climate change

Climate change is adding fuel to the Fort McMurray fire – and it’s okay to say that

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If you would like to support the aid in Fort McMurray, you can donate to the Red Cross here, or by texting REDCROSS to 30333 ($5 donation per text message).

View of wildfire from Highway 63 in Fort McMurra, on 3 May, 2016. (Photo: Reuters)
View of wildfire from Highway 63 in Fort McMurray, on 3 May, 2016. (Photo: Reuters)

As the province of Alberta declares a state of emergency and tens of thousands of people are displaced, social media is abuzz with shock, sympathy, and support.

While scrolling through my Twitter feed yesterday, I decided to scour the #yymfire hashtag. At the top of the thread was a tweet from @Slate which linked to an article on their site published by @EricHolthaus. In a moment of weakness, I decided to take a gander at the online responses to the article. Almost every response to the tweet included commentary about the insensitivity of associating this disaster with political arguments about global climate change. The fire, the responses argued, is an inevitable result of conditions inherent to the location of Fort McMurray and would have resulted in the same devastation regardless of climate conditions, concluding that it is inappropriate and fallacious to place the extreme loss to the working class people in the region in the context of climate change. I can empathize with these responses – emotions are high and the laceration of this tragedy is fresh. However, knowing that climate science does, in fact, predict increased wildfire occurrence (that is, the event can be scientifically linked to climate change), I’m inclined to disagree with the majority of responses on Twitter.

At the same time, I came across Facebook posts from numerous friends linking to a post from a man in British Columbia (that has subsequently been deleted after going negatively viral) expressing his lack of sympathy and karmic association towards a tragic fire in a town that exemplifies the Canadian oil industry and the proliferation of climate change – of course this attitude is highly insensitive and inappropriate.

So is it okay to talk about this fire in the context of climate change when the area affected is so heavily scrutinized for being a major contributor to it? My short answer is undoubtedly yes.

While the proximate cause of this fire wasn’t climate change. Of course, climate change isn’t the proximate cause of any fire – usually it’s something like lightning or some a**hole who doesn’t listen to fire advisories. However, the functional reasons for the fire’s spread and destruction can be largely attributed to record-breaking, abnormally-high temperatures and humidity – and this is going to be something that we face more often in both the immediate and distant future. Stating that isn’t insensitive – it’s factual and it’s our reality. What is insensitive is stating that this tragedy is karmic and to lack sympathy for the people affected. I’d consider those that feel this way as environmental extremists (yes, like religion and politics, environmentalism has extremism too), and they need not be pandered to.

I have many close friends working in Fort McMurray that are impacted by the devastation, and although I firmly think climate change has played a large role in this event, I’d never wish this tragedy on anyone. But discussing and admitting to the factors contributing to these events is a necessary part of adapting and making sure they don’t happen again.

So I will continue to discuss this tragedy in the context of climate change, and feel that we should all be framing this tragedy in the context of climate change, because it is important to. Not only because more people need to be aware of what future climate change means for us as a species, but in order to prepare ourselves for the next event of this magnitude – because it is inevitably going to happen. Such a discussion doesn’t imply insensitivity, nor should it be treated as such.

It’s times like these that I wish I could do more than donate money, express sympathy, and educate people, but that is what I’ve got to offer. My heart goes out to those affected. In the words of everybody’s favorite Cape Bretoner, “best of luck to ya’”.

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Climate change and marine biology: questioning our understanding

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Copyright © Joachim S. Müller, Creative Commons
Copyright © Joachim S. Müller, Creative Commons

At some point or another, you’ve probably read or heard the common headline:

“Climate change threatens ____________ (insert your favorite species).”

But once you’ve digested the doom-and-gloom story, have you ever wondered how we know how climate change impacts various marine species? What is it that scientists do that leads to such claims? Are these claims legitimate? How accurate are they?

When assessing the impacts of climate change on living organisms, most studies employ controlled experiments, where researchers can tinker with one or a number of relevant variables to mimic predicted future conditions and observe how organisms respond to these conditions. There are substantial problems with this approach, however. First, biological responses are typically assessed in the context of only one or two environmental stressors, while we know that a multitude of factors (e.g., temperature, acidification, eutrophication, hypoxia, salinity, etc.) will have independent and/or synergistic biological impacts. Second, over the duration of such experiments, conditions are often kept constant, mimicking average future conditions. Finally, studies typically assess species in isolation, which doesn’t adequately address the community and/or ecosystem consequences of climate change, nor how individual species will respond when residing in their natural habitats. Consequently, I argue that the biological effects of a changing climate are, at present, poorly understood.

Table 1. Summary of studies assessing the behavioural impacts of ocean acidification in the context of co-occurring environmental parameters expected to occur under future climate change scenarios.
Table 1. Summary of studies assessing the behavioural impacts of ocean acidification in the context of co-occurring environmental parameters expected to occur under future climate change scenarios.

