Archive for September, 2020

Warming and ocean acidification may decrease estuarine dissolved organic carbon export to the ocean

Estuaries make a disproportionately large contribution of dissolved organic carbon (DOC) to the global carbon cycle, but it is unknown how this will change under a future climate. As such, the response of DOC fluxes from microbially dominated unvegetated sediments to individual and combined future climate stressors of warming (from Δ−3 °C to Δ+5 °C on ambient mean temperatures) and ocean acidification (OA, ~2 times the current partial pressure of CO2, pCO2) was investigated ex situ. Warming alone increased sediment heterotrophy, resulting in a proportional increase in sediment DOC uptake, with sediments becoming net sinks of DOC (3.5 to 8.8 mmol-C m−2 d−1) at warmer temperatures (Δ+3 °C and Δ+5 °C, respectively). This temperature response changed under OA conditions, with sediments becoming more autotrophic and a greater sink of DOC (1 to 4 times greater than under current-pCO2). This response was attributed to the stimulation of heterotrophic bacteria with the autochthonous production of labile organic matter by microphytobenthos. Extrapolating these results to the global area of unvegetated subtidal estuarine sediments, the future climate of warming (Δ+3 °C) and OA may decrease the estuarine export of DOC by ~80 % (~150 Tg-C yr−1) and have a disproportionately large impact on the global DOC budget.

Continue reading ‘Warming and ocean acidification may decrease estuarine dissolved organic carbon export to the ocean’

Bigfin reef squid demonstrate capacity for conditional discrimination and projected future carbon dioxide levels have no effect on learning capabilities

Anthropogenic carbon dioxide (CO2) emissions are being absorbed by the oceans, a process known as ocean acidification, and risks adversely affecting a variety of behaviours in a range of marine species, including inhibited learning in some fishes. However, the effects of elevated CO2 on learning in advanced invertebrates such as cephalopods are unknown. Any impacts to the learning abilities of cephalopods could have far-reaching consequences for their populations and the communities they inhabit. Cephalopods have some of the most advanced cognitive abilities among invertebrates and are one of the few invertebrate taxa in which conditional discrimination has been demonstrated, though the trait has not been demonstrated in any species of squid. Here, we tested for the first time the capacity for conditional discrimination in a squid species (Sepioteuthis lessoniana). Furthermore, we investigated the effects of projected future CO2 levels (1,084 µatm) on conditional discrimination and learning more generally. A three-task experiment within a two-choice arena was used to test learning and conditional discrimination. Learning was measured by improvements in task completion in repeated trials over time and the number of trials required to pass each task. Squid exhibited significant learning capabilities, with an increase in correct choices over successive trials and a decrease in the number of trials needed to complete the successive tasks. Six of the 12 squid tested successfully passed all three tasks indicating a capacity for conditional discrimination in the species. Elevated CO2 had no effect on learning or on the capacity for conditional discrimination in squid. This study highlights the remarkable cognitive abilities of S. lessoniana, demonstrated by their capacity for conditional discrimination, and suggests that ocean acidification will not compromise learning abilities. However, other behavioural traits in the species have been shown to be altered at comparable elevated CO2 conditions. It is not clear why some ecologically important behaviours are altered by elevated CO2 whereas others are unaffected. Future research should focus on the physiological mechanism responsible for altered behaviours in squid at elevated CO2.

Continue reading ‘Bigfin reef squid demonstrate capacity for conditional discrimination and projected future carbon dioxide levels have no effect on learning capabilities’

Oregon recognized as leader in efforts to stem climate and ocean changes

Shellfish are particularly vulnerable to OAH and are also the bread and butter of Oregon’s commercial seafood industry, bringing over $100 million annually into coastal communities.

SALEM — Oregon again was recognized as a leader in efforts to stem climate change and ocean acidification and hypoxia (OAH).

The legislatively created Oregon Coordinating Council on OAH recently was recognized for its efforts to guide Oregon’s response to ocean change and OAH. The Coordinating Council received an Honorable Mention for the 2020 Climate Adaptation Leadership Award for Natural Resources.

ODFW’s Dr. Caren Braby and OSU’s Dr. Jack Barth lead the Coordinating Council.

The award, given by the Association of Fish and Wildlife Agencies, recognizes the Coordinating Council’s exemplary leadership in reducing climate related threats through developing and carrying out the 2019-2025 OAH Action Plan.

