Currently, between one-third and two-thirds of marine species may be undescribed, and previous estimates of there being well over one million marine species appear highly unlikely. More species than ever before are being described annually by an increasing number of authors. If the current trend continues, most species will be discovered this century.

Botanical and zoological collections may serve as archives for historical ecological research on the effects of global change and human impact on coral reef biota. Museum collections may harbour old specimens of reef‐dwelling species that have become locally extinct. Such collections also help to determine whether early records of invasive species can be obtained from times when they were not yet recognized as such. A case study (2006) involving Saba Bank, Caribbean Netherlands (former Netherlands Antilles), suggests that the coral reef fauna here may have become impoverished when compared with data obtained during an earlier expedition in 1972. However, the 1972 sampling may have been incomplete, as it was performed by professional divers who were not trained taxonomists, whereas the collecting in 2006 was done by experienced marine biologists who knew the taxa they were sampling. As Saba Bank has been under stress due to the anchoring of large vessels, and invasive species have been a potential threat as well, future studies are needed to obtain more insights into the changing reef biota of Saba Bank. Using this Saba Bank example, we want to address the importance of natural history collections as reservoirs of valuable data relevant to coral reef biodiversity studies in a time of global change. As such, these collections are still underexplored and underexploited.

The Banc d'Arguin, Mauritania, is an area of over 10000 km 2 of shallow water and tidal flats between the Sahara and the upwelling system off the Mauritanian coast . The results of the Dutch-Mauritanian project `Banc d'Arguin 1988' as well as the relevant literature are reviewed in order to develop a preliminary conceptual model of the functioning of this ecosystem . Hydrographically the Banc d'Arguin can be characterized as a large-scale negative estuary with higher salinities near the shore . It is concluded that ultimately the Banc d'Arguin ecosystem is fueled by nutrients and organic matter derived from the upwelling area . The inner part of the Banc d'Arguin system is dominated by a detritus-based benthic foodweb in which seagrasses are the principal primary producers . Little of the seagrass production seems to be exported to other parts of the system or other areas . Zooplankton and zoobenthos biomasses are relatively low, but nevertheless support high densities of consumers . Aquatic birds are especially numerous . The study identifies many research topics for the future .

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