly benefit policy, management plans, and current monitoring efforts.

Acid mine drainage affects the development and function of epilithic biofilms in streams

Abstract Acid mine drainage (AMD) is a legacy of historical coal mining that affects several thousand stream kilometers around the world by contributing high loads of acidity, SO42−, metals, and other cations. Most research has focused on how AMD affects diversity and structure of various biological assemblages, whereas considerably less has focused on functional processes in streams. We investigated how AMD from abandoned coal mines affects epilithic biofilm development and function. Algal biomass and accrual rates were significantly lower in AMD-affected stream reaches than in control streams. Biomass and accrual rates were lowest at intermediate AMD-affected sites (pH  =  5.1–5.9), probably because copious amounts of AlOH3 precipitates smothered the benthic habitat. Ratios of β-glucosidase (GLU):β-xylosidase (XYLO) were significantly correlated with algal biomass (r  =  0.60, p < 0.01), probably because algae are important sources of C that is readily broken down by bacterial GLU activity, whereas XYLO is mostly associated with C of allochthonous origin. Thus, reduced algal biomass could indirectly exacerbate AMD effects on bacterial function by providing less C needed for cellular functions. Ratios of phosphatase∶leucine aminopeptidase significantly increased as pH decreased (R2  =  0.88, p < 0.01). This increase indicated potential P limitation or stressful conditions for microbial communities because PO4-P readily adsorbs to metal hydroxides, rendering it biologically inaccessible. Ratios in 3 of 4 control streams indicated that N limitation may be more typical in unaffected streams of the region. Low algal biomass and potential P limitation of biofilms may indicate that AMD-affected streams have reduced capabilities to retain nutrients and energy needed to support healthy ecosystems. Considering the links between biofilm structure and function can provide a framework for developing management strategies to restore and conserve ecosystem processes, such as nutrient retention and spiraling, energy flow, food webs, and biodiversity.

Effects of climate on the expression of the urban stream syndrome

Urban streams display many similar symptoms around the world, but awareness is growing that the mechanisms and severity of the symptoms differ among regions. Climate is a key contributor to these differences via: 1) variation in the initial conditions of streams across climate (and their sensitivity to urbanization), 2) interactions between climate and urbanization, and 3) indirect effects of climate on the form of urbanization or management via effects on human behaviors. We discuss the direct and indirect pathways by which climate shapes the structure and function of urban streams and how differences in climate affect how the urban stream syndrome is manifested. For some symptoms, such as stream flashiness, climate can affect the direction and magnitude of response, whereas for others, such as losses of sensitive taxa, climate can affect the magnitude of the response. Mechanisms linking urbanization with ecological degradation, even when responses are similar, can differ among climates. Limited research has been done on the role of climate in stream response to urbanization. Controlled, large-scale studies are needed to address this issue, particularly because climate may covary with types of infrastructure and technological capabilities across the globe. Understanding the linkages between climate and urban stream ecosystems will improve our theoretical understanding of urban streams and our ability to implement tailored and regionally sensitive management strategies.

Diatom responses to watershed development and potential moderating effects of near-stream forest and wetland cover

Abstract. Watershed development alters hydrology and delivers anthropogenic stressors to streams via pathways affected by impervious cover. We characterized relationships of diatom communities and metrics with upstream watershed % impervious cover (IC) and with riparian % forest and wetland cover in 120-m buffers along each side of upstream networks. Threshold Indicator Taxa ANalysis (TITAN) identified potential threshold responses of diatom communities at 0.6 and 2.9% IC. Boosted regression trees (BRTs) indicated potential thresholds between 0.7 and 4.5% IC at which relative abundances of low-nutrient diatoms decreased and those of high-nutrient, prostrate, and motile diatoms increased. These individual thresholds indicated that multiple stressors or magnitudes of stressors related to increasing watershed % IC differentially affected relative abundances of taxa, and these differential effects probably contributed to a more gradual, but still substantial, change in overall community structure. BRTs showed that near-stream buffers with >65% and ideally >80% forest and wetland cover were associated with a 13 to 34% reduction in the effects of watershed % IC on diatom metrics and community structure and with a 61 to 68% reduction in the effects of watershed % pasture on motile and high-P diatom relative abundances. Watershed % IC and riparian % forest and wetland cover probably affect hydrologic, nutrient, and sediment regimes, which then affect diatom community physiognomy and taxa sensitive to nutrients and conductivity. Our results emphasize the importance of implementing mindful development and protective measures, especially in watersheds near watershed % IC thresholds. Effects of development potentially could be reduced by restoring and conserving near-stream forests and wetlands, but management and restoration strategies that extend beyond near-stream buffers are needed.

