Environmental and Sanitary Conditions of Guanabara Bay, Rio de Janeiro

Abstract

Guanabara Bay is the second largest bay in the coast of Brazil, with an area of 384 km(2). In its surroundings live circa 16 million inhabitants, out of which 6 million live in Rio de Janeiro city, one of the largest cities of the country, and the host of the 2016 Olympic Games. Anthropogenic interference in Guanabara Bay area started early in the XVI century, but environmental impacts escalated from 1930, when this region underwent an industrialization process. Herein we present an overview of the current environmental and sanitary conditions of Guanabara Bay, a consequence of all these decades of impacts. We will focus on microbial communities, how they may affect higher trophic levels of the aquatic community and also human health. The anthropogenic impacts in the bay are flagged by heavy eutrophication and by the emergence of pathogenic microorganisms that are either carried by domestic and/or hospital waste (e.g., virus, KPC-producing bacteria, and fecal coliforms), or that proliferate in such conditions (e.g., vibrios). Antibiotic resistance genes are commonly found in metagenomes of Guanabara Bay planktonic microorganisms. Furthermore, eutrophication results in recurrent algal blooms, with signs of a shift toward flagellated, mixotrophic groups, including several potentially harmful species. A recent large-scale fish kill episode, and a long trend decrease in fish stocks also reflects the bay's degraded water quality. Although pollution of Guanabara Bay is not a recent problem, the hosting of the 2016 Olympic Games propelled the government to launch a series of plans to restore the bay's water quality. If all plans are fully implemented, the restoration of Guanabara Bay and its shores may be one of the best legacies of the Olympic Games in Rio de Janeiro.

Keywords: Guanabara Bay; anthropogenic impacts; bacteria; microalgae; pollution; sanitary conditions.

FIGURE 1

Composition of pictures showing degraded (a,b) and non-degraded areas of Guanabara Bay (f), which still have some fringing mangrove system. There are different urban landscapes surrounding the bay, such as industries (a), slums (b), metropolis (c,d). The bay has social-economic importance and it is used, among others, as harbor (e), for artisanal fisheries (f), and recreational purposes (d). Pictures by: (a) and (c): Michelle Vils; (d): Wanderson F. de Carvalho; (b, e) and (f): Giovana O. Fistarol.

FIGURE 2

Location of Guanabara Bay, Southeastern Brazil. The cities around the bay and the rivers that form the bay’s drainage area are shown, as well as the location of sewage wastewater treatment plants (WWTPs) (WWTP location obtained from Comitê de Bacia da Baía de Guanabara, SIG-RHGB, http://www.comitebaiadeguanabara.org.br/sig-rhbg/).

FIGURE 3

Map of Guanabara Bay showing different parameters that indicate water quality throughout the sampling points (A–D) cited in the text. Sites where resistant bacteria were found are marked with a star (★), according to Coutinho et al. (2014). The bay was divided in sections (1–5, dashed lines) of various water quality levels (according to Mayr et al., 1989): section 1. better water quality conditions; section 2. areas with high circulation, but subjected to high organic load; section 3. deteriorated areas under strong influence of urban and industrial contaminants; section 4. areas under the influence of less polluted rivers and that still maintain a fringe of mangrove; section 5. the most deteriorated areas with low circulation and high input of contaminants. Water quality zones show a good correspondence with chlorophyll a (Chla) concentrations recorded in the literature (Mayr et al., 1989; Paranhos et al., 1998; Paranhos et al., 2001; Santos et al., 2007) which are shown here by different colors.

FIGURE 4

Relative abundance of phylogenetic groups to metagenomes (at class level) in three sites of Guanabara Bay (modified from Gregoracci et al., 2012). Location of sites are shown on Figure 3.

FIGURE 5

Scatterplot showing the correlation between the abundance of vibrios (CFU ml^-1) and concentrations of total nitrogen (log10 μM) (A), which had a correlation of R² = 0.59, and total phosphorus (log10 μM) (B), which had a correlation of R² = 0.62, for three sites of Guanabara Bay across a 6-years’ time-series (adapted from Gregoracci et al., 2012). For site location see Figure 3. Besides the correlation between vibrio abundance and nutrient concentration, the figure shows a clear separation between the less impacted sites “A” and “under Rio-Niteroi Bridge”, and the more impacted site “B”.

FIGURE 6

Flowchart showing the three programs in which the Sanitation Pact, enacted by the state of Rio de Janeiro, is divided in. From these three programs, the Clean Guanabara Plan (PGL) will tackle the pollution problems of Guanabara Bay, and it is divided in eight actions shown in the chart.