tag:theconversation.com,2011:/uk/topics/aquatic-problems-19389/articlesaquatic problems – The Conversation2019-06-27T13:19:53Ztag:theconversation.com,2011:article/1194002019-06-27T13:19:53Z2019-06-27T13:19:53ZMicroplastic pollution and wet wipe ‘reefs’ are changing the River Thames ecosystem<figure><img src="https://images.theconversation.com/files/281587/original/file-20190627-76717-9cf5sc.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C1000%2C667&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">London - June 19 2018: Volunteers cleaning the southern shores of the Thames from waste during low tide.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/london-june-19-2018-volunteers-cleaning-1186999855?src=onblU_QN6ig7sF1ck4TN5Q-1-1&studio=1">Daniel Lange/Shutterstock</a></span></figcaption></figure><p>Ever since the issue was highlighted in shows like “Blue Planet 2”, plastic pollution in the world’s oceans has <a href="https://theconversation.com/climate-change-obsession-with-plastic-pollution-distracts-attention-from-bigger-environmental-challenges-111667">generated a wave of concern among the public</a>. It might surprise people to learn that despite comparably less attention, many of the world’s rivers are just as polluted, <a href="https://inews.co.uk/news/environment/river-mersey-more-polluted-than-the-great-pacific-garbage-patch-study-finds/">if not more so</a>.</p>
<p>Around <a href="https://www.eunomia.co.uk/reports-tools/plastics-in-the-marine-environment/">80% of marine litter starts on land</a> and rivers help transport it out to sea. In this way, plastic pollution is not just a problem for the distant open ocean – it’s an issue on our doorstep. For this reason, I chose to focus on the River Thames and the impact that plastics are having close to home.</p>
<p>There are currently no estimates for the amount of plastic in the Thames, but the world’s rivers are estimated to carry <a href="https://science.sciencemag.org/content/347/6223/768">up to 4,000 kg of plastic out to sea every day</a>. Despite much of the plastic in the Thames making it to the North Sea, a portion is permanently accumulating in the catchment.</p>
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<img alt="" src="https://images.theconversation.com/files/281381/original/file-20190626-76730-94j7pr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/281381/original/file-20190626-76730-94j7pr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281381/original/file-20190626-76730-94j7pr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281381/original/file-20190626-76730-94j7pr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281381/original/file-20190626-76730-94j7pr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281381/original/file-20190626-76730-94j7pr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281381/original/file-20190626-76730-94j7pr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">A large wet wipe reef on the south bank just upstream of Hammersmith Bridge.</span>
<span class="attribution"><span class="source">Katy McCoy</span>, <span class="license">Author provided</span></span>
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<p>Researchers recovered <a href="https://doi.org/10.1016/j.marpolbul.2013.10.035">nearly 8,500 items from the Thames riverbed</a> over three months in 2012. After 20 river cleans on the foreshore of the Thames in 2019, nearly <a href="https://www.thames21.org.uk/2019/02/the-thames-polluted-by-single-use-items/">9,000 plastic items</a> were recovered, almost all of which were single-use.</p>
<p>These were most often wet wipes, sanitary products and food packaging, which accumulate in the sediment or are deposited on the inside of bends in the river. Several members of our lab group helped with a cleanup with local environment charity <a href="https://www.thames21.org.uk/2019/04/23-thousand-wet-wipes-discovered-stretch-thames-river-bank/">Thames21</a>. On the Thames foreshore at Hammersmith in early 2019, 23,000 wipes were collected, averaging 201 wipes per square metre. You may have heard of <a href="https://theconversation.com/to-fight-the-fatbergs-we-have-to-rethink-how-we-treat-sewage-waste-84714">wet wipes forming “fatbergs” in sewers</a>, but on the banks of the Thames there are wet wipe reefs that are slowly changing the shape of the river itself.</p>
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<a href="https://images.theconversation.com/files/281378/original/file-20190626-76713-1cw667g.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/281378/original/file-20190626-76713-1cw667g.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/281378/original/file-20190626-76713-1cw667g.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=610&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281378/original/file-20190626-76713-1cw667g.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=610&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281378/original/file-20190626-76713-1cw667g.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=610&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281378/original/file-20190626-76713-1cw667g.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=766&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281378/original/file-20190626-76713-1cw667g.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=766&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281378/original/file-20190626-76713-1cw667g.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=766&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">3 mm microplastic particle recovered from the stomach of a fish compared to a 7 mm grain of rice.</span>
<span class="attribution"><span class="source">Alex McGoran</span>, <span class="license">Author provided</span></span>
