Lakes in warm ecoregions

– Case studies  –

Hundreds, if not thousands, of recently published papers are dealing with the impact of Climate Change on freshwater ecosystems.

Here you find summaries of a few hundred papers, which we consider as most relevant.

• Shallow

  Abiotic indicators

  • Nutrients: N-/P-flux; eutrophication general / Jeppesen, E., Meerhoff, M., Jakobsen, B.A., H ...

    Climate Region	warm
    Ecosystem type	shallow
    Parameter group	Abiotic indicators
    Indicator	Nutrients: N-/P-flux; eutrophication general

    Reference

    Jeppesen, E., Meerhoff, M., Jakobsen, B.A., Hansen, R.S., Søndergaard, M., Jensen, J.P., Lauridsen, T.L., Mazzeo, N., Branco, C. (2007): Restoration of shallow lakes by nutrient control and biomanipulation?the successful strategy varies with lake size and climate. Hydrobiologia 581(1): 269-285.

    Description

    Major efforts have been made world-wide to improve the ecological quality of shallow lakes by reducing external nutrient loading. These have often resulted in lower in-lake total phosphorus (TP) and decreased chlorophyll a levels in surface water, reduced phytoplankton biomass and higher Secchi depth. Internal loading delays recovery, but in north temperate lakes a new equilibrium with respect to TP often is reached after p<10-15 years. In comparison, the response time to reduced nitrogen (N) loading is typically p<5 years. Also increased top-down control may be important. Fish biomass often declines, and the percentage of piscivores, the zooplankton:phytoplankton biomass ratio, the contribution of Daphnia to zooplankton biomass and the cladoceran size all tend to increase. This holds for both small and relatively large lakes, for example, the largest lake in Denmark (40 km^{2), shallow Lake Arresø, has responded relatively rapidly to a ca. 76% loading reduction arising from nutrient reduction and top-down control. Some lakes, however, have proven resistant to loading reductions. To accelerate recovery several physico-chemical and biological restoration methods have been developed for north temperate lakes and used with varying degrees of success. Biological measures, such as selective removal of planktivorous fish, stocking of piscivorous fish and implantation or protection of submerged plants, often are cheap versus traditional physico-chemical methods and are therefore attractive. However, their long-term effectiveness is uncertain. It is argued that additional measures beyond loading reduction are less cost-efficient and often not needed in very large lakes. Although fewer data are available on tropical lakes these seem to respond to external loading reductions, an example being Lake Paranoá, Brazil (38 km2). However, differences in biological interactions between cold temperate versus warm temperate-subtropical-tropical lakes make transfer of existing biological restoration methods to warm lakes difficult. Warm lakes often have prolonged growth seasons with a higher risk of long-lasting algal blooms and dense floating plant communities, smaller fish, higher aggregation of fish in vegetation (leading to loss of zooplankton refuge), more annual fish cohorts, more omnivorous feeding by fish and less specialist piscivory. The trophic structures of warm lakes vary markedly, depending on precipitation, continental or coastal regions locations, lake age and temperature. Unfortunately, little is known about trophic dynamics and the role of fish in warm lakes. Since many warm lakes suffer from eutrophication, new insights are needed into trophic interactions and potential lake restoration methods, especially since eutrophication is expected to increase in the future owing to economic development and global warming.}

• Early warning indicators

  • Clear water timing / Straile, D. (2002): ...

    Climate Region	humid warm
    Ecosystem type	shallow
    Parameter group	Early warning indicators
    Indicator	Clear water timing

    Reference

    Straile, D. (2002): North Atlantic Oscillation synchronizes food-web interactions in central European lakes. Proceedings of the Royal Society of London 269: 391-395.

    Description

    Higher water temperature (esp. winter/spring). Timing of early summer algal suppression (clear water timing) advanced by approx. 2 weeks within the last 30 years. Faster population growth of herbivores (i.e. Daphnia) due to warmer water.

  • Ice cover timing / Weyhenmeyer, G.A., M. Meili & D.M. Living ...

    Climate Region	humid warm
    Ecosystem type	shallow
    Parameter group	Early warning indicators
    Indicator	Ice cover timing

    Reference

    Weyhenmeyer, G.A., M. Meili & D.M. Livingstone (2004): Non-linear response of ice-breakup. Geophysical Research Letters 31(7): 1-4.

    Description

    Long-term records (4 decades). Lake ice phenology: Potentially important for employment of lake ice phenologies as climate indicators. Relationship between air temperature and timing of lake ice breakup shows arc cosine function. Nonlinearity results in marked differences in the response of timing in ice breakup to changes in air temperature between colder and warmer regions and cold.

• Food webs

  • Pico-, nanoplankton, epilithon / Christoffersen, K., N. Andersen, M. Sø ...

    Climate Region	humid warm
    Ecosystem type	shallow
    Parameter group	Food webs
    Indicator	Pico-, nanoplankton, epilithon

    Reference

    Christoffersen, K., N. Andersen, M. Søndergaard, L. Liboriussen &, E. Jeppesen (2006): Implications of climate-enforced temperature increases on freshwater pico- and nanoplankton populations studied in artificial ponds during 16 months. Hydrobiologia 560: 259-266.

    Description

    Generally, the results showed that the abundances of picoalgae, bacteria and heterotrophic nanoflagellates changed in a similar manner over time; abundances being lower in winter than in summer. Warming in itself had no effect on abundance, albeit it significantly modified the positive effect of the nutrients. Only at ambient temperatures did the whole microbial assemblage respond positively to nutrients. In the A2 scenario, only picoalgae responded to nutrients, while in the A2+ scenario all but the heterotrophic nanoflagellates showed a response. Elevated winter temperatures seemed not to be more important for the microbial assemblage than elevated summer temperatures. Our results demonstrate that the direct effects of warming were far less important than the nutrient effect. The results furthermore reveal that warming and nutrients in combination set off complex interactions. In consequence, global warming may possibly have pronounced effects on aquatic ecosystems if accompanied by increased nutrient loading.

• Primary production

  • Abundance nano-, picoplankton / Christoffersen, K., N. Andersen, M. Sø ...

