Ecophenotypic responses of benthic foraminifera to oxygen availability along an oxygen gradient in the California Borderland

Spatial variation in environmental conditions can elicit predictable size and morphological responses in marine organisms through influences on physiology. Thus, spatial and temporal variation in marine organism size and shape are often used to infer paleoenvironmental conditions, such as dissolved oxygen concentrations. Benthic foraminifera commonly serve as a tool for reconstructing past ocean oxygen levels. For example, benthic foraminiferal species assemblages, within‐ and among‐species patterns of test morphology, and geochemical analyses of carbonate tests are often employed to reconstruct past marine conditions. In this study, we measured the sizes and shapes of modern foraminifera representing four species that inhabit a steep oxygen gradient in the Santa Monica Basin on the Southern California Borderland with the aim of quantifying the influence of oxygen availability on foraminiferal morphology, both within and among species. Most foraminifera rely on aerobic respiration, but the four benthic foraminifera from the Santa Monica Basin do not show the predicted size and morphological responses to variations in dissolved oxygen concentrations based on first principles of cell physiology: Bolivina spissa shows no volume or volume‐to‐surface area response, Uvigerina peregrina increases in both test volume and volume‐to‐surface area ratio with decreasing dissolved oxygen concentrations, and both Bolivina argentea and Loxostomum pseudobeyrichi decrease in test volume, but only L. pseudobeyrichi shows a decrease in test volume‐to‐surface area ratio with decreasing oxygen concentrations as expected from physiological predictions. These findings imply that the morphological responses of individual foraminiferal species are not necessarily representative of the responses of other foraminiferal species within the community. Our findings further suggest that these species use physiological strategies such as depressed metabolic rates and alternative energy metabolisms to persist in low oxygen environments and, therefore, cannot be used in any simple way as paleo‐oxygen indicators. Should Proterozoic (1,000–542 million years ago) protists have possessed metabolic strategies similar to foraminifera, the sizes and shapes of protists in the fossil record may not usefully constrain ambient oxygen conditions during the appearance and initial taxonomic radiation of heterotrophic eukaryotes.     

Stable isotopes in deep-sea living (stained) foraminifera from the Mozambique Channel (eastern Africa): multispecies signatures and paleoenvironmental application

Oxygen and carbon isotopes (δ¹⁸O and δ¹³C) have been investigated in carbonate tests of deep-sea foraminifera living in the Mozambique Channel (eastern Africa) to understand how environmental constraints (e.g., organic matter, oxygenation) control the intra- and interspecific variability of isotopic signatures. 197 living individuals, including eight different species, from various microhabitats within the sediment were sorted from sediment samples gathered at two stations on the Malagasy upper slope. Results show that the δ¹⁸O values of foraminiferal taxa were not controlled by microhabitat pattern. They presented tremendous and intriguing intraspecific variability that is not explained by the classical ontogenetic effect. The δ¹³C values of infaunal foraminiferal taxa do not show a 1:1 relationship with the bottom water δ¹³C DIC and do not present a constant offset from it; instead, they appear to be mainly controlled by a microhabitat effect. The lower δ¹³C values of shallow, intermediate, and deep infaunal taxa at the deeper station compared to those seen at the shallower station reflect the enhanced exportation of sedimentary organic matter at the sediment–water interface, and its related mineralization within the upper sediments. The ?δ¹³C between shallow/very shallow infaunal species (i.e., Hoeglundina elegans, Uvigerina hispida) and intermediate/deep infaunal species (i.e., Melonis barleeanus, Globobulimina barbata) permits insight into (1) the exportation of organic matter to the seafloor and (2) the various degradation pathways for organic detritus in the benthic environments off NW Madagascar.     

