Papers find mixed impacts on ocean species from rising CO2

Britain’s Royal Society has published a helpful new collection of papers in Philosophical Transactions of the Royal Society B that provide fresh insights on how the global buildup of carbon dioxide released by human activities could affect ocean ecology.

The work adds to a growing body of science pointing to large changes, with some types of marine organisms and ecosystems seemingly able to adjust and even thrive, while others ail. And it’s quite clear that regions already heavily affected by other human activities (coastal pollution, overfishing, etc.) are — no surprise — likely to feel more stress from acidification.

The nine new studies in the Royal Society journal provide valuable detail and find a mix of impacts. Experiments transplanting certain worms around a volcanic carbon dioxide vent in the sea floor near Naples show remarkable adaptability in these organisms, both through shifts in metabolism and genetics. A poles-to-tropics assay of sea urchins shows significant impacts on larvae.

One study demonstrated that not all shifts in species’ prospects are the result of changing pH. Competition matters. In this analysis, mat-forming algae appeared to thrive in CO2-enriched marine conditions, to the detriment of corals and kelp (an echo of how some forests studies show vines thriving at the expense of trees).

A year-long laboratory study of coccolithophores — an important type of phytoplankton — found they remained capable of forming their calcium carbonate skeletons even in warmer, more acidic water. The study, which propagated 700 generations of the coccoliths*, pointed out the value of longer-duration experiments.

Most of the work is accessible only with a subscription but an excellent summary is provided in an overview paper written by the two scientists, Jasmin A. Godbold of University of Southampton and Piero Calosi of Plymouth University, who assembled the package of studies. A link to their overview is below, along with excerpts from university news releases on two of the papers.

As Bryan Walsh summarized nicely in Time today, a separate review of existing research on marine animals in acidifying conditions, published on Sunday in Nature Climate Change, found uniformly negative impacts.

It’s great to see this emerging body of work given that the oceans, despite occupying two thirds of Earth’s surface and showing signs of substantial change driven by the buildup of carbon dioxide emitted by human activities, have remained a secondary scientific focus.

The vast majority of research in recent decades on the carbon dioxide buildup has been focused on the atmospheric impacts of the accumulating greenhouse-gas blanket even though the vast majority of the heated trapped by these gases has gone first into the seas — and the drop in seawater pH driven by CO2 has been a clear signal of substantial environmental change.

In 2005, Britain’s Royal Society issued “Ocean acidification due to increasing atmospheric carbon dioxide,” a helpful report summarizing the state of knowledge at the time.

Despite its climate-centric name and mission, the Intergovernmental Panel on Climate Change has been focusing increasing attention on direct ocean impacts of carbon dioxide, most notably in an excellent 2011 report, “IPCC Workshop on Impacts of Ocean Acidification on Marine Biology and Ecosystems.” The workshop summarized the state of understanding, key uncertainties and next research steps on the shifting chemistry of the oceans and the impacts on species and ecosystems, with a focus on ecosystems of particular interest to humans.

You’ll see fresh detail, and fresh questions, in the panel’s fifth assessment of climate science, which starts rolling out in late September.

Please click here to read the overview of the newly published studies by Godbold and Calosi: “Ocean acidification and climate change: advances in ecology and evolution.”

Here’s an excerpt from the San Francisco State University news release on the laboratory experiment with diatoms:

A year-long experiment on tiny ocean organisms called coccolithophores suggests that the single-celled algae may still be able to grow their calcified shells even as oceans grow warmer and more acidic in Earth’s near future.

The study stands in contrast to earlier studies suggesting that coccolithophores would fail to build strong shells in acidic waters. The world’s oceans are expected to become more acidic as human activities pump increasing amounts of carbon dioxide into the Earth’s atmosphere.

But after the researchers raised one strain of the Emiliania huxleyi coccolithophore for over 700 generations, which took about 12 months, under high temperature and acidified conditions that are expected for the oceans 100 years from now, the organisms had no trouble producing their plated shells. [Read the rest.]

Here’s an excerpt from the news release on the fascinating work examining the response of certain worm species when transplanted in and around the 1,850-year-old seabed CO2 vent off Naples:

Researchers have discovered that some species of polychaete worms are able to modify their metabolic rates to better cope with and thrive in waters high in carbon dioxide (CO2), which is otherwise poisonous to other, often closely-related species.

The study sheds new light on the robustness of some marine species and the relative resilience of marine biodiversity should atmospheric CO2 continue to cause ocean acidification….

