Macroinvertebrates and Fishes as Bioindicators of Stream Water Pollution

Freshwater ecosystems worldwide have been progressively deteriorated during the past decades due to an increasing human pressure that has lead to a decrease in aquatic biodiversity. Among the human activities of high impact on freshwater ecosystems is the land-use change, principally from native forests to agriculture. To evaluate the impacts of human activities on water quality, a traditional approach has considered the use of single physical-chemical parameters. However, this approach may be insufficient to fully assess the impact of these human activities on freshwaters. Therefore, there is a need for alternative tools such as the indices of biotic integrity that may provide a complement to traditional approaches. In the literature, there are several examples of biotic indicators that have shown promising results in evaluating water quality including the use of macroinvertebrates and fish diets. Here, we provide a review of the indicators of biotic integrity that included fish assemblages as well as macroinvertebrates as bioindicators. We identify pros and cons of using aquatic communities as indicators of water quality. Finally, we develop a procedure that combines fish and macroinvertebrate assemblages as bioindicators and discuss their effectiveness using illustrative examples from streams under several agricultural uses in the Mediterranean region of Chile

A Framework to Evaluate Vulnerability of Upriver Migrants to Existing Hydroelectric Infrastructure and Climate Change

River systems have been extensively modified by anthropogenic development of uplands and alterations in flow regimes. These changes reduce the capacity of river floodplains to absorb natural geophysical and environmental changes and directly affect life history adaptations that have developed over the millennia for native species. For example, in western North America changes in upslope processes (i.e. fire regimes, forest harvest and associated managements) work in concert with alterations in natural flow and thermal regimes through dams, levees, and floodplain development to change recovery trajectories of river systems. However, existing phenotypic adaptation by native fishes to environmental conditions may not be compatible with alterations to flow and thermal regimes. Climate change may compound this issue by further reducing variability in environmental conditions, both directly and indirectly, thereby inhibiting the full expression of life history diversity present in current populations. We explored expressed behavioral variability in upriver migration and passage for adult Coho Salmon (Oncorhynchus kisutch), an endangered salmon in Washington and Oregon, USA. We combined long-term records of river flow, water temperature, and upstream fish passage in a single visualization, providing strong empirical foundations for understanding upstream behavioral movement and tolerances of this native salmon. We compared current behavioral variability of Coho Salmon to scenarios representing possible future hydrologic conditions associated with a changing climate. We found that in some locations, the range of environmental conditions in the future is not outside the behavioral variability currently expressed by upstream migrating adult Coho Salmon. However, in some locations, predicted changes in streamflow and temperature occur during times of peak migration and may affect survival of upstream migrants. We discuss management implications and recommendations for action that may expand the capacity of riverscapes to absorb perturbations, thereby allowing for enhanced resilience of native fish populations

Can air temperature be used to project influences of climate change on stream temperature?

Worldwide, lack of data on stream temperature has motivated the use of regression-based statistical models to predict stream temperatures based on more widely available data on air temperatures. Such models have been widely applied to project responses of stream temperatures under climate change, but the performance of these models has not been fully evaluated. To address this knowledge gap, we examined the performance of two widely used linear and nonlinear regression models that predict stream temperatures based on air temperatures. We evaluated model performance and temporal stability of model parameters in a suite of regulated and unregulated streams with 11–44 years of stream temperature data. Although such models may have validity when predicting stream temperatures within the span of time that corresponds to the data used to develop them, model predictions did not transfer well to other time periods. Validation of model predictions of most recent stream temperatures, based on air temperature–stream temperature relationships from previous time periods often showed poor performance when compared with observed stream temperatures. Overall, model predictions were less robust in regulated streams and they frequently failed in detecting the coldest and warmest temperatures within all sites. In many cases, the magnitude of errors in these predictions falls within a range that equals or exceeds the magnitude of future projections of climate-related changes in stream temperatures reported for the region we studied (between 0.5 and 3.0°C by 2080). The limited ability of regression-based statistical models to accurately project stream temperatures over time likely stems from the fact that underlying processes at play, namely the heat budgets of air and water, are distinctive in each medium and vary among localities and through time.Keywords: Temperature biases, Mohseni model, Salmon, Stream temperature, Air temperature, Climate change, Climate projectio

Escaped farmed salmon and trout in Chile: incidence, impacts, and the need for an ecosystem view

