Plastic waste and seabirds

Plastic waste is an important issue for marine conservation. Globally, a greater mass of human waste goes into the ocean than the mass of fish we take out and much of the waste is plastics. And, because plastics breakdown very slowly in the environment they can accumulate in the ocean forming garbage patches. 

Many animals eat or are entangled by plastic debris, which effects animals from very large things like whales to microscopic crustaceans. Photographs of the plastic filled skeletons of albatross chicks on Midway Atoll have placed seabirds among the most recognised victims of plastic pollution. Jennifer Lavers has an interesting article on The Conversation about the problem of plastic pollution for the flesh-footed shearwater and the failure of the Australian Government to place the it on the threatened species list despite significant population declines.

Fish get wasted on wastewater

In most cities sewage is treated to remove most of the things that we don't want going into the environment. But, some things get through and out to sea. The Western Treatment Plant in Melbourne, which treats over 50% of Melbourne's wastewater (including my contribution), releases large amounts of nitrogen into Port Phillip Bay. Indeed, a 1996 report from the Commonwealth Scientific and Industrial Research Organisation recommended that nitrogen released from the Western Treatment Plant be reduced by 1000 tonnes per year. Nearly 20 years later they've achieved half that amount.

The Western Treatment Plant. Covering 10,500 hectares it treats about 50% of Melbourne's wastewater.

Nitrogen pollution is significant issue. It, along with other types of nutrient pollution, has been linked to coral and seagrass declines, and jellyfish blooms. Other things that cause problems in the ocean also slip through sewage treatments plants. From the relatively large things, like plastic fibers from clothing, to the very small, like the drugs we take.

Not all drugs remain active after they've done their job in the human body, but many do. One of the best known and most researched drugs to escape sewage treatment is ethinyl oestradiol, the active ingredient in birth control pills. Decades of research has shown that ethinyl oestradiol has negative impacts on fish and other aquatic organisms. Even very small doses can lead to male fish that produce eggs in their testes, leading to reduced fertility and potentially to population collapse (Kidd et al. 2007).

Sections through the testis of two male fish showing developing eggs, which are the large circular cells surrounded by purple staining tissue. The smaller purple staining flecks are the sperm cells.

Many recreational drugs also make it through wastewater treatment, such as illicit  amphetamines (Kasprzyk-Hordern et al. 2009). To my knowledge, it has not been shown that these arrive in the environment at high enough doses to cause any negative effects. Caffeine, my favorite recreational drug, is detected in seawater at concentrations high enough to produce measurable, but probably minor effects in mussels (del Rey et al. 2011, 2012).

Exposure to the concentrations of caffeine that are normally found in the environment probably have little or no effect on fish. Unlike caffeine, some drugs can build up in the body tissues of fish, making chronic exposure to even low concentrations a risk. Recently a study found that the concentration of a common anti-anxiety medication, oxazepam, was six times higher in the muscle of redfin perch (Perca fluviatilis) than it was in the surrounding river water (Brodin et al. 2013).

A redfin perch, Perca fluviatilis, in an aquarium (photo Wikipedia)

Interestingly, Brodin et al. went on to test what effects oxazepam had on the redfin perch. Annoyingly, they used concentrations of the drug that were three times higher than they recorded in the river and higher than other studies have documented. But, their treatments produced levels of the drug in the muscle tissue of the fish that were comparable to the fish in the river, indicating their results are probably biologically relevant. They found that the fish exposed to the drug exhibited increased activity, reduced sociality, and higher feeding rate relative to control fish.

Although they scuffed their experiment a little with their choice of concentrations, they did do something that few other ecotoxicology studies do. They looked at behavioural traits that are important for the survival of fish in the wild. Too slowly are excotoxicologists moving away from testing the lethal effects of pollutants, often requiring doses that never occur in the wild. Hopefully, the publication of the Brodin et al. paper in the prestigious journal Science will encourage more researchers to examine the effects of pollutants at the levels which they typically occur and on a greater range biologically interesting traits.

