Yara Schaeffer-Novelli

Variability of mangrove ecosystems along the Brazilian coast

Brazilian mangroves extend from 4°30′N to 28°30′S, varying greatly in growth form, species distribution patterns, and stand structure, in spite of a limited floristic diversity. We divided the Brazilian coastline into eight units, within which physiographic and climatic conditions are relatively uniform, and described mangrove occurrence, species distribution and structural attributes characteristic of each segment. In general, greates mangrove coverage and greatest forest stature are found in areas with a large surplus of rainfall over potential evapotranspiration and macrotidal regimes. An exception was the segment containing the mouth of the Amazon river, where freshwater systems dominate over brackish or marine associations. We believe that the variability in species associations and the dominance of each in a given environment is predominantly determined by the characteristics of the landforms that can be colonized by each species in a given region. The type, size, and frequency of occurrence of available landforms is a function of the particular mix of fluvial, tidal, and wave energies found in a region. Different species colonize these sites depending on their adaptations and edaphic preferences. Climate affects mangrove colonization and growth. We suggest that Brazilian mangroves play a minor role in modifying the geomorphic setting; the spatial arrangement of the various forest types is a response to the underlying topography and edaphic conditions, and to the constraints imposed by climatic and hydrologic factors. The spatial arrangement of species does not necessarily show successional processes, but may be the result of direct and differential colonization on appropriate substrates.

The Cananéia Lagoon estuarine system, São Paulo, Brazil

The Cananéia Lagoon estuarine system lies at 25°S, near the latitudinal limit for mangroves. It is 110 km long, consisting of 1–3 km wide channels behind a barrier island, with narrow inlets at the southern and northern ends. Average and maximum depths are 6 m and 12 m. The system is microtidal and subtropical. Mean annual temperature is 21.4°C (annual amplitude=7.0°C). When the area receives sporadic frosts, temperatures close to 2°C occur in the estuary. Annual precipitation (2,270 mm) exceeds annual potential evapotranspiration (1,656 mm). The water budget of the 1,339 km2 watershed is controlled primarily by local rainfall. Before 1978, a large river discharged a significant portion of its flow into the lagoon, but closure of the diversionary channel has since caused changes in salinity, phytoplankton populations, and mangrove coverage. About 90 km2 of intertidal habitat is occupied by mangroves and tidal marsh; mangroves are dominant. Fringe and riverine forests (dominated byRhizophora) are more structurally developed than the basins dominated byLaguncularia and have higher litterfall rates (2.08 g m−2 d−1, fringes; 1.04 g m−2d−1, basins). Primary production exhibits pronounced seasonal pulses; heterotrophic processes lag photosynthetic production and are partially driven by particulate matter inputs. Synthetic models must consider the spatial and temporal heterogeneity of this region.

Araçá: biodiversidade, impactos e ameaças

Araca Bay (Sao Sebastiao, State of Sao Paulo), within one of Brazils most beautiful coastlines, has small relict mangrove stands and a very diverse marine ecosystem. As such, the bay is a natural laboratory as well as important for local small scale fishing. In this study we summarize the large literature base to comprehensibly list the flora and fauna as a preliminary biodiversity inventory of Araca Bay. We place this in the historical context of human impact on the environment of the bay and we emphasize new, introduced and threatened species as bioindicators and natural resources. With this information, we provide a basis to inform conservation decisions as well as data for conservation management plans and call attention to the urgent need to protect this fragile environment and biota. We also emphasize that this small and uniquely biologically rich bay should be preserved, revitalized and integrated into the growing urban environment.

Oil spills in mangroves: a conceptual model based on long-term field observations

Abstract A conceptual model is proposed for evaluating residence time of oil in mangrove environments. It assumes that, after oil has spread over a mangrove coastline, it remains in the environment by retention in the sediment. Removal is mainly in association with seaward particle export. Since detritus export depends on tidal flush, the area affected by an oil spill can be divided into sections parallel to the coastline having different removal rates increasing seaward (under little river flush and regular topography).

Chapter Nine Mangroves as indicators of sea level change in the muddy coasts of the world

Abstract Great concern has been expressed regarding the impacts of global warming and sea level rise on coastal areas and associated wetlands. Mangroves have been identified as potentially good indicators for detecting and monitoring sea level changes, because they occupy unconsolidated sediments subject to processes which would be influenced by sea level changes, and are known to display rapid responses to hydrological, geomorphic and climatic changes. Because mangroves develop under varying tidal regimes and imputs of fresh water, nutrients and sediments, patterns of response to sea level changes cannot be easily extrapolated from one location to another. In this paper, we suggest that Thoms (1984) physiographic classification of mangrove environments, coupled with an eco-regional approach, could be used to develop a framework for implementing long-term studies, monitoring sea-level changes, and help plan appropriate management policies to address the expected impacts.

