It is actually with some sadness that I write what will be (for now!) my last post for this blog that I have been keeping as part of the 'Global Environmental Change' course I have been taking at uni...I have thoroughly enjoyed writing it and have learnt a great deal about our oceans and how they are responding to increasing environmental stressors as a result of climate change and other human-induced changes.
Before writing this blog, I must admit that I was fairly unaware of the harm we are doing to the planet's oceans; as I said way back in my first post, the first thoughts of many people when the words 'climate change' are mentioned are the depletion of the ozone layer and melting sea ice...
That's not to say that these things are unimportant (far from it!) but with the oceans covering 70% of the Earth's surface and with 80% of life depending on healthy coasts and oceans, their importance is abundantly clear. Humanity is changing the nature of our oceans in a way that is unprecedented in the Earth's history. Throughout this blog I have explored issues such as increasing sea temperatures, acidification, coral bleaching and the mounting problem of plastic pollution in our oceans. All of these changes are affecting ocean ecosystems and with the ocean being so vast, the full effects are simply immeasurable. I think this is perhaps the most worrying problem of all: that we do not know the ocean's ability to cope with such changes nor what the future holds, we can only make predictions...
We have now recognised that serious efforts must be made in order to curb humanity's impact on the planet and for the first time in history, over 200 countries have reached a consensus on how to attempt to limit global temperature increase to 2 degrees Celsius or less above pre-industrial levels. Whether or not this can be achieved still hangs in the balance.
There are many organisations (some of which I have written about) that are dedicated to ocean protection and conservation though we still need recognition of the issue on a global scale.
Surprisingly, it is some of the smallest island nations that are making the biggest changes in order to protect the ocean. The Pacific island nation of Palau has created landmark legislation which closes off 80% of its marine zone and in doing so, creates a vast ocean sanctuary. This area is larger than California (roughly 193, 000 square miles) and is the largest protected ocean zone in the world.
Research has shown that creating large protected marine areas can help quell the effects of climate change by allowing marine populations to increase and for vulnerable species' populations to stabilise. It is hoped that these benefits can spread to other parts of the ocean.
Palau is just one of several island nations working with The Pew Charitable Trusts' Global Ocean Legacy campaign that is seeking to establish more fully protected marine reserves. There are plans for a marine park around Easter Island and last March, the UK government announced plans to establish a huge marine reserve around the Pitcairn Islands.
But even with these commitments, the fact remains that less than 2% of the ocean is highly protected and marine scientists argue that this figure needs to be at least 30% to have a significant impact on its health.
With the oceans playing a role in the planet's climate and providing many fundamental ecosystem services, we can only begin to mitigate the effects of climate change, if we begin by repairing the damage to the oceans.
Sea Change
Investigating the impacts of environmental change on our oceans
Sunday, 10 January 2016
Saturday, 9 January 2016
Definite evidence for the Anthropocene?
Slightly off-topic but nonetheless still part of the wider theme of global environmental change, I came across this paper published yesterday which argues that the Anthropocene is 'stratigraphically distinct from the Holocene and earlier epochs'.
There has been much debate as to whether the pervasive impacts of humans on our planet warrant recognition as a new geological era which has been assigned the name of 'The Anthropocene'. Now, the authors of the paper say there is unmistakable evidence for the definition of a new era, unique to the rest of the Holocene.
They explain that 'recent anthropogenic deposits contain new minerals and rock types, reflecting rapid global dissemination of novel materials, including elemental aluminium, concrete and plastics that form abundant, rapidly evolving "technofossils".' They also argue that there are clear geochemical signatures in sediments and ice cores, for example, elevated levels of hydrocarbons and polychlorinated biphenyls. The modification of both the carbon and nitrogen cycles, rates of sea-level rise and accelerating extinctions are also cited as evidence for a stratigraphically distinct era.
There has been much debate as to whether the pervasive impacts of humans on our planet warrant recognition as a new geological era which has been assigned the name of 'The Anthropocene'. Now, the authors of the paper say there is unmistakable evidence for the definition of a new era, unique to the rest of the Holocene.
They explain that 'recent anthropogenic deposits contain new minerals and rock types, reflecting rapid global dissemination of novel materials, including elemental aluminium, concrete and plastics that form abundant, rapidly evolving "technofossils".' They also argue that there are clear geochemical signatures in sediments and ice cores, for example, elevated levels of hydrocarbons and polychlorinated biphenyls. The modification of both the carbon and nitrogen cycles, rates of sea-level rise and accelerating extinctions are also cited as evidence for a stratigraphically distinct era.
