Ecological effects of perturbation by drought in flowing waters

Freshwater Biology, Год журнала: 2003, Номер 48(7), С. 1161 - 1172

Опубликована: Июнь 18, 2003

1 Knowledge of the ecology droughts in flowing waters is scattered and fragmentary, with much available information being gathered opportunistically. Studies on intermittent arid-zone streams have provided most information. 2 Drought may be viewed as a disturbance which water inflow, river flow availability fall to extremely low levels for extended periods time. As an ecological perturbation, there drought responses biota drought. 3 Droughts can either periodic, seasonal or supra-seasonal events. The types are presses droughts, ramps. 4 In hydrological connectivity disrupted. Such disruption range from reduction complete loss surface connectivity. longitudinal patterns along where ceases drying up occurs differs between streams. Three outlined: 'downstream drying', 'headwater drying' 'mid-reach drying'. 5 There both direct indirect effects stream ecosystems. Marked include water, habitat aquatic organisms Indirect deterioration quality, alteration food resources, changes strength structure interspecific interactions. 6 marked densities size- age-structure populations, community composition diversity, ecosystem processes. 7 Organisms resist by use refugia. Survival refugia strongly influence capacity recover once they break. 8 Recovery varies markedly droughts. Faunal recovery follows predictable sequences, whilst one case another dense populations transient species depletion that normally occur 9 restoration must provision inclusion long-term regime.

Язык: Английский

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River restoration, habitat heterogeneity and biodiversity: a failure of theory or practice?

Freshwater Biology, Год журнала: 2010, Номер 55(s1), С. 205 - 222

Опубликована: Янв. 1, 2010

Summary 1. Stream ecosystems are increasingly impacted by multiple stressors that lead to a loss of sensitive species and an overall reduction in diversity. A dominant paradigm ecological restoration is increasing habitat heterogeneity (HH) promotes biodiversity. This reflected stream projects through the common practice re‐configuring channels add meanders adding physical structures such as boulders artificial riffles restore biodiversity enhancing structural heterogeneity. 2. To evaluate validity this paradigm, we completed extensive evaluation published studies have quantitatively examined reach‐scale response invertebrate richness actions increased channel complexity/HH. We also evaluated used manipulative or correlative approaches test for relationship between diversity streams were not need restoration. 3. found macroinvertebrate data 78 independent river described 18 different author groups which taxa treatment available. Most successful HH; however, only two showed statistically significant increases rendering them more similar reference reaches sites. 4. Studies manipulating complexity otherwise healthy generally small scale less than half positive with Only one‐third attempted correlate existing levels in‐stream relationship. 5. Across all evaluated, there no evidence HH was primary factor controlling diversity, particularly context. The findings indicate should be driving force selecting most degraded waterways. Evidence suggests much must done simply meanders, boulders, wood, other structures. 6. Thematic implications : integrators activities on land, host including impacts from urbanisation, agriculture, deforestation, invasive species, flow regulation, water extractions mining. these individually combination typically decrease because reduced quality, biologically unsuitable regimes, dispersal barriers, altered inputs organic matter sunlight, habitat, etc. Despite stressors, large number focus primarily characteristics. show wise investment if recovery goal. Managers critically diagnose impacting impaired invest resources first repairing those problems likely limit

Язык: Английский

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The riverine ecosystem synthesis: biocomplexity in river networks across space and time

River Research and Applications, Год журнала: 2006, Номер 22(2), С. 123 - 147

Опубликована: Фев. 1, 2006

Abstract We propose an integrated, heuristic model of lotic biocomplexity across spatiotemporal scales from headwaters to large rivers. This riverine ecosystem synthesis (RES) provides a framework for understanding both broad, often discontinuous patterns along longitudinal and lateral dimensions river networks local ecological various temporal smaller spatial scales. Rather than posing completely new model, we arrange conceptual marriage eco‐geomorphology (ecological aspects fluvial geomorphology) with terrestrial landscape describing hierarchical patch dynamics. modify five components this ecosystems: (1) nested, hierarchies mosaics; (2) dynamics as composite intra‐ inter‐patch dynamics; (3) linked processes; (4) dominance non‐equilibrial stochastic (5) formation quasi‐equilibrial, metastable state. Our blends our perspectives on aquatic models proposed 1980–2004. Contrasting common view rivers continuous, gradients in physical conditions, the RES portrays downstream arrays hydrogeomorphic patches (e.g. constricted, braided floodplain channel areas) formed by catchment geomorphology climate. The distribution these patches, which are identifiable using standard geomorphic techniques, varies amongst is difficult forecast above ecoregional Some types may reoccur passage. Unique ‘functional process zones’ individual because physiochemical habitat differences affect structure function. currently includes 14 tenets predicting how species distributions, community regulation, processes, interactions will vary over scales, especially they relate functional zones network. Copyright © 2006 John Wiley & Sons, Ltd.

