Ocean acidification mooring deployments on Saturn’s moon, Europa, scheduled for 2023

Global ocean acidification monitoring efforts have greatly expanded over the last decade, with a myriad of new technologies produced to help scientists understand the effects of anthropogenic CO2 on ocean chemistry. This phenomenon has been documented in the world’s main ocean basins, with some time series sustained for several decades. Ocean chemists, astronomers, and engineers are now coming together to ask the next big question in ocean acidification research: can this process be measured in other ocean worlds, and if conditions are less acidic on other planets compared to Earth, might we be able to use other ocean planets as a proxy for palaeoceanographic studies?

The ET-OAMI (Extra Terrestrial Ocean Acidification Monitoring Initiative) has published its research plan to deploy twenty moorings around Saturn’s moon, Europa on 1 April 2023, each equipped with sensors for measuring temperature, salinity, dissolved oxygen, pCO2, and pH. As Europa’s ocean is covered in a thick blanket of ice, the astronauts will drill through this 15-25km sheet prior to deploying the moorings. Astronauts will also try to collect discrete seawater samples from Europa for measurements of dissolved inorganic carbon, total alkalinity, as well as for detecting any microbial DNA. Could ocean acidification monitoring lead to humanity’s first glimpse at alien life forms?

Continue reading ‘Ocean acidification mooring deployments on Saturn’s moon, Europa, scheduled for 2023’

Ocean acidification interacts with variable light to decrease growth but increase particulate organic nitrogen production in a diatom

Highlights

• Variable light decreased growth rate and pigmentation contents in both LC and HC.

• Cells grown under variable light appeared more tolerant of high light.

• HC and varying light decreased carbon fixation rate but increased POC and PON.

• HC and varying light lead to less primary productivity but more PON per biomass.

Abstract

Phytoplankton in the upper oceans are exposed to changing light levels due to mixing, diurnal solar cycles and weather conditions. Consequently, effects of ocean acidification are superimposed upon responses to variable light levels. We therefore grew a model diatom Thalassiosira pseudonana under either constant or variable light but at the same daily photon dose, with current low (400 μatm, LC) and future high CO2 (1000 μatm, HC) treatments. Variable light, compared with the constant light regime, decreased the growth rate, Chl a, Chl c, and carotenoid contents under both LC and HC conditions. Cells grown under variable light appeared more tolerant of high light as indicated by higher maximum relative electron transport rate and saturation light. Light variation interacted with high CO2/lowered pH to decrease the carbon fixation rate, but increased particulate organic carbon (POC) and particularly nitrogen (PON) per cell, which drove a decrease in C/N ratio, reflecting changes in the efficiency of energy transfer from photo-chemistry to net biomass production. Our results imply that elevated pCO2 under varying light conditions can lead to less primary productivity but more PON per biomass of the diatom, which might improve the food quality of diatoms and thereby influence biogeochemical nitrogen cycles.

Continue reading ‘Ocean acidification interacts with variable light to decrease growth but increase particulate organic nitrogen production in a diatom’

Vulnerability of Tritia reticulata (L.) early life stages to ocean acidification and warming

Ocean acidification and warming (OA-W) result mainly from the absorption of carbon dioxide and heat by the oceans, altering its physical and chemical properties and affecting carbonate secretion by marine calcifiers such as gastropods. These processes are ongoing, and the projections of their aggravation are not encouraging. This work assesses the concomitant effect of the predicted pH decrease and temperature rise on early life stages of the neogastropod Tritia reticulata (L.), a common scavenger of high ecological importance on coastal ecosystems of the NE Atlantic. Veligers were exposed for 14 days to 12 OA-W experimental scenarios generated by a factorial design of three pH levels (targeting 8.1, 7.8 and 7.5) at four temperatures (16, 18, 20 and 22 °C). Results reveal effects of both pH and temperature (T °C) on larval development, growth, shell integrity and survival, individually or interactively at different exposure times. All endpoints were initially driven by pH, with impaired development and high mortalities being recorded in the first week, constrained by the most acidic scenarios (pHtarget 7.5). Development was also significantly driven by T °C, and its acceleration with warming was observed for the remaining exposure time. Still, by the end of this 2-weeks trial, larval performance and survival were highly affected by the interaction between pH and T °C: growth under warming was evident but only for T °C ≤ 20 °C and carbonate saturation (pHtarget ≥ 7.8). In fact, carbonate undersaturation rendered critical larval mortality (100%) at 22 °C, and the occurrence of extremely vulnerable, unshelled specimens in all other tested temperatures. As recruitment cohorts are the foundation for future populations, our results point towards the extreme vulnerability of this species in case tested scenarios become effective that, according to the IPCC, are projected for the northern hemisphere, where this species is ubiquitous, by the end of the century. Increased veliger mortality associated with reduced growth rates, shell dissolution and loss under OA-W projected scenarios will reduce larval performance, jeopardizing T. reticulata subsistence.

Continue reading ‘Vulnerability of Tritia reticulata (L.) early life stages to ocean acidification and warming’

COVID-19 update: 5th Intl. Symposium on the Ocean in a High-CO2 World

In view of the current situation with COVID-19, the Organizing Committee of the 5th International Symposium on the Ocean in a High CO2 World has extended the deadline for submissions of abstracts and travel support applications until Friday, 24 April 2020. Applicants for travel support will be notified on the outcome of their application by 7 May. A decision will be made by mid-May on whether to continue with the proposed date (7-10 September 2020) or delay the Symposium. The Symposium organizers are monitoring the situation closely and updates will be posted on the Symposium website.