The ways in which organisms respond to a given environmental stressor do not solely depend on that single stressor. The interactive effects of multiple environmental stressors can elicit drastically different biological responses. For example, it is increasingly recognized that food availability can modulate the magnitude of effect when assessing the biological impacts of climate change in the ocean, suggesting that, at least physiologically, many species can tolerate a warming and acidifying ocean as long as they have enough energy to do so. In a recent literature review of the behavioural impacts of ocean acidification (Clements & Hunt, in review), we found that 7/8 publications incorporating the independent and synergistic effects multiple environmental stressors (Table 1) in experiments derived different conclusions than when acidification was tested in isolation. Furthermore, the outcomes were all over the board, with additional stressors attenuating, amplifying, or not affecting the behavioural endpoint in question. The problem is that only 8/57 studies actually addressed the effects of multiple environmental stressors – a problem that transfers other biological responses to climate change as well.

It doesn’t take a rocket scientist to know that nature is far from stable. Growing up in the Maritime Provinces of Canada, I know that a look out the window from one moment to the next can yield drastically different weather observations. While the term “weather” applies to environmental phenomena over small temporal scales (hours, day, weeks, months, etc.), “climate” refers to the average of those weather conditions over long periods of time (years, decades, centuries, millennia, etc.). Since climate is a function of weather, understanding the impacts of climate change requires incorporating an understanding of the weather that derives the climate. The variability (i.e., the weather) around projected climatic means can modulate the amount of time that an organism experiences environmental conditions above or below a threshold whereby the organism is affected (Figure 1). Unfortunately, few studies take variability into consideration. In the same literature review mentioned above (Clements & Hunt, in review), only 1/57 studies took variability into consideration, reporting a negative effect of acidification + variability, while acidification alone elicited no effect.  Furthermore, studies incorporating multiple environmental stressors and their associated variability are virtually non-existent. Ultimately, a strong understanding of how climate change influences biology requires embracing variability, not dismissing it – otherwise our understanding remains flawed.

Figure 1. Potential degrees of current and projected variability in diurnal oceanic pCO2 where variability increases over time (A) and where variability remains consistent over time (B). Distance between dashed lines indicate the relative amount of time organisms would be expected to spend above thresholds where they would be impacted by ocean acidification. Patterns of variability across ecosystems will differ as a result of differing types and magnitudes of various processes across systems.
Figure 1. Potential degrees of current and projected variability in diurnal oceanic pCO2 where variability increases over time (A), where variability remains consistent over time (B), and where variability decreases over time (C). Distance between vertical dashed lines indicate the relative amount of time organisms would be expected to spend above thresholds where they would be impacted by ocean acidification. Patterns of variability across ecosystems will differ as a result of differing types and magnitudes of various processes across systems.

Species interactions can also elicit different responses to climate change. For example, the presence of marine plants and their density/abundance within a given marine system can, to an extent, buffer oceanic pH and mitigate the impacts of ocean acidification to other organisms residing within that system. As such, understanding the impacts of climate change in terms of community- and ecosystem-wide consequences not only provides a broader understanding of the biological and ecological impacts of climate change, but can provide a more accurate understanding of how individual organisms will be impacted by shifting environmental conditions within their natural habitats.

So does this all mean that we shouldn’t worry about climate change? – ABSOLUTELY NOT! Climate change is currently, and will continue to be a huge problem for humans and a plethora of other organisms. However, I do think that the degree to which climate change will be a biological problem is poorly understood. On the bright side, scientists are beginning to recognize these shortcomings and are now working toward a better understanding of how climate change will affect marine organisms. Furthermore, not all studies simply employ highly controlled laboratory experiments; there is field evidence that provides sound information regarding the biological effects of climate change for some species. Ultimately, stamp collecting gets us nowhere – experimental approaches need to incorporate multiple shifting stressors and their associated variability, as well as numerous species (optimally mimicking communities or ecosystems) in order to adequately understand the biological implications of a changing climate. Until then, we will likely remain naive about the ways in which climate change will impact marine species.

Finding Nemo in an acidified ocean

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Nemo
Figure 1. Nemo, from Disney-Pixar’s “Finding Nemo”. Source: pixar.wikia.com.

It’s a story that many of us know well; a charismatic, touching and often hilarious tale of a father’s relentless pursuit to find his lost son. In Disney-Pixar’s 2003 blockbuster, “Finding Nemo”, a young clownfish by the name of Nemo ventures off into the open ocean, is unfortunately captured by humans, and is sent off to reside in a dentist office fish tank in Sydney, Australia. As a result, Nemo’s father, Marlin, with the company of his newfound pal, Dory, sets off across the big blue ocean to find his son and bring him home, while Nemo frantically plans his escape from the dentist office fish tank. After much hullabaloo, including Marlin and Dory encountering a hungry shark and a humpback whale, Nemo eventually escapes the dentist’s office and catches up with his dad (who unfortunately thinks Nemo is dead) and together with Dory they head for home – a touching story indeed. Though the ending is certainly of the feel-good genre, would the story have turned out the same in an acidified ocean?

Ocean acidification is a process whereby increasing atmospheric CO2 dissolves into the oceans, lowering their pH and making them more acidic. Though calcifying organisms are thought to be among the most negatively impacted, research has also suggested that an increasingly acidifying ocean can impair the behaviour of various marine fishes, with coral reef fish being the most intensively studied. Furthermore, among the coral reef fishes that have been studied, clownfish (Amphiprion percula) have been a fairly popular species of interest.

 Figure 1. Data reported in A) Dixson et al (2009), B) Simpson et al. (2011), and C) Munday et al. (2009), for predator avoidance (A, B) and homing ability (C).

