Publisher :
Place of publication :
Publication year : 2000
Thematic : Seagrasses
Language : English
Note
The input of organic matter and nutrients produced by mangrove and seagrass vegetation in
the intertidal bay on Inhaca island, Mozambique, was estimated. Mean mangrove tree height was
2.20 m, diameter at breast height was 6.4 cm and density was 6047 trees per hectare. Above-ground
biomass of mangrove was calculated at 107 t ha-1 and annual litterfall at 6 t ha-1. Above- and
below-ground biomass, shoot density, leaf size, number of leaves per shoot, production and production/
biomass (P/B) ratio of three different seagrass species, Cymodocea serrulata, Halodule
wrightii, and Zostera capensis, was measured. Shoot densities were low and plants small. Total dry
weight (DW) biomass was 18–198 gm-2, with higher values in summer, except for Z. capensis.
Production was 0.08–0.62 g DW per day, 2.2 times higher in summer, compared with winter, with
highest values recorded for C. serrulata. The P/B ratio varied from 3.2 to 5.8. The decomposition
decay constant K of mangrove and seagrass leaveswas 0.010–0.017; t50 values were 69 and 41 days,
respectively. Decomposition was faster at Saco, compared with the Banco area. Mean litter biomass
was higher at Saco, than at Banco (0.24 and 0.05 g ash-free DW per square metre, respectively),
with significant differences for litter type, season and substrate. The ratio of mangrove to seagrass
litter stock was equal to expected values, based on production and decomposition. Local differences
in litter stock could be explained by tidal current patterns. Litter production was estimated at 0.08
and 0.10 g ash-free DW per square metre, respectively, for the mangroves and seagrasses. The annual
input of mangroves into the system was estimated at 330 t C, 6 t N and 0.6 t P, whilst seagrass
produced more nutrients, 490 t C, 30 t N and 2 t P. This emphasised the importance of seagrass
vegetation as the dominant nutrient source of the system.
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Encoded by : Pauline Carmel Joy Eje
