Unknown species

The total diversity of life in the sea remains remarkably poorly known. Long regarded as being the most species diverse marine ecosystem less than 10% of the organisms found on coral reefs have been described by scientists. However not all experts agree on these species' identification and definition and there is no central record, even of the species which have been described. Using a number of broad assumptions therefore, one recent attempt has suggested that there may be 93,000 described coral reef species. The global total could perhaps be closer to 1 million. Others have estimated that there may be over 3 million reef species.

Perhaps the greatest problem hindering a more detailed assessment of coral reef biodiversity is the lack of basic taxonomic research and inventory, combined with the lack of sufficiently qualified taxonomists to undertake the work. Defining and describing species is a complex task, and detailed observation and description of external morphological characteristics of animals and plants have traditionally been key tools. A number of recent studies, however, have suggested that many of these morphologically similar 'species' may in fact be species complexes, groups of sibling species, each highly distinct in genetic terms. If such examples prove to be commonplace, the final analysis of species diversity may lead to massive increases in the total species numbers.

Another major problem in assessing marine species diversity accurately is serious undersampling of the huge area and volume available to biota. In fact, recent estimates suggest that deep-sea diversity is much higher than in any other marine habitat, perhaps even rivalling tropical rain forests in total species numbers though there is not universal agreement on this issue. What is certain however is that new species, even quite large animals such as squid, are being discovered regularly.