The oceans are so big that in the past they were believed to be inexhaustible, there would always be enough fish and it would be easy to dump waste and toxins because they simply disappear in a large amount of water. But that’s not true. What you pour into the sea does not just disappear. Toxins and plastic waste pollute the oceans for a long time. , Seas are very sensitive systems. One of the biggest threats to our seas is global warming. With it, the temperature of the seawater rises. For this reason, native fish species that prefer cool water temperatures are drawn to other regions, such as cod. To the north, where the water is colder.
In addition, the greenhouse gas carbon dioxide acidifies the oceans. It passes from the air at the sea surface into the sea water and is dissolved there and thus bound in the water. This is actually good for the air because it reduces the number of greenhouse gases in the atmosphere and thus slows down global warming. But: When carbon dioxide is dissolved in seawater, it produces carbonic acid, as in mineral water. As the name suggests, this is sour.
If the ocean becomes more acidic, the calcification of sea creatures such as corals, shells, and snails will be disturbed. Especially coral reefs are endangered and thus not only the corals themselves. Coral reefs are also home to many fish, crabs, and other animal species. They belong to the most species-rich habitats that we know.
Our seas are being misused as dumps. That sounds very dramatic, but it is actually a huge problem. According to estimates by some oceanographers, unbelievable 675 tonnes of garbage per hour (!) Land in the sea worldwide. Half of it is plastic. You know that plastic does not weigh much. To get on a single ton, a whole bunch of it is already necessary. And meanwhile, huge carpets of plastic waste have formed, which continue to grow daily. One of them is estimated to be four times the size of Germany. That’s unimaginable.
Plastic rots infinitely slowly. A baby diaper can float in the sea for up to 500 years until it dissolves. Animals can confuse floating plastic parts in the water with food or, for example, become entangled in plastic cords and ultimately perish. As the plastic dissolves into the smallest parts, it inevitably ends up in the food chain at some point and eventually also over the fish on our plate.
And it’s a really big and complex challenge to avoid this garbage. Did you know that with every wash of your fleece jacket, which is usually made of polyester or acrylic, up to 2000 synthetic fibers get into the sewage and eventually into the sea? No sewage treatment plant can hold them back so far.
Too Many Too Fast
But our appetite also threatens the oceans. The consequences of worldwide fishing are, on the one hand, overfishing of the oceans and, on the other hand, damage to other sea creatures. Overfishing means that more fish of a species are caught over a longer period of time in a body of water than they are naturally regrowing or migrating. What happens then, you can imagine – many fish stocks do not recover or insufficiently. Because the fish that are left are too few to compensate for the loss of their stock with offspring. Gradually, the oceans lose whole fish species in this way.
It is not easy for science to reliably identify and prove which fish species are as critically endangered. But the species that are well studied are already half overfished. The other fish species are thought to be overfished too.
Forfeited In Vain
Another threat is that the fishing gear used – gill nets, trawls, or “longlines” staffed with thousands of fishing lines – will take them out of the sea, and they should not be caught at all. So it can happen that marine mammals get caught in gillnets and suffocate. Protected sharks and rays are caught in trawl nets. Seabirds land in longlines with baits. But also fish species fall into the net and on the hook, which should not be fished at all.
Because this happens practically incidentally, these are called completely free-captive animals simply “by-catch”. He is mostly already dead or so weakened and hurt that he can not survive. This bycatch amounts to many millions of tons worldwide every year. This is especially dramatic when hunting for shrimps – for a kilogram of shrimp, up to 20 kilograms of bycatch are produced. This bycatch will be thrown back into the sea as it is.
Is not that a huge waste? This is something we should not be allowed to afford anymore in the current state of the oceans and the threatened stocks. And as if that were not enough, some trawls drag heavy chains or weights across the ocean floor. So they kill soil organisms and disturb or destroy habitats on the seabed.
Danger threatens the seas also if too many nutrients get into the water. They are mainly from agriculture. To grow fruits and vegetables, especially in ever larger quantities and faster, they need a lot of nutrients. For this, the fields are fertilized. In heavy rain, parts of this fertilizer are washed into streams and rivers and transported into the oceans. This leads to greatly increased growth of algae.
If more algae are produced than can be eaten, they sink to the bottom of the sea at the end of their growing season, where they are decomposed by bacteria. These bacteria then consume too much oxygen from the water. So much so that it is scarce for other creatures on the seabed. Sea creatures like shells, even whole communities that can not just swim away.
Pollutants can enter the oceans via the air and over rivers. Heavy metals such as cadmium and mercury from industry, copper from water pipes, but also pesticides from agriculture. In addition, there are refuse dumped in the sea despite bans or left lying by careless tourists on the beach. This is so fast! The wind grabs the bag in which you want to put your wet swimming trunks and blows them out to sea. So a little carelessness of a turtle can cost you your life.
The oil is also a major threat to the marine environment. Again and again, it is disposed of illegally or gets into the water due to ship accidents. Particularly serious consequences for life in the sea are accidents on oil rigs, where large quantities of oil are released. It can take a while until a leak at the drilling site is closed. Until then, tons of crude oil gushes into the sea every day. A disaster for the sea creatures.