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<p>As plastics move through the aquatic environment they break up. Eventually, these particles reach a microscopic scale. I have been researching microplastics, which are items smaller than 5 mm – roughly the size of a grain of rice – since 2015 and every study I have undertaken has found plastic. I have studied two UK rivers, the Thames and the Clyde, and <a href="https://doi.org/10.1016/j.marpolbul.2018.09.054">fish in both estuaries have ingested plastic.</a></p>
<h2>A river of plastic</h2>
<p>As part of my PhD, I’m researching the accumulation of microplastics in the Thames food web. When I trawl in the Thames for fish the nets are full of plastic, especially tangles of wet wipes. It’s extremely rare that we bring in a net with no litter at all.</p>
<p>Despite its murky appearance, the Thames is a diverse ecosystem that’s full of life. It supports over <a href="https://londonist.com/2014/11/what-lives-in-the-thames">120 species of fish</a> as well as many marine mammals, such as grey seals, common seals, dolphins and porpoises. Even a <a href="https://www.youtube.com/watch?v=vpusRwiT39g">beluga whale</a> was once spotted. Microplastics in the river can be ingested by all animals in the food web. Negative impacts on one part of this system can potentially cause a cascade which affects other species. </p>
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<img alt="" src="https://images.theconversation.com/files/281383/original/file-20190626-76730-birsrv.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/281383/original/file-20190626-76730-birsrv.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=417&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281383/original/file-20190626-76730-birsrv.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=417&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281383/original/file-20190626-76730-birsrv.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=417&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281383/original/file-20190626-76730-birsrv.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=525&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281383/original/file-20190626-76730-birsrv.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=525&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281383/original/file-20190626-76730-birsrv.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=525&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Microplastics accumulate in greater quantities in organisms feeding nearer the top of food webs, like seals.</span>
<span class="attribution"><span class="source">Alex McGoran</span>, <span class="license">Author provided</span></span>
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<p>Microplastics contain chemical additives which are <a href="https://theconversation.com/plastic-poisons-ocean-bacteria-that-produce-10-of-the-worlds-oxygen-and-prop-up-the-marine-food-chain-117493">released as they degrade</a> and can act as harmful pollutants in water. These toxic chemicals can be transferred to organisms if they ingest them. This forces the animal to use their energy to treat the problem, rather than growing, feeding or reproducing.</p>
<p>The amount of plastic in an animal’s gut is likely to increase higher up the food web that the animal feeds. If amphipods near the base of the foodweb ingest a few pieces of plastic then fish eating large numbers of amphipods – each likely to contain small amounts of plastic – would gradually accumulate more as they feed. Then seals at the top of the foodweb, which ingest lots of fish, would be exposed to a greater concentration still.</p>
<p>Though plastic straws and other single-use items have taken much of the blame, the plastic most commonly eaten by flatfish – <a href="https://britishseafishing.co.uk/thames-estuary/">a species often caught by fishers</a> – are fibres. These are long threads of plastic which originate in our fabrics. Straws may flow out to sea quicker but <a href="https://doi.org/10.1016/j.marpolbul.2018.09.054">during my research in the Thames</a>, I found that 80% of all plastic extracted from animals there were fibres.</p>
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<img alt="" src="https://images.theconversation.com/files/281382/original/file-20190626-76730-9tl1dz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/281382/original/file-20190626-76730-9tl1dz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=405&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281382/original/file-20190626-76730-9tl1dz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=405&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281382/original/file-20190626-76730-9tl1dz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=405&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281382/original/file-20190626-76730-9tl1dz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=509&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281382/original/file-20190626-76730-9tl1dz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=509&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281382/original/file-20190626-76730-9tl1dz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=509&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Example of some of the plastic found in UK fish – here a plaice is shown with a tangle of fibres.</span>
<span class="attribution"><span class="source">Alex McGoran</span>, <span class="license">Author provided</span></span>
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<p>Hundreds of thousands of these tiny plastic fibres can drain into rivers with every use of our washing machines. Wastewater treatment plants catch the majority of these fibres, but with so many people washing their clothes in the Thames catchment area, a vast number of fibres are still entering the river and making their way out to sea. </p>
