Effects of ocean acidification on larval development and early post-hatching traits in Concholepas concholepas (loco)

Larval stages represent a bottleneck influencing the persistence of marine populations with complex life cycles. Concholepas concholepas is a gastropod species that sustains the most important small-scale artisanal fisheries of the Chile-Peru Humboldt Coastal current system. In this study, newly-laid egg capsules of C. concholepas collected from 3 localities along the Chilean coast were used to evaluate the potential consequences of projected near-future ocean acidification (OA) on larval development and early post-hatching larval traits. We compared hatching time, hatching success and early survivorship of encapsulated larvae reared under contrasting average levels of pCO2: 382 (present-day), ca. 715 and ca. 1028 µatm CO2 (levels expected in near-future scenarios of OA). Moreover, we compared morphological larval traits such as protoconch size, thickness and statolith size at hatching. Some of the developmental traits were negatively affected by pCO2 levels, source locality, female identity, or the interaction between those factors. Meanwhile, the effect of pCO2 levels on morphological larval traits showed significant interactions depending on differences among egg capsules and females. Our results suggest that OA may decouple hatching time from oceanographic processes associated with larval transport and reduce larval survivorship during the dispersive phase, with a potential impact on the species’ population dynamics. However, the results also show geographic variability and developmental plasticity in the investigated traits. This variation may lead to an increased acclimatization ability, facilitate the persistence of natural populations and mitigate the negative effects that OA might have on landings and revenues derived from the fishery of this species.

Continue reading ‘Effects of ocean acidification on larval development and early post-hatching traits in Concholepas concholepas (loco)’

Continuous monitoring of in vivo chlorophyll a fluorescence in Ulva rigida (Chlorophyta) submitted to different CO2, nutrient and temperature regimes

A Monitoring-PAM fluorometer with high temporal resolution (every 5 min) was used to assess the effects on photosynthesis in Ulva rigida (Chlorophyta) during exposure to 2 different CO2 conditions: current (‘LC’, 390 ppm), and the predicted level for the year 2100 (‘HC’, 700 ppm) in a crossed combination with 2 different daily pulsed nitrate concentrations (‘LN’, 5 µM and ‘HN’, 50 µM) and 2 temperature regimes (ambient and ambient +4°C). Effective quantum yield (ΔF/Fm’) in the afternoon was lower under HCLN conditions than under the other treatments. The decrease in ΔF/Fm’ from noon to the afternoon was significantly lower under +4°C compared to ambient temperature. Maximal quantum yield (Fv/Fm) decreased during the night with a transient increase 1 to 3 h after sunset, whereas a transient increase in ΔF/Fm’ was observed after sunrise. These transient increases have been related to activation/deactivation of the electron transport rate and the relaxation of non-photochemical quenching. Relative electron transport rate was higher under the LC and +4°C treatment, but the differences were not significant due to high variability in daily irradiances. Redundancy analysis on the data matrix for the light periods indicates that photosynthetically active radiation through the day is the main variable determining the physiological responses. The effects of nutrient levels (mainly carbon) and experimental increase of temperature were low but significant. During the night, the effect of nutrient availability is of special importance with an opposite effect of nitrogen compared to carbon increase. The application of the Monitoring-PAM to evaluate the effects of environmental conditions by simulating climate change variations under outdoor-controlled, semi-controlled conditions is discussed.

Continue reading ‘Continuous monitoring of in vivo chlorophyll a fluorescence in Ulva rigida (Chlorophyta) submitted to different CO2, nutrient and temperature regimes’

Mass-transfer gradients across kelp beds influence Macrocystis pyrifera growth over small spatial scales

Nitrogen is essential for algal productivity but often reaches limiting concentrations in temperate ecosystems. Increased water motion enhances nitrogen uptake by decreasing the thickness of the diffusion boundary layer surrounding algal surface tissue, allowing for increased nitrogen mass-transfer across this boundary. Macrocystis pyrifera forms large beds that span the water column and can alter the surrounding physical environment by creating bed-wide boundaries that may reduce current and wave propagation to the bed interior; reduced water motion may decrease mass-transfer rates and therefore alter nitrogen uptake. We investigated whether a water mass-transfer gradient across M. pyrifera beds exists by identifying 3 bed types likely to experience different water motion intensities (open, shoreline exterior and shoreline interior) and whether this gradient influenced heterogeneity in M. pyrifera growth and tissue status during low nitrogen (summer) and high nitrogen (winter) conditions. Gypsum dissolution suggested that mass-transfer significantly increased across beds; open bed dissolution rates were approximately 6% higher than the shoreline exterior, which exhibited mean dissolution rates 17% higher than the shoreline interior. Summer kelp growth, pigmentation, tissue %N and C:N paralleled mass-transfer, where exterior kelp exhibited higher values than interior kelp. The same trends did not exist during the winter, when ambient nitrogen concentrations were high, suggesting that mass-transfer is an important mechanism for nitrogen acquisition during limitation events. This study highlights mass-transfer variability across relatively small macroalgal beds and the corresponding effects on kelp growth and nitrogen status, which previously might have been assumed as uniform due to the general wave exposure.

