Posts Tagged 'field'

Kon-Tiki2 expedition 2015-2016: scientific cruise report

The Kon-Tiki2 Expedition was partly an anthropogenic exploration and partly an interdisciplinary oceanic and atmospheric research expedition. As a research expedition it was unique for three reasons: 1) The type of vessel used, 2) the timing of the expedition, and 3) the geographical location. The scientific program was run onboard the ancient design balsa rafts, powered by solar power only, with almost no possibility of stopping the raft, during a year with the strongest El Niño recorded in human history, in the midst of the center of that El Niño, namely in the area between Peru, Easter Island and the Chilean mid-latitudinal coast.

The scientific expedition planned and organized as a cooperation between the NIVA and NTNU in Norway. It was divided in two legs: the transect from Peru to Easter island and from Easter Island until the expedition concluded with the organized evacuation of the rafts. Instruments were brought on board the rafts and procedures were specifically developed for this cruise to study 1) climate change and ocean acidification, 2) marine litter, 3) El Niño and operational weather forecasting and 4) marine life.

The rafts were built following the designs of archeological studies on an Ecuadorian maritime culture known as the Manteno. They were built in Peru, with help from volunteers from all over the world as well as from the national Peruvian Navy. Building efforts were delayed by logistic issues, but Leg 1 departed Callao on November 7th 2015 and reached the Easter Island as planned 6 weeks later, on December 19th 2015. After a change of crew and a full overhaul of the rafts and equipment in Easter Island, Leg 2 departed Easter Island January 6 and ended March 17 2016.

The crew was multinational, gender-mixed, synergetic and multidisciplinary experienced. Each raft on each leg had 7 members on board. Only four members were present during both legs. There was a one scientist on board on each leg representing either of the organizing institutions.

Both rafts were instrumented for research. Each had an electrical installation with capacity calculated according to the payload of instruments that would be operated from it. Wind was the main source of energy to transport the vessels while photovoltaic cells transformed solar into electric energy for the electronics onboard.

The sensor payloads can be classified into three categories: atmospheric, oceanographic and ecological. Optical sensors to measure light, together with physical sensors to measure atmospheric conditions were combined with crew observations to describe the meteorological situation in the raft. A combination of echosounders and cameras were used to describe the macrofauna biodiversity present around the rafts. DNA and Chlorophyll a filtering aimed to study the microdiversity. The physical parameters like temperature, salinity, pH, levels of carbon dioxide described the climatic conditions in the region were the cruise sailed. Finally, both conventional and state-of-the-art technology were used to observe macro and micro plastics in this remote area of the world oceans.

Currently, the material collected on the cruise is subject of analysis in different laboratories. Kon-Tiki2, due to its unique nature, has been the subject of interest to a wide range of audiences. In addition to the general scientific interest, the expedition has given a much louder voice to the oceans than any regular research expedition could have given. For instance, the expedition coincided with the Climate Summit in Paris in December 2015 (COP21), a coincidence that we utilized to its fullest. The outreach efforts of the expedition participants have raised awareness about the science as well as about the expeditions sponsors. Most importantly, it has promoted cultural awareness across many state borders.

The Kon-Tiki2 Expedition combined science with adventure and challenge. Its organization was not simple, however, the outcome is of highest value, both from a professional scientific point of view, for the originator and sponsors of the expedition idea and for each and every project participant.

Kon-Tiki2 aimed to double-down on Thor Heyerdahl’s Kon-Tiki voyage (1947) by sailing two rafts from South America to Polynesia and then back. No one has done this in modern history. Kon-Tiki2 was an unparalleled voyage of survival, science and exploration. Although one of the strongest El Niño ever recorded stopped us from sailing all the way to South America, Kon-Tiki2 substantiates the ancient Pacific pathway for both Polynesians and South Americans. We know both cultures had rafts. Polynesians probably used their superior double hulled canoe for exploration and rafts for migrations. Kon-tiki2 showed how Polynesians could have sailed to South America and back, and how South Americans could have done the same in the opposite direction.

