Flow Management for Hydropower Extirpates Aquatic Insects, Undermining River Food Webs

Kennedy, James A.; Muehlbauer, Jeffrey D.; Yackulic, Charles B.; Lytle, David A.; Miller, Scott W.; Dibble, Kimberly L.; Kortenhoeven, Eric W.; Metcalfe, Anya N.; Baxter, Colden V.

doi:10.1093/biosci/biw059

Cited by 159 publications

(144 citation statements)

References 56 publications

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“…) and that the insect community that humpback chub depend on lacks diversity due in part to chronic impacts of dam operations on insect populations (Kennedy et al. ). Understanding the relative importance of other drivers is important because managing them may be less controversial and more cost effective.…”

Section: Discussionmentioning

confidence: 99%

Inferring species interactions through joint mark–recapture analysis

Yackulic

Korman²,

Yard

et al. 2018

Ecology

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Introduced species are frequently implicated in declines of native species. In many cases, however, evidence linking introduced species to native declines is weak. Failure to make strong inferences regarding the role of introduced species can hamper attempts to predict population viability and delay effective management responses. For many species, mark-recapture analysis is the more rigorous form of demographic analysis. However, to our knowledge, there are no mark-recapture models that allow for joint modeling of interacting species. Here, we introduce a two-species mark-recapture population model in which the vital rates (and capture probabilities) of one species are allowed to vary in response to the abundance of the other species. We use a simulation study to explore bias and choose an approach to model selection. We then use the model to investigate species interactions between endangered humpback chub (Gila cypha) and introduced rainbow trout (Oncorhynchus mykiss) in the Colorado River between 2009 and 2016. In particular, we test hypotheses about how two environmental factors (turbidity and temperature), intraspecific density dependence, and rainbow trout abundance are related to survival, growth, and capture of juvenile humpback chub. We also project the long-term effects of different rainbow trout abundances on adult humpback chub abundances. Our simulation study suggests this approach has minimal bias under potentially challenging circumstances (i.e., low capture probabilities) that characterized our application and that model selection using indicator variables could reliably identify the true generating model even when process error was high. When the model was applied to rainbow trout and humpback chub, we identified negative relationships between rainbow trout abundance and the survival, growth, and capture probability of juvenile humpback chub. Effects on interspecific interactions on survival and capture probability were strongly supported, whereas support for the growth effect was weaker. Environmental factors were also identified to be important and in many cases stronger than interspecific interactions, and there was still substantial unexplained variation in growth and survival rates. The general approach presented here for combining mark-recapture data for two species is applicable in many other systems and could be modified to model abundance of the invader via other modeling approaches.

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Section: Discussionmentioning

confidence: 99%

Inferring species interactions through joint mark–recapture analysis

Yackulic

Korman²,

Yard

et al. 2018

Ecology

Self Cite

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“…At finer scales, hydropeaking produces much finer‐scale unnaturally variable fluctuations on the daily scale, which can have major negative effects on riverine biota (Kennedy et al. ). While older dams are increasingly being decommissioned in the developed world, the scale of new dam projects worldwide is immense, both in developed and developing countries (Zarfl et al.…”