Язык: Английский

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State of science: mental workload in ergonomics

Ergonomics, Год журнала: 2014, Номер 58(1), С. 1 - 17

Опубликована: Дек. 2, 2014

Mental workload (MWL) is one of the most widely used concepts in ergonomics and human factors represents a topic increasing importance. Since modern technology many working environments imposes ever more cognitive demands upon operators while physical diminish, understanding how MWL impinges on performance increasingly critical. Yet, also nebulous concepts, with numerous definitions dimensions associated it. Moreover, research has had tendency to focus complex, often safety-critical systems (e.g. transport, process control). Here we provide general overview current state affairs regarding understanding, measurement application design complex over last three decades. We conclude by discussing contemporary challenges for applied research, such as interaction between workload, quantification 'redlines' which specify when are approaching or exceeding their tolerances.

Язык: Английский

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A checklist for ecological management of landscapes for conservation

Ecology Letters, Год журнала: 2007, Номер 11(1), С. 78 - 91

Опубликована: Окт. 10, 2007

Abstract The management of landscapes for biological conservation and ecologically sustainable natural resource use are crucial global issues. Research over two decades has resulted in a large literature, yet there is little consensus on the applicability or even existence general principles broad considerations that could guide landscape conservation. We assess six major themes ecology landscapes. identify 13 important issues need to be considered developing approaches They include recognizing importance mosaics (including integration terrestrial aquatic areas), interactions between vegetation cover configuration, using an appropriate conceptual model, maintaining capacity recover from disturbance managing adaptive framework. These influenced by context, species assemblages goals do not translate directly into on‐the‐ground guidelines but they should recognized researchers managers when specific cases. Two overarching are: (i) clearly articulated vision (ii) quantifiable objectives offer unambiguous signposts measuring progress.

Язык: Английский

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Linking ecological theory with stream restoration

Freshwater Biology, Год журнала: 2007, Номер 52(4), С. 597 - 615

Опубликована: Март 2, 2007

Summary 1. Faced with widespread degradation of riverine ecosystems, stream restoration has greatly increased. Such is rarely planned and executed inputs from ecological theory. In this paper, we seek to identify principles theory that have been, or could be, used guide restoration. 2. attempts re‐establish populations, knowledge the species’ life history, habitat template spatio‐temporal scope critical. many cases dispersal will be a critical process in maintaining viable populations at landscape scale, special attention should given unique geometry systems 3. One way by which organisms survive natural disturbances use refugia, forms may been lost degradation. Restoring refugia therefore survival target particularly facilitating resilience ongoing anthropogenic disturbance regimes. 4. connectivity, especially longitudinal major goal. restoring lateral connectivity there an increasing awareness riparian zone as transition between streams their catchments. 5. Increased food web structure – bottom‐up versus top‐down control, trophic cascades subsidies are yet applied efforts. 6. restoration, species drawn regional pool. Having overcome environmental constraints (filters), persistence governed local internal dynamics, referred assembly rules. 7. While projects often define goals endpoints, succession pathways mechanisms (e.g. facilitation) these achieved considered. This occurs spite large body general on draw. 8. Stream neglected ecosystem processes. The concept biodiversity increases functioning very relevant Whether affects processes, such decomposition, equivocal. 9. Considering spatial scale success. Success more likely large‐scale projects, but they infeasible terms available resources conflicts interest. Small‐scale remedy specific problems. general, occur appropriate not reversed prevailing regime. 10. effectiveness predictability improve increased understanding processes ecosystems develop maintained. Ideas can clearly better incorporated into projects. provide twofold benefit providing opportunity both outcomes test

Язык: Английский

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The role of refugia for fishes during drought: a review and synthesis

Freshwater Biology, Год журнала: 2003, Номер 48(7), С. 1186 - 1198

Опубликована: Июнь 18, 2003

Summary Drought is a natural disturbance of aquatic ecosystems and can be major factor in structuring communities. For individuals, populations communities to persist disturbed environments, they must have refuge from or minimal. Refugia convey spatial temporal resistance resilience the face disturbance, but role refugia systems remains poorly understood. 2. We review available literature on for fishes order synthesise current knowledge provide suggestions needed research. Our objectives were clarify definitions context drought systems, how habitats influence fish community structure, consider potential impact population dynamics during drought. 3. Droughts cause decrease surface area/volume an increase extremes physical chemical water quality parameters. These conditions are linked with biotic interactions that structure residing low‐flow dry season by increasing mortality rates, decreasing birth rates and/or migration rates. Many organisms seek adaptations (e.g. physiological tolerance) refuge. 4. leads shifts spacing connectance at multiple scales. Refuge size, intensity, mobility predicted play large persistence. expect will experience net immigration drying emigration after rewetting, opposite occurring surrounding habitat patches. Population using best modelled modified source‐sink dynamics, likely change scale.

