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On a regional scale, the Western Atlantic coast bordering South America encompasses a variety of estuaries that result from drainage basins crossing from tropical
to temperate climates, and debouch into coastal and marine regions subject to different oceanographic forcing (Blaber and Barletta 2016). In most of these systems,
the major annual water quality shifts result from seaward river flow during the rainy
season and upstream coastal water inflow during the dry season (Barletta et al. 2005,
2008, 2010; Lima et al. 2015). River flow, and the extent of its influence over the
estuarine system, is proportional to rainfall patterns and human intervention aiming
at the use and control of water resources, such as damming and hydropower stations
(Almodóvar and Nicola 1999; Morita and Yamamoto 2002). Although rainfall patterns changes among estuaries, environmental variability responds to a combination
of factors that include riverine and estuarine basin geomorphology, microclimates
and habitat modification. Thus, the main channel of estuaries are a composition of
heterogeneous, temporary, habitats which differ among themselves in abiotic characteristics (mainly water salinity) varying from freshwater to marine water, known
as estuarine ecocline (Barletta and Blaber 2007; Barletta and Dantas 2016).
When rainfall and river flow increase, pollutant loads move together with shifting abiotic habitats to other estuarine areas downstream. Although somewhat
diluted, pollutants become bioavailable for a greater diversity of organisms over the
whole ecocline. Abrupt changes in climatic patterns or in the river flow regime
(dredging operations) will induce changes in the estuarine ecocline and fish communities will respond to these changes by modifying assemblage structures (Barletta
et al. 2016; Prestrelo and Monteiro-Neto 2016). However, despite all impacts suffered for these systems, climate and hydrodynamics contribute to reduce pollution,
especially during the rainy season, through biodilution and transport of contaminants out of the system to adjacent coastal waters, in a process known as environmental homeostasis (Elliott and Quintino 2007; Barletta et al. 2016).
Studies regarding estuarine ecocline have increased in term of quality and quantity aiming to provide consistent recommendations for conservational issues
(Barletta et al. 2005, 2008; Barletta and Blaber 2007; Storm et al. 2005; Prestrelo
and Monteiro-Neto 2016; Slater 2016). However, efforts of governmental agencies
for conservation, recovery and sustainable use of estuaries are almost always implemented regardless of basic concepts of estuarine variability and the influences of
human interventions, leading to poor management practices (Elliot and Whitefield
2011; Dauvin and Ruellet 2009; Barletta et al. 2010; Machado-Allison 2016).
Three important and well-studied examples exist of estuaries that represent the
different stages of the latitudinal gradient along the western Atlantic, from the
Equator to subtropical climates. The Caeté Estuary (0°45′–1°07′S; 46°25′–
46°50′W), the Goiana Estuary (7°32′–7°35′S; 34°50′–34°58′W) and the Paranaguá
Estuarine Complex (25°15′–25°35′S; 48°20′–48°45′W) are systems where the fish
fauna were year-round characterized along their ecocline, and from where information to support managerial decision is ready to be used. These three systems represent the humid tropics, the dry tropics and the warm temperate, respectively.
Different policies for the conservation of coastal ecosystems and traditional populations in the Amazon, northeast and southern Brazilian wetlands still exist (Barletta
16 Estuarine Ecoclines and the Associated Fauna: Ecological Information as the Basis…
On a regional scale, the Western Atlantic coast bordering South America encompasses a variety of estuaries that result from drainage basins crossing from tropical
to temperate climates, and debouch into coastal and marine regions subject to different oceanographic forcing (Blaber and Barletta 2016). In most of these systems,
the major annual water quality shifts result from seaward river flow during the rainy
season and upstream coastal water inflow during the dry season (Barletta et al. 2005,
2008, 2010; Lima et al. 2015). River flow, and the extent of its influence over the
estuarine system, is proportional to rainfall patterns and human intervention aiming
at the use and control of water resources, such as damming and hydropower stations
(Almodóvar and Nicola 1999; Morita and Yamamoto 2002). Although rainfall patterns changes among estuaries, environmental variability responds to a combination
of factors that include riverine and estuarine basin geomorphology, microclimates
and habitat modification. Thus, the main channel of estuaries are a composition of
heterogeneous, temporary, habitats which differ among themselves in abiotic characteristics (mainly water salinity) varying from freshwater to marine water, known
as estuarine ecocline (Barletta and Blaber 2007; Barletta and Dantas 2016).
When rainfall and river flow increase, pollutant loads move together with shifting abiotic habitats to other estuarine areas downstream. Although somewhat
diluted, pollutants become bioavailable for a greater diversity of organisms over the
whole ecocline. Abrupt changes in climatic patterns or in the river flow regime
(dredging operations) will induce changes in the estuarine ecocline and fish communities will respond to these changes by modifying assemblage structures (Barletta
et al. 2016; Prestrelo and Monteiro-Neto 2016). However, despite all impacts suffered for these systems, climate and hydrodynamics contribute to reduce pollution,
especially during the rainy season, through biodilution and transport of contaminants out of the system to adjacent coastal waters, in a process known as environmental homeostasis (Elliott and Quintino 2007; Barletta et al. 2016).
Studies regarding estuarine ecocline have increased in term of quality and quantity aiming to provide consistent recommendations for conservational issues
(Barletta et al. 2005, 2008; Barletta and Blaber 2007; Storm et al. 2005; Prestrelo
and Monteiro-Neto 2016; Slater 2016). However, efforts of governmental agencies
for conservation, recovery and sustainable use of estuaries are almost always implemented regardless of basic concepts of estuarine variability and the influences of
human interventions, leading to poor management practices (Elliot and Whitefield
2011; Dauvin and Ruellet 2009; Barletta et al. 2010; Machado-Allison 2016).
Three important and well-studied examples exist of estuaries that represent the
different stages of the latitudinal gradient along the western Atlantic, from the
Equator to subtropical climates. The Caeté Estuary (0°45′–1°07′S; 46°25′–
46°50′W), the Goiana Estuary (7°32′–7°35′S; 34°50′–34°58′W) and the Paranaguá
Estuarine Complex (25°15′–25°35′S; 48°20′–48°45′W) are systems where the fish
fauna were year-round characterized along their ecocline, and from where information to support managerial decision is ready to be used. These three systems represent the humid tropics, the dry tropics and the warm temperate, respectively.
Different policies for the conservation of coastal ecosystems and traditional populations in the Amazon, northeast and southern Brazilian wetlands still exist (Barletta
16 Estuarine Ecoclines and the Associated Fauna: Ecological Information as the Basis…