Study on the chemical forms of radionuclides in seawater—I

The stability constants for sulfate, chloride and hydroxide ions with cerium (III) in the solution at ionic strength of 0.67 have been determined by cation exchange method, the values of ₁ and ₂ for sulfate complexes of cerium being 40±13 and 453±140, respectively and those for chloride complexes being 1.28±0.23 and 0.56±0.076, respectively. The values of ₁, ₂ and ₃ for hydroxide complexes of cerium were (4.5±0.9)×10⁷, (3.3±0.7)×10¹⁴ and (1.8±0.7)×10²³, respectively.Using the above constants the ratios of individual chemical species of¹⁴⁴Ce were calculated in a solution at ionic strength of 0.67 containing sulfate and chloride ions approximately the same as in seawater of 35 %. The result of calculation indicates that the dominant species of¹⁴⁴Ce in this solution is Ce(OH)₃ ⁰ at pH 8.     

Sedimentary labile organic carbon and pore water redox control on species distribution of benthic foraminifera: A case study from Lisbon-Setúbal Canyon (southern Portugal)

Rose Bengal stained benthic foraminifera were studied from 11 cores collected along two depth transects off southern Portugal: one in the Lisbon-Setúbal Canyon and the other along the canyon edge. The total standing stocks and distribution of foraminifera were investigated in relation to sediment and pore water geochemistry. Nitrate was used as a redox indicator, sedimentary chlorophyll a and CPE (chloroplastic pigment equivalents) contents as a measure of labile organic matter, and total organic carbon as a measure of bulk organic matter availability.The canyon sediments were enriched in organic carbon and phytopigments at all water depths in comparison with the canyon edge. Water depth seemed to control sedimentary phytopigment content, but not total organic carbon. No significant correlation was seen between pigment and total organic carbon content.The abundance of calcareous foraminifera correlated with the phytodetritus content, whereas a weaker correlation was observed for the agglutinated taxa. Therefore, calcareous foraminifera appear to require a fresher food input than agglutinated taxa. The foraminiferal species composition also varied with pigment content and nitrate penetration depth in the sediment, in line with the TROX concept. Phytopigment-rich (surficial CPE content >20 μg/cm³) sediments with a shallow nitrate penetration depth (∼1 cm depth) were inhabited by generally infaunal species such as Chilostomella oolina, Melonis barleeanus and Globobulimina spp. As the nitrate penetration increased to ∼2 cm depth in sediment and the pigment content remained relatively high (>15 μg/cm³), Uvigerina mediterranea and Uvigerina elongatastriata became dominant species. With declining CPE content and increasing nitrate penetration depth, the foraminiferal assemblages changed from the mesotrophic Cibicides kullenbergi-Uvigerina peregrina assemblage to the oligotrophic abyssal assemblage, mainly consisting of agglutinated taxa.     

Geochemistry of gas hydrate accumulation offshore NE Sakhalin Island (the Sea of Okhotsk): results from the KOMEX-2002 cruise

Geochemical properties of gas hydrate accumulation associated with an active gas vent on the continental slope offshore northeast Sakhalin Island in the Sea of Okhotsk have been investigated. The pore water chemistry data suggest that the gas hydrates (GHs) were formed in an environment of upward-migrating fluid combined with a mechanism of pore water segregation. The upward infiltration of water enriched mainly by Cl^– and K⁺ species appears to occur on the background of earlier diagenesis processes within the gas vent sediments. The GHs were formed from water with chlorinity ranging from 530 to 570 mM. The ¹⁸O and D of GH water varied from –1.4 to –1.8 and from –13 to –18, respectively, representing a mix of seawater and infiltrating fluid water. A complex interaction of pore water, water of ascending fluid and segregated pore water during hydrate formation is also supported by water content measurements and observed gas hydrate structure. The direction of segregated water is opposite to upward fluid migration. Decreasing activity of the gas vent is inferred by comparing the present top of the recovered hydrate layer with previous observations.     

Influence of the hydrothermal vents on the distribution of benthic foraminifera from the Guaymas Basin,Mexico

The distribution and composition of four benthic foraminifera assemblages from the Guaymas Basin are depicted through Q- and R-mode Factor Analysis. One of these assemblages is distributed near hydrothermal vents,* another developed away from the influence of the vents, and the other two assemblages are found in the subbottom sediments.Biostratigraphic analysis of five cores collected within the hydrothermal region suggest that the foraminiferal remains have been affected by aselective dissolution process. Only small species, such asBulimina spinosa andBolivina sp 2, have been preserved in the subbottom sediments which have been influenced by the hydrothermal activity.     

