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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.
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Is de-extinction really a good idea?

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Given the current sequencing of its genome, the woolly mammoth (Mammuthus primigenius) is a top candidate for de-extinction.
Given the current sequencing of its genome, the woolly mammoth (Mammuthus primigenius) is a top candidate for de-extinction.
In March of 2013, a group of scientists gathered in Washington, D.C. at the TEDxDeExtinction meeting and proposed the idea of de-extinction. Yes, de-extinction is exactly what it sounds like – bringing extinct species back to life using genetic tools (biotechnology) to recreate (clone) various extinct organisms from their reassembled DNA. The idea is both exciting and interesting; however, given some of the ideas brought forward regarding such an undertaking, perplexity as to why we would bother bringing back extinct species rather than trying to preserve extant ones becomes apparent.
The concept is surely intriguing and would be one of the greatest achievements science has ever accomplished, but the idea brings forth many questions as well – particularly when it comes to ecology. For instance, how would the ‘resurrection’ of extinct species like the dodo or the woolly mammoth alter current ecosystem structure and, if we do have a grasp on how the re-introduction of these species would affect current ecosystems (which, for some, we do), will the changes be acceptable in terms of ecosystem stability and sustainability? In other words, will current ecosystems be able to sustain these organisms, given that these systems are drastically different from when such extinct organisms existed; will the current state of these systems remain stable with the introduction of these new (yet old) species? Furthermore, are we, as humans, willing to accept the associated consequences of bringing back an extinct species that simply appears “cool” or interesting?
An example of the basic concept of bringing extinct animals back to life.
An example of the basic concept of bringing extinct animals back to life.
Releasing these recreated species into the wild is easily comparable to releasing an invasive species into a novel ecosystem, and the consequences of doing so are often devastating. Of course, some of these species may have the ability to enhance biodiversity and other such metrics of ecosystem health, in which it may be beneficial to reintroduce them; but why not use these de-extinction techniques to enhance current ecosystems supporting extant organisms rather than reviving previously existing ones? Bringing back extinct species could also allow for the exploration into how these species initially became extinct, which could aid in enhancing conservation efforts for current species, whether endangered, threatened, or at risk. In artificial scenarios, these organisms could be utilized to make better predictions regarding how some extant organisms, even our own species, may be influenced by future climatic conditions or other potential extinction events. However, ethical implications then arise – do we establish populations of these organisms or just keep exposing them to conditions inducing extinction to better understand future scenarios/implications (i.e., do we keep them alive or just keep killing them)?
Stewart Brand revisiting the Conservation Pledge during his TEDTalk ‘The Dawn of De-extinction’ (photo credit: Jurvetson, Flickr).
Stewart Brand revisiting the Conservation Pledge during his TEDTalk ‘The Dawn of De-extinction’ (photo credit: Jurvetson, Flickr).
Additionally, to use the recreated organisms for this purpose, artificial ecosystems must be manufactured. Creating artificial ecosystems to bring back these organisms to life makes sense, but the historical ecosystem complexity that existed such a long time ago must be recreated with accuracy. This may not be difficult for some species, but for others it would – all this without mentioning the financial costs associated with such studies and how many species of other organisms that would have to be brought back in order to create these complex systems (many of which we don’t have the DNA for). Other questions also arise with keeping such complex populations/systems in concealment. For example, reproduction and mortality rates of revived species would have to be taken into account to sustain a confined population. If populations are to be sustained, these organisms will eventually have to be released, in which the slurry of ecological problems mentioned above then arise.
Although a ‘Jurassic Park’ scenario is not yet within our reach (nor is it likely to be), the ecological consequences of introducing genetically manufactured species which do not belong in a given ecosystem may be more detrimental than beneficial. The prospect of de-extinction is indeed interesting and stimulating, but much more thought regarding the ecological consequences of sustaining populations of such organisms must be established, and we must better understand the  beneficial or detrimental implications of such an endeavor. Clearly defining the purpose of implementing this type of technology must be well entrenched before woolly mammoths or kakapos are released into the wild along with the current flora and fauna.

