Maritime Knowledge (or) Knowledge of Tamil on Ocean

MARITIME KNOWLEDGE (OR) KNOWLEDGE OF TAMIL ON OCEAN

About 70% of the earth's surface is covered by ocean. The ocean has been known as Sea, Aazhi, Pazhi, Olam, Kayam, Varithi, Nerineer, Valayam, Pirambu, Thozham, Thirai since the Sangam period.

Apart from fishing in the sea, there are many other phenomena such as trade, exploration of mineral resources, discovery of oil resources, climatic changes, conch, pearl, agar, clams and various marine lives, medicinal plants in the sea, estuary areas where rivers merge with the sea. The nature of the sea was, it had full of bio-diversity. The Sangam people had an understanding of them.

Definition of Sea (Ocean)

Sea refers to a large body of salt water. The salinity of sea water varies widely. Less at the surface and near the mouths of large rivers and more in the depths of the ocean.

1. Substances Dissolved in Sea Water

The most dissolved solid in sea water is Sodium Chloride. Magnesium, Calcium, Potassium, Salts of mercury and many other elements are dissolved in the water.

1. Salinity

Ocean salinity is usually measured in parts per thousand. The open ocean has about 35 grams of solids per litre. In general, evaporation and ice formation increase salinity. At the same time, rainfall, melting of sea ice and run off from land reduce salinity.

2. Thermal Condition

Ocean temperature depends on the amount of solar radiation falling on its surface. Surface layers typically have a temperature of 30°C while deep sea water ranges from −2°C to 5°C in all regions. Sea water with a salinity of 35% is at about −1.8°C.

3. pH Value

Sea water is slightly alkaline with an average pH of 8.2 over the past 300 million years. Recent climate change has increased the amount of carbon-dioxide in the atmosphere. 30-40% of the added CO₂ is absorbed by the oceans, forming carbonic acid. This is called ocean acidification. pH is expected to reach 7.7 by 2100.

4. Oxygen Concentration

The amount of oxygen found in sea water depends on the plants that grow in it. These are mainly algae and phytoplankton and certain marine plants engage in photosynthesis and produce oxygen. It dissolves in sea water and is used by marine animals. At night, photosynthesis stops and dissolved oxygen levels decrease.

5. Light

Sunlight falling on ocean is reflected on the surface. Red light is absorbed at depths of a few meters. Yellow and green light reach greater depths. Blue and violet light penetrate upto 1000 metres. Beyond a depth of about 200 meters, enough light is not found for photosynthesis and plant growth.

2. Life at Sea

Marine life is the life of a variety of organisms that use the oceans as their habitat.

Algae and Plants

The primary producers of the ocean are plants and micro- organisms in the plankton. Half of the world's oxygen is produced by plankton. Algae also play an important role in this. Light can only penetrate 200 meters. Therefore, it is the only part of the ocean where plants can grow.

Animals and other Marine Lives

More animals live in the sea than on land. Some vertebrates such as sea birds, seals and sea turtles return to land to reproduce. But, fish, cetaceans and sea snakes have a completely aquatic lifestyle.

For Human Food

The oceans provide substantial food for humans, especially fish. Then they used sea water to extract salt for food. So sea water has become an important part of life today.

Travel

Pre-Historic Boats

It is believed that the first pre-historic boats might have been dug-out boats developed independently by various Neo-lithic peoples. In ancient history, various ships were used for coastal fishing and travel.

There are fossils and traces left in the rhinoceros skeleton that suggest early humans crossed the sea and colonized the Philippine island of Luzon between 777,000 and 631,000 years.

The sea crossing occurred about 53,000 to 65,000 years ago. They might have used large bamboo boats. In the history of whaling, the oldest method by humans around 6000 BC was to simply drive them ashore by placing several small boats between the whales and the open sea and scaring them with noise, small non-lethal weapons, etc.,

Travel on Ship

Sangam literature says that humans followed sea turtles to travel by sea. Sailing ships were used for fishing in the seas and for carrying mail packets abroad. When steam ships came into use in place of sailing ships, people started to travel. At the beginning of the 20th Century, they sailed larger and faster ships.

Silappathikaram mentions that Sangam Tamils used large ships for long distance travels. Literature also says that Sangam Tamils had knowledge of ocean currents. To help the ships to know the direction, lighthouse was made. Many references to this have been mentioned in the Sangam literatures of Silappathikaram, Pattinappalai and Agananooru.

Trade

Trades through sea routes have existed for thousands of years. The Ptolemic dynasty developed trade with India. Arabs, Phoenicians, Israelites and Indians traded in luxury goods like gold and precious stones.

Efficient Production

The ocean provides enormous potential for transporting energy through sea waves. They can be used to generate electricity.

Extractive Industries

There are huge mineral reserves in the seabed. They can be exploited by excavations. It has more advantages than land-based mining. Undersea rocks contain large deposits of petroleum such as oil and natural gas.

3. Environmental Issues

1. Oceans are polluted as a result of human activities. (Marine litter, plastic pollution, microplastics, nutrient pollution, toxins, etc.).

2. Over exploitation (fishing, habitat loss, invasive species)

3. Climate changes in the ocean (increasing sea temperature, decreasing pH value, ice melting, decreasing oxygen level).