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 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: 

'Just Jellyfish' (Source: http://www.nhm.ac.uk/visit/wpy/gallery/2015/images/under-water/5020/just-jellyfish.html)

The photo was taken in the Western Cape of South Africa and highlights the problem of the increasing jellyfish population which is occurring as a result of climate change and overfishing. Warmer waters increase the reproductive potential of these sea creatures while overfishing reduces the number of fish available to prey on their young. Worryingly, jellyfish eat the eggs and larvae of other fish and therefore other predators such as seals face serious repercussions as a result of the growing jellyfish population.

More information on this issue can be found in this article by the guardian.

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.

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".

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. 

So what is El Niño?

In my previous post, you may have noticed I referred to something called El Niño as a driver for coral bleaching events. But what is El Niño?

El Niño is a phase in the El Niño Southern Oscillation (ENSO) cycle, the other phase being La Niña. The ENSO describes the fluctuations in temperature between the ocean and atmosphere in the East-Central Equatorial Pacific, as measured by sea surface temperatures (SST) with La Niña being the cold phase and El Niño the warm phase. The frequency of these events can be quite irregular but they occur, on average, every 2-7 years with El Niño typically occurring more frequently than La Niña.

The last largest El Niño event was in 1997-98 which killed 20,000 people and cost billions in damage as a result of changed weather patterns causing cyclones, floods, droughts, fires and mudslides. It also caused the largest global coral bleaching event to date with 16% of the world's coral lost, with some areas, for example, The Maldives, experiencing catastrophic reef coverage losses of up to 90%.

In October this year, NOAA announced the 3rd ever global coral bleaching event as many forecast the current El Niño event to be the strongest yet. The El Niño of 1997-98 saw sea surface temperatures in the Pacific rise to 2.8 degrees Celsius above average; on 18th November 2015, this figure was 3.1 degrees Celsius, with NOAA expecting El Niño conditions to peak in early winter 2015-16.

Coral Bleaching: A global catastrophe... Part I

Perhaps one of the most severe and obvious indications of the harm we are doing to our oceans is the problem of coral bleaching which threatens the existence of one of our most precious ecosystems, coral reefs.

Coral reefs, sometimes called the ‘rainforests of the sea’ cover less than 0.015% of the world’s ocean surface but provide a home for at least 25% of all marine species. They also provide vital ecosystem services to tourism and fisheries, for example, with their annual global economic value estimated to be between US$29.8-375 billion.

So what is coral bleaching and how does it occur?

Corals are unique in that they possess microscopic algae (zooxanthellae) which inhabit their cells and form a symbiotic relationship with the coral: the algae pass nutrients produced by photosynthesis to the coral while in turn the coral provides a physical structure that protects the algae and the right conditions for photosynthesis.

However, when corals are exposed to high water temperatures, they expel their algae. The term coral ‘bleaching’ comes from the fact that as the zooxanthellae are lost from the coral, the photosynthetic pigments in the algae are also lost, resulting in the coral losing its colour. All that remains is their calcium carbonate skeleton which appears white.

Images of healthy v bleached coral (Source: http://dlnr.hawaii.gov/reefresponse/files/2014/04/bleachedVShealthy.jpg)

Just 50 years ago, coral bleaching was practically unheard of; the rise in this catastrophic phenomenon is a direct result of human-induced warming of the oceans. As corals live in shallow surface waters, they are most easily and quickly affected because as the atmosphere has warmed due to the greenhouse effect, some of the heat has been transferred to the surface of the ocean. This has led to an increase in global mean sea surface temperatures (STT).

For bleaching to occur, SST must rise by 1 or 2°C above normal temperatures for periods longer than 3-5 weeks. This usually occurs when higher sea surface baseline temperatures are combined with El Nino events when warming of the waters occurs naturally. 
 Once bleached, corals usually die. Recovery is possible though this is strongly dependent on the severity of the bleaching event and the conditions which follow. Corals that have already been weakened by other factors such as pollution or disturbance by tourism, are much less likely to survive a bleaching event.

The problem of coral bleaching is on the rise with seven major events, affecting reefs the world over, between 1979 and 2002 with the 1997-98 El Nino the worst of the last century for coral bleaching: over 10% of the world’s corals died in this event with mortality as high as 46% in some regions (the Indian Ocean). 

Unfortunately, it is not only rising sea surface temperatures that are causing problems for our coral reefs, ocean acidification as a result of more CO₂ being absorbed by the oceans, is also a worrying issue…

The process of coral bleaching and why it occurs (Source: http://oceanservice.noaa.gov/facts/coralbleaching-large.jpg)

More on this in Part II of my investigation into coral bleaching and a look into how corals have responded to environmental changes in the past and what this may mean for the future.

The Great Ocean Clean-up

Boyan Slat, founder of The Ocean Cleanup (which I mentioned in my last post), talks about his ideas for combatting the problem of plastic waste in our oceans...

