Dr. Matt Landos, co-author of the report, says that many people erroneously believe that fish declines are caused only by overfishing. “In fact, the entire aquatic food web has been seriously compromised, with fewer and fewer fish at the top, losses of invertebrates in the sediments and water column, less healthy marine algae, coral, and other habitats, as well as a proliferation of bacteria and toxic algal blooms. Chemical pollution, along with climate change itself a pollution consequence, are the chief reasons for these losses.”
Aquatic Pollutants in Oceans and Fisheries documents the numerous ways in which chemicals compromise reproduction, development, and immune systems among aquatic and marine organisms. It warns that the impacts scientists have identified are only likely to grow in the coming years and will be exacerbated by a changing climate.
As co-author Dr. Mariann Lloyd-Smith points out, the production and use of chemicals have grown exponentially over the past couple of decades. “Many chemicals persist in the environment, making environments more toxic over time. If we do not address this problem, we will face permanent damage to the marine and aquatic environments that have nourished humans and every other life form since the beginning of time.”
The report identifies six key findings:
Overfishing is not the sole cause of fishery declines. Poorly managed fisheries and catchments have wrought destruction on water quality and critical nursery habitat as well as the reduction and removal of aquatic food resources. Exposures to environmental pollutants are adversely impacting fertility, behavior, and resilience, and negatively influencing the recruitment and survival capacity of aquatic species. There will never be sustainable fisheries until all factors contributing to fishery declines are addressed.
Chemical pollutants have been impacting oceanic and aquatic food webs for decades and the impacts are worsening. The scientific literature documents man-made pollution in aquatic ecosystems since the 1970s. Estimates indicate up to 80% of marine chemical pollution originates on land and the situation is worsening. Point source management of pollutants has failed to protect aquatic ecosystems from diffuse sources everywhere. Aquaculture is also reaching limits due to pollutant impacts with intensification already driving deterioration in some areas, and contaminants in aquaculture feeds affecting fish health.
Pollutants including industrial chemicals, pesticides, pharmaceuticals, heavy metals, plastics and microplastics have deleterious impacts to aquatic ecosystems at all trophic levels from plankton to whales. Endocrine disrupting chemicals, which are biologically active at extremely low concentrations, pose a particular long-term threat to fisheries. Persistent pollutants such as mercury, brominated compounds, and plastics biomagnify in the aquatic food web and ultimately reach humans.
Aquatic ecosystems that sustain fisheries are undergoing fundamental shifts as a result of climate change. Oceans are warming and becoming more acidic with increasing carbon dioxide deposition. Melting sea ice, glaciers and permafrost are increasing sea levels and altering ocean currents, salinity and oxygen levels. Increases in both de-oxygenated ‘dead zones’ and coastal algal blooms are being observed. Furthermore, climate change is re-mobilizing historical contaminants from their ‘polar sinks.’
Climate change and chronic exposures to pesticides all can amplify the impacts of pollution by increasing exposures, toxicity and bioaccumulation of pollutants in the food web. Methyl mercury and PCBs are among the most prevalent and toxic contaminants in the marine food web.
We are at the precipice of disaster, but have an opportunity for recovery. Progress requires fundamental shifts in industry, economy and governance, the cessation of deep-sea mining and other destructive industries, and environmentally sound chemical management, and true circular economies. Re-generative approaches to agriculture and aquaculture are urgently required to lower carbon, stop further pollution, and begin the restoration process.
Global fish stocks are exploited or depleted to such an extent that without urgent measures we may be the last generation to catch food from the oceans.
It has been some time since most humans lived as hunter-gatherers – with one important exception. Fish are the last wild animal that we hunt in large numbers. And yet, we may be the last generation to do so.
Entire species of marine life will never be seen in the Anthropocene (the Age of Man), let alone tasted, if we do not curb our insatiable voracity for fish. Last year, global fish consumption hit a record high of 17 kg (37 pounds) per person per year, even though global fish stocks have continued to decline. On average, people eat four times as much fish now than they did in 1950.
Around 85% of global fish stocks are over-exploited, depleted, fully exploited or in recovery from exploitation. Only this week, a report suggested there may be fewer than 100 cod over the age of 13 years in the North Sea between the United Kingdom and Scandinavia. It’s a worrying sign that we are losing fish old enough to create offspring that replenish populations.
