Effects of ligand speciation on determinations of the complexing abilities of strong ligands in natural waters

The presence of organic ligands (L) whose conditional stability constants (K_ML) are strong enough to allow them to form complexes with copper has been reported in oceanic waters. However, there is no general agreement on the distributional characteristics of such strong ligands in the water column. We present that these inconsistencies are derived from not only different analytical methods employed for their detection but also different oceanographic conditions. In particular, the nature and quantities of detectable natural ligands are affected by what kind of form the ligands are presentin situ in different marine environments, that is, chemical speciation of natural ligands (ligand speciation), which depends strongly on the variations in concentrations of coexisting trace metals. Using published data from observations in the laboratory and the field, we provide limits to the ranges of conditional stability constants of organic ligands for copper, zinc and cadmium that are detectable by the extensively used direct metal-titration method. For example, our model indicates that organic ligands for copper with log K_CuL(Cu)>12.4 in surface water and with log K_CuL(Cu)>9.9 in deep water might not have been detected because stronger ligands had formed complexes with ambient metalsin situ at a station in the North Pacific. The estimation suggests that there is a basinscale difference in speciation of natural organic ligands and, moreover, that this difference influences metal speciation. It is postulated that comparisons of the occurrence and levels of organic ligands might not be possible among spatially and temporally different observations without reconciliation of the effects of speciation of the ligands, even if an identical method is used in every case.     

Entrainment of bottom sediment in the Seto Inland Sea in summer

Time series of the vertical distribution of resuspended matter and bottom current were collected concurrently during summer at a few anchored stations in the Seto Inland Sea. The vertical distribution of resuspended matter was measured every hour for about one tidal cycle and the three components of current fluctuation were obtained at each sampling station. Current data at each sampling station show that the bottom is hydraulically smooth.Assuming that the averaged vertical distribution of resuspended matter for one tidal cycle shows a steady state distribution, the settling velocityWs of resuspended matter is estimated to be in the range of 1.2×10^–2 to 5.7×10^–2 cm sec^–1 from analysis of the averaged distributions.The relation between the erosion rate and the bottom shear stress for this study area is investigated and is compared with that for other areas. The results show that the erosion of sediment in the Seto Inland Sea during summer occurs even due to the low bottom shear stress which is considered as almost smooth hydraulically.     

Mechanisms controlling the temporal variation of the sea ice edge in the Southern Ocean

This paper examines the mechanism controlling the short time-scale variation of sea ice cover over the Southern Ocean. Sea ice concentration and ice velocity datasets derived from images of the Defense Meteorological Satellite Program (DMSP) Special Sensor Microwave Imager (SSM/I) are employed to reveal this mechanism. The contribution of both dynamic and thermodynamic processes to the change in ice edge location is examined by comparing the meridional velocity of ice edge displacement and sea ice drift. In the winter expansion phase, the thermodynamic process of new ice production off the ice edge plays an important role in daily advances of ice cover, whereas daily retreats are mostly due to southward ice drift. On the other hand, both advance and retreat of ice edges in the spring contraction phase are mostly caused by the dynamic process of the ice drift. Based on the above mechanism and the linear relation between the degree of ice production at the ice edge and northward wind speed, the seasonal advance of ice cover can be roughly reproduced using the meridional velocity of ice drift at the ice edge.     

The Levant Slumps and the Phoenician Structures: collapse features along the continental margin of the southeastern Mediterranean Sea

Two distinct series of slumps deform the upper part of the sedimentary sequence along the continental margin of the Levant. One series is found along the base of the continental slope, where it overlies the disrupted eastern edge of the Messinian evaporites. The second series of slumps transects the continental margin from the shelf break to the Levant Basin. It seemed that the two series were triggered by two unrelated, though contemporaneous, processes. The shore-parallel slumps were initiated by basinwards flow of the Messinian salt, that carried along the overlying Plio-Quaternary sediments. Seawater that percolated along the detachment faults dissolved the underlying salt to form distinctly disrupted structures. The slope-normal slumps are located on top of large canyons that cut into the pre-Messinian sedimentary rocks. A layer of salt is found in the canyons, and the Plio-Quaternary sediments were deposited on that layer. The slumps are bounded by large, NW-trending faults where post-Messinian faulted offset was measured. We presume that the flow of the salt in the canyons also drives the slope-normal slumps. Thus thin-skinned halokynetic processes generated the composite post-Tortonian structural patterns of the Levant margin. The Phoenician Structures are a prime example of the collapse of a distal continental margin due to the dissolution of a massive salt layer.     

