Archive Page 157

OA-ICC bibliographic database updated

Published 2 September 2022 Science Closed

An updated version of the OA-ICC bibliographic database is available online.

The database currently contains 9,740 references and includes citations, abstracts and assigned keywords. Updates are made every month.

The database is available as a group on Zotero. Subscribe online or, for a better user experience, download the Zotero desktop application and sync with the group OA-ICC in Zotero. Please see the “User instructions” for further details.

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Acidification, deoxygenation, and nutrient and biomass declines in a warming Mediterranean Sea (update)

Published 2 September 2022 Science Closed
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The projected warming, nutrient decline, changes in net primary production, deoxygenation and acidification of the global ocean will affect marine ecosystems during the 21st century. Here, the climate change-related impacts on the marine ecosystems of the Mediterranean Sea in the middle and at the end of the 21st century are assessed using high-resolution projections of the physical and biogeochemical state of the basin under Representative Concentration Pathways (RCPs) 4.5 and 8.5. In both scenarios, the analysis shows changes in the dissolved nutrient contents of the euphotic and intermediate layers of the basin, net primary production, phytoplankton respiration and carbon stock (including phytoplankton, zooplankton, bacterial biomass and particulate organic matter). The projections also show uniform surface and subsurface reductions in the oxygen concentration driven by the warming of the water column and by the increase in ecosystem respiration as well as an acidification signal in the upper water column linked to the increase in the dissolved inorganic carbon content of the water column due to CO2 absorption from the atmosphere and the increase in respiration. The projected changes are stronger in the RCP8.5 (worst-case) scenario and, in particular, in the eastern Mediterranean due to the limited influence of the exchanges in the Strait of Gibraltar in that part of the basin. On the other hand, analysis of the projections under the RCP4.5 emission scenario shows a tendency to recover the values observed at the beginning of the 21st century for several biogeochemical variables in the second half of the period. This result supports the idea – possibly based on the existence in a system such as the Mediterranean Sea of a certain buffer capacity and renewal rate – that the implementation of policies for reducing CO2 emission could indeed be effective and could contribute to the foundation of ocean sustainability science and policies.

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Coastal freshening drives acidification state in Greenland fjords

Published 2 September 2022 Science Closed
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Greenland’s fjords and coastal waters are highly productive and sustain important fisheries. However, retreating glaciers and increasing meltwater are changing fjord circulation and biogeochemistry, which may threaten future productivity. The freshening of Greenland fjords caused by unprecedented melting of the Greenland Ice Sheet may alter carbonate chemistry in coastal waters, influencing CO 2 uptake and causing biological consequences from acidification. However, few studies to date explore the current acidification state in Greenland coastal waters. Here we present the first-ever large-scale measurements of carbonate system parameters in 16 Greenlandic fjords and seek to identify the drivers of acidification state in these freshening ecosystems. Aragonite saturation state (Ω), a proxy for ocean acidification, was calculated from dissolved inorganic carbon (DIC) and total alkalinity from fjords along the east and west coast of Greenland spanning 68-75 °N. Aragonite saturation was primarily > 1 in the surface mixed layer. However, undersaturated—or corrosive––conditions (Ω < 1) were observed on both coasts (west: Ω = 0.28-3.11, east: Ω = 0.70-3.07), albeit at different depths. West Greenland fjords were largely corrosive at depth while undersaturation in East Greenland fjords was only observed in surface waters. This reflects a difference in the coastal boundary conditions and mechanisms driving acidification state. We suggest that advection of Sub Polar Mode Water and accumulation of DIC from organic matter decomposition drive corrosive conditions in the West, while freshwater alkalinity dilution drives acidification in the East. The presence of marine terminating glaciers also impacted local acidification states by influencing fjord circulation: upwelling driven by subglacial discharge brought corrosive bottom waters to shallower depths. Meanwhile, discharge from land terminating glaciers strengthened stratification and diluted alkalinity. Regardless of the drivers in each system, increasing freshwater discharge will likely lower carbonate saturation states and impact biotic and abiotic carbon uptake in the future.

