Archive for February, 2017

Ocean acidification: International research team reports ocean acidification spreading rapidly in Arctic Ocean in area and depth

Photo credit: Z. Gao & D. Qi

Photo credit: Z. Gao & D. Qi

Ocean acidification (OA) is spreading rapidly in the western Arctic Ocean in both area and depth, according to new interdisciplinary research reported in Nature Climate Change by a team of international collaborators, including University of Delaware professor Wei-Jun Cai.

The research shows that, between the 1990s and 2010, acidified waters expanded northward approximately 300 nautical miles from the Chukchi slope off the coast of northwestern Alaska to just below the North Pole. Also, the depth of acidified waters was found to have increased, from approximately 325 feet to over 800 feet (or from 100 to 250 meters).

“The Arctic Ocean is the first ocean where we see such a rapid and large-scale increase in acidification, at least twice as fast as that observed in the Pacific or Atlantic oceans,” said Cai, the U.S. lead principal investigator on the project and Mary A.S. Lighthipe Professor of Earth, Ocean, and Environment at UD.

Continue reading ‘Ocean acidification: International research team reports ocean acidification spreading rapidly in Arctic Ocean in area and depth’

Entering the Anthropocene: How ocean acidification and warmer temperatures affect the symbiotic sea anemone Exaiptasia pallida

Here I report the effects of long-term elevated CO2 combined with two subsequent elevated temperature intervals on the model symbiotic anemone Exaiptasia pallida. A central goal of this thesis was to investigate how altered CO2 and temperature affect the symbiotic relationship while this anemone hosted three different strains of endosymbiotic dinoflagellates (Symbiodinium minutum, Symbiodinium A4a, and Symbiodinium A4b). Exposure to elevated CO2 (930μatm) alone for 42 days led to no significant changes in either the anemone or the algae physiological response, with the exception of some separation between the photosynthesis to respiration ratio of S. A4a and S. A4b control and treatment animals. Exposure to both elevated CO2 (930μatm) and a moderate  elevation in temperature (29°C) for 49 days led to a significant increase in the net maximal photosynthesis (normalized to algal cell density) between the treatment and controls of all three  holobionts. Exposure to both elevated CO2 (930μatm) and an even higher temperature (33°C) for up to 20 days led to a significant decrease in photobiology and algal cell density, along with visible bleaching in the S. minutum holobiont. All three holobionts displayed a significant decrease in the photosynthesis to respiration ratio, thereby providing evidence for temperature having a greater impact on the phototrophic response of these anemones. However, anemones harboring the two A4 Symbiodinium did not show as large of a negative response in photosystem II  photochemistry when compared to anemones with S. minutum. The high temperature treatment also resulted in juvenile mortality in all three holobionts, with the greatest mortality seen in the S. minutum holobiont. The differential response to both elevated CO2 and elevated temperature between the three holobionts highlights the thermal sensitivity of the S. minutum symbiosis, and the thermal tolerance of the S. A4 holobionts. Thermal tolerance may enable these anemones to survive and thrive in future climate change conditions, while the effects of higher CO2 appear to be more neutral.

Continue reading ‘Entering the Anthropocene: How ocean acidification and warmer temperatures affect the symbiotic sea anemone Exaiptasia pallida’

The effects of salinity and pH on fertilization, early development, and hatching in the crown-of-thorns seastar

Understanding the influence of environmental factors on the development and dispersal of crown-of-thorns seastars is critical to predicting when and where outbreaks of these coral-eating seastars will occur. Outbreaks of crown-of-thorns seastars are hypothesized to be driven by terrestrial runoff events that increase nutrients and the phytoplankton food for the larvae. In addition to increasing larval food supply, terrestrial runoff may also reduce salinity in the waters where seastars develop. We investigated the effects of reduced salinity on the fertilization and early development of seastars. We also tested the interactive effects of reduced salinity and reduced pH on the hatching of crown-of-thorns seastars. Overall, we found that reduced salinity has strong negative effects on fertilization and early development, as shown in other echinoderm species. We also found that reduced salinity delays hatching, but that reduced pH, in isolation or in combination with lower salinity, had no detectable effects on this developmental milestone. Models that assess the positive effects of terrestrial runoff on the development of crown-of-thorns seastars should also consider the strong negative effects of lower salinity on early development including lower levels of fertilization, increased frequency of abnormal development, and delayed time to hatching.

Continue reading ‘The effects of salinity and pH on fertilization, early development, and hatching in the crown-of-thorns seastar’

Growing mussels and giant kelp in San Pedro at the first offshore shellfish ranch in federal waters

Once home to the nation’s busiest tuna canneries and a Japanese American fishing village, Terminal Island is decades away from the thriving seafood industry of its past. But thanks to Catalina Sea Ranch, a pioneering research and business venture, that stretch of land between San Pedro and Long Beach is now at the forefront of sustainable aquaculture in the U.S. While the company’s offices and research facilities are housed in a sprawling historic warehouse — part of the Port of L.A.’s new AltaSea marine research campus — the real action is taking place roughly six miles off shore. There, just below the ocean’s surface, is a 100-acre shellfish “ranch” — the first offshore aquaculture facility in federal waters. And while Catalina Sea Ranch is currently farming mussels, they are researching how also growing giant kelp could help reduce greenhouse gas emissions in a significant way.

