Artificial tidepools promote marine diversity on Dutch sea-dikes

Marine construction homogenise coastal ecosystems by replacing a diverse array of shoreline habitats with artificial hard structures, such as seawalls and jetties. Climate adaptation will further increase shoreline hardening, posing an additional threat to coastal biodiversity. We therefore addressed the urgent need for practically oriented research on how to best promote marine biodiversity on different types of artificial substrates by testing the effects of enriching a Dutch sea-dike with artificial tidepools. For three years we monitored the development of different functional groups of sessile organisms on three different types of tidepools that were added in six clusters to the existing boulder base of a sea-dike. The artificial tidepools developed diverse sessile communities that included the common groups barnacles, green algae, bladderwrack, mussels and oysters; but also unique species groups, such as anemones, hydroids, red algae and colonial diatoms, that were otherwise absent or very rare on the sea-dike. Consequently, after three years, the taxonomic diversity of benthic organisms were 50 % higher in the artificial tidepools than on comparable rock habitats on the sea-dike, and the tidepool communities were more different from each other than from the other habitats on the dike. We demonstrate that artificial tidepools can play an important role in management interventions to increase habitat heterogeneity and bolster marine biodiversity on artificial substrates. • Artificial tidepools increase sessile biodiversity with 50 % on Dutch sea dikes. • Sessile communities rapidly develop in artificial tide pools in the Wadden Sea. • Different tide pool constructions promote different biological communities. • Artificial tidepools increase habitat heterogeneity and promote marine biodiversity.