Images and animation of a complex microboring (Pyrodendrina cupra n. igen. and isp.) from the early Paleozoic of Anticosti Island, Canada

Three complementary imaging techniques were used to describe a complex rosette-shaped microboring that penetrates the shells of brachiopods from the Ordovician–Silurian shallow marine limestones of Anticosti Island, Canada. Pyrodendrina cupra n. igen. and isp. is among the oldest dendrinid microborings and consists of shallow and deep penetrating canals that radiate from a central polygonal chamber. The affinity of the tracemaker is unknown, but a foraminiferal origin, as proposed for some dendrinid borings, is rejected. Combining microCT with traditional stereomicroscopy and SEM helped distinguish and quantify fine morphological features while maintaining contextual information of the microboring within the shell substrate. Different imaging techniques inherently bias the description of microborings. These biases must be accounted for as new methods in ichnotaxonomy are integrated with past research based on different methods.

Automated Tools for Layer Recognition (BMPix) and Counting (PEAK)

We present tools for rapid and quantitative detection of sediment lamination. The BMPix tool extracts color and gray-scale curves from images at pixel resolution. The PEAK tool uses the gray-scale curve and performs, for the first time, fully automated counting of laminae based on three methods. The maximum count algorithm counts every bright peak of a couplet of two laminae (annual resolution) in a smoothed curve. The zero-crossing algorithm counts every positive and negative halfway-passage of the curve through a wide moving average, separating the record into bright and dark intervals (seasonal resolution). The same is true for the frequency truncation method, which uses Fourier transformation to decompose the curve into its frequency components before counting positive and negative passages. We applied the new methods successfully to tree rings, to well-dated and already manually counted marine varves from Saanich Inlet, and to marine laminae from the Antarctic continental margin. In combination with AMS14C dating, we found convincing evidence that laminations in Weddell Sea sites represent varves, deposited continuously over several millennia during the last glacial maximum. The new tools offer several advantages over previous methods. The counting procedures are based on a moving average generated from gray-scale curves instead of manual counting. Hence, results are highly objective and rely on reproducible mathematical criteria. Also, the PEAK tool measures the thickness of each year or season. Since all information required is displayed graphically, interactive optimization of the counting algorithms can be achieved quickly and conveniently.

Short- versus long-term responses to changing CO2 in a coastal dinoflagellate bloom

Increasing pCO2 (partial pressure of CO2 ) in an "acidified" ocean will affect phytoplankton community structure, but manipulation experiments with assemblages briefly acclimated to simulated future conditions may not accurately predict the long-term evolutionary shifts that could affect inter-specific competitive success. We assessed community structure changes in a natural mixed dinoflagellate bloom incubated at three pCO2 levels (230, 433, and 765 ppm) in a short-term experiment (2 weeks). The four dominant species were then isolated from each treatment into clonal cultures, and maintained at all three pCO2 levels for approximately 1 year. Periodically (4, 8, and 12 months), these pCO2 -conditioned clones were recombined into artificial communities, and allowed to compete at their conditioning pCO2 level or at higher and lower levels. The dominant species in these artificial communities of CO2 -conditioned clones differed from those in the original short-term experiment, but individual species relative abundance trends across pCO2 treatments were often similar. Specific growth rates showed no strong evidence for fitness increases attributable to conditioning pCO2 level. Although pCO2 significantly structured our experimental communities, conditioning time and biotic interactions like mixotrophy also had major roles in determining competitive outcomes. New methods of carrying out extended mixed species experiments are needed to accurately predict future long-term phytoplankton community responses to changing pCO2 .

Chemical observations in the Red Sea and the inner Gulf of Aden during the International Indian Ocean Expedition 1964/65

