Lakes in warm ecoregions - indicators for climate change
The raising temperatures and changes in precipitation patterns due to climate change will result in complex cause–effect chains, linked by many interacting environmental parameters. The degree of ecosystem response will depend on the ecoregion (cold, temperate or warm) and ecosystem type (lakes, rivers or wetlands), and on species-specific adaptations of different organisms.
The purpose of this section is to suggest indicators for the effects of climate change on lake, river and wetland ecosystems that reflect the direction of their pathways, relative importance, and magnitude of change.The term ‘indicator’ is used here simply to describe a detectable signal of a complex process that can be used as an early warning of ecosystem change. Indicators may be chemical, hydrological, morphological, biological or functional parameters, which reflect key processes influenced by climate change and are relatively simple to monitor.
The purpose of this section is to suggest indicators for the effects of climate change on lake, river and wetland ecosystems that reflect the direction of their pathways, relative importance, and magnitude of change. It addresses the three ecosystem types and the three climatic regions always with four categories of indicators: (a) abiotic variables; (b) primary producers; (c) macroinvertebrates; and (d) fish.
Physico-chemical
Dissolved salts concentration
Ecoregion:
Cold and Warm
Category:
Physico-chemical
BQE:
Salinity
Indicators:
Dissolved salts concentration
Why measure:
Warmer winters cause extreme rainstorms and heavy sea-salt deposition together with increased evaporation in summer, might affect water chemistry and biotic structure
How to measure:
Direct measurments of salinity levels
Oxygen concentration at the bottom in summer
Ecoregion:
Warm
Category:
Physico-chemical
BQE:
Dissolved oxygen
Indicators:
Oxygen concentration at the bottom in summer
Why measure:
High temperatures will stimulate phytoplankton growth, which will lead to oxygen depletion of habitats. Dissolved oxygen will also decrease as a result of lower solubility in warmer waters and increased microbial activity
How to measure:
simple to monitor, easy to incorporate into routine monitoring
Hydrological parameters
Lake surface
Ecoregion:
Warm
Category:
Hydrological parameters
BQE:
Water level
Indicators:
Lake surface
Why measure:
Increased temperature and decreased precipitation in conjunction with intensive water use will decrease water volumes. This will lead to water level imbalances and, in many cases, to the complete loss of water bodies
How to measure:
simple to monitor, e.g. by remote sensing
Biological
Alien species
Ecoregion:
Temperate and Warm
Category:
Biological
BQE:
Secondary production
Indicators:
Alien species
Why measure:
Higher temperatures often favour alien fish, macrophytes or macroinvertebrate species. These may have a negative impact on local biota, including increased predation and competition for food and habitat.
How to measure:
Share of alien species in the community (macrophyte, macroinvertebrates, fish)
Macrophyte properties
Ecoregion:
Temperate and Warm
Category:
Biological
BQE:
Primary production
Indicators:
Macrophyte properties
Why measure:
Inter-annual variation in water temperature results in deeper macrophyte colonization, greater wet weight biomass, and an increase in whole lake biomass.
How to measure:
Macrophytes can be sampled routinely using WFD methodologies or using remote sensing techniques.
References:
Bucak T., Saraoglu E., Levi E.E., Tavsanoglu U.N.Y., Idil Çakiroglu A., Jeppesen E. & Beklioglu M., 2012. The role of water level for macrophytes growth and trophic interactions in Mediterranean shallow lakes: a mesocosms experiment with and without fish. Freshwater Biology 57(8): 1631-1642.?(2)