Continue reading ‘Mass-transfer gradients across kelp beds influence Macrocystis pyrifera growth over small spatial scales’

Glacial melt could change chemistry and food web in world’s oceans

Along with increasing sea levels, melting glaciers are putting something else into the world’s oceans — a huge load of organic carbon that has the potential to change marine chemistry and ecosystems, says a newly published study by a team of mostly Alaska scientists. (…)

The accelerated melt of glaciers gets attention because of its contribution to sea-level rise, but the “real take-home message” of the new study is that there will be “not just changes to the level of the ocean but changes to the chemistry and the food web,” Hood said.

Organic carbon is eaten by microbes and is at the base of the food web, he said. But it can also break down into inorganic carbon, which changes marine chemistry in other ways, he said. (…)

Continue reading ‘Glacial melt could change chemistry and food web in world’s oceans’

Oceans face higher acidity levels as more man-made CO2 gets absorbed

Just about 5 million tons of carbon dioxide (CO2) is dumped into the atmosphere every hour from the burning of fossil fuels mostly for transportation, electrical generation, industry and heating.

This is the fastest rate of CO2 generation that the earth has experienced in millions of years. It’s been estimated that about a quarter of the man-made carbon dioxide from the burning of fossil fuels has been absorbed by the oceans, one quarter by the land, and the rest has accumulated in the atmosphere. All told, around 600 billion tons of CO2 gas since the Industrial Revolution has been absorbed by the ocean.

The absorption of all this CO2 by the world’s oceans has certainly benefited us by reducing the amount of this greenhouse gases in the atmosphere. However, the introduction of massive amounts of CO2 in the world’s oceans is changing the sea’s water chemistry.

Continue reading ‘Oceans face higher acidity levels as more man-made CO2 gets absorbed’

Experts: include ocean acidification in climate change negotiations

Photo by M. Madsen

Photo by M. Madsen

Monaco – Actions to mitigate and adapt to ocean acidification in a future global climate deal could make the agreement stronger and facilitate its implementation. That was one of the conclusions from last week’s international workshop on ocean acidification organised by the IAEA in Monaco.

Scientists aren’t alone in raising the threat from ocean acidification; many world leaders are also being alerted to the importance of the ocean’s health for our planet. “Ocean acidification is, I believe, one of the greatest scourges resulting from the considerable development of anthropic greenhouse gas emissions, to have both concrete and global impact,” said H.S.H. Prince Albert II of Monaco. His address to the workshop described how scientific, political, and economic approaches need to be considered in unison to tackle ocean acidification.

Continue reading ‘Experts: include ocean acidification in climate change negotiations’

Acid in seas and mudflats threatens to wipe out local shellfish populations

56 million years ago, a massive release of carbon dioxide into the atmosphere and oceans caused a monumental shift in the climate, increasing the earth’s surface temperature by 11 degrees. Meanwhile, a rapid chemical change in the ocean occurred as the gas and water formed carbonic acid, eventually causing the extinction of all of the carbonate-bearing organisms in the sea, including clams, coral reefs and plankton. But unlike the 170,000-year “Paleocene-Eocene Thermal Maximum,” the climate change event happening in 2015 is almost certainly caused by humans. And the acidification of the oceans may be occurring 100 times faster than at any other time in the last 200,000 years. At that rate, scientists say Maine’s coastal marine ecosystem may not be able to adapt to the changes fast enough.

“People call this a natural process,” said Dr. Mark Green, a marine biologist at St. Joseph’s College in Standish, speaking last month at the Gulf of Maine Research Institute. “There’s really nothing natural about what’s been happening in the past 60 to 70 years. That’s when the bulk of this anthropogenic release of C02 has happened. Over the last 35 million years, C02 has never been this high.”

Continue reading ‘Acid in seas and mudflats threatens to wipe out local shellfish populations’

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Ocean acidification in the IPCC AR5 WG II

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