Glacial to Holoceneδ 13C variations in intermediate depth water masses of North Indian Ocean

The ¹⁸O and ¹³C compositions of glacial- to Holocene-aged benthic foraminifera in a core collected from the eastern Arabian sea (water depth 1230 m) were determined to investigate glacial—interglacial variations in the intermediate depth water chemistry of the North Indian Ocean. In addition, we determined the ¹³C composition of Holocene benthic foraminifera from seven cores for which the ¹⁸O and ¹³C of benthic foraminifera from last glacial maximum (LGM) were reported by Kallel et al. (1988). The ¹³C_DIC in the intermediate waters was generally depleted by 0.3–0.4 during the last glacial maximum compared to Holocene.     

Field data support of three-seconds power law andgu *σ−4-spectral form for growing wind waves

Observational data on air-sea boundary processes at the Shirahama Oceanographic Tower Station, Kyoto University, obtained in November, 1969, was analyzed and presented as an example representing the structure of growing wind-wave field. The condition was an ideal onshore wind, and the data contained continuous records of the wind speed at four heights, the wind direction, the air and water temperatures, the tides, and the growing wind waves, for more than six hours. The main results are as follows. Firstly, in both of the wind speed and the sea surface wind stress, rather conspicuous variations of about six-minute period were appreciable. Secondly, the three-seconds power law and its lemma expressed byH ^*=BT ^*3/2 and=2BT ^*–1/2, respectively, are very well supported by the data, whereH ^*(gH/u _* ²) andT ^*(gT/u _*) are the dimensionless significant wave height and period, respectively, the wave steepness,u _* the friction velocity of air,g the acceleration of gravity, andB=0.062 is a universal constant. Thirdly, the spectral form for the high-frequency side of the spectral maximum is well expressed by the form of()= _sgu_*^–4, where is the angular frequency and() the spectral density. The value of _s is determined as 0.062±0.010 from the observational data. There is a conspicuous discrepancy between the spectral shape of wind waves obtained in wind-wave tunnels and those in the sea, the former containing well-defined higher harmonics of the spectral peak, and consequently there is an apparent difference in the values of _s also. However, it is shown that the discrepancy of _s may be eliminated by evaluating properly the energy level of the spectral form containing higher harmonics.     

Diversity patterns in macrobenthos across a continental slope in the NE Atlantic

Different estimates were used to assess the diversity of the total macrofauna and its major taxonomic groups separately from a broad bathymetric range at a site in the NE Atlantic. In the Goban Spur region, a transect was sampled from the shelf to the abyssal plain over a depth range from 200 to 4500 m and in the Porcupine Sea Bight two stations were sampled (at 3670 m and 4115 m). Species diversity (the number of species per number of individuals) increased with increasing water depth, both when expressed as Hurlbert's E(S_n) and as Shannon's H′log e. The expected number of species in a 100-individual sample E(S₁₀₀) of total macrofauna increased from 30 on the shelf to 68 on the abyssal plain. Evenness (the proportional abundance of species), estimated with Shannon's J′, also increased with water depth from 0.66 to 0.91, whereas dominance (Simpson's D) decreased from 0.09 to 0.01. Species richness (the number of species per unit of area), however, showed a parabolic pattern with a peak at the upper slope. The largest number of species was found at the slope station at 1425 m (232 species within 0.66 m²). It is argued that species richness is not a synonym of species diversity, but that species richness depends both on species density (which decreases with increasing water depth) and on species diversity. Across the whole bathymetric range (200 to 4500 m) a total of 696 species within 8327 specimens in a total sampled area of 4.12 m² were counted, yielding mean values of 12 individuals per species and 169 species per m². Different communities were found to exist on the shelf, slope and abyss. It is suggested that this could have been caused by different selection processes. Differences in life-history strategies and organic-matter supply could (at least partly) explain the different community structures and diversity patterns found along the depth gradient.     