Section: Generalizing the Approachmentioning

confidence: 99%

Seasonality and predictability shape temporal species diversity

Tonkin

Bogan

Bonada

et al. 2017

Ecology

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254

286

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Temporal environmental fluctuations, such as seasonality, exert strong controls on biodiversity. While the effects of seasonality are well known, the predictability of fluctuations across years may influence seasonality in ways that are less well understood. The ability of a habitat to support unique, non-nested assemblages of species at different times of the year should depend on both seasonality (occurrence of events at specific periods of the year) and predictability (the reliability of event recurrence) of characteristic ecological conditions. Drawing on tools from wavelet analysis and information theory, we developed a framework for quantifying both seasonality and predictability of habitats, and applied this using global long-term rainfall data. Our analysis predicted that temporal beta diversity should be maximized in highly predictable and highly seasonal climates, and that low degrees of seasonality, predictability, or both would lower diversity in characteristic ways. Using stream invertebrate communities as a case study, we demonstrated that temporal species diversity, as exhibited by community turnover, was determined by a balance between temporal environmental variability (seasonality) and the reliability of this variability (predictability). Communities in highly seasonal mediterranean environments exhibited strong oscillations in community structure, with turnover from one unique community type to another across seasons, whereas communities in aseasonal New Zealand environments fluctuated randomly. Understanding the influence of seasonal and other temporal scales of environmental oscillations on diversity is not complete without a clear understanding of their predictability, and our framework provides tools for examining these trends at a variety of temporal scales, seasonal and beyond. Given the uncertainty of future climates, seasonality and predictability are critical considerations for both basic science and management of ecosystems (e.g., dam operations, bioassessment) spanning gradients of climatic variability.

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“…Torrente-Vilara et al (2011) showed that waterfalls have greater effects than seasonal variations of water level on fish assemblage structure, whereas in diatoms the relative influence of environment versus barrier differed among seasons (Liu et al, 2013). On the stream/river scale, indirect effects of artificial barriers such as dams have been extensively studied and turned out to be profound by disintegrating whole ecosystems (Greathouse et al, 2006;Kennedy et al, 2016). Few studies exist that examine mollusk communities explicitly, this is especially true for regional or supraregional scales.…”

Section: Combined Influence Of Environment Dispersal and The Indirementioning

confidence: 99%

Mollusk communities of the central Congo River shaped by combined effects of barriers, environmental gradients, and species dispersal

et al. 2017

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Rapids, falls, and cascades might act as barriers for freshwater species, determining the species community up-and downstream of barriers. However, they affect community composition not only by acting as barriers but also by their influence on environmental gradients. Moreover, the directional dispersal of species along the watercourse might determine community composition. A suitable system to study these differential effects is the Congo River, the world's second largest river by discharge. The small 'Upper Congo Rapids' ecoregion features several rapids known as barrier for fish. The Wagenia Cataract at the town of Kisangani constitutes the strongest drop of the Congo River and several studies have emphasized its role as barrier for fish distribution. Alternative explanations for this pattern, however, are rarely evaluated. Though mollusks represent a vital component of the macrozoobenthos, with distribution patterns and underlying drivers often distinct from that of fishes, virtually no field surveys of the Congo River have been reported for decades. We collected and determined mollusks of 51 stations, recorded environmental conditions, and generated proxies for directional species dispersal and an indirect barrier effect. Those variables were subjected to distance-based redundancy analyses and variation partitioning in order to test whether the mollusk community compositions are better explained by an individual or combined influence of the direct and indirect effect of the cataract barrier, environmental conditions, and downstreamdirected dispersal. Our survey showed an exclusive upstream/downstream distribution for just four out of the 19 species, suggesting a limited barrier effect. We revealed no direct influence of the barrier itself on community composition but of substrate type. However, we found an indirect effect of the barrier through replacing spatially structured communities upstream of the cataract with more uniform ones downstream. Downstream-directed dispersal explained the highest fraction of variation in mollusk communities. Thus, environmental factors, the indirect cataract effect, and downstream-directed spatial proxies model mollusk community composition in concert. These results support previous studies showing a multi-factorial imprint on communities. However, a large fraction of variation community composition remained unexplained, potentially due to flood plain dynamics that (re-)shape mollusk communities constantly and a high temporal turnover, evidenced by the comparison with historical surveys. This is likely caused by the growth of Kisangani and resulting human activities. A monitoring system could allow better assessments of these impacts on communities and the conservation status of endemic species in the Wagenia Cataract.

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Flow Management for Hydropower Extirpates Aquatic Insects, Undermining River Food Webs

Cited by 159 publications

References 56 publications

Inferring species interactions through joint mark–recapture analysis

Inferring species interactions through joint mark–recapture analysis

Seasonality and predictability shape temporal species diversity

Mollusk communities of the central Congo River shaped by combined effects of barriers, environmental gradients, and species dispersal

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