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Impact of intermittent convection in the northwestern Mediterranean Sea on oxygen content, nutrients and the carbonate system

Published 2 September 2022 Science Closed
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Abstract

Using Argo profiling floats, cruises and mooring data, we reconstructed the dissolved oxygen (O2) dynamics in the Gulf of Lion and the Ligurian Sea, with a focus on the intermediate waters. By applying the CANYON-MED neural network-based method on the large network of O2-equipped Argo floats we derived nutrients and carbonate system variables in the Gulf of Lion and the Ligurian Sea at different depths in the water column and derived trends over the 2012-2020 period. In these waters, the O2 minimum is strongly affected by the intermittent convection process, and the two areas show dissimilar responses to the mixing events. In the absence of deep convection events, the O2-depleted layer tends to spread vertically and intensify even more so in the Ligurian than in the Gulf of Lion. In both areas, over the 2012-2020 period, nutrients increase overall in deep layers, with a concomitant impact on nutrient molar ratios tending towards an increase in P-limitation. Acidification estimates derived in different layers of the water column show an overall increase in dissolved inorganic carbon and a concurrent pH decrease. These trends were strongly affected by convection events slowing down the overall acidification trend.

Key Points

  • In the absence of deep convection events, the O2-depleted layer spreads vertically and intensifies more in the Ligurian than Gulf of Lion.
  • Nutrients increase in deep and to a lesser extent in intermediate waters with a decoupling between nitrate and phosphate trends.
  • Dissolved inorganic carbon increases in intermediate and deep waters with a concurrent pH decrease over the period of study, 2012-2020.
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5th International Symposium for the Ocean in High CO2 World: plenary speeches streamed live

Published 2 September 2022 Events , Meetings Closed

The 5th International Symposium on the Ocean in High CO2 World will take place from the 13 -16 September in Lima, Peru. The plenaries will be available to stream live on the High CO2 YouTube channel. The schedule for the plenary speakers is as follows:

Tuesday 13 September

  • 13:00-13:50 UTC – Samantha Siedlicki
  • 13:50-14:40 UTC – Cristian Vargas

Wednesday 14 September

  • 13:00-13:50 UTC – Steve Widdicombe
  • 13:50-14:40 UTC – Dalin Shi

Thursday 15 September

  • 13:00-13:50 UTC – Jessie Turner
  • 13:50-14:40 UTC – Frédéric Gazeau

Friday 16 September

  • 13:00-13:50 UTC – Sarah Cooley
  • 13:50-14:40 UTC – Guillermo Diaz-Pulido
  • 21:00-22:00 UTC – Dimitri Gutiérrez

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Building resilience to ocean acidification from sea to shell

Published 2 September 2022 Web sites and blogs Closed
Oyster operations images provided by Mook Sea Farm

Mook Sea Farm, located on the Damariscotta River in midcoast Maine, produces over 120 million juvenile oysters each year. The farm’s water comes directly from the river and changes in environmental conditions affect hatchery production. During the 2008-2009 season, Mook experienced decreased larval production due to high levels of precipitation decreasing the carbon dioxide (CO2) buffering capacity in hatchery water. This short-term acidification event negatively impacted production of larval oysters.

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Calcification response of planktic foraminifera to environmental change in the western Mediterranean Sea during the industrial era

