The Fate of Cold-Water Corals in a Changing World: A Geological Perspective

As “ecosystem engineers,” framework-forming scleractinian cold-water corals (CWC) build reefs that are unique biodiversity hotspots in the deep sea. Studies using common biological techniques such as correlating the spatial occurrence of the most common CWC species with modeled environmental conditions have revealed the ecological requirements and tolerances of these species. However, limited field observations and poorly understood geographical distribution patterns of the CWC restrict the application of existing knowledge toward assessing their fate (e.g., local extinction, newly established populations) under ongoing global change. Hence, the risk to cross ecological tipping points causing the demise (or establishment) of entire CWC reefs remains unclear. A major challenge is to identify the key environmental parameters (or stressors) having the potential to control CWC vitality by providing such tipping points. This is largely hampered by the overall lack of present-day observations of such tipping point crossings. However, evidence for such events is frequently preserved in geological records revealing that entire CWC ecosystems vanished or returned at specific moments in the past. Here, a geological approach is presented that by correlating geological CWC records with paleoceanographic data describing past environmental changes allows to identify a set of key environmental drivers that directly or indirectly control CWC vitality. Thus, by combining such a geological approach with common biological techniques (see above) to describe the ecological tolerance of the most important reef-building CWC has a great potential to better assess their future spatial distribution in times of accelerating global change and to improve the sustainable management of the important deep-sea ecosystems formed by CWC

Caracterização paleoceanográfica do testemunho JPC-95, margem continental Sul Brasileira, com base em foraminíferos planctônicos e isótopos estáveis de oxigênio

