78
C. Medeiros et a!.
5.6 Trophic Relations
The ltamaraca estuarine ecosystem displays strong trophic interactions
between the pelagic and benthic compartment. While meroplanktonic larvae of benthic organisms (i.e., decapods) appear to feed on phytoplankton,
mangrove detritus is a significant food source for the copepod-rich haloplankton ( 13-40 %; Schwamborn 1997) as well as for the crabs Aratus
pisone, Ucides cordatus, and Goniopsis cruentata. High primary production
frequently causes hypoxia in bottom substrates, resulting in a meiobenthic
community with low diversity and strong dominance (143 ind. cm- 2 ) of
opportunistic species (polychaetes, nematodes, oligochaetes) which feed
on decomposing organic matter and associated bacteria and fungi. Plant
detritus and associated microflora and microfauna also comprise the diet
of ostracods and copepod Harpactidoida and of macroconsumers, such as
mollusks (Littorina australis, Tagellus plebeus, Neritina virginea), crustaceans ( Uca leptodactyla, U. rapax, U. maracoani, U. thayeri), and shrimps
(Penaeus schimiti, P. subtilis). Suspended detritus particles in the water
column are a food source for the oyster Crassostrea rhizophorae as well
as for shrimps. The fish species Arius parkeri, Arius proops, Diapterus
olisthostomus, and Eugerres brasilianus feed largely on invertebrates, such
as polychaetes, mollusks, and crustaceans. Important carnivores are Centropomus undecimalis, C. parallelus, and Caranx fatus. The planktivorous
fish Hemirhamphus brasiliensis and Hypohamphus unifasciatus feed upon
Acartia lilljeborgi, Paracalanus crassirostris, Oithona hebes, Oithona oswaldocruzi, Euterpina acutifron, Oikopleura dioica, and Sagitta tenuis among
others.
5.7 Environmental Problems
As most estuaries, the Itamaraca estuarine ecosystem is exposed to
multiple pressures from industrial pollution, domestic sewage discharge,
urban expansion and land reclamation, and fisheries. Raw domestic sewage is discharged from ltapissuma (population 19,000) into the Santa Cruz
Channel, thus coliform contamination in mangrove oysters tends to be
high. However, one of the major environmental problems in the estuary
has been the release of mercury (22-35 tons) into the Botafogo River by a
chlor-alkali factory between 1964 and 1987 (Meyer 1996). The impact ofHg
pollution was aggravated by the concomitant discharge of chlorine and
acid wastes from sugarcane mills, which increased Hg dissolution and
C. Medeiros et a!.
5.6 Trophic Relations
The ltamaraca estuarine ecosystem displays strong trophic interactions
between the pelagic and benthic compartment. While meroplanktonic larvae of benthic organisms (i.e., decapods) appear to feed on phytoplankton,
mangrove detritus is a significant food source for the copepod-rich haloplankton ( 13-40 %; Schwamborn 1997) as well as for the crabs Aratus
pisone, Ucides cordatus, and Goniopsis cruentata. High primary production
frequently causes hypoxia in bottom substrates, resulting in a meiobenthic
community with low diversity and strong dominance (143 ind. cm- 2 ) of
opportunistic species (polychaetes, nematodes, oligochaetes) which feed
on decomposing organic matter and associated bacteria and fungi. Plant
detritus and associated microflora and microfauna also comprise the diet
of ostracods and copepod Harpactidoida and of macroconsumers, such as
mollusks (Littorina australis, Tagellus plebeus, Neritina virginea), crustaceans ( Uca leptodactyla, U. rapax, U. maracoani, U. thayeri), and shrimps
(Penaeus schimiti, P. subtilis). Suspended detritus particles in the water
column are a food source for the oyster Crassostrea rhizophorae as well
as for shrimps. The fish species Arius parkeri, Arius proops, Diapterus
olisthostomus, and Eugerres brasilianus feed largely on invertebrates, such
as polychaetes, mollusks, and crustaceans. Important carnivores are Centropomus undecimalis, C. parallelus, and Caranx fatus. The planktivorous
fish Hemirhamphus brasiliensis and Hypohamphus unifasciatus feed upon
Acartia lilljeborgi, Paracalanus crassirostris, Oithona hebes, Oithona oswaldocruzi, Euterpina acutifron, Oikopleura dioica, and Sagitta tenuis among
others.
5.7 Environmental Problems
As most estuaries, the Itamaraca estuarine ecosystem is exposed to
multiple pressures from industrial pollution, domestic sewage discharge,
urban expansion and land reclamation, and fisheries. Raw domestic sewage is discharged from ltapissuma (population 19,000) into the Santa Cruz
Channel, thus coliform contamination in mangrove oysters tends to be
high. However, one of the major environmental problems in the estuary
has been the release of mercury (22-35 tons) into the Botafogo River by a
chlor-alkali factory between 1964 and 1987 (Meyer 1996). The impact ofHg
pollution was aggravated by the concomitant discharge of chlorine and
acid wastes from sugarcane mills, which increased Hg dissolution and