Kristensen E., Flindt M. - University of Southern Denmark

The project

The dramatic decline in eelgrass coverage in coastal areas during recent decades has serious implications for associated ecosystem services, such as carbon and nitrogen sequestration, coastal protection and biodiversity. The expected recovery of eelgrass in coastal areas following substantial reductions in nutrient loading has not occurred. A major reason is negative feedback mechanisms related to physical and biological disturbances that hinder the transition from seeds to established seedlings.

The objectives of the NOVAGRASS project are to 1) develop new technical tools for eelgrass seed harvest and transplanting, 2) apply and evaluate these tools at a large scale in the field, 3) provide guidelines for eelgrass restoration, including challenges related to climate change through modeling approaches, and 4) provide a socio-economic analysis and assessment of the ecosystem services gained by restoration.

The approach is to develop eelgrass seed harvest and storage procedures, and to combine these with transplanting techniques designed to alleviate effects of physical and biological disturbances. The work is based on the experience obtained from previous projects and the knowledge of widely recognized eelgrass restoration experts. Industrial partners are integrated in the NOVAGRASS research providing logistics, equipment and techniques for large-scale restoration.  They enable NOVAGRASS to develop novel technologies for the expanding market of aquatic ecosystem restoration.

Some results

- The effect of seed processing on germination success. Results show that mechanically processed seeds survive and germinate less successfully than hand separated seeds. The impact of storage for periods of several months on dormancy and germination success of manually harvested seeds will be available soon.​​​

- Eelgrass restoration. Methods based the broadcast of eelgrass seeds have shown limited success. As an alternative, shoot transplantation has been attempted at shallow and deep locations using an array of newly developed methods. The results indicate basin-scale spatial heterogeneity in transplantation success.  In some locations eelgrass will not remain unless it is protected, using a variety of methods, while in other locations transplanted eelgrasses has been found to grown well irrespective of physical protection.​

- A particle model of eelgrass seeds. Combined hydraulic and ecological 3D models have been used to predict the likely success of eelgrass recovery following restoration actions. The model includes a variety of key state variables, and can identify thresholds where the system feedback mechanisms respond positively to eelgrass recovery. A series of multi-year simulations is being carried out on selected estuaries (lagoons) with different eelgrass die-back history, restoration schemes and climate scenarios to identify the potential for eelgrass recovery. GIS maps are being generated of present and simulated future eelgrass coverage depending on the applied restoration actions and climate conditions. The maps will be used for subsequent ecological and socio-economic analyses.

Figure 1. Seeds on mature shoot. Photo credits to Troels Lange. ​

- Technological developments. The collaboration of scientific and industrial partners with complementary expertise in NOVAGRASS offers the potential for successful development of innovative technologies for mass harvesting, storing and germination of seeds as well as for planting seedlings. The industrial partners’ commercial interest provides the incentive for the development of cost-effective techniques that are applicable widely in water management. The systems are designed to have limited impact on the eelgrass meadows that are being harvested. The design and construction drawing for a large scale eelgrass seed harvester have been completed. In addition, a lighter second generation sowing machine has been developed while tests of a high density sowing machine have been performed. Initial tests of the seed harvester have shown successful regrowth of eelgrass after seed harvesting.

The future

The NOVAGRASS project ends in 2018. The work will instead be continued for the next 3 years in the project “large-scale transplantation of eelgrass” (TRANSPLANT) funded by the Danish Nature Agency. The main purpose of TRANSPLANT is to demonstrate the potential for eelgrass restoration by applying large-scale transplantations of shoots in a number of Danish fjords. The transplantations will be conducted in hydrographically and ecologically diverse areas where eelgrass distribution is limited. The specific test areas selected will cover the most common types of coastal areas found in Denmark. The benefits derived from ecosystem services following the transplantation of eelgrass will be assessed including N, P and C sequestration.

For further information contact Erik Kristensen (ebk@biology.sdu.dk) and Mogens Flindt (mrf@biology.sdu.dk), Department of Biology, University of Southern Denmark.

Figure 2. Automated seed harvester. Photo credits to Flemming Gertz. ​