As freqüentes oscilações climáticas ocorridas nos últimos dois milhões de anos geraram grandes transformações na biodiversidade, na dinâmica de circulação oceânica e nas propriedades físico-químicas dos oceanos. Em estudos com abordagens paleoceanográficas e paleoclimáticas a partir de sedimentos oceânicos, é reconhecida a alta sensibilidade dos foraminíferos planctônicos às variações na temperatura da água do mar, com decorrente flutuação na diversidade e abundância relativa dos vários táxons. Por outro lado, a precipitação do CaCO3 ocorre em equilíbrio com o ambiente, possibilitando identificar variações paleoceanográficas e paleoclimáticas através da composição isotópica das carapaças de foraminíferos. Desse modo, é possível correlacionar as variações isotópicas com a freqüência dos táxons de foraminíferos planctônicos ao longo de um testemunho, permitindo inferências sobre a paleoceanografia e o paleoclima de uma região. O trabalho identificou as variações paleoceanográficas no talude da margem continental Sul brasileira através da análise da freqüência de táxons de foraminíferos planctônicos correlacionando-os com isótopos estáveis de oxigênio extraídos das carapaças de foraminíferos bentônicos, através do estudo do testemunho JPC 95, coletado em 1998, durante o cruzeiro KNORR 159-5, do Woods Hole Oceanographic Institution (WHOI – EUA), no talude da Bacia de Santos (270 52,73’ S e 460 55,25’ W). Foram identificados três grandes intervalos paleoclimáticos: o último intervalo interglacial (1641cm – 920 cm) e o último glacial (911 – 20 cm) ocorridos durante o Pleistoceno, além do intervalo pós-glacial (11cm – topo), correspondente ao Holoceno; esse intervalos são também correlacionáveis, respectivamente, às Biozonas X , Y e Z, e aos Estágios Isotópicos Marinhos 5, 4/3/2 e 1. Também foram reconhecidas flutuações paleoclimáticas ao longo dos intervalos interglaciais e glaciais do Pleistoceno, as quais correspondem às subzonas X1 a X6 e Y1 a Y5. A associação microfossilifera encontrada nesses intervalos sugere influência das águas quentes da Corrente do Brasil durante o intervalo de tempo representado pelas Biozonas X e Z; e influência da Zona de Convergência Subtropical/Subantártica e/ou das águas frias da Corrente das Malvinas durante o tempo correlacionável à Biozona Y. A comparação dos resultados das associações de foraminíferos planctônicos com análises isotópicas de d18O em carapaças de foraminíferos bentônicos para os cinco metros superiores do testemunho sugerem que os ambientes bentônico e pelágico responderam diferentemente às pequenas flutuações paleoceanográficas durante a porção final do último intervalo glacial (subzonas Y3 superior, Y2 e Y1), na região estudada. O posicionamento do limite Pleistoceno / Holoceno foi confirmado por uma datação de 14C, obtida pra a amostra 16,5 cm. Taxas de sedimentação foram estimadas para os diversos intervalos reconhecidos no testemunho JPC95Conselho Nacional de Desenvolvimento Científico e TecnológicoThe frequent climatic oscillations during the past two million years has caused great changes in biodiversity, on ocean circulation patterns and in the physicochemical properties of seawater. Since the precipitation of CaCO3 occurs in equilibrium with the water environment, it is possible to evaluate the paleoceanography and paleoclimatic variations through the biogenic calcareous isotopic composition of marine sediment. Among others, planktic foraminifera are important paleoceanographic proxies in the ocean due to their high sensitivity to temperature variations of sea water masses. These changes are evident on diversity and relative abundance of the species, and therefore it’s possible to correlate the stable isotopic records with the changes on planktonic foraminiferal populations. The work identified the paleoceanographic variations on the south Brazilian continental margin slope using planktonic foraminifera frequency of species and stable oxygen isotopes extracted from benthic foraminifera on the core JPC-95, collected in 1998 during cruise on the R/V KNORR 159-5 from Woods Hole Oceanographic Institution (WHOI,EUA), which was retrieved from the slope of Santos Basin at coordinates 270 52,73’ S and 460 55,25’ W. In this study three major paleoclimatic intervals were recognized, the last interglacial interval (base at 1641cm – 920 cm) and the last glacial interval (911cm – 20 cm), which occurred during the Pleistocene, besides the Post-glacial interval ( 11cm – 3 cm) that corresponds to the Holocene. These are similar to Biozones X, Y and Z and it was possible to further subdivide the core data into paleoclimatic fluctuations during the last interglacial and glacial intervals from the Pleistocene, which correspond to X1 to X6 and Y1 to Y5 . Further, through the use of stable oxygen isotopes it was possible to recognize the Marine Isotopic Stages 1 and 2 (MIS 1 and 2), that corresponds to post- glacial and glacial intervals. The planktonic foraminifera association suggests to the intervals represented by biozones X and Z the influence of warm water masses of Brazil current; and the influence of the subtropical/subantarctic convergence zone and/or cold water of Malvinas current during the time interval related to biozone Y. The correlation of planktonic foraminifera with d18O isotopic data from benthic foraminifera to the top 5m of the core suggest that benthic and pelagic environments responded differently to the short term paleoceanographic changes during the final portion of the last glacial at this region (upper subzone Y3, Y2 and Y1). The Pleistocene/Holocene limit was confirmed through a radiocarbon dating at sample 16,5cm. Sedimentation rates were estimated to several intervals within JPC95 core.85 f

Paleoceanografia do Sudeste do Atlântico Sul: registros de eventos abruptos nos últimos 50.000 anos

