PRECISE

Predicting eutrophication and climate change impacts on shallow lake ecology and biodiversity: disentangling the effects of temperature and nutrients

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 Obiettivo del progetto (Objective)

'Increased nutrient concentrations in freshwater ecosystems have had profound impacts on their biodiversity, perhaps none more so than in shallow lakes. It may be that impacted systems such as these are particularly vulnerable to climate change. Increasing temperature and eutrophication are not only linked, but their impacts are similar and thus it has proven very difficult to disentangle their effects. It may be that analysis of rate of change may elucidate the effects of climate change and nutrient enrichment on shallow lake biodiversity, species turnover and ecosystem function. PRECISE seeks to determine the extent and rate of change in shallow lake biodiversity and ecosystem function resulting from eutrophication and climate change. To do this a longer-term perspective is vital, PRECISE consists of three approaches which encompass distinct combinations of climate and nutrient effects at a range of temporal scales. These are: large-scale mesocosm experiment; contemporary time series analysis; and palaeolimnogical analysis. The overarching aim is the determination of the effect of temperature and nutrient concentration on the extent and rate of change in the balance of benthic to pelagic production and biodiversity. This will be achieved by complementing on-going research generating biodiversity data with both direct measurement of algal crop (benthic and pelagic) and the determination of pathways of production by the analysis of stable isotopes. This will be done both in the mesocosm experiment (nutrient and temperature separate) and through time series analysis of observational data (temperature and nutrient together). A meta-analysis of an existing data from sediment cores will compare contemporary change (nutrients and climate together) with change associated with a rapid increase in temperature after the 8.2K cooling (climate alone). These integrated analyses will elucidate on unique climate and nutrient impacts on shallow lake biodiversity and function.'

Introduzione (Teaser)

Shallow lakes have been greatly affected by increased concentrations of nitrogen and phosphorus from intensive agriculture and increased human populations. These key nutrients for plant growth enter the aquatic environment, changing clear water to turbid through a phenomenon called eutrophication.

Descrizione progetto (Article)

Eutrophication can lead to the replacement of aquatic plants by large blooms of phytoplankton and the loss of species at every level of the food chain. In combination with the impacts of eutrophication, freshwater ecosystems are also threatened by climate change both now and in the future.

The PRECISE project investigated the extent and rate of change in shallow lake biodiversity and ecosystem function resulting from eutrophication and climate change. Researchers took a long-term perspective based on a three-way approach that considered distinct combinations of climate and nutrient effect over time. The three approaches involved large-scale experiments under controlled conditions (mesocosm), contemporary time series analysis and analysis of ancient lake sediments.

Project partners complemented available biodiversity data with measurement of algae production from the lake bed and the water column. They also determined production pathways using stable isotope analysis. Analysis of existing data from lake sediment was used to compare contemporary changes in temperature and nutrients with past changes.

Results demonstrated that sedimentary remains can be used to track long-term change in the ecology of shallow lakes by using isotropic analysis. In addition, a species of water flea, Daphnia ephippia, and fish scales can be used to track changes in the food web structure over time.

The work conducted by PRECISE has increased scientific understanding of the effects of eutrophication and climate change on shallow lakes. This was achieved by explaining how these two factors relate to changes in biodiversity and ecosystem function.