Potential roles of past, present, and future urbanization characteristics in producing varied stream responses

Stormwater drainage and wastewater disposal are primary pathways through which urbanization degrades streams. These technologies and management practices change over time, reshaping the urban template and affecting the environmental challenges a city will face in the following decades to centuries. Spatial and temporal asynchrony in the implementation and replacement of these technologies and the adoption of new management approaches means that the mechanisms of the urban stream syndrome will be heterogeneous. Thus, promoting ‘one size fits all’ global panaceas for urban streams may be less effective than local solutions based on the unique urban templates and socioeconomic factors governing streams. Understanding the cumulative effects of spatiotemporal changes in urban templates on streams is critical to protecting and managing them because: 1) existing water infrastructure in many countries (especially high-income countries) is aging and requires replacement, 2) urbanization in rapidly developing countries requires ever more infrastructure, and 3) demand for higher levels of environmental quality is transforming technological and management approaches globally. The management and technological decisions made during the current infrastructure replacement or new construction cycle will define the future urban template and select the trajectory and character of the urban stream syndrome during the coming decades.

Roles of benthic algae in the structure, function, and assessment of stream ecosystems affected by acid mine drainage

Tens of thousands of stream kilometers worldwide are degraded by a legacy of acid loads, high metal concentrations, and altered habitat caused by acid mine drainage (AMD) from abandoned underground and surface mines. As the primary production base in streams, the condition of algal‐dominated periphyton communities is particularly important to nutrient cycling, energy flow, and higher trophic levels. Here, we synthesize current knowledge regarding how AMD‐associated stressors affect (i) algal communities and their use as ecological indicators, (ii) their functional roles in stream ecosystems, and (iii) how these findings inform management decisions and evaluation of restoration effectiveness. A growing body of research has found ecosystem simplification caused by AMD stressors. Species diversity declines, productivity decreases, and less efficient nutrient uptake and retention occur as AMD severity increases. New monitoring approaches, indices of biological condition, and attributes of algal community structure and function effectively assess AMD severity and effectiveness of management practices. Measures of ecosystem processes, such as nutrient uptake rates, extracellular enzyme activities, and metabolism, are increasingly being used as assessment tools, but remain in their infancy relative to traditional community structure‐based approaches. The continued development, testing, and implementation of functional measures and their use alongside community structure metrics will further advance assessments, inform management decisions, and foster progress toward restoration goals. Algal assessments will have important roles in making progress toward improving and sustaining the water quality, ecological condition, and ecosystem services of streams in regions affected by the legacy of unregulated coal mining.

Can pollution severity affect diatom succession in streams and could it matter for stream assessments

