As seagrass meadows disappear around the world, along with their associated biodiversity and numerous ecosystem services, efforts have been made to restore these critical ecosystems. However, restoration success rates are... [ view full abstract ]
As seagrass meadows disappear around the world, along with their associated biodiversity and numerous ecosystem services, efforts have been made to restore these critical ecosystems. However, restoration success rates are low (37%), due to habitat degradation and the disappearance of critical feedbacks regulating seagrass ecosystems, which are often not addressed in restoration projects.
Using a combined approach including meta-analysis, aquarium experiments, and field studies, we studied interactions and feedbacks between seagrasses and bivalves to understand the factors and mechanisms involved, and to determine how they could be applied in a restoration context. In the meta-analysis, interactions between seagrasses and bivalves were mostly positive, except between infaunal bivalves and intertidal seagrasses. We then used a series of field and aquarium experiments across Europe (using local species) to test whether adding infaunal and epifaunal bivalves in different environmental conditions increased restoration success, i.e. the survival, growth, and reproduction of planted seagrass.
In the lab, epifaunal bivalves increased seagrass growth through sediment fertilization and seed retention in high hydrodynamic conditions, while seagrass presence supported bivalve growth. However, results were less consistent in the field, as in some sites degraded environmental conditions (e.g. algal blooms, sedimentation, erosion, invasive species) reduced seagrass survival. The most critical aspect of seagrass restoration and conservation must thus be to first reduce anthropogenic impacts and ensure suitable environmental conditions. However, once these are in place, our results support the idea that promoting positive feedbacks by planting seagrass along with other ecosystem engineers together can indeed increase restoration success.