<p>Washing clothes less often and using products designed to capture fibres in the wash can prevent them getting to rivers or the sea, such as the <a href="https://guppyfriend.com/en/">guppy friend bag</a> and <a href="https://coraball.com/">coraball</a>. We may rightly fret about the impact of our plastic on life in the ocean, but it’s time we realised that the plastic pollution crisis is <a href="https://inews.co.uk/news/environment/river-mersey-more-polluted-than-the-great-pacific-garbage-patch-study-finds/">a lot closer to home than we care to think.</a></p><img src="https://counter.theconversation.com/content/119400/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Alex McGoran receives funding from NERC through the London NERC DTP in the form of a research grant and stipend to support her research at the Natural History Museum, London and Royal Holloway, University of London. She also receives additional funding through a CASE partnership, organised with the London NERC DTP, with The Fishmonger's Company.</span></em></p>It’s not just the ocean we need to worry about – plastic is accumulating in the world’s rivers, too.Alex McGoran, PhD Researcher in Aquatic Pollution, Royal Holloway University of LondonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1096532019-01-22T04:24:28Z2019-01-22T04:24:28ZWhy we don’t know if Irukandji jellyfish are moving south<p>Reports that <a href="https://www.australiangeographic.com.au/news/2018/04/irukandji-jellyfish-everything-you-need-to-know/">Irukandji</a> jellyfish might be <a href="https://www.abc.net.au/news/2019-01-06/lifesavers-sweep-for-irukandji-jellyfish-at-fraser-island-qld/10687744">moving south</a> may be panicking people unnecessarily. It’s almost impossible to tell where the tiny jellyfish are along our coast, but that could change with new technology that can “sweep” the ocean for traces of DNA.</p>
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Read more:
<a href="https://theconversation.com/will-venomous-irukandji-jellyfish-reach-south-east-queensland-19372">Will venomous Irukandji jellyfish reach south-east Queensland?</a>
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<p>Since the Christmas period <a href="https://www.abc.net.au/news/2019-01-05/irukandji-jellyfish-found-in-greater-numbers-in-queensland-south/10686956">nearly twice</a> the usual number of people have suffered the excruciating consequences of being stung by Irukandji. The stings are rarely fatal, but can require medical evacuation and hospitalisation.</p>
<p>These reports of southward movement are almost a yearly tradition, often sensational, and accompanied by varying expert opinions about whether climate change is driving these dangerous tropical animals south, towards the lucrative beach tourism destinations of southeast Queensland.</p>
<p>But simply counting the number of Irukandji found, or the number of reported stings, tells us very little about where the species can be found. </p>
<h2>A simple question but difficult answer</h2>
<p>“Where are Irukandji located, and is that changing?”, might seem like a straightforward question. Unfortunately, finding the answer is not easy. The only definitive way to determine where they are is to catch them – but that poses many challenges.</p>
<p>Irukandji are tiny (most are about 1cm in diameter) and transparent. Along beaches they are usually sampled by a person wading through shallow water towing a fine net. This is often done by lifeguards at beaches in northern Queensland to help manage risk. </p>
<p>Irukandji are also attracted to light, so further offshore they can be concentrated by deploying lights over the sides of boats and then scooped up in nets. The problem is they’re are often very sparsely scattered, even in places we know they regularly occur, such as Queensland’s north. As with any rare species, catching them can confirm their presence, but failure to catch them does not guarantee their absence. Collecting Irukandji in an ocean environment is truly like searching for the proverbial needle in a haystack. </p>
<p>Another method is to infer their presence from hospital records and media reports of Irukandji syndrome, the suite of symptoms caused by their sting, but this method has major pitfalls. There is often a delay of around 30 minutes between the initial sting, which is usually mild, and the onset of Irukandji syndrome. Hence the animal that caused the symptoms is almost never caught and we cannot verify the species responsible. </p>
<p>Indeed, we do not know whether Irukandji are the only marine organisms to cause Irukandji syndrome. For example, the <a href="http://lifesaving.com.au/wp-content/uploads/Marine-Stinger-Fact-Sheets-Morbakka.pdf">Moreton Bay Fire Jelly</a>, a species of jellyfish related to Irukandji only found in southeast Queensland, and even bluebottles, which in the past couple of weeks have stung more than 10,000 people along Australia’s east coast, have also been suggested to occasionally cause Irukandji-like symptoms.</p>
<h2>eDNA to save the day</h2>
<p>Emerging technology may be the key to properly mapping Irukandji distribution. All animals shed DNA in large quantities into their environment (for example, skin cells and hair by humans). This DNA is called <a href="https://www.jcu.edu.au/brighter/articles/what-is-edna">environmental DNA</a>) (or eDNA) and genetic techniques are now so powerful that they can detect even trace amounts. </p>
<p>In the sea, this means we can determine whether an animal has been in an area by collecting water samples and testing them for the presence of the target species’ DNA. This technology is exciting because it provides a major upgrade in our ability to detect rare species. Moreover, it is relatively simple to train people to collect and process water samples, the results can be available within hours, and the equipment needed to analyse the samples is becoming increasingly affordable.</p>
