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.

Marine planktonic diatoms export carbon to the deep ocean, playing a key role in the global carbon cycle. Although commonly thought to have diversified over the Cenozoic as global oceans cooled, only two conflicting quantitative reconstructions exist, both from the Neptune deep-sea microfossil occurrences database. Total diversity shows Cenozoic increase but is sample size biased; conventional subsampling shows little net change. We calculate diversity from a separately compiled new diatom species range catalog, and recalculate Neptune subsampled-in-bin diversity using new methods to correct for increasing Cenozoic geographic endemism and decreasing Cenozoic evenness. We find coherent, substantial Cenozoic diversification in both datasets. Many living cold water species, including species important for export productivity, originate only in the latest Miocene or younger. We make a first quantitative comparison of diatom diversity to the global Cenozoic benthic ∂18O (climate) and carbon cycle records (∂13C, and 20-0 Ma pCO2). Warmer climates are strongly correlated with lower diatom diversity (raw: rho = .92, p<.001; detrended, r = .6, p = .01). Diatoms were 20% less diverse in the early late Miocene, when temperatures and pCO2 were only moderately higher than today. Diversity is strongly correlated to both ∂13C and pCO2 over the last 15 my (for both: r>.9, detrended r>.6, all p<.001), but only weakly over the earlier Cenozoic, suggesting increasingly strong linkage of diatom and climate evolution in the Neogene. Our results suggest that many living marine planktonic diatom species may be at risk of extinction in future warm oceans, with an unknown but potentially substantial negative impact on the ocean biologic pump and oceanic carbon sequestration. We cannot however extrapolate our my-scale correlations with generic climate proxies to anthropogenic time-scales of warming without additional species-specific information on proximate ecologic controls.

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This paper summarizes the biostratigraphy and magnetostratigraphy of the 11 sites drilled on the Kerguelen Plateau and in Prydz Bay, Antarctica, during ODP Leg 119. Excellent magnetobiochronologic reference sections were obtained at deep-water Sites 745 and 746 (0-10 Ma) and at intermediate depth Site 744 (0-39 Ma) on the southern Kerguelen Plateau. Site 738, an intermediate depth companion site for Site 744, contains a nearly complete lowermost Oligocene to Turonian carbonate section including a continuous sequence across the Cretaceous/Tertiary boundary. Northern Kerguelen Sites 736 and 737 (ca. 600 m water depth) constitute a composite middle Eocene to Quaternary reference section near the present-day Antarctic Polar Front. Biostratigraphic control is limited in Prydz Bay Sites 739-743. Glacial sequences cored on the continental shelf at Sites 739 and 742 appear to form a composite record, possibly from the uppermost middle Eocene to the Quaternary; the entire upper Oligocene and most of the Miocene, however, are removed at an unconformity. Preglacial sediments at Site 741 contain Early Cretaceous pollen and spores, but the red beds cored at Site 740 are unfossiliferous. Poorly-fossiliferous glacial sediments of probable Quaternary age were sampled on the upper slope at Site 743. A magnetobiochronologic time scale is presented for the Late Cretaceous and Cenozoic of the Southern Ocean based on previous studies and the results of Leg 119 studies.

It has been hypothesized that increased water column stratification has been an abiotic ''universal driver'' affecting average cell size in Cenozoic marine plankton. Gradually decreasing Cenozoic radiolarian shell weight, by contrast, suggests that competition for dissolved silica, a shared nutrient, resulted in biologic coevolution between radiolaria and marine diatoms, which expanded dramatically in the Cenozoic. We present data on the 2 components of shell weight change-size and silicification-of Cenozoic radiolarians. In low latitudes, increasing Cenozoic export of silica to deep waters by diatoms and decreasing nutrient upwelling from increased water column stratification have created modern silicapoor surface waters. Here, radiolarian silicification decreases significantly (r ‫؍‬ 0.91, P < 0.001), from Ϸ0.18 (shell volume fraction) in the basal Cenozoic to modern values of Ϸ0.06. A third of the total change occurred rapidly at 35 Ma, in correlation to major increases in water column stratification and abundance of diatoms. In high southern latitudes, Southern Ocean circulation, present since the late Eocene, maintains significant surface water silica availability. Here, radiolarian silicification decreased insignificantly (r ‫؍‬ 0.58, P ‫؍‬ 0.1), from Ϸ0.13 at 35 Ma to 0.11 today. Trends in shell size in both time series are statistically insignificant and are not correlated with each other. We conclude that there is no universal driver changing cell size in Cenozoic marine plankton. Furthermore, biologic and physical factors have, in concert, by reducing silica availability in surface waters, forced macroevolutionary changes in Cenozoic low-latitude radiolarians.evolution ͉ microfossils ͉ micropaleontology ͉ morphometrics ͉ Ocean Drilling Program T he evolution of ocean plankton has played an important role in the development of the earth's climate system, and changes in ocean plankton may affect future changes in climate (1). The deep-sea microfossil record of protist plankton provides an unusual opportunity to understand how plankton evolution and environmental change mutually affect each other. Recently, it has been proposed that Cenozoic changes in upper ocean water column stratification have influenced the evolution of cell size in a variety of marine protist plankton groups, including planktonic foraminifera (2), diatoms (3), and dinoflagellates (4), and it has been suggested that these patterns are indicative of a ''universal driver'' of size change in Cenozoic plankton (4). The polycystine radiolarians are an important marine protist zooplankton group abundant as fossils in Cenozoic and Mesozoic deep-sea sediments. Their general size, feeding ecology, and distribution patterns are similar to those of the better-known planktonic foraminifera (5, 6), although radiolarians are more diverse and, at least since the Oligocene (7), possess distinct, diverse endemic high-latitude faunas. Radiolarians are most diverse in low latitudes and most abundant in near-surface waters, although some species inhabit ...

