**3. Case study: São Sebastião Channel, SE coast of Brazil**

Deciphering the impacts of domestic and industrial pollutants is difficult because they often occur together in sheltered coastal environments (bays or estuaries). When they occur separately, it is often in environments with different natural conditions, which makes comparison problematic. São Sebastião Channel (SSC) is an open area where industrial and domestic effluents are separately disposed, but under similar natural conditions, offering the opportunity to compare their impact on benthic biota [53].

SSC, located between the latitudes 23°40′S and 23°53.5′S and the longitudes 45°19′ and 45°30′W, is a 25 km stretch, which separates the continent from São Sebastião island (**Figure 2**). SSC width ranges from 2 km in its central portion and 7 km in its southern and northern ends. Its axis, where the largest depths (30–50 m) are found, is located closer to the island, due to the erosion and/or structural conditioning of the bottom. The smaller depths (6 m) occur on the continental side of the channel. The southern and northern ends have depths of 25 and 20 m, respectively (**Figure 2**).

 The water circulation in the channel is characterized by alternate northerly and southerly movements, with a periodicity of days that is not directly influenced by tidal currents [54]. Geometry and topography of the channel bottom produce more intense longitudinal currents on the insular side, with speeds of up to 1.0 m s <sup>−</sup><sup>1</sup> toward the north and 0.7 m s<sup>−</sup><sup>1</sup> toward the south.

In SSC, there are some areas where the anthropic influence is quite intensified. Among these, the central region of the channel has the largest petroliferous terminals of South America, "Dutos e Terminais Centro Sul" (DTCS) of PETROBRAS. According to Duleba et al. [53], the DTCS generates two types of

**Figure 2.**  *Study areas and sampling grid in São Sebastião Channel (SE coast of Brazil).* 

liquid effluents. The first type consists mostly of water, separated from oil by density during transportation from drilling platforms in the oil tankers; the second type consists of rainwater and industrial water from the DTCS, contaminated by oil. These waters are treated in the wastewater treatment plants (ETE—Estação de Tratamento de Efluentes), where they are first separated from residual oil by adding a solution of polyelectrolyte [55]. Then, a series of treatments, using hydrogen peroxide at several pH levels, allows the oxidization of sulfides and phenol before an ultimate neutralization of the effluent. Approximately 15,000 m3 of produced waters are treated every month. According to Fortis et al. [55], contaminated rainwater and industrial water are treated in systems that use mostly decantation to separate oil from water (SAO = Separação de Águas Oleosas). In addition, if the quality of the

*Response of Benthic Foraminifera to Environmental Variability: Importance of Benthic… DOI: http://dx.doi.org/10.5772/intechopen.81658* 

outflowing water does not satisfy the legal regulations, it is sent for treatment in the ETE. After treatment, effluents from both the ETE and SAO are mixed before being discharged through two submarine pipelines (with 1600 and 1400 m long), which end in diffusers, located at a depth ranging from 20 to 25 m [55].

The oil separation techniques, used in the wastewater treatment plants, primarily remove particulate matter and dispersed oil, while dissolved hydrocarbons remain in the discharged water [55]. The treated water is generally enriched with ammonia [55] and dissolved ions of sodium, potassium, magnesium, chloride, and sulfate, leading to salinity levels of up to 52.8 [55]. The treated water also has elevated levels of some heavy metals, as well as corrosion and scale inhibitors, biocides, dispersants, emulsion breakers, and other chemicals [56].

Close to DTCS, there is the submarine outfall of Araçá, which transports almost all the domestic effluents from the São Sebastião city. That emissary has a total length of 1061 m and a diameter of 400 mm. Its diffuser has a length 10.1 m and is located at Araçá point, at a depth of 8 m. The discharge speed per final discharge is 91.46 l s<sup>−</sup><sup>1</sup> [46].

#### **3.1 Methods applied in São Sebastião Channel**

Sediment samples from DTCS (named TB) were collected near the outfall diffusers in September 2005, by the Environmental Agency of the São Paulo State, Brazil (CETESB—"Companhia Ambiental do Estado de São Paulo"). This authority evaluates the adequacy of the wastewater plants projects, the definition of environmental monitoring programs, and the regulation and enforcement of the water quality compliance. The sampling grid, consisting of 10 sampling points, was located in an area of 125,000 m<sup>2</sup> surrounding the diffusers. In addition, samples from 10 stations along the São Sebastião Channel (SSC) and 10 stations around the Araçá (AR) domestic sewage outfall were used for comparison. The geographical positions of the sampling stations were determined using the global positioning system (GPS), with the UTM datum SAT 69.

Surface sediment samples were collected for the following analyses: (i) grain size analyses; (ii) geochemical analyses; and (iii) determination of living benthic foraminifera. Textural, trace elements, and foraminifera data from TB, AR, and SSC areas were previously studied by Teodoro et al. [46, 53], which described in detail the methods of sedimentological and geochemical analysis.