On the relation between the growth rate of water waves and wind speed

Various wind velocitiesu _*,U _/2,U andU ₁₀ are correlated to the measured growth rate of water waves , whereu _* is the friction velocity of the wind, andU _/2,U andU ₁₀ are the wind speeds respectively at the heights /2, and 10m above sea surface (: wave length). It is shown that within a range of the dimensionless wind speed, 0.1<u _* /C<0.6, there are no appreciable differences in the correlations, whereC is the phase velocity of water waves. The present relation between andU shows qualitatively similar properties as the one obtained by Al'Zanaidi and Hui (1984); the growth rate for waves with rough surface is larger than that with smooth surface. However, our present relations give, for the both waves with different surface roughness, larger values by factors 1.71.8 than those given by Al'Zanaidi and Hui's relation.     

The mechanism of the development of wind-wave spectra

The mechanism of the development of wind-waves will be proposed on the basis of the observed wave spectra in the wind tunnels and at Lake Biwa (Imasato, 1976). It consists of two aspects: One is that the air flow over the wind-waves transfers momentum concentratively to the steepest component waves and the other is that the upper limit of the growth of a wave spectral density is given by the ultimate value in the slope spectral density. The first aspect means that the wave field has the momentum transfer filter on receiving the momentum from the air flow. Wind-waves in the stage of sea-waves receive the necessary amount of momentum by the form drag,e.g. according to the Miles' (1960) inviscid mechanism, through a very narrow frequency region around a dominant spectral peak. On the other hand, wind-waves in the stage of initial-wavelets receive it according to the Miles' (1962a) viscous model through a fairly broad frequency region around the peak. The upper limit ofS _max developing according to viscous mechanism is given byS _max =6.40×10^–4 k _max ^–2cm²s andS _max =2.03C(f _max )^–2cm²s(S _max is the power density of the wave spectral peak with the frequencyf _max ,k _max is the wave number corresponding to the frequencyf _max andC is the phase velocity).From the second aspect, the upper limit of the growth of wave spectral density is given by 33.3f ^–4cm²s in the frequency region of late stage of sea-waves. Therefore, the spectral peak, which has the largest value in the slope spectral density in the component waves of the wave spectrum, rises high over the line 4.15f ^–5cm²s. The energy is transported from the spectral peak to the high frequency part and to the forward face of a wave spectrum by nonlinear wave-wave interaction. This nonlinearity is confirmed by the bispectra calculated from the observed wind-wave data. In the stage of sea-waves, nonlinear rearrangement of the wave energy comes from a narrow momentum transfer filter, and, in the stage of initial-wavelets, it comes mainly from small corrugations and small steepness of the wave field.     

Contents of strontinm-90 and ruthenium-106 in beach and shallow water deposits of noto peninsula

⁹⁰Sr,¹⁰⁶Ru, natural strontium and major elements were studied in 12 samples of beach deposits from Togi, Fukuura and Shiga, and in 26 samples of shallow water sediments from sea off Fukuura, Noto Peninsula, Ishikawa Pref., Japan.The average contents of natural strontium and⁹⁰Sr in the beach deposits were 488 ppm ranging from 247 to 1,550 ppm and 45±9 pCi kg^–1-dry mud ranging from 18 to 72 pCi kg^–1-dry mud, respectively. While the average contents of natural strontium,⁹⁰Sr and¹⁰⁶Ru in the sediments were 234 ppm ranging from 136 to 415 ppm, 22±6 pCi kg^–1-dry sand ranging from 7 to 48 pCi kg^–1-dry sand and 0.6 ±0.2 nCi kg^–1-dry ranging from 0.3 to 1.2 nCi kg^–1-dry, respectively.The average contents of each natural strontium and⁹⁰Sr in the beach deposits were about two times higher than those in the shallow water sediments. But no obvious relation of natural strontium to⁹⁰Sr was found in all the samples. The enrichment of⁹⁰Sr and¹⁰⁸Ru in the beach deposits or tthe sediments were as high as 150320 and of 2,0003,000 compared with average contents of⁹⁰Sr and¹⁰⁶Ru in a liter of surface water from the Japan Sea. It is to be noticed that the average¹⁰⁶Ru to⁹⁰Sr ratio of 27 for the shallow water sediments is much higher than the average of 1.0 for surface sea water of the Japan Sea.As to major elements of the samples, the beach deposits are rich in silicon (Av. 70.89 ±0.92% SiO₂), but poor in iron (Av. 2.99±0.32% Fe₂O₃). Whereas the shallow water sediments are poor in silicon (Av. 52.96±10.33% SiO₂) and rich in iron (Av. 5.50±1.90% Fe₂O₃), calcium (Av. 9.64±9.22% CaO) and magnesium (Av. 2.83±1.58% MgO).     