    Climate Region	humid warm
    Ecosystem type	shallow
    Parameter group	Primary production
    Indicator	Abundance nano-, picoplankton

    Reference

    Christoffersen, K., N. Andersen, M. Søndergaard, L. Liboriussen &, E. Jeppesen (2006): Implications of climate-enforced temperature increases on freshwater pico- and nanoplankton populations studied in artificial ponds during 16 months. Hydrobiologia 560: 259-266.

    Description

    Generally, the results showed that the abundances of picoalgae, bacteria and heterotrophic nanoflagellates changed in a similar manner over time; abundances being lower in winter than in summer. Warming in itself had no effect on abundance, albeit it significantly modified the positive effect of the nutrients. Only at ambient temperatures did the whole microbial assemblage respond positively to nutrients. In the A2 scenario, only picoalgae responded to nutrients, while in the A2+ scenario all but the heterotrophic nanoflagellates showed a response. Elevated winter temperatures seemed not to be more important for the microbial assemblage than elevated summer temperatures. Our results demonstrate that the direct effects of warming were far less important than the nutrient effect. The results furthermore reveal that warming and nutrients in combination set off complex interactions. In consequence, global warming may possibly have pronounced effects on aquatic ecosystems if accompanied by increased nutrient loading.

  • Makrophytes, community, distribution, production / Rooney, N. & J. Kalff (2000): ...

    Climate Region	humid warm
    Ecosystem type	shallow
    Parameter group	Primary production
    Indicator	Makrophytes, community, distribution, production

    Reference

    Rooney, N. & J. Kalff (2000): Inter-annual variation in submerged macrophyte community biomass and distribution: the influence of temperature and lake morphometry. Aquatic Botany 68: 321-335.

    Description

    Primary Production:Interannual variation in underwater light climate: No effect on macrophyte colonization. Early season warm temperatures: deeper macrophyte colonization, greater wet weight biomass, increase in whole lake biomass. This effect is most pronounced in eutrophic shallow lake systems, not applicable to deeper systems.

    Early Warning Indicators - Water temperature: Increased air temperature: Warmer surface temperatures in all lakes. Clear lakes: volume of cold water reduced (<10 °C). Colored lakes (DOC > 4 mg/l): cold water volume stable resp. Increased

    Early Warning Indicators - Stratification characteristics: Shallower mixing depths, stronger thermal gradient in metalimnion in all lakes.

• Primary production: plants / Secondary production - fish

  • Community change, diversity change / Fish distribution, richness, abundance change / Meerhoff, M., Clemente, J.M., Teixeira de Mel ...

    Climate Region	warm
    Ecosystem type	shallow
    Parameter group	Primary production: plants / Secondary production - fish
    Indicator	Community change, diversity change / Fish distribution, richness, abundance change

    Reference

    Meerhoff, M., Clemente, J.M., Teixeira de Mello, F., Iglesias, C., Pedersen, A.R., Jeppesen, E. (2007): Can warm climate-related structure of littoral predator assemblies weaken clear water state in shallow lakes? Global Change Biology 13: 1888-1897.

    Description

    Shallow lakes, the most abundant lake type in the world, are very sensitive to climatic changes. The structure and functioning of shallow lakes are greatly impacted by submerged plants, and these may be affected by climate warming in various, contrasting, ways. Following a space-for-time substitution approach, we aimed to analyse the role of aquatic (submerged and free-floating) plants in shallow lakes under warm climates. We introduced artificial submerged and free-floating plant beds in five comparable lakes located in the temperate zone (Denmark, 55-57 °N) and in the subtropical zone (Uruguay, 30-35 °S), with the aim to study the structure and dynamics of the main associated communities.Regardless of differences in environmental variables, such as area, water transparency and nutrient status, we found consistent patterns in littoral community dynamics and structure (i.e. densities and composition of fish, zooplankton, macroinvertebrates, and periphyton) within, but substantial differences between, the two regions. Subtropical fish communities within the macrophyte beds exhibited higher diversity, higher density, smaller size, lower relative abundance of potentially piscivores, and a preference for submerged plants, compared with otherwise similar temperate lakes. By contrast, macroinvertebrates and cladocerans had higher taxon richness and densities, and periphyton higher biomass, in the temperate lakes. Several indicators suggest that the fish predation pressure was much stronger among the plants in the subtropical lakes. The antipredator behaviour of cladocerans also differed significantly between climate zones. Submerged and free-floating plants exerted different effects on the spatial distribution of the main communities, the effects differing between the climate zones. In the temperate lakes, submerged plants promoted trophic interactions with potentially positive cascading effects on water transparency, in contrast to the free-floating plants, and in strong contrast to the findings in the subtropical lakes.The higher impact of fish may result in higher sensitivity of warm lakes to external changes (e.g. increase in nutrient loading or water level changes). The current process of warming, particularly in temperate lakes, may entail an increased sensitivity to eutrophication, and a threat to the high diversity, clear water state.

• Secondary production - fish

  • Phyto- and Zooplankton production change / Moss, B., Stephen, D., Balayla, D.M., Becares ...

    Climate Region	arid warm
    Ecosystem type	shallow
    Parameter group	Secondary production - fish
    Indicator	Phyto- and Zooplankton production change

    Reference

    Moss, B., Stephen, D., Balayla, D.M., Becares, E., Collings,S.E., Fernández Aláez, C., Fernández Aláez, M., Ferriol, C., García, P., Gomá, J., Gyllström, M., Hansson, L-A., Hietala, J., Kairesalo, T., Miracle, M.R., Romo, S., Rueda, J., Russell, V., Stahl-Delbanco, A., Svensson, M., Vakkilainen, K., Valentín, M., Van De Bund, W.J., Van Donk, E., Vicente, E., Villena, M.J. (2004): Continental-scale patterns of nutrient and fish effects on shallow lakes: synthesis of a pan-European mesocosm experiment. Freshwater Biology 49: 1633-1649. (Euro-limpacs paper)

