Biotic and abiotic data for: European Benthic survey of seagrass-lucinid mutualism

Coastal ecosystem functioning often hinges on habitat-forming foundation
species that engage in positive interactions (e.g. facilitation and
mutualism) to reduce environmental stress. Seagrasses are important
foundation species in coastal zones but are rapidly declining with losses
typically linked to intensifying global change-related environmental
stress. There is growing evidence that loss or disruption of positive
interactions can amplify coastal ecosystem degradation as it compromises
its stress-mitigating capacity. Multiple recent studies highlight that
seagrass can engage in a facultative mutualistic relationship with lucinid
bivalves that alleviate sulphide toxicity. So far, however, the generality
of this mutualism, and how its strength and relative importance depend on
environmental conditions, remains to be investigated. Here we study the
importance of the seagrass-lucinid mutualistic interaction on a
continental scale using a field survey across Europe. We found that the
lucinid bivalve Loripes orbiculatus is associated with the seagrasses
Zostera noltii and Zostera marina across a large latitudinal range. At
locations where the average minimum temperature was above 1°C, L.
orbiculatus was present in 79% of the Zostera meadows; whereas, it was
absent below this temperature. At locations above this minimum temperature
threshold, mud content was the second most important determinant
explaining the presence or absence of L. orbiculatus. Further analyses
suggest that the presence of the lucinids have a positive effect on
seagrass biomass by mitigating sulphide stress. Finally, results of a
structural equation model (SEM) support the existence of a mutualistic
feedback between L. orbiculatus and Z. noltii. We argue that this
seagrass-lucinid mutualism should be more solidly integrated into
management practices to improve seagrass ecosystem resilience to global
change as well as the success of restoration efforts.