Large areas of seabed in the Mediterranean and North Sea now resemble a desert – the seas have been expunged of fish using increasingly efficient methods such as bottom trawling. And now, these heavily subsidised industrial fleets are cleaning up tropical oceans too. One-quarter of the EU catch is now made outside European waters, much of it in previously rich West African seas, where each trawler can scoop up hundreds of thousands of kilos of fish in a day. All West African fisheries are now over-exploited, coastal fisheries have declined 50% in the past 30 years, according to the UN Food and Agriculture Organisation.
Catches in the tropics are expected to decline a further 40% by 2050, and yet some 400 million people in Africa and Southeast Asia rely on fish caught (mainly through artisanal fishing) to provide their protein and minerals. With climate change expected to impact agricultural production, people are going to rely more than ever on fish for their nutritional needs.
The policy of subsidising vast fishing fleets to catch ever-diminishing stocks is unsustainable. In Spain, for example, one in three fish landed is paid for by subsidy. Governments, concerned with keeping jobs alive in the fishing industry in the short-term, are essentially paying people to extinguish their own long-term job prospects – not to mention the effect on the next generation of fishermen. Artisanal fishing catches half the world’s fish, yet it provides 90% of the sector’s jobs.
Protect depletion
Clearly, industrialised countries are not about to return to traditional methods. However, the disastrous management of the industry needs to be reformed if we are to restore fisheries to a sustainable level. In the EU alone, restoring stocks would result in greater catches of an estimated 3.5 tonnes, worth £2.7 billion a year.
Rather than having a system in which the EU members each hustle for the biggest quotas – which are already set far beyond what is sustainable – fisheries experts suggest individual governments should set quotas based on stock levels in their surrounding waters. Fishermen should be given responsibility over the fish they hunt – they have a vested interest in seeing stocks improve, after all – and this could be in the form of individual tradable catch shares of the quotas. Such policies end the tragedy of the commons situation whereby everyone grabs as much as they can from the oceans before their rival nets the last fish, and it’s been used successfully in countries from Iceland to New Zealand to the US. Research shows that managing fisheries in this way means they are twice as likely to avoid collapse as open-access fisheries.
In severely depleted zones, the only way to restore stocks is by introducing protected reserves where all fishing is banned. In other areas, quota compliance needs to be properly monitored – fishing vessels could be licensed and fitted with tracking devices to ensure they don’t stray into illegal areas, spot-checks on fish could be carried out to ensure size and species, and fish could even be tagged, so that the authorities and consumers can ensure its sustainable source.
The other option is to take humanity’s usual method of dealing with food shortages, and move from hunter-gathering to farming.
Already, more than half of the fish we eat comes from farms – in China, it’s as high as 80% – but doing this on an industrial scale has its problems. Farms are stocked with wild fish, which must then be fed – larger fish like salmon and tuna eat as much as 20 times their weight in smaller fish like anchovies and herring. This has led to overfishing of these smaller fish, but if farmed fish are fed a vegetarian diet, they lack the prized omega-3 oils that make them nutritious, and they do not look or taste like the wild varieties. Scientists are working to create an artificial version of omega-3 – current synthetic omega-3 versions are derived from fish oils.
Fish farms are also highly polluting. They produce a slurry of toxic run-off – manure – which fertilises algae in the oceans, reducing the oxygen available to other species and creates dead zones. Scotland’s salmon-farming industry, for example, produces the same amount of nitrogen waste as the untreated sewage of 3.2 million people – over half the country’s population. As a result, there are campaigns to ban aquaculture from coastal areas.
Farmed fish are also breeding grounds for infection and parasites that kill off large proportions of fish – escapees then frequently infect wild populations. Farmers try to control infestations with antibiotics, but usually only succeed in creating a bigger problem of antibiotic resistance.
A drumbeat of recent scientific studies emphasises an increasingly alarming convergence of crises for Earth’s oceans.
The amount of plastic floating in the Pacific Gyre – a massive swirling vortex of rubbish – has increased 100-fold in the past four decades, phytoplankton counts are dropping, over-fishing is causing dramatic decreases in fish populations, decreasing ocean salinity is intensifying weather extremes, and warming oceans are speeding up Antarctic melting.
One warning of humanity’s increasingly deleterious impact on the oceans came from prominent marine biologist Jeremy Jackson of the Scripps Institute of Oceanography.
In a 2008 article published in Proceedings of the National Academy of Sciences, Jackson warned that, without profound and prompt changes in human behaviour, we will cause a “mass extinction in the oceans with unknown ecological and evolutionary consequences”.