 Concerning the foraminiferal study, immediately after sampling, the samples were fixed with 70% alcohol stained with 1 g Rose Bengal, to distinguish stained (living) from unstained (dead) benthic foraminifera [57]. Aliquots of 10 cm3 of sediment were washed through two sieves: 0.5 and 0.063 mm. The obtained fractions were dried, and the foraminifera were separated from the sediment by flotation using trichloroethylene. In samples with a low number of foraminifera, aliquots of 10 cm3 were successively analyzed for to count of at least 100 stained individuals [33, 58]. Therefore, about 100 or more stained foraminifera were handpicked for identification and counting at each station. Foraminiferal density 1 (density 1) is expressed as the number of foraminifera per volume of sediment and density 2 is number of foraminifera per 10 cm3 [59]. Foraminiferal assemblages structure was analyzed by using the Shannon index (H′) [34], the equitability (J′), calculated according to the Pielou index [35], and the species richness, calculated from density 1.

Canonical correspondence analysis (CCA) was used to investigate the relationship between foraminifera and sedimentological variables of the three areas: TEBAR, Araçá, and São Sebastião Channel (see details in [53]). The Monte Carlo permutation test (999 permutations) was used to assess the statistical significance of the correlations (at *p* < 0.05 and *p* < 0.01).

### **3.2 Results obtained in São Sebastião Channel**

### *3.2.1 São Sebastião Channel*

 A total of 88 living species were identified in the São Sebastião Channel [53] belonging to the suborders of Rotaliina (63 species), Textulariina (20 species), and Miliolina (only one species). The volume of analyzed sediment needed to obtain at least 95 stained foraminifers ranged from 10 to 60 cm3 . Density 1 values ranged from 95 specimens per 60 cm3 of sediment to 296 specimens per 10 cm3 of sediment. Density 2 values ranged from 16 to 296 specimens per 10 cm3 of sediment. The highest densities were identified at stations SSC3 (266 specimens) and SSC6 (296 specimens). Richness values varied from 12 to 33 species. The H′ and J′ values varied between 1.59 and 3.25 and between 0.64 and 0.93, respectively.

*Ammonia tepida* was the most abundant species in almost all samples (5–56.1%). The following species presented significant relative abundance: *Ammonia parkinsoniana* (2–19.6%), *Bolivina striatula* (0.8–11.6%), *Globocassidulina crassa* (<18.8%), *Globocassidulina subglobosa* (<10.2%), *Nonionella opima* (<9.1%), *Buliminella elegantissima* (2–8.5%), *Bolivina fragilis* (<8.5%), *Bulimina marginata* (<5.9%), *Pseudononion japonicum* (<5.8%), *Hopkinsina pacifica* (<5.3%), *Rosalina floridensis*  (<6.1%), *Gavelinolepsis praegeri* (<5.5%), and *Hanzawaia boueana* (<5.1%). At the reference station (SSC3), *A. tepida* had the highest relative abundance (42.5%), followed by *A. parkinsoniana* (16.2%), *B. striatula* (7.9%), and *B. elegantissima* (7.5%). At this station, 32 species were recognized.

#### *3.2.2 Dutos e Terminais Centro Sul (DTCS)*

Throughout this area, 45 species were identified as belonging to Rotaliina (37 species), Textulariina (6 species), and Miliolina (2 species). Foraminiferal densities ranged from 0.5 (TB9) to 25 (TB7) specimens per 10 cm3 of sediment. Owing to this low density, the volume of analyzed sediment needed to obtain 95 stained individuals varied from 40 to 190 cm3 . Species richness varied from 12 to 23 per 95 foraminifera. The H′ and J' values ranged from 1.5 to 2.4 and from 0.56 to 0.71, respectively. Both indices presented low values, indicating low species diversity, due to the dominance of few species.

*Ammonia tepida* was the most abundant species in all the samples (38.5–66%). The following species also had significant relative abundance: *Pararotalia cananeiaensis* (<20%), *B. elegantissima* (0.9–11.8%), *A. parkinsoniana* (<7.3%), *C. lobatulus*  (<6.6%), *B. striatula* (<6.4%), *B. marginata* (1–6.3%), *B. ordinaria* (0.9–6%), *Bolivina compacta* (<5.5%), and *Rosalina floridensis* (<5%).

#### *3.2.3 Araçá Outfall*

 In this area, 51 species [53] were identified as belonging to the suborders Rotaliina (33 species), Textulariina (11 species), and Miliolina (7 species). Foraminiferal densities ranged from 28 to 98 specimens per 10 cm3 of sediment. A volume ranging from 10 to 40 cm3 was analyzed to obtain 95 stained individuals. Species richness values varied from 13 to 28 species. The H′ and J' values varied from 0.70 to 2.64 and from 0.69 to 0.85, respectively.

