guia do novo coronavirus
Imprimir Republish

Ecology

In the mud and sand of Araçá

Despite the loss of mangrove stands in recent years, this bay on the northern coast of São Paulo State displays a great deal of biodiversity

The beach exposed: at low tide, the bay is transformed into a muddy bog. In the distance, the port of São Sebastião

Eduardo CesarThe beach exposed: at low tide, the bay is transformed into a muddy bog. In the distance, the port of São SebastiãoEduardo Cesar

in São Sebastião, SP

When the tide is low, Araçá Bay is transformed. The water recedes and the sandy, pebble-strewn beach turns into a muddy bog hundreds of meters long. Ahead, one can see the ships entering and leaving the Port of São Sebastião, to one side, and fishing boats near the mouth of the bay, which is framed by forests, houses and high rock walls. This 500,000-square-meter inlet in the city of São Sebastião on the northern coast of the state of São Paulo has revealed a surprising diversity of life forms, some of which are sustained by the polluted discharge from household and port sewerage systems.

The debris carried into the bay from the Mãe Isabel creek appear to benefit some animal groups, such as the marine worms Heteromastus filiformis and Laeonereis culveri, and the microcrustacean Monokalliapseudes schubarti. But they can be harmful to other groups that are ecologically important or endangered, such as the marine worm species Eunice sebastiani and Diopatra cuprea—which look like bristly earthworms. Since 2012, the 170 researchers led by Cecília Amaral, a biologist with the Institute of Biology at the University of Campinas (Unicamp), have been investigating the physical, chemical, geological and socioeconomic factors that influence the dynamics of Araçá. Their biodiversity inventory of the bay has enabled them to identify 1,368 species or organisms.

058-061_Baia do Araça_234 novoneldsonMost of these creatures are benthos, a group of organisms that live along rocky coasts, in mangrove stands and among grains of sand. A total of 56 species were found for the first time, including Jebramella angusta, a transparent worm with whitish tentacles that lives on rocks or in shell fragments. On the basis of the research conducted in this bay in 1950, Amaral regards Araçá as one of the most biodiverse coastal regions in Brazil. Much of the data compiled from the project she heads is presented in the book A vida na Baía do Araçá [Life in Araçá Bay], published in São Paulo on August 5, 2015.

In 2014, the Office of the State Prosecutor for the Public Interest used the biodiversity data from the bay to support an environmentally-based challenge to an application for another port expansion, which the Companhia Docas de São Sebastião, the state-run port administrator, considered essential in order to receive larger vessels. The expansion, proposed by the state government in 2011, would double the size of the 400,000-square-meter port. After reviewing the environmental impact report prepared by Companhia Docas, the Brazilian Institute of the Environment and Renewable Natural Resources (IBAMA) granted a preliminary permit in December 2013, enabling work to begin on two of the four phases of the project.

Residents of the bay. Teotônio Jesus digs on the beach in search of cockles

Eduardo CesarResidents of the bay. Teotônio Jesus digs on the beach in search of cocklesEduardo Cesar

In a press release to Pesquisa FAPESP, Companhia Docas said that the Preliminary Environmental Permit issued by IBAMA was based on the Environmental Impact Study and the respective Environmental Impact Report drawn up for the project by a multidisciplinary team of some 80 highly qualified professionals, including biologists, geologists, geographers, oceanographers, economists, agronomists, and fishery, environmental, civil and forestry engineers.

According to the press release, the most recent version of the project would preserve the rocky areas that surround the bay, as well as its two small islands and four beaches. In addition, according to Docas, “over the course of the permit process, which began in 2008, the initial project was refined specifically to provide for the most environmentally feasible option, taking into account the technical factors, impact assessment, and engineering and economic considerations. The project evolved to allow for enormous environmental benefits, in particular the drastic reduction of its operational footprint in Araçá Bay, from 84% down to 34%.”

marine worm Diopatra aciculata and microcrustacean Monokalliapseudes schubarti, abundant in the region

Gabriel MonteiroMarine worm Diopatra aciculata and microcrustacean Monokalliapseudes schubarti, abundant in the regionGabriel Monteiro

According to Antonio Carlos Marques, director of the Center for Marine Biology at the University of São Paulo (USP), that figure applies only to the first two phases of the port expansion, not the whole project.

If it is fully approved, the port expansion would involve construction of a concrete slab supported on 17,000 piles embedded into the ocean floor, as an alternative to building earthworks in the bay—the proposal initially considered.