A team of scientists led by Plymouth University, and including colleagues from the Naples Zoological Station in Ischia; the Marine Ecology Laboratory ENEA in La Spezia, Italy; the University of Texas Galveston; and the University of Hull, conducted a three-year research project into the potential mechanisms that species of worm polychaetes use to live around the underwater CO2 vent of Ischia in Southern Italy.

The researchers collected specimens found in waters characterised by either elevated or low levels of CO2, and placed them in specially-constructed ‘transplantation chambers’, which were then lowered into areas both within and away from the volcanic vent.

They monitored the responses of the worms and found that one of the species that had been living inside the CO2 vent was physiologically and genetically adapted to the acidic conditions, whilst another was able to survive inside the vent by adjusting its metabolism.

Project leader Dr. Piero Calosi, of Plymouth University’s Marine Institute, said: “Previous studies have shown that single-cell algae can genetically adapt to elevated levels of carbon dioxide, but this research has demonstrated that a marine animal can physiologically and genetically adapt to chronic and elevated levels of carbon dioxide.

“Furthermore, we show that both plasticity and adaptation are key to preventing some species’ from suffering extinction in the face of on-going ocean acidification, and that these two strategies may be largely responsible to defining the fate of marine biodiversity.”

The results revealed that species normally found inside the CO2 vent were better able to regulate their metabolic rate when exposed to high CO2 conditions, whilst species only found outside the CO2 vent were clearly impaired by acidic waters. In fact, their metabolism either greatly decreased, indicating reduced energy production, or greatly increased, indicating a surge in the basic cost of living, in both cases making life inside the vent unsustainable.

Dr. Maria-Cristina Gambi, of the Naples Zoological Station in Ischia, explained: “Despite some species showing the ability to metabolically adapt and adjust to the extreme conditions that are found inside the CO2 vents, others appear unable to physiologically cope with such conditions.

”In this sense, our findings could help to explain mass extinctions of the past, and potential extinctions in the future, as well as shed light on the resilience of some species to on-going ocean acidification.”

The team also found that those species adapted to live inside the CO2 vent showed slightly higher metabolic rates and were much smaller in size – up to 80% smaller – indicating that adaptation came at a cost of energy for growth.

Dr. Calosi concluded that: ”Ultimately, species’ physiological responses to high CO2, as those reported by our study, may have repercussions on their abundance and distribution, and thus on the structure and dynamics of marine communities. This in turn will impact those ecosystem functions that humans rely upon to obtain goods and services from the ocean.” [Read the rest.]

Here’s the full list of studies, with summaries:

Adaptation and acclimatization to ocean acidification in marine ectotherms: an in situ transplant experiment with polychaetes at a shallow CO2 vent system

Calosi, Piero; Rastrick, Samuel; Lombardi, Chiara; de Guzman, Heidi; Davidson, Laura; Jahncke, Marlene; Giangrande, Adriana; Hardege, Joerg; Schultze, Anja; Spicer, John; Gambi, Maria Cristina

To investigate the extent to which nature or nurture determines marine animals’ responses to Ocean Acidification (OA) we carried out in-situ transplants using tolerant and sensitive worms living around a natural CO2 vent. Two tolerant species respond differently. One shows adaptation, evolving higher metabolism and smaller size (nature) but the other responds using acclimation, maintaining its size (nurture). The metabolism of sensitive species altered greatly but unpredictably. Marine animals can respond to OA by evolving or being plastic, the response being species-specific. This work throws light on sensitivity of species to past mass extinctions, and resilience to ongoing acidification.

Long-term effects of warming and ocean acidification are modified by seasonal variation in species responses and environmental conditions

Godbold, Jasmin; Solan, Martin

Over the last decade, the impacts of warming and ocean acidification have received considerable attention, and there is clear consensus that these stressors will have far-reaching consequences for species and ecosystems. Much of the evidence, however, is based on short-term experiments that ignore long-term variation in how species and ecosystems respond. Using the longest study to date, we show that species can take much longer times to respond than previously thought and that the impact of these responses on important ecosystem properties varies with season. These findings suggest that the ecological consequences of climate change may diverge from present expectations.

The other ocean acidification problem: CO2 as a resource among competitors for ecosystem dominance

Connell, Sean; Kroeker, Kristy; Fabricius, Katharina; Kline, David; Russell, Bayden

We explore how ocean acidification combines with complex environmental changes across a number of scales, highlight the multiplicity of factors and complexities that cause variation, and raise awareness of CO2 as a resource whose change in availability could have wide ranging community consequences beyond its direct effects.  The positive effects of CO2 on producers are likely to be highly variable among species. Accordingly, there is an enormous potential for shifts in species dominance, as some species gain a relative advantage in a high CO2 world.

