Rivers in temperate ecoregions
– Indicators for Climate Change Impacts –
Interactions between Climate Change, other stressors and the biota are complex. What are the main impacts? Which simple parameters are suited to detect them?
Here we suggest indicators, which reflect the main effects of Climate Change on freshwater ecosystems.
Within the Euro-Limpacs consortium there is an ongoing discussion about the best suited indicators. On this page you find a first selection, which will frequently be updated and improved within 2008.
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Small rivers
Biological parameters
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"Potamalization" - effects on invertebrates
Climate Region Temperate Ecosystem type Small rivers Stressor type Temperature Responding parameter group Biological parameters Responding parameter "Potamalization" - effects on invertebrates Response description
Besides current velocity, water temperature is the most relevant environmental variable for stream invertebrates. Higher water temperature lead to the disappearance of species adapted to cold water temperature and the associated high oxygen content, e.g. several stonefly (Plecoptera) species. They are replaced by species typical for warmer water previously colonizing more downstream reaches. Thus, invertebrate species typical for small streams ("rhithral") will be replaced by species from larger rivers ("potamal").
Secondary effects
Food availability for top predators (fish) changes.
Specification of relevant ecosystem type
Relevant for all small rivers in temperate ecoregions.
Relevant ecoregion(s) according to Illies
Pyrenees (2), Alps (4), Western Mountains (8), Central Mountains (9), Carpathians (10)
Suggested indicator
Share of invertebrate taxa preferring the metarhithral (trout zone)
Justification of indicator
Benthic invertebrates are routinely monitored in most European countries. The response of the invertebrate community to temperature increase is reflected by their longitudinal zonation preference. The share of "metarhithral taxa" in an unimpacted small stream differs between ecoregions, but should typically be around 50%.
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Decline of species number
Climate Region Temperate Ecosystem type Small rivers Stressor type Temperature Responding parameter group Biological parameters Responding parameter Decline of species number Response description
Increasing water temperatures lead to the extinction of cold stenothermic taxa, which are particularly species rich in small mountain streams.
Secondary effects
Eurythermic species will dominate stream sections, which were formerly dominated by cold-stenothermic species.
Specification of relevant ecosystem type
Relevant for all small rivers in temperate ecoregions.
Relevant ecoregion(s) according to Illies
Pyrenees (2), Alps (4), Western Mountains (8), Central Mountains (9), Carpathians (10)
Suggested indicator
Water temperature (maximum and minimum monthly values); Share of cold-stenothermic species
Justification of indicator
Cold stenothermic species are sensitive particularly against water temperature in summer.
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Increase of algae growth rates
Climate Region Temperate Ecosystem type Small rivers Stressor type Temperature Responding parameter group Biological parameters Responding parameter Increase of algae growth rates Response description
With increasing water temperatures, growth of benthic algae will stop later in autumn and start earlier in spring.
Secondary effects
Increased food availability for grazers in the macroinvertebrate community. Increased grazer abundance.
Specification of relevant ecosystem type
Relevant for all small rivers in temperate ecoregions.
Relevant ecoregion(s) according to Illies
Central Lowlands (14), Western Lowlands (13), Western Mountains (8), Central Mountains (9)
Suggested indicator
Water temperature (maximum and minimum monthly values) in winter
Justification of indicator
Algae growth in winter is inhibited by water temperatures.
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Increase of r-strategists
Climate Region Temperate Ecosystem type Small rivers Stressor type Hydrology / Morphology Responding parameter group Biological parameters Responding parameter Increase of r-strategists Response description
Invertebrate r-strategists benefit from unpredictable flood events, e.g. in summer, which remove most invertebrates and thus favour species rapidly colonising the competition-free space.
Secondary effects
Disappearance of stenotopic species.
Specification of relevant ecosystem type
Relevant for all small rivers in temperate ecoregions.
Relevant ecoregion(s) according to Illies
Pyrenees (2), Alps (4), Western Mountains (8), Central Mountains (9), Carpathians (10)
Suggested indicator
Number and discharge or flood events in unusual seasons (recorded by gauging stations)
Justification of indicator
Unusual hydrological events e.g. floods in summer cause catastrophic drifts of invertebrate species and favour r-strategists.
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Reduced water quality
Climate Region Temperate Ecosystem type Small rivers Stressor type Temperature Responding parameter group Biological parameters Responding parameter Reduced water quality Response description
Increasing water temperatures enhances production and decomposition intensity, thus leading to oxygen depletion, particularly at night times.
Secondary effects
Organism groups and species sensitive to oxygen depletion will disappear.