References:

Kidd, K., Blanchfield, P., Mills, K., Palace, V., Evans, R., Lazorchak, J., & Flick, R. (2007). Collapse of a fish population after exposure to a synthetic estrogen Proceedings of the National Academy of Sciences, 104 (21), 8897-8901 DOI: 10.1073/pnas.0609568104  

Kasprzyk-Hordern, B., Dinsdale, R., & Guwy, A. (2009). The removal of pharmaceuticals, personal care products, endocrine disruptors and illicit drugs during wastewater treatment and its impact on the quality of receiving waters Water Research, 43 (2), 363-380 DOI: 10.1016/j.watres.2008.10.047  

Rey, Z., Granek, E., & Buckley, B. (2011). Expression of HSP70 in Mytilus californianus following exposure to caffeine Ecotoxicology, 20 (4), 855-861 DOI: 10.1007/s10646-011-0649-6  

Rodriguez del Rey, Z., Granek, E., & Sylvester, S. (2012). Occurrence and concentration of caffeine in Oregon coastal waters Marine Pollution Bulletin, 64 (7), 1417-1424 DOI: 10.1016/j.marpolbul.2012.04.015  

Brodin, T., Fick, J., Jonsson, M., & Klaminder, J. (2013). Dilute Concentrations of a Psychiatric Drug Alter Behavior of Fish from Natural Populations Science, 339 (6121), 814-815 DOI: 10.1126/science.1226850

Seaweek!

Seaweek is coming up fast. It's organised by the Marine Education Society of Australia and running from the 2nd to the 10th of March. I've been invited to participate in a day of activities at Rickets Point Marine Sanctuary on the 7th. I'll be talking to primary and high school students about marine introduced species. The day will bring together marine experts from MESA, Parks Victoria, Melbourne Aquarium, Monash University, the Earth Watch Institute, the Ocean Ark Alliance, the Gould League, Marine Care Ricketts Point, Pelican Expeditions, Nautilus Educational and the Australian Youth Climate Coalition (and me, who is not from any of those organisations).

The theme for Seaweek 13 is ‘Sustainable Seas’. The theme provides a focus for students in schools and for communities to inform and inspire them about the diversity of our marine and coastal environments and how, through good management and individual action, we can all contribute towards the sustainability of these environments.

Aims

• Highlight the sustainable management of Australia’s marine environment;
• Identify factors that threaten the sustainability of marine and coastal ecosystems;
• Facilitate the communication of sustainable marine management projects to the education community;
• Initiate interest and actions for supporting sustainable marine management that help us learn more about and contribute towards the sustainability of our marine and coastal environments; and
• Provide schools with educational resources available on the MESA website for school’s classroom based activities.

Find out more about Seaweek here.

Plastic bag ban

I missed out on World Turtle Day, but the city of Los Angeles gave turtles a small gift. The LA City Council voted 13 - 1 in favour of banning plastic bags on Turtle Day. Turtles are known to eat plastic bags, perhaps mistaking them for jellyfish, and this can lead to their death. A while ago I wrote about the general problem of plastic in the ocean, if you're interested in learning more that's a place to start.

It's currently complicated

A few weeks ago I wrote about the problem of plastic in the ocean. In that post I used a simple graphic showing the location and direction of rotation of the five oceanic gyres. On seeing that diagram you may have guessed that things were actually a little more complicated. Well, they are. Something that might have tipped you off was the swirls in the photos of plankton blooms I posted, here and here. If you want to get a sense of just how complex the ocean currents are, here is a great visualisation of a NASA ocean current model. This too, is a simplification.