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East coast oysters show resilience to ocean acidification

Oysters from Saint-Simon Bay in northern New Brunswick have been shown to be impressive tolerance to ocean acidification, according to a new study in the ICES Journal of Marine Science.

Experimental eastern oyster broodstock at the oyster hatchery in northern New Brunswick

Globally, seawater pH is decreasing as the oceans absorb excess carbon dioxide from the atmosphere.

“The oceans are a massive sink for atmospheric carbon dioxide,” says Jeff Clements, lead author of the study. “All of this extra CO2 is changing the chemistry of the oceans, with potentially deleterious effects for marine shellfish.”

While ocean pH is not actually acidic by definition, the change in ocean pH presents a challenge for marine life. A major consequence is that shellfish like oysters have a harder time making shells. Although studies have reported negative effects of ocean acidification on oysters in the eastern United States, how oysters in Atlantic Canada may be affected remains unknown.

To fill this knowledge gap, the researchers studied Eastern oysters (Crassostrea virginica) at the L’Étang Ruisseau Bar oyster hatchery in northern New Brunswick. They found that adult oysters actually increased their reproductive development under low pH. In addition, while juvenile oysters were smaller and had a higher percentage of deformities under low pH, their survival was actually higher.
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Nordic Seas acidification

Being windows to the deep ocean, the Nordic Seas play an important role in transferring anthropogenic carbon, and thus ocean acidification, to the abyss. Due to its location in high latitudes, it is further more sensitive to acidification compared with many other oceanic regions. Here we make a detailed investigation of the acidification of the Nordic Seas, and its drivers, since pre-Industrial to 2100 by using in situ measurements, gridded climatological data, and simulations from one Earth System Model (ESM). In the last 40 years, pH has decreased by 0.11 units in the Nordic Seas surface waters, a change that is twice as large as that between 1850–1980. We find that present trends are larger than expected from the increase in atmospheric CO2 alone, which is related to a faster increase in the seawater pCO2 compared with that of the atmosphere, i.e. a weakening of the pCO2 undersaturation of the Nordic Seas. The pH drop, mainly driven by an uptake of anthropogenic CO2, is significant all over the Nordic Seas, except for in the Barents Sea Opening, where it is counteracted by a significant increase in alkalinity. We also find that the acidification signal penetrates relatively deep, in some regions down to 2000 m. This has resulted in a significant decrease in the aragonite saturation state, which approaches undersaturation at 1000–2000 m in the modern ocean. Future scenarios suggest an additional drop of 0.1–0.4 units, depending on the emission scenario, in surface pH until 2100. In the worst case scenario, RCP8.5, the entire water column will be undersaturated with respect to aragonite by the end of the century, threatening Nordic Seas cold-water corals and their ecosystems. The model simulations suggest that aragonite undersaturation can be avoided at depths where the majority of the cold-water corals live in the RCP2.6 and RCP4.5 scenarios. As these results are based on one model only, we request additional observational and model studies to better quantify the transfer of anthropogenic CO2 to deep waters and its effect on future pH in the Nordic Seas.

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Sentinels of ocean acidification impacts survived Earth’s last mass extinction

Two groups of tiny, delicate marine organisms, sea butterflies and sea angels, were found to be surprisingly resilient — having survived dramatic global climate change and Earth’s most recent mass extinction event 66 million years ago, according to research published this week in the Proceedings of the National Academy of Sciences led by Katja Peijnenburg from Naturalis Biodiversity Center in the Netherlands.

Sea butterflies and sea angels are pteropods, abundant, floating snails that spend their entire lives in the open ocean. A remarkable example of adaptation to life in the open ocean, these mesmerizing animals can have thin shells and a snail foot transformed into two wing-like structures that enable them to “fly” through the water.