Drowning in Plastic

Current estimates state that 8 million tonnes of plastic end up in the ocean each year. At the beginning of October, England introduced a (more or less) compulsory 5p charge for every plastic bag sold in order to combat the problem of plastic waste in our society but, as the video in my previous post shows, it’s going to take a lot more than a plastic bag tax to address the damage we are doing to our marine ecosystems.

Dubbed the ‘new continent’ by some, the huge amount of plastic waste accumulating in the Pacific Ocean as a result of ocean current directions, paints an alarming picture.

In the centre of this area, Midway Atoll, an otherwise pristine paradise, has beaches littered with piles of plastic waste with everything from plastic bags to old computer monitors! Particularly upsetting is the effect on the albatross birds that inhabit this island with bodies of albatross whose bellies were filled with everything from old toothbrushes to cigarette lighters to fragments of plastic toys, strewn across the beaches. 

This albatross died with 558 individual pieces of plastic in its stomach (Photo credit: Eric Dale/FWS Volunteer)

And this isn’t a local problem, worldwide research currently estimates that 90% of all birds have ingested plastic and it is thought that by 2050, virtually all dead birds would be found with plastic in their stomach.

Aside from the obvious problems associated with plastic waste such as marine life becoming entangled in nets and plastic bags and ingesting harmful rubbish, a new problem associated with plastic has arisen: microplastics.

Microplastics are (as the name suggests) small particles of plastic less than 5mm in size and can occur when larger pieces of plastic are broken down or through accidental loss of industrial raw materials such as plastic pellets or powders. More recently, it has been brought to our attention that a large number of beauty products such as face washes and shower gels also contain microplastics in the form of micro-beads which directly enter waterways, eventually winding up in the ocean. 

(For more on the damaging effects of microplastics check out this blog)

Staggering new video footage show microplastics entering the food chain at its lowest level:

In theory, these microplastics ingested by the vital life form, plankton, could work their way through the food chain but currently, further research is needed to understand the impacts of microplastics on different levels of the food chain. 

So what is being done about the plastic problem?

Earlier, in August this year, scientists and volunteers spent a month gathering data on the 'Great Pacific Garbage Patch' with their findings due to be published by mid-2016. The expedition which was sponsored by the organisation, Ocean Cleanup, eventually hopes to lead to the construction of a 60 mile barrier in the middle of the Pacific to collect rubbish with plans for a 1 mile test barrier to collect rubbish near Japan.

There are also urgent calls for the waste management to be improved. Currently, 20 countries are responsible for 83% of all mismanaged material available to enter the oceans, with China at the top of this list producing over a million tonnes of marine debris singlehandedly. 

Map showing estimates of the amount of mismanaged plastic waste generated within 50km of coastlines (source www.bbc.co.uk)

Jambeck et al. (2015) argue that while rich nations need to reduce their consumption of single-use plastic items such as bags, developing countries need to improve their waste management strategies. If the latter isn't addressed, an additional 155 million tonnes of plastic could enter the ocean by 2025.

Further, World Bank calculations predict that global 'peak waste' is unlikely to be reached until 2100, suggesting the problem of plastic rubbish in our oceans may only continue to get worse.

Although efforts to trawl the ocean removing plastic or building large-scale barriers to collect waste are meritorious, it seems unlikely that we will be able to make much of an impact on the plastic already in our oceans especially given that a lot of it ends up on the ocean floor (average depth 14,000ft). The effort must focus on preventing plastic entering our oceans in the first place but given the usefulness of plastic as a material and the rapid development of countries such as India and China, this may be easier said than done...

The Great Ocean Landfill

A couple of weeks ago I posted a photo taken in Taiwan of a dead sperm whale that was found to have large quantities of plastic in its gut; indeed biologists believed this to be largely responsible for the creature’s death.

So now I want to return to the worrying problem of plastic pollution in our oceans with this excerpt from a 2013 documentary that highlights the scale of the problem...

Blog post to follow shortly!

Climate Change and the Forgotten Deep Ocean

'In the deep ocean, warming, acidification and deoxygenation, as well as changing food supply are already occurring and we have barely begun to study this...'

It just so happens that the latest issue of Science Magazine features a special section focusing on the effects of climate change on the oceans. Never one to miss an opportunity, here I review Levin and Le Bris’ article ‘The deep ocean under climate change’ published yesterday.

The deep ocean is defined as the ocean below a depth of 200m and makes up most (90%) of the habitable space for life on Earth. Largely unseen and unmonitored, the deep oceans play a fundamental role in quelling the effects of climate change by absorbing vast amounts of heat and carbon dioxide as well as recycling nutrients for surface ecosystems. The problem is that in acting as a ‘critical buffer to climate change’, vulnerable ecosystems are exposed to the combined pressures of warming, ocean acidification, deoxygenation and altered food inputs.