Published 1 September 2022 Science Closed
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The aim of this work is to investigate the variability of planktic foraminifera calcification in the northwestern Mediterranean Sea on seasonal, interannual and pre-industrial Holocene time scales. This study is based on data from a 12-year-long sediment trap record retrieved in the in the Gulf of Lions and seabed sediment samples from the Gulf of Lions and the promontory of Menorca. Three different planktic foraminifera species were selected based on their different ecology and abundance: Globigerina bulloides, Neogloboquadrina incompta, and Globorotalia truncatulinoides. A total of 273 samples were weighted in both sediment trap and seabed samples. As the traditionally used sieve fractions method is considered unreliable because of the effect of morphometric parameters on the foraminifera weight, we measured area and diameter to constrain the effect of these parameters. The results of our study show substantial different seasonal calcification patterns across species: G. bulloides showed a slight calcification increase during the high productivity period, while both N. incompta and G. truncatulinoides display a higher calcification during the low productivity period. The comparison of these patterns with environmental parameters revealed that Optimum Growth Conditions temperature and carbonate system parameters are the most likely to influence seasonal calcification in the Gulf of Lions. Interannual analysis suggest that both G. bulloides and N. incompta slightly reduced their calcification between 1994 and 2005, while G. truncatulinoides exhibited a constant and pronounced increase in its calcification that translated in an increase of 20 % of its shell weight for the 400–500 µm narrow size class. While our data suggest that carbonate system parameters are the most likely environmental parameter driving foraminifera calcification changes over the years.

Finally, comparison between sediment trap data and seabed sediments allowed us to assess the changes of planktic foraminifera calcification during the late Holocene, including the preindustrial era. Several lines of evidence strongly indicate that selective dissolution did not bias the results in any of our data sets. Our results showed a clear calcification reduction between pre-industrial Holocene and recent data with G. truncatulinoides experiencing the largest calcification decrease (32–40 %) followed by N. incompta (20–27 %) and G. bulloides (18–24 %). Overall, our results provide evidence of clear reduction in planktic foraminifera calcification in the Mediterranean most likely associated with ongoing ocean acidification and consistent with previous observations in other settings of the world’s oceans.

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Planktonic foraminifera organic carbon isotopes as archives of upper ocean carbon cycling

Published 1 September 2022 Science Closed
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The carbon cycle is a key regulator of Earth’s climate. On geological time-scales, our understanding of particulate organic matter (POM), an important upper ocean carbon pool that fuels ecosystems and an integrated part of the carbon cycle, is limited. Here we investigate the relationship of planktonic foraminifera-bound organic carbon isotopes (δ13Corg-pforam) with δ13Corg of POM (δ13Corg-POM). We compare δ13Corg-pforam of several planktonic foraminifera species from plankton nets and recent sediment cores with δ13Corg-POM on a N-S Atlantic Ocean transect. Our results indicate that δ13Corg-pforam of planktonic foraminifera are remarkably similar to δ13Corg-POM. Application of our method on a glacial sample furthermore provided a δ13Corg-pforam value similar to glacial δ13Corg-POM predictions. We thus show that δ13Corg-pforam is a promising proxy to reconstruct environmental conditions in the upper ocean, providing a route to isolate past variations in δ13Corg-POM and better understanding of the evolution of the carbon cycle over geological time-scales.

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Effects of ocean acidification and hypoxia on stress and growth hormone responses in juvenile blue rockfish (Sebastes mystinus) (video)

Published 1 September 2022 Presentations , Resources Closed

Hannah Bruzzio

“Effects of Ocean Acidification and Hypoxia on Stress and Growth Hormone Responses in Juvenile Blue Rockfish (Sebastes mystinus)”

Moss Landing Marine Labs Thesis Defenses

August 30th, 2022

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Stability of coral reef islands and associated legal maritime zones in a changing ocean

Published 31 August 2022 Science Closed
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Coral reef islands can support large legal maritime zones (i.e., ocean spaces where States have rights and responsibilities) and are of international and geopolitical importance. This review focuses on low-lying coral reef islands supplied with sediments derived from skeletons and shells of calcifying organisms. For coral islands, the outer ‘low-water line’ of the reef can be used as the legal ‘baseline’ to establish maritime zones. Coral islands and the reefs that support them are experiencing the effects of rising and warming seas, increased storminess and ocean acidification. Coral reefs, their islands and associated maritime zones support millions of people, including those in Small Island Developing States (SIDS). SIDS communities are arguably the least responsible for climate change but are at the forefront of its impacts so ensuring their continued wellbeing is a global responsibility. Securing the future of coral reefs and islands is dependent on reducing global climate threats and emissions, improving local management, and investing in restoration and adaption research. It is uncertain if coral islands will persist into the future, and on what timelines. This raises questions such as, where coral islands support maritime zones, what are the legal implications of island instability or loss? This review focuses on the bio-physical interactions of coral islands and associated reefs in the face of changing climates, and implications for legal maritime zones and SIDS.

