Probable collapse of seagrass beds: evidence from a preserved subtropical intertidal ecosystem

Worldwide, eutrophication is presented as one of the causes underlying the significant losses in seagrass beds. As the effects of the nutrient load vary along environmental gradients, it is expected that the strength of the waves in particular would impact the stability of meadows, the nutrient status as well as nutrient supply responses.

An experience conducted in Mauritania to establish the main features of Zostera noltei through a survey of the Banc d’Arguin preserved subtropical intertidal meadow system has shown that the hydrodynamic gradient has a strong spatio-temporal impact on the nutrient status and stability of meadows, for which the increasing wave action is commensurate with the nutrient limitation and stability of meadows.

Similarly, it was observed that the magnitude of the effect of an increased nutrient load on meadows was closely related to wave exposure. The more exposed the area, the greater the risks for a loss of biomass as a result of fertilisation, unlike protected areas. The findings also suggest that, to a large extent, nitrogen is a limiting factor for the Banc d’Arguin intertidal meadows.