Ecosystem Diversity

Life in the oceans is very unevenly distributed some parts are astonishingly productive (e.g. slat marshes) and diverse (e.g. coral reefs) while others are virtually barren (e.g. oligotrophic expanses of open ocean). With the present configuration of land masses, a major part (37%) of the world ocean is within the tropics, and about 75% lies between the 45� latitudes. The largest continental shelf areas (40%) are in high northern latitudes and about 30% of the total shelf area is in the tropics.

 

Although knowledge of the functioning of the marine biosphere has increased enormously in the past few decades, overall it remains far less well known and understood than the terrestrial part of the globe. The main reason for this is, quite simply, that much of it is inaccessible to humans. Study of any part below the top few meters requires specialised equipment and is expensive and time consuming. Knowledge of most of the sea is thus based largely on a range of remote sensing and sampling. As these techniques become more sophisticated, so our under- standing of marine ecosystems, particularly those away from the coastal zone, is under- going constant revision.

 

This is especially the case for deep sea ecosystems. The long held idea that the deep sea is uniformly featureless has been dispelled by many discoveries of sometimes bizarre, and highly diverse, deep-sea communities such as those associated with hydrothermal vents and other hydrocarbon, wood, seamounts and, most recently, whale skeletons. Even flat muddy bottoms are now known to have sources of local physical heterogeneity, such as biogenic structures, manganese nodules, and patches of organic matter. Such heterogeneity permits niche diversification and high species richness.