Marques thinks that embedding piles would compromise the water exchange in the bay and prove harmful to the communities of organisms and fish stocks in the region. There could be other effects as well. “Making perforations in the bed of the bay to install piles would mean moving about 140,000 cubic meters of sediment from the bottom of the bay,” he says. “This would release polluting substances that would rise to the surface and alter the current physical makeup of the area.” But according to Companhia Docas, the use of piles “would facilitate water and nutrient exchange with the mangroves, which would promote the preservation of local animal and plant life and the establishment of aquatic fauna—essential ingredients for maintaining and strengthening the trophic food chain.”

Amaral points to another possible effect of port expansion: the proposed slab over the bay would shade a large area of the water. “Without sunlight, algae would be unable to carry out photosynthesis and would die,” she says. “The region would turn into a dead zone as a result,” concludes Alexander Turra, a biologist at the Oceanographic Institute of USP (IO-USP) and a member of Amaral’s team. Like Marques, he questions IBAMA’s environmental permit approval process.

The debate goes on. The Office of the State Prosecutor for the Public Interest had used the arguments posed by the researchers studying the region to challenge the preliminary permit granted by IBAMA. In July 2014, the permit was suspended by preliminary injunction until the case is decided in court.

Residents of the bay. Teotônio Jesus digs on the beach in search of cockles. At left, marine worm Diopatra aciculata and microcrustacean Monokalliapseudes schubarti, abundant in the region. Below, panoramic view of the bay

Eduardo Cesar Panoramic view of the bayEduardo Cesar

Dwidling mangroves
The mangrove stand at Araçá has been shrinking for at least five decades. “The size of the mangrove area around Araçá Bay has been reduced by 70% since the 1960s,” says Caiuá Mani Peres, an oceanographer and member of Turra’s team at IO-USP. Based on historical photographs and satellite images, Peres concluded that the loss of mangroves may have been the effect of a combination of environmental impacts, such as the accumulation of trash and oil deposited there by the waters of the bay, and changes in the sediment caused by the construction of an underwater effluent outlet and other port expansion work begun in 1955.

“A lot has changed in recent times,” says Teotônio Nobre de Jesus, a fisherman who was born in São Sebastião. At 69, his skin weathered by the sun, Mr. Teotônio, as he is called, spends the day crouching on the beach, sifting through the mixture of mud and sand with his hands as he searches for cockles, mollusks whose shells display white veining and small brown and black ridges, scientifically known as Anomalocardia brasiliana. “Look how much I’ve already caught today,” he says on the afternoon of July 20, displaying a bucket with dozens of cockles gathered since morning. In four hours, he has collected almost 30 kilograms. Some will go to his family, and some will be sold to local restaurants that cook them in butter sauce. Then he stands up, wipes the sweat from his forehead with the backs of his hands and points to one of the islands, Ilha de Pernambuco, which is covered by two of the three species of mangroves found in Araçá. “See that hill of trees? That’s what is left of the mangroves. There used to be a lot more, all interconnected.”

Despite the changes, Araçá is home to one of the last remaining mangrove stands on the northern coast of the state of São Paulo. Its tangle of exposed roots keeps the trees standing. The bay supports three species typical of mangrove forests: black mangrove, white mangrove and red mangrove.

The researchers have endeavored to show their findings to the residents of the region and talk with them. The book published in 2015 was one more way of disseminating information and focusing attention on the biological riches of the bay. “We go into schools, we spent time at homes, we talk with fishermen on the beach and invite them to meetings,” Turra says. Mr. Teotônio says he knows the researchers and has heard people talk about the meetings, but he hasn’t yet felt like going.

Project
Biodiversity and functioning of a subtropical coastal ecosystem: a contribution to integrated management (nº 2011/50317-5); Grant Mechanism: Research Grant – Thematic Project; Principal Investigator: Antonia Cecília Zagagnini Amaral (IB-Unicamp); Investment: R$2,986,800.00 (FAPESP).

Scientific articles
VIEIRA, L. M., MIGOTTO, A. E. & WINSTON, J. E. Ctenostomatous Bryozoa from São Paulo, Brazil, with descriptions of twelve new species. Zootaxa. V. 3889, No. 4, p. 485-524. December 2014.
AMARAL, A. C. Z. et al. Araçá: biodiversidade, impactos e ameaças. Biota Neotropica. V. 10, No. 1, p. 219-64. March 2010.

Book
AMARAL, A. C. Z. et al. A vida na Baía do Araçá – Diversidade e importância. São Paulo: Lume, 2015.

Republish