Figure 2. Data reported in A) Dixson et al. (2009), B) Simpson et al. (2011), and C) Munday et al. (2009), depicting the impacts of elevated CO2 on the predator avoidance (A, B) and homing (C) behaviour in juvenile clownfish.

In 2010, Danielle Dixson and colleagues reported the results of their research comparing the ability of juvenile clownfish to avoid their predators under both ambient (present day) and elevated (2100 projection) CO2 conditions. What Dixson et al. (2010) found was that, in comparison to fish raised in present day CO2, juvenile clownfish reared under elevated CO2 were unable to distinguish between predators and non-predators, spending equal amounts of time hanging around both (though newly-hatched larvae were unaffected; Figure 2A). Likewise, Simpson et al. (2011) reported that clownfish lost their ability to avoid the sounds of their predators when raised under elevated CO2 conditions (Figure 2B). Additionally, negative impacts on the homing ability of clownfish have also been reported. Munday et al. (2009) found that baby clownfish raised under elevated CO2 conditions lost the ability to choose their preferred and optimal habitat and were also unable to distinguish their parents from other clownfish (Figure 2C).

These negative changes in clownfish behaviour are likely induced by a change in their biochemistry when reared under elevated CO2 conditions. Studies have suggested that high levels of CO2 interfere with one particular chemical in the brains of fishes (and other animals as well) – GABA (chief inhibitory neurotransmitter vertebrate central nervous systems; e.g. Nilsson et al. 2012). Since the GABAA receptor has a specific conductance for Chlorine (Cl) and bicarbonate (HCO3) – the two ions most likely to be impacted under elevated CO2 conditions – this explanation seems probable.

Figure 3. Marlin and Dory swim away from a hungry shark in Disney-Pixar’s “Finding Nemo”. In an acidified ocean, things may have turned out much different. Source: lyrics.wikia.com

So how would this have impacted Finding Nemo? Well, if we revisit the plot of the movie, there are two ways in which acidification may have changed the outcome of Finding Nemo. Firstly, in the original movie, Marlin and Dory swim away when they come across a predatory shark (though shark odour tracking may also be hindered in a more acidified ocean; see Dixson et al. 2014). However, in a more acidified ocean, as research has suggested, they may have done exactly the opposite and would likely have become dinner for the shark. Secondly, at the end of the movie, Nemo pops out of a sewer pipe and swims along, eventually finding his dad and Dory. Unfortunately, in a more acidified ocean, research suggests that Nemo likely wouldn’t be able to find his father.

Though I like to think that adult behaviour may not be altered and Marlin would have eventually found the dazed and confused Nemo (though other inaccuracies in the movie, if corrected for, would have led to Marlin and Dory’s demise, let alone a much more incestual tale), it is likely that the feel-good ending that we’ve all come to love would have been anything but feel-good. So we need to find ways of mitigating ocean acidification and saving our precious ecosystems from the myriad of destructive consequences that they will face if we continue our ways – not only for our own sake, but so that the Nemos of the future will have a chance to swim away from their predators or find their way home if they ever decide to venture away from their anemonemone.

REFERENCES:

Munday, PL et al. 2009. Ocean acidification impairs olfactory discrimination and homing ability of a marine fish. PNAS, 106: 1848-1852.

Dixson, DL et al. 2010. Ocean acidification disrupts the innate ability of fish to detect predator olfactory cues. Ecology Letters, 13: 68-75.

Simpson, SD et al. 2011. Ocean acidification erodes crucial auditory behaviour in a marine fish. Biology Letters, doi:10.1098/rsbl.2011.0293.

Nilsson, GE et al. 2012. Near-future carbon dioxide levels alter fish behaviour by interfering with neurotransmitter function. Nature Climate Change, 2: 201-204.

Dixson, DL et al. 2014. Odor tracking in sharks is reduced under future ocean acidification conditions. Global Change Biology, doi: 10.1111/gcb.12678.