Citizen science: the good, the bad, and the useful

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In science, we rely on rigorously collected, tested, and criticized data to make the best informed decisions about natural phenomena that we possibly can. These data are most often collected by the scientists themselves (or, of course, their graduate students). However, one often untapped resource that has been emerging for some time is citizen science. Citizen science comes in many forms – public citizens can actively engage with scientists in the collection of data, can contribute data to online databases and participate in large-scale studies, or can bestow years of personally collected data to scientists, who can then analyze it to understand trends in (most often) small-scale phenomena.
eButterfly allows citizens to record detailed information regarding butterflies seen in North America in an attempt to understand broad patterns of abundance and distribution. Photo: J. Clements
eButterfly allows citizens to record detailed information regarding butterflies seen in North America in an attempt to understand broad patterns of abundance and distribution. Photo: J. Clements
Some larger examples of citizen science utilize online databases such as eButterfly, EyeWire, Digital Fishers, EteRNA,and Project Squirrel to name a few, in which citizens engage in specific tasks to help scientists answer interesting and important questions about various aspects of science. Indeed, smaller scale versions of these databases also exist. For example, in Nova Scotia, the provincial government has initiated an online database for people to record the number and species of bats that they see in the province, aiding in bat conservation in Atlantic Canada; an immediate concern given that white nose syndrome (a fungal infection) has devastated the abundances of 3 species of bats in the region, reducing their populations by 95-99% over the past 4 years.
Public citizens can also directly associate with scientists to help collect data regarding important scientific information. For example, in many countries around the world, including Australia, Canada, Ireland, New Zealand, Portugal, Spain, Taiwan, Trinidad & Tobago, the UK, and the USA, citizens can participate in BioBlitz projects, which involve intense sampling of biological data in an attempt to record all living species in a defined area, from plants and animals to fungi and lichens. Additionally, many geographic areas partake in annual Christmas Bird Counts, in which citizens and scientists count the number of birds in a defined area to understand their biodiversity and abundances. Other examples include the submission of data from citizens themselves for scientific use. In 2012, the UNESCO Fundy Biosphere Reserve in New Brunswick, Canada, initiated a citizen-sourced climate data project. One couple, the Whitneys, submitted 40 years of data that they had personally collected on their property, which was utilized by scientists at Mount Allison University to assess over 40 years of microclimatic data.

White Nose Syndrome, a fungal disease in bats, has decimated the populations of 3 species of bats in Atlantic Canada by 95-99%. Citizens in Nova Scotia can help to conserve them by reporting sightings on an online database. Photo: USFWS Headquarters, Flickr Creative Commons
White Nose Syndrome, a fungal disease in bats, has decimated the populations of 3 species of bats in Atlantic Canada by 95-99%. Citizens in Nova Scotia can help to conserve them by reporting sightings on an online database. Photo: USFWS Headquarters, Flickr Creative Commons
Although citizen science may sound like a universally useful tool, it does provide challenges. As stated earlier, science requires rigorous and often systematically collected data in order to answer specific questions. Using publicly collected data does not always meet these criteria. As such, measures must be taken to ensure the accuracy and validity of citizen collected data. Moreover, publicly collected data is often messy and inconsistent, making analyses quite difficult. Ultimately, data collected by public citizens is highly useful, but precautions must be taken and measures implemented to ensure that publicly collected data is accurately answering the question of interest.
Overall, citizen science can be a highly useful tool, aiding scientists in answering key scientific questions. Citizen science is particularly useful in studies of conservation and climate change, allowing scientists to understand the abundances and distribution of various organisms in response to a changing climate. With the proper measures to ensure the accuracy, validity, and usefulness of publicly collected data, the rate at which scientists can gain insight into large, broad-scale questions and trends can be emphatically enhanced; a feat which is critical in this period of immense and rapid global change.
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If you would like to participate in or learn more about any of the above-mentioned citizen science projects, simply click the hyperlinks. Other projects do exist; visit SciStarter for more information, or if you would like to find out more about local citizen science projects in your area, contact your local university or science museum.

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/.

Is it time for scientific language to change?