Specification of relevant ecosystem type
Relevant for all small rivers in temperate ecoregions.
Relevant ecoregion(s) according to Illies
Central Lowlands (14), Western Lowlands (13), Western Mountains (8), Central Mountains (9)
Suggested indicator
Saprobic indices
Justification of indicator
Saprobic indices reflect the organic load in streams and eventually the oxygen content. Thus, if the organic load increases the saprobic indices will decrease. Species with a high oxygen demand respectively low saprobic value will disappear while species with a low oxygen demand respectively high saprobic value will benefit.
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Replacement of cold-stenothermic by eurythermic species
Climate Region Temperate Ecosystem type Small rivers Stressor type Temperature Responding parameter group Biological parameters Responding parameter Replacement of cold-stenothermic by eurythermic species Response description
Higher temperatures will favour eurythermic species in formerly cold water habitats.
Secondary effects
The cold-stenothermic species are threatened by warmer water temperatures.
Specification of relevant ecosystem type
Relevant for all small rivers in temperate ecoregions.
Relevant ecoregion(s) according to Illies
Pyrenees (2), Alps (4), Western Mountains (8), Central Mountains (9), Carpathians (10)
Suggested indicator
Water temperature (minimum monthly values)
Justification of indicator
Minimum temperature is a key survival factor. The tolerance of low temperatures decides about the presence and the absence of a species in a certain habitat.
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Replacement of salmonid by cyprinid fish species
Climate Region Temperate Ecosystem type Small rivers Stressor type Temperature Responding parameter group Biological parameters Responding parameter Replacement of salmonid by cyprinid fish species Response description
Higher water temperatures will reduce reproductive success of salmonid species and increase parasitic and predator pressure on the egg and young larval stages. Warm water cyprinid species will invade in cold water regions.
Secondary effects
Food webs will change if salmonid species as main predators of macroinvertebrates will be reduced.
Specification of relevant ecosystem type
Relevant for all small rivers in temperate ecoregions.
Relevant ecoregion(s) according to Illies
Pyrenees (2), Alps (4), Western Mountains (8), Central Mountains (9), Carpathians (10)
Suggested indicator
Water temperature (maximum and minimum monthly values); fish species composition.
Justification of indicator
The eggs of salmonid species need high oxygen concentrations which will be reduced by higher water temperatures. Parasites and fungi benefit of high temperatures.
Reference(s)
Hari, R., D.M. Livingstone, R. Siber, P. Burkhardt-Holm & H. Güttinger (2005): Consequences of climate change for water temperature and brown trout populations in Alpine river and streams. Global Change Biology 11: 1-17.
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Spread of alien species
Climate Region Temperate Ecosystem type Small rivers Stressor type Temperature Responding parameter group Biological parameters Responding parameter Spread of alien species Response description
Higher temperatures often favour alien species that increasingly colonize small streams. These could be alien fish, macrophyte or macroinvertebrate species.
Secondary effects
Strong competitions with native species.
Specification of relevant ecosystem type
Relevant for all small rivers in temperate ecoregions.
Relevant ecoregion(s) according to Illies
Central Lowlands (14), Western Lowlands (13), Western Mountains (8), Central Mountains (9)
Suggested indicator
Water temperature (maximum and minimum monthly values); Share of alien species in the community
Justification of indicator
The survival and reproduction of several alien species in temperate ecoregions is controlled by minimum temperatures. The second parameter can often be inferred from routine monitoring for the Water Framework Directive.
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Hydromorphological parameters
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Increase in drought frequency and duration
Climate Region Temperate Ecosystem type Small rivers Stressor type Hydrology / Morphology Responding parameter group Hydromorphological parameters Responding parameter Increase in drought frequency and duration Response description
Decreased summer precipitation and increasing air temperature in some parts of Central and Eastern Europe change the character of several small streams from permanent to temporary.
Secondary effects
Macrophyte, fish and invertebrate communities will change to drought resistant species.
Specification of relevant ecosystem type
Relevant for all small rivers in temperate continental ecoregions.
Relevant ecoregion(s) according to Illies
Central Lowlands (14), Eastern Lowlands (16)
Suggested indicator
Drought periods
Justification of indicator
As gauging stations are not installed in most small headwater streams, drought periods can be easily recorded by visiting the respective streams.
Reference(s)
Arnell, N.W. & N.S. Reynard (1996): The effects of climate change due to global warming on river flows in Great Britain. Journal of Hydrology 183: 397-424.
