Impacts of increased atmospheric CO2 concentration on photosynthesis and growth of micro- and macro-algae

Marine photosynthesis drives the oceanic biological CO2 pump to absorb CO2 from the atmosphere, which sinks more than one third of the industry-originated CO2 into the ocean. The increasing atmospheric CO2 and subsequent rise of pCO2 in seawater, which alters the carbonate system and related chemical reactions and results in lower pH and higher HCO3 − concentration, affect photosynthetic CO2 fixation processes of phytoplanktonic and macroalgal species in direct and/or indirect ways. Although many unicellular and multicellular species can operate CO2-concentrating mechanisms (CCMs) to utilize the large HCO3 − pool in seawater, enriched CO2 up to several times the present atmospheric level has been shown to enhance photosynthesis and growth of both phytoplanktonic and macro-species that have less capacity of CCMs. Even for species that operate active CCMs and those whose photosynthesis is not limited by CO2 in seawater, increased CO2 levels can down-regulate their CCMs and therefore enhance their growth under light-limiting conditions (at higher CO2 levels, less light energy is required to drive CCM). Altered physiological performances under high-CO2 conditions may cause genetic alteration in view of adaptation over long time scale. Marine algae may adapt to a high CO2 oceanic environment so that the evolved communities in future are likely to be genetically different from the contemporary communities. However, most of the previous studies have been carried out under indoor conditions without considering the acidifying effects on seawater by increased CO2 and other interacting environmental factors, and little has been documented so far to explain how physiology of marine primary producers performs in a high-CO2 and low-pH ocean.

The state of the climate—and of climate science

In the list of world challenges, global warming might be at once the most alarming and the most controversial. According to some predictions, climate change caused by human activity could cause mass extinction in the oceans, redraw the planet’s coastlines, and ravage world food supplies. At the same time, a significant portion of the American public questions whether global warming will really cause any major harm; many still doubt that human-driven warming is happening at all. How can we settle the debate? And can we intervene in the process or find ways to adapt to the new conditions? In conjunction with the National Science Foundation and the San Francisco Exploratorium, DISCOVER brought together four experts to discuss the reality and meaning of climate change. In a highly nuanced exchange of ideas, these researchers weighed the various scenarios and laid out a road map for navigating the warmer world to come. The conversation was moderated by DISCOVER’s editor in chief, Corey S. Powell.

Ozone hole trims polar water’s CO2-absorbing power

Simulations also suggest that the dearth of ozone over Antarctica leads to ocean acidification

The ozone hole over Antarctica does more than let a little extra ultraviolet light reach ground level: It boosts ocean acidification in the waters surrounding the icy continent and reduces the amount of carbon dioxide emissions those waters can absorb.

Recent research has indicated that the oceans surrounding Antarctica aren’t absorbing nearly as much planet-warming CO2 from the atmosphere as they did in previous decades (SN: 5/26/07, p. 333). In one of those studies, scientists speculated that meteorological effects of the high-altitude ozone hole over Antarctica, including strengthening of winds at sea level, might be to blame. Now, results of computer simulations bolster that notion, researchers report online June 20 in Geophysical Research Letters.

Francis Codron, an atmospheric scientist at the French national center for scientific research, CNRS, in Paris, and his colleagues used climate models to compare two scenarios: one in which the stratosphere over Antarctica had no ozone hole from 1975 to 2004 and one in which the stratosphere had a hole like the one that has actually developed. The researchers ran five simulations for each of the two scenarios, Codron says.

Klimawandel gibt dem Meer Saures (in german)

Die co2-emissionen setzen den ozeanen zu, mit dramatischen Folgen für meeresbewohner

Ohne die Ozeane hätten wir heute schon das Klima des Jahres 2050. Mehr als eine halbe Milliarde Tonnen des Treibhausgases Kohlendioxid (CO2) haben die Weltmeere seit vorindustrieller Zeit geschluckt. Das ist rund die Hälfte aller vom Menschen verursachten fossilen CO2-Emissionen.

Aus Sicht vieler Meeresbewohner hat diese Pufferfunktion der Ozeane eine traurige Kehrseite: Im Wasser gelöst wird CO2 – wie wir es vom Mineralwasser her kennen – zu Kohlensäure. Da Säure Kalk auflöst, ist dies Gift für kalkhaltige Organismen wie Korallen, Muscheln, Garnelen, Meeresschnecken, manche Planktonarten und Algen. Ihnen kommt die Bausubstanz für ihre teilweise filigranen Kalkskelette abhanden. In Extremfällen kann das veränderte Meerwasser die Kalkstrukturen sogar auflösen.

High carbon dioxide levels cause abnormally large fish ear bones

Rising carbon dioxide levels in the ocean have been shown to adversely affect shell-forming creatures and corals, and now a new study by researchers at Scripps Institution of Oceanography at UC San Diego has shown for the first time that CO2 can impact a fundamental bodily structure in fish.

A brief paper published in the June 26 issue of the journal Science describes experiments in which fish that were exposed to high levels of carbon dioxide experienced abnormally large growth in their otoliths, or ear bones. Otoliths serve a vital function in fish by helping them sense orientation and acceleration.

The researchers had hypothesized that otoliths in young white seabass growing in waters with elevated carbon dioxide would grow more slowly than a comparable group growing in seawater with normal CO2 levels. They were surprised to discover the reverse, finding “significantly larger” otoliths in fish developing in high-CO2 water.

Marine life ‘at risk’ from C02

THE Arctic Ocean could become corrosive to marine life within a matter of decades, according to leading scientists who will be attending a critical meeting in Plymouth next week.

More than 100 marine scientists specialising in ocean acidification will gather at the Plymouth University on Monday to discuss their research into the dramatic effects of excess carbon dioxide being absorbed from the atmosphere into the oceans.

Ocean acidification, often referred to as “the other C02 problem”, is a relatively recently recognised consequence of C02 emissions and threatens to corrode shell or skeleton-forming marine organisms. The oceans are a natural sink for C02 and, because of their sheer collective size, were once thought too big to be affected by humans.