Short- and long-term conditioning of a temperate marine diatom community to acidification and warming

Tatters, Avery; Roleda, Michael; Schnetzer, Astrid; Fu, Feixue; Hurd, Catriona; Boyd, Phillip; Caron, David; Lie, Alle; Hoffmann, Linn; Hutchins, David

Ocean acidification and greenhouse warming will interactively influence competitive success of key phytoplankton groups such as diatoms, but how long-term responses to global change will affect community structure is unknown. We incubated a natural diatom community from coastal New Zealand waters in a short-term incubation experiment using a factorial matrix of temperature and CO2, and measured effects on community structure. Our results support the use of short-term manipulative experiments spanning weeks as proxies to understand the potential effects of global change forcing on diatom community structure over longer timescales such as years.

Ocean acidification and rising temperatures may increase biofilm primary productivity but decrease grazer consumption

Russell, Bayden; Connell, Sean; Findlay, Helen; Tait, Karen; Widdicombe, Stephen; Mieszkowska, Nova

Warming and acidifying oceans, a consequence of carbon dioxide emissions, are changing coastal ecosystems; we know this. Our experiment shows that these changes may be unpredictable because the combination of temperature and acidification changes the amount and type of biofilm, green rock slime at the base of the intertidal food web, while reducing the ability of marine snails to eat it. This inability of snails to compensate for higher maintenance costs, likely to be a stress response as they are pushed beyond their normal functioning range, warns us that these ecosystems are likely to change beyond what we currently know.

Bioturbation determines the response of benthic ammonia oxidising microorganisms to ocean acidification

Laverock, Bonnie; Kitidis, Vassilis; Tait, Karen; Gilbert, Jack; Osborn, A; Widdicombe, Stephen

Nitrification is a key process in coastal sediments, contributing to the breakdown of organic matter and the recycling of nutrients in both the sediments and the overlying water. However, microbial nitrification rates in seawater are dramatically inhibited by ocean acidification. We show that, in coastal sediments, the response may be dependent upon animals living within the sediment. Under normal conditions, mud shrimps enhance sediment nitrification rates, but at reduced seawater pH, this functionality rapidly declines. Ocean acidification therefore has the potential to significantly alter coastal nutrient cycling and productivity through knock-on effects on animal-microbe interactions.

Effects of acidification on olfactory-mediated behaviour in freshwater and marine ecosystems: a synthesis

Leduc, Antoine; Munday, Philip; Brown, Grant; Ferrari, Maud

Aquatic ecosystem acidification has significant detrimental consequences to olfaction and chemosensory abilities of aquatic organisms. This loss of sensory function may lead to impaired behavioural responses of potentially far-reaching consequences in population dynamics and community structure. Whereas the ecological impacts of such impairments may be similar between freshwater and marine ecosystems, the underlying mechanisms are quite distinct. Molecular change to chemicals at low pH is the primary cause of impaired olfactory-mediated behaviour of fishes in freshwater conditions. In contrast, interference of high CO2 with brain neurotransmitter functions is the primary cause of such impaired behaviour in experiments simulating future ocean acidification.

The stunting effect of a high CO2 ocean on calcification and development in sea urchin larvae, a synthesis from the tropics to the poles

Byrne, Maria; Lamare, Miles; Uthicke, Sven; Dworjanyn, Symon; Winter, David

The ocean is warming, acidifying and decreasing in mineral saturation, compromising the ability of larvae to make shells and skeletons. We analysed responses of the calcifying larvae of sea urchins, an ecologically important group, to ocean change stressors in a synthesis of data from species from tropical to polar environments and from intertidal to subtidal habitats. Acidification impairs calcification and growth while warming promotes growth. We need to understand the effects of both stressors. Responses of larvae from across world regions indicate overall trends despite disparate environments and ecology as well as differences in the sensitivities of tropical and polar species.

Emiliania huxleyi increases calcification but not expression of calcification-related genes in long-term exposure to elevated temperature and pCO2
Benner, Ina; Diner, Rachel; Lefebvre, Stephane; Li, Dian; Komada, Tomoko; Carpenter, Edward; Stillman, Jonathon

We cultured a globally important calcifying phytoplankton, the coccolithophore Emiliania huxleyi, for >700 generations under present and future ocean conditions of carbon dioxide and temperature, and analyzed their physiological and genomic response.  We found that cells produced more calcium carbonate under future ocean conditions, but had the same amount of organic carbon as in present conditions.  Surprisingly, they did this without altering the expression of genes thought to be involved with the calcification process.  Our findings have significance for global carbon cycling, oceanic carbon sequestration, and the cellular biology of coccolithophores.

Andrew C. Revkin, New York Times Opinion Pages, 26 August 2013. Article.

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