The exponential growth of the salmonid farming industry during the last 3 decades has created conditions for massive escapes of these exotic species into natural environments in southern Chile. Here, we review and update information about salmonid escapes from 1993 to 2012 and examine their potential environmental, social, and economic consequences. We estimate that more than 1 million salmonids escape each year from marine farms, mainly due to weather conditions and technical and operational failures of net-pens. While a decrease in the magnitude of escaped Atlantic and coho salmon has occurred during the last several years, escaped rainbow trout have not followed the same pattern. Rainbow trout have become a greater threat to native ecosystems due to their greater potential to establish self-sustaining naturalized populations. The main ecological effects of escapees are related to short-term predatory effects upon native fish, long-term effects linked to the likelihood of farmed salmon establishing self-sustainable populations, and disease and pathogen transfer to native fauna. More research is needed to identify and develop reliable indicators to estimate the impact of escapees at the ecosystem level in both marine and freshwater systems. An understanding of the mechanisms of coexistence between native fishes and introduced non-native salmonids may be useful to design effective management strategies aimed at protecting native fish from salmonid introductions. A precautionary approach that encourages local artisanal and recreational fisheries to counteract colonization and naturalization of salmon species in southern Chile may constitute another management option.KEY WORDS: Fish farming · Salmo salar · Oncorhynchus kisutch · Oncorhynchus mykiss · Exotic specie

Increasing synchrony of high temperature and low flow in western North American streams: double trouble for coldwater biota?

Flow and temperature are strongly linked environmental factors driving ecosystem processes in streams. Stream temperature maxima (T [subscript max_w]) and stream flow minima (Q[subscript min]) can create periods of stress for aquatic organisms. In mountainous areas, such as western North America, recent shifts toward an earlier spring peak flow and decreases in low flow during summer/fall have been reported. We hypothesized that an earlier peak flow could be shifting the timing of low flow and leading to a decrease in the interval between T [subscript max_w] and Q [subscript min]. We also examined if years with extreme low Q [subscript min] were associated with years of extreme high T [subscript max_w]. We tested these hypotheses using long-term data from 22 minimally human-influenced streams for the period 1950-2010. We found trends toward a shorter time lag between (T [subscript max_w] and Q [subscript min] over time and a strong negative association between their magnitudes. Our findings show that aquatic biota may be increasingly experiencing narrower time windows to recover or adapt between these extreme events of low flow and high temperature. This study highlights the importance of evaluating multiple environmental drivers to better gage the effects of the recent climate variability in freshwaters.Keywords: Freshwater ecosystems, Hydrology, Hydroclimatology, Temperature, Climate chang

The paradox of cooling streams in a warming world:Regional climate trends do not parallel variable local trends in stream temperature in the Pacific continental United States

Temperature is a fundamentally important driver of ecosystem processes in streams. Recent warming of terrestrial climates around the globe has motivated concern about consequent increases in stream temperature. More specifically, observed trends of increasing air temperature and declining stream flow are widely believed to result in corresponding increases in stream temperature. Here, we examined the evidence for this using long-term stream temperature data from minimally and highly human-impacted sites located across the Pacific continental United States. Based on hypothesized climate impacts, we predicted that we should find warming trends in the maximum, mean and minimum temperatures, as well as increasing variability over time. These predictions were not fully realized. Warming trends were most prevalent in a small subset of locations with longer time series beginning in the 1950s. More recent series of observations (1987-2009) exhibited fewer warming trends and more cooling trends in both minimally and highly human-influenced systems. Trends in variability were much less evident, regardless of the length of time series. Based on these findings, we conclude that our perspective of climate impacts on stream temperatures is clouded considerably by a lack of long-term data on minimally impacted streams, and biased spatio-temporal representation of existing time series. Overall our results highlight the need to develop more mechanistic, process-based understanding of linkages between climate change, other human impacts and stream temperature, and to deploy sensor networks that will provide better information on trends in stream temperatures in the future. Citation: Arismendi, I., S. L. Johnson, J. B. Dunham, R. Haggerty, and D. Hockman-Wert (2012), The paradox of cooling streams in a warming world: Regional climate trends do not parallel variable local trends in stream temperature in the Pacific continental United States, Geophys. Res. Lett., 39, L10401, doi:10.1029/2012GL051448.Keywords: River temperature, Wildfire tests, Western, Snowpac

Comparing Large-Scale Hydrological Model Predictions with Observed Streamflow in the Pacific Northwest: Effects of Climate and Groundwater

