Abstract:
Vegetated marine habitats are globally important carbon sinks, making a significant contribution towards mitigating climate change, and they provide a wide range of other ecosystem
services. However, large gaps in knowledge remain, particularly for seagrass meadows in
Africa. The present study estimated biomass and sediment organic carbon (Corg) stocks of
four dominant seagrass species in Gazi Bay, Kenya. It compared sediment Corg between
seagrass areas in vegetated and un-vegetated ‘controls’, using the naturally patchy occurence of seagrass at this site to test the impacts of seagrass growth on sediment Corg. It also
explored relationships between the sediment and above-ground Corg, as well as between
the total biomass and above-ground parameters. Sediment Corg was significantly different
between species, range: 160.7–233.8 Mg C ha-1 (compared to the global range of 115.3 to
829.2 Mg C ha-1). Vegetated areas in all species had significantly higher sediment Corg compared with un-vegetated controls; the presence of seagrass increased Corg by 4–6 times.
Biomass carbon differed significantly between species with means ranging between 4.8–7.1
Mg C ha-1 compared to the global range of 2.5–7.3 Mg C ha-1. To our knowledge, these are
among the first results on seagrass sediment Corg to be reported from African seagrass
beds; and contribute towards our understanding of the role of seagrass in global carbon
dynamics.
