Chapter 4
Nutrients and Suspended Matter Behaviour in the
Patos Lagoon Estuary (Brazil)
Luis Felipe Niencheski . Maria da Gra<;:a Baumgarten
Gilberto Fillmann . Herbert L. Windom
4.1
Introduction
Estuaries are distinctive environments where continental runoff interacts with sea
water. They are characterized by complex and usually strong circulation and this, along
with the typically shallow depths of estuarine systems, leads to intense sediment-water interactions. Estuaries are generally also biologically productive.
Because human populations are concentrated in coastal regions, characteristics of
estuaries can be influenced by man leading to changes in processes that occur there.
A major impact of human activity is the release of contaminants and nutrients, the
ultimate concentrations of which are controlled by the mixing of freshwater and seawater and by exchange between different components of the estuarine system (e.g.,
sediments, water column, biota).
Estuarine water quality is the result of an interplay of factors including material
inputs, water movement and in situ biological and chemical processes. The changing
chemical and physical conditions encountered in estuaries, along the salinity gradient (Le., from freshwater to saltwater), may lead to changes in the solubility of substances resulting in either their removal from solution onto particles or their leaching from particles into solution. Chemical precipitation of substances may lead to the
formation of particles which are preferentially removed from the water column during transport through estuarine systems, and biological processes may result in the
exchange of materials, particularly nutrients, from particulate to dissolved form and
vice versa.
The aim of this study was to describe basic chemical conditions of the estuary of
the Patos-Mirim Lagoon system. The study is based on several cruises made during
different environmental conditions, and involved the measurement of salinity, dissolved oxygen, suspended matter and nutrients. The main focus of the study was on
the input of these substances to the estuarine system and processes affecting their
behaviour.
The Patos Lagoon (10 360 km2) and Mirim Lagoon (3749 km2) are located about
2000 km South of Rio de Janeiro and form the largest lagoonal system of South
America (Fig. 4.1). The communication between these lagoons is through the 70 km
long Sao Gon<;:alo Channel. The watershed emptying into these lagoons is about
201 626 km>, of which 75% belongs to the Patos Lagoon. The only contact with the sea
is through an inlet at the southern end of Patos Lagoon. Both lagoons are shallow
(average deep about 6 m). Geomorphologically the southern region of the Patos Lagoon has the characteristics of a bar-built estuary with a 30 km wide upper limnic
part which gradually, over 50 km, narrows into a 700 m wide access channel. All along
Nutrients and Suspended Matter Behaviour in the
Patos Lagoon Estuary (Brazil)
Luis Felipe Niencheski . Maria da Gra<;:a Baumgarten
Gilberto Fillmann . Herbert L. Windom
4.1
Introduction
Estuaries are distinctive environments where continental runoff interacts with sea
water. They are characterized by complex and usually strong circulation and this, along
with the typically shallow depths of estuarine systems, leads to intense sediment-water interactions. Estuaries are generally also biologically productive.
Because human populations are concentrated in coastal regions, characteristics of
estuaries can be influenced by man leading to changes in processes that occur there.
A major impact of human activity is the release of contaminants and nutrients, the
ultimate concentrations of which are controlled by the mixing of freshwater and seawater and by exchange between different components of the estuarine system (e.g.,
sediments, water column, biota).
Estuarine water quality is the result of an interplay of factors including material
inputs, water movement and in situ biological and chemical processes. The changing
chemical and physical conditions encountered in estuaries, along the salinity gradient (Le., from freshwater to saltwater), may lead to changes in the solubility of substances resulting in either their removal from solution onto particles or their leaching from particles into solution. Chemical precipitation of substances may lead to the
formation of particles which are preferentially removed from the water column during transport through estuarine systems, and biological processes may result in the
exchange of materials, particularly nutrients, from particulate to dissolved form and
vice versa.
The aim of this study was to describe basic chemical conditions of the estuary of
the Patos-Mirim Lagoon system. The study is based on several cruises made during
different environmental conditions, and involved the measurement of salinity, dissolved oxygen, suspended matter and nutrients. The main focus of the study was on
the input of these substances to the estuarine system and processes affecting their
behaviour.
The Patos Lagoon (10 360 km2) and Mirim Lagoon (3749 km2) are located about
2000 km South of Rio de Janeiro and form the largest lagoonal system of South
America (Fig. 4.1). The communication between these lagoons is through the 70 km
long Sao Gon<;:alo Channel. The watershed emptying into these lagoons is about
201 626 km>, of which 75% belongs to the Patos Lagoon. The only contact with the sea
is through an inlet at the southern end of Patos Lagoon. Both lagoons are shallow
(average deep about 6 m). Geomorphologically the southern region of the Patos Lagoon has the characteristics of a bar-built estuary with a 30 km wide upper limnic
part which gradually, over 50 km, narrows into a 700 m wide access channel. All along