今回のブログでは、バラスト水にかかわる問題自体について考察し、一体どのような生物が移動しているのかについて調べてみました。北大西洋やバルト海に生息するヨーロッパ緑カニは、現在、ニュージーランドのアンティポデス諸島や南ア、南米・北米の大西洋・太平洋沿岸で発見されています。185千個程の卵を産み生態系に影響を及ぼしています。本来、日本など極東アジアに生息する黄ヒトデは、現在、オーストラリア、アラスカやヨーロッパで発見され、特にオーストラリアで絶滅危惧種を危険にさらしています。北米・南米の東海岸に生息するクシクラゲ（Sea Walnut）は、現在、黒海や地中海、バルト海、北海で見つかっており、体重の10倍の量を食べつくし食物連鎖に影響を及ぼしています。 カスピ海や黒海に生息するゼブラ貝（Zebra Mussel）は繁殖力の強い淡水性の貝ですが、現在バルト海やヨーロッパの運河で、水中の栄養を大量に消費して生態系に大きな影響を及ぼしています。これは一部の例に過ぎませんが、バラスト水管理システムの開発は生態系の維持に重要な役割を持っていることがわかります。
There has been a lot of focus on Ballast Water Management in the press recently and the Club itself has produced numerous circulars on the topic; so what better way to accompany this than with an additional blog post. However, we will not be covering any changes in laws here, or even advising on what steps need to be taken to ensure you are fully prepared (this is neatly covered in the material we have already produced). Instead we will be taking a deeper look into this issue itself and the reason this is needed in the first place. Let’s dive into the unknown and unearth some of the creatures that are causing mass disturbance as they are transported from their natural habitats and shot out of a vessel somewhere completely different. Likened, I can only imagine, to a drunken stumble around unknown territory – dazed and confused and probably about to cause some havoc.
This is by no means an exhaustive list but just a taster into what is being transferred in the exchange of ballast water from load to discharge ports around the world and what effects it can have on the eco system already in place.
European Green Crab
Native to: North East Atlantic Ocean and Baltic Sea Now found in: Antipodes, South Africa, S. America and Atlantic/Pacific coasts of N.America.
The European Green Crab has been labelled one of the top 10 most unwanted species in the world. Sounds a bit harsh but when you learn that they will feed on pretty much any organism and can be active at all times of day with reproduction producing 185,000 eggs, it’s clear to see how they fast become the neighbours from hell and completely take over. The presence of this innocent looking little crab can cause complete imbalance to the species already present in the ecosystem and also affect the profitability of the area for fisherman harvesting certain sea creatures that the crab finds tasty.
North Pacific Seastar
Native to: Japan, N.Korea, China, Far East Russia
Now found in: Australia, Alaska, Europe
Who would have thought that the humble starfish would be considered a pest? Certainly not me! But when removed from its rightful place in the sea and transported elsewhere they can cause all manner of problems from assisting in the decline of entire species (specifically the endangered hardfish from Australia) to endangering other profitable organisms with its aggressive predatory nature, causing the local economy to suffer.
Native to: East Coast North and South America
Now found in: Black Sea, Mediterranean, Baltic and North Seas
As a self-fertiliser, the Sea Walnut (or Comb Jelly) can produce rapidly and with a healthy smorgasbord of prey on offer can thrive in their new habitat. Moving at a snail’s pace, being visually impaired and not having a brain does nothing to stop this tyke as it consumes up to ten times its body weight in a single day. Again this threatens the profitability of the new found areas and diminishes vital components in the local food chain.
Native to: Caspian and Black Sea
Now found in: Baltic Sea and European canals and rivers
The Zebra Mussel differs from the other invasive species mentioned as it’s not solely the eating habits of this crustacean which causes such a disturbance, but instead their incessant reproduction and need to hug each other. When huddled together- as they seem to enjoy- they can reach over 100,000 per square metre causing an unwanted filtration system. Of course their huge appetites also play a large part, so whether it’s the food their filtering out for themselves, the food chain they’re unsettling or their interference in the water pipes with their harbour like barriers; the Zebra Mussel is definitely a force to be reckoned with.
Personally I find this topic fascinating, but whilst interesting it is also clear that moving sea creatures and disrupted local eco systems is serious business. Therefore it’s no surprise that such an importance is placed on the development of Ballast Water Management Systems.