The restoration of Ormesby Broad

Aim

To restore clear water, wildlife, and good fishing conditions to Ormesby Broad

Background

Routine water quality monitoring by the Environment Agency indicated that some deterioration had occurred in the water quality; an increase in phosphorus was recorded which could greatly increase the growth of algae.  Active management was required to encourage a reversal of this trend using a technique called ‘biomanipulation’.

Biomanipulation

Water fleas feed on algae and need water plants to protect them from the fish that prey on them for food.  When a lake becomes enriched through nutrients, water plants gradually disappear leaving no refuge for water fleas.  If there are no water fleas then the algae remains and the water stays cloudy.

By temporarily removing, such as Bream and Roach, water fleas can feed on algae in safety, naturally clearing the water of algae.  This creates the right conditions for water plants to re-establish themselves; light and oxygen reaches the water plants rather than being blocked out by the algae.

Project

The biomanipulation project was undertaken as a demonstration study under EC LIFE Project (LIFE 92-3/UK/301) in partnership with the Broads Authority, Environment Agency and Essex & Suffolk Water; this partnership has since funded the necessary work.

The biomanipulation process will remain a temporary measure until the Broad has reached a natural balance where it can maintain its own clear water conditions.

Local Community

The Trinity Broads Consultation Group was formed in 1997 to ensure the local community remained fully briefed on the activities and developments of the project.  The support of the Broad users and the local community is an important component of the biomanipulation project.

Results

The project has produced encouraging results so far but the period of monitoring has only encompassed a relatively short timescale (1995 – present) and ecological systems often take a number of years to adjust before the full impacts can be identified

The fish community in Ormesby Broad is responding in an encouraging way with the recruitment of species such as Tench (Tinca tinca), Rudd (Scardinus erythrophthalmus), Perch (Perca fluviatillis) and Pike (Esox lucius).  This has led to the establishment of a diverse community containing a large number of species.

The biomanipulation on this Broad is now entering a critical stage.  If a stable aquatic plant dominated broad can be achieved, intervention through manipulation of fish stocks will no longer be necessary.