    Description

    1. Results are analysed from 11 experiments in which effects of fish addition and nutrient loading on shallow lakes were studied in mesocosms. The experiments, five in 1998, six in 1999, were carried out in six lakes, distributed from Finland to southern Spain, according to a standard protocol. 2. Effects of the treatments on 29 standard chemical, phytoplankton and zooplankton variables are examined to assess the relative importance of bottom-up (nutrient enrichment) and top-down (fish predation) effects. For each year, the experiments in different locations are treated as replicates in a meta-analysis. Results of individual experiments are then compared in terms of the patterns of significant influences of nutrient addition and fish predation with these overall results (the baseline), and between years in the same location. 3. The overall meta-analysis gave consistent results across the 2 years, with nutrient loading influencing all of the chemical variables, and on average 31% of primary producer and 39% of zooplankton variables. In contrast, fish influenced none of the chemical variables, 11% of the primary producer and 44% of the zooplankton variables. Nutrient effects on the system were thus about three times greater than fish effects, although fish effects were not inconsiderable. 4. The relative importance of nutrients and fish in individual experiments often differed between years at the same location and effects deviated to varying degrees from the baseline. These deviations were treated as measures of consistency (predictability) of conclusions in repeat experiments. Consistency increased southwards and this is interpreted as a consequence of more variable annual weather northwards. 5. The influence of nutrient loading was greater southwards and this was probably manifested through naturally greater annual macrophyte abundance in warmer locations in consequence of the longer plant growing-season. There was no trend in the relative importance of fish effects with latitude but this may partly be an artefact of the simple fish community used. These findings suggest that nutrient control should be a greater priority than biomanipulation in the restoration of eutrophicated shallow lakes in warm temperate regions. 6. Starting conditions affected the outcome of experiments. High initial concentrations of total phosphorus and planktonic chlorophyll a concentration (created by local conditions prior to the experiment) led to de-emphasis of the importance of nutrient loading in the experiment.

• Secondary production - fish

  • Phyto- and Zooplankton production change / Moss, B., Stephen, D., Balayla, D.M., Becares ...

    Climate Region	warm
    Ecosystem type	shallow
    Parameter group	Secondary production - fish
    Indicator	Phyto- and Zooplankton production change

    Reference

    Moss, B., Stephen, D., Balayla, D.M., Becares, E., Collings,S.E., Fernández Aláez, C., Fernández Aláez, M., Ferriol, C., García, P., Gomá, J., Gyllström, M., Hansson, L-A., Hietala, J., Kairesalo, T., Miracle, M.R., Romo, S., Rueda, J., Russell, V., Stahl-Delbanco, A., Svensson, M., Vakkilainen, K., Valentín, M., Van De Bund, W.J., Van Donk, E., Vicente, E., Villena, M.J. (2004): Continental-scale patterns of nutrient and fish effects on shallow lakes: synthesis of a pan-European mesocosm experiment. Freshwater Biology 49: 1633-1649.

    Description

    1. Results are analysed from 11 experiments in which effects of fish addition and nutrient loading on shallow lakes were studied in mesocosms. The experiments, five in 1998, six in 1999, were carried out in six lakes, distributed from Finland to southern Spain, according to a standard protocol.
    2. Effects of the treatments on 29 standard chemical, phytoplankton and zooplankton variables are examined to assess the relative importance of bottom-up (nutrient enrichment) and top-down (fish predation) effects. For each year, the experiments in different locations are treated as replicates in a meta-analysis. Results of individual experiments are then compared in terms of the patterns of significant influences of nutrient addition and fish predation with these overall results (the baseline), and between years in the same location.
    3. The overall meta-analysis gave consistent results across the 2 years, with nutrient loading influencing all of the chemical variables, and on average 31% of primary producer and 39% of zooplankton variables. In contrast, fish influenced none of the chemical variables, 11% of the primary producer and 44% of the zooplankton variables. Nutrient effects on the system were thus about three times greater than fish effects, although fish effects were not inconsiderable.
    4. The relative importance of nutrients and fish in individual experiments often differed between years at the same location and effects deviated to varying degrees from the baseline. These deviations were treated as measures of consistency (predictability) of conclusions in repeat experiments. Consistency increased southwards and this is interpreted as a consequence of more variable annual weather northwards.
    5. The influence of nutrient loading was greater southwards and this was probably manifested through naturally greater annual macrophyte abundance in warmer locations in consequence of the longer plant growing-season. There was no trend in the relative importance of fish effects with latitude but this may partly be an artefact of the simple fish community used. These findings suggest that nutrient control should be a greater priority than biomanipulation in the restoration of eutrophicated shallow lakes in warm temperate regions.
    6. Starting conditions affected the outcome of experiments. High initial concentrations of total phosphorus and planktonic chlorophyll a concentration (created by local conditions prior to the experiment) led to de-emphasis of the importance of nutrient loading in the experiment.

• Secondary production - zooplankton

  • Abundance nano-, picoplankton / Christoffersen, K., N. Andersen, M. Sø ...

    Climate Region	humid warm
    Ecosystem type	shallow
    Parameter group	Secondary production - zooplankton
    Indicator	Abundance nano-, picoplankton

    Reference

    Christoffersen, K., N. Andersen, M. Søndergaard, L. Liboriussen &, E. Jeppesen (2006): Implications of climate-enforced temperature increases on freshwater pico- and nanoplankton populations studied in artificial ponds during 16 months. Hydrobiologia 560: 259-266.

    Description

    Generally, the results showed that the abundances of picoalgae, bacteria and heterotrophic nanoflagellates changed in a similar manner over time; abundances being lower in winter than in summer. Warming in itself had no effect on abundance, albeit it significantly modified the positive effect of the nutrients. Only at ambient temperatures did the whole microbial assemblage respond positively to nutrients. In the A2 scenario, only picoalgae responded to nutrients, while in the A2+ scenario all but the heterotrophic nanoflagellates showed a response. Elevated winter temperatures seemed not to be more important for the microbial assemblage than elevated summer temperatures. Our results demonstrate that the direct effects of warming were far less important than the nutrient effect. The results furthermore reveal that warming and nutrients in combination set off complex interactions. In consequence, global warming may possibly have pronounced effects on aquatic ecosystems if accompanied by increased nutrient loading.

  • Biomass / Shuter, B.J. & K.K. Ing (1997): ...

    Climate Region	humid warm
    Ecosystem type	shallow
    Parameter group	Secondary production - zooplankton
    Indicator	Biomass

    Reference

    Shuter, B.J. & K.K. Ing (1997): Factors affecting the production of zooplankton in lakes. Canadian Journal of Fisheries and Aquatic Sciences 54(2): 359-377.

