Impactos de um ambiente em mudança nos recifes de corais marginais do Oceano Atlântico Tropical

Novo artigo publicado na revista Ocean and Coastal Management pelo GT1.2 (Recifes e Ecossistemas Coralinos), intitulado “Impacts of a changing environment on marginal coral reefs in the Tropical Southwestern Atlantic”, de autoria de Marcelo Oliveira Soares, Sergio Rossi, Anne Rebouças Gurgel, Caroline Costa Lucas, Tallita Cruz Lopes Tavares, Beatriz Diniz, Caroline Vieira Feitosa, Emanuelle Fontenele Rabelo, Pedro Henrique Cipresso Pereira, Ruy Kenji Papa de Kikuchi, Zelinda M.A.N. Leão, Igor Cristino Silva Cruz, Pedro Bastos de Macedo Carneiro, Lorenzo Alvarez-Filip, discute os efeitos de múltiplas pressões sobre os recifes brasileiros.

Uma ampla avaliação revela que eventos de branqueamento afetaram 26 espécies nos últimos 26 anos (1994–2020). Entre 1994 e 2018 nenhuma espécie sofreu mortalidade em massa após o branqueamento. No entanto, as ondas de calor recentes e intensas de 2019 e 2020 causaram altas taxas de mortalidade em vários corais mostrando que esses recifes não são protegidos a longo prazo e nem refúgios universais. Essas mudanças e outros fatores como pesca🪝, urbanização, mineração, derramamentos de óleo, aumento da sedimentação, ondas de calor, lixo marinho, contaminação urbana, efluentes agrícolas e industriais e espécies invasoras são as pressões mais severas.

O artigo também discute a "hipótese de refúgio do recife brasileiro" a qual poderia ser parcialmente aplicada para alguns corais resistentes ao estresse durante distúrbios agudos (refúgio de curto prazo). No entanto, tal fato não garante que os recifes brasileiros devem ser assumidos como um ecossistema que servirá de refúgio contra as mudanças climáticas.

Por fim, os autores argumentam que é essencial a adoção de estratégias de gestão a nível local e global.

Acesse e compartilhe o artigo completo pelo link: https://authors.elsevier.com/a/1d9-K3RKK-qP4f

RESUMO

The peculiar shallow-water reefs of the Tropical Southwestern Atlantic Ocean have thrived in conditions considered suboptimal (e.g., moderate turbidity, higher level of nutrients, and resuspension of sediments) under the optics of classical coral reefs. Recently, these marginal reefs have been hypothesized to provide climate-change refugia from natural and anthropogenic impacts; yet with little empirical evidence. Therefore, in this article we discuss the known effects of multiple pressures on the Brazilian reefs. A wide evaluation of the peer reviewed literature reported that bleaching events affected 26 species of scleractinians, hydrocorals, octocorals, and zoanthids in turbidzone reefs over the last 26 years (1994–2020) in the Tropical SW Atlantic Brazil. Between 1994 and 2018 no species suffered post-bleaching mass mortality. However, the recent and intense heatwaves of 2019 and 2020 caused higher mortality rates in several key foundation corals (e.g., Millepora alcicornis, Millepora braziliensis, and Mussismilia harttii) showing that the SW Atlantic reefs are not long-term protected and universal refuges. Moreover, other direct and indirect human pressures threaten these tropical reefs. Local and regional (e.g., pollution and fisheries) and large-scale pressures (e.g., global warming and marine heatwaves) act simultaneously on the health of these reefs, which intensifies negative species-specific impacts. We outline the occurrence of pressures that have been important factors responsible for the reduction in species richness and reef fish biomass, changing geoecological functions, altered reef composition and dominant morpho-functional groups, as well as phase shifts. Along with large-scale climatic changes, such as heatwaves, fisheries, urbanization, mining disasters, oil spills, increased sedimentation, increased warming, marine debris, contamination by domestic, agricultural, and industrial effluents, and introduction of invasive species are likely the most severe pressures on Brazilian reefs. We discuss that the “Brazilian reef refuge hypothesis” could be partially applied for some stress-tolerant massive corals during acute disturbances (short-term refuge); yet should not be assumed as a reef ecosystem-wide feature under ongoing environmental change. Therefore, we argue that it is essential to alleviate the main local and regional human impacts and to adopt resilient-based management strategies at local and global scales to protect the lowfunctional redundancy and higher endemism of these unique marginal coral reefs.

TAOS (Tropical Atlantic Observing System)

Foi publicado em maio de 2021 o relatório completo do TAOS (Tropical Atlantic Observing System) que teve entre seus autores principais o prof. Moacyr Araujo, coordenador do do GT3.0 (Variabilidade climática, ciclos biogeoquímicos e fluxo de CO2 no oceano Atlântico tropical) do inctAmbtropic. O relatório resume os resultados de duas oficinas realizadas e discussões subsequentes do comitê revisor, incluindo contribuições de outros membros da comunidade de pesquisadores que atuam no Atlântico Tropical (você pode fazer o "download"do relatório ao final desta postagem).