O Atlântico Sul desempenha um papel fundamental no controle do clima mundial, interligando os oceanos Indico e Pacífico, sendo principal fornecedor de calor para o Atlântico Norte. Com os crescentes debates sobre as variações climáticas e o aquecimento global, aumenta o interesse dos cientistas em entender as causas, a freqüência e intensidade dos processos envolvidos nas variações climáticas em diversas escalas espaçotemporal e na avaliação de tendências paleoclimáticas de longo prazo. O presente trabalho teve como objetivo reconstituir a paleotemperatura e paleossalinidade das águas oceânicas superficiais bem como reconhecer, no setor Sudoeste do Atlântico Sul, a ocorrência de eventos paleoclimáticos abruptos ocorridos durante os últimos 50ka. Para isso foram realizadas análises isotópicas (d18O), geoquímica orgânica (porcentagem de COT, N, razão C/N e d13CMO), razão Mg/Ca em Globigerinoides ruber para os cinco primeiros metros superficiais do testemunho JPC-17 (27o41.83’S, 46o29.64’W). Avaliou-se também o padrão de freqüência de taxons de foraminíferos planctônicos dos testemunhos JPC-17, JPC-95 (27o52,73’S, 46o55,25’W) e GeoB6206-3 (30°12,40’S, 46°33,30’W) também coletados na região. Os sedimentos do testemunho JPC-17 recuperaram os últimos 46.6ka, abrangendo a última glaciação e o Holoceno, na qual corresponderam aos estágios isotópicos 3 ao 1 (MIS-3, MIS-2 e MIS-1). A temperatura oscilou entre 200C (durante o intervalo glacial) e 24.30C (início do Holoceno) enquanto que os valores de 18OW (proxy para salinidade) flutuou entre 0.79‰ (durante o intervalo glacial) e 2.4‰ (início do Holoceno). Foi possível reconhecer dois intervalos de aumento relativo na temperatura (TSM) e salinidade (SSM) ao longo dos últimos 46.6ka no qual foram reconhecidas as assinaturas do último Máximo Glacial (UMG) e do Heirinch Event 1 (H1). O UMG foi em torno de 10C mais frio em relação ao Holoceno. Foi observada uma queda da temperatura e salinidade entre 14.8 – 11.9ka provavelmente relacionado aos eventos climáticos Bollin/Allerod (B/A) ocorrido na Groelândia e no Atlântico Norte e o ACR (Antartic Cold Reversal) ocorrido quase simultaneamente na Antártica durante a última deglaciação. Durante o Holoceno foi observado um pico de redução da temperatura e de aumento da salinidade relacionado ao evento frio de 8.2ka. Este trabalho revela que as variações na TSM e SSM coincidiram com variações climáticas ocorridas no Hemisfério Norte associadas a flutuações na formação da Água de fundo do Atlântico Norte (North Atlantic Deep Water - NADW) e na circulação meridional do Atlântico (Atlantic Meridional overturning circulation – AMOC). As águas da Corrente Sul Equatorial (South Equatorial Current- SEC) são transportadas pela Corrente Norte do Brasil (CNB) para o Atlântico Norte para compensar a formação da AFAN/Circulação Termohalina (CTH), enfraquecendo a Corrente do Brasil (CB) e o transporte de calor e salinidade para o Atlântico Sul. Variações no regime de chuvas na região possivelmente desempenham papel importante nas variações da salinidade das águas oceânicas na região, porem as mudanças na circulação oceânica parece ser a principal responsável pelas oscilações da TSM e SSM na região. A frequência dos taxons de foraminíferos planctônicos visivelmente responde mais as variações na TSM e SSM do que a produtividade. Foi evidenciado que a matéria orgânica produzida foi exclusivamente marinha (algas fitoplanctônicas), com uma leve mudança no tipo e a fonte dessa matéria orgânica durante o intervalo glacial e o Holoceno, não estando relacionada a mudanças na circulação oceânica.Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorConselho Nacional de Desenvolvimento Científico e TecnológicoThe South Atlantic Ocean plays a crucial role in global climate control linking the Indian and the Pacific Oceans, acting as the main heat source to the North Atlantic Ocean. With increasing of debates about the climate changes and global warming increase the interesting of scientists to wonder the causes, the frequency and intensity of process behind the climate oscillations in a variety of space-temporal scales and long term paleoclimatic tend evaluation. This work had as its objective the recreation of oceanic water’s surface paleotemperature and paleosalinity as well as the recognition of records from abrupt climate changes that took place during the last 50ky in the Southwestern sector of the South Atlantic Ocean. Thus, in order to obtain such information, it was necessary to conduct analyses of oxygen isotopes (18O), organic geochemistry (percentage of TOC, Nitrogen, C/N ratio and 13C of organic matter, Mg/Ca ratio in Globigerinoides ruber to the upper five meters of the core JPC-17 (27o 41.83’ S, 46o29.64’W). Frequency pattern of planktonic foraminifera from cores JPC-17, JPC-95 (27o52,73’S, 46o55,25’W) and GeoB6206-3 (30°12,40’S, 46°33,30’W) also drilled in the area. Sediments from core JPC-17 recorded the last 46.6 ky, including the last glaciations and the Holocene, which corresponded to Marine Isotope Stages 3 to 1 (MIS- 3, MIS-2 and MIS1). The temperature ranged from 200C (during glacial intervals) to 24.30C (Early Holocene), while 18OW values (proxy of salinity) ranged from 0.79‰ (during glacial intervals) to 2.4‰ (Early Holocene). It was possible to indentify two intervals of relative temperature (TSM) and salinity (SSM) increase during the last 46.6 ky, which were linked to the Last Glacial Maximum (LGM) and the Heinrich event 1 (H1). The LGM was around 10C colder than the Holocene. Moreover, a temperature and salinity reduction from 14.8 ky to 11.9 ky was observed, which is probably linked to the Bollin/Allerod (B/A) climate event and Antarctic Cold Reversal (ACR) that took place simultaneously during the last deglaciation of the Northern and Southern hemispheres respectively. During the Holocene, the evidence of a sharp temperature fall and a salinity increase linked to the 8.2 ky cold event was identified. This study shows that TSM and SSM changes in the Southwestern Subtropical Atlantic matched precisely with the Northern Hemisphere climate changes associated to the North Atlantic Deep Water (NADW) formation and the Atlantic Meridional Overturning Circulation (AMOC) changes. Besides, South Equatorial Current Waters (SEC) are transported by the North Brazilian Current (NBC) to North Atlantic to compensate the NADW formation/Termohalina Circulation (THC), weakening the Brazilian Current (BC), its heat and its salinity transport to the South Atlantic. In addition, regional rainy variations play an important role in local ocean water salinity changes. However, ocean circulation changes seem to be the main driver linked to regional SST and SSS changes. The frequency of planktonic foraminifera is cLEArly more influenced by SST and SSS’s changes than in productivity. It was shown that organic matter was exclusively synthesized by marine fitoplanktonic organisms, with a small change in the type and source of these organic matter during glacial the interval and the Holocene, are not related to ocean circulation change