Continue reading ‘Sentinels of ocean acidification impacts survived Earth’s last mass extinction’

The origin and diversification of pteropods precede past perturbations in the Earth’s carbon cycle

Pteropods are a group of planktonic gastropods that are widely regarded as biological indicators for assessing the impacts of ocean acidification. Their aragonitic shells are highly sensitive to acute changes in ocean chemistry. However, to gain insight into their potential to adapt to current climate change, we need to accurately reconstruct their evolutionary history and assess their responses to past changes in the Earth’s carbon cycle. Here, we resolve the phylogeny and timing of pteropod evolution with a phylogenomic dataset (2,654 genes) incorporating new data for 21 pteropod species and revised fossil evidence. In agreement with traditional taxonomy, we recovered molecular support for a division between “sea butterflies” (Thecosomata; mucus-web feeders) and “sea angels” (Gymnosomata; active predators). Molecular dating demonstrated that these two lineages diverged in the early Cretaceous, and that all main pteropod clades, including shelled, partially-shelled, and unshelled groups, diverged in the mid- to late Cretaceous. Hence, these clades originated prior to and subsequently survived major global change events, including the Paleocene–Eocene Thermal Maximum (PETM), the closest analog to modern-day ocean acidification and warming. Our findings indicate that planktonic aragonitic calcifiers have shown resilience to perturbations in the Earth’s carbon cycle over evolutionary timescales.

Continue reading ‘The origin and diversification of pteropods precede past perturbations in the Earth’s carbon cycle’

Insight from sports medicine leads to discovery about mussels in an acidifying ocean

Photo: NOAA Fisheries

The feeding rates of blue mussels slows down under ocean acidification conditions, and the cause may be the slowing beat of gill cilia, similar to a known response in human lung cells.

Shannon Meseck, a NOAA Fisheries research chemist and marathon runner, was initially interested in how ultra-runners can tolerate higher levels of carbon dioxide than non-athletes. A chance conversation with a medical doctor about ciliated cells in the human lung turned on a light bulb in her head. Could similarities between the function of these cells in humans and in blue mussels explain the mussels’ response to increasing acidification in the ocean?

Blue mussels, one of the mollusks Meseck studies,  are economically and environmentally important filter-feeding bivalves. Like other bivalves, they use their gills for feeding and respiration. Gill cilia—microscopic, hair-like structures—create and control the current that allows water and food to flow over the gills. The cilia also help capture and sort food particles.

Continue reading ‘Insight from sports medicine leads to discovery about mussels in an acidifying ocean’

Physiological feeding rates and cilia suppression in blue mussels (Mytilus edulis) with increased levels of dissolved carbon dioxide


  • Increase carbon dioxide decreases cilia beat frequency for blue mussel.
  • Ocean acidification decreased clearance rates in blue mussels.
  • Ocean acidification resulted in changes in particle selection for marine bivalves.


Gills of marine bivalves, the organs that mediate water flow for feeding and other physiological functions, are exposed to increasing levels of carbon dioxide (CO2) in seawater, in response to ocean acidification (OA). We examined the effects of elevated dissolved CO2 upon filtration and feeding behavior of the blue mussel, Mytilus edulis, under field conditions and in laboratory studies. We further investigated possible changes in cilia beat function in response to elevated dissolved CO2. Physiological filtration and feeding variables measured; included clearance, filtration, organic ingestion, and assimilation rates and selection efficiency, which decreased with increasing CO2. Absorption efficiency was not affected by dissolved CO2. Cilia beat frequency declined in excised lateral cilia (lc) exposed to increasing CO2 levels, which appears to account for decreased clearance rates observed in field and laboratory experiments. Our data suggest that under conditions of increased CO2 blue mussels will experience changes in physiological filtration, feeding rates, and cilia beat function that could have consequences for fitness and performance.

Continue reading ‘Physiological feeding rates and cilia suppression in blue mussels (Mytilus edulis) with increased levels of dissolved carbon dioxide’

Climate change and its impact on the coastal region

Coastal zones are highly populated and among the world’s most diverse and productive environments. Coastal areas include complex ecosystems such as coral reefs, mangrove, salt marshes, seagrasses, etc. Global climate change accelerated by human activities affects the physical, biological, and biogeochemical characteristics of the coastal regions. Consequently the ecological structure, their functions, and the goods and services of the coastal regions are being modified. The ecosystem resilience will be greatly reduced through human impacts as well as rising sea levels, increasing sea temperatures, and other climate ocean-related changes, including prevailing wave activity and storm waves and surges. Sea level rise and increased seawater temperatures are projected to accelerate beach erosion and cause degradation of natural coastal defences such as mangroves and coral reefs resulting in negative effect on the socio-economic aspects of coastal population. Therefore, integrated approaches are essential at various levels to manage the climate change impact on coastal region.

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Ocean acidification in the IPCC AR5 WG II

OUP book