Canada lagging behind in ocean acidification research and action

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scallop
The year was 2011, and Rob Saunders, CEO of Island Scallops, had some grim news to report from his scallop hatchery in Qualicum Bay, BC – every scallop the company had put in the water over the past 3 years had died. The likely culprit? – ocean acidification (OA). Seawater pH levels reaching 7.2 had been reported from the area, where typical seawater hovers around a pH of 8. Consequently, Island Scallops was forced to dramatically scale back production, shutting down its processing plant and laying off 1/3 of its employees.
Although often considered a future problem, OA is already impacting coastal systems on the Pacific coast of North America. Aside from the shellfish crises in the Northwest United States, and British Columbia, Feely et al. (2008) reported undersaturated seawater (with respect to aragonite; a mineral form of calcium carbonate) upwelling along the continental shelf of the Pacific coast of North America from Canada to Mexico. More recently, it has been suggested that these chemical changes in the same area are already resulting in negative biological implications at the base of the food web (Bednaršek et al. 2014). As a result of these immediate threats of OA, various committees and national projects have been formed to address and monitor OA in the United States, such as the NOAA Ocean Acidification Program (NOAA OAP), while documents outlining strategic plans for research, monitoring, and tackling the problem of OA in the US  have been published in recent years (e.g. OCBP 2009, NRC 2010, IWGOA 2014) (Europe is also leading the way in this area, but I will stick to North America for the purposes of this post; for a glimpse at the European Project on Ocean Acidification, EPOCA, see here). In fact, the United States federal government, through NOAA initiatives, has a total of 16 buoys/moorings monitoring OA in their national waters (10 on the Pacific coast, 6 on the Atlantic coast) (Figure 1).
Figure 1. Allocation of buoys/moorings monitoring ocean acidification in countries of the Pacific and Atlantic coasts of North America.
Figure 1. Allocation of buoys/moorings monitoring ocean acidification in countries of the Pacific and Atlantic coasts of North America.
While the US Federal government appears to be sufficiently concerned about OA, the Canadian Federal government seems much more disinterested. In their 2012 State of the Oceans report, Fisheries and Oceans Canada (DFO) reported that, due to its age, Pacific sub-surface water already contains a high concentration of CO2 and periodic episodes of undersaturated (pH<7.7) surface waters already occur on the Pacific coast of Canada (DFO 2012). In the report, DFO also stated that on the Atlantic coast of Canada, bottom waters in the St. Lawrence Estuary have dropped 0.2-0.3 units over the past 70 years (in comparison to the global average decrease of 0.1 units) resulting in biological implications for bottom-dwelling animals, and suggested that water from Arctic outflow moving through the Canadian Arctic Archipelago is bringing more acidic waters to the east coast of Canada, potentially making it more susceptible to future changes (DFO 2012). Although the report clearly outlines that ocean acidification is already a problem on both Canadian coasts and suggests that future conditions will get worse, the Canadian Federal government is doing very little to address OA in Canada, simply stating in the report that “Continued scientific research into ocean acidification is necessary to identify its impacts and drivers, which vary by location, with a view to developing a coherent response to the issue”. While 16 buoys are monitoring OA in US waters, Canada has a total of 1 (Pacific coast), which is itself a collaborative project with NOAA in the US (Figure 1). Canada has, however, been involved in the AMAP project which has contributed to monitoring Arctic OA, but the only other governmental OA research program in Canada is just getting off of the ground at a DFO lab in St. Andrews, New Brunswick; however, this program is very primitive and requires much more time, effort, and funding to appropriately establish an OA monitoring program on Canada’s east coast. When it comes to policy, OA isn’t even on the radar in Canada. Although, the President of the United States committed to protecting marine ecosystems of the US and tackling the problem of OA in June of 2014 (not to mention the myriad regional initiatives aimed at addressing the problem in the United States), the Canadian government has yet to mention the prospect of trying to mitigate the implications of OA in our country. While the United States have multiple, detailed documents outlining OA and potential adaptation strategies, the latest formal report outlining Canada’s action on climate change designates less than a page to OA (Warren & Lemmen 2014). Furthermore, although the Canadian government is abundantly proud of its ecoENERGY program (i.e., investing money into oil and natural gas exploration), the ecoACTION program (i.e., actively taking action against ecological problems such as climate change and ocean acidification) has been dismantled. Finally, although government agencies such as NOAA in the US and EPOCA in Europe have devoted a substantial amount of time into public outreach and education, government scientists studying OA in Canada are still struggling to speak outside of their offices.
The latest report from the Government of Canada outlining Canada's actions towards climate change restrict ocean acidification to less than a single page.
The latest report from the Government of Canada outlining Canada’s actions towards climate change restrict ocean acidification to less than a single page.
For the past decade or more, OA has been on the radars of scientists around the world. With its imminent threat to marine organisms around the world, from individual species to global biodiversity, acidification has been a hot topic, peaking the interest of scientists and (some) policy makers alike. Although disparately necessary, a global policy to address the threat of OA is lacking. Consequently, a disconnect exists between regions around the world, with some taking notice and action more than others. Although the United States has begun to lead the way in OA research and mitigation (along with numerous countries in Europe), it is quite clear that the Canadian Federal Government and associated policy makers are drastically lagging when it comes to acting on OA, a detrimental environmental issue the requires immediate attention. As a result, research into OA in Canada is drastically hindered and negative instances such as those at Island Scallops aren’t likely to be prevented for quite some time to come.

References:

Feely RA et al. 2008. Evidence for upwelling of corrosive “acidified” water onto the continental shelf. Nature, 320, 1490-1492.

Ocean Carbon and Biogeochemistry Program 2009. ocean acidification: Recommended strategy for a U.S. national research program [online]. Accessed 01/12/2014 from http://www.us-ocb.org/publications/OCB_OA_Whitepaper.pdf.

National Research Council 2010. Ocean acidification: A national strategy to meet the challenges of a changing ocean [online]. Accessed 01/12/2014 from http://hofmannlab.msi.ucsb. edu/resources/OA_A%20National%20Strategy%20to%20Meet%20the%20Challenges%20of%20a%20Changing%20Ocean.pdf.

Bednaršek N et al. 2014. Limacina helicina shell dissolution as an indicator of declining habitat suitability owing to ocean acidification in the California Current Ecosystem. Proc R Soc B, 281, DOI: 10.1098/rspb.2014.0123.

Fisheries and Oceans Canada 2014. Canada’s state of the oceans report, 2012 [online]. Accessed 01/12/2014 from http://www.dfo-mpo.gc.ca/science/coe-cde/soto/report-rapport-2012/index-eng.asp#a2.