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| A sediment core from west Greenland with distinct layers of proglacial sediment and non glacial organic matter as a result of glacier retreat due to global warming. The dotted line represents the onset of the Anthropocene. (Source: https://www.sciencemag.org/content/351/6269/aad2622) |
Friday, 8 January 2016
New 'super' corals to tackle climate change?
Scientists in a research centre in Hawaii are developing new 'super' corals in an attempt to tackle the escalating problem of coral bleaching. It is hoped that these new corals will be better able to cope with warmer and increasingly acidic waters which are occurring as a result of global warming.
The team, led by Ruth Gates (director of the Hawaii Institute of Marine Biology) on the 29 acre Coconut Island, gradually expose corals that have already been identified as having strong genes to water which mimics the changing conditions of the ocean. In addition, they are also breeding more resistant coral with each other in order to enhance the traits of future strains in a process known as assisted evolution.
Although the theory has been used on other animals and plants, this is the first time it has been applied to coral. It's the team's hope that the new resilient corals will grow healthily and reproduce next summer however, they know that success on a local scale doesn't necessarily mean reproducibility on a global scale which is ultimately what is needed to address the problem of coral bleaching. It has been estimated that 30% of the world's coral reefs have already been lost as a result of the combined effects of warmer waters, acidification and the effects of El Nino.
Although leading marine biologists from NOAA suggest the project is scalable, there are doubts as to whether it can be implemented quickly enough...can we save our coral reefs before it's too late?
The team, led by Ruth Gates (director of the Hawaii Institute of Marine Biology) on the 29 acre Coconut Island, gradually expose corals that have already been identified as having strong genes to water which mimics the changing conditions of the ocean. In addition, they are also breeding more resistant coral with each other in order to enhance the traits of future strains in a process known as assisted evolution.
Although the theory has been used on other animals and plants, this is the first time it has been applied to coral. It's the team's hope that the new resilient corals will grow healthily and reproduce next summer however, they know that success on a local scale doesn't necessarily mean reproducibility on a global scale which is ultimately what is needed to address the problem of coral bleaching. It has been estimated that 30% of the world's coral reefs have already been lost as a result of the combined effects of warmer waters, acidification and the effects of El Nino.
Although leading marine biologists from NOAA suggest the project is scalable, there are doubts as to whether it can be implemented quickly enough...can we save our coral reefs before it's too late?
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| Juvenile 'super' corals ready for transplantation (Source:http://d1udmfvw0p7cd2.cloudfront.net/wp-content/uploads/2015/11/f-coral-a-20151107.jpg) |
Giant North Sea dam to combat problem of ocean plastic?
A little while ago, I wrote a number of posts on the growing problem of plastic waste in our oceans and what is being done about it, including the development of large, plastic-collecting, floating barriers by the organisation, Ocean CleanUp. Now, the organisation's founder, Boyan Slat, whose technology has already been trialled in Dutch lakes and in Japan, is installing a revolutionary 328ft giant 'dam' in the North Sea next year. The barrier, which will be installed some 14 miles off the coast of the Netherlands, will trap plastic waste floating in the sea using giant buffers while allowing fish and other sea creatures to safely pass through underneath.
This will be the first time that the technology will be tested in open waters and will provide an opportunity to measure the effects of waves and currents on the barrier using cameras and sensors. If successful, Ocean CleanUp hope to install other floating barriers around the world, with plans for a 100km long v-shaped one in the 'Great Pacific Garbage Patch' where large volumes of plastic rubbish collect. The company estimate that once installed, the barrier could collect around 42% of the plastic in this area over 10 years, representing a phenomenal 70, 320, 000kg of plastic!
The video below shows what the organisation do:
However, not everyone is convinced of the project's feasibility with many condemning the giant barriers as unsupported by scientific research and as a quick-fix to a problem of a colossal scale. It is argued by some that the barriers will quickly become colonised by sea life such as barnacles, fish and sea birds which when coupled with salt from the ocean, could spell disaster for the functionality of the equipment. Another issue is that the tiny organism, plankton, which have no control over their movements, would essentially be caught up in the currents directing the removed plastic into the recycling containers...with plankton so vital to the food chain this could be a huge problem with the barriers and Slat himself admits that more research is needed on this.
