Alpha and beta diversity of encrusting foraminifera that recruit to long-term experiments along a carbonate platform-to-slope gradient: Paleoecological and paleoenvironmental implications

The spatial and temporal distribution and diversity of sediment-dwelling foraminifera are reasonably well known, but encrusting (hard-substrate dwelling) foraminifera are little studied. Encrusting foraminifera are common in the worldʹs oceans, attached to floating debris or marine animals in the water column to living on rocks, sand grains and organisms in benthic environments from shallow to deep marine regions. With projected ocean acidification and warming conditions, these important calcifying protists that comprise beaches, buffer sediments, and contribute to complex food webs are potentially in peril. s indicate that calcifying foraminifera were the first to colonize experimental molluscan substrates within the first year in shallow habitats, with colonization offshore in subsequent years. Agglutinated foraminifera become more common after one year. Species richness (α diversity) remained relatively similar throughout the study, but species turnover (β diversity) was greatest within the first year and between the shelf/slope break and deeper water, following the thermocline and photic zone regions. The equivalent of the Shannon Entropy Index provided important information on β diversity and community structure. athymetric distributions can be resolved after six years into four distinct foraminiferal distributional zones: shallow shelf (15 m), outer shelf (33 m), shelf/slope break (73–88 m), and slope depths (> 213 m to 267 m). Some encrusting foraminifera are invasive, settling in high numbers within the first year, and increasing their abundance through the duration of the experiment. A foraminiferan, Discorbis bertheloti, was discovered to bioerode carbonate, and is a potentially excellent paleobathymetric indicator for 15–33 m depths. Results differ from previously reported pioneer and climax foraminiferal communities documented for Caribbean coral reefs, because long-term experiments reveal the spatial and temporal development and distribution of carbonate-producing encrusting foraminifera in these climatically-sensitive regions.