The unique experiment, which was conducted simultaneously at 15 sites across the northern hemisphere, showed that small invertebrates such as crustaceans and snails eat and control the algae that can otherwise smother seagrasses, and that animal communities with more species performed this biological service more efficiently. Interestingly, the effect of biodiversity was stronger than the effect of both water temperature and simulated eutrophication.

Field sampling in Kristineberg
Seagrass bed on the Swedish west coast.
Photo: Johan Eklöf

Seagrass beds are important nursery areas for fish and protect coastal areas against erosion, but are decreasing in the whole world. "We have for long sought to improve the coastal environment and the health of seagrasses by reducing nutrient loads. But our study suggests it is equally important to maintain a high diversity of herbivorous invertebrates, as this keeps seagrass meadows clean of algae", says Johan Eklöf.

The global experiment has not only produced an important confirmation of the importance of biodiversity. It has also established a unique collaboration model to pursue large-scale ecological research - the Zostera Experimental Network (ZEN, - where researchers and students from seven countries cooperated. "Difficult global challenges in ecology - from climate change to fisheries management - require global strategies. Partnerships such as the Zostera Experimental Network gives us a unique opportunity to study and hopefully resolve these challenges in the coastal ecosystem," said Pamela Reynolds, program director for ZEN and postdoctoral researcher at the Virginia Institute of Marine Sciences and the University of California, Davis.

The crustacean Gammarus locusta is an efficient grazer on filamentous algae.
Photo: Johan Eklöf

ZEN is now in its second phase and has expanded to include 25 institutions working in over 50 locations, from the Russian Arctic to Mexico and South Korea. At the moment the team are studying how biodiversity of both small animals and plants contributes to fish production, carbon storage and other ecosystem services.

The study was published in Ecology Letters and supported by grants from the US National Science Foundation and local support from the 15 partner institutions (including Formas and Vetenskapsrådet in Sweden).

Link to the publication: