Fiddling with the carbon budget: fiddler crab burrowing activity
increases wetland’s carbon flux
Abstract
Coastal wetlands store significant amounts of carbon through
sequestration. Salt marshes are also known to harbour high densities of
crabs, which increase the sediment-atmosphere exchange interface through
their burrowing behaviour. We hypothesized that this additional and
reactive interface area could mediate gas exchange and, ultimately,
could influence carbon sequestration. CO fluxes were measured over
patches characterized by different densities of fiddler crab, , burrows
within a natural salt marsh located on the coast of Massachusetts (USA).
Even accounting for the importance of ecological factors such as
differences in organic matter content of the soil and presence of , we
demonstrated that CO release increased if local crab burrow density is
considered. The increase in vertical CO fluxes linked to burrow density
was higher for the non-vegetated areas with respect to patches. By means
of burrow casting and morphological analyses of the burrows, we could
relate this difference in COfluxes to structural differences of the
burrows themselves, which were larger and deeper in the non-vegetated
areas. Our results strongly emphasize the importance of including the
faunal component, and specifically the dominant burrowing species, in
carbon budget assessments for vegetated coastal habitats. This study
also emphasizes the critical role of community-scale factors within the
salt marsh, which are often overlooked, for large scale carbon budget
assessments.