The Cabo Frio Upwelling System, Brazil
101
Simultaneous peaks of phyto- and zooplankton abundance in the Cabo
Frio upwelling system indicate equilibrium between these trophic levels
and an advanced state of system maturity, generally attributed to oligotrophic waters. The process, which synchronizes phyto- and zooplankton
variations, depends on phytoplankton bloom-induced spawning of herbivores during upwelling. Drift currents carry the larvae to the open sea
where they undergo ontogenic vertical migration and return as adults to
coastal surface waters if the interval between consecutive upwellings
approximately corresponds to the duration of their life cycle. The synchronization increases the rate of grazing and reduces peaks of primary biomass. The quali-quantitative variations in phytoplankton translate into
changes of zooplankton species composition as a result of different feeding
regimes. A model of zooplankton succession in Cabo Frio waters (Valentin
1988) suggests that during periods of phytoplankton maxima, opportunistic herbivores (Paracalanus parvus, Oikopleura longicauda, Thalia
democratica, Calanoides carinatus) and opportunistic carnivores (Sagitta
enflata) dominate. During post-maxima periods, facultative herbivores,
predators, and detritivores are Ctenocalanus van us, Creseis acicula, Pen ilia
avirostris, Doliolum spp., and the genera Eucalanus and Clausocalanus.
Detritivores and omnivores are represented by Temora stylifera, Centropages furcatus, Euterpina acutifrons, Nannocalanus minor, Oithona plumifera, and the genus Conchaecia while carnivores are Sagitta enflata, siphonophores, and copepods of the families Euchaetidae, Candaciidae, and
Pontellidae.
7.3.2 Benthos
Large temperature variations ( 10 °C) within hours, high nutrient input, and
phytoplankton bloom impact the structure of the benthic community.
Owing to a wide variety of physical and biological conditions (Boudouresque and Yoneshigue 1983), the macroflora of rocky shore communities
of the Cabo Frio region displays high diversity with a large number of Rhodophyta (64.5 %), Phaeophyta (18.6 %), and Chlorophyta (16.8 %) (Yoneshigue 1985). The species richness among Phaeophyta at the tropical latitude of Cabo Frio is unusual and characterizes the local flora as
intermediate with warm-temperate affinities, confirming the biogeographic importance of the Cabo Frio barrier (de Oliveira Filho 1977). Sites
with temperate affinities and a Porphyra assemblage contrast with tropical
sites and Sargassum/Zonaria and Caulerpa assemblages, while other sites
have mixed communities. Pterocladiella capillacea develops high biomass
at exposed sites as a result of the combined effect of cold, nutrient-rich
101
Simultaneous peaks of phyto- and zooplankton abundance in the Cabo
Frio upwelling system indicate equilibrium between these trophic levels
and an advanced state of system maturity, generally attributed to oligotrophic waters. The process, which synchronizes phyto- and zooplankton
variations, depends on phytoplankton bloom-induced spawning of herbivores during upwelling. Drift currents carry the larvae to the open sea
where they undergo ontogenic vertical migration and return as adults to
coastal surface waters if the interval between consecutive upwellings
approximately corresponds to the duration of their life cycle. The synchronization increases the rate of grazing and reduces peaks of primary biomass. The quali-quantitative variations in phytoplankton translate into
changes of zooplankton species composition as a result of different feeding
regimes. A model of zooplankton succession in Cabo Frio waters (Valentin
1988) suggests that during periods of phytoplankton maxima, opportunistic herbivores (Paracalanus parvus, Oikopleura longicauda, Thalia
democratica, Calanoides carinatus) and opportunistic carnivores (Sagitta
enflata) dominate. During post-maxima periods, facultative herbivores,
predators, and detritivores are Ctenocalanus van us, Creseis acicula, Pen ilia
avirostris, Doliolum spp., and the genera Eucalanus and Clausocalanus.
Detritivores and omnivores are represented by Temora stylifera, Centropages furcatus, Euterpina acutifrons, Nannocalanus minor, Oithona plumifera, and the genus Conchaecia while carnivores are Sagitta enflata, siphonophores, and copepods of the families Euchaetidae, Candaciidae, and
Pontellidae.
7.3.2 Benthos
Large temperature variations ( 10 °C) within hours, high nutrient input, and
phytoplankton bloom impact the structure of the benthic community.
Owing to a wide variety of physical and biological conditions (Boudouresque and Yoneshigue 1983), the macroflora of rocky shore communities
of the Cabo Frio region displays high diversity with a large number of Rhodophyta (64.5 %), Phaeophyta (18.6 %), and Chlorophyta (16.8 %) (Yoneshigue 1985). The species richness among Phaeophyta at the tropical latitude of Cabo Frio is unusual and characterizes the local flora as
intermediate with warm-temperate affinities, confirming the biogeographic importance of the Cabo Frio barrier (de Oliveira Filho 1977). Sites
with temperate affinities and a Porphyra assemblage contrast with tropical
sites and Sargassum/Zonaria and Caulerpa assemblages, while other sites
have mixed communities. Pterocladiella capillacea develops high biomass
at exposed sites as a result of the combined effect of cold, nutrient-rich