Incorporating facilitative interactions into small‐scale eelgrass restoration—challenges and opportunities

Abstract

Marine ecosystem engineers such as seagrasses and bivalves create important coastal habitats sustaining high biodiversity and ecosystem services. Restoring these habitats is difficult due to the importance of feedback mechanisms that can require largescale efforts to ensure success. Incorporating facilitative interactions could increase the feasibility and success of small-scale restoration efforts, which would limit pressure on donor sites and reduce costs and time associated with restoration. Here, we tested two methods for providing facilitation in small-scale eelgrass (Zostera marina) restoration plots across northern Europe:(1) co-restoration with blue mussels (Mytilus edulis, M. trossulus); and (2) the use of biodegradable establishment structures (BESEs). Eelgrass-mussel co-restoration showed promise in aquaria, where eelgrass growth was nearly twice as high in treatments with medium and high mussel densities than in treatments without mussels. However, this did not translate to higher shoot length or shoot densities in subsequent field experiments. Rather, hydrodynamic exposure limited both eelgrass and mussel survival, especially in the most exposed sites. The use of BESEs showed more potential in enabling small-scale restoration success: they effectively enhanced eelgrass survival and reduced mussel loss, and showed potential for enabling mussel recruitment in one site. However, eelgrass planted in BESE plots along with mussels had a lower survival rate than eelgrass planted in BESE plots without mussels. Overall, we show that though co-restoration did not work at small scales, facilitation by using artificial structures (BESEs) can increase early eelgrass survival and success of small-scale eelgrass and bivalve restoration.

Nordic Blue Carbon Ecosystems: Status and Outlook

“…Moksnes et al, 2016;Lange et al, 2022). The most successful Nordic eelgrass restorations have involved eelgrass transplants rather than seeds, and have sometimes involved anchoring of shoots, stabilization of sediments by protective structures, sandcapping, enclosures to avoid bioturbation, traps to reduce crabs, or co-restoration with blue mussels in order to facilitate eelgrass survival and growth (Moksnes et al, 2016;Gagnon et al, 2021;van der Heide et al, 2021Lange et al, 2022) (Table S7). Target areas for restoration have been identified by modelling where eelgrass habitat requirements are fulfilled (e.g.…”

Testing habitat suitability for shellfish restoration with small‐scale pilot experiments

“…Pilot restoration studies can be critical for determining the potential effectiveness of subsequent larger‐scale restoration efforts by filling in knowledge gaps, validating methods, and improving overall restoration efficiency (e.g., Brumbaugh & Coen, 2009; Cook et al, 2022). Close monitoring of pilot restoration studies may also help to isolate specific causes of decline that can then be targeted for mitigation, along with providing a method for trialing new techniques (e.g., corestoration, Gagnon et al, 2021). Shellfish restoration best practice guidelines have recommended initial smaller scale pilot experiments to assess habitat suitability as a means to ultimately improve the effectiveness of wide‐scale restoration initiatives (Fitzsimons et al, 2020).…”

Artificial habitat structures for animal conservation: design and implementation, risks and opportunities

“…Some artificial habitats are even designed to degrade over time, such as biodegradable starch mesh that can provide stable habitat on which organisms can colonize in areas where native habitat‐forming species are absent (Gagnon et al . 2021). Artificial habitat structures can also be used to replace nonrenewable habitat structures that have been permanently lost, such as rock crevices (Cowan et al .…”

“…Artificial habitat structures can act as temporary stopgaps while natural habitat structures recover; for instance, artificial tree hollows can supplement mature, hollow-bearing trees that take decades or centuries to recover from logging (Lindenmayer et al 2009; see also "Minimizing ecological risks" below). Some artificial habitats are even designed to degrade over time, such as biodegradable starch mesh that can provide stable habitat on which organisms can colonize in areas where native habitat-forming species are absent (Gagnon et al 2021). Artificial habitat structures can also be used to replace nonrenewable habitat structures that have been permanently lost, such as rock crevices (Cowan et al 2020).…”