Long-term effects of oil pollution in mangrove forests (Baixada Santista, Southeast Brazil) detected using a GIS-based multitemporal analysis of aerial photographs

Oil spills are potential threats to the integrity of highly productive coastal wetlands, such as mangrove forests. In October 1983, a mangrove area of nearly 300 ha located on the southeastern coast of Brazil was impacted by a 3.5 million liter crude oil spill released by a broken pipeline. In order to assess the long-term effects of oil pollution on mangrove vegetation, we carried out a GIS-based multitemporal analysis of aerial photographs of the years 1962, 1994, 2000 and 2003. Photointerpretation, visual classification, class quantification, ground-truth and vegetation structure data were combined to evaluate the oil impact. Before the spill, the mangroves exhibited a homogeneous canopy and well-developed stands. More than ten years after the spill, the mangrove vegetation exhibited three distinct zones reflecting the long-term effects of the oil pollution. The most impacted zone (10.5 ha) presented dead trees, exposed substrate and recovering stands with reduced structural development. We suggest that the distinct impact and recovery zones reflect the spatial variability of oil removal rates in the mangrove forest. This study identifies the multitemporal analysis of aerial photographs as a useful tool for assessing a systems capacity for recovery and monitoring the long-term residual effects of pollutants on vegetation dynamics, thus giving support to mangrove forest management and conservation.

Analysis of mangrove forest succession, using sediment cores: a case study in the Cananéia-Iguape coastal system, São Paulo Brazil

Sediment cores are an essential tool for the analysis of the dynamics of mangrove succession. Coring was used to correlate changes in depositional environments and lateral sedimentary facies with discrete stages of forest succession at the Cananeia-Iguape Coastal System in southeastern Brazil. A local level successional pattern was examined based on four core series T1) a sediment bank; T2) a smooth cordgrass Spartina alterniflora bank; T3) an active mangrove progradation fringe dominated by Laguncularia racemosa, and; T4) a mature mangrove forest dominated by Avicennia schaueriana. Cores were macroscopically described in terms of color, texture, sedimentary structure and organic components. The base of all cores exhibited a similar pattern suggesting common vertical progressive changes in depositional conditions and subsequent successional colonization pattern throughout the forest. The progradation zone is an exposed bank, colonized by S. alterniflora. L. racemosa, replaces S. alterniflora as progradation takes place. As the substrate consolidates A. schaueriana replaces L. racemosa and attains the greatest structural development in the mature forest. Cores collected within the A. schaueriana dominated stand contained S. alterniflora fragments near the base, confirming that a smooth cordgrass habitat characterized the establishment and early seral stages. Cores provide a reliable approach to describe local-level successional sequences in dynamic settings subject to drivers operating on multiple temporal and spatial scales where spatial heterogeneity can lead to multiple equilibria and where similar successional end-points may be reached through convergent paths.

Análise populacional de Anomalocardia brasiliana (Gmelin, 1791), na Praia do Saco da Ribeira, Ubatuba, Estado de São Paulo

Monthly quantitative sampling of the beach benthic macro fauna was made from June 1972 through December 1974. Determinations of the distribution index, length |dry weight correlation and vertical distribution pattern was also made.

Mangrove vegetation decreases density but does not affect species richness and trophic structure of intertidal polychaete assemblages

The positive influence of mangrove vegetation on macrobenthic communities has been widely investigated, but studies mainly focused on epibenthic assemblages. Given the contrasting characteristics between epifauna and infauna, we expected that mangrove vegetation would not exert the same positive effect on infaunal assemblages. To test this hypothesis, we investigated polychaete assemblages in mangrove stands in a tidal flat in Southeast Brazil. Specifically, we focused on (a) whether polychaete assemblages (i.e., density, richness, community, and feeding guild composition) are different inside and outside mangrove stands, and (b) if changes are related to root biomass. Our results showed that mangrove areas have lower polychaete density than that of adjacent sandflats, and polychaete density is negatively related to root biomass. Species richness was not affected by the presence of vegetation, but the number of exclusive species was higher inside the mangrove. Changes in composition of polychaete assemblages were mainly attributable to reductions in species density rather than species replacement. Trophic structure was not influenced by mangrove vegetation, as subsurface-feeders dominated inside and outside mangrove zones. Our results contrast with the richness enhancement found for epibenthic fauna inside mangroves, and highlight that mangrove vegetation does not exert the same influence on epibenthic as that on infaunal assemblages.

Status of mangrove research in Latin America and the Caribbean

For those in the eastern hemisphere, the most striking characteristic of New World mangroves must be their low diversity. However, this apparent simplicity is deceptive, New World mangrove species are extraordinarily plastic in their adaptations to their environment. On a geographic basis mangroves attain their greatest development where rainfall and tidal subsidies are abundant. These conditions occur in the northwest part of South American continent and on the eastern seabord, south of the Gulf of Paria (Venezuela) to Sao Luis, in Brazil. In the 1970s events related to the developing environmental movement in the United States led to a marked interest in these systems, their ecology and management, pointing out the ecological role of mangroves as sources of organic matter to estuarine food webs.The economic recession of the 80s and its impact on funding agencies, both national and international, and changing national priorities have dramaticaly curtailed scientific research. Research in the region is now almost totally supported by local institutions.The alarming rate at which mangroves are being destroyed in the region requires that prompt action be taken to develop a regional program such as the one recommended in the UNESCO Cali 1978 meeting, capable of fostering and supporting ecosystemic research, the development and compilation of management guidelines and the training of scientific personnel, resource managers, and providing for public environmental education. These guidelines and strategies for effective management of a complex resource can only be developed through research.