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mesocosm, e-flow

First Fully Flow-Through Stream/Ditch System

mesocosm, e-flow,

For Tier 3 Environmental Risk Assessment using Model Ecosystems (Coming 2018)

In partnership with mesocosm, e-flow

A mesocosm is an outdoor experimental system of ponds and streams whose physical dimensions and basic water chemistry are known and under controlled conditions so you can examine the natural environment. Mesocosms chararacteristically include both natural species assemblages (e.g. invertebrates, algae and macrophytes) in addition to structure populations of vertebrates such as fish. In this way mesocosm studies provide a link between field surveys and highly controlled laboratory experiments and tend to be medium-sized to large (e.g., aquatic mesocosm range: 1 to > 10,000 litres) and contain multiple trophic levels of interacting organisms. In contrast to laboratory experiments, mesocosm studies are normally conducted outdoors in order to incorporate natural variation (e.g., diel cycles). The assessment of the risk of chemicals to aquatic resources has now evolved to include an array of toxicity, fate and exposure studies conducted under both laboratory and field conditions.

Extensive mesocosm studies have been conducted to evaluate how organisms or communities might react to environmental change, through deliberate manipulation of environmental variables, such as increased temperature, carbon dioxide or pH levels. Using a mesocosm approach in regulatory risk assessment maximises ecological relevance and consequently reduces the need to use high safety assessment factors.

e-flow - The first fully flow-through stream/ditch system

The e-flow mesocosm will be the first fully flow-through mesocosm exposure facility in Europe.

Each experimental unit comprises of a 10m stream (2m width, 30cm depth) each with capture ponds. The retention time is variable allowing controlled pulse dosimetry. It will be designed, built and managed to meet the requirements of the EFSA 2013 Guidance*. This will standardise the output, assisting in ease of data interpretation. It will include sufficient replication to meet the requirement for Level 1 Reliability Index (Ri1) graded experiments. It will provide capacity to run up to three concurrent studies each utilising up to 30 experimental units (90 units available in total). The e-flow mesocosm will contain and support the diversity necessary to clearly demonstrate safety of sensitive aquatic organisms. A series of naturalised ponds, streams and wetlands will provide a diverse supply of plants and invertebrates. Alongside this fantastic facilities, we are able to provide all supporting requirements including extensive analytical capability, Quality Assurance (GLP), and trained ecologists.

*Guidance on Tiered Risk Assessment for Plant Protection Products for Aquatic Organisms in Edge- of- Field Surface Waters (EFSA, 2013)


"I want to deliver an agenda to increase farming yield and productivity whilst leaving our environment in a better condition than we inherited" - Andrea Leadsom, SoS DEFRA, OFC 2017

A mesocosm will support product developments for increased yield whilst ensuring environmental protection for water habitats.

The e-flow mesocosm facility will support active/product development for increased yield whilst ensuring environmental protection for edge-of-field waterbody habitats

Want to know more about e-flow

The choice of site supports the quality of the science we do here at Sand Hutton. Here we have considered several factors:

  • Unshaded experimental area - shadow analysis to demonstrate that the experimental area is not partially shaded, as this could otherwise affect the experimental outcome
  • Buffered from local activity - while ensuring the site is not shaded, it remains enclosed by a buffer of established vegetation to protect if from local road and farm activity
  • Geographical considerations - Sand Hutton in positioned on the northern extent of the European growing region - allowing 'worst case' assessments. Where chemical application is shown to be safe for Yorkshire, it can be expected to be safe for locations further south with longer growing seasons.
  • Size and nature of experimental area - the large experimental units (base unit volume = 3000L) have been designed to be as naturalised as possible in order that the biota is not pre-stressed by the habitat provided.

Quality of Water

It is also vital that the water used in aquatic risk assessments is a good simulation of a high quality edge of field waterbodies. Our water supply is delivered via a borehole from a Grade A Sandstone Aquifer 40m under the site. It is then aged by a 5 day aging process through 5 large surface area lagoons to 'create' surface water. We regularly undertake analysis of the water quality.

It's important that there is sufficient scope for adequate experimental replication: the e-flow will provide a mesocosm system than can be used flexibly over up to 90 experimental units, in order that multiple exposures can be made each with three replicates, six concentrations and double controls. An experimental unit on this mesocosm comprises a stream that can be varied in depth between 15 and 35 cm, and in length, anything up to 10m long. Where necessary experimental units can even be combined into 30 units each 30m long. The unique property of the e-flow is that it can deploy all the experimental units as fully flow through streams, at any flow rate giving retention times from 100's days up to 0.1 days. This allows chemical doses to be managed in order to mimic the dose pulses predicted by models. Of course, pumping can be stopped so that lotic conditions apply. Each experimental unit is also terminated by a capture chamber that can be used to deploy additional measures where this is desired, e.g. drift nets, or can be used as deeper water ponds, or to exposure additional compartments - deep sediments or even fish on particular request.

In addition, each unit will have automatic monitoring of pH, dissolved oxygen and temperature, and a site weather station will be provided recording sunlight hours, light levels, rainfall, air temperature.

If you have any questions please do not hesitate to contact or +44 (0)300 100 0323