Interagency Working Group on Ocean Acidification 2014. Strategic plan for federal research and monitoring of ocean acidification [online]. Accessed 01/12/2014 from http://www.whitehouse. gov/sites/default/files/microsites/ostp/NSTC/iwg-oa_strategic_plan_march_2014.pdf.

Warren FJ & Lemmen DS 2014. Canada in a changing climate: Sector perspectives on impacts and adaptation. Government of Canada, Ottawa, 286pp.

On the need to incorporate carbonate variability parameters in predicting the biological impacts of ocean acidification

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This post is published as an excerpt of a “Quo Vadimus” essay to be submitted to a special issue of the ICES Journal of Marine Science. I highly appreciate any criticisms and/or feedback on the article.

 
     Ocean acidification is expected to yield negative implications for a wide array of marine organisms in the near future, as average oceanic pH levels are projected to drop by 0.3-0.4 units by the end of the century (e.g. Orr et al. 2005, IPCC 2014). However, as with other processes affected by global climate change, variability in oceanic carbonate chemistry can also be expected to increase. For example, precipitation and temperature are expected to become more variable in the future, while the frequency and magnitude of extreme weather is expected to increase (Easterling et al. 2007, IPCC 2014). Consequently, environmental conditions within marine habitats may become more variable, including more pronounced fluctuations in marine carbonate chemistry.
     Although we can expect the variability of marine carbonate chemistry to increase in the future, oceanic pH is already highly variable both spatially and temporally, with coastal areas being the most dynamic of these systems. This variability can be primarily attributed to differences in ecosystem processes across systems. Although some studies suggest that interannual and seasonal surface ocean [CO32-] variability is negligible, except in higher latitudes (temporal and arctic regions) (Orr et al. 2005), others report fairly substantial variability. For example, a study by Dore et al. (2009) utilizing 20 years of time-series measurements suggested substantial interannual and seasonal variability, coupled with a long-term decrease in pH in the north Pacific, with seasonal trends driven primarily by changes in temperature, mixing, and the net assimilation of photosynthetic CO2.  Biological processes have also been suggested to drive seasonal variation in CaCO3 saturation states in the Arctic Ocean (Bates et al. 2009), while highly variable carbonate parameters have been recorded in California current systems (Hauri et al. 2009, Lienweber & Gruber 2013). The degree of variability in marine carbonate chemistry also varies within and among systems. For example, in the North Sea, it has been reported that a low degree of pH variability exists in biologically inactive areas (< 0.2), but a high degree of variability exists in coastal areas, particularly those around the mouths of rivers (Hinga 2002, Blackford & Gilbert 2005). Likewise, in Australia, degrees of pH variability have been shown to vary temporally and spatially, but specific trends are not always evident (Gagliano et al. 2010), while substantial variation in carbonate saturation has been reported from a Great Barrier Reef flat, although the impacts of such variability on coral calcification are unknown (Shaw et al. 2012). Sediments are also known to be highly variable with respect to carbonate geochemistry, varying by different degrees both spatially and temporally (Figure 1, Wenzhöfer 1999, Yates & Halley 2006). Annual patterns in carbonate geochemical variability have also been documented to correlate with cyclical trends in the abundance of benthic organisms (i.e., foraminiferans; Green et al. 1993). Rainfall can also impose drastic changes and substantial variability in sediments (Figure 1) and coastal systems (Doney et al. 2007), with negative relationships observed between rainfall and pH (i.e., increased rainfall, lower pH).
Figure 1. Daily (A) and bi-weekly (B) variability in surface sediment pH at three mudflats on the Bay of Fundy in southwest New Brunswick, Canada. Red arrow indicates significant rainfall event (>20 mm). Data source: Clements, unpublished data.
Figure 1. Daily (A) and bi-weekly (B) variability in surface sediment pH at three mudflats on the Bay of Fundy in southwest New Brunswick, Canada. Red arrow indicates significant rainfall event (>20 mm). Data source: Clements, unpublished data.
     Studies have provided a solid basis for understanding the complexities of marine carbonate variability. However, the ways in which these temporal and spatial trends (or lack thereof in some areas) will impact marine organisms at the various levels of biological organization are still unknown. Some studies have started to incorporate variability parameters into assessing the biological impacts of ocean acidification, suggesting that the effects of fluctuating carbonate chemistry are species specific, allowing organisms to adapt and persist or become more vulnerable in an acidifying ocean. A study conducted by Alenius & Munguia (2012) suggested that the intertidal isopod, Paradella dianae, although adapted to a high degree of variability because it lives in the intertidal zone, experiences behavioural and physiological changes under variable pH conditions compared to a stable, low pH environment, with variable conditions (low pH) yielding negative impacts on survival, oxygen consumption, and behaviour (significantly depressed swimming time and increased resting time). Cornwall et al. (2013) also observed significantly lower growth rates of coralline macroalgae under variable pH conditions relative to static conditions. On the positive side, Default et al. (2012) have reported beneficial effects of fluctuating pCO2, reporting increases in growth and survival of coral recruits under naturally-fluctuating levels of pCO2. Similarly, when assessing the impacts of static and variable pH (O2 was also assessed, but ignored here), Frieder et al. (2014) reported that low pH treatments incorporating variability resulted in quicker transitions from trochophore to veliger larvae and larger (and less variable) larval shells compared to static low pH conditions for two species of mussels (Mytilus galloprovincialis and M. californianus). Although they did not directly test the impacts of variability on animals, Shaw et al (2013b) have outlined to importance of carbonate variability on the exposure time of marine organisms to conditions either above or below current and projected means.
