Observed from space, our planet’s surface appears to be dominated by the color blue. This blue color occurs because of the presence of the oceans and seas of the world. These features cover approximately 71% or 361 million square kilometers (139 million square miles) of Earth’s surface with a volume of about 1370 million cubic kilometers (329 million cubic miles). The average depth of these bodies of seawater is about 3.8 kilometers (2.4 miles). Maximum depths can exceed 10 kilometers (6.2 miles) in areas known as ocean trenches. The oceans contain 97% of our planet's available water. The ocean is also home to many forms of life uniquely adapted to survive in this habitat. Humans have degraded the oceans and their life through pollution, overfishing, carbon dioxide acidification and resource exploitation.
A sea is commonly defined to be an extended body of saline water associated with one of the worlds five oceans (Atlantic, Indian, Pacific, Arctic, and Southern oceans). Some seas...
Marine biodiversityLast Updated on 2014-12-15 19:53:24Biodiversity is now commonly defined as the variety of life in genes, species and habitats. According to the definition of the Convention on Biological Diversity, biodiversity is the variability among living organisms from all sources, including inter alia, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part; this includes diversity within species, between species and of ecosystems.
The three domains of life, bacteria, archaea and eukarya are present in the marine environment. In addition there are viruses. About 230,000 species of marine plants and animals have been scientifically described and a few thousand bacteria and archaea. This known biodiversity only represents a small fraction of the number of species existing, except for the macrophytes and seagrasses which are living in coastal environments and, in general, for the pelagic... More »
Fisheries and aquacultureLast Updated on 2014-12-07 21:08:51
In 2002 the global production from fishing and aquaculture combined reached about 133 million tonnes. The global yield from capture fisheries is stagnating, but aquaculture has been expanding.
The quantities of fish captured remained stable at about 93 million tonnes per year between 1999 and 2002. China and Peru are leading the top ten of countries with the largest catches. The same countries have remained in the top ten for over a decade.
Oceans and seas provide 90% of the world's fishery catches. During the past decade marine catches brought to land increased slightly compared to the preceding decade. It should be noted that the quantity of marine fish caught and discarded fell by several million tonnes in the same time period. Trends vary greatly across different regions and for different species. The species yielding the largest harvest is the Peruvian... More »
OverfishingLast Updated on 2014-12-07 17:22:32Overfishing is the human act of extracting aquatic (that is, marine and freshwater) fauna from natural water bodies at a rate greater than the reproductive and recruitment functions can replace that extraction. While there is some evidence that localized overfishing may have occurred in prehistoric eras, the bulk of overfishing has taken place in the last 150 years as the human population has expanded greatly and fishing technologies have enabled harvesting of many species at rates not imagined in earlier times. For over a century man's role in the depletion of certain regional fisheries has been noted. A functional definition of overfishing is sometimes given as the reduction in catch per unit effort by fishermen. Typically the concept of overfishing is linked to an individual aquatic species, and this issue is most often discussed within a specific marine or lacustrine province... More »
Mangrove ecologyLast Updated on 2014-10-19 17:31:46
Mangrove ecology is the study of biotic interactions within mangrove swamp ecosystems. These habitats are significant not only for the biodiversity they represent, but also for the protection of coastal erosion, and for the provision of protected nursery areas for marine fauna.
Mangroves worldwide cover an approximate area of 240 000 square kilometers of sheltered coastlines in the tropics and subtropics.
Mangroves stabilize coastal intertidal soils pereventing coastal erosion
Four of the most common ecotypes include fringe, riverine, basin, and scrub forests.
Mangroves are restricted to the intertidal zone.
Mangroves in general have a great capacity to recover from major natural disturbances.
Mangroves maintain water quality by trapping sediments and taking up excess... More »
ClimateLast Updated on 2014-10-01 10:48:54
Climate is the typical pattern of conditions of the earth’s atmosphere over a given region, as defined by factors such as temperature, air pressure. humidity, precipitation, sunlight, cloudiness, and winds. The World Meteorological Organization defines climate as "the statistical description in terms of the mean and variability of relevant quantities over a period of time," where an appropriate period is typically at least thirty years. Climate can be assessed at different, overlapping geographic regions. For example, Earth is thought to have a climate that is distinct from that of other planets, while different regions of Earth are also thought to have distinct climate types. Climate is often described as the "average" conditions; however, since daily and seasonal variability (including extremes) are critical determinants, using the term... More »
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