Язык: Английский

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Parallels and contrasts in the effects of drought on stream macroinvertebrate assemblages

Freshwater Biology, Год журнала: 2003, Номер 48(7), С. 1173 - 1185

Опубликована: Июнь 18, 2003

Summary It is axiomatic that unusually long dry periods (droughts) adversely affect aquatic biota. Recovery after drought rapid by macroinvertebrates possess strategies to survive drying or are highly mobile but other taxa take longer recolonise depending on the timing, intensity, and duration of phase. Although acts as a sustained ‘ramp’ disturbance, impacts may be disproportionately severe when certain critical thresholds exceeded. For example, ecological changes gradual while riffle dries cessation flow causes abrupt loss specific habitat, alteration physicochemical conditions in pools downstream, fragmentation river ecosystem. Many responses within these habitats apparently depend timing rapidity hydrological transitions across thresholds, exhibiting ‘stepped’ response alternating between change threshold approached followed swift transition habitat disappears fragmented. In two Australian intermittent streams, eliminated decimated several groups macroinvertebrates, including atyid shrimps, stoneflies free‐living caddisflies. These persisted during early stages did not recruit successfully following year, despite return higher‐than‐baseflow conditions. This ‘lag effect’ emphasises value long‐term survey data. faunal composition were inconsistent among sites, marked shifts richness, abundance trophic organisation dried provide evidence for stepped response. Responses macroinvertebrate assemblages droughts differing severity English chalk streams variable. The prolonged 1988–92 had greater impact than shorter 1970s recovery over next 3 years was swift. Effects 1995 summer buffered groundwater discharge from previous winter. tended reduce available riverine habitats, especially via siltation, few because they could perennial sections streams. contrasting environments studied England Australia, there parallels rates recolonisation. However, recruitment lack desiccation‐resistant have limited mobility delayed. Currently, data systems insufficient indicate persistent effects predict excessive surface abstraction increased frequency expected with global climate change.

Язык: Английский

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A framework for assessing ecosystem dynamics in response to chronic resource alterations induced by global change

Ecology, Год журнала: 2009, Номер 90(12), С. 3279 - 3289

Опубликована: Дек. 1, 2009

In contrast to pulses in resource availability following disturbance events, many of the most pressing global changes, such as elevated atmospheric carbon dioxide concentrations and nitrogen deposition, lead chronic often cumulative alterations available resources. Therefore, predicting ecological responses these will require modification existing disturbance‐based frameworks. Here, we present a conceptual framework for assessing nature pace change under alterations. The “hierarchical‐response framework” (HRF) links well‐documented, mechanisms provide theoretical basis testing hypotheses explain dynamics differential sensitivity ecosystems HRF is based on temporal hierarchy beginning with individual (physiological/metabolic) responses, followed by species reordering within communities, finally loss immigration. Each mechanism hypothesized differ magnitude rate its effects ecosystem structure function, this variation depending attributes, longevity dominant species, rates biogeochemical cycling, levels biodiversity, trophic complexity. Overall, predicts nonlinear changes dynamics, expectation that interactions natural disturbances other global‐change drivers further alter change. explicitly comparative better understand sensitivities ecosystems, it can be used guide design coordinated, cross‐site experiments enable more robust forecasts contemporary future dynamics.

Язык: Английский

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Reviews and syntheses: Effects of permafrost thaw on Arctic aquatic ecosystems

Biogeosciences, Год журнала: 2015, Номер 12(23), С. 7129 - 7167

Опубликована: Дек. 8, 2015

Abstract. The Arctic is a water-rich region, with freshwater systems covering about 16 % of the northern permafrost landscape. Permafrost thaw creates new ecosystems, while at same time modifying existing lakes, streams, and rivers that are impacted by thaw. Here, we describe current state knowledge regarding how affects lentic (still) lotic (moving) systems, exploring effects both thermokarst (thawing collapse ice-rich permafrost) deepening active layer (the surface soil thaws refreezes each year). Within thermokarst, further differentiate between in lowland areas vs. on hillslopes. For almost all processes explore, vary regionally, lake stream systems. Much this regional variation caused differences ground ice content, topography, type, coverage. Together, these factors determine (i) degree to which manifests as (ii) whether leads slumping or formation (iii) manner constituent delivery altered Differences thaw-enabled can be considerable, determining, for example, balance particulate dissolved constituents, inorganic organic materials. Changes composition thaw-impacted waters, coupled changes morphology, strongly affect physical optical properties lakes. ecology lakes streams also likely change; have unique microbiological communities, show respiration, primary production, food web structure largely driven sediment, matter, nutrient delivery. enables matter morphology stratification characteristics recipient will play an important role determining release greenhouse gases (CO2 CH4), its burial sediments, loss downstream. magnitude impacts aquatic ecosystems increasing, prevalence streams. There therefore urgent need quantify affecting across diverse landscapes, implications change climate warming.

Язык: Английский

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