The Convergence Ecosystem in the Southwest Atlantic
153
(Odebrecht 1997). Cell concentration of large dinoflagellates (Noctiluca
scintillans, Polykrikos schwartzii, Protoperidinium spp.) and of naked
(Strombidium) and loricate (tintinnids) ciliates tend to coincide with
phytoplankton concentration, higher values being common in coastal surface waters or under the influence of nutrient-rich SAW and SACW. In oligotrophic warm waters of the Brazil Current, small ( <20 11m) naked ciliates
are important.
Zooplankton ( copepods, mysids, euphausiids, cladocerans, ostracods,
chaetognaths, tunicates, medusae, siphonophores, polychaetes, mollusks)
species composition and spatial and temporal distribution depend on the
dominance of different water masses (Boltovskoy 1981; Montu et al. 1997).
Copepods (up to 2,000 org. m- 3 ) constitute the most abundant group in
neritic (Acartia tonsa, Calanoides carinatus, Calanus australis, Centropages brachiatus, Ctenocalanus van us, Euterpina acutifrons, Oithona nana,
0. similis, Paracalanus parvus, P. quasimodo, Temora stylifera) and oceanic
(Acartia danae, Calanus simillimus, Conaea rapax, Corycaeus furcifer,
Oncaea venusta, Rhyncalanus nasutus, Sapphirina spp.) waters (Montu et
al. 1997). Mysids, like Metamysidopsis elongata and Neomysis americana,
may constitute up to 90 o/o of the surf zone zooplankton. Adult euphausiids
are more common in oceanic regions under the influence of SAW
(Euphausia longirostris, E. lucens, E. spinifera) and TW (Euphausia similis,
E. hemigibba, E. recurva, Stylocheiron abbreviatum, S. affine, Thysanopoda
spp.; Brinton and Antezana 1981; Montu et al. 1997). Cladocerans (Evadne
nordmanni, Penilia avirostris, Pleopis polyphemoides, Podon intermedius,
P. schmacheri, Pseudoevadne tergestina) are mainly neritic with highest
concentration and number of species in winter (Montu et al. 1997). Several
species of chaetognaths are water masses indicators. Sagitta tenuis is a
common coastal and shelf species, while the distribution of S. enflata, S.
serratodentata, S. minima, S. hispida, and Pterosagitta draco extends over
the shelf and slope (Boltovskoy 1981; Montu et al. 1997). Different species
of appendicularian tunicates are abundant in nearshore ( Oikopleura dioica), shelf and slope ( Oikopleura longicauda, 0. fusiform is, 0. rufescens,
Fritillaria borealis, F. pellucida), or in oceanic waters (Fritillaria formica,
Oikopleura albicans, 0. cophocerca, Stegosoma magnum; Montu et al.
1997). Thaliaceans, coelenterate medusae and siphonophores, and shelled
planktonic pteropod mollusks are occasionally common.
11.4.2 Macrobenthic Invertebrates
The unstable conditions of the shallow inner shelf under influence of turbid Patos Lagoon freshwater runoff largely impede the colonization by spe-
153
(Odebrecht 1997). Cell concentration of large dinoflagellates (Noctiluca
scintillans, Polykrikos schwartzii, Protoperidinium spp.) and of naked
(Strombidium) and loricate (tintinnids) ciliates tend to coincide with
phytoplankton concentration, higher values being common in coastal surface waters or under the influence of nutrient-rich SAW and SACW. In oligotrophic warm waters of the Brazil Current, small ( <20 11m) naked ciliates
are important.
Zooplankton ( copepods, mysids, euphausiids, cladocerans, ostracods,
chaetognaths, tunicates, medusae, siphonophores, polychaetes, mollusks)
species composition and spatial and temporal distribution depend on the
dominance of different water masses (Boltovskoy 1981; Montu et al. 1997).
Copepods (up to 2,000 org. m- 3 ) constitute the most abundant group in
neritic (Acartia tonsa, Calanoides carinatus, Calanus australis, Centropages brachiatus, Ctenocalanus van us, Euterpina acutifrons, Oithona nana,
0. similis, Paracalanus parvus, P. quasimodo, Temora stylifera) and oceanic
(Acartia danae, Calanus simillimus, Conaea rapax, Corycaeus furcifer,
Oncaea venusta, Rhyncalanus nasutus, Sapphirina spp.) waters (Montu et
al. 1997). Mysids, like Metamysidopsis elongata and Neomysis americana,
may constitute up to 90 o/o of the surf zone zooplankton. Adult euphausiids
are more common in oceanic regions under the influence of SAW
(Euphausia longirostris, E. lucens, E. spinifera) and TW (Euphausia similis,
E. hemigibba, E. recurva, Stylocheiron abbreviatum, S. affine, Thysanopoda
spp.; Brinton and Antezana 1981; Montu et al. 1997). Cladocerans (Evadne
nordmanni, Penilia avirostris, Pleopis polyphemoides, Podon intermedius,
P. schmacheri, Pseudoevadne tergestina) are mainly neritic with highest
concentration and number of species in winter (Montu et al. 1997). Several
species of chaetognaths are water masses indicators. Sagitta tenuis is a
common coastal and shelf species, while the distribution of S. enflata, S.
serratodentata, S. minima, S. hispida, and Pterosagitta draco extends over
the shelf and slope (Boltovskoy 1981; Montu et al. 1997). Different species
of appendicularian tunicates are abundant in nearshore ( Oikopleura dioica), shelf and slope ( Oikopleura longicauda, 0. fusiform is, 0. rufescens,
Fritillaria borealis, F. pellucida), or in oceanic waters (Fritillaria formica,
Oikopleura albicans, 0. cophocerca, Stegosoma magnum; Montu et al.
1997). Thaliaceans, coelenterate medusae and siphonophores, and shelled
planktonic pteropod mollusks are occasionally common.
11.4.2 Macrobenthic Invertebrates
The unstable conditions of the shallow inner shelf under influence of turbid Patos Lagoon freshwater runoff largely impede the colonization by spe-