Cladocera (Crustacea: Branchiopoda; water fleas) are ubiquitous in inland aquatic habitats and play a key role in freshwater ecosystems due to their central position in the food web, positioned between top-down feeders (fish and invertebrate predators) and bottom- up organisms (phytoplankton).
Cladocera are therefore highly significant for nutrient cycling in freshwater systems and, by extracting and enumerating their remains in the sediment record, can be used to infer past lake nutrient conditions or lake habitat changes. The taxonomic composition of the subfossil cladoceran remains have been used to track past changes in the environment, including eutrophication, acidification, lake levels, submerged macrophyte abundance, fish density and climate.
At Henderson Ecology we can analyse the Cladocera remains preserved in lake sediments to establish past reference conditions for a lake and inform ecological classifications as required by the Water Framework Directive. A selection of Gina Henderson's Cladocera studies are listed below (see Publications for more details).
2011-2014, BIOFRESH project (European Union).
2013, Reference conditions for phosphorus runoff from forested areas with arable soil properties (Norwegian Research Council, led by Bioforsk, see details below).
Case Study- Lake Vastadtjern, Norway
The cladocera remains were analysed from a sediment core from Lake Vastadtjern, Norway as part of the BIOFRESH project (European Union) in order to explore if the lake had undergone recent eutrophication. The graph below is a summary stratigraphy for selected sub-fossil cladoceran remains (>2% relative abundance) from the lake. Marked changes occur in the Cladocera remains, from a diverse assemblage of pelagic and plant-associated taxa in the middle of the core to an assemblage comprising smaller taxa and several species indicative of higher productivity (Eurycerus spp, Chydorus sphaericus and Graptoleberis testudinaria) in the upper section. In addition the reduction of Alonella nana, Alonella excisa and Acroperus harpae in the upper section of the core could be related to an increase in nutrients as these species have all been shown to prefer less productive lakes.
The results of the cladocera work were used in conjunction with the ephippia remains, diatom assemblages and macrofossil record to asses how the lake had changed in the past and evaluate the extent of the eutrophication. For more details of this project please see Publications or contact us to discuss how cladocera analysis could inform ecological restoration targets.