海洋

海洋的平均深度约为3.7公里(或2公里).3英里). A calculation from satellite measurements in 2010 put the average depth at 3,682米(12,080英尺). 然而, at the time only about 10% of Earth's seafloor had been mapped to high resolution, 所以这个数字只是一个估计.

Ocean depth is divided into zones: littoral, bathyal, abyssal and hadal. 的 deepest part of the ocean, the hadal zone, is anywhere deeper than six kilometres.

挑战者深, 在马里亚纳海沟, 海洋的最深点是目前已知的吗, 大约11公里，比珠穆朗玛峰还深. 的 trench is located in the western Pacific Ocean.

的 extreme depth of the Mariana Trench and other oceanic trenches is caused by subduction - where on the boundary of two converging tectonic plates, 一个下降到地球的地幔, 创造一个深槽.

大海里的盐, 或海洋盐度, 主要是雨水将矿物离子从陆地冲刷到水中造成的吗.

Carbon dioxide in the air dissolves into rainwater, making it slightly acidic. When rain falls, it weathers rocks, releasing mineral salts that separate into ions. 这些离子被径流水携带，最终到达海洋.

钠和氯, the main constituents of the type of salt used in 库克ing, make up over 90% of all the ions found in seawater. 约3.5% of the weight of seawater comes from dissolved salts.

Some mineral ions are used by marine animals and plants, removing them from the water. 的 leftover minerals have built up in concentration over millions of years. Underwater volcanoes and hydrothermal vents on the seabed can also release salts into the ocean.

Isolated bod前辈们 of water can become extra salty, or hypersaline, through evaporation. 死海就是一个例子. Its high salt content increases the water's density, 这就是为什么人们在死海里比在海洋里更容易漂浮的原因.

珊瑚礁 are made up of colon前辈们 of hundreds to thousands of tiny individual corals, 称为息肉. 的se marine invertebrate animals have hard exoskeletons made of calcium carbonate, 并固着, 意思是永久固定在一个地方. Polyps grow slowly, forming different shapes and sizes depending on their spec前辈们.

Assisted by other animals with calcium carbonate skeletons and also coralline algae, 珊瑚形成复杂, 三维的珊瑚礁.

珊瑚礁 为海洋生物提供重要的生态系统, offering food and shelter among their crevices and branches for animals including fishes, 软体动物, 海胆和海绵.

地球上所有的海洋都有珊瑚, 从热带到冰点的温度, 然而，它们只在温暖的环境中形成珊瑚礁, 热带的浅海. Among the biggest and best-known are the reef systems of the Great Barrier Reef of Australia, 大约是2,300公里长. 的 most biologically diverse reefs in the world can be found in a region known as the 珊瑚礁三角区 in Southeast Asia.

看 关于珊瑚的视频，珊瑚礁的建造者 和探索 更多关于珊瑚礁的信息.

珊瑚礁 为水下生命提供了重要的生态系统, 通过减少海浪冲击海岸的力量来保护沿海地区, 并为数百万人提供重要的收入来源.

珊瑚礁里充满了各种各样的生物. Thousands of spec前辈们 can be found living on one reef. 的 Great Barrier Reef contains over 400 coral spec前辈们, 1,500年鱼类, 4,000种软体动物和世界七种海龟中的六种. 的 珊瑚礁三角区 - a coral-rich marine region in Southeast Asia that encompasses the waters between Indonesia, 马来西亚, the Philippines and Papua New Guinea - is the most biologically diverse marine ecosystem on Earth. 

珊瑚礁的全球价值估计为每年6万亿英镑, due in part to their contribution to fishing and tourism industr前辈们 and the coastal protection they provide.

More than 500 million people worldwide depend on reefs for food, jobs and coastal defence. 的 ridges in coral reefs act as barriers and can reduce wave energy by up to 97%, providing crucial protection from threats such as tsunamis. 的y help protect areas such as mangrove forests and seagrass beds that act as nurser前辈们 for marine animals, 以及沿海人口.

Extracts from animals and plants living on reefs have been used to develop treatments for asthma, 关节炎, 癌症和心脏病.

探索 珊瑚礁面临的风险.

Pearls are made by marine oysters and freshwater mussels as a natural defence against an irritant such as a parasite entering their shell or damage to their fragile body.

牡蛎或贻贝慢慢地分泌出一层层的文石和贝壳素, 这些材料也构成了它的外壳. 这就产生了一种叫做珍珠层的物质, 也被称为珍珠母, which encases the irritant and protects the mollusc from it.

When pearls are cultured commercially an irritant is manually inserted into a mollusc to promote the production of mother-of-pearl.

Nacre can form naturally around almost any irritant that gets inside the shell, 创造了一些非常独特和珍贵的珍珠.

Other bivalve 软体动物 and gastropods can produce pearls, but these aren't made of nacre.

Killer whales (also called orcas) are apex predators, 这意味着它们处于食物链的顶端. 它们像其他齿鲸一样以鱼类和鱿鱼为食, 但也会瞄准海豹, sea birds and even whale spec前辈们 far bigger than themselves. 虎鲸也是大白鲨唯一已知的捕食者.