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Coastal carbonate system variability along an active lava–seawater interface

Published 31 August 2022 Science Closed
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Lava flows from the 2021 volcanic eruption in La Palma, Canary Islands, reached the shoreline during three events on September 28th, November 10th, and November 22nd, strongly affecting the seawater properties as they interacted with the seawater. The evolution of surface and water column physicochemical properties (temperature, salinity, carbonate system variables, and dissolved oxygen) was characterized during 13 visits to the frontal zone of the newly formed deltas. A large volume of hot (50°C measured on November 12th) and high salinity seawater promoted pH values in the frontal zone of 7.0 with important decreases in alkalinity, ΔAT, and total dissolved inorganic carbon, ΔCT, that reached 566 and 272 µmol kg−1, respectively. The addition of acids generated during the lava–seawater interaction (44.4 mmol), together with those used in the titration of carbonate alkalinity (796 ± 72 mmol) plus acids used in metal dissolution (21 mmol), was estimated with an average added proton concentration of 0.31 µmol kg−1 of seawater in the affected 2.7 · 106 m3 for November 12th. During this event, the decrease in pH and the increase in temperature increased the partial pressure of CO2, outgassing 2 tons of CO2, 40 times the daily emitted CO2 for this area under non-eruptive conditions. One month after the eruption, the studied physicochemical properties of the seawater close to the new deltas returned to the usual non-eruptive normal values, which include the presence of low salinity, low pH, and high CO2 gas diffusive emissions through submarine groundwater discharges observed between the formed deltas. The new mineral-rich deltas and the increase in solubility due to the low pH conditions contributed to the recovery of the affected area.

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Effect of CO2 driven ocean acidification on the mud crab Scylla serrata instars

Published 31 August 2022 Science Closed
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Graphical abstract

Highlights

  • Ocean acidification (OA) affected feed intake and growth of Scylla serrata.
  • OA reduced minerals content in S. serrata.
  • OA disturbs the chitin production and alkaline phosphatase activity in S.serrata.
  • OA increased the antioxidants and metabolic enzymes in S. serrata.

Abstract

The decreasing ocean pH seems to adversely affect marine organisms, including crustaceans, which leads to potential threats to seafood safety. The present investigation evaluated the effect of seawater acidification on the edible marine mud crab Scylla serrata instars. The experimental setup was designed using a multi-cell cage based system assembled with 20 pre holed PVC pipes containing 20 individual crabs to avoid cannibalism. The crab instars were exposed to CO2 driven acidified seawater at pH 7.8 (IPCC forecast pH at the end of the 21st century), 7.6, 7.4, 7.2, and 7.0 for 60 days. The crabs reared in seawater without acidification at pH 8.2 served as control. The present study revealed a notable decrease in survival, feed intake, growth, molting, tissue biochemical constituents, minerals, chitin, and alkaline phosphatase in S. serrata instar reared in acidified seawater, denotes the adverse effect of seawater acidification on crabs. The significant elevations in antioxidants, lipid peroxidation, and metabolic enzymes in all acidified seawater compared to ambient pH indicates the physiological stress of the crabs’ instars. The changes in the metabolic enzymes reveal the metabolism of protein and glucose for additional energy required by the crabs to tolerate the acidic stress. Hence, the present study provides insight into the seawater acidification can adversely affect the crab S. serrata.