SummaryCharles Darwin, like others before him, collected aeolian dust over the Atlantic Ocean and sent it to Christian Gottfried Ehrenberg in Berlin. Ehrenberg's collection is now housed in the Museum of Natural History and contains specimens that were gathered at the onset of the Industrial Revolution. Geochemical analyses of this resource indicated that dust collected over the Atlantic in 1838 originated from the Western Sahara, while molecular-microbiological methods demonstrated the presence of many viable microbes. Older samples sent to Ehrenberg from Barbados almost two centuries ago also contained numbers of cultivable bacteria and fungi. Many diverse ascomycetes, and eubacteria were found. Scanning electron microscopy and cultivation suggested that Bacillus megaterium, a common soil bacterium, was attached to historic sand grains, and it was inoculated onto dry sand along with a non-sporeforming control, the Gram-negative soil bacterium Rhizobium sp. NGR234. On sand B. megaterium quickly developed spores, which survived for extended periods and even though the numbers of NGR234 steadily declined, they were still considerable after months of incubation. Thus, microbes that adhere to Saharan dust can live for centuries and easily survive transport across the Atlantic.

Speciation processes are only rarely studied with fossil materials, even though in principle hypotheses of speciation patterns are most directly testable in the fossil record. We quantitatively document in two widely separated South Pacific DSDP holes the mid-Pliocene speciation of the planktonic foraminifer Globorotalia truncatulinoides. Speciation, with continuous geographic co-occurrence of ancestor and descendant forms, occurred simultaneously at both localities over a period of ~500,000 years. This suggests a sympatric speciation process that involved a large, geographically extensive population. Globorotalia truncatulinoides underwent its most rapid and extensive evolutionary change between ~2.8 and 2.5 Ma. This time interval corresponds to the development of northern hemisphere glaciation, suggesting that climate-controlled paleoceanographic change may have played a significant role in the evolution of G. truncatulinoides.

Morphometric examination of cladogenesis and phyletic evolution in two late Neogene sister lineages of marine microfossils (Pterocanium prismatium and P. charybdeum, Radiolaria) from two equatorial Pacific sediment cores was undertaken to better understand the rate of cladogenesis and its relation to subsequent phyletic change. The origin of P. prismatium from P. charybdeum ∼4 ma ago has been estimated to take place over an interval of ∼500,000 yr. Results show that the speciation event consists of two distinct phases. The first phase, cladogenesis, occurred relatively rapidly (on the order of 50,000 yr). A second phase of relatively rapid divergent phyletic evolution away from the common ancestral state followed in both descendant branches and continued for at least 500,000 yr after completion of the cladogenetic event. Net evolutionary rates over the next 2 ma appear to be much lower. Individual characters change by as much as 2 population standard deviations during cladogenesis, and by a total of approximately 3 standard deviations over 2.5 ma of phyletic evolution. Up to 5 population standard deviations of change during ≦ 50,000 yr of cladogenesis, and 7 additional standard deviations of phyletic change over 500,000 yr are observed in multivariate (discriminant function) indices of morphologic difference. The measured pattern does not appear to be either strictly “punctuated” or strictly “gradual,” but instead shows features of both hypotheses.