(a) Give an account of marine resources and their economic significance. How has marine pollution affected such resources? (20…

(a) Marine resources, their economic significance and the effect of pollution

Marine resources are the living and non-living wealth of the oceans. India has a coastline of about 11,000 km and an Exclusive Economic Zone of about 2 million sq km.

(i) Biotic resources. Fish, shrimp, seaweed, pearls, corals and plankton give food protein, livelihoods for fisherfolk, exports, and raw material for feed and medicines.

(ii) Mineral and energy resources. Offshore petroleum and gas (Mumbai High, the Krishna-Godavari basin), polymetallic nodules in the Central Indian Ocean Basin, placer deposits of ilmenite and monazite on beaches, marine salt and sand. Tidal, wave, ocean-thermal and offshore wind energy add to this.

(iii) Economic significance. They support food security, trade, energy security and ports, tourism, and the blue economy, including aquaculture, seaweed farming and deep-sea mining.

Effect of marine pollution.

(i) Oil. Spills, as in the MSC Chitra collision off Mumbai in 2010 and at Ennore in 2017, smother shellfish, coat birds and close fisheries and beaches.

(ii) Plastics and microplastics. They entangle animals, enter food chains, and affect the catch. The X-Press Pearl disaster in 2021 spread plastic pellets on Sri Lanka's coast.

(iii) Nutrients. Fertiliser and sewage runoff cause algal blooms, oxygen-poor dead zones and fish kills, as in the Gulf of Mexico.

(iv) Toxic metals and chemicals. Mercury, lead and pesticides bioaccumulate and make seafood unsafe, as in the Minamata disease in Japan.

(v) Warming and acidification. They bleach coral reefs and weaken shell-forming species.

Pollution thus cuts yields, raises clean-up costs, reduces exports and tourism, and turns a productive commons into a degraded resource.

(b) Organic and mineral horizons

A soil profile is a vertical section through the horizons. The O horizon is organic; A, E, B, C and R are mineral.

(i) Origin. The organic horizon is formed from surface litter and humus, by decomposition of plants and animals. Mineral horizons come from weathered rock and its parent material.

(ii) Composition. The O horizon is mostly organic matter, dark, loose and with few mineral particles. Mineral horizons are mostly mineral particles, with humus decreasing downward.

(iii) Biological activity. The O horizon has the most organisms, roots and microbes. Activity falls with depth through A to C.

(iv) Processes. The A horizon is the mineral topsoil mixed with humus and is the main zone of roots. The E horizon loses clay, iron and bases by eluviation, so it is pale. The B horizon gains them by illuviation, so it is denser, blocky and often reddish or yellowish. C is partly weathered parent material, and R is bedrock.

(v) Occurrence. The O horizon is thick in forest and peat soils, but thin or absent in cultivated and arid soils. Mineral horizons are always present.

(c) Temperature inversion and local weather

Inversion is the reversal of the normal fall of temperature with height, so that a layer of warm air lies over cold air near the surface. The cold air is dense and stable, so it does not rise.

(i) Radiation inversion. On long, clear, calm winter nights the ground loses heat by long-wave radiation and cools the air above it. It is strongest in valleys and basins, where cold air drains down, as in Kashmir and Punjab.

(ii) Subsidence inversion. Sinking air in an anticyclone warms by compression and forms a warm lid, as over Los Angeles.

(iii) Advection and frontal inversion. Warm air passing over a cold surface or over a cold air mass at a front gives inversion, with fog on cold coasts.

Significance. The inversion acts as a lid. It causes fog, frost damage to crops such as mustard and potato, and poor visibility that delays flights and trains. It traps pollutants, so smog forms, as in Delhi in November from vehicle and stubble smoke, and in Los Angeles. It also stops convection, so there is no rain, and in hill valleys it makes the valley floor colder than the slopes, which is why orchards are placed on the slopes.