Variability of the upwelling system in the southeastern Brazilian margin for the last 110,000 years

Western boundary upwelling systems such as those found in the southeastern Brazilian margin (SBM) are promoted by special atmospheric and oceanographic interactionswith topography of the coastline. In order to investigate the evolution of the upwelling systemin SBMover the past 110 kyr, the abundance of Globigerina bulloides (a planktonic foraminiferal species typically associated with upwelling waters) from two marine cores was combined with estimates of upper water thermal structure derived from Modern Analog Technique based on planktonic foraminifera. High abundances (up to 35%) of large specimens of G. bulloides (=250 μm) associated with cooling subsurface waters reveal the occurrence of an intense coastal upwelling system between 110 kyr and 88 kyr. Changes in coastline orientation due to lower sea level stand (20-70 m lower than today) and a longer season of vigorous Brazil Current (BC) and prevailing northeasterly winds maintained permanently the cold and nutrient-rich South Atlantic Central Waters (SACW) over the shelf promoting the strongest upwelling system of the Brazilian coast over the past 110 kyr. At 88 kyr, a sharp reduction of 14% in abundance of G. bulloides and a 2.6 °C warming of the water column indicates an abrupt weakening of the coastal upwelling, probably caused by a disturbance in SACW formation. During the last glaciation, longer current winter-like conditions of prevailing southwesterly winds and a weakened Brazil Current suppressed the upwelling system in SBM. At this time, constant and relatively high abundance of G. bulloides (up to 10%) suggest that the coastal upwelling was restricted to a short period of months year-round, when the BC and northeasterly winds were relatively vigorous despite the glacial context. The predominance of warm and oligotrophic Tropical Waters due to the shutdown of coastal upwelling in northern SBM was inferred for the last 20 kyr. Despite vigorous northeasterly winds and BC strength, high sea level stand during the Holocene submersed the Abrolhos Bank (AB) leading to a new coastline configuration. Presently, the interaction between the AB and the BC generated a newoceanographic feature in SBM, the Vitória Eddy,with very limited efficiency in producing a strong upwelling such as the one recorded in the past

Abundance of Globorotalia crassaformis in cores GL-74 and GL-75 from southeastern Brazilian Margin since the last interglacial MIS 5

We are providing records of Globorotalia crassaformis as a new late Quaternary biostratigraphic marker for the southeastern Brazilian margin