Benthic foraminifera living in Gulf of Mexico bathyal and abyssal sediments: Community analysis and comparison to metazoan meiofaunal biomass and density

Benthic foraminiferal biomass, density, and species composition were determined at 10 sites in the Gulf of Mexico. During June 2001 and 2002, sediment samples were collected with a GoMex box corer. A 7.5-cm diameter subcore was taken from a box core collected at each site and sliced into 1-cm or 2-cm sections to a depth of 2 or 3 cm; the >63-μm fraction was examined shipboard for benthic foraminifera. Individual foraminifers were extracted for adenosine triphosphate (ATP) using a luciferin–luciferase assay, which indicated the total ATP content per specimen; that data was converted to organic carbon. Foraminiferal biomass and density varied substantially (2–53 mg C m⁻²; 3600–44,500 individuals m⁻², respectively) and inconsistently with water depth: although two 1000-m deep sites were geographically separated by only 75 km, the foraminiferal biomass at one site was relatively low (9 mg C m⁻²) while the other site had the highest foraminiferal biomass (53 mg C m⁻²). Although most samples from Sigsbee Plain (>3000 m) had low biomass, one Sigsbee site had >20 mg foraminiferal C m⁻². The foraminiferal community from all sites (i.e. bathyal and abyssal locales) was dominated by agglutinated, rather than calcareous or tectinous, species. Foraminiferal density never exceeded that of metazoan meiofauna at any site. Foraminiferal biomass, however, exceeded metazoan meiofaunal biomass at 5 of the 10 sites, indicating that foraminifera constitute a major component of the Gulf's deep-water meiofaunal biomass.     

Regional primary productivity differences off Morocco (NW-Africa) recorded by modern benthic foraminifera and their stable carbon isotopic composition

The influence of different primary productivity regimes on live (Rose Bengal stained) and dead benthic foraminiferal distribution, as well as on the stable carbon isotopic composition of foraminiferal tests, was investigated in sediment surface samples (0–1 cm) from the upwelling region off Morocco between Cape Ghir (31°N) and Cape Yubi (27°N). A combination of factor analysis, detrended correspondence analysis (DCA) and canonical correspondence analysis (CCA) was applied to the benthic foraminiferal data sets. Five major assemblages for both the live and dead fauna were revealed by factor analysis. In the cape regions organic matter fluxes are enhanced by high chlorophyll-α concentrations in the overlying surface waters. Here, benthic foraminiferal faunas are characterized by identical live and dead assemblages, high standing stocks, and low species δ¹³C values, indicating constant year-round high productivity. Bulimina marginata dominates the unique fauna at the shallowest station off Cape Ghir indicating highest chlorophyll-a concentrations. Off both capes, the succession of the Bulimina aculeata/Uvigerina mediterranea assemblage, the Sphaeroidina bulloides/Gavelinopsis translucens assemblage, and the Hoeglundina elegans assemblage from the shelf to the deep sea reflects the decrease in chlorophyll-a concentrations, hence the export flux. In contrast, the area between the capes is characterized by differently composed live and dead assemblages, low standing stocks, and less depleted δ¹³C values, thus reflecting low primary productivity. High foraminiferal numbers of Epistominella exigua, Eponides pusillus, and Globocassidulina subglobosa in the dead fauna indicate a seasonally varying primary productivity signal. Significantly lower mean δ¹³C values were recorded in Bulimina mexicana, Cibicidoides kullenbergi, H. elegans, U. mediterranea and Uvigerina peregrina. Cibicidoides wuellerstorfi is a faithful recorder of bottom water δ¹³C in the Canary Islands regions. The mean δ¹³C signal of this species is not significantly influenced by constant high organic matter fluxes. The species-specific offset between live and dead specimens is the same.     