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Increased fine sediment entry
Climate Region Temperate Ecosystem type Small rivers Stressor type Hydrology / Morphology Responding parameter group Hydromorphological parameters Responding parameter Increased fine sediment entry Response description
Extreme precipitation events increase surface runoff and lead to large amounts of fine sediments entering the streams; sediments accumulate and clogg the bottom interstitial.
Secondary effects
Oxygen depletion in the interstitial and on the channel bottom will affect benthic organisms and fish eggs.
Specification of relevant ecosystem type
Relevant for all small rivers in temperate ecoregions.
Relevant ecoregion(s) according to Illies
Central Lowlands (14), Western Lowlands (13), Western Mountains (8), Central Mountains (9)
Suggested indicator
Number and discharge or flood events in unusual seasons (recorded by gauging stations)
Justification of indicator
Extreme precipitation events will wash out fine sediments from adjacent cropland. They are well reflected by the discharge of a river.
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Reduced availability of leaves
Climate Region Temperate Ecosystem type Small rivers Stressor type Hydrology / Morphology Responding parameter group Hydromorphological parameters Responding parameter Reduced availability of leaves Response description
Processing rates of leafs and wood increase with temperature. Floods in winter cause more than 50% of the leaf inputs to be exported, leaving little detrital material available for invertebrate consumption. In consequence, coarse particulate organic matter availability to shredders will decrease during the summer months.
Secondary effects
Decreasing abundance of shredders will limit the food source of predators (e.g. fishes).
Specification of relevant ecosystem type
Relevant for all small rivers in temperate continental ecoregions.
Relevant ecoregion(s) according to Illies
Central Lowlands (14), Western Lowlands (13), Western Mountains (8), Central Mountains (9)
Suggested indicator
Share of the feeding type "shredder" in the invertebrate community
Justification of indicator
Benthic invertebrates are routinely monitored in most European countries. If the availability of leaves decreases the share of shredders will decrease, too; in small headwater streams shredders should typically account for 30-40 % of the invertebrate community.
Reference(s)
Buzby, K.M. & S.A. Perry (2000): Modeling the potential effects of climate change on leaf pack processing in central Appalachian streams. Canadian Journal of Fisheries and Aquatic Sciences 57(9): 1773-1783.
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Physico-chemical parameters
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"Potamalization" - effects on nutrients
Climate Region Temperate Ecosystem type Small rivers Stressor type Temperature Responding parameter group Physico-chemical parameters Responding parameter "Potamalization" - effects on nutrients Response description
Higher water temperatures lead to a more rapid mineralisation of organic matter (leafs, wood) and thus to eutrophication effects. As a result, small streams ("rhithral") will change character and resemble larger rivers ("potamal").
Secondary effects
Increased availability of N and P; increased growth of algae, oxygen depletion during night times, and isappearance of species sensitive to oxygen depletion such as brown trout (Salmo trutta).
Specification of relevant ecosystem type
Relevant for all small rivers in temperate ecoregions.
Relevant ecoregion(s) according to Illies
Pyrenees (2), Alps (4), Western Mountains (8), Central Mountains (9), Carpathians (10)
Suggested indicator
Water temperature (maximum monthly values)
Justification of indicator
The response of communities is mainly determined by extremes; secondary effects (e.g. oxygen depletion at night times) are most extreme in summer.
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Large rivers
Biological parameters
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Decline of species number
Climate Region Temperate Ecosystem type Large rivers Stressor type Temperature Responding parameter group Biological parameters Responding parameter Decline of species number Response description
Increasing water temperatures lead to the extinction of cold stenothermic taxa, which are particularly species rich in small mountain streams.
Secondary effects
Eurythermic species will dominate stream sections, which were formerly dominated by cold-stenothermic species.
Specification of relevant ecosystem type
Relevant for all large rivers in temperate ecoregions.
Relevant ecoregion(s) according to Illies
Pyrenees (2), Alps (4), Western Mountains (8), Central Mountains (9), Carpathians (10)
Suggested indicator
Water temperature (maximum and minimum monthly values); Share of cold-stenothermic species
Justification of indicator
Cold stenothermic species are sensitive particularly against water temperature in summer.
Reference(s)
Xenopoulos, M.A., D.M. Lodge, J. Alcamo, M. Märker, K. Schulze & D.P. van Vuuren (2005): Scenarios of freshwater fish extinctions from climate change and water withdrawal. Global Change Biology 11 (10): 1557-1564.
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Increase of r-strategists
Climate Region Temperate Ecosystem type Large rivers Stressor type Hydrology / Morphology Responding parameter group Biological parameters Responding parameter Increase of r-strategists Response description
Invertebrate r-strategists benefit from unpredictable flood events, e.g. in summer, which remove most invertebrates and thus favour species rapidly colonising the competition-free space.