There are also issues with the economics of the project as the plastic, once collected, will need to be sorted into its various types and with many of the plastic pieces on a very small scale, analysis will be costly and time consuming. Moreover, there are arguments that the barriers will not collect anywhere close to the volume suggested by the organisation as their figures are based on the assumption that most plastic is floating on the ocean's surface which is simply not the case. It has been shown that most plastic is suspended at around 100-150m in the water column meaning it would escape the barrier's claws... if this is true then the company's estimates of the timescale involved in cleaning up ocean plastic becomes vastly skewed.
For more criticism of the project see here and for Boyan Slat's response see here (all 530 pages of it...!)
At first glance, the concept of giant floating barriers to rid our oceans of plastic seems obvious...and maybe that's the problem: it's too obvious. I can't help but feel that it's going to take a lot more than two dozen or so 100km long barriers to combat the problem of ocean waste. These are merely a speck in the 315 million square kilometres of ocean...
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| One of the large floating barriers similar to the one which will be installed in the North Sea next year (Source: http://i.dailymail.co.uk/i/pix/2015/06/05/12/29600FF200000578-0-image-a-15_1433503748631.jpg) |
This will be the first time that the technology will be tested in open waters and will provide an opportunity to measure the effects of waves and currents on the barrier using cameras and sensors. If successful, Ocean CleanUp hope to install other floating barriers around the world, with plans for a 100km long v-shaped one in the 'Great Pacific Garbage Patch' where large volumes of plastic rubbish collect. The company estimate that once installed, the barrier could collect around 42% of the plastic in this area over 10 years, representing a phenomenal 70, 320, 000kg of plastic!
The video below shows what the organisation do:
However, not everyone is convinced of the project's feasibility with many condemning the giant barriers as unsupported by scientific research and as a quick-fix to a problem of a colossal scale. It is argued by some that the barriers will quickly become colonised by sea life such as barnacles, fish and sea birds which when coupled with salt from the ocean, could spell disaster for the functionality of the equipment. Another issue is that the tiny organism, plankton, which have no control over their movements, would essentially be caught up in the currents directing the removed plastic into the recycling containers...with plankton so vital to the food chain this could be a huge problem with the barriers and Slat himself admits that more research is needed on this.
There are also issues with the economics of the project as the plastic, once collected, will need to be sorted into its various types and with many of the plastic pieces on a very small scale, analysis will be costly and time consuming. Moreover, there are arguments that the barriers will not collect anywhere close to the volume suggested by the organisation as their figures are based on the assumption that most plastic is floating on the ocean's surface which is simply not the case. It has been shown that most plastic is suspended at around 100-150m in the water column meaning it would escape the barrier's claws... if this is true then the company's estimates of the timescale involved in cleaning up ocean plastic becomes vastly skewed.
For more criticism of the project see here and for Boyan Slat's response see here (all 530 pages of it...!)
At first glance, the concept of giant floating barriers to rid our oceans of plastic seems obvious...and maybe that's the problem: it's too obvious. I can't help but feel that it's going to take a lot more than two dozen or so 100km long barriers to combat the problem of ocean waste. These are merely a speck in the 315 million square kilometres of ocean...
Wednesday, 6 January 2016
Coral Bleaching Part II...Past and Future Coral Reefs
So it's been a while since my last post on the problem of coral bleaching (which you can find here if you need to refresh your memory!) but having got distracted by a number of other interesting stories, I want to return to this issue.
In order to understand what may happen to our coral reefs in the future, it is important to look at what happened in the past and how ancient reef systems responded to climatic changes.
Today, our coral reefs are composed of scleractinian corals however in the past, other types of reef-building organisms dominated. In fact, 100 million years ago when atmospheric carbon dioxide levels were double the current levels, corals were only a minor component of tropical reefs with bivalves and other non-coral organisms dominating instead. This was largely as a result of the elevated carbon dioxide levels altering the pH of the water which favoured those organisms that secreted their shells in the calcite phase of calcium carbonate (corals secrete their shells in aragonite).
The earliest reefs were formed by algae (which often replaces corals once bleached) but by 500 million years ago, reefs were composed of calcifying organisms such as rugose and tabulate corals in addition to mollusks, crustaceans and echinoderms. The development of coral reefs was more or less continuous over a long time span (hundreds of millions of years) with only 'brief' interruptions where no reefs occur in the fossil record coinciding with the major mass extinctions.