Studies on the red tide flagellates—VI

Extensive bloom of red tide, accompanying mass mortality of fish and the other animals, occurred in Bingo-Nada, the Seto Inland Sea, in August, 1970. Two species of microorganisms,Eutreptiella sp. andExuviaella sp., were isolated from the water and were obtained in axenic culture by micropipette washings.These organisms are stimulated by trace metals. The highest growth resulted from the addition of chelated Fe (<3 mg/l) or/and Mn (<2 mg/l) to enriched sea water. The organisms prefer low salinity. The optimal salinities are Cl 8.0–17.0 forEutreptiella sp., Cl >11.0 forExuviaella sp. respectively. These organisms can tolerate a wide range of pH.Exuviaella sp. needs vitamin B₁₂ for growth. The pattern of specificity toward B₁₂ analogues²⁾ is similar to that ofEuglena gracilis. On the other hand,Eutreptiella sp. requires B₁₂, biotin, and thiamine. The B₁₂ specificity fits toEscherichia coli. Both organisms prefer NH₄-N in lower concentrations than 1 mg/l (optimal 0.3 mg/l) as nitrogen sources.Exuviaella sp. also likes urea. Inorganic and organic phosphates are utilized by the organisms:Eutreptiella sp. utilizes Na₂-glycerophosphate, guanylic acid,Exuviaella sp. utilizes Na₂-glycerophosphate, adenylic acid. KH₂PO₄ is the most favorable to the growth of both organisms. All the purines, pyrimidines, plant hormones tested increase the growth ofExuviaella sp. Especially, guanine, xanthine, thymine, indoleacetic acid, and gibberellic acid promote the growth remarkably.These organisms do not grow to high densities without Fe or/and Mn in high concentrations even under the conditions provided by optimal temperature, salinities, pH, and essential nutrients. On the other hand, the coastal area of Fukuyama where the red tide first occurred has been fertilized with the nutrients essential to the organisms, and also polluted with trace metals such as Fe (Iwasaki, Inoue unpublished data). From these results, it can be considered that the great increase of the organisms is caused principally by the high concentration of iron in the sea water.     

Bispectra of spike-array type time series and their application to the analysis of oceanic microstructures

Bispectral analysis is applied to records of the vertical profile of the vertical temperature gradient in the oceanic thermocline in the San Diego Trough. The bispectra exhibit three notable features; (1) bispectral peaks at the points (0.2 m^–1, 0.2 m^–1) and (0.2 m^–1, 0.1 m^–1), (2) bispectral ridges along the lines ( ₁= ₀, ₂= ₀ and ₁+ ₂= ₀ corresponding to peak wavenumbers ₀ in power spectra, and (3) array of bispectral peaks of interval of 0.2 m^–1 The results are compared with the bispectra of several modeled time series of spike-array type. The periodicity of 5 m found in the records seems to have two meanings: spacing of predominant spikes and wavelength of predominant sinusoidal wave. If this indicates the existence of internal waves having a vertical wavelength the same as the scale of homogeneous layers, it would suggest the possible importance of internal waves in the formation and maintenance mechanisms of oceanic microstructure.     

