Wednesday, 09 February 2011
The extent of dredging in coastal environments has rapidly increased in recent years, as a consequence of the growth in the minerals and energy export sectors. Dredging for new ports now poses a major threat to many marine ecosystems, including seagrass ecosystems, and is a major focus of impact assessments and environmental management plans. Here, Kathryn, Paul & Mike have published the second paper from an extensive study into the effects of light-reductions associated with dredging on the seagrass Amphibolis griffithii. An earlier paper reported the impacts of shading, while this latest work reports the potential for the ecosystem to recover following the removal of shading. The meadow could recover from 3 months of shading, where plants received 5–18% of ambient light - after 10 months re-exposure to ambient light the meadow had recovered. This was a much faster recovery than has previously been observed for large seagrasses. However, when the meadow had been shaded for 6–9 months and more than 82% of leaf biomass was lost, no recovery was detected, even up to 23 months after the light shading had ceased. Five potential indicators of recovery were recommended.