Seafloor biodiversity affects sediment nutrient cycling

The global decline of biodiversity highlights the urgent need to understand how biodiversity contributes to ecosystem functionality. In the Baltic Sea, eutrophication-induced oxygen deficiency or hypoxia is the major problem for animals living on the seafloor. Hypoxia has resulted in dead or impoverished seafloor communities over vast areas.

Stressed benthic animals at the sediment surface [Credit: University of Helsinki]

"It is known that the biodiversity of seafloor communities is vital for healthy marine ecosystems, but we have very limited evidence from natural communities. 

Most of our current knowledge is based on laboratory experiments and modelling. 

Instead of that, we dived and did our experiments on the seafloor itself," says researcher Anna Villnäs from Tvärminne Zoological Station, University of Helsinki, Finland.

In a pioneering field experiment, the biodiversity of natural seafloor communities was changed through experimental manipulation of oxygen deficiency. 

The research group at Tvärminne Zoological Station shows how hypoxic disturbance degrades the structure and function of seafloor communities. 

Sampling the experiment [Credit: University of Helsinki]

The animals on the seafloor can withstand about one week of hypoxia, but after that most species die. The in situ evidence shows that impoverished seafloor biodiversity leads to changes in sediment nutrient cycling.

Due to a naturally low-diverse fauna, the seafloors of the Baltic Sea only have a few species that perform similar functions, which lowers the buffering capacity of the system towards disturbances. 

Therefore the authors argue that preservation of species at sufficient abundances is essential for maintaining a healthy seafloor and for sustaining functions, such as sediment nutrient cycling, in the Baltic Sea.

The research has been published online in the PLOS ONE journal.

Source: University of Helsinki [October 25, 2012]