*Ammonia tepida* was the most abundant species in all samples of the Araçá region, with a relative abundance ranging between 24.7 and 47.3%. The following species also had significant relative abundance: *P. cananeiaensis* (1.8–17%), *C. lobatulus* (<11.9%), *B. ordinaria* (1.1–11.3%), *R. floridensis* (<8.6%), *B. elegantissima* (<7.8%), *B. striatula*  (3.2–7.7%), *P. japonicum* (<6.1%), *G. crassa* (<6.1%), and *A. parkinsoniana* (<5.4%).

*Response of Benthic Foraminifera to Environmental Variability: Importance of Benthic… DOI: http://dx.doi.org/10.5772/intechopen.81658* 

### **3.3 Discussion of the results obtained in São Sebastião Channel**

 Sediments in the DTCS area were silty with high concentrations of total organic carbon (1.7–2.4%), total nitrogen (0.2–0.3%), total sulfur (0.4–0.6%), and total phosphorous (0.12–0.18%) and inorganic phosphorous (0.07–0.11%). These values were higher than those in sediments collected in the SSC and Araçá regions. The sediments' concentrations of As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn in the SSC and AR regions were lower than their corresponding probable effect levels (PELs) [53]. However, sediments near the DTCS were enriched with As, Cu, and Ni, whose concentrations exceeded their corresponding threshold effect levels (TELs).

Despite potentially considerable pollution sources, mostly around DTCS, the contamination of sediment, as measured through geochemical analyses, is moderate. This probably results from the dispersion of effluents by the currents that affect the São Sebastião Channel. However, even if they are dispersed and do not accumulate within the sediment, pollutant may affect the benthos since all habitats exposed to all types of contaminants experience decreased biodiversity [60]. Indeed, the low densities of foraminifera around the DTCS diffusers illustrate the impact of environmental stress on the benthos.

 In the DTCS area, it was necessary to search 50–190 cm3 of sediment to find 100 living specimens (an average of 9 ± 6 individuals per 10 cm3 of sediment) [53]. In the SSC and Araçá areas, a maximum of 40 cm3 of sediment was enough to locate 100 living specimens (an average density of 62 ± 22 foraminifera per 10 cm3 of sediment).

Organic matter may favor microfauna [7], or it may be responsible for decreasing microfauna density and richness [10, 15]. The toxic threshold depends on the nature of the organic matter and its concentration in the sediments [10]. The degradation of organic matter requires large quantities of oxygen; thus, when the flux of organic matter exceeds the degradation rate, a benthic hypoxia or even anoxia can occur. In this sense, the microfauna is compelled to change: stenobiotics can disappear and an abundance of tolerant species may be observed [10, 15, 31].

 *Pararotalia cananeiaensis* is an herbivorous, epifaunal species characteristic of a marine environment. It is abundant in dead assemblages all over the SSC. The positive correlation of *P. cananeiaensis*, together with *D. floridana*, with TP and Cd appears to be an indication that they are tolerant to these elements and to the associated contaminants. However, the ecological preference of *P. cananeiaensis* is not yet well known in Brazil (Debenay et al., 2001c)\*\*\*. Near the Araçá domestic submarine outfall, Teodoro et al. [46] reported *P. cananeiaensis* living preferentially at stations with high sulfur content (r = 0.86; *p* < 0.001), particulate organic matter (r = 0.62; *p* < 0.001), and silt (r = 0.75; *p* < 0.01). In the present study, no relationship between abiotic parameters and relative abundance of *P. cananeiaensis* was recorded.

The species related to reducing muddy sediment, with a moderate concentration in Cr and a noticeable content of organic matter, were *B. marginata*, *B. elegantissima*, *B. compacta*, *A. tepida*, and *A. parkinsoniana*. Most of these species are recognized in the literature as tolerant to high organic matter flux and as able to survive in low oxic conditions. Such is the case of *B. marginata* [61] and *B. elegantissima* [14]. Bandy et al. [62] noted that *B. elegantissima* and *B. marginata* tend to be abundant in areas affected by pollutants. In this study, the highest abundance of bolivinids and buliminids was observed in stations positioned in the central part of the channel: stations SSC7, SSC8, and SSC9.

*Ammonia tepida* is a eurybiotic species characteristic of near-shore areas and paralic environments [63]. The tolerance of *A. tepida* to adverse conditions, including organic and chemical pollution, has long been reported in both field studies and culture studies [10]. Its potential application for pollution monitoring is well established. It reached the highest relative abundance in DTCS the polluted samples and, to a lesser extent, in Araçá. This higher proportion of *A. tepida* is due to a decline of stenobiotic species. The higher abundance of tolerant species in these areas indicates that the benthos is significantly impacted by both organic (Araçá) and chemical (DTCS) pollution and suffers with a greater impact of chemical pollution.