While the succession of benthic diatoms on scoured substrata has been widely studied to better understand community recovery from high flow disturbances, how anthropogenic stressors affect this common and dynamic process has received little attention; yet, it could have consequences for bioassessment and subsequent management decisions. Our objectives were to examine if the severity of acid mine drainage (AMD), a stressor of common concern in several countries, affected patterns of community development, diversity, and stream assessment outcomes (based on diatom metrics and indices) when diatoms are sampled during succession. In southeastern Ohio (USA), we deployed unglazed ceramic tiles in three streams along an AMD-impact gradient and in a control stream with no upstream AMD sources, and we sampled diatoms on days 5, 12, 19, 26, and 33. Diatom diversity decreased as AMD severity increased. In more severely AMD-impacted streams, diatom succession was simplified with less community turnover during the 33-day study than the least impacted AMD stream and control stream. Variability in community structure, diversity, and index scores was greatest at the least impacted AMD site. This stream was misclassified during succession by the Diatom Model Affinity index (severely impaired, then unimpaired, then ultimately moderately impaired) and the AMD – Diatom Index of Biotic Integrity (fair condition, then ultimately good condition). The control stream and the two more severely AMD-impacted streams were never misclassified during succession. Severe pollution may reduce niche availability by overriding effects of other environmental gradients important to diatoms (e.g., light and nutrients). The variability at intermediate stressor levels might lead to misclassification and misdirected management decisions if care is not taken to ensure a community has fully recovered from disturbance.

Stable isotopes of algae and macroinvertebrates in streams respond to watershed urbanization, inform management goals, and indicate food web relationships

Watershed development and anthropogenic sources of nitrogen are among leading causes of negative impacts to aquatic ecosystems around the world. The δ15N of aquatic biota can be used as indicators of anthropogenic sources of nitrogen enriched in 15N, but this mostly has been done at small spatial extents or to document effects of point sources. In this study, we sampled 77 sites along a forest to urban land cover gradient to examine food webs and the use of δ15N of periphyton and macroinvertebrate functional feeding groups (FFGs) as indicators of watershed development and nitrogen effects on streams. Functional feeding groups had low δ15N variability among taxa within sites. Mean absolute differences between individual taxa and their respective site FFG means were < 0.55‰, whereas site means of δ15N of FFGs had ranges of approximately 7-12‰ among sites. The δ15N of periphyton and macroinvertebrate FFGs distinguished least disturbed streams from those with greater watershed urbanization, and they were strongly correlated with increasing nitrogen concentrations and watershed impervious cover. Nonmetric multidimensional scaling, using δ15N of taxa, showed that changes in macroinvertebrate assemblages as a whole were associated with forest-to-urban and increasing nitrogen gradients. Assuming an average +3.4‰ per trophic level increase, δ15N of biota indicated that detrital pathways likely were important to food web structure, even in streams with highly developed watersheds. We used periphyton and macroinvertebrate FFG δ15N to identify possible management goals that can inform decisions affecting nutrients and watershed land use. Overall, the δ15N of periphyton and macroinvertebrates were strong indicators of watershed urban development effects on stream ecosystems, and thus, also could make them useful for quantifying the effectiveness of nitrogen, stream, and watershed management efforts.

Algal assessment of threats to freshwater ecosystems: trends, challenges, and opportunities.