    Description

    76 % of the observed variation in growing season weight-specific production rates could be accounted for by differences in temperature, length of growing season, and taxonomic group (Rotifera, Chydoroidea, Cyclopoida, Calanoida, ordered from highest rate to lowest). Within taxonomic groups, effects of population biomass density, individual body size, and food availability were not detected. 58% of the observed variation in growing season population biomass density could be accounted for by differences in individual body size, mean chlorophyll concentration, and lake mean depth. 24% of the observed variation in growing season length could be accounted for by differences in mean chlorophyll concentration and taxonomic group. Our findings suggest a simple model of the seasonal production cycle for limnetic zooplankton in which weight-specific rates of biomass production are largely set by temperature, and levels of biomass accumulation are largely set by food resource availability and individual body size. We briefly discuss the implications of this model for predicting the effects of climate change on lake productivity.

  • Population timing, growth, maximum / Straile, D. (2002): ...

    Climate Region	humid warm
    Ecosystem type	shallow
    Parameter group	Secondary production - zooplankton
    Indicator	Population timing, growth, maximum

    Reference

    Straile, D. (2002): North Atlantic Oscillation synchronizes food-web interactions in central European lakes. Proceedings of the Royal Society of London 269: 391-395.

    Description

    Higher water temperature (esp. winter/spring). Timing of early summer algal suppression (clear water timing) advanced by approx. 2 weeks within the last 30 years. Faster population growth of herbivores (i.e. Daphnia) due to warmer water.

• Secondary production - zooplankton

  • Zooplankton biomass, diversity, composition change / Gyllström, M., Hansson, L.A., Jeppesen, ...

    Climate Region	warm
    Ecosystem type	shallow
    Parameter group	Secondary production - zooplankton
    Indicator	Zooplankton biomass, diversity, composition change

    Reference

    Gyllström, M., Hansson, L.A., Jeppesen, E., García-Criado, F., Gross, E., Irvine, K., Kairesalo, T., Kornijow, R., Miracle, M.R., Nykänen, M., Nõges, T., Romo, S., Stephen, D., Van Donk, E., Moss, B. (2005): The role of climate in shaping zooplankton communities of shallow lakes. Limnology & Oceanography 50(6): 2008-2021.

    Description

    We analyzed data from 81 shallow European lakes, which were sampled with standardized methods, for combined effects of climatic, physical, and chemical features of food-web interactions, with a specific focus on zooplankton biomass and community structure. Multiple-regression analysis showed that total phosphorus (TP) generally was the most important predictor of zooplankton biomass and community structure. Climate was the next most important predictor and acted mainly through its effect on pelagic zooplankton taxa. Benthic and plant-associated taxa (typically almost half the total zooplankton biomass) were, however, affected mainly by macrophyte coverage. Neither climate nor TP affected the relation between small and large taxa, and we found only a weak trend with increasing TP of increasing mean crustacean body mass. Dividing the data set into three climate zones revealed a pronounced difference in response to lake productivity between cold lakes, with long periods of ice cover, and the two warmer lake types. These "ice" lakes differed from the others with respect to the effect of TP on chlorophyll a, the zooplankton : chlorophyll a ratio, the chlorophyll a :TP ratio, and the proportion of cyclopoids in the copepod community. Our data suggest that bottom-up forces, such as nutrient concentration, are the most important predictors of zooplankton biomass. In addition, climate contributes significantly-possibly by affecting top-down regulation by fish-and may interact with productivity in determining the zooplankton standing biomass and community composition. Hence, the present study suggests that food-web dynamics are closely linked to climatic features.

  • Zooplankton biomass, diversity, composition change / Meerhoff, M., Iglesias, C., Teixeira de Mello ...

    Climate Region	warm
    Ecosystem type	shallow
    Parameter group	Secondary production - zooplankton
    Indicator	Zooplankton biomass, diversity, composition change

    Reference

    Meerhoff, M., Iglesias, C., Teixeira de Mello, F., Clemente, J.M., Jensen E., Lauridsen, T.L., Jeppesen, E. (2007): Effects of habitat complexity on community structure and predator avoidance behaviour of littoral zooplankton in temperate versus subtropical shallow lakes. Freshwater Biology 52: 1009-1021.

    Description

    1. Structural complexity may stabilise predator-prey interactions and affect the outcome of trophic cascades by providing prey refuges. In deep lakes, vulnerable zooplankton move vertically to avoid fish predation. In contrast, submerged plants often provide a diel refuge against fish predation for large-bodied zooplankton in shallow temperate lakes, with consequences for the whole ecosystem.
    2. To test the extent to which macrophytes serve as refuges for zooplankton in temperate and subtropical lakes, we introduced artificial plant beds into the littoral area of five pairs of shallow lakes in Uruguay (30°-35°S) and Denmark (55°-57°N). We used plants of different architecture (submerged and free-floating) along a gradient of turbidity over which the lakes were paired.
    3. We found remarkable differences in the structure (taxon-richness at the genus level, composition and density) of the zooplankton communities in the littoral area between climate zones. Richer communities of larger-bodied taxa (frequently including Daphnia spp.) occurred in the temperate lakes, whereas small-bodied taxa characterised the subtropical lakes. More genera and a higher density of benthic/plant-associated cladocerans also occurred in the temperate lakes. The density of all crustaceans, except calanoid copepods, was significantly higher in the temperate lakes (c. 5.5-fold higher).
    4. Fish and shrimps (genus Palaemonetes) seemed to exert a stronger predation pressure on zooplankton in the plant beds in the subtropical lakes, while the pelagic invertebrate Chaoborus sp. was slightly more abundant than in the temperate lakes. In contrast, plant associated predatory macroinvertebrates were eight times more abundant in the temperate than in the subtropical lakes.
    5. The artificial submerged plants hosted significantly more cladocerans than the freefloating plants, which were particularly avoided in the subtropical lakes. Patterns indicating diel horizontal migration were frequently observed for both overall zooplankton density and individual taxa in the temperate, but not the subtropical, lakes. In contrast, patterns of diel vertical migration prevailed for both the overall zooplankton and for most individual taxa in the subtropics, irrespective of water turbidity.
    6. Higher fish predation probably shapes the general structure and dynamics of cladoceran communities in the subtropical lakes. Our results support the hypothesis that horizontal migration is less prevalent in the subtropics than in temperate lakes, and that no predator avoidance behaviour effectively counteracts predation pressure in the subtropics. Positive effects of aquatic plants on water transparency, via their acting as a refuge for zooplankton, may be generally weak or rare in warm lakes.
• 
  

  Lakes in general

  Abiotic indicators

  • Acidification: import (wetlands) / Aherne, J., Larssen, T., Dillon, P.J. & B ...

