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BioHavens – What Are They Good For?

Darren Tansley, Essex Wildlife Trust’s Water for Wildlife Officer, worked with landowners in Sible Hedingham to improve a lake that was previously a carp fishing lake.

The lake is no longer fished and the carp have been removed and is now left to become a wildlife area. The quality of the water within the lake is poor due to increased nutrients from the fish and lacks habitats within the lake itself. Darren saw this as an opportunity to try out floating islands called BioHavens. These islands not only create habitats within the lake but it is hoped that they will improve water quality through their clever design. Below is a description of how they work:

BioHaven Floating Wetland Technology is designed around the same principles as a wetland: utilising the natural processes of plants and microbes to improve water quality. BioHavens are man-made floating islands, the proprietary design enables plants and microbes to live in ultra-high concentrations, exponentially higher than those found in naturally occurring or constructed wetlands.

Beneath the BioHaven, a hanging network of roots, rhizomes and attached biofilm is formed. This provides a huge active surface area for biochemical processes, as well as physical processes such as filtering and entrapment. The general design objective is to maximise the contact between the root/biofilm network and the polluted water.

BioHaven® has been specifically designed to mimic a natural wetland; these habitats are extremely valuable environments and provide a broad range of ecosystem services.

BioHaven doesn’t rely on any form of external buoyancy; its deep matrix allows emergent vegetation to naturalise, establishing extensive roots that grow into the water and provides a year round enhancement.

BioHaven can accommodate gravel finishes, otter holts, artificial sand martin banks or beautiful combinations of emergent and terrestrial vegetation, tailored to specifically target habitat creation for key species.

The BioHavens are uniquely designed for each location, with a combination of plants that suit the needs of the area they are being installed into. The company that created and installed the BioHavens is Frog Environmental and if you would like to know more please follow this link.

The photos show some of the Conservation team from Essex Wildlife Trust and the Frog Environmental Team, including Richard Haines a founding partner of the company, assembling and installing the islands in the lake in Sible Hedingham.

It will be interesting to see how the lake will improve with the introduction of the BioHavens and the lake will continue to be monitored to see what impact they have. We will keep you informed of what the results are and any similar projects that we are involved in.

Note: the photos on the right show the following: 1st photo; the BioHaven/island before anything is added, 2nd photo; a layer of compost is spread across the top and fills in all the holes which will help to absorb water from the lake to keep the plants moist, 3rd photo; a mat of aquatic plants are placed on top of the soil (the plants are grown on coir matting), 4th photo; the matting is secured in place, 5th photo; shows the weights that are attached to the bottom of the island and these will sit on the bottom of the lake preventing the island moving too far from its desired position, final photo; the island being secured in place.

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The topics below represent the pressures that many waterbodies in the Combined Essex catchment face. They have been divided into six main categories, but it is quite often that these categories can overlap as pressures relate to each other.

Diffuse pollution occurs as water moves across the land or through the ground and picks pollutants. These pollutants can come from a variety of places, including urban and field run off. The pollutants that enter the river can range from sediment to toxins to excess nutrients, meaning that diffuse pollution can cause a whole range of different issues. The variety in these pressure groups means that it is something that can be quite difficult to tackle. It requires groups of people, business and stakeholders to work together in order to solve this problem.

Fish should be able to travel up and down a river freely, allowing them to move and breed in the most suitable habitats for them. It is important that fish populations do not become isolated, as this makes them more susceptible to disease and puts pressure on their survival. Unfortunately, there are often many barriers along rivers that prevent fish from being able to migrate up and down stream. Where barriers have been identified, they will be seen as a ‘pressure’ on a waterbody. Thankfully, there are many solutions now that can be put in place to aid fish passage, even over large barriers.

The flow in a river can vary greatly throughout the year as rainfall and run off can have an effect. This is a natural process. It is when flow is impacted by non-natural processes that it can cause problems. Sometimes, water can be intercepted or removed from a system; this will reduce the flow, therefore changing the habitat conditions. Some species are happy in high energy rivers. This means that when flow is reduced, these species will no longer survive. The opposite of this can occur when excess water is entering a river, for example through increased runoff. Low energy systems then become high energy and displace the species that live there.

A species that is not meant to be found in a particular area is known as an invasive species. Invasive species can be from a different habitat or a different country altogether. Most of the invasive species that we find on our rivers have come from other countries – plants that people have imported for their gardens or animals that have been released for food or by animal rights activists. Control of invasive species requires a lot of time and effort. We are fortunate that we do have a range of methods to manage most of the invasive species that cause havoc on our rivers, but there are still some which we are still struggling to control.

Many of our rivers have been heavily modified over the years as rivers have been used for a wide range of purposes. Physical modification is one of the biggest factors that causes our rivers to be unhealthy. The issues that it can cause range from reducing habitat, preventing migration of mobile species, and even have an effect on the water quality. Where structures and modifications are no longer in use or necessary, they should be removed to allow the river to regain its natural state. Unfortunately, this action is not always taken which means that many of our rivers are over straightened and contain redundant structures. It is possible to return a lot of our rivers to their natural state, through one off projects, but in other cases it is not possible as the river has been changed to protect assets or manage flooding. It is recognised that some modifications cannot be removed without having severe negative impacts both socially and economically.

This is pollution that comes from a single identifiable source. The pollution entering the river could include a whole range of pollutants. Some point source pollution is known about and licences, for example sewage treatment works. Other sources are not licensed, and therefore work needs to be done with landowners to fix the problems that are allowing the pollution to enter the river. Point source pollution is more easily controlled than diffuse pollution as it often only takes one management approach to solve the issue.