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Total alkalinity minus dissolved inorganic carbon as a proxy for deciphering ocean acidification mechanisms

Highlights

• [TA–DIC] can be used for measuring OA and deciphering OA processes in global ocean.

• [TA–DIC] is conservative to ocean mixing and insensitive to temperature and pressure.

• Biological influences on OA rates can be directly linked via Redfield ratio and AOU.

Abstract

Ocean acidification (OA) defined as the decline of ocean pH and calcium carbonate saturation state (Ω) as a result of ocean uptake of CO2 from the atmosphere may have considerable negative impacts on global marine organisms and may substantially modify ocean biogeochemistry. However, as changes of pH and Ω are not conservative or linear with respect to ocean physical processes (e.g., mixing, temperature and pressure changes), the influences of anthropogenic CO2 uptake and ocean biogeochemical processes on OA rates cannot be easily identified. Here, we examine whether a composite property [TA–DIC] or the difference between total alkalinity (TA) and dissolved inorganic carbon (DIC), which is conservative to ocean mixing and is not sensitive to temperature and pressure changes, can be used for measuring OA rates and deciphering the underlying OA mechanisms in the global ocean as it in surface waters of several regional oceans. Based on Global Ocean Data Analysis Project Version 2 (GLODAPv2), we demonstrate using this property for measuring OA rates can be applied on a global ocean scale, except at low salinity e.g., <20 and when [TA–DIC] is <~50 μmol kg−1, where the relationships of [TA–DIC] with pH and/or Ω are nonlinear. However, there are almost no limitations when using this property for deciphering the underlying OA mechanisms since the change of [TA–DIC] with time is relatively small on OA timescales of decades or more. Using [TA–DIC], we can readily quantify the influences from freshwater inputs and upwelling on OA rates based on a two end-member mixing model. More importantly, through the Redfield ratio and apparent oxygen utilization, we can directly link biological influences to OA rates and conveniently quantify the biological modulation on OA rates. Therefore, we argue that using [TA–DIC] as a proxy for OA would provide a simple but powerful way of deciphering acidification mechanisms and predicting future development of acidification.

Continue reading ‘Total alkalinity minus dissolved inorganic carbon as a proxy for deciphering ocean acidification mechanisms’

Upcoming webinar: Are we already seeing impacts of OA? biological studies and research from around the world

Date: Wednesday, April 15 at 11:00am PST

Description: Join us for our first webinar of the year and a discussion about the potential impacts of OA on seafood. Presentations will include a focus on Dungeness Crab in the Pacific, oysters in the Atlantic and finfish in the Pacific. Speakers will answer questions like:

How are culturally and economically significant species being impacted by OA and other stressors?
How might some seafood economies be affected?
How is science being prioritized to better examine these impacts?

Continue reading ‘Upcoming webinar: Are we already seeing impacts of OA? biological studies and research from around the world’

Variation of pCO2 concentrations induced by tropical cyclones “Wind-Pump” in the middle-latitude surface oceans: a comparative study

The Bermuda Testbed Mooring (BTM) and Bay of Bengal Ocean Acidification (BOBOA) mooring measurements were used to identify changes in the partial pressure of CO2 at the sea surface (pCO2sea) and air-sea CO2 fluxes (FCO2) associated with passage of two tropical cyclones (TCs), Florence and Hudhud. TC Florence passed about 165 km off the BTM mooring site with strong wind speeds of 24.8 m s–1 and translation speed of 7.23 m s–1. TC Hudhud passed about 178 km off the BOBOA mooring site with wind speeds of 14.0 m s–1 and translation speed of 2.58 m s–1. The present study examined the effect of temperature, salinity, dissolved inorganic carbon (DIC), total alkalinity (TA), air-sea CO2 flux, and phytoplankton chlorophyll a change on pCO2sea as a response to TCs. Enhanced mixed layer depths were observed due to TCs-induced vertical mixing at both mooring sites. Decreased pCO2sea (–15.16±5.60 μatm) at the BTM mooring site and enhanced pCO2sea (14.81±7.03 μatm) at the BOBOA mooring site were observed after the passage of Florence and Hudhud, respectively. Both DIC and TA are strongly correlated with salinity in the upper layer of the isothermal layer depth (ILD). Strong (weak) vertical gradient in salinity is accompanied by strong (weak) vertical gradients in DIC and TA. Strong vertical salinity gradient in the upper layer of the ILD (0.031 psu m–1), that supply much salinity, dissolved inorganic carbon and total alkalinity from the thermocline was the cause of the increased pCO2sea in the BOBOA mooring water. Weak vertical salinity gradient in the upper layer of the ILD (0.003 psu m–1) was responsible for decreasing pCO2sea in the BTM mooring water. The results of this study showed that the vertical salinity gradient in the upper layer of the ILD is a good indicator of the pCO2sea variation after the passages of TCs.

Continue reading ‘Variation of pCO2 concentrations induced by tropical cyclones “Wind-Pump” in the middle-latitude surface oceans: a comparative study’


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OA-ICC HIGHLIGHTS

Ocean acidification in the IPCC AR5 WG II

OUP book