“水富营养化”过程中，藻类封闭住水体，近来，这一问题很频繁地发生。
藻类的艺术表现形式
鱼类是最容易受到它的危害，据了解，野生的哺乳动物和狗也会白白送命。蓝藻可引起人类出现不适症状，如皮疹、发烧、头晕、腹泻和呕吐。据英国普利茅斯大学研究，即便常见的藻类似乎都能降低鱼的生育能力，很可能对人类都有相同的危害。
不只是英国受到“水富营养化”威胁，从北爱尔兰到格陵兰的迪斯科湾，它们都在同绿色威胁做斗争，这不只是水体清新的问题，还记住北京奥运会吗？由于当时全世界最严重的藻华，主办方差一点取消帆船赛事。海藻场对水体富营养化和藻类疯长的责任难以推脱。
令人担心的是，正处在藻类盛长的季节，我们却没有觉察到。去年，环境机构接受了225例关于藻类大量繁殖导致鱼类死亡的报告，发生在英国和威尔士的河流、湖泊和水库。截止到目前，共计83起藻类危害事件，待到夏季情况会更糟。
威尔士环境局戴维斯称，污水中25%的营养成分来自洗涤剂，这些洗涤剂用在洗衣机和洗碗机中。
科学家希望藻类通过吸收二氧化碳固定来自大气中的温室气体，并把它存储在海底对减缓全球变暖有益。几年前，为了刺激浮游植物的生长，大量的铁被倒入南大洋中。该理论认为浮游生物生长的越快，二氧化碳就会更多地输送到海洋底部。
但是，印度国家海洋研究所和德国极地和海洋研究所研究发现，其它的微生物吃掉藻类，因此不能把二氧化碳固定在海底。
与此同时，Richard Branson认为，藻类可为飞机提供一种气候友好型燃料，甚至美国海军在今年夏季早期就开始尝试藻类来源的生物燃料。（生物探索译 Pobee）
生物探索推荐英文原文
Facing a summer of algae
How children grow up. Not so long ago, my eldest son William would have associated slime with Fungus the Bogeyman. Now, having just sat his GCSEs, he says “eutrophication”. This is the process by which water becomes choked by algae, and it has been happening a lot recently.
A blue-green scum has overmantled the Norfolk Broads. Oxygen is being pumped into the Serpentine, in an effort to keep the lake in London’s Hyde Park fit for swimmers. In Scotland, Stirling Council has put up hazard notices around Loch Coulter. Some kinds of algae can be pretty nasty.
Fish are obviously the most vulnerable to it, but wild mammals and dogs have also been known to die. Blue-green algae can cause humans to suffer skin rashes, fever, dizziness, diarrhoea and vomiting. According to research from Plymouth University, even common algae appear to reduce fertility in fish – on account of the oestrogen they release – and could have the same effect on people.
At the beginning of our history, we emerged from the primordial slime, and now it looks as though it is coming back to get us.
It’s not only Britain that is affected. From Lake Eire in North America to Disko Bay in Greenland, they are fighting the green peril. Nor is it just an issue for fresh water.
Remember the Beijing Olympics? The organisers nearly had to call off the sailing events because of the world’s biggest algae bloom, off the coast of Qingdao, which was visible from space. A seaweed farm that had enriched the waters and led to the growth of algae was to blame.
So be afraid. We are now in the prime season for algae, and have probably seen nothing yet. Last year, the Environmental Agency received 225 reports of algal blooms killing fish on English and Welsh rivers, lakes and reservoirs. So far this year, the tally has been 83. It’s early days. The summer months are the worst.
Algae love sunny weather; they reproduce like crazy when it is accompanied by pollution. The latter can take many forms. Around Llanberis, Environmental Agency Wales is asking local people to reduce their use of washing machines and dishwashers: the phosphates that they discharge send the algae wild.
“We know that around 25 per cent of nutrients in sewage effluent come from modern detergents, which we use in washing machines and dishwashers,” says Meic Davies of Environment Agency Wales.
Farmers are doing better than they were. There are now stringent regulations to control the use of fertilisers in some areas, to stop nitrates entering drinking water; spreaders are only allowed out in wet seasons, when the fertiliser will be absorbed by the land.
These restrictions have coincided with a spike in the cost of fertiliser, which has in any case discouraged overuse. One of the many woes of dairy farmers is the demand that they should build expensive slurry tanks to store waste and reduce pollution.
But despite these measures, agriculture isn’t off the hook. Sudden torrential downpours, of the kind we seem to be experiencing more often these days, wash valuable soil off fields and into water courses: algae thrive on the nutrients that were intended to benefit the crops.
But in a world of hunger and rising food prices, it is difficult to balance the demand for increased productivity with the need to reduce fertiliser use – without, that is, licensing GM crops.
And so, instead of cruising through gin-clear waters, holidaymakers, who have booked into the Norfolk Broads, are forced to contemplate a repellent, scummy scene. It must seem as though a green mutant has invaded from outer space. To the people suffering this horror, it may be little comfort to reflect that the circumstances that cause algal blooms, and other infestations, tend to be localised.
Last year, the beach that I like outside Ramsgate in Kent was ankle deep in rotting seaweed; the council employed a man to scoop it up in a digger and dump it out to sea (from which it would wash back again, if the tides were right.) This year, the problem has either gone away or moved elsewhere. Algae, too, move in mysterious ways. Last August, fish were dying in two lakes in south-east London; those same lakes are now fine.
Lakes, particularly when the streams feeding them are sluggish, do have a tendency to mantel over – ask the numerous country-house owners who struggle to keep the sheet of water in their parks as Capability Brown intended.
But in general, Britain’s waterways are in far better condition than they have been since the dawn of the Industrial Revolution. The other day, I took a boat trip from Westminster to Kew: throughout its length, the Thames is now haunted by cormorants and herons, which would not be there if it weren’t full of fish.
Besides, while few of us would feel instinctively drawn to slime, it may be time to view it in a more friendly light. One of the most basic building blocks of life, sometimes single-celled, could possibly come to the rescue of the most sophisticated species on earth.
Scientists are hoping that algae, which absorb carbon dioxide, might be useful in trapping the gas from the atmosphere and burying it on the seabed, where it cannot contribute to global warming. Several years ago, there was an expedition to pour iron into the Southern Ocean, a vast area that encircles Antarctica, to stimulate a giant bloom of phytoplankton. The theory was that by stimulating the growth of more phytoplankton, more CO₂ might be sent to the bottom of the ocean.
But the experiment, conducted by India’s National Institute of Oceanography and the Alfred Wegener Institute for Polar and Marine Research in Germany, proved disappointing when it was found that blooms of the wrong sort of algae had been induced (the algae were eaten by other tiny organisms, not dispatching the carbon dioxide to the bottom of the ocean, as intended). Scientists are still on the case.
Meanwhile, Richard Branson believes that algae could provide a climate-friendly fuel for aircraft, and even the American Navy – hardly the most obviously green of consumers – began trials of an algae-based biofuel earlier this summer. Solazyme, the company which supplied the fuel, has used algae to make a kind of “flour”. Yum, slime sponge.
Algae are also being made to produce the stuff that partly causes the bloom problem in the first place: fertiliser. Alas, algal fertilisers won’t reduce the amount of algal bloom that ends up disfiguring our watercourses, but, given the large volume of fossil fuel used in making conventional fertiliser, it will help the environment in other ways.
So cheer up. Algae are a part of nature and thrive on the very thing that holidaymakers most like. If we’d had a wet summer, the scum problem would have solved itself – only not many holidaymakers would have been out and about to see it.