Total amount of oceanic excess CO2 taken from the North Pacific subpolar region

Concentrations of total carbonate, alkalinity and dissolved oxygen were obtained near the 1973 GEOSECS stations in the North Pacific subpolar region north of 40°N along 175°E between 1993 and 1994. A difference of excess CO₂ content between the GEOSECS and our expeditions was estimated. The maximum difference in water column inventory of excess CO₂ has increased by about 280 gC m^–2 above 2000 m depth which apparently means an uptake of excess CO₂ taken from air to sea during the last two decades. An averaged value of the annual flux of excess CO₂ at 75–1000 m depth was 8.63±2.01 gC m^–2yr^–1 in the North Pacific subpolar region. By introducing the annual flux of excess CO₂ into a two-box model for the North Pacific subpolar region, a penetration factor of excess CO₂ from air to sea was obtained to be 1.08×10^–2 gC m^–3ppm^–1 in the North Pacific subpolar region. Based on this factor, the surface concentration of excess CO₂ in the North Pacific subpolar region was estimated to be 68 mole I^–1, suggesting that the North Pacific subpolar region absorbed atmospheric excess CO₂ more than the saturated concentration of excess CO₂. Total amount of excess CO₂ taken from the North Pacific subpolar region by 1993 was estimated to be 36.2×10¹⁵ gC, which was equal to about one tenth of that released by human activities after the preindustrial era.     

Mixed layer variability in Northern Arabian Sea as detected by an Argo float

Seasonal evolution of surface mixed layer in the Northern Arabian Sea (NAS) between 17° N–20.5° N and 59° E-69° E was observed by using Argo float daily data for about 9 months, from April 2002 through December 2002. Results showed that during April - May mixed layer shoaled due to light winds, clear sky and intense solar insolation. Sea surface temperature (SST) rose by 2.3 °C and ocean gained an average of 99.8 Wm⁻². Mixed layer reached maximum depth of about 71 m during June - September owing to strong winds and cloudy skies. Ocean gained abnormally low ∼18 Wm⁻² and SST dropped by 3.4 °C. During the inter monsoon period, October, mixed layer shoaled and maintained a depth of 20 to 30 m. November - December was accompanied by moderate winds, dropping of SST by 1.5 °C and ocean lost an average of 52.5 Wm⁻². Mixed layer deepened gradually reaching a maximum of 62 m in December. Analysis of surface fluxes and winds suggested that winds and fluxes are the dominating factors causing deepening of mixed layer during summer and winter monsoon periods respectively. Relatively high correlation between MLD, net heat flux and wind speed revealed that short term variability of MLD coincided well with short term variability of surface forcing.     

Spatial and Temporal Variations of Sound Speed at the PN Section

Gridded sound speed data were calculated using Del Grosso's formulation from the temperature and salinity data at the PN section in the East China Sea covering 92 cruises between February 1978 and October 2000. The vertical gradients of sound speed are mainly related to the seasonal variations, and the strong horizontal gradients are mainly related to the Kuroshio and the upwelling. The standard deviations show that great variations of sound speed exist in the upper layer and in the slope zone. Empirical orthogonal function analysis shows that contributions of surface heating and the Kuroshio to sound speed variance are almost equivalent. This revised version was published online in July 2006 with corrections to the Cover Date.     

Seasonal variations of water system distribution and flow patterns in the southern sea area of Hokkaido,Japan

Hydrographic data and composite current velocity data (ADCP and GEK) were used to examine the seasonal variations of upper-ocean flow in the southern sea area of Hokkaido, which includes the “off-Doto” and “Hidaka Bay” areas separated by Cape Erimo. During the heating season (April–September), the outflow of the Tsugaru Warm Current (TWC) from the Tsugaru Strait first extends north-eastward, and then one branch of TWC turns to the west along the shelf slope after it approaches the Hidaka Shelf. The main flow of TWC evolves continuously, extending eastward as far as the area off Cape Erimo. In the late cooling season (January–March), part of the Oyashio enters Hidaka Bay along the shallower part of the shelf slope through the area off Cape Erimo, replacing almost all of the TWC water, and hence the TWC devolves. It is suggested that the bottom-controlled barotropic flow of the Oyashio, which may be caused by the small density difference between the Oyashio and the TWC waters and the southward migration of main front of TWC, permits the Oyashio water to intrude along the Hidaka shelf slope.     

Characteristics of photosynthetic pigment composition ofGymnodinium mikimotoi Miyake etKominami exOda

Gymnodinium mikimotoi, a senior synonym ofGymnodinium nagasakiense often causes red tides in coastal waters of the western part of Japan. The photosynthetic pigment composition of two strains ofG. mikimotoi were analyzed by HPLC. They contain chlorophyllc ₃ which has not been reported from dinoflagellates. They also contain fucoxanthin, 19'-hexanoyloxyfucoxanthin and 19'-butanoyloxyfucoxanthin as major carotenoides, which are anomalous in dinoflagellates. The pigment composition ofG. mikimotoi is compared with that ofGyrodinium aureolum which occur in European waters and is thought as a conspecific species withG. mikimotoi by several authors.