Ecological-social-economic assessment of zebra-mussel cultivation scenarios for the Oder (Szczecin) Lagoon

Abstract

The Systems Approach Framework with an integrated Ecological-Social-Economic assessment was applied to address the issue of zebra mussel (Dreissena polymorpha) farming in the large Oder (Szczecin) Lagoon, southern Baltic Sea. Heavy eutrophication hampers the use of the lagoon and zebra mussel farming is considered as new use and potential measure to improve water quality. Three alternative scenarios were developed in interaction with local stakeholders: 1) the production of mussels as fresh feed and meal on a commercial basis seemed not profitable, because of a limited market for fresh mussels (zoos, aquaculture) and low prices for organic feed. 2) Mussel cultivation to improve transparency and attractiveness of bathing waters near beaches had only a limited potential (0.2 m improvement of Secchi depth). A higher mussel biomass would increase the risk of temporary hypoxia. 3) Mussels farms for improving the environmental status (according to EU Water Framework Directive) by supporting macrophyte restoration were considered as the most promising scenario. Our model simulations suggested that as soon as a compensation for nutrient removal is considered, all mussel farm scenarios could cover the costs. Experiments and literature confirm that the conditions for an environmental friendly farming approach in the lagoon are suitable. Steps towards and problems associated with an implementation, e.g. invasion of Dreissena bugensis (quagga mussel), are discussed. Each step of the Ecological-Social-Economic assessment and major lessons learnt are documented in detail. Altogether, the approach turned out to be very suitable for this issue.

Spatial Effects of Different Zebra Mussel Farming Strategies in an Eutrophic Baltic Lagoon

“…They allow an efficient reduction of phytoplankton (Qualls et al, 2007) and the active withdrawal of nutrients from strongly eutrophied coastal waters, which will fail to achieve the Good Ecological Status (GES) as claimed by overarching European legislations like the Water Framework Directive (WFD, 2000). Harvesting the farmed mussels is thereby necessary to ensure the active nutrient removal and allows to produce a highly valuable protein-rich product, utilizable i. a. in zoos (Schernewski et al, 2018), as forage (McLaughlan et al, 2014) or for the biogas production (Wollak et al, 2018). Even further uses of the shells are under development (Morris et al, 2018).…”

“…For the aquarium, sampling procedure was analog and air bubbles provided continuous mixing of the system. Between 2012 and 2014, in a semi-enclosed bay (Lake Usedom; Figure 2A) in the north-western part of Small Lagoon, a pilot farm was established, utilizing a newly developed net ( Figure S1, on which the mussels stay throughout their whole life cycle (Schulze-Böttcher, 2014;Schernewski et al, 2018). The nets were deployed on six longlines which were locked with gravity anchors.…”

“…To estimate it, coupled 3D-simulation models are a suitable tool (Marinov et al, 2007), which include the hydrographical conditions near and far of a mussel farm, as well as the lower trophic food web, as nutrients and phytoplankton are impacted. Such spatially explicit models are a central key for the public acceptance and the stakeholder involvement in the planning process (Schumacher et al, 2018), while box models (Grant et al, 2007;Schernewski et al, 2012) are not suited to predict the spatial effects, which are often requested by stakeholders (Schernewski et al, 2018). If proven to be operated in a sustainable way, mussel farms allow to combine a spatial and temporal restricted effect with the necessary ecological improvements and the production of highly valuable protein-rich food for which there is a growing demand and market (Weber and Windisch, 2017), following the EU Blue Growth Strategy (European Commission, 2014).…”

“…This resulted in an improved Secchi Depth (e.g., reported for Lake Huron by Fahnenstiel et al, 1995) and often led to the resettlement of submerged macrophytes (Skubinna et al, 1995;MacIsaac, 1996). Up to now, zebra mussels are only cultivated in small scale pilot farms (Lindahl, 2013) and are 2 to 3 cm at harvest to ensure the further processing (Schernewski et al, 2018). However, their potential is attracting more attention, e.g., in Curonian Lagoon (Bagdanaviciute et al, 2018).…”

A systems approach framework for coastal management and its application in practice

“…This Special Issue also tests the new SAF process through several case studies comprised of the BONUS BaltCoast project: in Schernewski et al (2017) to explore the possibility, together with stakeholders, to open a beach in the Curonian Lagoon (Lithuania); in Schernewski et al (2018) the SAF is applied to evaluate the effects of three potential scenarios of Zebra mussel (Dreissena polymorpha) cultivation in the Oder Lagoon (Germany) in an ecological-social-economic context; in Tõnisson et al (2018), to support coastal zone management in Pärnu (Estonia) by (re)evaluating coastal protection and flood prevention measures; and in Dinesen et al (2019) to support sustainable fisheries management by understanding the decline of Atlantic cod (Gadus morhua) fishery in Danish waters. Highlighted by Gillgren et al (2018), in the SAF application, an effective public participation strategy is of great importance to support the process of policy implementation and decision-making.…”