    Climate Region	humid warm
    Ecosystem type	lakes in general
    Parameter group	Abiotic indicators
    Indicator	Acidification: import (wetlands)

    Reference

    Aherne, J., Larssen, T., Dillon, P.J. & B.J. Cosby (2004): Effects of climate events on environmental fluxes from forested catchments in Ontario, Canada: Modelling drought-induced redox processes. Water, Air and Soil Pollution: Focus 4: 37-48.

    Description

    Application of MAGIC model (biogeochemical model of acidification) in comparison to observed trends: Model reproduced successfully observed trends in sulphate retention. Including wetlands. Variation in precipitation. Drought periods: Oxidation of stored sulphur in wetlands, subsequent efflux into streams/lakes. Generation of wetland compartment with incorporated redox processes included in MAGIC model.

  • Acidification: release sediment / Vesely, J., V. Majer, J. Kopácek, J. & ...

    Climate Region	humid warm
    Ecosystem type	lakes in general
    Parameter group	Abiotic indicators
    Indicator	Acidification: release sediment

    Reference

    Vesely, J., V. Majer, J. Kopácek, J. & S.A. Norton (2003): Increasing temperature decreases aluminum concentrations in Central European lakes recovering from acidification. Limnology and Oceanography 48(6): 2346-2354.

    Description

    Increasing temperature over 17 yr-period (1984-2001) (+1.27 ±0.49 °C). Decrease of total Al and Al³⁺ concentrations in lakes (Inverse relationship between temperature and solubility: lower mobilization and/or enhanced precipitation).

  • Nutrients: eutrophication general / Evans, C.D., D.T. Monteith & D.M. Cooper ...

    Climate Region	humid warm
    Ecosystem type	lakes in general
    Parameter group	Abiotic indicators
    Indicator	Nutrients: eutrophication general

    Reference

    Evans, C.D., D.T. Monteith & D.M. Cooper (2005): Long-term increases in surface water dissolved organic carbon: Observations, possible causes and environmental impacts. Environmental Pollution 137(1): 55-71.

    Description

    Rising temperatures in combination with declining acid deposition may be the cause for increasing DOC concentrations. May have impacts on freshwater biota, drinking water quality, coastal marine ecosystems, upland carbon balances.

  • Thermocline depth / McCormick, M.J. (1990): ...

    Climate Region	humid warm
    Ecosystem type	lakes in general
    Parameter group	Abiotic indicators
    Indicator	Thermocline depth

    Reference

    McCormick, M.J. (1990): Potential changes in thermal structure and cycle of Lake Michigan due to global warming. Transactions of the American Fisheries Society 119: 183-194.

    Description

    Earlier onset of stratification, season increases by up to two months. Stronger stratification, less energy for large-scale vertical mixing. No full turnover in most winters leads to permanent thermocline in deeper regions (below shallow seasonal thermocline). Elevated summer and winter heat contents, summer increase less than winter increase.

  • Thermocline depth, nutrients: depletion and general eutrophication / Schindler, D.W., S.E. Bayley, B.R. Parker, K. ...

    Climate Region	humid warm
    Ecosystem type	lakes in general
    Parameter group	Abiotic indicators
    Indicator	Thermocline depth, nutrients: depletion and general eutrophication

    Reference

    Schindler, D.W., S.E. Bayley, B.R. Parker, K.G. Beaty, D.R. Cruikshank, E.J. Fee, E.U. Schindler & M.P. Stainton (1996): The effects of climatic warming on the properties of boreal lakes and streams at the Experimental Lakes Area, northwestern Ontario. Limnology and Oceanography 41(5): 1004-1017.

    Description

    Higher water temperatures, deeper thermoclines, higher alkalinities, higher concentrations of base cations and nitrogen, lower DOC, silica and P. Increased phytoplankton biomass. Habitats for cold stenotherms reduced slightly. Increased water retention.

• Early warning indicators

  • Clear water timing / Straile, D. (2002): ...

    Climate Region	humid warm
    Ecosystem type	lakes in general
    Parameter group	Early warning indicators
    Indicator	Clear water timing

    Reference

    Straile, D. (2002): North Atlantic Oscillation synchronizes food-web interactions in central European lakes. Proceedings of the Royal Society of London 269: 391-395.

    Description

    Higher water temperature (esp. winter/spring). Timing of early summer algal suppression (clear water timing) advanced by approx. 2 weeks within the last 30 years. Faster population growth of herbivores (i.e. Daphnia) due to warmer water.

  • Ice cover timing / Weyhenmeyer, G.A., M. Meili & D.M. Living ...

    Climate Region	humid warm
    Ecosystem type	lakes in general
    Parameter group	Early warning indicators
    Indicator	Ice cover timing

    Reference

    Weyhenmeyer, G.A., M. Meili & D.M. Livingstone (2004): Non-linear response of ice-breakup. Geophysical Research Letters 31(7): 1-4.

    Description

    Long-term records (4 decades). Lake ice phenology: Potentially important for employment of lake ice phenologies as climate indicators. Relationship between air temperature and timing of lake ice breakup shows arc cosine function. Nonlinearity results in marked differences in the response of timing in ice breakup to changes in air temperature between colder and warmer regions and cold.

  • Water temperature, mixis timing/type change / Strub, P.T., T. Powell & C.R. Goldman (19 ...

    Climate Region	humid warm
    Ecosystem type	lakes in general
    Parameter group	Early warning indicators
    Indicator	Water temperature, mixis timing/type change

    Reference

    Strub, P.T., T. Powell & C.R. Goldman (1985): Climatic forcing: Effects of El Niño on a small, temperate lake. Science 227: 55-57.