Figure 2. Relative percentages of studies assessing the biological impacts of ocean acidification (n=414) incorporating only static means in carbonate parameters, and those incorporating variability in carbonate parameters. Data were obtained from a preliminary ISI Web of Science search using the keyword “ocean acidification”.
Figure 2. Relative percentages of studies assessing the biological impacts of ocean acidification (n=414) incorporating only static means in carbonate parameters, and those incorporating variability in carbonate parameters. Data were obtained from a preliminary ISI Web of Science search using the keyword “ocean acidification”.
     The vast majority of studies assessing the biological consequences of ocean acidification focus their efforts on organisms raised under or exposed to static conditions based on mean predicted near-future acidification scenarios (Figure 2). Furthermore, although research has started to shift toward assessing the biological impacts of near-future OA conditions in the context of other environmental factors (e.g., multiple factors; temperature, salinity, oxygen, etc.), they have yet to focus on understanding the impact of acidification on marine fauna in the context of current and future marine carbonate variability. Because carbonate variability can modulate an organism’s duration of exposure to carbonate conditions above, at, or below current and projected means, as well as increase the extremes that the organism experiences, variability may offset the negative effects of ocean acidification, or amplify them. Since the time spent in conditions yielding biological effects is likely increase over time, along with the extremes of these conditions (Figure 3, Shaw et al. 2013a), it would be expected that future marine carbonate variability would result in more pronounced biological effects. Of the four studies directly relating carbonate variability to biological effects, two suggested that variability will act to modulate the impacts of ocean acidification (Default et al. 2012, Frieder et al. 2014). However, it is important to recognize these studies use current degrees of variability as the basis for future variability, which may be inaccurate. As such, the duration and extremes of the conditions that the animals in those two studies were exposed to could have confounded their results, as the tested duration and extremes of conditions may not have accurately depicted those of actual future scenarios (Figure 3). As such, an accurate understanding of how carbonate variability will transpire in the future, along with how marine organisms will respond to current and near-future acidification is of utmost importance for understanding the true biological impacts of ocean acidification.
Figure 3. Potential degrees of current and projected variability in diurnal oceanic pCO2 where variability increases over time (A) and where variability remains consistent over time (B). Distance between dashed lines indicate the relative amount of time organisms would be expected to spend above thresholds where they would be impacted by ocean acidification. Patterns of variability across ecosystems will differ as a result of differing types and magnitudes of various processes across systems. Adopted from Shaw et al. 2013.
Figure 3. Potential degrees of current and projected variability in diurnal oceanic pCO2 where variability increases over time (A) and where variability remains consistent over time (B). Distance between dashed lines indicate the relative amount of time organisms would be expected to spend above thresholds where they would be impacted by ocean acidification. Patterns of variability across ecosystems will differ as a result of differing types and magnitudes of various processes across systems. Adopted from Shaw et al. 2013.
Figure 4. Percentages of positive and negative biological effects of carbonate variability in ocean acidification studies incorporating variability around mean carbonate conditions (n=4).
Figure 4. Percentages of positive and negative biological effects of carbonate variability in ocean acidification studies incorporating variability around mean carbonate conditions (n=4).
     Although the current data on how variability around current and future carbonate geochemical means suggest that marine carbonate variability will have differential effects on different species (Figure 4) and that the magnitude of the effects of ocean acidification may be more or less pronounced under variable conditions (in comparison to static conditions), the number of studies that have attempted to address variability parameters in biological ocean acidification studies is negligible and insufficient to draw any generalizations. As such, it is critical that ocean acidification research, in the context of biological impacts, begins to understand current and projected localized and broad-scale variability in marine carbonate systems to accurately predict how organisms will respond under future acidification scenarios. It is also apparent that studies focusing on the biological impacts of ocean acidification need to begin understanding how the degree of marine carbonate variability is going to change with an increasingly acidifying ocean in the myriad of systems that will be impacted by ocean acidification. Understanding whether or not the variability in the marine carbonate system is going to increase, decrease, or remain the same under future climate change scenarios is imperative for predicting how marine organisms will respond to an acidifying and warming ocean. Ultimately, because ocean acidification studies focus on stable conditions under near-future predictions, our current understanding of how acidification will impact marine organisms is very limited, rendering it critical to begin understanding how acidification will affect these organisms in the context of variability around the projected means, as well as in the context of other environmental factors and their associated variabilities.