Secondary effects
Disappearance of stenotopic species.
Specification of relevant ecosystem type
Relevant for all largerivers in temperate ecoregions.
Relevant ecoregion(s) according to Illies
Pyrenees (2), Alps (4), Western Mountains (8), Central Mountains (9), Carpathians (10)
Suggested indicator
Number and discharge or flood events in unusual seasons (recorded by gauging stations)
Justification of indicator
Unusual hydrological events e.g. floods in summer cause catastrophic drifts of invertebrate species and favour r-strategists.
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Increased macrophytes growth
Climate Region Temperate Ecosystem type Large rivers Stressor type Temperature Responding parameter group Biological parameters Responding parameter Increased macrophytes growth Response description
Macrophyte growth rates increase due to higher temperatures and prolonged vegetation period.
Secondary effects
Dammed and unshaded stream reaches will experience high macrophyte biomass. Fish and macroinvertebrate species bound to macrophyte stands will increase.
Specification of relevant ecosystem type
Relevant for all large rivers in temperate ecoregions.
Relevant ecoregion(s) according to Illies
Central Lowlands (14), Western Lowlands (13), Western Mountains (8), Central Mountains (9)
Suggested indicator
Water temperature (maximum and minimum monthly values); degree of shading
Justification of indicator
Water temperature is a key factor enhancing macrophyte growth. ; Degree of shading well reflects light availability.
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Reduced water quality
Climate Region Temperate Ecosystem type Large rivers Stressor type Temperature Responding parameter group Biological parameters Responding parameter Reduced water quality Response description
Increasing water temperatures enhances production and decomposition intensity, thus leading to oxygen depletion, particularly at night times.
Secondary effects
Organism groups and species sensitive to oxygen depletion will disappear.
Specification of relevant ecosystem type
Relevant for all large rivers in temperate ecoregions.
Relevant ecoregion(s) according to Illies
Central Lowlands (14), Western Lowlands (13), Western Mountains (8), Central Mountains (9)
Suggested indicator
Saprobic indices
Justification of indicator
Saprobic indices reflect the organic load in streams and eventually the oxygen content. Thus, if the organic load increases the saprobic indices will decrease. Species with a high oxygen demand respectively low saprobic value will disappear while species with a low oxygen demand respectively high saprobic value will benefit.
Reference(s)
Bultot, F., D. Gellens, M. Spreafico & B. Schädler (1992): Repercussions of a CO2 doubling on the water balance - a case study in Switzerland. Journal of Hydrology 137: 199-208.
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Replacement of salmonid by cyprinid fish species
Climate Region Temperate Ecosystem type Large rivers Stressor type Temperature Responding parameter group Biological parameters Responding parameter Replacement of salmonid by cyprinid fish species Response description
Higher water temperatures will reduce reproductive success of salmonid species and increase parasitic and predator pressure on the egg and young larval stages. Warm water cyprinid species will invade in cold water regions.
Secondary effects
Food webs will change if salmonid species as main predators of macroinvertebrates will be reduced.
Specification of relevant ecosystem type
Relevant for all large rivers in temperate ecoregions.
Relevant ecoregion(s) according to Illies
Pyrenees (2), Alps (4), Western Mountains (8), Central Mountains (9), Carpathians (10)
Suggested indicator
Water temperature (maximum and minimum monthly values)
Justification of indicator
The eggs of salmonid species need high oxygen concentrations which will be reduced by higher water temperatures. Parasites and fungi benefit of high temperatures.
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Replacement of salmonid by cyprinid fish species
Climate Region Temperate Ecosystem type Large rivers Stressor type Temperature Responding parameter group Biological parameters Responding parameter Replacement of salmonid by cyprinid fish species Response description
Higher water temperatures will reduce reproductive success of salmonid species and increase parasitic and predator pressure on the egg and young larval stages. Warm water cyprinid species will invade in cold water regions.
Secondary effects
Food webs will change as salmonid and cyprinid fish species prefer different food sources.
Specification of relevant ecosystem type
Replacement of salmonid by cyprinid fish species
Relevant ecoregion(s) according to Illies
Pyrenees (2), Alps (4), Western Mountains (8), Central Mountains (9), Carpathians (10)
Suggested indicator
Fish species composition
Justification of indicator
In natural systems the percentage of cold water species (mainly salmonids) is high and the percentage of warm water species (mainly cyprinids) is low; this will change with increasing temperature.