Continue reading ‘Kon-Tiki2 expedition 2015-2016: scientific cruise report’

Investigating controls on boron isotope ratios in shallow marine carbonates

The boron isotope-pH proxy has been widely used to reconstruct past ocean pH values. In both planktic foraminifera and corals, species-specific calibrations are required in order to reconstruct absolute values of pH, due to the prevalence of so-called vital effects — physiological modification of the primary environmental signals by the calcifying organisms. Shallow marine abiotic carbonate (e.g. ooids and cements) could conceivably avoid any such calibration requirement, and therefore provide a potentially useful archive for reconstructions in deep (pre-Cenozoic) time. However, shallow marine abiotic carbonates could also be affected by local shifts in pH caused by microbial photosynthesis and respiration, something that has up to now not been fully tested. In this study, we present boron isotope measurements from shallow modern marine carbonates, from the Bahama Bank and Belize to investigate the potential of using shallow water carbonates as pH archives, and to explore the role of microbial processes in driving nominally ‘abiogenic’ carbonate deposition. For Bahama bank samples, our boron-based pH estimates derived from a range of carbonate types (i.e. ooids, peloids, hardground cements, carbonate mud, stromatolitic micrite and calcified filament micrite) are higher than the estimated modern mean-annual seawater pH values for this region. Furthermore, the majority (73%) of our marine carbonate-based pH estimates fall out of the range of the estimated pre-industrial seawater pH values for this region. In shallow sediment cores, we did not observe a correlation between measured pore water pH and boron-derived pH estimates, suggesting boron isotope variability is a depositional rather than early diagenetic signal. For Belize reef cements, conversely, the pH estimates are lower than likely in situ seawater pH at the time of cement formation. This study indicates the potential for complications when using shallow marine non-skeletal carbonates as marine pH archives. In addition, variability in δ11B based pH estimates provides additional support for the idea that photosynthetic CO2 uptake plays a significant role in driving carbonate precipitation in a wide range of shallow water carbonates.

Continue reading ‘Investigating controls on boron isotope ratios in shallow marine carbonates’

Spatial and temporal controls on the inorganic carbon system of the Western Arctic Ocean

The Arctic Ocean plays a critical role in the global carbon cycle. It is believed to be particularly sensitive to the effects of climate change, is already undergoing dramatic changes, and is therefore important to study in that context. Most studies of the inorganic carbon system in the Western Arctic focus on hydrographic datasets from summer and/or fall (July-October), and do not consider the full response of the system to the timing of ice retreat, organic matter production and remineralization, and ice advance. Here we present the first dataset to investigate the spatial and temporal controls on the inorganic carbon system from early spring (pre-phytoplankton), late spring (initial phytoplankton bloom), summer (post-bloom), and fall in 2014. Our results suggest that the timing of ice retreat has important implications for the length of the phytoplankton growing season, and thus influences the magnitude of biological carbon cycling. We extend our analysis to include high-resolution temporal estimates of air-sea CO2 flux, and estimate a total annual CO2 uptake in the Chukchi Sea of ~7.7 Tg C. This is the first dataset to evaluate the importance of different seasonal observations within one year on the annual uptake of CO2 in the western Arctic Ocean. Our results show that extrapolations from one observational dataset result in large over- or underestimations of annual CO2 flux.

Continue reading ‘Spatial and temporal controls on the inorganic carbon system of the Western Arctic Ocean’

Development and application of foraminiferal carbonate system proxies to quantify ocean acidification in the California Current

The oceanic uptake of anthropogenic carbon has mitigated climate change, but has also resulted in a global average 0.1 decline in surface ocean pH over 20th century known as ocean acidification. The parallel reduction in carbonate ion concentration ([CO32-]) and the saturation state of seawater (Ω) has caused many major calcium carbonate-secreting organisms such as planktonic foraminifera to exhibit impaired calcification. We develop proxy calibrations and down core records that use calcification and geochemical characteristics of planktonic foraminifera as proxies for the marine carbonate system. This study focuses specifically on the surface ocean chemistry of the California Current Ecosystem (CCE), which has been identified as a region of rapidly progressing ocean acidification due to natural upwelling processes and the low buffering capacity of these waters. The calibration portion of this study uses marine sediments collected by the Santa Barbara Basin (SBB), California sediment-trapping program located in the central region of the CCE. We calibrate the relationships of Globigerina bulloides calcification intensity to [CO3 2-] and the B/Ca ratios of G. bulloides, Neogloboquadrina dutertrei and Neogloboquadrina incompta shells to Ω calcite using in situ measurements and model simulations of these independent variables. By applying these proxy methods to down core, our records from the SBB indicate a 20% reduction in foraminiferal calcification since ~1900, translating to a 35% decline in [CO 32-] in the CCE over this period. Our high-resolution calcification record also reveals a substantial interannual to decadal modulation of ocean acidification in the CCE related to the sign of Pacific Decadal Oscillation and El Niño Southern Oscillation. In the future we can expect these climatic modes to both enhance and moderate anthropogenic ocean acidification. Based on our historic record, we predict that if atmospheric CO2 reaches 540 ppm by the year 2100 as predicted by a conservative CO3 pathway, [CO32-] will experience a net reduction of 55%, resulting in at least a 30% reduction in calcification of planktonic foraminifera that will likely be mirrored by other adversely affected marine calcifiers.

