Minerals – ores like iron, aluminium and copper. Catalysts and harders – sand gravel cement, clay salt sulphur and diamonds – all non-renewable but mostly available for re-use. Distribution is uneven.
The US citizin is responsible for the use of 7.25 kg of lead, 3.55 tons of stone, sand and gravel, 227 kg of cement, 91 kg of clay, and 91 kg of salt. Luckily, not many nations consume as much. The rate of consumption of more minerals since 1950 then in the previous recoded history of the world. Due to technological advances, some believe there will be no major shortages in mineral supply, e.g. atomic power will provide the energy to extract minerals from presently unviable sources such as the sea. This point of view has been attacked. Unless technology develop to utilize the following abundant supplies: iron, aluminium, magnesium, silicates, hydrogen, oxygen, nitrogen, sunlight, to provide all our mineral needs.
71% of Earth’s surface. The salinity of the sea has been stable for the last 2000 million years. Organisms in the sea play an important role in removing minerals from the liquid state to solid state. Mineral resources: Those dissolved in the water, thos deposited in the sea bed. The utility of dissolved elements is proportional to the concentration in the water and the relative cost of mining the mineral on terrestrial sources. NaCl, Mg and bromine are at present the only minerals in sea water that exceed 1 part per million. Sediments and sedimentary rocks on the continental shelves are sources of certain materials such as petroleum and natural gas. Manganese nodules in sediment. They occur as a layer with a mean depth of 4000 – 5000 m. There are reports of large deposits of sulphide ores of zinc, copper and iron on the sea floor. A small proportion of the worlds wealth by mining comes from the sea but this is likely to increase.
Biological resources: There are limiting factors on the biological productivity of the sea. The euphotic zone in which photosynthesis can occur is only about 60mm??cm?? deep, primary producers are scattered very thinly otherwise they would shade each other, therefore are self limiting. CO2 also scarse in sea water and depends on mixingdynamics. Plankton are generally unable to control their regional movements and considerable patchiness in their presence and productivity. Food shains generally simple and short lived. As animals grow, their diets change so that food chains are continually forming and disappearing. Detritus and bacteria are important food sources in shallow water and probably have a important role in deeper water since there are 10 grams of dead and 100g of dissolved carbon for every gram of living carbon in the water column, and the dead organic carbon can only be made available again via bacterial activity. Open oceans are the least productive and can be considered biological desserts because of the small size of autotrophic zone in relation to the heterotrphic zome in which the cycling of nutrients takes place. The distribution of productivity suggests that nutrients may be a limiting factor. Coastal zones are productive because of sources of nutrients. There are also upwelling zones (West coast etc.). Tidal flats and estuaries are among the most productive ecosystems in the world. The standing crop is always relatively low because of the high turnover (i.e. short life spans). It is not viable to harvest phytoplankton or zooplanton (taste, processing, low density, silicated shells). Third trophic level yields many more desirable species e.g. flounders, haddock, cod, herring, sardines and certain whales and further along the food chain, tuna, salmon, swordfish, seals and certain whales. There are also detritus feeders I.e. sole and crustacea. (up to date harvesting estimates and SA example?). Asian countries most consume sea food. The extension fo fisheries could involve : the exploitation of untapped spacies, better capture techniques, extending operation into unexploited areas. The fertilisation of low nutrient areas may in the future be employed to increase productivity (lookup?). Krill may become a viable food source as most whale populations have been decimated.
Oysters and mussels in Hong Kong and Philippines and Japan, are vulnerable to contamination. True aquaculture involves genetic manipulation and the chosen species by keeping them captive throughout their breeding cycle. This is very difficult and requires unpolluted sea water and a suitable coastal site and waste heat, needs much skill.
Over exploitation of biological resources.
The population must not be overcropped to the point that its reproduction no longer provides sufficient individuals to constitute a resource. Requires the rational management of the resource. Serious declines have occurred in the past: Asian and Californian sardine, North West pacific salmon, Yellow fin tuna are presently taking strain. Interim regulatory measures are sometimes applied to such species, regulating catch and net size, but these measures are difficult to enforce and therefore certain species have been overfished. It may not be possible for an overfished species to regain its place in energy pathways of the ecosystem. Sea mammals have been exploited: Japan and porpoises. Certain seals. Whaling: most prolific example of over-exploitation. Japan and the USSR (former) still killing whales.
Pullution: Sea had had some deliberate and accidental spills and continues to be used as a garbage bin: radio isotopes and industrialised effluents.