Reference(s)
Daufresne, M., M. C. Roger, H. Capra & N. Lamouroux (2004): Long-term changes within the invertebrate and fish communities of the upper Rhône river: effects of climatic factors. Glob. Change Biol. 10: 124 - 140.
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Spread of alien species
Climate Region Temperate Ecosystem type Large rivers Stressor type Temperature Responding parameter group Biological parameters Responding parameter Spread of alien species Response description
Higher temperatures often favour alien species that increasingly colonize small streams. These could be alien fish, macrophyte or macroinvertebrate species.
Secondary effects
Strong competitions with native species.
Specification of relevant ecosystem type
Relevant for all large rivers in temperate ecoregions.
Relevant ecoregion(s) according to Illies
Central Lowlands (14), Western Lowlands (13), Western Mountains (8), Central Mountains (9)
Suggested indicator
Water temperature (maximum and minimum monthly values)
Justification of indicator
The survival and reproduction of several alien species in temperate ecoregions is controlled by minimum temperatures.
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Hydromorphological parameters
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Restructuring of channel features (sedimentation/erosion)
Climate Region Temperate Ecosystem type Large rivers Stressor type Hydrology / Morphology Responding parameter group Hydromorphological parameters Responding parameter Restructuring of channel features (sedimentation/erosion) Response description
Extreme precipitation events increase sediment entry from riverine cropland into the river, altering the composition of the bottom substrates. In channelized rivers sediment is relocated much faster than in natural rivers.
Secondary effects
Catastrophic drift due to flooding and relocation of sediments will diminish macroinvertebrate communities.
Specification of relevant ecosystem type
Relevant for all large rivers in temperate ecoregions.
Relevant ecoregion(s) according to Illies
Pyrenees (2), Alps (4), Western Mountains (8), Central Mountains (9), Carpathians (10), Central Lowlands (14), Western Lowlands (13)
Suggested indicator
Share of fine sediment (sand, silt) at the river bottom.
Justification of indicator
The share of fine sediment (sand silt) at the river bottom is simple to record, e.g. by transect measurements.
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Unpredictable flood events
Climate Region Temperate Ecosystem type Large rivers Stressor type Hydrology / Morphology Responding parameter group Hydromorphological parameters Responding parameter Unpredictable flood events Response description
Extreme precipitation events will cause more frequent flash floods in channelized river systems.
Secondary effects
Frequent remobilisation of bottom substrates and of the biota.
Specification of relevant ecosystem type
Relevant for all large rivers in temperate ecoregions.
Relevant ecoregion(s) according to Illies
Central Lowlands (14), Western Lowlands (13), Western Mountains (8), Central Mountains (9)
Suggested indicator
Number and discharge or flood events in unusual seasons (recorded by gauging stations)
Justification of indicator
The discharge of most large rivers is already monitored with gauging stations.
Reference(s)
Graham, L.P. (2004): Climate change effects on river flow to the Baltic Sea. Ambio 33 (4-5): 235-241.
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Physico-chemical parameters
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Mobilisation of toxic substances
Climate Region Temperate Ecosystem type Large rivers Stressor type Hydrology / Morphology Responding parameter group Physico-chemical parameters Responding parameter Mobilisation of toxic substances Response description
Extreme precipitation events lead to inundation of former mining and deposition zones, mobilising toxic substances (heavy metals, POPs) stored in the bottom substrate.
Secondary effects
Enhanced concentration of toxic substances and respective consequences for biota and drinking water quality.
Specification of relevant ecosystem type
Relevant for all large rivers in temperate ecoregions.
Relevant ecoregion(s) according to Illies
Central Lowlands (14), Western Lowlands (13)
Suggested indicator
Concentration of toxic substances, e.g. heavy metals.
Justification of indicator
Several “priority substances” are already routinely monitored for the purpose of the Water Framework Directive.
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Oxygen depletion
Climate Region Temperate Ecosystem type Large rivers Stressor type Temperature Responding parameter group Physico-chemical parameters Responding parameter Oxygen depletion Response description
Higher water temperatures lead to increased phytobenthos and macrophyte growth and to oxygen depletion at night times.
Secondary effects
Fish kills may occur in oxygen depleted waters.
Specification of relevant ecosystem type
Relevant for all large rivers in temperate ecoregions.
Relevant ecoregion(s) according to Illies
Central Lowlands (14), Western Lowlands (13)
Suggested indicator
Oxygen contents (minimum daily values)
Justification of indicator
Oxygen contents are routinely monitored at a large number of sites. Oxygen contents below 50% are critical for most aquatic species.
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