Continue reading ‘Development and application of foraminiferal carbonate system proxies to quantify ocean acidification in the California Current’

The influence of CO2 enrichment on net photosynthesis of seagrass Zostera marina in a brackish water environment

Seagrasses are distributed across the globe and their communities may play key roles in the coastal ecosystems. Seagrass meadows are expected to benefit from the increased carbon availability which might be used in photosynthesis in a future high CO2 world. The main aim of this study was to examine the effect of elevated pCO2 on the net photosynthesis of seagrass Zostera marina in a brackish water environment. The short-term mesocosm experiments were conducted in Kõiguste Bay (northern part of Gulf of Riga, the Baltic Sea) in June–July 2013 and 2014. As the levels of pCO2 naturally range from ca. 150 μatm to well above 1000 μatm under summer conditions in Kõiguste Bay we chose to operate in mesocosms with the pCO2 levels of ca. 2000, ca. 1000, and ca. 200 μatm. Additionally, in 2014 the photosynthesis of Z. marina was measured outside of the mesocosm in the natural conditions. In the shallow coastal Baltic Sea seagrass Z. marina lives in a highly variable environment due to seasonality and rapid changes in meteorological conditions. This was demonstrated by the remarkable differences in water temperatures between experimental years of ca. 8°C. Thus, the current study also investigated the effect of elevated pCO2 in combination with short-term natural fluctuations of environmental factors, i.e., temperature and PAR on the photosynthesis of Z. marina. Our results show that elevated pCO2 alone did not enhance the photosynthesis of the seagrass. The photosynthetic response of Z. marina to CO2 enrichment was affected by changes in water temperature and light availability.

Continue reading ‘The influence of CO2 enrichment on net photosynthesis of seagrass Zostera marina in a brackish water environment’

Linking gene expression to productivity to unravel long- and short-term responses of seagrasses exposed to CO2 in volcanic vents

Ocean acidification is a major threat for marine life but seagrasses are expected to benefit from high CO2. In situ (long-term) and transplanted (short-term) plant incubations of the seagrass Cymodocea nodosa were performed near and away the influence of volcanic CO2 vents at Vulcano Island to test the hypothesis of beneficial effects of CO2 on plant productivity. We relate, for the first time, the expression of photosynthetic, antioxidant and metal detoxification-related genes to net plant productivity (NPP). Results revealed a consistent pattern between gene expression and productivity indicating water origin as the main source of variability. However, the hypothesised beneficial effect of high CO2 around vents was not supported. We observed a consistent long- and short-term pattern of gene down-regulation and 2.5-fold NPP decrease in plants incubated in water from the vents and a generalized up-regulation and NPP increase in plants from the vent site incubated with water from the Reference site. Contrastingly, NPP of specimens experimentally exposed to a CO2 range significantly correlated with CO2 availability. The down-regulation of metal-related genes in C. nodosa leaves exposed to water from the venting site suggests that other factors than heavy metals, may be at play at Vulcano confounding the CO2 effects.

Continue reading ‘Linking gene expression to productivity to unravel long- and short-term responses of seagrasses exposed to CO2 in volcanic vents’

Sensitivity of sea urchin fertilization to pH varies across a natural pH mosaic

In the coastal ocean, temporal fluctuations in pH vary dramatically across biogeographic ranges. How such spatial differences in pH variability regimes might shape ocean acidification resistance in marine species remains unknown. We assessed the pH sensitivity of the sea urchin Strongylocentrotus purpuratus in the context of ocean pH variability. Using unique male–female pairs, originating from three sites with similar mean pH but different variability and frequency of low pH (pHT ≤ 7.8) exposures, fertilization was tested across a range of pH (pHT 7.61–8.03) and sperm concentrations. High fertilization success was maintained at low pH via a slight right shift in the fertilization function across sperm concentration. This pH effect differed by site. Urchins from the site with the narrowest pH variability regime exhibited the greatest pH sensitivity. At this site, mechanistic fertilization dynamics models support a decrease in sperm–egg interaction rate with decreasing pH. The site differences in pH sensitivity build upon recent evidence of local pH adaptation in S. purpuratus and highlight the need to incorporate environmental variability in the study of global change biology.

Continue reading ‘Sensitivity of sea urchin fertilization to pH varies across a natural pH mosaic’

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Ocean acidification in the IPCC AR5 WG II

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