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Read more:
<a href="https://theconversation.com/the-blue-bottles-are-coming-but-what-exactly-are-these-creatures-48675">The blue bottles are coming, but what exactly are these creatures?</a>
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<p>This means an eDNA monitoring program could be easily established in Southeast Queensland to monitor the occurrence and, importantly, changes in the distribution of Irukandji jellyfish. This is because Irukandji leave traces of their genetic code in the water as they swim.</p>
<p>Developing the eDNA technology for use with Irukandji would cost a few hundred thousand dollars – a relatively small price to pay to improve public safety, to provide stakeholders with some control over their ability to detect Irukandji, and to create some certainty around the long-term distribution of these animals.</p>
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<p><em>The authors would like to acknowledge the significant contribution to this article by Professor Mike Kingsford (James Cook University).</em></p><img src="https://counter.theconversation.com/content/109653/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kylie Pitt receives funding from the National Environmental Science Program. </span></em></p><p class="fine-print"><em><span>Dean Jerry does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The irukandji jellyfish can be deadly and particularly hard to trace. However, emerging technology offers a solution.Kylie Pitt, Professor, Griffith UniversityDean Jerry, Associate Professor of Marine Biology and Aquaculture, James Cook UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/829472017-09-04T15:41:39Z2017-09-04T15:41:39ZEthiopia’s Lake Tana is losing the fight to water hyacinth<figure><img src="https://images.theconversation.com/files/184000/original/file-20170830-23702-17vlg7u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The aquatic weed water hyacinth is causing major problems in Ethiopia's Lake Tana.</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>Lake Tana is the largest lake in Ethiopia. It holds 50% of <a href="https://cgspace.cgiar.org/handle/10568/21499">the country’s fresh water</a>. It is also the source of the Blue Nile, which contributes up to 60% of the <a href="https://link.springer.com/chapter/10.1007/978-1-4020-9726-3_9">Nile’s water</a>. Not only is the lake important as a water source for over <a href="http://mandalaprojects.com/ice/ice-cases/bluenile.htm">123 million people</a> in the Nile Basin, it is also a source of food in the form of fish. But weeds are threatening this life-giving resource.</p>
<p>The lake has been listed in the top 250 lake regions of <a href="https://cgspace.cgiar.org/handle/10568/21499">Global Importance for Biodiversity</a>. It has 28 species of fish, of which <a href="https://link.springer.com/chapter/10.1007/978-3-319-45755-0_12">21 are endemic</a>. Commercially, the lake’s most important fishes include the large African barbs, Nile tilapia and African catfish. The annual commercial value of fish production at Lake Tana is about USD$<a href="http://www.fao.org/docrep/v6718e/v6718E01.htm#12">1.1 million</a>. </p>
<p>The potential fish production of the lake is estimated to be <a href="http://www.fao.org/fi/oldsite/FCP/en/ETH/body.htm">13 000 tons yearly</a>. But its current fish production is less than 1000 tons a year. <a href="http://onlinelibrary.wiley.com/doi/10.1002/ldr.2730/abstract">Recent studies</a> show a serious decline in fish stocks due to the spread of the aquatic weed water hyacinth around fish spawning grounds.</p>
<p>Water hyacinth, <em>Eichhornia crassipes</em>, is an exotic free-floating invasive plant that is native to South America. People who tend aquariums and gardens are believed to have spread the plant inadvertently across the Atlantic to <a href="https://link.springer.com/content/pdf/10.1007%2F978-3-319-55396-2_9.pdf">Africa and Asia</a>. </p>
<p>It restricts water flow, blocks sunlight from reaching native water plants and depletes the oxygen in the water - often choking aquatic animals like <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2427.2009.02294.x/abstract">fish</a>. It also has an economic impact by interfering with navigation, irrigation, power generation and fishery.</p>
<h2>The infestation</h2>
<p>The weed forms thick mats that cover the open water. <a href="http://www.netjournals.org/pdf/NJAS/2017/1/16-039.pdf">Recent data</a> show that Lake Tana is critically infested with water hyacinth and it’s putting the aquatic biodiversity at extreme risk.</p>
<p>In 2011, the <a href="http://www.ethiopia.gov.et/amhara-regional-state">Regional Environmental Bureau</a> named water hyacinth as <a href="http://allafrica.com/stories/201708080175.html">the most dangerous weed</a> affecting Lake Tana. By then, about <a href="https://www.peertechz.com/Allergy/Allergy-1-103.php">20 000 hectares</a> of the north-eastern shore of the lake was infested. In 2014, researchers from Ethiopia <a href="http://www.bdu.edu.et/sites/default/files/Water_Hyacinth_Lake%20Tana_Report%20Series%201.pdf">found out</a> that about one-third of the lake’s shoreline, around 128km, was invaded by water hyacinth.</p>
<p>In just two years, the estimated coverage of the weed doubled from <a href="http://www.bdu.edu.et/sites/default/files/Water_Hyacinth_Lake%20Tana_Report%20Series%201.pdf">20 000 to 40 000 hectares</a>. The weed is now estimated to cover <a href="http://www.netjournals.org/pdf/NJAS/2017/1/16-039.pdf">50 000 hectares</a> of the lake. To make matters worse, inflowing rivers carry heavy loads of soil <a href="https://link.springer.com/chapter/10.1007/978-1-4020-9726-3_9">and suspended sediment</a> into the lake, which affects the water quality and creates favourable conditions for the spread of the weed.</p>