The demand on freshwater ecosystem resources and services has increased with human population growth, threatening their quality and sustainability. Many threats to freshwater systems originate from the alteration of watersheds to support growing societal needs for food production, energy, resource extraction, housing, commercial development, and industrial production. The challenge therein is meeting these needs while avoiding or minimizing negative impacts on aquatic ecosystem structure, function, and services. Addressing this challenge requires tools to assess the current and expected conditions of ecosystems and the degree to which they are affected by anthropogenic stressors, such as nutrients, habitat and hydrologic alterations, and acidity. Assessments of the biology, ecology, and ecosystem processes of streams, lakes, and wetlands provide essential information for decisions affecting these resources. Measuring the condition of valued attributes provides quantifiable ecological outcomes and a context for determining stressor severity and the effectiveness of management practices. Protecting high-quality resources (and restoring degraded ones) depends on assessments that identify ecological effects, establish stressor–response relationships, and set management targets. Algae are appealing organisms for use in ecological assessments because they are strong responders to stressors caused by human activities. Changes in algal community structure have ramifications for food webs, biogeochemical cycling, ecosystem services, and human well-being. Technology, statistical analyses, and conceptual approaches to ecological assessments with algae continue to evolve, and recent advancements offer exciting opportunities for improving conservation, management, and restoration of aquatic ecosystems. With this in mind, the following three reviews are the results of a plenary session convened at the 2012 Phycological Society of America meeting, which identified current trends, challenges, and opportunities for using algae to assess freshwater ecosystems. The first review by Manoylov provides a discussion of algal taxonomy and its role in ecological assessments, the second review by Smucker et al. examines current and emerging tools and strategies for assessing streams and restoration effectiveness, and the third by Stevenson establishes an overarching framework and process for implementing ecological assessments and management and proposes strategies for use of algae to support environmental policy and ecosystem services. Each of these complementary reviews (1) examines past and current approaches to ecological assessments, (2) identifies emerging methods, concepts, and technologies for improving future assessments, and (3) highlights how algal sciences can be used to support decisions, designated uses of freshwater resources, and ecosystem services. At the heart of these reviews are the roles algae can play in environmental policy and the management of aquatic ecosystems. Taxonomy is the foundation upon which ecological assessments using algal community attributes are built, and these assessments would not be possible without identifying which taxa are where and in what abundances. Manoylov begins this series of reviews focused on the importance of taxonomy and how approaches to identifying algae affect assessments. Ecological assessments using morphological-based taxonomy of algae have been very effective, but issues with taxonomic expertise, consistency, accuracy, and debatable species concepts exist and can negatively affect assessment outcomes. Manoylov further reviews how these issues affect ecological assessments and examines the performance of species versus genus level taxonomy in metrics, indices, and assessment programs. New technology and advances in molecular-based taxonomy are opening the door to new opportunities for improving consistency and taxa inventories from environmental samples. Although these molecular approaches are still in their infancy, they could further enhance assessments and lead to a better understanding of evolutionary histories and species traits. Communicating ecological results from speciesrich algal communities is important for informing managers, agencies, and decision makers who need to act on well-supported scientific data. Smucker et al. focus on concepts and approaches for using algae in ecological assessments and review how their community structure and functions in streams can be used to assess human impacts and inform management practices. While they concentrated on a specific type of pollution, acid mine drainage (AMD), the approaches they review and the concepts they put forth can be useful to algal assessments of numerous other impacts. A growing body of research shows substantial ecosystem simplification as AMD severity increases, and this is manifested as a loss of species diversity, reduced rates of nutrient cycling and productivity, and less dynamic J. Phycol. 50, 407–408 (2014) Published 2014. This article is a U.S. Government work and is in the public domain in the USA DOI: 10.1111/jpy.12191

Performance of National Maps of Watershed Integrity at Watershed Scales

Watershed integrity, the capacity of a watershed to support and maintain ecological processes essential to the sustainability of services provided to society, can be influenced by a range of landscape and in-stream factors. Ecological response data from four intensively monitored case study watersheds exhibiting a range of environmental conditions and landscape characteristics across the United States were used to evaluate the performance of a national level Index of Watershed Integrity (IWI) at regional and local watershed scales. Using Pearson’s correlation coefficient (r), and Spearman’s rank correlation coefficient (rs), response variables displayed highly significant relationships and were significantly correlated with IWI and ICI (Index of Catchment Integrity) values at all watersheds. Nitrogen concentration and flux-related watershed response metrics exhibited significantly strong negative correlations across case study watersheds, with absolute correlations (|r|) ranging from 0.48 to 0.97 for IWI values, and 0.31 to 0.96 for ICI values. Nitrogen-stable isotope ratios measured in chironomids and periphyton from streams and benthic organic matter from lake sediments also demonstrated strong negative correlations with IWI values, with |r| ranging from 0.47 to 0.92, and 0.35 to 0.89 for correlations with ICI values. This evaluation of the performance of national watershed and catchment integrity metrics and their strong relationship with site level responses provides weight-of-evidence support for their use in state, local and regionally focused applications.