The Sea is our oldest mother. To put in other way, if the earth is the mother, as we are used to say now days, sea is the womb. But to place the ‘life’ phenomenon in a proper context, it is better to recognise sea as is the primeval mother of all species.
It was in the sea that the primordial life was first originated. Then through the long walk of evolution many different species evolved. Those species had their habitation on land or into the sea according to the dictation of evolution.  A good position may be, to recognise the role of both the sea and land in our life is to bestow motherhood like this, that the sea is the mother with womb who carried and the land is the mother with lap who rears.
For a long time it was believed that nothing can pollute the sea.  Seas are so vast that any amount of pollutant will be diluted to a harmless trace concentration. And therefore will have no adverse affect on marine life and life on land as well. 

Till day, many countries dispose their nuclear and chemical wastes into the sea. They follow the technical principle of “dilute and disperse”. In addition, oil spilling into the sea happened due to ship accident for many times, since the transport of crude oil by sea going vessels started. Oil spilling also happens due to malfunctioning of the oil silos stationed in the sea. The leakage from British Petroleum silo in the Gulf of Mexico is one major oil spilling event in the recent past. Apart from this, accident in offshore oil exploration and mining sometimes causes oil spill. 

Undoubtedly, oil spill is a serious threat to marine environment. It threatens the aquatic life of flora and fauna and of birds and fishes. Due to a dispersed big layer of oil over the sea surface, oxygen from air can’t mix with sea water in the required amount. So, the dissolved oxygen level falls below the level required for aquatic life to survive. Moreover, birds, fishes and many small aquatic animals get stick into the spilled oil. Their bodies are cloaked with slimy crude oil. Most importantly, the food chain within the sea is hampered. 

But there is more striking situation of marine pollution where we are engaged personally beyond our common sense. Anyone wouldn’t believe at first approach that we pollute seas from here our house and staying in far away cities. It apparently sounds absurd. But this is scientifically true. Whatever you dispose off   ultimately goes to the sea. A simple potato chip packet, cork of a cold drink pet bottle, whatever is not properly disposed off, will go to the sea with the runoff water of rain. The pathway of the urban litter to reach the sea is through sewerage line to the nearest river, being carried by rain water and then from river to the sea.

Moreover, It might also  sound unbelievable, but it is   true that more oil pollution of the sea is made by the small amount of oil that spills from our vehicles while at  home garage or on  the street than large scale oil spilling due oil tanker accident in the sea itself.  The amount of oil spill that happens from thousands of vehicles in the city is significant in aggregate and reaches the sea through rain water following rivers and other channels.

There is no perfect technology so far to cleanse the sea of spilled oil. Scientists are trying to do it through biotechnological methods. It was reported years before, that scientists have developed a new strain of microorganism that will eat up the spilled oil and will make sea water clean. Also there are other scientific approaches on trial to ensure spilled oil free sea.

The most horrific situation is with transport and accumulation of different plastics and polythene into the sea. The tragedy with this deceiving pollutant happens with Albatross. Albatross, the most known sea bird is badly affected by plastic. They mistake these plastics for their food. While they swallow plastic they   get sick and finally die. This perilous situation of albatross is well reported in the world media. But it can certainly be   assumed that the same situation might hold true to for other marine species too.

The other dangerous feature of this marine pollution with solid plastics is that these are being accumulated back within human body through food cycle. It is the rule of food cycle that, poison in bigger amount will accumulate in the higher species that is at the top of the food cycle.

Plastic wastes that go to the sea are converted into plastic dust by the whirlpool of water at different parts of the sea.  These plastic dusts are eaten up by sea fish and aquatic animals. Finally, human beings eat this plastic dust by consuming sea fish. Our metabolic system can’t process plastics and these plastics are definitely carcinogenic. Sadly, we are the victims of our daily careless litter and no doubt, very badly. 

For many years, since human settlement had begun, people have been continuously cutting trees and destroying forest.  Million years ago the whole earth was covered with forest.  People cleaned it up for habitation, for agriculture and for industrialisation.

Now, the most vital question that knocks us to be answered is that after a massive deforestation throughout the course of development of civilisation, how the composition of the atmosphere still maintains approximately the same and provides us with enough oxygen to survive?

The answer is simple. It is actually the ocean that made us to survive with oxygen and helped preserve the composition of the atmosphere same. The photosynthesis that happens in the sea plants, especially in the phytoplankton is enough to give necessary oxygen. Sea provides 55 to 85 percent of necessary oxygen for our survival. It doesn’t justify deforestation though. Because destroying forests have other environmental impacts too. 

So, oceans play the most important role in our life. Seas are full of different resources. They can feed the whole earth population for next thousand years.

United Nations has recognised Jun 8 as the World Ocean Day.  The Action focus for 2018 of UN is ‘Preventing Plastic pollution and encouraging solutions for a healthy ocean’. UN recognises that plastic pollution is causing tremendous harm to our marine resources. 

According to the UN,

• 80 percent of all pollution in the ocean comes from people on land.
• 8 million tones of plastic per year end up in the ocean, wreaking havoc on wildlife, fisheries and tourism.
• Plastic pollution costs the lives of 1 million seabirds and 100,000 marine mammals per year.
• Fish eat plastic, and we eat the fish.
• Plastic causes $8 billion in damage to marine ecosystems each year.

As final remarks, we have to be careful in our consumption and disposal. It has to be environmentally friendly causing less pollution. Now, it is well accepted scientifically that we can pollute oceans by just staying in our homes or community, not even going by sea. We have to keep in mind that 80 percent of all pollution in the ocean comes from people on land. So, what we behave here affects the sea far away.

The ocean is our oldest mother and the last resort for oxygen and food. Let’s keep it clean even while staying at home. Scientists recommend for less use plastics in our daily life and to recycle plastics. UN also recommends the same. We have to uphold the fact that ‘Everything goes to the sea’ and have to behave accordingly. The earth is deposit to us by our ancestors for our future generation.

Zahirul Hoque Mozumder is an associate professor of Electrical and Electronic Engineering at the University of Dhaka.