Abaixo alguns trechos do Resumo Executivo:

"The tropical Atlantic is the smallest of Earth’s tropical ocean basins, one half the width, west to east, of the tropical Indian Ocean and less than one fifth that of the tropical Pacific. Thus, the tropical Atlantic interacts intimately with its bordering lands, strongly influencing their weather and climates, and it is readily accessible by the region’s inhabitants. At the same time, the tropical Atlantic plays an outsized role in the global climate system. Through the Atlantic Meridional Overturning Circulation (AMOC), it delivers nearly half a petawatt of energy from the Southern to the Northern Hemisphere, and it has marked, if still not fully understood, impacts on globally significant variations in the tropical Indian and Pacific Oceans"

"All countries bordering the tropical Atlantic experience important societal challenges driven by regional ocean processes and air-sea-land interactions. These are exacerbated by climate change, which induces new emerging threats. Examples include floods and droughts in South America and West Africa, more intense storms and hurricanes, and continuing sea-level rise that increases flooding risks and episodes of coastal erosion. Other regional emerging extreme events such as ocean heat-waves and episodes of anoxia and acidification amplify the vulnerabilities of regional marine ecosystems – systems already stressed by overfishing and pollution. Moreover, recent studies show that the tropical Atlantic has two-way connections with the Pacific and appears to play a driver role in mid- and high-latitude climatic events including the occurrence of impactful mid-latitude extremes throughout the year)".

"The present TAOS review comes at an inflexion point for the tropical Atlantic, where scientific progress, demands on its resources, and environmental changes resulting from local and global stressors simultaneously are accelerating. At this juncture, there are great rewards to be reaped from an enhanced and invigorated TAOS, rationally planned and responsibly governed and coordinated. This report offers the rationale and the strategy for achieving a TAOS that will be well suited to serve the societal and scientific needs of the Atlantic basin and the globe over the coming decades. The recommended enhancements to the observing system across the range of platforms, with their associated sampling timescales, variables measured, and ranges of depths is expected lead to improved forecasts and projections of phenomena ranging from daily weather, fisheries and coastal managements, to anthropogenic climate change over multiple decades".

TAOS Review Report_final_13May2021.pdf

Fazer download de PDF • 7.61MB

Mudanças Climáticas e a Evolução Holocênica do Delta do rio São Francisco

Um trabalho recentemente publicado na revista Marine Geology (IF: 3.04) pelo GT1.1 (Deltas e Erosão da Linha de Costa) intitulado "Effects of Holocene climate changes and anthropogenic river regulation in the development of a wave-dominated delta: The São Francisco River (eastern Brazil)" de autoria de José Maria Landim Dominguez e Junia Kacenelenbogen Guimarães, discute os efeitos das mudanças climáticas durante o Holoceno e da regulação antropogênica do rio São Francisco no desenvolvimento do seu delta e conclui que a construção do delta ocorreu em pulsos associados a períodos mais úmidos na bacia hidrográfica. O artigo também discute as causas da erosão severa que afeta a desembocadura fluvial nas última décadas.

Modelo evolutivo do delta do São Francisco, durante o Holoceno

Erosão da linha de costa durante o periodo 1960-2020 no delta do São Francisco ABSTRACT

The São Francisco River is the fourth longest river in South America and one of the most regulated. Severe coastalerosion has affected the delta shoreline since 1985, leading to the complete destruction of Cabeço village be- tween 1997 and 1999. In this study, we mapped and radiocarbon dated the beach ridge sets occurring on the delta plain and performed a detailed analysis of the delta shoreline changes since 1960. During the Holocene, the delta plain construction was punctuated and took place during episodes of higher river discharges coincident with Bond events 4, 2 and 1 and periods of higher precipitation in the river basin, as reconstructed by δ18O measurements in cave speleothems. The last major episode of delta construction apparently ended at approxi- mately 1.0 ka cal. BP. Since that time, riverine sediment input has been just sufficient to maintain the shoreline. A comparison of historical maps and aerial photographs showed that from 1853 to 1960, the shoreline at the river mouth remained in approximately the same position. A decrease in rainfall in combination with river regulation, particularly after 1985, triggered extensive erosion at the delta shoreline. This erosion was not caused by sediment retention behind the major dams but instead resulted from changes in the backwater/drawdown effects deriving from river regulation. Shoreline erosion mostly affected the river mouth. The mobilized sediments caused progradation of the downdrift shoreline. Updrift of the river mouth, the shoreline remained stable, as it had already reached an equilibrium orientation in which the net longshore transport was zero

O trabalho completo pode ser acessado em: https://doi.org/10.1016/j.margeo.2021.106456