<p>The release of <a href="https://link.springer.com/chapter/10.1007%2F978-3-319-45755-0_10">untreated waste water</a> from industries around the lake adds to the deterioration of the lake ecosystem. As a consequence, the lake has lost 75% of its fish stock <a href="http://www.sciencedirect.com/science/article/pii/S0006320703001988">in recent years</a>. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/183197/original/file-20170823-6585-1a8cdw7.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/183197/original/file-20170823-6585-1a8cdw7.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/183197/original/file-20170823-6585-1a8cdw7.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=443&fit=crop&dpr=1 600w, https://images.theconversation.com/files/183197/original/file-20170823-6585-1a8cdw7.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=443&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/183197/original/file-20170823-6585-1a8cdw7.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=443&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/183197/original/file-20170823-6585-1a8cdw7.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=557&fit=crop&dpr=1 754w, https://images.theconversation.com/files/183197/original/file-20170823-6585-1a8cdw7.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=557&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/183197/original/file-20170823-6585-1a8cdw7.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=557&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Farmers trying to remove water hyacinth from Lake Tana.</span>
<span class="attribution"><a class="source" href="https://www.youtube.com/watch?v=6OW4DMuolYk">CGTN Africa</a></span>
</figcaption>
</figure>
<h2>Control measures</h2>
<p>A water hyacinth infestation is hard to get rid of. But there are three ways to do this: removal, chemical spraying (using herbicides) and biological control. </p>
<p>Removing the weed, either manually or using machines, could reduce coverage and slow its spread. But it’s expensive and takes time. Local authorities are mobilising an estimated <a href="http://www.bdu.edu.et/sites/default/files/Water_Hyacinth_Lake%20Tana_Report%20Series%201.pdf">162 000 people</a> to remove the weed by hand. This happens only when the lake shores are accessible and when farmers have time.</p>
<p><a href="https://www.britannica.com/place/Lake-Victoria">Lake Victoria</a>, lying in Tanzania, Uganda and Kenya, offers lessons for dealing with the water hyacinth problem. An estimated 60 000 hectares is covered by the weed in Kenya alone. A weed harvesting machine can clear only 10 hectares a day, so it would take 6 000 days (more than 16 years) to <a href="http://www.nation.co.ke/counties/kisumu/removal-of-water-hyacinth-lake-victoria-could-take-longer/1954182-3804090-mw2c6z/index.html">remove the weed</a> entirely. Methods like biological control have been shown to be more <a href="http://www.abc.net.au/science/slab/hyacinth/">effective</a>. </p>
<p>Herbicides have been widely used to reduce the spread of the weed, but they may harm the environment. They can kill native plants that are necessary for a healthy functioning of <a href="http://www.spc.ichemejournals.com/article/S2352-5509(15)00010-X/pdf">the lake’s ecosystem</a>.</p>
<p>This control method is expensive for developing countries and requires highly skilled people. In Sudan, the costs of chemical treatment for water hyacinth control were estimated to be <a href="https://www.invasive.org/proceedings/pdfs/6_491-496.pdf">£1 million each year</a>.</p>
<h2>The best approach</h2>
<p>Biological control has been widely used. It appears to be the most economical and effective approach to manage water hyacinth in the long term. It uses natural enemies, with little cost and usually no negative environmental impact. Two weevil – or beetle – species, Neochetina eichhorniae and Neochetina bruchi, have been widely used with success. They have shrunk the coverage of the weed and controlled its spread <a href="http://ageconsearch.umn.edu/bitstream/135372/2/PR102.pdf#page=8">in 33 countries</a>, including the United States, Uganda, Nigeria, Ghana, India and Australia. But this method takes years of work by the insect to clear the weed. For instance, the weevils took two years to control the weed at Lake Victoria <a href="http://www.abc.net.au/science/slab/hyacinth/">in Uganda</a>. </p>
<p>Neochetina weevils eat only water hyacinth. <a href="http://www.fao.org/docrep/006/y5031e/y5031e0c.htm">Studies</a> show that these weevils rely on the water hyacinth’s root system for crucial stages of growing. They feed heavily on the plant tissue: larvae eat the inside of the plant and adults eat the outside. Feeding damage by both life stages inhibits the growth of the plant by slowing the flowering process. </p>
<p>Biological control using weevils has been <a href="http://www.abc.net.au/science/slab/hyacinth/">successful in Lake Victoria</a>. A recent study on the adaptability and efficacy of weevils for water hyacinth control in the Ethiopian Rift Valley showed <a href="http://www.sciencedirect.com/science/article/pii/S0261219415300557">promising results</a>. Potential negative effects, however, should to be studied before realising the weevils to new environment. Once the weevils are released, there is no operational cost as they naturally reproduce and continue feeding until all the weed is cleared. </p>