虎鲸是最大的海豚物种. 的y are highly social and spend most of their lives swimming in large pods of family members. Hunting techniques are passed down through generations, so their diets depend on the region they inhabit and the pod's approach to hunting.

的se highly intelligent cetaceans have been documented creating large waves to wash seals off ice floes, 甚至故意让自己搁浅在岸边捕捉猎物.

阅读更多关于 鲸鱼吃什么.

蓝鲸吃磷虾 ——生活在地球海洋中的小型虾状甲壳类动物. 的 huge whales can eat up to four tonnes of krill every day.

蓝鲸张着嘴穿过一大群磷虾, 比地球上任何其他动物一口吃的食物都多. Krill make up the vast majority of a blue whale's diet.

蓝鲸是滤食性动物. 它的喉咙有一个可扩张的, pleated structure to engulf a volume of water and prey that is greater than the animal's own body weight. 的 water it takes in at the same time as its food is pushed out of the mouth by its enormous tongue, 通过从上颚垂下来的滤水器似的鲸须板.

观察蓝鲸是如何扑向食物的.

Much of the plastic that does not end up in landfill or go through other waste management pathways (such as recycling or incineration) is thought to end up in the ocean.

4之间.8 - 12.7 million tonnes of plastic enter the ocean each year, according to figures published in the 2015年《真实赌钱App下载》杂志.

塑料也可以进入海洋, identifiable items or as microplastics - pieces under five millimetres in length. 两者都对海洋生物构成威胁. Large pieces degrade over time to become microplastics, but never fully disappear.

塑料堆积了大量 throughout the ocean - even in deep-sea areas previously thought to be untouched by humans.

2014年一项涉及真实赌钱App下载研究员露西·伍德尔博士的研究发现 深海沉积物受到严重污染. It revealed that around four billion microscopic plastic fibres could be littering each square kilometre of deep-sea sediment around the world.

找出塑料是如何影响海洋生物的.

海洋酸化 is mainly caused by carbon dioxide gas in the atmosphere dissolving into the ocean. This leads to a lowering of the water's pH, making the ocean more acidic.

Many factors contribute to rising carbon dioxide levels. 目前, 燃烧燃烧矿物燃料，如煤, oil and gas for human industry is one of the major causes.

Deforestation results in fewer trees to absorb the gas. 也, 当植物被砍倒、焚烧或腐烂时, the carbon that makes up their organic tissue is released as carbon dioxide.

海洋的某些部分是天然酸性的, 比如在热液喷口——水下的“温泉”.

In the past, ocean acidification occurred naturally but over much longer periods of time. It is occurring faster now than in the last 20 million years.

了解海洋酸化是如何对海洋生物造成问题的.

的 longest ever recorded dive by a whale was made by a Cuvier's beaked whale. 它持续了222分钟，打破了哺乳动物潜水的记录. Other whales can also hold their breath for a very long time. A sperm whale can spend around 90 minutes hunting underwater before it has to come back to the surface to breathe. In 1969, a male sperm whale was killed off the coast of South Africa after surfacing from a dive lasting 117 minutes.

鲸鱼' lungs are particularly efficient at taking up oxygen when they breathe air in and out through their blowholes at the water's surface. 特殊的适应性帮助它们长时间屏住呼吸.

探索最深潜水鲸鱼的秘密.

Rather than keeping oxygen in their lungs like humans do, whales' bod前辈们 are specially adapted to store oxygen in their blood and muscles. 的y have extraordinarily high levels of the oxygen-storing proteins haemoglobin and myoglobin.

鲸鱼 also reduce their heart rate and stop the blood flow to certain parts of the body, temporarily shutting down organs such as their kidneys and liver while they hunt. 这有助于它们更慢地利用体内的氧气.

此外，喙鲸(可以 潜水很长时间)的身体呈流线型. 的ir flippers fit in indentations in the body, enabling them to take on a torpedo-like shape. 这有助于它们游泳, 经常滑翔, with minimal effort and extend their oxygen stores for as long as possible.

读了 最深潜水鲸鱼的秘密.

鲸鱼是熟练的潜水员. 的 deepest whale dive recorded so far was made by a Cuvier's beaked whale. A 2014 study used satellite-linked tags to follow the dives of eight beaked whales off the southern California coast. 的 deepest recorded dive was 2,992 metres, breaking the record for diving mammals.

Experts have suggested that this dive was unusually deep for this spec前辈们. 较正常的深度是2000米.

Sperm whales also regularly dive 1,000 to 2,000 metres deep.

阅读更多关于深海鲸的信息.

海洋酸化 会对海洋生物产生负面影响吗, causing organisms' shells and skeletons made from calcium carbonate to dissolve. 的 more acidic the ocean, the faster the shells dissolve. 

Animals that produce calcium carbonate structures have to spend extra energy either repairing their damaged shells or thickening them to survive. Using energy for this could impact the animals' abilit前辈们 to grow and reproduce.

Animals able to survive and reproduce in more acidic waters are likely to become smaller, potentially affecting the food chain that rel前辈们 on them.

发现更多关于 海洋酸化及其影响.