Reef development independent of coral diversity


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The development of coral reefs is independent of coral species diversity, scientists from UK and USA have found.

In a study published in a recent issue of the journal Science, Kenneth Johnson, Jeremy Jackson and Ann Budd compared changes in coral diversity and reef development within the tropical western Atlantic over the past 28 million years using new and published fossil and stratigraphic data.

Even though coral diversity on Indo-Pacific reefs is 10 times higher than on Caribbean reefs, the rates of carbonate production and reef growth are similar.

This suggests that coral diversity is unimportant to reef development, a hypothesis that the authors sought to test with their analysis.

Picture by Albert Kok (Creative Commons).

Using statistics to analyse the data, the authors found that the development of coral reefs has been independent of coral diversity over the span of geologic history studied.

As an example, the authors found that in the Middle Miocene (16.0"11.6 million years ago) through Early Pliocene (5.3 to 3.6 million years ago) intervals, coral diversity was rising but reef development was minimal, and in the Late Pliocene (3.6 to 1.8 million years ago) through Pleistocene (1.8 million"11,500 years ago), reef development dramatically increased despite mass extinction of coral species.

Their study is supported by previous studies that showed that the thick Miocene (23.0"5.3 million years ago) reef deposits in the Mediterranean were built by fewer than 10 species of corals.

The present-day Caribbean coral reef is dominated by two fast-growing species: the elkhorn (Acropora palmata) and staghorn (A. cervicornis) corals.

The authors hypothesize that the fast growth rate of these species may have allowed them to keep up with sudden rises in sea levels that have occurred repeatedly over the past 1 million years.

Picture by Albert Kok (Creative Commons).

The authors conclude that xtensive reef development in the modern ocean is controlled mainly by temperature and surface productivity.

The physical environment sets the boundary conditions for the biota and determines accumulation rates of calcium carbonate and ecological zonation, because the symbiosis functions most effectively within a limited range of nutrient and temperature conditions.

Thus, under the appropriate environmental conditions, the production and accumulation of carbonate by both low- and high-diversity coral communities can result in substantial reef development.

For more information, see the paper: Johnson, KG, JBC Jackson and AF Budd (2008) Caribbean reef development was independent of coral diversity over 28 million years. Science 319, pp. 1521"1523.