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dnasequence_Flickr_JohnGoode
DNA Sequence (Flickr Creative Commons: JohnGoode)
“But evolution is just a theory!” A common argument heard all too often from staunch opponents of Evolutionary Theory. However, evolution is the fundamental theory essential to modern-day biology – without it, our biological understanding of the world crumbles. So if the entirety of our understanding about biology rests on the back of a “theory”, how can we be sure that we know much about biology at all?
Just a theory; Just a theory… If you want to make a biologist cringe, tell him or her that evolution is just a theory. Yet, if you told a random stranger on the street that evolution is ‘just a theory’, they would probably agree with you and disregard its validity. This suggests that the definition of “theory” means something much different to a biologist than it does to a non-biologist. But “theory”, at least in ecology, really only has has a single definition; so why the discrepancy? The answer inherently lies in the interpretation of “proof”.
In science, with the exception of mathematical proofs, nothing can be “proven”. That is, 100% proof of something cannot be obtained. This is because science works on the principle of disproving prior ideas. As ideas are tested, and are failed to be disproved, they gain more and more evidential support for their existence and truth. Once enough evidence supporting the reality of an idea surmounts, that idea becomes a theory. As science continues to test a theory and continues to fail disproving it…it stays a theory. But why? If so much evidence supports a theory, why does it never become a fact? This is because there is always a chance that even the most well supported theories could be disproved. As unlikely as it may be, science must rest on the idea that all theories have the potential to be disproved.

Theory; Theory… But if something has the potential to be disproved, doesn’t that mean we’re unsure about its truth? Sure, if that something has very little evidence supporting it. But when something has a lot of evidence weighted overwhelmingly in one direction, the confidence we can exude in expressing its truth increases. Take a homicide investigation, for example, where the suspect was seen running out of a murder victim’s house 30 seconds after shots were fired, carrying a gun and covered in blood. Upon investigation, the man’s blood-covered clothes were retrieved down the street from the crime scene and DNA analysis confirms that the blood on the clothes was that of the victim. The suspect has no alibi and footprint analysis confirms that it was indeed the suspect who ran out of the victim’s house after the shots were fired. Several hours later, the police get a confession from the suspect that he/she committed the murder. Now, there is a chance that the suspect was inside the house saying hello to the victim, someone else shot the victim, covered the suspect in blood, the suspect stole the gun from the killer, ran away, ditched the clothes because they were dirty, and confessed because the police forced a confession; but this is a very unlikely scenario. In a homicide case as clear-cut as this, the evidence would “prove” that the suspect was guilty and would face the subsequent consequences.
Scientific language is often lost on the general public (Flickr Creative Commons: AJCann)
Scientific language is often lost on the general public (Flickr Creative Commons: AJCann)
The overwhelming evidence in the homicide example above is akin to the amount of scientific evidence supporting Evolutionary Theory. Although the suspect in the homicide would be “proven guilty”, scientists are reluctant to say that evolution (or any other theory for that matter) is proven. In essence, this is contributing (but is not the only contributor) to the lack of understanding amongst the general public as to what a scientific theory really is, and opponents of solid scientific theories (e.g., evolution and climate change) often manipulate the word “theory” to undermine scientific understanding. As Neil deGrasse Tyson says, “The theory of evolution, like the theory of gravity, is a scientific fact!” A theory is a fact! Yet the general public all too often grasps the word theory as something that is untrue, unsure, and extremely likely to change – this is not the case.
So is it time for science to shift its use of the word theory to something that can’t be manipulated to undermine concrete scientific concepts? Maybe, but science is the closest that we, as humans, can get to complete objectivity. Although absolute objectivity cannot be obtained, science allows us to try and explain how the world works with as little human bias as possible. As such, keeping some degree of skepticism, however small that degree might be, is critical to the faculty of science. Consequently, this minute degree of skepticism will always be exploited by those who argue against scientific reasoning. Ultimately, scientists should try and do a better job of communicating their science in a clear and concise way to keep the general public informed of the solidity of such “theories”, while the school system must equally inform children of what a scientific theory really is and why we know that “theories” are true accounts of the way certain things work.
But this is just a theory…