Groundwater flooding: Groundwater community recovery following an extreme recharge event.

This winter (2013-14) has been the wettest in the UK since records began resulting in extremely high groundwater levels and very extensive groundwater flooding, particularly in chalk aquifers. The exceptionally high intensity of flooding and water movement through the aquifers is expected to result in changed nutrient concentrations, including carbon. We think that these changes will have major effects on the groundwater ecosystem which, in addition to the chemical and physical environment, comprises microbial biofilms, microfauna (e.g. Protozoa, rotifers), and macroscopic invertebrates dominated by crustaceans such as copepods and Niphargus (blind shrimp-like animals). Most groundwater organisms are unique to this habitat and, in the UK, have been present for many millions of years. They mediate processes such as nitrogen recycling and thus they impact the quality of a vital source for drinking water.

We think that during flooding, nutrient supplies will initially decrease due to dilution and that flow rates will increase, potentially stripping microbial biofilms and associated microfauna from the sediments and dislodging larger organisms into the water flow. This will lead to an initial reduction in biomass at each trophic level although it will not alter the overall shape of the biomass pyramid. We also expect ecosystem respiration and species and/or functional diversity to be low during flooding. When the flood ends we think that microbial biofilms, protozoa and small metazoa will recover quickly because they reproduce rapidly but that larger animals will recover more slowly if they cannot find shelter from the flood. This may result in a change in shape of the biomass pyramids. We will test these ideas by tracking the recovery of the groundwater ecosystem through space and time. We will do this by collecting samples to measure the food supply (dissolved organic carbon and other nutrients), count and identify the inhabitants of the groundwater ecosystem and also determine how ecosystem function changes by measuring respiration rates and microbial activity. We will collect samples in two separate flooded chalk aquifers at fortnightly intervals over a seven month period so that we can monitor changes in the community; we expect these to be rapid. We will use specialised equipment to measure microbial respiration and count the smallest organisms (bacteria). This extreme event permits a uniquely important case study because it will provide a baseline against which future extreme events (e.g. flooding and drought) in groundwaters can be measured and will enable us to compare the responses of groundwater ecosystems to stressors with those of other aquatic ecosystems.

We hope to use the data collected in this project to apply for larger grants, possible topics for these grant applications include combining data generated in this Urgency grant with laboratory experiments that will enable us to calculate the extent to which different Groundwater assemblages (e.g. with or without macrofauna) are able to metabolise dissolved organic carbon/ nutrient loadings and thus, provide effective water quality ecosystem services of substantial ecological and economic impact to the UK.

Those who will benefit from the research

Scientists including Ecologists and Biogeochemists:
Our findings will improve the current very limited understanding of the responses of groundwater ecosystems to flooding and provide a benchmark for future extreme groundwater flooding events, providing an essential resource to the scientific community. They will enable a comparison with ecosystem responses to stressors in surface systems and be used to examine groundwater ecosystems and their response to flooding in the context of general ecological theories e.g. the Metabolic Theory of Ecology. Our data will also be of benefit to interdisciplinary scientists because it will shed light on the interactions between water chemistry, microbial biofilms and macrofauna and how these are affected by flooding.

Government Agencies, Environmental Consultancies and Water Industries:
The results of this project will provide regulators and decision makers in government agencies, environmental consultancies and water industries with a picture of how groundwater ecosystems will respond to one aspect of a changing climate. Our results will feed into mitigation strategies for future extreme events and provide policy makers and stakeholders with data pertaining to the responses of GW ecosystems to flooding and the impact this may have on GW quality.

The General public:
There is a clear concern as to the impact of groundwater flooding on human property and water quality and the general public will need to be appropriately informed of the results of our research.

How they will benefit from our research
Scientific community: The knowledge gained from our study will drive future research directions, and inform research into understanding the ecological response of ecosystems to future climate extremes.
Government Agencies, Environmental Consultancies and Water Industries and general public: Close collaboration with our EA Project Partner and with other stakeholders such as Natural England and river trusts ensures that the new understanding of responses of groundwater ecosystems to flooding will inform decision making in the management of groundwater ecosystems. Our results will provide policy makers and stake holders with an estimate of the impact of flooding on GW ecosystems, these results are transferable and can provide essential information for predictions of future impacts of global change and anticipated increased frequency of flooding extremes.

Measures to ensure benefits from this research
The dissemination of the results of this project will benefit strongly from our Environment Agency project partner who will ensure that our results are highlighted within their organisation. The involvement of the investigators in national and international research and stakeholder networks (e.g. BES, SEFS, UNESCO, EGU , BHS) will also benefit dissemination. We will also organise a one day UK workshop targeted at academics, research institutes, water companies, environmental consultants and managers, decision and policy-makers, government agencies and laypersons.
We will develop a project website (hosted at UR) with content for scientists, decision makers and laypersons. A project summary will be published here, outlining (in layperson's terms) the significance and key findings of our work. Following the urgency phase of the project, results will be published in high-impact, peer-reviewed journals as well as in popular periodicals and newsletters (e.g. NERC Planet Earth, Freshwater Biological Association newsletter). We will present our results at major international and UK conferences plus invited research seminars at universities and other research institutes.
We will also engage with schoolchildren (keystage 2; water cycle). JR is a STEM ambassador and will disseminate our findings in local schools. The project findings will form part of the science week hosted by UR where we showcase our research to the local community.