Assessing uncertainties in hydrologic models can improve accuracy in predicting future streamflow. Here, simulated streamflows using the Variable Infiltration Capacity (VIC) model at coarse (1/16°) and fine (1/120°) spatial resolutions were evaluated against observed streamflows from 217 watersheds. In particular, the adequacy of VIC simulations in groundwater- versus runoff-dominated watersheds using a range of flow metrics relevant for water supply and aquatic habitat was examined. These flow metrics were 1) total annual streamflow; 2) total fall, winter, spring, and summer season streamflows; and 3) 5th, 25th, 50th, 75th, and 95th flow percentiles. The effect of climate on model performance was also evaluated by comparing the observed and simulated streamflow sensitivities to temperature and precipitation. Model performance was evaluated using four quantitative statistics: nonparametric rank correlation ρ, normalized Nash–Sutcliffe efficiency NNSE, root-mean-square error RMSE, and percent bias PBIAS. The VIC model captured the sensitivity of streamflow for temperature better than for precipitation and was in poor agreement with the corresponding temperature and precipitation sensitivities derived from observed streamflow. The model was able to capture the hydrologic behavior of the study watersheds with reasonable accuracy. Both total streamflow and flow percentiles, however, are subject to strong systematic model bias. For example, summer streamflows were underpredicted (PBIAS = -13%) in groundwater-dominated watersheds and overpredicted (PBIAS = 48%) in runoff-dominated watersheds. Similarly, the 5th flow percentile was underpredicted (PBIAS = -51%) in groundwater-dominated watersheds and overpredicted (PBIAS = 19%) in runoff-dominated watersheds. These results provide a foundation for improving model parameterization and calibration in ungauged basins.Keywords: Model errors, Hydrologic models, Model evaluation/performanc

Local Variability Mediates Vulnerability of Trout Populations to Land Use and Climate Change

Land use and climate change occur simultaneously around the globe. Fully understanding their separate and combined effects requires a mechanistic understanding at the local scale where their effects are ultimately realized. Here we applied an individual-based model of fish population dynamics to evaluate the role of local stream variability in modifying responses of Coastal Cutthroat Trout (Oncorhynchus clarkii clarkii) to scenarios simulating identical changes in temperature and stream flows linked to forest harvest, climate change, and their combined effects over six decades. We parameterized the model for four neighboring streams located in a forested headwater catchment in northwestern Oregon, USA with multi-year, daily measurements of stream temperature, flow, and turbidity (2007–2011), and field measurements of both instream habitat structure and three years of annual trout population estimates. Model simulations revealed that variability in habitat conditions among streams (depth, available habitat) mediated the effects of forest harvest and climate change. Net effects for most simulated trout responses were different from or less than the sum of their separate scenarios. In some cases, forest harvest countered the effects of climate change through increased summer flow. Climate change most strongly influenced trout (earlier fry emergence, reductions in biomass of older trout, increased biomass of young-of-year), but these changes did not consistently translate into reductions in biomass over time. Forest harvest, in contrast, produced fewer and less consistent responses in trout. Earlier fry emergence driven by climate change was the most consistent simulated response, whereas survival, growth, and biomass were inconsistent. Overall our findings indicate a host of local processes can strongly influence how populations respond to broad scale effects of land use and climate change

A global assessment of freshwater fish introductions in Mediterranean-climate regions

Mediterranean-climate regions (med-regions) are global hotspots of endemism 40 facing mounting environmental threats associated with human-related activities, including the ecological impacts associated with non-native species introductions. We review freshwater fish introductions across med-regions to evaluate the influences of non-native fishes on the biogeography of taxonomic and functional diversity. Our synthesis revealed that 136 freshwater fish species (26 families, 13 orders) have been introduced into med-regions globally. These introductions, and local extirpations, have increased taxonomic and functional faunal similarity among regions by an average of 7.5% (4.6-11.4%; Jaccard) and 7.2% (1.4-14.0%; Bray-Curtis), respectively. Faunal homogenization was highest in Chile and the western Med Basin, whereas sw Cape and the Aegean Sea drainages showed slight differentiation (decrease in faunal similarity) over time. At present, fish faunas of different med-regions have widespread species in common (e.g. Gambusia holbrooki, Cyprinus carpio, Oncorhynchus mykiss, Carassius auratus, and Micropterus salmoides) which are typically large-bodied, non migratory, have higher physiological tolerance, and display fast population growth rates. Our findings suggest that intentional and accidental introductions of freshwater fish have dissolved dispersal barriers and significantly changed the present-day biogeography of med-regions across the globe. Conservation challenges in med-regions include understanding the ecosystem consequences of non-native species at macro-ecological scales.This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by Springer and can be found at: http://link.springer.com/journal/10750.Keywords: Conservation biogeography, Introduced species, Non-native species, Taxonomic homogenization, Functional homogenizatio