PROJECT DESCRIPTION
BACKGROUND
Filamentous green algae grow fast during the summer months and form dense mats covering large parts of shallow coastal bays in the Archipelagos in Bohuslän, on Sweden’s West Coast and in Åland in the Baltic. These algae mats are decreasing the biological diversity and destroying the nurseries of several species of fish. The value of the bays in terms of outdoor life and tourism is also decreasing. The rapid growth of algae is one of the results of the increasing amounts of nutrients in coastal waters and in the bottom sediments. The bays have become eutrophicated.
OBJECTIVES
The project aimed to demonstrate a way to reduce the negative effects of eutrophication on biodiversity, fisheries and recreation by removing short-lived macro algae in ecologically representative shallow water areas. For this purpose the project would develop a method and equipment to collect algae and to recycle it for environmentally sound purposes. Algae removal would be supported by efforts to reduce the discharge of nutrients into the coastal waters. It is expected that the project would result in the restoration of shallow coastal waters as nurseries and feeding grounds for juvenile fish. Instruments appropriate for local and regional authorities to improve coastal management would also be developed. The pilot areas and sites were in the Bohuslän archipelago on the Swedish West Coast and in the western part of the Åland archipelago between Finland and Sweden.
RESULTS
An innovative technique for harvesting algae was developed and tested. The result was a functional algae harvester prototype that can take up floating algae in bays where the water is more than 30 cm deep without disturbing the bottom or plant and animal life to any considerable extent. It has three main components: a hydraulic engine that drives the other two components; a platform and three conveyor belts that pull up, dewater and buffer-store the algae. The algae are subsequently loaded onto a barge for transportation to dry land for recycling in suitable processes. The meaningful use of algae, for example as fertilizers, as raw material for the manufacturing of paper and for production of biogas, were investigated and tested. However the end results were rather meagre. The projects efforts to identify alternative uses of harvested algae did not lead to the identification of concrete solutions, beyond the fact that the use of algae as fertiliser on certain crops did not seem to have any significant negative effects. The sustainable use of the harvested algae has to be further studied. Two new models were developed that increase our understanding of the ecological role of shallow bays: One model describes how plaice recruitment is affected by algae mats and show that the amount of juvenile plaice decreases significantly when the coverage of algae mats increases. The other model, shows how the supply of nutrients and harvesting of algae limits the growth of algae. With regard to the economic feasibility of harvesting algae, the results of the project were rather superficial and further studies are required. On the one hand it is indicated that harvesting is cost-efficient if it significantly improves the recruitment of plaice. Calculations made show that the algal covering may reduce the potential catch of adult plaice to an annual sales loss of about SEK 60 million. However, the difficulty of how to dispose the harvested algae in a sustainable way, avoiding excessive costs, has not been solved. Increased water flow through road embankments and inlets in shallow waters were calculated by the use of a water flow model. The calculations have already led to a number of measures being taken to increase water flow in the Bohuslän Archipelago and thus decreasing the algal cover. The project worked successfully in achieving its goals, but considerable delays occurred in the core area of technology development, which affected the monitoring programmes. The prototype algae harvester was operational for the harvesting season of 2000, although the plan had foreseen this to happen already in 1998. This meant that the monitoring up until then was based on simulations or inference or experiences from other actions such as manual harvesting. The beneficiary had problems in estimating and solving the technical difficulties the development of the equipment would involve and consequently the timescale needed to find solutions. It may be noted that the beneficiary, being an administrative body, might not have been the most suitable organisation for the development of equipment needing some hands-on work. However it could also be stated that it would be difficult to imagine any other organisation or e.g. commercial entity daring to tackle this issue, with very unforeseeable results. The total cost for the development and construction of the harvester was about EUR 260 000. The estimated price for building one more is EUR 105 000. It is unlikely however that the harvester would be copied for a more extensive use in that the beneficiary, as owner of the technology and as an administrative body, is not familiar with the commercial type dissemination and marketing required. The project lacked resources in terms of time and funds to test alternative/existing machinery. Design and testing was confined to the projects own prototype. The project has however gathered plenty of knowledge concerning the biology of these shallow waters and how they are affected by the rapid growth and removal of floating algae. This knowledge is crucial especially for the fishing industry since shallow waters are often a ‘nursery” for fish. This knowledge is likely to be of great interest also for other parts of the EU and for EU policy development, particularly with regard to the Integrated Coastal Zone Management process and the EC Water framework directive.
