Showing papers by "Woods Hole Oceanographic Institution published in 1976"

Computations of Surface Energy Flux and Annual Air–Sea Interaction Cycles of the North Atlantic Ocean

Abstract: Energy fluxes through the surface of the North Atlantic Ocean have been calculated using bulk aerodynamic equations with exchange coefficients which vary with wind speed and stability, and radiation equations. Values of the coefficients were determined from published results of many experiments made at sea, coastal installations and in laboratories. Eight million ship weather reports were used for flux calculations. Reliabilities of monthly meteorological and flux averages are found to be good in areas having SW or move observations per average. A chart of the net annual heat gain by the ocean shows regions with characteristic gains or losses such as the Gulf Stream, Norwegian Sea, Labrador Current, trade winds and upwelling areas. Annual cycles of fluxes, winds, temperatures, clouds and rainfall in eight regions are presented and discussed from the point of view of predominating air–sea interaction processes. Contributions of meteorological variables, oceanic currents, atmospheric circulations a...

Alkalinity changes generated by phytoplankton growth1

Abstract: Continuous cultures of three marine phytoplankton species, Phaeodactylum tricornutum, Dunaliella tertiolecta, and Monochrysis lutheri, were monitored for changes in alkalinity of the culture medium resulting From NO, and NHa+ uptake. Uptake of NO,caused an increase in alkalinity, whereas uptake of NH,+ produced a decrease. These results are consistent with the type of schematic equation proposed by Redfield, Ketchum, and Richards for photosynthetic assimilation of inorganic nitrogen, in which NO, uptake is balanced by OHproduction and NHa+ uptake leads to H+ generation. These reactions suggest active uptake of nitrogen species by microbes. We have been unable to demonstrate the exact stoichiometry of this relationship, and the role of P uptake in the alkalinity change is unclear. An offset in the data, functionally equivalent to the production of some strong acid, may be due to reactions on the walls of the vessel, active uptake of cations, or extrusion of H’ ions by the growing cells. An understanding of the oceanic CO2 system is important in many branches of marine chemistry and biolo,gy. Experimentally, this may be approached through measurement of any two of the four variablcs pH, alkalinity, pCOa, and total COz, and from any two of these properties the others can be calculated (Skirrow 1965). Many recent data have been obtained by the potentiometric titration technique ( Dyrsscn 1965; Edmond 1970) that enables the alkalinity and total COz to be measured in a single sample. The alkalinity of scawater is defined as the number of equivalents of strong acid required to titrate 1 liter of seawater to the C02-HC03end point. Analytically, this is equivalent to the sum of the concentrations of the anions of carbonic and other weaker acids. Alkalinity is thus inherently associated with charge balance ( Stumm and Morgan 1970), and the addition or removal of neutral CO2 during respiration or photosynthesis has no cffcct on this property. All this is frequently taken to mean that the photosynthetic or decomposition processes occurring in aquatic environments do not generate alkalinity changes. This is ’ Contribution No. 3595 from the Woods IIole Oceanographic Institution. This research was supported by NSF grants GA-22292 and GX-33295 (P.G.B. ) and ERDA contract AT( 11-l )2532 ( J.C.G. ) . by no means correct. Goldman c t al. (1972) have pointed out that uptake of N03during photosynthesis generates strong base, whereas NH4+ assimilation leads to acid production. Brewer et al. ( 1975) have discussed the reverse effect in which the dccomposition of marine organic matter csscntially leads to the liberation of nitric acid. This strong acid reacts with carbonate ion derived from calcium carbonate dissolution, thus leaving an excess of calcium over that predicted from observed alkalinity changes. These effects have been inferred for many years (Trelease and Trelease 1935; Cramer and Myers 1948; Rcdfield ct al. 1963; Richards 1965; Berner et al. 1970; Gaines and Pilson 1972) and indeed are implicit in the Redficld-Ketchum-Richards phytoplankton equations. Yet, as far as we are aware, these phenomena have not been adequately documented and no cxpcrimental prooE cxis ts. Here, we report our mcasurcmcnts of alkalinity changes during the growth of phytoplankton on both NOaand NI-IJ+ as nitrogen sources. We thank J. M. Edmond and F. Morel for their critical review and R. Smith, S. Kadar, A. Fleer, and R. Carbon for their technical assistance.

Production and dynamics of experimentally enriched salt marsh vegetation: Belowground biomass1

Abstract: Root growth increased during the early growing season in Spartina alterniflora salt marsh plots. While fertilization with nitrogenous fertilizer did not affect initial growth, a marked decrease in root biomass followed the spring peak particularly where nutrient doses were highest. A sharp reduction in roots occurred in enriched areas covered by Spartina patens, although, as with S. alterniflora, aboveground biomass increased. Roots disappeared during autumn leaving rhizomes as the only part of the plants to overwinter. The maximum standing crop for roots was 0–2 cm deep, for rhizomes 2–5 cm. Net annual underground production was calculated from annual increments in dead matter belowground. Total production, underground and aboveground, exceeds that of any marine vegetation, ranging from 3,900 to 6,600 g m‒2 yr‒1 in S. alterniflora areas and 3,200 to 6,200 g m‒2 yr‒1 in S. patens areas. Fertilization increased production particularly aboveground where dead plant parts are subject to export.

A similarity measure sensitive to the contribution of rare species and its use in investigation of variation in marine benthic communities.