An ocean of plastic

There are five major oceans in the world. There's the Arctic Ocean, the Atlantic Ocean, the Pacific Ocean, the Indian Ocean and the Southern Ocean. In the Pacific, the Atlantic and Indian oceans there are huge circular currents called gyres. The Indian Ocean has a single gyre, while the Atlantic and the Pacific have two, one in the northern hemisphere and one in the southern hemisphere.

The five great oceanic gyres showing the direction of rotation

The northern hemisphere gyres rotate in a clockwise direction, while the southern hemisphere gyres rotate in an anti-clockwise direction. The direction of rotation has to do with the Coriolis effect, which is what people joke about when the say that water goes down plug-holes in different directions in Europe compared to Australia. The Coriolis effect doesn't matter too much for water going down plug-holes (other forces are far more important), but operating over long time periods and over large distances it produces gyres.

Because the gyres rotate they are good at accumulating floating items in their centres. Waste material is drawn into the gyres from the countries that surround the gyre. When the waste reaches concentrations that are significantly higher than the rest of the World's oceans that area of ocean is termed a garbage patch. So far surveys have found garbage patches in the North Pacific, North Atlantic and Indian Ocean gyres. Garbage patches also form in other places, but the oceanic gyres form the biggest patches.

Of all the garbage patches the North Pacific gyre is the largest by a considerable margin. Mainland Australia has an area of 7.69 million square kilometres and estimates of the size of the North Pacific Garbage Patch are as high as 15 million square kilometres. So, basically there's a patch of garbage that could cover an area almost twice the size of Australia floating in the North Pacific. It should be noted, however, that other estimates are considerably smaller. Estimates vary largely because different studies use different densities of debris to define what a garbage patch is.

Plastic particles hanging underwater in the North Pacific garbage patch (photo Scripps Oceanography).

The garbage patches collect a huge array of debris and chemical waste. A lot of it, about 80%, comes from land-based sources. Natural disasters, such as a tsunami or a hurricane can lead to large amounts of waste entering the sea. However, the most common route is through storm water and waste water inputs. The other 20% of waste is lost or deliberately dumped from ships at sea. Although it has been illegal to dump waste at sea for the last 20 or so years, the law is almost impossible to enforce.

By far the most common thing found in the garbage patches is plastic. Mostly it's small particles of plastic, but sometimes very large items like fishing nets that are kilometers long can be found. The fact that it is mostly plastic is pretty amazing seeing as plastic has only become common since the Second World War. But the plastic is able to accumulate because, unlike many other type of rubbish that finds its way into the sea, there are very few organisms that can break it down.

A ghost net floating in the North Pacific garbage patch (photo Scripps Oceanography).

Plastic has a number of negative effects on marine animals. Probably the effect that most people would be familiar with is that large items of plastic, like ropes, fishing line and fishing nets can entangle marine animals. This can cause them to drown, if they breath air, it can inhibit their movements making them more vulnerable to predators and it can cause them injuries as they try to struggle free.

A beached whale's tail entangled with ropes (photo Mike Baird).

Another effect is that marine animals can consume the plastic because it looks to them like a tasty piece of food. At its most minor the animal has simply wasted its time and effort catching the plastic. But, if an animal eats enough plastic it can clog their digestive tracts making it hard for them to eat and digest real food. And it is not just the larger animals like whales, turtles and sea birds that are at risk from ingesting plastic. We know that there are some very small, even microscopic animals that are eating plastics.

Plastic bag fragments found in the contents of a turtle's stomach (photo Victoria González Carman).

Plastics have also been reported to accumulate toxic chemicals on their surface in high concentrations. And if marine animals eat the plastics the chemicals can be released during digestion and become incorporated into their tissues. So even if an animal eats plastic rarely, it can acquire a toxic dose of some chemicals that enter its system via the plastic. The research on toxic plastic is controversial and not yet widely accepted.

So plastic waste is a huge problem for life in the ocean. In fact, one researcher looking at plastics in the ocean has argued in a recent book that the biggest effect on the marine environment this century won't be climate change, it'll be plastic waste.