The statement might sound extreme, until one considers what science journalist Alanna Mitchell has written about the oceans: “Every tear you cry … ends up back in the ocean system. Every third molecule of carbon dioxide you exhale is absorbed into the ocean. Every second breath you take comes from the oxygen produced by plankton.”
These and other issues will be discussed at the Rio 20 United Nations Conference on Sustainability, which will be held between June 20 and 22 in Rio de Janeiro, Brazil.
But marine biologists, oceanographers, and others who study the seas are telling Al Jazeera of the deepening impact humans are having on the oceans, and, from what they are saying, now is the time to listen.
Plastic, plastic everywhere…
The most obvious impact humans are having on the world’s oceans is pollution. Though it can take myriad forms, pollution is now most shockingly evident in the seas in the form of giant, swirling gyres of plastic.
Scientists recently investigated the North Pacific Subtropical Gyre, known as the “Great Pacific Garbage Patch”, and found an “alarming amount” of refuse, much of it comprising individual pieces of very small size. The eastern section of the spiralling mass, between Hawaii and California, is estimated to be around twice the size of Texas, and is having ecosystem-wide impacts, according to their study released May 8.
Miriam Goldstein, a graduate student researcher at Scripps Institution of Oceanography at University of California San Diego, and the lead author of the study, told Al Jazeera that by adding this amount of plastic to the oceans, humans could be causing large-scale change to the ocean’s ecological system.
“We found eggs on the pieces of plastic, and these were sea-skater [insect] eggs,” Goldstein said. “Sea skaters naturally occur in the gyre and are known to lay their eggs on floating objects. So we found that the amount of eggs being laid had increased with the amount of plastic.”
Goldstein is also concerned by the findings because, “Our work shows there could be potential effects to the ocean ecosystem that we can’t expect or predict. There are five subtropical gyres, one in each ocean basin, and they are natural currents. They are vast areas of the oceans; together they comprise the majority of the area of the oceans. So altering them on a large scale could have unexpected results on all kinds of things.”
The study shows how an increase in pollution, in this case an immense amount of plastic, may have dire consequences for animals across the entire marine food web.
This Scripps study follows another report by colleagues at the institution that showed nine per cent of the fish collected during the trip to study the gyre had plastic waste in their stomachs.
Published in Marine Ecology Progress Series, that study estimated that fish at intermediate ocean depths in the North Pacific Ocean could be ingesting plastic at the staggering rate of 12,000 to 24,000 tonnes per year.
Dr Wallace J Nichols, a research associate at the California Academy of Sciences, told Al Jazeera he finds plastic on every beach he visits across the globe, and added, “Probably every sea turtle on the planet interacts with plastic at some point in its life.”
Jo Royle, a trans-ocean skipper and ocean advocate, has seen the same.
“For 13 years I’ve been crossing oceans,” she told Al Jazeera. “I’ve seen plastic on the coastline of Antarctica, and over the years we’ve noticed plastic becoming more of an issue on remote islands. Over the last seven years we’ve seen it increase dramatically. I can’t remember the last time I’ve been on a beach and not seen plastic.”
Biological oceanographer Dr Debora Iglesias-Rodriguez, with the National Oceanography Centre at Britain’s University of Southampton, is also concerned.
“Marine pollution is a big issue,” she told Al Jazeera. “There is this idea that oceans have unlimited inertia, but nano-particles of plastic getting into marine animals and the food chain are affecting fish fertility rates, and this affects food security and coastal populations. Pollution is having a huge impact on the oceans, and is urgent and needs to be dealt with.”
Dead zones
Another phenomenon afflicting Earth’s oceans are “dead zones”.
While these can be formed by natural causes, climate change, along with human activities and industrial waste, have greatly aggravated the situation.
The US National Oceanographic and Atmospheric Administration released a study showing that rising global temperatures cause oceans to warm, which translates into a decreased capacity to hold oxygen.
The excessive use by industrial agriculture of chemical fertilisers containing phosphorus and nitrogen is the other key factor, since these chemicals encourage the increased development of algae – starving other marine life of oxygen.
The world’s second-largest and most heavily studied human-caused coastal dead zone is in the Gulf of Mexico, a zone caused by massive amounts of the aforementioned chemicals, along with other sources of nitrogen from animal feed, sewage treatment plants, and urban runoff from the Mississippi River flowing into the Gulf.