References

Alenius B & Munguia P 2009. Effects of pH variability on the intertidal isopod, Paradella dianae. Mar Freshw Beh Phy, 45, 245-259. doi: 10.1080/10236244.2012.727235.

Bates NR et al. 2009. Ocean acidification and biologically induced seasonality of carbonate mineral saturation states in the western Arctic Ocean. J Geophys Res, 114, C11007. doi: 10.1029/2008JC004862.

Blackford & Gilbert 2005. pH variability and CO2 induced acidification in the North Sea. J Mar Sys, 64, 229-241. doi:10.1016/j.jmarsys.2006.03.016.

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Acid trip: ocean acidification alters marine animal behaviour

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Ocellaris clownfish, Amphiprion ocellaris
Ocellaris clownfish, Amphiprion ocellaris. Photo: Wikipedia
When assessing the impacts of ocean acidification (OA) on marine animals, peer-reviewed studies predominantly address the mortality and physiology of these organisms. However, over the past few years, it has become apparent that animal behavior can also be altered under increasingly acidifying conditions.
A recent study by Sue-Ann Watson and colleagues at James Cook University in Australia demonstrated that near-future CO2 levels can interfere with neurotransmitter functioning (i.e., chemical functioning of the brain), leading to a 50% decrease in predatory escape behavior in a species of marine gastropods, making them more susceptible to being eaten by predators in high-CO2 conditions. Studies have also suggested shifts in the behavior of various fishes, including increased anxiety in rockfish, hindered hearing behavior in clownfish, and reduced swimming behavior in dolphinfish, with the likely mechanism being hindered neurotransmitter functioning. Some of these observations in fishes have also been translated to invertebrate organisms as well. Alongside these behavioural modifications under acidic water-column conditions, some interesting research on the east coast of North America has also been suggesting that juvenile clams can change their behavior in response to increased acidification as well, except in this case, the clams respond to sediments and not the water column.
If exposed to acidic conditions for a long enough time period, the shells of living molluscs begin to dissolve and can ultimately lead to their death.
If exposed to acidic conditions for a long enough time period, the shells of living molluscs begin to dissolve and can ultimately lead to their death. Photo: J. Clements
Before they mature and dig into sediments at the bottom of the ocean in coastal areas, clams go through what is called a larval stage, where they swim around and develop in the water column (this is akin to a caterpillar and a butterfly – the caterpillar is the larvae and the butterfly is the mature). After a certain period of time, the larval clams will sink to the bottom to start their life as mature animals. However, before they dig into the sediment to start the next stage of their life, they can test the chemistry of the sediment and make a decision as to whether or not it is an appropriate place to live. So if they don’t like the initial place where they land, they can refuse to burrow into it and may be able to move to a different area.
Recent research has suggested that the acidification of these sediments may impact the behavior of these clams in their decision to dig or leave. One study conducted by Mark Green and colleagues at St. Joseph’s College in Maine, USA assessed the impact of increasing acidification within marine muds on the burrowing behavior of juvenile quahogs (Mercenaria mercenaria).
By manipulating the level of acidity in different containers of soft-sediment and watching whether or not clams burrowed into them, the scientists were able to determine that as the sediment becomes more acidic, the clams reject it and don’t burrow – the first time that acidification was found to have an impact on clam burrowing behavior.
Given this interesting result, researchers at the University of New Brunswick in New Brunswick, Canada wanted to see if this lack of burrowing actually resulted in the clams moving away. By taking the same approach as Green and colleagues, only with a different species of clam (soft-shell clam, Mya arenaria), myself and Dr. Heather Hunt (see “Publications” to download a PDF) observed the same trend of burrowing behavior that Green and colleagues did in their study – more acidic sediments had less clams burrowing. However, by adding flowing water to the experiments (a means by which soft-shell clams move), we were able to determine that when sediment was more acidic, more clams left than when sediment was not as acidic.
At high levels of acidification (low values of Ωaragonite on x-axis), fewer clams burrow into sediments (left panel), while more clams move away (right panel). Source: Clements & Hunt (2014)
At high levels of acidification (low values of Ωaragonite on x-axis), fewer clams burrow into sediments (left panel), while more clams move away (right panel). Source: Clements & Hunt (2014)
The combined results of our study and those of Green and colleagues provide evidence that the acidification of marine soft-sediments can influence the behavior and population dynamics of juvenile clams by altering their decision to burrow and subsequently their dispersion. Since acidic conditions dissolve the shells of these animals and result in death, this could be the reason why the clams decide to move away from these acidic muds. Other reasons are possible, however. For example, increased concentrations of CO2 may depress other physiological functions such as respiration, metabolism, or feeding, which would also contribute to the negative burrowing cue (recruitment cue) detected in these two studies.
Juvenile soft-shell clams used in the Clements & Hunt (2014) study. Bivalves are most susceptible to the impacts of OA in their early life stages. Photo: J.Clements
Juvenile soft-shell clams used in the Clements & Hunt (2014) study. Bivalves are most susceptible to the impacts of OA in their early life stages. Photo: J.Clements
These studies, along with others, highlight the impact of ocean acidification on the behavior of marine-dwelling animals. Changes in behavior have the potential to impact these animals in both positive and negative ways.
The bright side, at least for clams, is that if they can avoid more acidic sediments and move to better ones,  they enhance their chances of avoiding “death by dissolution” or other stressful conditions, so long as there is enough suitable mud available! However, by not burrowing immediately, the clams do put themselves at a higher risk for other mortality factors, such as predation. Ultimately, scientists have much work to do in determining how the future chemistry of our oceans could impact the behavior of marine organisms and how this could in turn influence their survival.