The separation of flow past a circular cylinder on aβ-plane

Effects of the Ekman friction on the prograde (eastward) flows past a cylinder on a-plane are investigated when (=R ²/U, whereR is the cylinder radius andU the freestream speed)O(1) and(=2E _k ^1/2/R ₀·O(1) where is the non-dimensional beta parameter and the ratio of the square root of the Ekman numberE _k multiplied by 2 to the Rossby numberRo multiplied by the aspect ratio(=H/R, whereH is the fluid depth). Previous studies without the Ekman friction have shown that the-effect inhibits flow separation for pragrade flows through the asymptotic boundary condition by shifting the region of the adverse pressure gradient toward the rear stagnation point. It is found that the Ekman friction alleviates this-effect on the exterior flow. In the E_k ^1/4-boundary layer, on the other hand, Ekman friction suppresses the vorticity advection along the wall, which tends to make the boundary layer thickness thin and delay the flow separation. The Ekman friction thus affects flow separation in a complicated manner. Details of the boundary layer structures and the separation angles are described for 0.3< <4.0 and 0.1<<1.5.     

On nondimensional correlation between roughness length and wind-friction velocity

Physical bases for nondimensional parameters,z ₀/(u ² _*/g) andz ₀/(u _*/), characterizing wind-wave interaction are discussed; data selected to support the latter are critically reviewed. Both parameters are herewith unified, with the former describing the primary growth of roughness length with wind and the latter the secondary effects due to waves.     

Scale dependence of accumulation-dispersal coefficient of marine organisms

An attempt is made to find a relation betweenK, the absolute value of accumulation-dispersal coefficient of marine organisms referred to a region or a group (Kawai, 1986a), andL, the square root of the area of the region or the group over which the distribution density of organisms is averaged.K is estimated as shown below. For appropriate sampling time-intervals,K becomes greater than other coefficients such as population growth coefficient. Using this result, an order of magnitude ofK dependent onL is estimated from various data of temporal change in density. With the aid of a dependenceQL ^–2/3 (Kawai, 1985b), a relationKL ^–2/3 is predicted for 30 cmL 30 km, whereQ andK are the root-mean-square values of area-averaged horizontal divergence of near-surface flows and of the accumulation-dispersal coefficient, respectively. The reason whyK tends to have the order of magnitude of weak or mediumQ is discussed. The doubling-halving time of the distribution density due to accumulation-dispersal,T, is related toK byT=(log_e2)/¦K¦L ^2/3. Finally, sampling time-intervals to estimate accumulation-dispersal coefficients are referred to.     

Radiation balance and heat budget at the ocean/atmosphere interface in the western North Pacific

The downward short- and long-wave radiation fluxes at the sea surface (S, L) were measured aboard the R/VHakuho Maru, University of Tokyo, for the period of 117 days on six cruises from 1981 to 1985 in the western North Pacific near Japan. The upward fluxes of short- and long-wave radiation (S, L) were calculated by Payne's (1972) table and the Stefan-Boltzmann's law, respectively. The sensible and laten heat fluxes (Q _h ,Q _e ) were also estimated from an aerodynamic bulk method.From April to August, the daily mean value ofS varied with the amplitude of 100200 Wm^–2. The value ofS was estimated approximately 6% ofS in all seasons. The difference betweenL andL was so small that the net radiation flux (Q _n ) was dominated byS. In addition, the net heat flux at the sea surface was also dominated byS due to small values ofQ _h andQ _e , and then the ocean was warmed at the rate of 111 Wm^–2 in April and 63 Wm^–2 in August in the Oyashio Area, and 132 Wm^–2 in May and 164 Wm^–2 in June in the Kuroshio Area, respectively.From September to March, a remarkable negative correlation between the day to day variation ofS and that ofL was observed except when an intense cold air outbreak occurred. It was found that the correlation was caused by the cloud climatological feature of the western North Pacific in this period.S was not a dominant factor in the net heat flux. The value ofQ _h +Q _e in the Kuroshio Area ranged from 260 Wm^–2 to 630 Wm^–2, much larger thanQ _n which ranged from –8 Wm^–2 to 92 Wm^–2 in the leg mean values (each leg period was about 10 days). Then the ocean was cooled at the rate of –160–620 Wm^–2 during this period. The net heat flux in the Kuroshio Area averaged over five legs from late November to February was –473 Wm^–2. This value is 50100% larger than the climatological values reported so far.The temporal and spatial variability of radiation fluxes and heat fluxes during each leg was also discussed.