Around 250 million years ago, both rugose and tabulate corals became extinct and corals more similar to the modern-day scleractinian corals, appeared. It is thought that the disappearance of the ancient types of coral is linked to changes in ocean chemistry, especially alterations to carbon dioxide concentration.
This paloecological evidence suggests that tropical reef systems are variable, with different states existing depending on the climatic conditions. Based on the fact that ancient reefs were composed of non-coral organisms, it seems likely that at some point in the future our current tropical reef systems could be pushed into a new state as a result of human influences. Given the fact that bleached reefs are frequently replaced by algae, it seems possible that the world's reefs could be replaced by algal reefs like the ones which dominated in the past. Although there have been few studies to investigate this idea, those that exist imply that the alteration of coral reefs to algal reefs would significantly impact upon the species composition of reef systems and given our reliance on them for fisheries and tourism, it is in our favour to address the issue of coral bleaching before it is too late...
Next time...can we save our reefs by breeding new 'super' corals?
In order to understand what may happen to our coral reefs in the future, it is important to look at what happened in the past and how ancient reef systems responded to climatic changes.
Today, our coral reefs are composed of scleractinian corals however in the past, other types of reef-building organisms dominated. In fact, 100 million years ago when atmospheric carbon dioxide levels were double the current levels, corals were only a minor component of tropical reefs with bivalves and other non-coral organisms dominating instead. This was largely as a result of the elevated carbon dioxide levels altering the pH of the water which favoured those organisms that secreted their shells in the calcite phase of calcium carbonate (corals secrete their shells in aragonite).
The earliest reefs were formed by algae (which often replaces corals once bleached) but by 500 million years ago, reefs were composed of calcifying organisms such as rugose and tabulate corals in addition to mollusks, crustaceans and echinoderms. The development of coral reefs was more or less continuous over a long time span (hundreds of millions of years) with only 'brief' interruptions where no reefs occur in the fossil record coinciding with the major mass extinctions.
Around 250 million years ago, both rugose and tabulate corals became extinct and corals more similar to the modern-day scleractinian corals, appeared. It is thought that the disappearance of the ancient types of coral is linked to changes in ocean chemistry, especially alterations to carbon dioxide concentration.
This paloecological evidence suggests that tropical reef systems are variable, with different states existing depending on the climatic conditions. Based on the fact that ancient reefs were composed of non-coral organisms, it seems likely that at some point in the future our current tropical reef systems could be pushed into a new state as a result of human influences. Given the fact that bleached reefs are frequently replaced by algae, it seems possible that the world's reefs could be replaced by algal reefs like the ones which dominated in the past. Although there have been few studies to investigate this idea, those that exist imply that the alteration of coral reefs to algal reefs would significantly impact upon the species composition of reef systems and given our reliance on them for fisheries and tourism, it is in our favour to address the issue of coral bleaching before it is too late...
Next time...can we save our reefs by breeding new 'super' corals?
Tuesday, 5 January 2016
Why you may need to get a new face wash...
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| (Source:http://www.al.com/news/index.ssf/2016/01/congress_bans_microbeads_in_fa.html) |
In recent months, stories of face washes and scrubs containing microbeads and their links to ocean pollution, have flooded the media. Now, in recognition of the problem of microplastics, Barack Obama has just signed the 'Microbead-Free Waters Act of 2015'. This bans the production and intentional addition of plastic microbeads like the ones commonly found in face and body scrubs.
It is estimated that 11 million microbeads end up in our water systems every day and whilst not directly harmful on their own, microbeads often attract harmful chemicals such as PCBs which stick to their surface and are then subsequently ingested by marine life.
The ban will come into effect on 1st July 2017 with several US states (California, Connecticut, New Jersey and Illinois) having already banned microbeads. Major companies such as Unilever are also pledging to phase out the use of microbeads in their products.
There are now calls for the UK to follow in US footsteps and also ban microbeads and in the meantime to at least make it clear which products contain the harmful tiny plastic pieces so that consumers who want to can make a point of using microbead-free ones. Although some companies, for example, Colgate-Palmolive, have voluntarily removed the microbeads from their products after criticism, many others continue to manufacture microbeads.
Hopefully in the near future, the problem of microplastics and in particular in the form of microbeads, can be globally recognised with more countries introducing a ban. Until then, we can all play a part in trying to reduce the amount of plastic entering our oceans by making a simple switch to microbead-free products.
