274
J.R. Cantera and J.F. Blanco
the fall of rivers fuel primary production of phytoplankton, macroalgae,
and mangroves. The tidal, high-turbidity zone of rivers has higher chlorophyll concentrations than non-tidal upstream zones (i.e. chlorophyll-a
0.16-0.10 jlg 1- 1 ; chlorophyll-b O.ll-0.06jlg 1- 1 ; chlorophyll-c 0.230.1jlg 1- 1 ). Owing to increased nutrient levels and lower water turbidity,
concentrations increase in February-March and May-June, suggesting high
phytoplankton biomass and photosynthetic oxygen production (Bejarano
1996). Mangroves appear to be highly productive, with red (Rhizophora
mangle 960-4,800kg ha- 1 year- 1 ; R. racemosa 1,800-7,200kg ha- 1 year- 1 )
and black (Avicennia germinans 240-1,440kg ha- 1 year- 1 ) mangrove species contributing the most to total litter production (Prahl et al. 1990). The
average annual litter production ranges from 9.6 tons ha- 1 in bar mangroves to 11.4 tons ha- 1 in riverine mangroves (Lasso and Cantera 1995),
but is much lower in disturbed riverine mangroves (7.5 tons ha- 1 year- 1 ;
Garcia and Garces 1984). Owing to high photosynthetic rates (24-38mg C
per g dry wt. and day), the mangrove macroalgae community contributes
about 23-26% to the total annual mangrove production (Pefia 1998).
18.4.2 Food Webs
The organic carbon of primary production processes enters the food web
of Buenaventura Bay via herbivory or decomposition pathways as particulate (POM) or dissolved organic matter (DOM). Decomposition of the
large (85.5 g m- 2 ) macroalgal biomass (Bejarano 1996) takes about
120 days, with rates of 0.58 g day- 1 during the first 20 days which increase
proximate to muddy bottom sediments. Herbivory on mangroves is
largely restricted to leaves (84.9%), though only a small part of the total
leaf area (A. germinans 4.9 o/o, L. racemosa 4.7 o/o, R. mangle 2.3 o/o, P. rhizophorae 2.06 o/o) is removed. As a consequence, the grazing impact on
well-developed mangrove stands in Buenaventura Bay ranges from
428.8kg ha- 1 year- 1 in A. germinans and 413kg ha- 1 year- 1 in L. racemosa
to about 247.2kg ha- 1 year- 1 in R. mangle and 200.8 kg ha- 1 year- 1 in Pellicera rhizophorae (Romero 1998). The principal primary consumers of
mangrove leaf tissue are insects (Scotylidae, Saturnidae, Sphingidae),
crabs ( Goniopsis pulchra, Aratus pisonii, Pachygrapsus transversus,
Sesarma spp., Armases sp.), and some periwinkles (Littorinidae). The
decomposition of the leaf litter presents the most important energy
pathway. The dead leaves are initially colonized by microorganisms (i.e.
the fungi Pestalotiopsis, Penicillium, Aspergillus, Fusarium, Trichoderma,
Ceriosporopsis, Pontogenia). The decomposing litter and microorganisms
are then ingested by gastropods (Theodoxus, Melampus, Ellobium, Mari-
J.R. Cantera and J.F. Blanco
the fall of rivers fuel primary production of phytoplankton, macroalgae,
and mangroves. The tidal, high-turbidity zone of rivers has higher chlorophyll concentrations than non-tidal upstream zones (i.e. chlorophyll-a
0.16-0.10 jlg 1- 1 ; chlorophyll-b O.ll-0.06jlg 1- 1 ; chlorophyll-c 0.230.1jlg 1- 1 ). Owing to increased nutrient levels and lower water turbidity,
concentrations increase in February-March and May-June, suggesting high
phytoplankton biomass and photosynthetic oxygen production (Bejarano
1996). Mangroves appear to be highly productive, with red (Rhizophora
mangle 960-4,800kg ha- 1 year- 1 ; R. racemosa 1,800-7,200kg ha- 1 year- 1 )
and black (Avicennia germinans 240-1,440kg ha- 1 year- 1 ) mangrove species contributing the most to total litter production (Prahl et al. 1990). The
average annual litter production ranges from 9.6 tons ha- 1 in bar mangroves to 11.4 tons ha- 1 in riverine mangroves (Lasso and Cantera 1995),
but is much lower in disturbed riverine mangroves (7.5 tons ha- 1 year- 1 ;
Garcia and Garces 1984). Owing to high photosynthetic rates (24-38mg C
per g dry wt. and day), the mangrove macroalgae community contributes
about 23-26% to the total annual mangrove production (Pefia 1998).
18.4.2 Food Webs
The organic carbon of primary production processes enters the food web
of Buenaventura Bay via herbivory or decomposition pathways as particulate (POM) or dissolved organic matter (DOM). Decomposition of the
large (85.5 g m- 2 ) macroalgal biomass (Bejarano 1996) takes about
120 days, with rates of 0.58 g day- 1 during the first 20 days which increase
proximate to muddy bottom sediments. Herbivory on mangroves is
largely restricted to leaves (84.9%), though only a small part of the total
leaf area (A. germinans 4.9 o/o, L. racemosa 4.7 o/o, R. mangle 2.3 o/o, P. rhizophorae 2.06 o/o) is removed. As a consequence, the grazing impact on
well-developed mangrove stands in Buenaventura Bay ranges from
428.8kg ha- 1 year- 1 in A. germinans and 413kg ha- 1 year- 1 in L. racemosa
to about 247.2kg ha- 1 year- 1 in R. mangle and 200.8 kg ha- 1 year- 1 in Pellicera rhizophorae (Romero 1998). The principal primary consumers of
mangrove leaf tissue are insects (Scotylidae, Saturnidae, Sphingidae),
crabs ( Goniopsis pulchra, Aratus pisonii, Pachygrapsus transversus,
Sesarma spp., Armases sp.), and some periwinkles (Littorinidae). The
decomposition of the leaf litter presents the most important energy
pathway. The dead leaves are initially colonized by microorganisms (i.e.
the fungi Pestalotiopsis, Penicillium, Aspergillus, Fusarium, Trichoderma,
Ceriosporopsis, Pontogenia). The decomposing litter and microorganisms
are then ingested by gastropods (Theodoxus, Melampus, Ellobium, Mari-