The ranch is currently growing an initial pilot crop of around 30,000 lbs of mussels that will soon be harvested from dozens of specially designed ropes. Catalina Sea Ranch is also developing and utilizing innovative marine technologies — including remotely operated vehicles (ROVs) with underwater cameras and a network of sensors — to monitor the crop and collect environmental data to ensure a minimal to zero impact on the local ecosystem. The Mediterranean mussels grown by Catalina Sea Ranch are ranked as a “best choice” for sustainable seafood options by organizations such as the Seafood Watch Program, as the filter-feeding mollusks require no supplemental feed since upwelling from the deep ocean provide a steady supply of nutrients. The company is also researching how best to grow other low-impact — and highly profitable — shellfish such as scallops and possibly oysters. And while the company aims to expand the ranch to 1000 acres and 20 million lbs annually — helping to offset the high percentage of seafood that is imported to the U.S. — Catalina Sea Ranch also has its sights set on expanding its research and design efforts to growing giant kelp, which can help offset greenhouse gas emissions in a variety of ways.

Continue reading ‘Growing mussels and giant kelp in San Pedro at the first offshore shellfish ranch in federal waters’

Ocean acidification in Southeast, tribal network seeks regional impact (audio and text)

Wrangell and fourteen other tribes have participated in the Southeast Alaska Tribal Ocean Research program, collecting clams and cockles for paralytic shellfish poison testing. The Sitka Tribe of Alaska heads the initiative and now wants to get a baseline for ocean acidification in the region.

Sitka tribe Environmental Specialist Esther Kennedy explains that monitoring ocean acidification in near-shore environments has been quite difficult until recently.

“Most of the research on OA to date has been done in the open ocean,” said Kennedy.

These environments naturally have wide swings in ocean chemistry due to stream and river volume changes, storms and droughts, and proximity to the open ocean.

“I suspect that Sitka Sound will look a lot more like the Gulf of Alaska than it will look like Wrangell with its huge fresh water input from the Stikine,” Kennedy noted. “One of the interesting things will be can we start to see say gradience and effects of ocean acidification as we move from the outer coast to the even more coastal environments.”

Continue reading ‘Ocean acidification in Southeast, tribal network seeks regional impact (audio and text)’

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’

Understanding feedbacks between ocean acidification and coral reef metabolism

Biogeochemical feedbacks from benthic metabolism have been hypothesized as a potential mechanism to buffer some effects of ocean acidification on coral reefs. The article in JGR-Oceans by DeCarlo et al. demonstrates the importance of benthic community health on this feedback from Dongsha Atoll in the South China Sea.

Continue reading ‘Understanding feedbacks between ocean acidification and coral reef metabolism’

BIOACID Science Portrait – Maria Moreno de Castro: “A data detective tracking uncertainties”

Maria Moreno de Castro, modeler at Helmholtz-Zentrum Geesthacht (HZG), became a scientist because she likes to solve mysteries. Just like a detective, she tries to track uncertainties in scientific findings. “Our daily life is full of uncertainties. In science it’s the same: There are many outcomes, any solutions, many responses that we are not certain and we don’t know. We have to deal with this uncertainty, we have to understand it and know the origins.”

Maria Moreno used model calculations to get a grip on these uncertainties. By using mathematical approaches, she calculates thresholds below which variabilities will not escalate and mask the effect an experiment tries to explore. “Particularly in ecology of ocean acidification the answer is not black or white. Always there will be a grey area”, the young scientist explains. “This is also important when we communicate to policy makers, because it is really not possible.to give just a value to the effect of ocean acidification, but possible scenarios with their probabilities. This is highly difficult, and the best we can do from science.”

Further information.

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’

Acidification and warming affect prominent bacteria in two seasonal phytoplankton bloom mesocosms

In contrast to clear stimulatory effects of rising temperature, recent studies of the effects of CO2 on planktonic bacteria have reported conflicting results. To better understand the potential impact of predicted climate scenarios on the development and performance of bacterial communities, we performed bifactorial mesocosm experiments (pCO2 and temperature) with Baltic Sea water, during a diatom dominated bloom in autumn and a mixed phytoplankton bloom in summer. The development of bacterial community composition (BCC) followed well-known algal bloom dynamics. A principal coordinate analysis (PCoA) of bacterial OTUs (operational taxonomic units) revealed that phytoplankton succession and temperature were the major variables structuring the bacterial community whereas the impact of pCO2 was weak. Prokaryotic abundance and carbon production, and organic matter concentration and composition were partly affected by temperature but not by increased pCO2. However, pCO2 did have significant and potentially direct effects on the relative abundance of several dominant OTUs; in some cases, these effects were accompanied by an antagonistic impact of temperature. Our results suggest the necessity of high-resolution BCC analyses and statistical analyses at the OTU level to detect the strong impact of CO2 on specific bacterial groups, which in turn might also influence specific organic matter degradation processes.

Continue reading ‘Acidification and warming affect prominent bacteria in two seasonal phytoplankton bloom mesocosms’


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