The Red Sea has a special place among the adjacent seas of the world. High evaporation, exclusion of its deep water from contact with the Indian Ocean proper and complete absence of continental drainage may result special conditions of the chemistry of the Red Sea. This paper aims to describe and explain the peculiarity of the hydrochemical situation. The influence of the topography, of the inflow and outflow through the straights of Bab el Mandeb, of the evaporation, of the stability of the water layers, and of the circulation will be studied. An attempt is made to estimate the apparent oxygen ultilisation in order to obtain an indication of the biological activity. A further attempt is made toward the quantitative estimation of the circulation of the nutrients and also to obtain some information about transport, dissolution, and precipitation of calcium carbonate. The basis of these investigations are mainly observations of R. V. "Meteor" during the International Indian Ocean Expedition 1964/65. The determination of dissolved oxygen, dissolved inorganic phosphate, nitrate, nitrite, ammonia, pH, alkalinity, silicate as well as salinity and temperature forms the necessary basis for such an investigation of the chemical conditions. In the first chapter the methods and some modifications for the determination of the chemical properties as applied during the I.I.O.E. cruise of R. V. "Meteor" are described. The new methods, as worked out and tested under sea going conditions during several years by the author, are described in more detail. These are the methods for nitrate, silicate, the automatic determination of dissolved inorganic phosphate and silicate, the automated determination of total phosphorus, the in situ recording of the oxygen tension, and the modification for the determination of ammonia, calcium, and dissolved oxygen. With these revised methods more than 18,000 determinations have been carried out during the Indian Ocean cruise. The complete working up of the chemical data of the Indian Ocean Expedition of R. V. "Meteor" is devided into four sections: Contributions 1) to the Chemistry of the Red Sea and the Inner Gulf of Aden, 2) to the Gulf of Aden and the Somali Coast Region, 3) to the Western Indian Coast Region, and 4) to the Persian Gulf and the Straits of Oman. This paper presents the first contribution. The special hydrographical conditions are discussed. It can be shown, that the increase of salinity in the surface waters from the south to the north of the Red Sea is only to about 30 % due to evaporation. The remaining increase is presumed to be due to the admixture of deep water to the surface layers. A special rate for the consumption of oxygen (0.114 ml/ l/a) is derived for the deep water of the Red Sea at 1500 m. Based upon the distribution of the dissolved oxygen along the axii of the Red Sea, a chematic model for the longitudinal circulation of the Red Sea is constructed. This model should be considered as a first approximation and may explain the special distribution of phosphate, nitrate, and silicate. Based upon the evaluation of the residence time of the deep water a dissolution rate for silicate is estimated as 1 mygat/a. It seems possible to calculate residence times of water masses outside the Red Sea from the silicate content. The increase of silicate and the consumption of oxygen lead to residence times of the water below the thermocine of 30 to 48 years. The distribution of oxygen in the Straits of Bab el Mandeb is described and discussed. The rate of consumption of the oxygen in the outflowing Red Sea water is estimated to 8.5 ml/ l/a. This rather high rate is explained with reference to the special conditions in the outflowing water. The Red Sea water is characterized initially by a relative high content of oxygen and a low content of nutrients. The increase in nutrients and the decrease in the oxygen content is a secondary process of the Red Sea water on its way to the Arabian Sea. Based upon the vertical distribution of the dissolved inorganic phosphate vertical exchange coefficients of 1 - 4 g/cm/sec and vertical current speeds of 10**-5 to 10**-4 cm/sec are calculated for some stations in the Red Sea. The distribution of phosphate, silicate, nitrate, nitrite and ammonia for the Red Sea and the Straits of Bab el Mandeb are discussed. The special circulation is evaluated and the balance of the nutrients is estimated by means of the brutto transport. The nutrient deficit is assumed to be balanced by sporadic inflow of intermediate water from the Gulf of Aden. An example for such an inflow has been observed and is demonstrated. The silicate-salinity relationships are a suitable way for characterizing water masses in the Red Sea. Equations for the calculation of the different components from the carbonate system, the ion activities, and the calcium carbonate saturation are evaluated. The influence of temperature and pressure is taken into account. The carbonate saturation is calculated from the determined concentrations of calcium, alkalinity, and the hydrogen ion activity. Saturation values of 320 % are found for the surface layer and of 100% ± 1 for the deep water. The extraordinary equilibrium conditions may explain the constant Ca/Cl ratio and also the sedimentation of undissolved carbonate skelecons even in greater depths. A main sedimentation rate of 2 * 10**-3cm/year is evaluated from a total sedimentation of 10 * 106 to/a of calcium carbonate in the Red Sea. The appendix contains those data, which are not published in the data volume of the I.I.O.E. expedition of R. V. "Meteor".

An environmental magnetic study, sedimentological and numerical methods around Tauranga Harbour, New Zealand

Magnetic iron minerals are widespread and indicative sediment constituents in estuarine, coastal and shelf systems. We combine environmental magnetic, sedimentological and numerical methods to identify magnetite-enriched placer-like zones in a complex coastal system and delineate their formation mechanisms. Magnetic susceptibility and remanence measurements on 245 surficial sediment samples collected in and around Tauranga Harbour, the largest barrier-enclosed tidal estuary of New Zealand, reveal several discrete enrichment zones controlled by local hydrodynamic conditions. Active magnetite enrichment takes place in tidal channels, which feed into two coast-parallel nearshore magnetite-enriched belts centered at water depths of 6-10 m and 10-20 m. A close correlation between magnetite content and magnetic grain size was found, where higher susceptibility values are associated within coarser magnetic crystal sizes. Two key mechanisms for magnetite enrichment are identified. First, tide-induced residual currents primarily enable magnetite enrichment within the estuarine channel network. A coast-parallel, fine sand magnetite enrichment belt in water depths of less than 10 m along the barrier island has a strong decrease in magnetite content away from the southern tidal inlet and is apparently related to active coast-parallel transport combined with mobilizing surf zone processes. A second, less pronounced, but more uniform magnetite enrichment belt at 10-20 m water depth is composed of non-mobile, medium-coarse-grained relict sands, which have been reworked during post-glacial sea level transgression. We demonstrate the potential of magnetic methods to reveal and differentiate coastal magnetite enrichment patterns and investigate their formative mechanisms.