Sunday, 20 December 2015
Cop21... thoughts
A little while after the Cop21 negotiations in Paris have come to an end, I thought it would be good to take a moment to reflect on the outcomes of the meetings.
Just from a quick glance in the media, I can't help but feel that the agreements reached are a little general and nothing other than what we knew needed to happen. Hailed as an historic moment in getting nearly 200 countries to reach an agreement on climate change, here is a summary of the Cop21 outcomes:
- To keep global temperatures "well below" 2.0C above pre-industrial times and "endeavour to limit them even more, to 1.5C".
- To limit the amount of greenhouse gases emitted by human activity to the same level that trees, soils and the ocean can absorb naturally, beginning at some point between 2050 and 2100.
- To review each country's contribution to cutting emissions every five years so they scale up the challenge.
- For rich nations to help poorer nations by providing "climate finances" to adapt to climate change and switch to renewable energy.
(Source: http://www.bbc.co.uk/news/science-environment-35073297)
The full draft agreement can be found here
As I'm writing a blog focusing on the effects of climate change on the oceans, I was disappointed to note that the word "ocean" only appears once in the draft agreement... The oceans are so fundamental to our Earth system and yet endure climate change's effects in silence and we are only really beginning to realise exactly what is going on beneath the pristine surface. Surely they deserve more of our attention?
One of the other things which stands out to me is a phrase in the second target, 'beginning at some point between 2050 and 2100'. What does this mean? Surely whether we begin limiting the amount of greenhouse gases emitted into the atmosphere in the earlier part of this timeframe or towards the end will make a massive difference to the effects on our planet and the chance of us reaching the "2C target"?
You've probably guessed from reading this that I am a little cynical about the outcomes of Cop21. I guess only time will tell to see if we really can cut our emissions and keep global temperatures below that golden 2C above pre-industrialisation values. Feel free to post your thoughts in the comments section and I'll be putting a poll up so you can share your feelings on the outcomes of Cop21.
Just from a quick glance in the media, I can't help but feel that the agreements reached are a little general and nothing other than what we knew needed to happen. Hailed as an historic moment in getting nearly 200 countries to reach an agreement on climate change, here is a summary of the Cop21 outcomes:
- To keep global temperatures "well below" 2.0C above pre-industrial times and "endeavour to limit them even more, to 1.5C".
- To limit the amount of greenhouse gases emitted by human activity to the same level that trees, soils and the ocean can absorb naturally, beginning at some point between 2050 and 2100.
- To review each country's contribution to cutting emissions every five years so they scale up the challenge.
- For rich nations to help poorer nations by providing "climate finances" to adapt to climate change and switch to renewable energy.
(Source: http://www.bbc.co.uk/news/science-environment-35073297)
The full draft agreement can be found here
As I'm writing a blog focusing on the effects of climate change on the oceans, I was disappointed to note that the word "ocean" only appears once in the draft agreement... The oceans are so fundamental to our Earth system and yet endure climate change's effects in silence and we are only really beginning to realise exactly what is going on beneath the pristine surface. Surely they deserve more of our attention?
One of the other things which stands out to me is a phrase in the second target, 'beginning at some point between 2050 and 2100'. What does this mean? Surely whether we begin limiting the amount of greenhouse gases emitted into the atmosphere in the earlier part of this timeframe or towards the end will make a massive difference to the effects on our planet and the chance of us reaching the "2C target"?
You've probably guessed from reading this that I am a little cynical about the outcomes of Cop21. I guess only time will tell to see if we really can cut our emissions and keep global temperatures below that golden 2C above pre-industrialisation values. Feel free to post your thoughts in the comments section and I'll be putting a poll up so you can share your feelings on the outcomes of Cop21.
Friday, 18 December 2015
Just Jellyfish
Yesterday, I visited the Natural History Museum's Wildlife Photographer of the Year Exhibition which displays a selection of the most outstanding wildlife photography of the year.
Many of the photos are relevant to the wider theme of global environmental change especially those which show the impacts of human activity on wildlife however, a photo which particularly struck a chord with me was this one taken by Thomas Peschak:
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| 'Just Jellyfish' (Source: http://www.nhm.ac.uk/visit/wpy/gallery/2015/images/under-water/5020/just-jellyfish.html) |
Friday, 11 December 2015
Past Marine Ecosystem Changes
We are well aware that our oceans are undergoing vast changes as a result of human activity and given their role as climate regulators and their huge contribution to primary productivity, understanding these changes is extremely important.