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Assistant Professor, Biology, Global Change Ecology

Published 31 August 2022 Jobs Closed

Job no: 517800
Work type: Instructional Faculty – Tenured/Tenure-Track
Location: San Francisco

Applications close: Open Until Filled

San Francisco State University, Department of Biology invites applications for a tenure-track Assistant Professor position in Global Change Ecology to begin August 2023. We seek applicants conducting research in Global Change Ecology, broadly defined (e.g., climate change, biodiversity loss, land use change, invasive species). We welcome scientists developing an externally funded research program towards a comprehensive and holistic understanding of the effects and consequences of global change on ecological systems, biosphere-atmosphere interactions, and coupled natural-human systems across temporal and spatial scales. Research foci may include nature-based adaptation solutions to reduce the causes and impacts of global change (e.g., sea level rise, carbon emissions, fire, ocean acidification, nutrient pollution, hypoxia, etc.). We are open to all research approaches, including experimental field-based research, computational or mathematical modeling, and/or machine learning within the context of natural communities or at the urban/natural ecosystem interface. The successful candidate may also address how social justice and incorporating traditional ecological knowledge fits into understanding and addressing global change through research or outreach. We are especially interested in qualified candidates who can contribute to the excellence and diversity of the SFSU academic community by working on important and relevant research areas, whose teaching and research engages our diverse student body and improves their academic success, and whose service is meaningful to our institution as well as the broader community.

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Responsibilities

The position requires both graduate and undergraduate teaching in biology. Curricular contributions could include Introductory Biology, Climate change, Evolution, Ecology, Research Design and Data Analysis, and specialty courses in the candidate’s area of research focus at the undergraduate and graduate level. In addition, the successful candidate will be required to engage, mentor, and advise undergraduate and master’s students in directed research. The successful candidate is also expected to continue an active, externally-funded research program in their area of expertise, and to participate in committee and service assignments at the department and university level, and to their professional community.

Qualifications

Required

  • Ph.D. or equivalent doctoral degree and post-doctoral experience in a biology or biology-related field are required. 
  • Record of scientific and mentorship accomplishments in biology and global change ecology. 
  • Evidence of working and communicating effectively with colleagues and students.

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Application Procedure

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How is climate change affecting ocean waters and ecosystems?

Published 31 August 2022 Web sites and blogs Closed
Ducklow at a glacial ice cave near Palmer Station, Antarctica, 2006. The glacier collapsed and wasted away a year or two later. (Courtesy Hugh Ducklow)

Biological oceanographer Hugh Ducklow studies the marine food web, and how it interacts with the physical properties of the oceans. Much of his work is through the U.S. Long Term Ecological Research Program (LTER), in which researchers have for decades investigated trends across 28 land and marine regions in the United States, along with a few sites elsewhere. In addition to the open ocean, studies encompass deserts, coasts, rivers, forests and grasslands. From 2012 to 2018, while based at Columbia University’s Lamont-Doherty Earth Observatory, Ducklow led the Palmer Station LTER site, the base for yearly cruises through 800 kilometers of icy waters off the Antarctic Peninsula.

To mark the 40th anniversary of the LTER program, researchers just published a series of articles on how climate change is affecting their sites. Ducklow led the section on open-ocean environments, which in addition to Antarctica spans waters off Alaska, California and the U.S. Northeast. We spoke with him about the work, his and colleagues’ observations, and prospects for the future.

Why should we care about what climate change does to the oceans?

Besides the fact that seafood constitutes the major protein source for about 3 billion people, the ocean soaks up a major amount of excess heat and human-generated carbon dioxide. Around 90 percent of all the excess heat produced by the greenhouse effect since the Industrial Revolution is in the ocean. The global ocean has also taken up about one quarter to one third of our carbon dioxide emissions. Both these processes keep air temperatures cooler than they would be otherwise. But they both come with costs. The ocean is warming as a result of added heat. The human-caused warming signal is even detectable in the deep Southern Ocean. Enhanced carbon dioxide uptake is causing ocean acidification. The ecological consequences of warming and acidification are just beginning to be understood, and the future capacity to continue to store heat and CO2 is not certain.

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Changing tides: how does ocean acidification affect marine life?

Published 31 August 2022 Web sites and blogs Closed

Despite how the ocean has influenced the natural world throughout history, human-triggered global warming is now changing ocean chemistry through a process called ocean acidification. Described by some researchers as “the other CO2 problem”, this phenomenon refers to the reduction in the pH of seawater over time – a change that comes with negative impacts on life above and below the waves. How does ocean acidification affect marine life and humans and what can we do to mitigate its impact?