    Description

    Earlier/later mixing, anomalously large/small heat storage (max heat content August) below mixed layer.

  • Water temperature, stratification characteristics / McCormick, M.J. (1990): ...

    Climate Region	humid warm
    Ecosystem type	lakes in general
    Parameter group	Early warning indicators
    Indicator	Water temperature, stratification characteristics

    Reference

    McCormick, M.J. (1990): Potential changes in thermal structure and cycle of Lake Michigan due to global warming. Transactions of the American Fisheries Society 119: 183-194.

    Description

    Earlier onset of stratification, season increases by up to two months. Stronger stratification, less energy for large-scale vertical mixing. No full turnover in most winters leads to permanent thermocline in deeper regions (below shallow seasonal thermocline). Elevated summer and winter heat contents, summer increase less than winter increase.

• Food webs

  • Uncoupling food chains, timing mismatch, loss of top predators / Petchey, O.L., P.T. McPhearson, T.M. Casey &a ...

    Climate Region	humid warm
    Ecosystem type	lakes in general
    Parameter group	Food webs
    Indicator	Uncoupling food chains, timing mismatch, loss of top predators

    Reference

    Petchey, O.L., P.T. McPhearson, T.M. Casey & P.J. Morin (1999): Environmental warming alters food-web structure and ecosystem function. Nature 402: 69-72.

    Description

    Disproportionate loss of top predators and herbivores, dominance of autotrophs and bacterivores. Zoogeographical boundaries could move 500-600 km north. Growth and production increases for fish in colder than optimum habitats. Decrease of growth and production for fish at or above thermal optimum.

• Primary production

  • Cold water species: changed distribution/extinction, bacterioplankton / Schindler, D.W., S.E. Bayley, B.R. Parker, K. ...

    Climate Region	humid warm
    Ecosystem type	lakes in general
    Parameter group	Primary production
    Indicator	Cold water species: changed distribution/extinction, bacterioplankton

    Reference

    Schindler, D.W., S.E. Bayley, B.R. Parker, K.G. Beaty, D.R. Cruikshank, E.J. Fee, E.U. Schindler & M.P. Stainton (1996): The effects of climatic warming on the properties of boreal lakes and streams at the Experimental Lakes Area, northwestern Ontario. Limnology and Oceanography 41(5): 1004-1017.

    Description

    Higher water temperatures, deeper thermoclines, higher alkalinities, higher concentrations of base cations and nitrogen, lower DOC, silica and P. Increased phytoplankton biomass. Habitats for cold stenotherms reduced slightly. Increased water retention.

  • Phytoplankton maximum, blooms timing / Weyhenemeyer, G.A., T. Bleckner & K. Pett ...

    Climate Region	humid warm
    Ecosystem type	lakes in general
    Parameter group	Primary production
    Indicator	Phytoplankton maximum, blooms timing

    Reference

    Weyhenemeyer, G.A., T. Bleckner & K. Pettersson (1999): Changes of the plankton spring outburst related to the North Atlantic Oscillation. Limnology and Oceanography 44(7): 1788-1792.

    Description

    North Atlantic Oscillation: long-term variability strongly related to changes in timing and composition of phytoplankton spring peaks. Regional parameters as ice-breakup and nutrient concentrations no stronger relation than NAO.

• Secondary production - fish

  • Distribution range change (thermal habitat) / Carpenter, S.R., Fisher, S.G., Grimm, N.B. &a ...

    Climate Region	humid warm
    Ecosystem type	lakes in general
    Parameter group	Secondary production - fish
    Indicator	Distribution range change (thermal habitat)

    Reference

    Carpenter, S.R., Fisher, S.G., Grimm, N.B. & J.F. Kitchell (1992): Global change and freshwater ecosystems. Annual Review of Ecology and Systematics 23: 119-139.

    Description

    Review on effects of climate warming on freshwater ecosystems, concerning productiviy of phytoplankton, increase in zooplankton and invertebrates. Also changed fish distribution due to changed thermal limits.

  • Distribution range change (thermal habitat) / Jansen, W. & R.H. Hesslein (2004): ...

    Climate Region	humid warm
    Ecosystem type	lakes in general
    Parameter group	Secondary production - fish
    Indicator	Distribution range change (thermal habitat)

    Reference

    Jansen, W. & R.H. Hesslein (2004): Potential effects of climate warming on fish habitats in temperate zone lakes with special reference to Lake 239 of the experimental lakes area (ELA), north-western Ontario. Environmental Biology of Fishes 70: 1-22.

    Description

    Salvelinus namaycush thermal habitat progressively reduced, disappeared in littoral areas in spring and summer. Perca flavescens thermal habitat increase for temperature rise up to 4 °C, disappeared for 9 °C increase.

  • Distribution range change (thermal habitat), growth, production, survival change / Petchey, O.L., P.T. McPhearson, T.M. Casey &a ...

    Climate Region	humid warm
    Ecosystem type	lakes in general
    Parameter group	Secondary production - fish
    Indicator	Distribution range change (thermal habitat), growth, production, survival change

    Reference

    Petchey, O.L., P.T. McPhearson, T.M. Casey & P.J. Morin (1999): Environmental warming alters food-web structure and ecosystem function. Nature 402: 69-72.

    Description

    Disproportionate loss of top predators and herbivores, dominance of autotrophs and bacterivores. Zoogeographical boundaries could move 500-600 km north. Growth and production increases for fish in colder than optimum habitats. Decrease of growth and production for fish at or above thermal optimum.

  • Species richness change / Minns, C.K. & J.E. Moore (1995): ...

    Climate Region	humid warm
    Ecosystem type	lakes in general
    Parameter group	Secondary production - fish
    Indicator	Species richness change

    Reference

    Minns, C.K. & J.E. Moore (1995): Factors limiting the distributions of Ontarios freshwater fishes: the role of climate and other variables, and the potential impacts of climate change. Canadian Special Publication of Fisheries and Aquatic Sciences 121: 137-160.

    Description

    Total species richness strongly related to air temperature. For 33 out of 61 fish species presence-absence pattern related to temperature, besides geographic factors.

