The crustose coralline algae are well known in shallow tropical waters as reef frame-builders and sediment producers. Although their abundance at greater depths and in arctic waters has been previously recorded, this knowledge in recent decades has been largely ignored by geologists and marine scientists in general. Many erroneous or misleading ecological and paleoecological statements and conclusions have resulted, and we have endeavored to clarify matters through the citation of the older literature along with more recent ecological studies.
A parallel tendency to “simplify” the taxonomic structure of crustose corallines has threatened to add considerable confusion to modern marine studies. We have discussed recent work on anatomy, reproduction, and taxonomy. These and classical data are summarized in the form of keys and an evolutionary tree, which are intended to provide the geologist and marine biologist with a working facility with the group.
A number of quantitative ecological studies treating crustose corallines have appeared during the past decade; these results are discussed and possibilities for future ecological work indicated. The occurrence of rhodoliths (maerl, free corallines) and the factors controlling the development of these deposits are also noted.