Cruoriella rhodoliths from shallow-water back reef environments in La Parguera, Puerto Rico (Caribbean Sea)

The occurrence of shallow-water (0.9 to 1.3 m) rhodoliths in back reef envi ronments in southwest Puerto Rico is reported. The rhodoliths were generall y cylindrical, discoidal or irregular in shape with an average longest dime nsion of 7.2 cm. They occurred at a maximum density of 524 m(-2). The rhodo liths were composed of mostly coral nuclei with concentric laminations of a ragonite-producing Cruoriella armorica (Peyssonneliaceae, Rhodophyta). Maxi mum Cruoriella accretion around coral nuclei was 30 mm although accretions of 1 to 20 mm were more common. Based on measurements of Cruoriella accreti on, these shallow water rhodoliths are estimated to have minimum ages of 12 to 24 years. It is further estimated that approximately 2% of the rhodolit hs are turned over daily.