CIE Spotlight: No detectable impact of small-scale disturbances on ‘blue carbon’ within seagrass beds

Peter M.

Peter M.

TitleNo detectable impact of small-scale disturbances on ‘blue carbon’ within seagrass beds.

AuthorsMacreadie, Peter I.; York, Paul H.; Sherman, Craig D. H.; Keough, Michael J.; Ross, D. Jeff; Ricart, Aurora M.; Smith, Timothy M.

Source: MARINE BIOLOGY, 161 (12):2939-2944, DEC 2014.

Brief summary of the paper: Seagrass meadows are among the most efficient and long-term carbon sinks on earth, but disturbances could threaten this capacity, so understanding the impacts of disturbance on carbon stored within seagrass meadows-‘blue carbon’-is of prime importance. To date, there have been no published studies on the impacts of seagrass loss on ‘blue carbon’ stocks.

We experimentally created several kinds of small-scale disturbances, representative of common grazer and boating impacts, within seagrass (Zostera nigracaulis) meadows in Port Phillip Bay (Australia) and measured the impacts on sediment organic carbon stocks (‘C-org’, and other geochemical variables-%N, delta C-13, delta N-15).

Disturbance had no detectable effect on C-org levels within seagrass sediments, even for high-intensity disturbance treatments, which remained bare (i.e. no seagrass recovery) for 2 years after the disturbance.

These findings challenge the widely held assumption that disturbance and concomitant loss of seagrass habitat cause release of carbon, at least for small-scale disturbances.

We suggest that larger (e.g. meadow scale) disturbances may be required to trigger losses of ‘blue carbon’ from seagrass meadows.