In their paper, Levin and Le Bris argue that more must be done to mitigate the effects of climate change on the deep ocean as changes that could arise from these stresses may ‘threaten biodiversity and compromise key ocean services that maintain a healthy planet and human livelihoods’.

There are few long-term data series available for the deep ocean on climate-relevant time scales though repeat hydrographic surveys have provided estimates of decadal warming in deep basins of up to a 0.1°C increase per decade in the global ocean (Purkey et al. 2010). However, warming of deep-sea basins is not homogeneous and much higher rates of warming have been documented in the Arctic and Southern Oceans.

It is known that most deep-sea species live in very stable thermal regimes, growing and reproducing slowly and experiencing great longevity- for example, fish in these settings can live for hundreds of years while some forms of colonial coral can live for thousands. As a result these species are thought to be extremely sensitive to change where warming of even 1°C or less may ‘exert stress or cause shifts in distributions and alter species interactions’. A prime example of where this has already occurred is in the Palmer Deep near the Antarctic Peninsula, where warming above a 1.4°C threshold has prompted the invasion of lithodid crabs: voracious predators that are responsible for the dramatic plunge in benthic invertebrate numbers. And what is more worrying, according to the authors, is that many species of the deep ocean are yet to be described and the impacts of climate change on such species unknown. Armstrong et al. (2012) argue that ‘potential loss of deep-sea biodiversity may suppress adaptation capacity and limit the living library of species, genes and biomolecules available to future generations’.

Fig 1. A) Lithodid crabs invading Palmer Deep, Antarctica enabled by warming; B) expansion of cold seep fauna due to methane release induced by warming; C) Mediterranean cold-water coral reefs affected by warming and acidification; D) Low-oxygen tolerant Humboldt squid have expanded their distribution along the East Pacific margin

Further, it is warned that warming of the seafloor also has the potential to release methane from gas hydrates buried along continental margins. 

In a similar manner to that of warming, data relating to the effects of acidification on the deep ocean are rare and direct observation of the biological consequences of acidification on organisms is lacking.

Increased CO₂ is predicted to decrease the habitat range suitable for calcifying marine species because the depth at which water becomes undersaturated for aragonite or calcite will move upward. The effects on deep-sea coral reefs is of particular concern because they support extremely diverse communities as well as providing fundamental habitats to commercial fishes.    

Warming of the ocean also results in a decrease in its ability to hold oxygen and waters become more stratified because warm water being less dense than cold water creates strong density gradients which reduce vertical mixing. The combined effects of reduced oxygen solubility in warmer water and increased stratification create widespread deoxygenation, with effects greatest at 200-700m. This is leading to the expansion of the world’s naturally occurring low oxygen zones (OMZs), causing shifts in habitat usage. For example, intolerant billfishes are faced with a reduction in suitable habitat whereas for hypoxia-tolerant species such as the Humboldt squid, habitat ranges are expanding. 

The paper also explains that increased stratification also reduces nutrient supply to surface waters from the deeper ocean where organic matter is recycled and vast abyssal habitats beneath oligotrophic (nutrient-poor) waters may be further deprived of organic matter supply. They argue this could lead to decreased benthic biomass and altered respiration and bioturbation rates and predictions worryingly suggest a similar trend could affect 80% of biodiversity hotspots.

Interactions between many different climate stressors in deep sea ecosystems are complex and many areas expected to experience the greatest climatic changes are also subject to anthropogenic pressures from mining, fishing and oil and gas exploration.

Fig.2 The current and proposed human exploitation activities in the deep ocean with CO2-induced change in the temperature, pH and oxygenation of the deep ocean (Levin and Le Bris 2015)

But what can be done?

As it stands nobody is responsible for protecting the mitigation potential or resilience of ecosystems in the vast deep oceans and 64% of the world’s ocean is beyond national jurisdiction meaning it isn’t covered by the United Nations Framework Convention on Climate Change (UNFCCC). As Levin and Le Bris state, ‘the biodiversity and climate change vulnerability’ of the deep ocean exist in a ‘policy vacuum’. 

  

As with so many other climate change problems, the first and foremost effort must be put into reducing CO₂ emissions although even if this were to occur, the deep ocean will continue to experience the effects of these emissions for years to come. Other ways to mitigate the effects of climate change on the deep sea are limited- possibilities include spatial planning to limit human activities that may help to create safe havens for endangered species and attempts to reduce physical and chemical disturbances from bottom trawling, oil and gas extraction and seabed mining.

Levin says there’s an urgent need for a deep-ocean observation network to improve climate modelling and evaluate feedbacks between the ocean that can act to speed up or slow down the rate of warming. The ocean’s capacity to absorb heat and carbon dioxide is not indefinite, she warns.