Looking back at the paleoecological record, many marine responses to climate change can be observed and these past insights are incredibly valuable in predicting the response of marine communities to human-induced climate change in the future.
Changes in temperature, sea level, circulation patterns and acidification are the major drivers of marine response to climate change with communities responding with range changes, changes in composition and changes in body size.
Temperature Change
The most significant effect of temperature change in the oceans is on species' distributions and records dating back several million years reveal range changes in response to temperature. For example, warmer temperatures in the Miocene (15-17 million years ago) led to range extensions of mollusks and plankton, with many species that are currently found in the tropics and subtropics extending much further to the north - some as far as Alaska. As the climate cooled again after the mid-Miocene global temperature peak, these species' distributions altered, retreating southwards once more.
Changes in species' ranges can lead to changes in community composition, some of which are transitory while others are longer-lasting. Global cooling that occurred around 3.5 million years ago led to the loss of larger predatory species such as crabs, sharks and many fish from Antarctic communities and as a result, these communities today are dominated by invertebrates such as star fish even at higher trophic levels.
Fossil data for the Pleistocene (last 2 million years) are abundant and indicate clear responses to temperature change such as latitudinal shifts whereby species' distributions shift polewards with warming and towards the equator with cooling: species that existed between Santa Barbara and Ensenada (both California) during a warm interglacial 125,000 years ago, exist only in (sub)tropical waters today (Roy et al. 1996).
Sea level change
Global warming fuels sea level change in two main ways: from thermal expansion of the oceans and from the melting of land ice. If the ice in Antarctica and greenland alone was to melt, global sea level would rise by approximately 75m (Hannah, 2011). It is important to note that melting of sea ice in comparison while having profound impacts on food webs, would not be a major contributor to global sea level rise (this is because sea ice already displaces water).
Past warming and cooling has raised and lowered sea levels continuously with Pleistocene glacial-interglacial cycles being one of the main drivers for change. Range shifts of marine organisms in response to sea level change exist as far back as 55 million years ago. For instance, bivalves in tropical Pacific islands changed distribution repeatedly, affecting community composition. Similar effects have also been observed in bivalves, gastropods and other species in places such as Fiji and Kenya.
Ocean Circulation
Ocean circulation plays an important role in all of the major functions of the ocean (heat and carbon dioxide absorption, the transportation of these and their mixing into deep waters). Evaluation of paleoecological data reveals that changes in two major types of ocean circulation have had exceptional influence on both climate and biodiversity in the past- these are thermohaline changes and changes in teleconnections.
Thermohaline circulation helps to maintain nutrient levels in the deep ocean which is linked to high productivity in phytoplankton and thus high biodiversity and abundance in other trophic levels o the food chain. When the breakdown of this circulation system occurs (often as a result of a large input in freshwater in the North Atlantic), deep waters become oxygen deprived which can lead to the death of many organisms. Oxygen deprivation in deep waters is believed to be linked to many of the major extinction events in the past.
Teleconnections include El Nino as well as the North Atlantic Oscillation (NAO). These result in sea surface temperature changes (see previous blog post) and El Nino episodes are associated with decreased upwelling of deep nutrient-rich waters and changed air circulation patterns over the Pacific. Marine systems respond rapidly to these changes, changes in fish stocks of species such as Atlantic cod, sardines and Pacific salmon, are particularly widespread.
Ocean Chemistry
Major changes in ocean chemistry (primarily carbon dioxide and pH levels) are recorded in the fossil record, especially in the shells and skeletons of marine organisms. Both ocean pH and carbon dioxide affect the ability of organisms to form hard calcium carbonate shells and remains of these shells can provide a useful indication of past sea condition. Corals and foraminifera are the leading indicators of past climate- analysis of the isotopic composition of their shells allow reconstruction of past ocean temperatures and conditions.
In my next post, more on the distribution of coral reefs through history and the fate of our reefs in the future.
Looking back at the paleoecological record, many marine responses to climate change can be observed and these past insights are incredibly valuable in predicting the response of marine communities to human-induced climate change in the future.
Changes in temperature, sea level, circulation patterns and acidification are the major drivers of marine response to climate change with communities responding with range changes, changes in composition and changes in body size.
