Community-based monitoring detects catastrophic earthquake and tsunami impacts on seagrass beds in the Solomon Islands.

Tetepare Island in the Solomon Islands is the largest uninhabited island in the South Pacific and supports seagrass beds inside fringing reefs along its coastline. We monitored the diversity and abundance of seagrass species on Tetepare and nearby sparsely-populated Rendova Island over a 12 year period, 4 years before and up to 8 years after a major earthquake and tsunami event in January 2010. Both seagrass cover and diversity declined after the tsunami and had not reached pre-Tsunami levels after 8 years. Seagrass cover declined the fastest at sites on Rendova, closest to the epicentre, declining from 50% to <10% cover within 12 months of the earthquake. At sites within the Tetepare MPA, seagrass cover took longer to decline and dropped from an average of 50% to <10% within 2 years and became dominated by Halophila ovalis. Species richness declined from 9 to 4 species with some species such as Syringodium isoetifolium disappearing from monitoring sites. Community-based monitoring was an effective method of documenting long term changes in seagrass cover and long-term monitoring is required to determine if seagrass beds are permanently altered or return to pre-tsunami conditions.