Chapter 7 Carbon Flux in Seagrasses
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Fig. 7. Seagrass leaf litter decomposition. Top left: Typical litter bags used in the classical experiments for determining seagrass leaf
litter in situ decay rates. The mesh size of the bags, as in the image, is usually 1 mm. The bags in the picture contain Posidonia oceanica
senescent leaf litter. Top right: Round-shaped bacteria growing on P. oceanica leaf litter adhering by extracellular polymers. Bottom:
Bacteria dividing on P. oceanica leaf litter (photographs by M. A. Mateo).
through the bag pores in P. oceanica. When comparing the results from both methods on a carbon
basis, it was found that only 40% of the weight lost
from the bags was actually attributable to microdecomposer activity (Figs. 7 right and bottom and
8) and the rest would seem to have been lost through
the bag pores. This conclusion, however, has to be
taken with caution because of the well-known limitations of microcosm experiments. However, it is
also possible that respiration rates in situ may have
been much higher owing to a higher water nutrient
renewal.
Despite the fact that decay rate estimates using
litter bags are not the most adequate for ecosystem