• Secondary production - zooplankton

  • Biomass / Shuter, B.J. & K.K. Ing (1997): ...

    Climate Region	humid warm
    Ecosystem type	lakes in general
    Parameter group	Secondary production - zooplankton
    Indicator	Biomass

    Reference

    Shuter, B.J. & K.K. Ing (1997): Factors affecting the production of zooplankton in lakes. Canadian Journal of Fisheries and Aquatic Sciences 54(2): 359-377.

    Description

    76 % of the observed variation in growing season weight-specific production rates could be accounted for by differences in temperature, length of growing season, and taxonomic group (Rotifera, Chydoroidea, Cyclopoida, Calanoida, ordered from highest rate to lowest). Within taxonomic groups, effects of population biomass density, individual body size, and food availability were not detected. 58% of the observed variation in growing season population biomass density could be accounted for by differences in individual body size, mean chlorophyll concentration, and lake mean depth. 24% of the observed variation in growing season length could be accounted for by differences in mean chlorophyll concentration and taxonomic group. Our findings suggest a simple model of the seasonal production cycle for limnetic zooplankton in which weight-specific rates of biomass production are largely set by temperature, and levels of biomass accumulation are largely set by food resource availability and individual body size. We briefly discuss the implications of this model for predicting the effects of climate change on lake productivity.

  • DNA damage by radiation - temp induced / MacFadyen, E.J., C.E. Williamson, G. Grad, M. ...

    Climate Region	humid warm
    Ecosystem type	lakes in general
    Parameter group	Secondary production - zooplankton
    Indicator	DNA damage by radiation - temp induced

    Reference

    MacFadyen, E.J., C.E. Williamson, G. Grad, M. Lowery, W.H. Jeffrey & D.L. Mitchell (2004): Molecular response to climate change: temperature dependence of UV-induced DNA damage and repair in freshwater crustacean Daphnia pulicaria. Global Change Biology 10: 408-416.

    Description

    Molecular response to climate change: temperature dependence of UV-induced DNA damage and repair in freshwater crustacean Daphnia pulicaria: DNA damage, DNA repair, photoreactivation.

• Secondary production - zooplankton

  • Population timing, growth / Van Doorslaer, W., Stoks, R., Jeppesen, E., D ...

    Climate Region	warm
    Ecosystem type	lakes in general
    Parameter group	Secondary production - zooplankton
    Indicator	Population timing, growth

    Reference

    Van Doorslaer, W., Stoks, R., Jeppesen, E., De Meester, L. (2007): Adaptive responses to simulated global warming in Simocephalus vetulus: a mesocosm study. Global Change Biology 13: 878-886.

    Description

    Although several studies suggest the occurrence of microevolutionary responses that may allow local persistence of populations under global warming, rigorous experimental proof is lacking. Here, we combined the realism and rigid, replicated experimental design of a large-scale mesocosm study where populations of the zooplankter Simocephalus vetulus were exposed for 1 year to different global warming scenarios with a life table experiment under laboratory conditions at three temperatures that eliminated confounding, nongenetic factors. Our results provide solid proof for a rapid microevolutionary response to global warming in both survival and the subcomponents of individual performance (age at reproduction and number of offspring), which may allow populations of S. vetulus to persist locally under predicted scenarios of global warming. Such microevolutionary responses may buffer changes in community structure under global warming and help explain the outcome of previous mesocosm studies finding only marginal effects of global warming at the community level.

• Secondary production - zooplankton

  • Population timing, growth, maximum / Straile, D. (2002): ...

    Climate Region	humid warm
    Ecosystem type	lakes in general
    Parameter group	Secondary production - zooplankton
    Indicator	Population timing, growth, maximum

    Reference

    Straile, D. (2002): North Atlantic Oscillation synchronizes food-web interactions in central European lakes. Proceedings of the Royal Society of London 269: 391-395.

    Description

    Higher water temperature (esp. winter/spring). Timing of early summer algal suppression (clear water timing) advanced by approx. 2 weeks within the last 30 years. Faster population growth of herbivores (i.e. Daphnia) due to warmer water.

• Susceptibility ecosystem

  • Review (anthropogenic stressors) / Søndergaard, M., Jeppesen, E. (2007): ...

    Climate Region	warm
    Ecosystem type	lakes in general
    Parameter group	Susceptibility ecosystem
    Indicator	Review (anthropogenic stressors)

    Reference

    Søndergaard, M., Jeppesen, E. (2007): Editorial overview: anthroprogenic impacts on freshwater ecosystems and approaches to restoration. Journal of Applied Ecology 44: 1089-1094.

    Description

    Freshwater ecosystems have long been affected by numerous types of human interventions that have a negative impact on their water quality and ecological state. Fortunately, in most western countries the input of sewage to freshwater systems has been reduced, but hydromorphological alterations, eutrophication-related turbidity and loss of biodiversity remain major problems in many parts of the world. Such impacts prevent the achievement of a high or good ecological state, as defined by the European Water Framework Directive (WFD) or other standards. This paper synthesizes and links the findings presented in the seven papers of this special profile, focusing on the effects of anthropogenic stressors on freshwater ecosystems and on how to maintain and restore ecological quality. The papers cover a broad range of research areas and methods, but are all centred on the relationship between dispersal barriers, the connectivity of waterways and the restoration of rivers and lakes. The construction of dams and reservoirs disturbs the natural functioning of many streams and rivers and shore-line development around lakes may reduce habitat complexity. New methods demonstrate how reservoirs may have a severe impact on the distribution and connectivity of fish populations, and new techniques illustrate the potential of using graph theory and connectivity models to illustrate the ecological implications. Hydromorphologically degraded rivers and streams can be restored by addition of wood debris, but "passive" restoration via natural wood recruitment may be preferable. The most cost-effective way to restore streams may also include information campaigns to farmers on best management practices. Removal of zooplanktivorous fish often has marked positive effects on trophic structure in lakes, but there is a tendency to return to turbid conditions after 8-10 years or less unless fish removal is repeated. Development of new methods, as well as derivation of more general conclusions from reviewing the effects of previous restoration efforts, are crucial to achieve progress in applied freshwater research. The papers contained in this Special Profile contribute on both counts, as well as illustrating the importance of well-designed research projects and monitoring programmes to record the effects of the interventions. Such efforts are vital if we are to improve our knowledge of freshwater systems and to elaborate the best and most cost-effective recommendations. They may also help in achieving a good ecological state or potential in water bodies by 2015, as demanded by the European WFD.
• 
  

  Deep

  Abiotic indicators

  • Hydrology: residence time / Bertahas, I., Dimitriou, E., Karaouzas. I., L ...