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With its powerful tides and vast expanses that stretch into the horizon, the ocean captivates us. It is the cradle of early life – over billions of years our oceans have witnessed the evolution of simple cellular organisms to the wonderfully complex communities we see today. Whether we are standing with our feet in the surf or landlocked thousands of miles from the coast, we are surrounded by the ocean’s influence. By distributing heat, sequestering carbon, and storing solar radiation, it drives weather and climate across the globe. 

What is Ocean Acidification?

Ocean acidification refers to a decrease in the pH of seawater due to increased levels of carbon dioxide (CO2) in the atmosphere. Our oceans are carbon sinks – think of them as sponges that soak up excess carbon from the atmosphere.

By natural processes, CO2 absorbed by the ocean reacts with seawater to create carbonic acid, a weak acid that breaks apart into ions of different charges (imagine ions as Lego pieces that make up a larger structure– in this case,  carbonic acid). These include hydrogen ions and bicarbonate ions. The latter disassociates further to produce additional ions of hydrogen and carbonate. Animals like corals, shellfish, oysters, and urchins  –collectively referred to as calcifiers – use carbonate to build their shells and skeletons.

How does this process change when more CO2 is added to the mix? Since the industrial revolution, the amount of CO2 in the atmosphere has risen nearly 50%, jumping up to nearly 420 parts per million. Our seas currently soak up more than a quarter of the CO2 emitted from human activity. More CO2 in the ocean means more carbonic acid is produced, resulting in extra hydrogen and bicarbonate ions in seawater. pH is determined by the number of free hydrogen ions in a solution; the more they are, the lower the pH (and the more acidic the water). Additional CO2 in the water also leads to a decrease in the bioavailability of carbonate, making it harder for calcifiers to build their shells. 

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Modeling the sea-surface pCO2 of the central Bay of Bengal region using machine learning algorithms

Published 30 August 2022 Science Closed
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Highlights

  • Performance of MLR, ANN, and XGboost for emulating sea-surface pCO2 is evaluated.
  • XGBoost outperforms MLR and ANN in reproducing sea-surface pCO2.
  • The pCO2 reproducibility using satellite-derived SST and SSS is best using XGBoost.
  • The central BoB has been warming at a rate of 0.0175°C per year during 2010–2019.
  • The sea-surface pCO2 decreases at a rate of −0.4852 μatm per year in the BoB.

Abstract

The present study explores the capabilities of advanced machine learning algorithms in predicting the sea-surface pCO2 (partial pressure of carbon dioxide) in the open oceans of the Bay of Bengal (BoB). We collect the available observations (outside EEZ (Exclusive Economic Zone)) from the cruise tracks and the mooring stations. Due to the paucity of data in the BoB, we attempt to predict pCO2 based on the Sea Surface Temperature (SST) and the Sea Surface Salinity (SSS). Comparing the MLR, the ANN, and the XGBoost algorithm against a common dataset reveals that the XGBoost performs the best for predicting the sea-surface pCO2 in the BoB. Using the satellite-derived SST and SSS, we predict the sea-surface pCO2 using the XGBoost model and compare the same with the in-situ observations. The model performs satisfactorily, having a correlation of 0.75 and the RMSE of ±12.23μatm. Further using this model, we emulate the monthly variations in the sea-surface pCO2 for the central BoB between 2010-2019. Using the satellite data, we show that the central BoB is warming at a rate of 0.0175 °C per year, whereas the SSS decreases at a rate of -0.0088 PSU per year. The modeled pCO2 shows a declination at a rate of −0.4852 μatm per year. We perform sensitivity experiments to find that the variations in SST and SSS contribute ≈ 41% and ≈ 37% to the declining trends of the pCO2 for the last decade. Seasonal analysis shows that the pre-monsoon season has the highest rate of decrease of the sea-surface pCO2.

