Seagrass reproductive effort as an ecological indicator of disturbance

The available information on the changes in the reproductive effort (RE) of seagrasses in response to disturbances was reviewed and analysed to assess if seagrasses invest in RE when disturbed, and if this response is related to specific types of disturbance or seagrass traits. In 72% of the documented cases RE increased with disturbance, in 25% it decreased, and in 3% no changes were reported. Overall, seagrass RE increased 4-fold with disturbance. Anthropogenic disturbances had the highest impact on RE (a 13-fold increase); 3 times higher than the effect of natural disturbances. Mechanical and sedimentary/hydrodynamics disturbances caused the highest RE increase (9- and 5-fold, respectively). The positive RE response was significantly correlated with rhizome diameter of seagrasses, but not with shoot size (mass or length), suggesting that species with higher storage capacity have a higher capacity of investing in sexual reproduction when conditions deteriorate. Seagrasses showed a general trend of increasing RE under disturbance; this was evident regardless of the origin and type of disturbance, which suggests that changes in seagrass RE provide a valuable indicator of disturbance in coastal areas.