178
U. Seeliger
dance and high population turnover rates. Most ingest organic particles in
superficial sediments, but some nematodes also feed in deeper sediments
and therefore facilitate energy flow to the upper aerobic layers. Macrobenthic infaunal polychaetes (i.e., Laeonereis acuta), the pelecipod Tagelus
plebeius, and the peracarid Kalliapseudes schubartii ingest a mixture of
detritus particles and epibenthic microalgae of surface layers, whilst the
burrowing polychaete Heteromastus similis feeds on organic matter in
deeper ( <15 em) sediments. In general, the low infaunal diversity accounts
for abbreviated food chains though predation by the infaunal polychaete
Nephtys fluviatilis on Heteromastus similis acts as an important intermediate link for epifaunal macropredators. The macro benthic epifaunal deposit-feeding gastropods (i.e., Heleobia australis) and peracarids (i.e., the
tanaid Tanais stanfordii, the amphipod Mellita mangrovi, the isopod Dies
fluminensis) ingest detritus, diatoms and occasionally copepods in superficial sediments. Among the fishes, primary consumers are represented by
juveniles of Mugil curema, M. gaimardianus, and monospecific schools of
adult M. platanus, which ingest large quantities of detrital matter together
with epibenthic and epiphytic diatoms (Vieira et al. 1998).
Decapods and fishes typically represent second-level consumer species.
However, the omnivoruous decapods are able to act at different trophic
levels because they display ontogenetic changes in diet preference and/or
opportunistically exploit food sources as they become available. The early
life stages of Cyrtograpsus angulatus, Callinectes sapidus, Farfantepenaeus
paulensis, Chasmagnathus granulata, and Metasesarma rubripes largely
feed on detrital matter and on epibenthic and epiphytic microalgae. The
juveniles and sub-adults of Callinectes sapidus and Cyrtograpsus angulatus
and the crab Rhithropanopeus harrissi prey on meiobenthic and small inand epifaunal organisms, which represents an important link between
detrital matter and higher trophic levels. Larger individuals of Chasmagnathus granulata, Metasesarma rubripes, as well as juveniles of Micropogonias furnieri (Sciaenidae) and adults of Odontesthes argentinensis and
Atherinella brasiliensis (Atherinidae) selectively prey on meiobenthic
ostracods, nematodes, in- and epifaunal organisms, small decapods and
fishes. Especially epifaunal macrobenthic peracarids are an important
food source and provide a measure of predation by secondary consumers,
owing to their abundance and exposure (Bemvenuti 1997b ). Many primary
and secondary consumers of shallow shoals are preyed upon by wading
birds, like the common stilt (Himantopus himantopus), the hudsonian godwit (Limosa haemastica), and the rufous-chested dotterel ( Charadrius
modestus) (Fig. 12.3).
In deeper waters the abundant Erodona mactroides represents the most
important infaunal phytoplankton grazer. The larvae of both Erodona
U. Seeliger
dance and high population turnover rates. Most ingest organic particles in
superficial sediments, but some nematodes also feed in deeper sediments
and therefore facilitate energy flow to the upper aerobic layers. Macrobenthic infaunal polychaetes (i.e., Laeonereis acuta), the pelecipod Tagelus
plebeius, and the peracarid Kalliapseudes schubartii ingest a mixture of
detritus particles and epibenthic microalgae of surface layers, whilst the
burrowing polychaete Heteromastus similis feeds on organic matter in
deeper ( <15 em) sediments. In general, the low infaunal diversity accounts
for abbreviated food chains though predation by the infaunal polychaete
Nephtys fluviatilis on Heteromastus similis acts as an important intermediate link for epifaunal macropredators. The macro benthic epifaunal deposit-feeding gastropods (i.e., Heleobia australis) and peracarids (i.e., the
tanaid Tanais stanfordii, the amphipod Mellita mangrovi, the isopod Dies
fluminensis) ingest detritus, diatoms and occasionally copepods in superficial sediments. Among the fishes, primary consumers are represented by
juveniles of Mugil curema, M. gaimardianus, and monospecific schools of
adult M. platanus, which ingest large quantities of detrital matter together
with epibenthic and epiphytic diatoms (Vieira et al. 1998).
Decapods and fishes typically represent second-level consumer species.
However, the omnivoruous decapods are able to act at different trophic
levels because they display ontogenetic changes in diet preference and/or
opportunistically exploit food sources as they become available. The early
life stages of Cyrtograpsus angulatus, Callinectes sapidus, Farfantepenaeus
paulensis, Chasmagnathus granulata, and Metasesarma rubripes largely
feed on detrital matter and on epibenthic and epiphytic microalgae. The
juveniles and sub-adults of Callinectes sapidus and Cyrtograpsus angulatus
and the crab Rhithropanopeus harrissi prey on meiobenthic and small inand epifaunal organisms, which represents an important link between
detrital matter and higher trophic levels. Larger individuals of Chasmagnathus granulata, Metasesarma rubripes, as well as juveniles of Micropogonias furnieri (Sciaenidae) and adults of Odontesthes argentinensis and
Atherinella brasiliensis (Atherinidae) selectively prey on meiobenthic
ostracods, nematodes, in- and epifaunal organisms, small decapods and
fishes. Especially epifaunal macrobenthic peracarids are an important
food source and provide a measure of predation by secondary consumers,
owing to their abundance and exposure (Bemvenuti 1997b ). Many primary
and secondary consumers of shallow shoals are preyed upon by wading
birds, like the common stilt (Himantopus himantopus), the hudsonian godwit (Limosa haemastica), and the rufous-chested dotterel ( Charadrius
modestus) (Fig. 12.3).
In deeper waters the abundant Erodona mactroides represents the most
important infaunal phytoplankton grazer. The larvae of both Erodona