<p>Researchers are also looking at the potential of <a href="http://www.apms.org/japm/vol51/japm-51-02-109-121.pdf">using weevils</a> for water hyacinth control around Lake Tana. At least <a href="https://en.nabu.de/projects/ethiopia/tana/area/population.html">2-3 million</a> people living around the lake will be relying on the success of all these efforts.</p><img src="https://counter.theconversation.com/content/82947/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Dr Solomon Kibret is a member of the Global Coalition for Lake Tana Restoration, a not-for-profit group supporting environmental and watershed management activities to restore Lake Tana's ecosystem in Ethiopia. </span></em></p>Lake Tana in Ethiopia has been massively affected by the invasive weed, water hyacinth. Control methods are available but there are challenges.Solomon Kibret, Postdoctoral researcher, University of California, IrvineLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/495852015-10-22T19:07:29Z2015-10-22T19:07:29ZWatch out, Australia: a red-hot summer means blue-green algae<figure><img src="https://images.theconversation.com/files/99294/original/image-20151022-19646-167uhf4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Pretty, but also pretty nasty.</span> <span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File%3ACSIRO_ScienceImage_4628_Bluegreen_algae_in_irrigation_drain.jpg">Willem van Aken/CSIRO/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>As the Bureau of Meteorology has <a href="http://www.bom.gov.au/climate/enso/archive/ensowrap_20150915.pdf">already warned us</a>, Australia is in for a hot, dry summer as the <a href="https://theconversation.com/when-the-indian-ocean-and-el-nino-join-forces-things-can-get-hot-and-dry-48969">current El Niño</a> takes hold. Those conditions are ideal for blue-green algae to bloom in lakes, ponds and reservoirs.</p>
<p>Photosynthesising bacteria, also known as cyanobacteria, are found in all aquatic environments from the tropics to the poles. Most species have no adverse impact on the environment, but a few have nastier effects, and some are toxic to humans and animals. </p>
<p>Blue-green algae can form vast “blooms”, some large enough to be seen from space. In the Australian drought summers of 2009 and 2010, for example, hundreds of kilometres of the Murray River suffered <a href="http://www.ncbi.nlm.nih.gov/pubmed/22081581,%20http://www.abc.net.au/news/2009-03-28/potentially-toxic-algae-bloom-threatens-murray/1633630">major cyanobacterial blooms</a>, which hampered the use of water for drinking, agriculture and recreation.</p>
<p>These blooms occur mostly in still water bodies and can be found throughout Australia. Some blue-green algae form visible surface scums, while others remain hidden in the water column. Some live in freshwater; others float in the open ocean or even live on the sea bed.</p>
<h2>Tiny and toxic</h2>
<p>The toxins produced by some blue-green algae can affect the nervous system, the liver and kidneys, or be toxic to cells more generally. Humans can be affected by drinking contaminated water or eating affected shellfish. Direct contact with water can also cause itching and rashes. Worse still, the toxins can remain in the water even after the blue-green algae themselves have vanished - in some cases for weeks, depending on the conditions. </p>
<p>Larger blooms tend to occur where there is an excess of nutrients, often the result of fertiliser runoff from intensive agriculture or other degradation of the catchment system. This means that, throughout Australia, the <a href="http://www.ncbi.nlm.nih.gov/pubmed/20598731">potential for blooms is increasing</a>. </p>
<p>Water temperature also influences algal blooms, for two reasons. First, blue-green algae grow faster in warmer water and, second, warmer temperatures increase “thermal stratification”, in which a warmer surface layer overlies deeper, cooler water. Stratification allows cyanobacteria to flourish in the warmer sunlit surface waters because of their unique ability to make themselves float.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/99295/original/image-20151022-7999-p8yjxy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/99295/original/image-20151022-7999-p8yjxy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/99295/original/image-20151022-7999-p8yjxy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/99295/original/image-20151022-7999-p8yjxy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/99295/original/image-20151022-7999-p8yjxy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/99295/original/image-20151022-7999-p8yjxy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/99295/original/image-20151022-7999-p8yjxy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/99295/original/image-20151022-7999-p8yjxy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1005&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">This bloom in Western Australia’s Shark Bay was big enough for NASA to spot it from space.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File%3AShark_Bay_Phytoplankton_in_Bloom.jpg">NASA</a></span>
</figcaption>
</figure>
<p>So how do you steer clear of blue-green algae? The obvious tips are to avoid drinking untreated water from still, calm water bodies, and to be mindful of children or dogs playing by the water.</p>
<p>Green surface scum is the most obvious tell-tale sign of an algal bloom, but not all species of cyanobacteria form scums. Discolouration of the water, particularly a green colour, can also indicate the presence of blue-green algae. Some species, such as <em>Microcystis</em>, give off a distinctive odour, although some other blue-green algae also create musty-smelling chemicals that are non-toxic.</p>
<p>It is comforting to know that if water quality is at risk, your local water authority is probably on top of it already, and will typically erect warning signs each summer. Many lakes and reservoirs are routinely closed for recreational use to protect the public from toxic blooms during the hotter months. </p>
