The Patos Lagoon Estuary, Brazil
169
ments by inflowing seawater and strong winds (Niencheski and Baumgarten 1997).
12.3 Estuarine Habitats
The size and the physiographic heterogeneity of the Patos Lagoon estuary,
with marshes, shoals ( <1.5 m), deeper open waters (1.5-5 m) and channels
(>6 m), provide for extensive and diverse habitats (Fig. 12.1). Many of the
marine invertebrates and fishes in the southwestern Atlantic depend on
estuarine habitats as nurseries during part of their life cycle while others,
like marine mammals and birds, find feeding, roosting and breeding
grounds in the estuary.
12.3.1 The Water Column
The meteorologic processes which control seawater intrusion are also responsible for the transport of phyto- and zooplankton and the eggs and
larvae of fish into the estuary, thus marked seasonal and annual changes in
the estuarine planktonic community composition are common. Organisms which are constant and often abundant components of the plankton
community are typically represented by phytoplanktonic nanoflagellates
( <20 J.tM), the copepod Acartia tonsa, and eggs and larvae of Atherinidae
( Odonthestes argentinensis, Atherinella brasiliensis), Soleidae (Achirus
garmanii), Ariidae ( Genidens genidens), Jenynsiidae, Blenniidae, Gobiidae,
and Gobiesocidae. During intense runoff in winter, oligohaline diatoms
(Skeletonema subsalsum 10 6 cells 1- 1 ), cladocerans, freshwater copepods,
and eggs and larvae of some limnic fish (i.e., Parapimelodus valencienis)
are introduced into the estuary and may become an important part of the
plankton community. In contrast, after periods of seawater intrusion,
euryhaline diatoms (Skeletonema costatum, Cerataulina daemon), marine
copepods, and larvae of polychaetes, mollusks, and crustaceans become
the dominant components of an increasingly diverse plankton community.
Elevated water temperatures and extended periods of saltwater intrusion
during summer introduce neritic marine cladocerans (i.e., ctenophores,
siphonophores, medusae, chaetognats ), coastal mysids, dinoflagellates, and
large numbers ( 10 5 cells 1-') of marine diatoms ( Chaetoceros, Rhizosolenia,
Coscinodiscus, Odontella), which leads to high plankton community diversity in the estuary (Montu et al. 1997; Odebrecht and Abreu 1997). Intense
spawning activities of many coastal and oceanic fish species in warm
169
ments by inflowing seawater and strong winds (Niencheski and Baumgarten 1997).
12.3 Estuarine Habitats
The size and the physiographic heterogeneity of the Patos Lagoon estuary,
with marshes, shoals ( <1.5 m), deeper open waters (1.5-5 m) and channels
(>6 m), provide for extensive and diverse habitats (Fig. 12.1). Many of the
marine invertebrates and fishes in the southwestern Atlantic depend on
estuarine habitats as nurseries during part of their life cycle while others,
like marine mammals and birds, find feeding, roosting and breeding
grounds in the estuary.
12.3.1 The Water Column
The meteorologic processes which control seawater intrusion are also responsible for the transport of phyto- and zooplankton and the eggs and
larvae of fish into the estuary, thus marked seasonal and annual changes in
the estuarine planktonic community composition are common. Organisms which are constant and often abundant components of the plankton
community are typically represented by phytoplanktonic nanoflagellates
( <20 J.tM), the copepod Acartia tonsa, and eggs and larvae of Atherinidae
( Odonthestes argentinensis, Atherinella brasiliensis), Soleidae (Achirus
garmanii), Ariidae ( Genidens genidens), Jenynsiidae, Blenniidae, Gobiidae,
and Gobiesocidae. During intense runoff in winter, oligohaline diatoms
(Skeletonema subsalsum 10 6 cells 1- 1 ), cladocerans, freshwater copepods,
and eggs and larvae of some limnic fish (i.e., Parapimelodus valencienis)
are introduced into the estuary and may become an important part of the
plankton community. In contrast, after periods of seawater intrusion,
euryhaline diatoms (Skeletonema costatum, Cerataulina daemon), marine
copepods, and larvae of polychaetes, mollusks, and crustaceans become
the dominant components of an increasingly diverse plankton community.
Elevated water temperatures and extended periods of saltwater intrusion
during summer introduce neritic marine cladocerans (i.e., ctenophores,
siphonophores, medusae, chaetognats ), coastal mysids, dinoflagellates, and
large numbers ( 10 5 cells 1-') of marine diatoms ( Chaetoceros, Rhizosolenia,
Coscinodiscus, Odontella), which leads to high plankton community diversity in the estuary (Montu et al. 1997; Odebrecht and Abreu 1997). Intense
spawning activities of many coastal and oceanic fish species in warm