The Itamaraca Estuarine Ecosystem, Brazil
77
ries. The productivity of the plankton community decreases from estuarine
areas towards the ocean. However, despite the hydrographic barrier between estuarine and shelf waters, the export of diatoms, larvae of bivalves,
gastropods, and cirripedes is significant. Especially Brachyura zoeae are
exported at high rates (1.5 x 10 8 zoeae day-- 1 ; Wehrenberg 1996) to coastal
waters (10-20 km offshore) and are occasionally more abundant than
copepods (Schwamborn 1997). Since both copepods and zoeae are important food sources for various species of fish (Vasconcelos et al. 1984;
Morgan 1990; Sautour et al. 1996), their export is likely to fuel the marine
food web.
Around the islands and in the "inner sea" extensive and productive
(approx. 3 tons dry weight per ha and year) sea grass meadows of Halodule wrightii (Kempf 1970) constitute a substrate for epifaunal organisms
(mollusks and crustaceans). The associated macrofauna is dominated by
the mollusk Tricolia affins. The most abundant taxa among decapod crustaceans are pangurid hermit crabs (Panguridae) and the shrimp Hippolyte
curacaoensis (Caridae). The approximately 70 species of fish in the Santa
Cruz Channel (365 kg ha- 1 year-') are represented by the families Mugilidae (Mugil curema, M. liza, Mugil sp.), Centropomidae (Centropomus
parallelus, C. undecimalis), Gerreidae (Eugerres brasilianus, Diapterus
olisthostomus), Clupeidae (Opisthonema oglinum), Hemirhamphidae
(Hypohamphus unifasciatus, Hemirhampus brasiliensis), Carangidae
( Caranx fatus ), and Ariidae (Arius parkeri, A. proops; Eskinazi 1972; Azevedo and Guedes 1973).
The bird fauna (71 species of 30 families) of the Itamaraca estuarine
system is represented by resident and migratory species. Common residents (i.e., Butorides striatus, Conirostrum bicolor, Chloroceryle americana, and the kingfisher Ceryle torquata) are related to mangrove habitats.
Other species, like wading birds (Jacana jacana, Porphirula martinica),
river swallow (Tachycineta albiventer), seagull (Larus maculipenis), sea
tern (Sterna eurygnatha), tyrant flycatcher (Pitangris sulphuratus), and
tanager (Thraupis sayaca) are found on riverine and estuarine flood
plains, reefs, and beaches. Migratory birds (i.e., Pluvial is squatarola, Charadrius semipalmatus, Arenaria interpres, Calidria pusilla, C. alba) stay
from August to April in the Santa Cruz Channel area to feed and change
their plumage (Azevedo 1992). The manatee (Trichechus manathus), a
native species of north and northeastern Brazil, with an estimated population of 400 individuals, occurs in sea grass beds around Itamaraca Island
but is in danger of extinction.
77
ries. The productivity of the plankton community decreases from estuarine
areas towards the ocean. However, despite the hydrographic barrier between estuarine and shelf waters, the export of diatoms, larvae of bivalves,
gastropods, and cirripedes is significant. Especially Brachyura zoeae are
exported at high rates (1.5 x 10 8 zoeae day-- 1 ; Wehrenberg 1996) to coastal
waters (10-20 km offshore) and are occasionally more abundant than
copepods (Schwamborn 1997). Since both copepods and zoeae are important food sources for various species of fish (Vasconcelos et al. 1984;
Morgan 1990; Sautour et al. 1996), their export is likely to fuel the marine
food web.
Around the islands and in the "inner sea" extensive and productive
(approx. 3 tons dry weight per ha and year) sea grass meadows of Halodule wrightii (Kempf 1970) constitute a substrate for epifaunal organisms
(mollusks and crustaceans). The associated macrofauna is dominated by
the mollusk Tricolia affins. The most abundant taxa among decapod crustaceans are pangurid hermit crabs (Panguridae) and the shrimp Hippolyte
curacaoensis (Caridae). The approximately 70 species of fish in the Santa
Cruz Channel (365 kg ha- 1 year-') are represented by the families Mugilidae (Mugil curema, M. liza, Mugil sp.), Centropomidae (Centropomus
parallelus, C. undecimalis), Gerreidae (Eugerres brasilianus, Diapterus
olisthostomus), Clupeidae (Opisthonema oglinum), Hemirhamphidae
(Hypohamphus unifasciatus, Hemirhampus brasiliensis), Carangidae
( Caranx fatus ), and Ariidae (Arius parkeri, A. proops; Eskinazi 1972; Azevedo and Guedes 1973).
The bird fauna (71 species of 30 families) of the Itamaraca estuarine
system is represented by resident and migratory species. Common residents (i.e., Butorides striatus, Conirostrum bicolor, Chloroceryle americana, and the kingfisher Ceryle torquata) are related to mangrove habitats.
Other species, like wading birds (Jacana jacana, Porphirula martinica),
river swallow (Tachycineta albiventer), seagull (Larus maculipenis), sea
tern (Sterna eurygnatha), tyrant flycatcher (Pitangris sulphuratus), and
tanager (Thraupis sayaca) are found on riverine and estuarine flood
plains, reefs, and beaches. Migratory birds (i.e., Pluvial is squatarola, Charadrius semipalmatus, Arenaria interpres, Calidria pusilla, C. alba) stay
from August to April in the Santa Cruz Channel area to feed and change
their plumage (Azevedo 1992). The manatee (Trichechus manathus), a
native species of north and northeastern Brazil, with an estimated population of 400 individuals, occurs in sea grass beds around Itamaraca Island
but is in danger of extinction.