<h2>Blooming hot</h2>
<p>The forecast hot, dry summer is likely to be a boon for blooms, given that blue-green algae prefer warm, still water. This means that areas that typically get algal blooms might find they are bigger and longer-lasting this summer. In Australia’s southern states, the blooms might also start earlier in the summer and last longer into autumn. </p>
<p>But the scale of blooms also depends on nutrients, so reducing the amount of nutrients that are washed off the land during rainfall events can provide a way of controlling them. This can be done by reducing land degradation, for example, reducing erosion, creating vegetation buffer zones along river banks, and avoiding excessive fertiliser use. </p>
<p>Some of these processes will take time to implement and therefore won’t help us this summer. But combating cyanobacteria in the longer term will help to protect the environment, allow continued recreational use of water and, most importantly, protect our precious drinking water.</p><img src="https://counter.theconversation.com/content/49585/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Anusuya Willis works for the Australian Rivers Institute, Griffith University, and receives funding from the Australian Research Council and Seqwater. Anusuya is also a member of the Greens political party. </span></em></p><p class="fine-print"><em><span>Michele Burford receives funding from the Australian Research Council and Seqwater</span></em></p>With El Niño ramping up, Australia is in for a long, hot, dry summer - perfect conditions for blue-green algae. And that innocuous-looking pond scum can pack a toxic punch if you’re not careful.Anusuya Willis, Research Fellow, Australian Rivers Institute, Griffith UniversityMichele Burford, Professor of Aquatic Ecology, Griffith UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/448032015-08-12T04:37:02Z2015-08-12T04:37:02ZHow Africa can grow its own solutions to the continent’s aquatic weed problems<figure><img src="https://images.theconversation.com/files/91416/original/image-20150811-11077-b11x1u.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Megamelus scutellaris insects fighting aquatic weeds.</span> <span class="attribution"><span class="source">Philip Weyl</span></span></figcaption></figure><p>Aquatic weeds throughout the world pose significant threats to water security. These threats are not only to biodiversity and ecological processes but also land and river communities that rely heavily on water resources – especially in <a href="http://www.scielo.org.za/scielo.php?pid=S1816-79502012000200019&script=sci_arttext">developing countries</a>. Wetlands, rivers and lakes throughout Africa have been <a href="http://www.fao.org/docrep/006/y4270e/y4270e03.htm">invaded</a> by several aquatic weed species. </p>
<p>These include some of the most damaging <a href="http://www.cabi.org/isc/FullTextPDF/2003/20033109570.pdf">worldwide</a>, such as water hyacinth, Kariba weed and water lettuce. These aquatic weeds not only threaten one of Africa’s most valuable resources – water – but also the well-being of these communities that rely heavily on the abundant resources that Africa’s waters offer.</p>
<p>Invasive aquatic weeds are an ongoing problem. For example, in South Africa alone, more than 400 sites are infested with alien aquatic plants. Every year new sites are being recorded, some of them having major <a href="http://www.fao.org/docrep/006/y4270e/y4270e03.htm">socioeconomic implications</a>. The impact that aquatic weeds have include: </p>
<ul>
<li><p>reducing water storage capacity, specially potable water; </p></li>
<li><p>impeding flow and interfering with navigation; </p></li>
<li><p>promoting habitat for mosquitoes; and </p></li>
<li><p>spreading water borne disease.</p></li>
</ul>
<h2>Biological control is the way forward</h2>
<p>Control technologies <a href="https://pubs.ext.vt.edu/420/420-251/420-251.html">exist</a> for these weeds. These are chemical, mechanical and biological control methods. Chemical control involves the use of registered herbicides, which are usually sprayed directly onto the plants. Mechanical control is the use of mechanical harvesters or manual labour to remove plants from the system where they are problematic.</p>
<p>Biological control is the use of host specific organisms, usually insects, in weed biological control. Many herbivorous insects have evolved and developed an intricate relationship with plants. Often, the herbivore is bound to a small group of closely related plant species and even a single species. Biological control takes advantage of this close relationship. </p>
<p>Scientists can spend around five years on host specificity testing, impact assessments and a cost-benefit analysis. Before release, the biological control agent must be host-specific, damaging to the plant population and the benefits must outweigh the potential risks.</p>
<p>These have been widely <a href="http://www.icid.org/weed_report.pdf">implemented</a> throughout Africa. Even though these control efforts have been successful, there is often no continuity in these programmes. Many of them are externally funded and when the funding dries up, programmes are discontinued. When more funding becomes available the wheel is reinvented despite extensive research being <a href="http://www.sajs.co.za/sites/default/files/publications/pdf/Moran_News%20and%20Views.pdf">available</a>. </p>