Temperature Change
The most significant effect of temperature change in the oceans is on species' distributions and records dating back several million years reveal range changes in response to temperature. For example, warmer temperatures in the Miocene (15-17 million years ago) led to range extensions of mollusks and plankton, with many species that are currently found in the tropics and subtropics extending much further to the north - some as far as Alaska. As the climate cooled again after the mid-Miocene global temperature peak, these species' distributions altered, retreating southwards once more.
Changes in species' ranges can lead to changes in community composition, some of which are transitory while others are longer-lasting. Global cooling that occurred around 3.5 million years ago led to the loss of larger predatory species such as crabs, sharks and many fish from Antarctic communities and as a result, these communities today are dominated by invertebrates such as star fish even at higher trophic levels.
Fossil data for the Pleistocene (last 2 million years) are abundant and indicate clear responses to temperature change such as latitudinal shifts whereby species' distributions shift polewards with warming and towards the equator with cooling: species that existed between Santa Barbara and Ensenada (both California) during a warm interglacial 125,000 years ago, exist only in (sub)tropical waters today (Roy et al. 1996).
Sea level change
Global warming fuels sea level change in two main ways: from thermal expansion of the oceans and from the melting of land ice. If the ice in Antarctica and greenland alone was to melt, global sea level would rise by approximately 75m (Hannah, 2011). It is important to note that melting of sea ice in comparison while having profound impacts on food webs, would not be a major contributor to global sea level rise (this is because sea ice already displaces water).
Past warming and cooling has raised and lowered sea levels continuously with Pleistocene glacial-interglacial cycles being one of the main drivers for change. Range shifts of marine organisms in response to sea level change exist as far back as 55 million years ago. For instance, bivalves in tropical Pacific islands changed distribution repeatedly, affecting community composition. Similar effects have also been observed in bivalves, gastropods and other species in places such as Fiji and Kenya.
Ocean Circulation
Ocean circulation plays an important role in all of the major functions of the ocean (heat and carbon dioxide absorption, the transportation of these and their mixing into deep waters). Evaluation of paleoecological data reveals that changes in two major types of ocean circulation have had exceptional influence on both climate and biodiversity in the past- these are thermohaline changes and changes in teleconnections.
Thermohaline circulation helps to maintain nutrient levels in the deep ocean which is linked to high productivity in phytoplankton and thus high biodiversity and abundance in other trophic levels o the food chain. When the breakdown of this circulation system occurs (often as a result of a large input in freshwater in the North Atlantic), deep waters become oxygen deprived which can lead to the death of many organisms. Oxygen deprivation in deep waters is believed to be linked to many of the major extinction events in the past.
Teleconnections include El Nino as well as the North Atlantic Oscillation (NAO). These result in sea surface temperature changes (see previous blog post) and El Nino episodes are associated with decreased upwelling of deep nutrient-rich waters and changed air circulation patterns over the Pacific. Marine systems respond rapidly to these changes, changes in fish stocks of species such as Atlantic cod, sardines and Pacific salmon, are particularly widespread.
Ocean Chemistry
Major changes in ocean chemistry (primarily carbon dioxide and pH levels) are recorded in the fossil record, especially in the shells and skeletons of marine organisms. Both ocean pH and carbon dioxide affect the ability of organisms to form hard calcium carbonate shells and remains of these shells can provide a useful indication of past sea condition. Corals and foraminifera are the leading indicators of past climate- analysis of the isotopic composition of their shells allow reconstruction of past ocean temperatures and conditions.
In my next post, more on the distribution of coral reefs through history and the fate of our reefs in the future.
Cleaning up the oceans...one trainer at a time
It has been revealed today that Adidas has teamed up with Parley for the Oceans (an organisation dedicated to reducing plastic waste in the oceans) to make a 3D printed trainer made out of recycled ocean plastic.
The shoe has an upper made of ocean plastic and a midsole produced from recycled polyster and gillnets (a type of fishing net). At the moment, the trainer is just a prototype but according to Adidas the goal is to "rethink design and help stop ocean plastic pollution".
The shoe has an upper made of ocean plastic and a midsole produced from recycled polyster and gillnets (a type of fishing net). At the moment, the trainer is just a prototype but according to Adidas the goal is to "rethink design and help stop ocean plastic pollution".
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| Adidas' recycled ocean plastic trainer (Image source: https://metrouk2.files.wordpress.com/2015/12/adidas-3d-printed-trainers.jpg?w=620&h=414&crop=1) |
No word yet as to when the shoe will be available in the shops but good on Adidas for raising awareness of this important issue.
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