“All this pollution flows down and in the summer causes huge algae blooms,” Matt Rota, Science and Water Policy Director for the Gulf Restoration Network, told Al Jazeera. “These algae then die and sink to the bottom, where bacteria eat them and deplete the water of oxygen. And the water can’t mix to get more oxygen into it, so sea life suffocates and dies if it’s unable to swim away.”
The Gulf of Mexico dead zone varies in size and shape, but has been steadily increasing in size since it was first measured at 9,774 sq km in 1985. It forms annually at the mouth of the Mississippi River, and spans an area that encompasses the entire coast of Louisiana, and over to Texas.
An oceanographer who noticed a disappearing act in which the surface of the ocean went from confetti-covered to clear now suggests wind may driving large amounts of trash deeper into the sea.
Oceanographer Giora Proskurowski was sailing in the Pacific Ocean when he saw the small bits of plastic debris disappear beneath the water as soon as the wind picked up.
His research on the theory, with Tobias Kukulka of the University of Delaware, suggests that on average, plastic debris in the ocean may be 2.5 times higher than estimates using surface-water sampling. In high winds, the volume of plastic trash could be underestimated by a factor of 27, the researchers report this month in the journal Geophysical Research Letters.
Plastic waste can wreak havoc on an ecosystem, harming fish and other organisms that ingest it, possibly even degrading a fish’s liver; the trashy bits also make nice homes for bacteria and algae that get carried to other areas of the ocean where they could be invasive or cause other problems, the researchers noted.
In 2010, the team collected water samples at various depths in the North Atlantic Ocean. “Almost every subsurface tow we took had plastic in the net,” Proskurowski told LiveScience, adding that they used a specialized tow net that isolated certain layers of the water, so it would only open at a specific depth and close before being pulled up.
Next, they combined the trash tally with wind measurements to come up with a mathematical model, which allowed them to calculate the amount of debris at different depths on average as well as look at how that amount changed with different conditions, such as on a windy day.
They found 2.5 times more debris in the layers of water below the “surface water” (defined as the top 9.8 inches or 25 centimeters) as was found in that surface section. The debris was distributed down to a depth of about 65 to 82 feet (20 to 25 meters).
The findings mean the estimates of plastic litter in the ocean, conducted by skimming the surface water only, may in some cases vastly underestimate the true amount of plastic debris there.
“The scope of the [plastic debris] problem is not just at the very surface but goes down to 20 meters or so, and that plastic is distributed throughout this layer,” Proskurowski said during an interview.
He and his colleagues plan to publish a simplified version of the model so others investigating ocean plastics can use it.
In 1872 the HMS Challenger pulled out from Portsmouth, England to begin an unprecedented scientific expedition of the world’s oceans. During its over three year journey the HMS Challenger not only collected thousands of new species and sounded unknown ocean depths, but also took hundreds of temperature readings—data which is now proving invaluable to our understanding of climate change.
Utilizing the temperature data from the HMS Challenger expedition and comparing it to contemporary temperatures, researchers writing in Nature Climate Change found that the oceans’ surface— where marine warming is most intense—saw temperature rise on average by 0.59 degrees Celsius (1.1 degrees Fahrenheit) over the past 135 years or so. This implies that oceanic temperatures have been rising for at least a century.
“The significance of the study is not only that we see a temperature difference that indicates warming on a global scale, but that the magnitude of the temperature change since the 1870s is twice that observed over the past 50 years,” explains lead author Dean Roemmich, University of California San Diego physical oceanographer. “This implies that the time scale for the warming of the ocean is not just the last 50 years but at least the last 100 years.”
Prior research has shown that 90 percent of the heat added to the atmosphere has ended up in the oceans, at least since the 1960s. Roemmich told LiveScience that this implies, “the ocean temperature is probably the most direct measure we have of the energy imbalance of the whole climate system.”
While the HMS Challenger took temperatures at over 300 stations with mercury, pressure, and resistance thermometers, today some 3,500 free-floating Argo robotic probes roll through the seas gathering temperature data.
Temperatures globally, including both land and sea, have risen about 0.8 degrees Celsius (1.44 degrees Fahrenheit) since the first decade of the 1900s. The rate of warmth has doubled since 1950. Scientists overwhelmingly agree that climate change is occurring due to greenhouse gas emissions from burning fossil fuels.