<p>This is one of the main reasons biological control is the most cost-effective and sustainable method of control. Irrespective of funding cycles, the host specific biological control agents work tirelessly, feeding on their target weed. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/91417/original/image-20150811-11110-noa4u1.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/91417/original/image-20150811-11110-noa4u1.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/91417/original/image-20150811-11110-noa4u1.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/91417/original/image-20150811-11110-noa4u1.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/91417/original/image-20150811-11110-noa4u1.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/91417/original/image-20150811-11110-noa4u1.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/91417/original/image-20150811-11110-noa4u1.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/91417/original/image-20150811-11110-noa4u1.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Aquatic weed fighters released on Lake Victoria.</span>
<span class="attribution"><span class="source">Philip Weyl</span></span>
</figcaption>
</figure>
<p>One example of biological control is with the invasive plant water hyacinth which has infested Lake Victoria. Aquatic weeds were a massive problem in this region, affecting the <a href="http://www.rff.org/rff/Documents/EfD-DP-08-05.pdf">local fishing industry</a>. It was brought down from 20,000 hectares to just 2000 over a couple of years using just two biological control agents. These were two <a href="http://www.abc.net.au/science/slab/hyacinth/">weevil</a> species, <em>Neochetina eichhoriae</em> and <em>N. bruchi</em>. </p>
<p>Massive weed infestations in Lake Kariba, where the Kariba weed (<em>Salvinia molesta</em>) got its common name, were reduced through biological control <a href="http://www.cabi.org/isc/datasheet/48447">alone</a>. It reached such low levels that any impact to the community and ecosystem are <a href="http://www.tandfonline.com/doi/pdf/10.1080/096708797228780">considered negligible</a>.</p>
<h2>Time for Africa to come together</h2>
<p>With the growing level of research and understanding of the mechanisms behind the invasion of many these aquatic weeds, there is no reason for them to be a problem. </p>
<p>By understanding the processes behind both successful and unsuccessful biological control programmes, current management plans can be adapted for better results. With the ongoing research in biological control in South Africa, new agents are being cleared for release on a regular basis. The most recent being the delphacid leaf hopper (<em>Megamelus scutellaris</em>) <a href="http://www.invasives.org.za/item/568-deputy-minister-launches-water-hyacinth-plant-hopper.html">against</a> water hyacinth.</p>
<p>One <a href="http://www.ru.ac.za/zoologyandentomology/research/biologicalcontrolresearchgroup/">unit</a> in particular is committed to solving aquatic weed problems in Africa using knowledge and capacity grown in Africa.</p>
<p>This research group has already grown capacity in Africa by training master’s and PhD students in aquatic weed biological control from several countries including Mozambique, Ghana, Cameroon, South Africa and Zimbabwe. The group is also in the process of creating a clearing house for the knowledge on the identification, impacts and control of these weeds. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/90306/original/image-20150730-25757-134ceps.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/90306/original/image-20150730-25757-134ceps.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/90306/original/image-20150730-25757-134ceps.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/90306/original/image-20150730-25757-134ceps.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/90306/original/image-20150730-25757-134ceps.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/90306/original/image-20150730-25757-134ceps.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/90306/original/image-20150730-25757-134ceps.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Unless Africa can come together to deal with the problem, aquatic weeds will continue to cause problems for many Africans.</span>
<span class="attribution"><span class="source">Philip Weyl</span></span>
</figcaption>
</figure>
<p>This would involve setting up networks bringing the right people together, facilitating the control efforts and, probably most importantly, sourcing funding. There is a belief that within Africa there is a growing capacity, knowledge and enthusiasm to control these weeds. In line with the <a href="http://www.millenniumassessment.org/documents/document.358.aspx.pdf">Millennium Assessment Plan</a>, knowledge created in Africa to solve Africa’s aquatic weed problems is the way forward. </p>
<p>Initially, the clearing house will be set up in South Africa for the spreading of appropriate technology and knowledge. That is with the hope that Africa will take responsibility for its own aquatic weed problems. </p>
<p>The vision and ultimate goal is for there to be aquatic weed combatants at institutions around Africa. The knowledge grown in Africa should be freely available for people though out the continent willing to take responsibility of a problem in their country, region or maybe just the pond in their back garden.</p>
<p>As long as Africa comes together, there is no reason for aquatic weeds to still be a problem.</p><img src="https://counter.theconversation.com/content/44803/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Philip Weyl works for Biological Control Research Group and Rhodes University. He receives funding from both Rhodes University and The Working for Water Programme of the Natural Resource Management Programmes (Department of Environmental Affairs), South Africa.</span></em></p>Biological control is the best way to combat aquatic weeds in African water.Philip Weyl, Postdoctoral Researcher, Entomology and Biological Control, Rhodes UniversityLicensed as Creative Commons – attribution, no derivatives.