Continue reading ‘Modeling the sea-surface pCO2 of the central Bay of Bengal region using machine learning algorithms’

Geochemical significance of Acropora death assemblages in the northern South China Sea: implications for environmental reconstruction using branching corals

Published 30 August 2022 Science Closed
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Highlights

  • Acropora-derived SST reconstruction using Sr/Ca has registered SST shifts around 4–5 ka BP and the modern warming.
  • The universal Li/Mg-SST calibration tends to underestimate the SST reconstruction.
  • Reduced pHcf is found for the post-industrial corals compared to the ancient corals.
  • Coral DICcf exhibits a progressive decrease since the mid-Holocene.
  • Skeletal δ13C is intrinsically linked to the coral CF carbonate chemistry.

Abstract

The geochemistry preserved in coral skeletons provides access to pre-instrumental records of environmental changes. While a variety of proxies have been established for coral paleoclimatology, their applications to the use of Acropora to generate longer-term reconstructions have been studied less. Here, we examine the geochemical proxies (i.e., Sr/Ca, Li/Mg, δ18O, δ13C, δ11B, and B/Ca) of dead Acropora assemblages collected from a fringing reef off Hainan Island in the northern South China Sea. These samples have been precisely dated using Usingle bondTh isotopes and record reef development episodes since the mid-Holocene, allowing us to assess their potential as paleoclimate archives. The sea surface temperature (SST) trend reconstructed by Sr/Ca and Li/Mg exhibits better consistency with each other, and they have recorded the SST shifts around 5–4 ka BP and the subdued variability during the Medieval Climate Anomaly (MCA), whereas the δ18O-SST record exhibits less clear variations over the past 7000 years. However, the universal Li/Mg-SST calibration tends to underestimate the SST reconstruction from tropical corals, highlighting the importance of using a site- and species-specific calibration of the Li/Mg-SST. Boron systematics are used to reconstruct the carbonate chemistry of coral calcifying fluid (CF), which reveals significant differences between the ancient and modern corals. The pH of the coral CF (pHcf) is significantly lower in the modern Acropora compared to the ancient corals, with a mean difference of ~0.08 pH, corroborating the pronounced influence of ocean acidification on the coral CF chemistry. The dissolved inorganic carbon of the coral CF (DICcf) is also lower for modern Acropora, and this decreasing trend seems to have persisted over the past 7000 years. In addition, the skeletal δ13C is closely related to the CF carbonate chemistry, highlighting the intrinsic relationship between the coral internal carbon pool used for calcification and the up-regulation of the pHcf.

Continue reading ‘Geochemical significance of Acropora death assemblages in the northern South China Sea: implications for environmental reconstruction using branching corals’

Ocean acidification but not nutrient enrichment reduces grazing and alters diet preference in Littorina littorea

Published 30 August 2022 Science Closed
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Ocean acidification and eutrophication have direct, positive effects on the growth of many marine macroalgae, potentially resulting in macroalgal blooms and shifts in ecosystem structure and function. Enhanced growth of macroalgae, however, may be controlled by the presence of grazers. While grazing under ocean acidification and eutrophication conditions has variable responses, there is evidence of these factors indirectly increasing consumption. We tested whether a common marine herbivorous snail, Littorina littorea, would increase consumption rates of macroalgae (Ulva and Fucus) under ocean acidification (increased pCO2) and/or eutrophication conditions, via feeding trials on live and reconstituted algal thalli. We found that increased pCO2 resulted in reduced grazing rates on live thalli, with snails feeding almost exclusively on Ulva. However, eutrophication did not impact consumption rates of live tissues. In addition, similarity in consumption of reconstituted Ulva and Fucus tissues across all treatments indicated that physical characteristics of algal tissues, rather than tissue chemistry, may drive dietary shifts in a changing climate. In this system, decreased consumption, coupled with increased growth of macroalgae, may ultimately enhance algal growth and spread.

Continue reading ‘Ocean acidification but not nutrient enrichment reduces grazing and alters diet preference in Littorina littorea‘

OA-ICC booth at the Virtual Ocean Pavilion on the Road to COP27

Published 30 August 2022 Educational Materials , Events , Presentations Closed

The OA-ICC booth at the Virtual Ocean Pavilion for COP27 opened this week for Africa Climate Week (ACW), being held from 29 August-2 September 2022 in Gabon. Come visit to learn more about OA-ICC news, activities, and resources.