Shallow secrets of ocean acidification: Current coastal consequences

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The close relationship between atmospheric CO2 and oceanic CO2 and the ensuing drop in pH at Mauna Loa, Hawaii, suggest that increasing atmospheric CO2 is driving the acidification of our oceans.
The close relationship between atmospheric CO2 and oceanic CO2 and the ensuing drop in pH suggest that increasing CO2 is driving the acidification of our oceans. Source: Doney et al. 2009.
Known as “the other CO2 problem”, ocean acidification (OA) has crept onto the scene as one of the most menacing and destructive aspects of human-induced climate change. Basically, OA refers to the dissolving of atmospheric carbon dioxide (CO2) into the oceans, making them more acidic and spelling trouble for many marine organisms, particularly those with calcium carbonate (CaCO3) skeletons (e.g., pteropods, clams, snails, corals). Since the Industrial Revolution, the pH of the oceans has dropped from ~8.2 to ~8.1, corresponding to a 30% increase in ocean acidity, with a projected 0.3-0.4 further decrease by 2100 (120-150% increase in acidity). Ultimately, OA could result in major losses to marine biodiversity, threatened food sources for a myriad of organisms (including humans), diminished coastal protection, altered food webs and ecosystem structuring, and an interrupted carbonate system (Hardt & Safina 2008). However, OA is typically attributed to the burning of fossil fuels and the human contribution to atmospheric CO2. As a result, this can be misleading when reporting the effects that ocean acidification is having in coastal waters and those that it could have in the near future.
Recently, open-ocean acidification has been distinguished from that of coastal waters on the basis that acidification in coastal regions is functionally much different than that of the open ocean (Duarte et al. 2012). As a consequence, the pH decrease in coastal waters (particularly in estuaries) is much more pronounced than that of the open-ocean, and the variability of pH ranges is much wider. Furthermore, although atmospheric CO2 is the primary driver in open-ocean acidification, it plays less of a role in coastal systems. Instead, coastal upwelling, terrestrial and freshwater runoff, organic decomposition, and other processes not occurring in the open-ocean can act as the primary drivers of acidification in coastal systems to varying degrees. As such, organisms residing within coastal waters are subjected to extremely stressful conditions for the majority of their life.

Historically, OA studies have manipulated seawater conditions to mimic future open-ocean acidification scenarios and measured the response of various organisms to these future conditions. However, to the surprise of scientists and shellfish growers alike, the changes in seawater chemistry in coastal areas (particularly the west coast of North America) and resultant biological and economical consequences are happening right now! Shellfish hatcheries on the west coast of North America have already felt the effects of OA. In 2005-2006, shellfish growers on the west coast of the United States were experiencing mass mortality of larvae in their tanks and couldn’t figure out why. When scientists equipped the tanks with pH meters and saw that it was critically low, they were able to come up with solution strategies that worked and, in essence, saved the shellfish industry in parts of the Pacific US. More recently, the loss of approximately 10 million scallops in British Columbia at Island Scallops in 2013 and a financial loss of $10 million (and the forced lay-offs of numerous staff has been attributed to a change in pH from 8.1 in 1953 to a low of 7.3 in 2001. Furthermore, a recent study published in the journal Proceedings of the Royal Society B has reported that 53% of pteropods on the US Pacific coast had severe dissolution of their shells (Bednaršek et al. 2014).
Shell dissolution in larval oysters raised at hatcheries on the Pacific coast of North America has resulted in mass mortality events over the past 10 years. Photo courtesy of Taylor Shellfish from OSU.
Shell dissolution in larval oysters raised at hatcheries on the Pacific coast of North America has resulted in mass mortality events over the past 10 years. Image courtesy of Taylor Shellfish from OSU.
Given the magnitude and obvious immediacy of OA, understanding how this process is currently impacting coastal waters is critical. Alongside the anthropogenic sources of acidification in coastal zones mentioned above, natural causes of acidification and other physical changes (e.g., temperature, salinity, oxygen concentration, etc.) must also be taken into account when addressing acidification in coastal areas. The complex interactions between all of these factors make the task of predicting their effects on coastal ecosystems magnificently daunting. What is apparent, however, is that the pronounced acidification of coastal waters is having and will have significant consequences, not just for the organisms living in these ecosystems, but for humans as well. The overwhelming majority of the global human population depends on coastal ecosystems for survival. With coastal acidification affecting marine organisms both directly and indirectly (indeed acidification will affect more than CaCO3-bearing organisms; e.g., food web shifts and trophic cascades affecting fishes and mammals), a major source of food for billions of people is in jeopardy. Ultimately, scientific studies addressing the impacts of OA need to take the plethora of physical into account in order to sufficiently predict how coastal ecosystems are going to react to the changes that humans are imposing on them. Furthermore, studies need to start focusing more on the current impacts of OA rather than the biological impacts of future scenarios. More importantly, the general public needs to know about the implications of acidification in coastal areas to put the brakes on coastal acidification before things become drastically worse.

References:

Bednaršek, N. et al. 2014. Limacina helicina shell dissolution as an indicator of declining habitat suitability due to ocean acidification in the California Current Ecosystem. Proceedings of the Royal Society B 20140123.
Doney, SC. et al. 2009. Ocean acidification: A critical emerging problem for the ocean sciences. Oceanography 22: 16-25.
Duarte, CM. 2013. Is ocean acidification an open-ocean syndrome? Understanding anthropogenic impacts on seawater pH. Estuaries and Coasts 10.1007.
Hardt, M. & Safina, C. 2008. Covering ocean acidification: Chemistry and considerations. [online]. The Yale Forum on Climate Change and the Media. Accessed 07 May 2014 from http://www.yaleclimatemediaforum.org/2008/06/covering-ocean-acidification-chemistry-and-considerations/.