Catastrophic hypotheses for mass extinctions are commonly criticized because many taxa gradually disappear from the fossil record prior to the extinction. Presumably, a geologically instantaneous catastrophe would not cause a reduction in diversity or a series of minor extinctions before the actual mass extinction. Two types of sampling effects, however, could cause taxa to appear to decline before their actual biotic extinction. The first of these is reduced sample size provided in the sedimentary record and the second, which we examine in greater detail, is artificial range truncation. The fossil record is discontinuous in time and the recorded ranges of species or of higher taxa can only extend to their last known occurrence in the fossil record. If the distribution of last occurrences is random with respect to actual biotic extinction, then apparent extinctions will begin well before a mass extinction and will gradually increase in frequency until the mass extinction event, thus giving the appearance of a gradual extinction. Other factors, such as regressions, can exacerbate the bias toward gradual disappearance of taxa from the fossil record. Hence, gradual extinction patterns prior to a mass extinction do not necessarily eliminate catastrophic extinction hypotheses. The recorded ranges of fossils, especially of uncommon taxa or taxa in habitats not represented by a continuous record, may be inadequate to test either gradual or catastrophic hypotheses.

Although coral reefs occupy only 0.17% of the ocean surface, they contribute 900 million tons, or roughly one sixth of the carbonate produced in the world's oceans each year. Corals, coralline algae and foraminifera are by far the most important producers of sediment on reefs. In order to understand the role of foraminifera in reef and global carbonate production cycles, we estimated carbonate production rates of reef foraminifera from more than 70 sites in all oceanic regions. Our first order production estimate shows that reef foraminifera contribute approximately 43 million tons of CaCO ₃ per year, 34 million tons of which accumulate in reef sediments. Eighty percent of the global foraminiferal reef carbonate is estimated to be produced by larger symbiont-bearing species alone. The annual production of 43 million tons represents roughly 0.76 percent of the present-day CaCO ₃ production in the world's oceans and approximately 4.8 percent of the global carbonate reef budget. Given an average weight of 0.5 mg for the typical reef foraminifer, the production of 43 million tons translates into a yearly turnover rate of approximately 86X10 ¹⁵ individuals. The biochemical production of calcium carbonate in the ocean leads to the release of the greenhouse gas CO ₂ which can be discharged into the atmosphere. Using our first order approximation, the annual production of 43 million tons of foraminiferal reef carbonate results in the release of 11.4 million tons of CO ₂ . This represents only 0.05 percent of anthropogenic CO ₂ emission in 1991. On a global scale, both carbonate and CO ₂ production of reef foraminifera are comparatively small. In present-day reef complexes foraminifera do, however, play an essential role in the production of reef carbonates.

Samples and observations under 420 meters of ice and 430 kilometers from the open sea on the Ross Ice Shelf at a water depth of 597 meters revealed an unusual assemblage of benthic organisms. Scavenging amphipods, an isopod, and fish were present but a living infauna was absent. The observations may be accounted for by sampling or spatial bias, or by extremely low or fluctuating trophic resources.