Pliocene foraminifera and SST changes in ODP Site 184-1125

Planktonic foraminiferal census counts were converted to sea surface temperature (SST) estimates using the modern analogue technique (MAT) for the middle-late Pliocene (4.0-2.37 Ma) in ODP Site 1125, north side of Chatham Rise, SW Pacific Ocean. MAT SST(warm) records range between 8°C and 20.5°C, and MAT SST(cold) records parallel that pattern but with a temperature range of 5-15°C. The modern position of Site 1125 is just north of the Subtropical Front and has an annual temperature range of ~14-18°C. Pliocene warmest temperatures are 1-2° warmer than modern summers, whereas cold season SST records are up to 6-10°C cooler than modern winters. Overall average temperatures at the site are 2-3°C cooler than modern temperatures during a time of sustained global warmth. Three major cold excursions centred on 3.35, 3.0, and 2.8 Ma showed warm season temperatures over 5°C colder than the last glacial maximum, experiencing temperatures typical of modern subantarctic waters. Two minor cold excursions at 2.7 Ma and 2.4 Ma experienced temperatures cooler than modern winters but not as cold as last glacial conditions. Cold season SSTs show a shift to warmer climate upward through the study interval, whereas warm season estimates remain essentially unchanged. We interpret the strong regional cooling of subtropical Southwest Pacific water through the middle-late Pliocene as having been caused by increased upwelling. It is also possible that the subtropical frontal zone moved north over the site in the Pliocene, however, this is considered the least likely interpretation. Our record of cool conditions in the Southwest Pacific corroborate evidence of cooler than modern conditions in other regions of the western Pacific through the mid-Pliocene despite overall global warming.

Planktonic foraminifera of ODP Site 117-722

Quantitative analysis of the late Cenozoic planktonic foraminiferal record from western Arabian Sea Site 722 revealed long term trends in the history of oceanography and climate. The modern western Arabian Sea surface waters are highly influenced by the monsoonal wind system. Summer upwelling, a result of southwestern winds, occurs along the coast of Somalia which produces distinct foraminiferal assemblages which are dominated by G. bulloides d'Orbigny. Consequently, variations in the distribution record of G. bulloides through time monitor the upwelling history associated with monsoonal activities. G. bulloides was a minor constituent of the foraminiferal fauna from the bottom of the hole (~14.5 Ma) until about 8.6 Ma ago. Then a rapid shift occurred toward higher values, up to 53% at 7.4 Ma. We interpret this rapid increase as a major step in the evolution of the monsoonal history. It is either the establishment of the system or at least a strong intensification of the monsoonal winds. At 5.5 Ma a significant drop of the G. bulloides relative abundance occurred which may indicate less upwelling, or alternatively other biota may have been favored in this period. From 5.0 Ma to Recent the G. bulloides record indicates that upwelling has occurred with minor fluctuations.

Ages and diatom temperature values of DSDP sites in the western Pacific Ocean

Maximum entropy spectral analyses and a fitting test to find the best suitable curve for the modified time series based on the non-linear least squares method for Td (diatom temperature) values were performed for the Quaternary portion of the DSDP Sites 579 and 580 in the western North Pacific. The sampling interval averages 13.7 kyr in the Brunhes Chron (0-780 ka) and 16.5 kyr in the later portion of the Matuyama Chron (780-1800 ka) at Site 580, but increases to 17.3 kyr and 23.2 kyr, respectively, at Site 579. Among dominant cycles during the Brunhes Chron, there are 411.5 kyr and 126.0 kyr at Site 579, and 467.0 kyr and 136.7 kyr at Site 580 correspond to 413 kyr and 95 to 124 kyr of the orbital eccentricity. Minor cycles of 41.2 kyr at Site 579 and 41.7 kyr at Site 580 are near to 41 kyr of the obliquity (tilt). During the Matuyama Chron at Site 580, cycles of 49.7 kyr and 43.6 kyr are dominant. The surface-water temperature estimated from diatoms at the western North Pacific DSDP Sites 579 and 580 shows correlation with the fundamental Earth's orbital parameters during Quaternary time.

Palynology of ODP Leg 127 sites

This initial survey of pollen from 192 samples from Hole 794A, supplemented by 189 samples from Hole 795 and 797B, suggests that marine pollen assemblages from the southwestern Sea of Japan provide a consistent Neogene pollen stratigraphy and a solid basis for regional paleoenvironmental reconstructions. Late Miocene vegetation inferred from these pollen data, a mix of conifer and broad-leaf elements with now-extinct Tertiary types well represented, appears similar to Aniai-type floras of Japan. During the late Miocene through early Pliocene, as Tertiary types declined, conifers (including the Sequoia/Cryptomeria group) became more prominent than broad-leaf elements, and herbs played an increasing role in the vegetation. Middle Pliocene pollen assemblages imply significant changes in forest composition. In a 500,000-yr interval centered at ~4 m.y., Tertiary and warm-temperate deciduous types re-expanded and were comparable to or greater than middle-late Miocene levels. Temperate and cold-temperate conifers {Picea, Abies, Tsuga) were minimal. Subsequently, Tertiary and deciduous forest components (including Quercus) decreased, Picea, Tsuga, and Abies were again prominent, and herbs formed an increasingly larger part of the vegetation. Between ~3 m.y. and -2.5 m.y., conifers, except for Cryptomeria types, were prominent, Quercus continued to decline, and other broad-leaf trees were minor. Over the last 2 Ma, the very large and frequent changes in forest composition inferred from pollen in the Sea of Japan correspond to forest dynamics inferred from changes in pollen and floral assemblages throughout Japan. Given present vegetation/climate relationships, broad trends in Neogene climate inferred from these preliminary pollen data include decreasing temperatures, increasing seasonality in temperatures and precipitation, and increasing amplitude and frequency of climatic change. Two significant events, centered at ~9 m.y. and ~4 m.y., punctuate the gradual deterioration of the equable warm, humid subtropical/warm temperate late Miocene and early Pliocene climates. The first indication of cold-temperate conditions comparable to those of Pleistocene glacial intervals occurs ~3 m.y. Subsequently, regional climates oscillated rapidly between temperate and cold-temperate regimes that supported conifer and mixed broad-leaf forests; however, climatic extremes were apparently never great enough to displace warm-temperate and temperate forests from Honshu nor to produce arctic climates on the west coast of Japan.

