Experimental planting of low-growing aquatic macrophytes in the Alte Donau

In 2017, seven low-growing stonewort species were planted out on a test bed on the lower section of the Alte Donau. One of the main aims of the pilot project is to reduce the amount of mowing required in future.

In spring and autumn 2017, seven low-growing stonewort species - originally the dominant aquatic plant species in the Alte Donau - were planted out over a large area on the lakebed. The test bed covers approximately 2.5 hectare and is situated on the right side-arm of the lower section of the Alte Donau.

It is hoped that the pilot measure will improve aquatic plant biodiversity in the Alte Donau while simultaneously reducing the amount of mowing required.

A number of preparatory steps were required, including mowing to a depth of 2.5 metres to clear away the high-growing plants.

The experimental planting was funded under the EU project LIFE+ Alte Donau.

Protection of the test bed

The test bed is protected by a net approximately 115 metres long which extends from the Strombucht sunbathing lawn across to Am Kaisermühlendamm on the opposite lakeshore. The net is designed to prevent fish entering the pilot area and grazing the young plants.

The stretch of water can still be used for swimming and boating as usual, a swing gate having being installed at the side to allow boats to pass through.

The net will remain in place until spring 2020 to give the new plants chance to grow and flourish.

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Function of the submerged aquatic vegetation

Underwater plants, so-called macrophytes, are essential to the excellent water quality of the Alte Donau.

They act as a biological filter, binding nutrients and thus keeping the water clear. The oxygen they produce maintains the lake's self-cleaning capacity.

However, tall underwater plants spoil people's enjoyment of boating and swimming. There has also been a huge proliferation of the underwater plants in the Alte Donau over the past few years.

The LIFE+ Alte Donau project was funded under the LIFE+ Programme of the European Union as part of the "Environment Policy and Governance" strand.