To visit the booth, explore materials from other Virtual Ocean Pavilion exhibitors, and view the schedule of live events, register for an account at the link. The booth and the Virtual Ocean Pavilion will be viewable through the end of COP27.

The Virtual Ocean Pavilion will host two live events this week in the Pavilion Virtual Auditorium. Please review the details below.

  • COP27 Virtual Ocean Pavilion Opening Event: Raising Action: An Ocean of Prospects and Opportunities in 2022 and Beyond
    • 30 August 2022 at 7:00 – 8:30 UTC
    • Speakers: Dr. Manuel Barange, Mr. Richard Delaney, Ms. Landisang Kotaro, Ms. Nozi Mbongwa, Ms. Elisabeth Mrema, Ian Mzee Ngunga, Ambassador Olivier Poivre d’Arvor, Dr. Joanna Post, Dr. Vladimir Ryabinin, Ambassador Peter Thomson, Prof. Carol Turley
  • Ocean and Climate Action: Adaptation and Resilience Practices and Tools Clinic
    • 30 August 2022 at 13:00 – 14:30 UTC
    • Speakers: Dr. Indumathie Hewawasam, Dr. Nayrah Shaltout, Dr. Roshan T. Ramessur, Dr. Bernadette Snow, Dr. Flower Msuya
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Seasonal variability of carbonate chemistry and its controls in a subtropical estuary

Published 29 August 2022 Science Closed
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Graphical abstract

Highlights

  • The seasonal variability in CO2 system was evaluated in the Patos Lagoon Estuary (PLE) between 2017 and 2021.
  • Mixing between riverine freshwater and seawater drives the changes in the CO2 system in the PLE.
  • The nonthermal effects on seasonal changes in the pCO2 prevail over thermal effects.
  • The waters of PLE are susceptible to CaCO3 undersaturation conditions during winter and spring.
  • The CO2 system in the PLE swings between an ocean-dominated and riverine-dominated estuarine behavior.

Abstract

We performed an unprecedented investigation of the seasonal variability in carbonate system parameters (total alkalinity – AT, total dissolved inorganic carbon – CT, pH, and partial pressure of carbon dioxide – pCO2) in the lower zone of the Patos Lagoon Estuary (PLE), the largest choked lagoon in the world. Sampling was conducted monthly from May 2017 to June 2021. AT and pH were measured during the study period, while other carbonate system parameters were estimated using CO2Sys software. The pH distribution reflected the average natural alkaline conditions throughout the year, with an average of 8.0 pH units. The surface waters in the lower zone of the PLE are generally characterized by a supersaturated calcium carbonate environment. However, a susceptibility to undersaturation conditions was observed during winter (calcite and aragonite) and spring (aragonite). Furthermore, the average surface water pCO2 was 394 μatm during the analyzed period, with the highest values recorded in winter and early spring. The predominant estuarine processes governing changes in the carbonate system in the PLE were the dilution and concentration of salts. These processes depend on the complex balance between freshwater outflows and oceanic inflows that change the surface salinity and produce favorable conditions for primary producer development and the input of continental carbon. However, the remineralization of organic matter and CO2 ingassing likely contribute to the deviations in the theoretical mixing line, causing the increased CT in the region. In addition, the nonthermal effects on seasonal changes in the pCO2 prevail over thermal effects, and the region presents an ocean-dominated (riverine-dominated) condition during summer and autumn (winter and spring). The novel results described here reveal the complexity and challenges that still exist to a better comprehension of how carbonate system parameters evolve temporally and spatially in the PLE, especially considering the climate- and anthropogenic-driven stressors. Finally, this study contributes to the understanding of carbonate system variability in coastal ecosystems and highlights the need for more intense and continuous biogeochemical monitoring of Southern Hemisphere estuaries.

Continue reading ‘Seasonal variability of carbonate chemistry and its controls in a subtropical estuary’

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