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Sustainable Development - 14 Life Below Water

Sonar operators in the navy discovered that a large number of fishes, squids and plankton swim upwards at night - this event or process was called the deep scattering layer, this layer reflects sound due to the high density of marine life in the deep sea or basically the midnight zone of oceans. Scientists discovered that this phenomenon happens every night and has been occurring for many centuries without humans ever noticing. This could be because 95% of the ocean is undiscovered even when 94% of living organisms exist in water bodies, especially oceans particularly in the midnight zone. This habitual phenomenon is called DVM which is Diel Vertical Migration and was declared as the largest migration in the world. It is done by small fishes, sea animals and/or planktons to ‘eat without being eaten’. In the day time big fishes like whales, sharks and dolphins go in search for food, they feed on  small fishes and plankton which makes it difficult for these small fishes and plankton to come up in search for their food because they may get eaten which is why such small fishes, planktons and sea animals migrate to the twilight zone at night to eat while the big sea animals are deeper in the ocean. This migration or process of eating without being eaten is changing due to factors like climate change and light pollution. Light pollution usually occurs in urban areas like coastal areas where lights are used excessively like Mumbai or NYC. This light sometimes manipulates the fishes and sea creatures into thinking that it is day time at night and they end up not migrating for food so ultimately they get eaten, or they just starve and die, whereas deep sea creatures and fishes die due to insufficient oxygen. Insufficient oxygen in midnight zones of oceans has occurred due to climate change. The upper layer of the ocean, which is where sunlight can pass through, absorbs a lot of heat since 90% of heat is absorbed by water bodies and due to this the water above the midnight zone has warmth and heat and oxygen. The midnight zone receives only red light or no light at all and the water here is dense and colder while the upper layer’s water, above the twilight zone and the twilight zone is less dense and warm, these two water layers don’t mix at all because of the different densities so the midnight zone doesn’t receive any oxygen which wasn’t the case before climate change and global warming. This leads to extinction of many species on a large scale. Many sea creatures are moving to the surface in search of oxygen, like the deep sea oarfish which used to be a rare sight. It is a silver strip-like fish which is more than 7 metres long. 50 of these fishes were found in California washed up on the shore, 3 were found in Mexico and 20 in Japan before all this, it was seen once in 2011. This fish was considered a bad omen in Japan because an Earthquake occurred after seeing it on shore. Scientists discovered that water in those zones would increase in temperature by 1 degree Celsius over the next 84 years and DVM would occur 4-11 times faster than now. Recently countries like the USA and India may start Deep Sea Mining which is bad for all living organisms in water bodies. A sea creature called as scaly foot snail was discovered and it’s shell is made up of iron this is another reason why people are leaning towards doing deep sea mining, overfishing, polluting-nutrient pollution and light pollution instead of restoring our coastal and marine ecosystems, reducing all types of pollution which are inter-related to the slow depletion of marine life like acid rain which is caused by air pollution and leads to water pollution. Sustainable fishing, stopping illegal fishing, not overfishing as well as regulating fishing in the right way should be practiced. Most importantly scientific knowledge, research and technology for ocean health to discover more solutions, causes and efforts towards it to prevent facing consequences of human’s mistakes and wrong decisions should be done for the betterment of Life Below Water.