(Table 2) Chemical composition of gases in basalts from DSDP Leg 65 Holes

Basalts from different structural provinces in the ocean basins, such as mid-ocean ridges, island arcs, and oceanic plateaus, show marked differences in major and minor element composition stemming from differences in magma source. In addition, there are variations even within individual provinces, based on such processes as crystal fractionation, secondary alteration, and hydrothermal alteration. It is also known that hydrothermal processes can cause changes in the gas composition of submarine basalts. For example, Zolotarev et al. (1978) have established that hydrothermal alteration frequently causes an increase in the CO2 content of basalts. If the homogeneity in composition and concentration of organic gases in oceanic basalts is associated with degassing during epimagmatic alteration, it would be interesting to investigate the relative abundance of gas phases in young basalts from midoceanic ridges. This chapter deals with the distribution of organic gases and CO2 in young basalts recovered on Leg 65 from the Gulf of California. Our aim was to establish the relationship between gas composition and degree of alteration.

(Table S2) Cell concentrations of individual and combined Alexandrium spp. and phylogenetic groups as obtained by qPCR assay and Utermöhl counts, as well as particulate PSP toxin concentrations from discrete water depths

Molecular methods provide promising tools for routine detection and quantification of toxic microalgae in plankton samples. To this end, novel TaqMan minor groove binding probes and primers targeting the small (SSU) or large (LSU) ribosomal subunit (rRNA) were developed for two species of the marine dinoflagellate genus Alexandrium (A. minutum, A. tamutum) and for three groups/ribotypes of the A. tamarense species complex: Group I/North American (NA), Group II/Mediterranean (ME) and Group III/Western European (WE). Primers and probes for real-time quantitative PCR (qPCR) were species-specific and highly efficient when tested in qPCR assays for cross-validation with pure DNA from cultured Alexandrium strains. Suitability of the qPCR assays as molecular tools for the detection and estimation of relative cell abundances of Alexandrium species and groups was evaluated from samples of natural plankton assemblages along the Scottish east coast. The results were compared with inverted microscope cell counts (Utermöhl technique) of Alexandrium spp. and associated paralytic shellfish poisoning (PSP) toxin concentrations. The qPCR assays indicated that A. tamarense (Group I) and A. tamutum were the most abundant Alexandrium taxa and both were highly positively correlated with PSP toxin content of plankton samples. Cells of A. tamarense (Group III) were present at nearly all stations but in low abundance. Alexandrium minutum and A. tamarense (Group II) cells were not detected in any of the samples, thereby arguing for their absence from the specific North Sea region, at least at the time of the survey. The sympatric occurrence of A. tamarense Group I and Group III gives further support to the hypothesis that the groups/ribotypes of the A. tamarense species complex are cryptic species rather than variants belonging to the same species.

Table 2: Evaporation from individual shoots of antarctic mosses

Experimental observations on pathways of water movement are discussed in relation to anatomical and micromorphological features of five moss species from Signy Island, South Orkney Islands. Significant internal uptake of water was recorded only in the mesic species Polytrichum alpinum (internal=>60% of total) and Bartramia patens (internal=c.30% of total), in experiments in which uptake by cut shoots was compared in individuals with the external pathway blocked, and others with both external and internal pathways open. Internal uptake maintained shoot water content close to full turgor in P. alpinun and at 30% of full tugor in B. patens, whereas water content fell to 12-15% dry wt. in the lithophytes Andreaea gainii and Schistidium antarctici and in the mesic/hydric species Drepanocladus uncinatus, with the external pathway blocked. Where both pathways were open water uptake from below maintained water content at or above full turgor in shoots of all five species. External water uptake by capillarity occurred most rapidly in the lithophytes, and was slower in initially air-dry than in hydrated shoots of the other species. The spreading limbs of leaves in B. patens and P. alpinum are water-repellent, as are the bright green leaves in the apical 1-2 mm of dry shoots of the lithophytes. A central strand of hydroids is well-developed only in B. patens and P. alpinum. These two species have deposits of surface wax on parts of the leaves, and surface wax also occurs on the green apical leaves in some specimens of S. antarcticum and other lithophytes from Signy Island.