    Climate Region	humid warm
    Ecosystem type	deep
    Parameter group	Abiotic indicators
    Indicator	Hydrology: residence time

    Reference

    Bertahas, I., Dimitriou, E., Karaouzas. I., Laschou, S. & I. Zacharias (2006): Climate change and agricultural pollution effects on the trophic status of a Mediterranean lake. Acta Hydrochimica Et Hydrobiologica 34(4): 349-359.

    Description

    Receiving pollutants (intensive agricultural practices, urban sewages, stock grazing land and small industries). Due to relatively higher rainfall precipitation during the last years, an increased amount of the phosphorus entering into the lake system is flushed out, thus keeping the trophic status of the lake in oligotrophic levels. In contrast, lower rainfall rates during the first period (1990-1991) have led to the decrease in phosphorus flush out and its detainment into the lake water and sediment resulting to mesotrophic conditions. As the trophic status of the lake is mainly hydrologically dependent and thus unpredictable, effective management plans targeting the elimination of nutrient pollution loadings are necessary.

• Early warning indicators

  • Clear water timing / Straile, D. (2002): ...

    Climate Region	humid warm
    Ecosystem type	deep
    Parameter group	Early warning indicators
    Indicator	Clear water timing

    Reference

    Straile, D. (2002): North Atlantic Oscillation synchronizes food-web interactions in central European lakes. Proceedings of the Royal Society of London 269: 391-395.

    Description

    Higher water temperature (esp. winter/spring). Timing of early summer algal suppression (clear water timing) advanced by approx. 2 weeks within the last 30 years. Faster population growth of herbivores (i.e. Daphnia) due to warmer water.

  • Ice cover timing / Weyhenmeyer, G.A., M. Meili & D.M. Living ...

    Climate Region	humid warm
    Ecosystem type	deep
    Parameter group	Early warning indicators
    Indicator	Ice cover timing

    Reference

    Weyhenmeyer, G.A., M. Meili & D.M. Livingstone (2004): Non-linear response of ice-breakup. Geophysical Research Letters 31(7): 1-4.

    Description

    Long-term records (4 decades). Lake ice phenology: Potentially important for employment of lake ice phenologies as climate indicators. Relationship between air temperature and timing of lake ice breakup shows arc cosine function. Nonlinearity results in marked differences in the response of timing in ice breakup to changes in air temperature between colder and warmer regions and cold.

• Secondary production - invertebrates

  • Community change: species richness, diversity, assemblage structure. / Manca M., Portogallo M., Brown, M.E. (2007): ...

    Climate Region	warm
    Ecosystem type	deep
    Parameter group	Secondary production - invertebrates
    Indicator	Community change: species richness, diversity, assemblage structure.

    Reference

    Manca M., Portogallo M., Brown, M.E. (2007): Shifts in phenology of Bythotrephes longimanus and its modern success in Lake Maggiore as a result of changes in climate and trophy. Journal of Plankton Research 29: 515-525.

    Description

    In Lake Maggiore, the density of the invertebrate predator Bythotrephes longimanus increased following lake re-oligotrophication in the late 1980s. This "invasion" was followed by dramatic changes in the pelagic food web, consistent with those that followed the establishment of B. longimanus in North American lakes where it is not native. In this contribution, we explore the modern success of B. longimanus in Lake Maggiore by investigating its phenology and population density, and their correlations with abiotic and biotic factors during the period from 1981 to 2003. A 10-fold increase in the abundance of B. longimanus followed an earlier start and longer duration of annual population growth. Increased prey resources and decreased predation pressure were not observed during the B. longimanus density increase. Instead, a rise in lake temperature may have altered the reproductive cycle of this species. Furthermore, the depth and duration of a refuge from visually orienting fish predators increased during these 20 years, as a result of changes in the thermal stratification regime of the lake. This case study provides a timely example of how climatic changes may interact with biotic drivers (e.g. fish predation) to influence the density and phenology of an invertebrate predator.

• Secondary production - zooplankton

  • Biomass / Shuter, B.J. & K.K. Ing (1997): ...

    Climate Region	humid warm
    Ecosystem type	deep
    Parameter group	Secondary production - zooplankton
    Indicator	Biomass

    Reference

    Shuter, B.J. & K.K. Ing (1997): Factors affecting the production of zooplankton in lakes. Canadian Journal of Fisheries and Aquatic Sciences 54(2): 359-377.

    Description

    76 % of the observed variation in growing season weight-specific production rates could be accounted for by differences in temperature, length of growing season, and taxonomic group (Rotifera, Chydoroidea, Cyclopoida, Calanoida, ordered from highest rate to lowest). Within taxonomic groups, effects of population biomass density, individual body size, and food availability were not detected. 58% of the observed variation in growing season population biomass density could be accounted for by differences in individual body size, mean chlorophyll concentration, and lake mean depth. 24% of the observed variation in growing season length could be accounted for by differences in mean chlorophyll concentration and taxonomic group. Our findings suggest a simple model of the seasonal production cycle for limnetic zooplankton in which weight-specific rates of biomass production are largely set by temperature, and levels of biomass accumulation are largely set by food resource availability and individual body size. We briefly discuss the implications of this model for predicting the effects of climate change on lake productivity.

  • Population timing, growth, maximum / Straile, D. (2002): ...

    Climate Region	humid warm
    Ecosystem type	deep
    Parameter group	Secondary production - zooplankton
    Indicator	Population timing, growth, maximum

    Reference

    Straile, D. (2002): North Atlantic Oscillation synchronizes food-web interactions in central European lakes. Proceedings of the Royal Society of London 269: 391-395.

    Description

    Higher water temperature (esp. winter/spring). Timing of early summer algal suppression (clear water timing) advanced by approx. 2 weeks within the last 30 years. Faster population growth of herbivores (i.e. Daphnia) due to warmer water.