**3.2 Abiotic variable**

Conductivity (mS.cm<sup>−</sup><sup>1</sup> ), salinity, pH, water temperature (°C), dissolved oxygen—DO (mg.L<sup>−</sup><sup>1</sup> ), and oxidation-reduction potential—ORP (mg.L<sup>−</sup><sup>1</sup> ) were

**193**

(mg.L<sup>−</sup><sup>1</sup>

**Figure 6.**

*Sampling station: South.*

**Figure 5.**

**Figure 4.**

*Sampling station: North.*

*Sampling station: Center.*

system of Vollenweider [54].

*Subtropical Coastal Lagoon from Southern Brazil: Environmental Conditions and Phytobenthic…*

measured with a HORIBA U52 probe. Depth and water transparency (cm) were measured with a Secchi disk. Precipitation, wind velocity, and wind direction data

Laboratory analyses were performed as follows: total phosphorus—TP (mg.L<sup>−</sup><sup>1</sup>

) with the silicomolybdate method [52]. The classification of salinity was

)

), accord-

were obtained from the National Institute of Meteorology—INMET.

by absorptiometry reduction of ascorbic acid, total nitrogen—TN (mg.L<sup>−</sup><sup>1</sup>

ing to the Kjeldahl method (NBR 10560-1988, 13796-1997), and total silicate

based on the Venice System [53]. Trophic level was determined by the modified

*DOI: http://dx.doi.org/10.5772/intechopen.87776*

*Subtropical Coastal Lagoon from Southern Brazil: Environmental Conditions and Phytobenthic… DOI: http://dx.doi.org/10.5772/intechopen.87776*

**Figure 4.** *Sampling station: North.*

*Lagoon Environments Around the World - A Scientific Perspective*

*Aerial view of the Peixe Lagoon channel. Source: Lagoa do Peixe National Park (PNLP).*

The study was based on samples collected at three sampling stations in the lagoon. North (**Figure 4**) is close to a narrow channel that interconnects the northernmost sealed bodies with a central portion of the lagoon; Center (**Figure 5**) is next to the channel that connects to the ocean; and South (**Figure 6**) is at the south end of the lagoon. Sampling occurred in the four seasons, fall (June 2011), winter (August 2011), spring (November 2011), and summer (February 2012). During the first sampling, in the fall, the channel was closed. It was open days before winter sampling and remained open for the remainder of the sampling period. For the diatoms analysis, sediment samples were collected at depths of 2 cm with a spatula, at the

*Total precipitation (mm) and average monthly temperature (°C) recorded by the meteorological station of* 

*Mostardas/RS. Source: National Institute of Meteorology (INMET).*

lagoon margin, and packed in glass pods for transport to the laboratory.

), salinity, pH, water temperature (°C), dissolved

) were

), and oxidation-reduction potential—ORP (mg.L<sup>−</sup><sup>1</sup>

**192**

**Figure 2.**

**3. Methods**

**Figure 3.**

**3.1 Sampling**

**3.2 Abiotic variable**

oxygen—DO (mg.L<sup>−</sup><sup>1</sup>

Conductivity (mS.cm<sup>−</sup><sup>1</sup>

**Figure 5.** *Sampling station: Center.*

**Figure 6.** *Sampling station: South.*

measured with a HORIBA U52 probe. Depth and water transparency (cm) were measured with a Secchi disk. Precipitation, wind velocity, and wind direction data were obtained from the National Institute of Meteorology—INMET.

Laboratory analyses were performed as follows: total phosphorus—TP (mg.L<sup>−</sup><sup>1</sup> ) by absorptiometry reduction of ascorbic acid, total nitrogen—TN (mg.L<sup>−</sup><sup>1</sup> ), according to the Kjeldahl method (NBR 10560-1988, 13796-1997), and total silicate (mg.L<sup>−</sup><sup>1</sup> ) with the silicomolybdate method [52]. The classification of salinity was based on the Venice System [53]. Trophic level was determined by the modified system of Vollenweider [54].
