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.