Saturating light and not increased carbon dioxide under ocean acidification drives photosynthesis and growth in Ulva rigida (Chlorophyta)

Carbon physiology of a genetically identified Ulva rigida was investigated under different CO2(aq) and light levels. The study was designed to answer whether (1) light or exogenous inorganic carbon (Ci) pool is driving growth; and (2) elevated CO2(aq) concentration under ocean acidification (OA) will downregulate CAext-mediated inline image dehydration and alter the stable carbon isotope (delta13C) signatures toward more CO2 use to support higher growth rate. At pHT 9.0 where CO2(aq) is <1 ?mol/L, inhibition of the known inline image use mechanisms, that is, direct inline image uptake through the AE port and CAext-mediated inline image dehydration decreased net photosynthesis (NPS) by only 56-83%, leaving the carbon uptake mechanism for the remaining 17-44% of the NPS unaccounted. An in silico search for carbon-concentrating mechanism elements in expressed sequence tag libraries of Ulva found putative light-dependent inline image transporters to which the remaining NPS can be attributed. The shift in delta13C signatures from -22 per mil toward -10 per mil under saturating light but not under elevated CO2(aq) suggest preference and substantial inline image use to support photosynthesis and growth. U. rigida is Ci saturated, and growth was primarily controlled by light. Therefore, increased levels of CO2(aq) predicted for the future will not, in isolation, stimulate Ulva blooms.

Upper Cenozoic dinoflagellate cysts from the continental slope and rise off New Jersey

This report contains the occurrence data for dinoflagellate cysts recorded from 163 samples taken from Sites 902 through 906, during Ocean Drilling Program (ODP) Leg 150. The dinoflagellate cyst (dinocyst) stratigraphy has been presented in Mountain, Miller, Blum, et al. (1994, doi:10.2973/odp.proc.ir.150.1994), and was based on these data. This report provides the full dinocyst data set supporting the dinocyst stratigraphic interpretations made in Mountain, Miller, Blum, et al. (1994). For Miocene shipboard dinocyst stratigraphy, I delineated 10 informal zones: pre-A, and A through I, in ascending stratigraphic order. These zones are defined in Shipboard Scientific Party (1994a, doi:10.2973/odp.proc.ir.150.103.1994), and are based on my studies of Miocene dinocyst stratigraphy in the Maryland and Virginia coastal plain (de Verteuil and Norris, 1991, 1992; de Verteuil, 1995). This zonation has been slightly revised (de Verteuil and Norris, 1996), and the new formal zone definitions are repeated below. Each new zone has an alpha-numeric abbreviation starting with "DN" (for Dinoflagellate Neogene). The equivalence between the informal zones reported in Mountain, Miller, Blum, et al. (1994), and the new DN zones is illustrated in Figure 1. For clarity, I delineated both zonations in the range charts that accompany this report (Tables 1-6). De Verteuil and Norris (1996a), using these and other data, correlated the DN zonation with the geological time scale of Berggren et al. (1995). Figure 2 summarizes these correlations and can be used to check the chronostratigraphic position of samples in this report, as determined by dinocyst stratigraphy. A thorough discussion of the basis for, and levels of uncertainty associated with, these correlations to the Cenozoic time scale can be found in de Verteuil and Norris (1996a). The Appendix lists all the dinocyst taxa recorded during shipboard analyses of Leg 150 samples. Open nomenclature is used for undescribed taxa. The range charts and Appendix also include reference to several new taxa that de Verteuil and Norris (1996b) described from Miocene coastal plain strata in Maryland and Virginia. Names of these taxa in Tables 1 through 6 and in the Appendix of this report are not intended for effective publication as defined in the International Code of Botanical Nomenclature (ICBN, Greuter et al., 1994). Therefore, taxonomic nomenclature contained in this report is not to be treated as meeting the conditions of effective and valid publication (ICBN; Article 29).

Late Quateranry dinoflagellate cysts of ODP Site 202-1233

The late Quaternary organic-walled dinoflagellate cyst record of Site 1233 (41°S, offshore Chile) was studied with a ?200 year resolution spanning the last 25,000 years. The study provides the first continuous record of sub-recent and recent dinoflagellate cysts in the Southeast (SE) Pacific. Major changes in the composition of the cyst association, cyst concentration and morphology of Operculodinium centrocarpum reflect changes in sea surface temperature (SST), sea surface salinity (SSS), palaeoproductivity and upwelling intensity. These changes can be associated with latitudinal shifts of the circumpolar frontal systems. The high cyst concentration, high Brigantedinium spp. abundances, low species diversity and the occurrence of certain cold water species are supportive for a 7-10° equatorward shift of the Antarctic Circumpolar Current (ACC) during the coldest phase of the Last Glacial Maximum (LGM) between 25 and 21.1 cal ka BP. Deglacial warming initiated at ~18.6 cal ka BP. Termination I (18.6-11.1 cal ka BP) is interrupted by an unstable period of extreme seasonality, rather than a cooling event, between 14.4 and 13.2 cal ka BP, synchronous with the Antarctic Cold Reversal (ACR). The Holocene Maximum is observed between 11.6 and 9.8 cal ka BP and is typified by the most southward position of the northern margin of the ACC. A cooling phase occurred during the early Holocene (until ~7 cal ka BP) and during the last ~0.8 ka. Our data indicates that the SE Pacific (41°S) climate has been influenced over the whole record by changes in the Southern Hemisphere (SH) high-latitudes, while during the mid to late Holocene, also a tropical forcing mechanism was involved, including the El Niño Southern Oscillation and the variable Hadley cell intensity. Furthermore, this study showed a relationship between the variable morphology of the spines/processes of O. centrocarpum and the combined variation of sea surface salinity and temperature (SSS/SST-ratio).

(Table 2) Taxonomic composition of diatoms in dredged samples from the island-side slope of the Kuril-Kamchatka Trench

Studies of diatoms from dredge samples collected on the island slope of the Kuril-Kamchatka Trench have allowed to recognize well-preserved marine diatom assemblages corresponding to assemblages of the followed Oligocene zones: Rhizosolenia oligocaenica (subzone ''a'', 33.6-31 Ma), Cavitatus rectus (29.6-28.2 Ma), and Rocella gelida (28.2-24.0 Ma) as identified in the North Pacific zonal scale. Description of these assemblages and their complete taxonomic composition are presented. Diversity of species together with abundance and degree of preservation of diatoms and accompanying siliceous microorganisms suggests their autochtonous origin and favorable conditions of their development. Assemblages of the Early Oligocene zones Rhizosolenia oligocaenica and Cavitatus rectus recognized in sediments of the outer zone of the Lesser Kuril Ridge (submarine slope of the Shikotan Island) and on the Vityaz' submarine ridge were most probably formed under conditions of a vast shelf, while assemblage of the Late Oligocene zone Rocella gelida encountered only in the region of the Lesser Kuril Ridge formed under more deep-water conditions, presumably, over an island slope. Deepening of the basin in the region of the outer zone of the Lesser Kuril Ridge in Late Oligocene probably reflects one of stages of evolution of the Kuril-Kamchatka Trench.