Abstract: We propose a new measure of similarity, the normalized expected species shared or NESS. The measure is based on the expected number of species shared between random samples of size, m, drawn from a population. The NESS measure is shown to be a generalization of Morisita's similarity and is demonstrated to be less biased than other commonly used measures. The contribution of dominant and rare species is explicit according to the sample size, m, chosen. For large m, NESS is sensitive to the less common species in the populations to be compared. The NESS measure has been used to cluster a 2-year sequence of subtidal benthic samples taken after a severe disturbance. The NESS measure is responsive to the less common species so that both a temporal progression in community recovery and seasonal variation are revealed.

Production of epibenthic salt marsh algae: Light and nutrient limitation1

Abstract: Epibenthic algal production was measured in Great Sippewissett Marsh, Falmouth, Massachusetts, in plots treated with two levels of a mixed fertilizer and with urea or phosphate. Production, which followed a consistent seasonal pattern with short-lived peaks in spring and fall, was increased by the highest dosage of mixed fertilizer but not by the other treatments. Fertilization also increased production of the marsh grasses. Algal production at the marsh surface was limited due to shading by the grass canopy. The production rate decreased with increasing biomass of the grasses. To separate the effects of light and nutrients in the treated areas, additional small plots were enriched with three levels of nitrogen (suspected as the limiting nutrient) and provided with three levels of canopy cover cross-classified to the nitrogen treatments. Shading by the grasses reduced, while fertilization with nitrogen significantly increased, production. When the grasses were dormant, prediction from a model of epibenthic production based on limitation by light compared well with observed measurements. The predicted production rate was higher than that observed during the growing season of the grasses. In the plots receiving the highest doses of mixed fertilizer the added nutrients comoensated for the light limitation. since the discrepancy between predicted and observed valuis was smaller than in the control plots.

Temperature‐influenced species competition in mass cultures of marine phytoplankton

Abstract: Five marine phytoplankton species (Phaeodactylum tricornutum, Thalassiosira pseudonana, Skeletonema costatum, Monochrysis lutheri, and Dunaliella tertiolecta) were grown in enriched laboratory continuous cultures and natural populations were mass cultured outdoors for 16 months. Competition among the species was shown to be highly dependent on temperature, although the actual production of plant organic matter at the low growth rates used was relatively independent of this variable. Control of marine species in mass cultures does not appear economically feasible, but this drawback may be overcome by selecting herbivorous shellfish that are capable of assimilating those temperature-dependent phytoplankton species dominating in a particular locale.

The feeding rates of the pelagic tunicate Pegea confederata and two other salps1

Abstract: The filtration rates of Pegea confederata, Salpa maxima, and Cyclosalpa a;ffinis were measured. Filtration rates increase exponentially with increasing length and body carbon. Filtration rates exceeding 100 ml min-’ were recorded. The mucous net of P. confederata can retain particles at least as small as 0.7 P. There appears to be no change in filtration rate with changes in particle concentration. Filtration rate per microgram of carbon increases with increasing body weight of salps in contrast to ascidians, perhaps because salps use muscular pumping rather than ciliary currents to transport water. The filtration rates recorded suggest that the role of salps in the open ocean ecosystem may be more important than previously assumed.

Continental Margin Off Western Africa: Senegal to Portugal

Abstract: About 22,000 km of continuous seismic-reflection, magnetic, and gravity profiles, 118 radiosonobuoy recordings, 98,000 km of geophysical profiles from previous investigations, 15 deep-sea-drilling logs, and many dredge samples served to reconstruct the history of the continental margin and adjacent deep-ocean floor between Senegal and Portugal. Initial structures of the margin south of Morocco formed by divergence when Africa and North America separated 180 m.y. ago. The margin off western Portugal had a similar origin when the Iberian Peninsula and North America separated about 80 m.y. ago. Between these two divergent segments the area of the Strait of Gibraltar formed by a combination of translation from 180 to 72 m.y. ago and plate convergence from 63 m.y. ago to the p esent, with convergence becoming more intense during the past 10 m.y. Oldest sedimentary rocks atop basement include an evaporite of Late Triassic to Early Jurassic age. When the apron deposited by upbuilding and outbuilding became thick enough, mobility of the evaporites deformed the overlying sediments especially north of the Canary Islands. Except off Morocco and the Strait of Gibraltar and possibly off southern Senegal the sedimentary blanket is dominantly calcareous, reflecting the general lack of fluvial influx. Included is a middle-Late Jurassic algal reef that constitutes the lower continental slope off Morocco. During Aptian-Cenomanian time the deep ocean off much of northwestern Africa had only sluggish bottom circulation, recorded by organic-rich sediments. A major hiatus in deep-ocean sedimentary rocks and in three prominent sedimentary ridges (off Madeira, near Agadir canyon, and north of Conception bank) probably was caused by temporarily intensified circulation. Tertiary tectonics modified the divergent margin south of Morocco by folding of shelf strata off the western High Atlas, emplacement of the Canary Island Ridge, folding of slope strata off Spanish Sahara, and uplift of the Cape Verde plateau. These orogenies also may have uplifted oceanic basement beneath the upper rise and formed the volcanic seamounts along this ridge. Maximum modification by Tertiary diastrophism occurred on the margin of translation-convergence near the Strait of Gibraltar. There, the convergence phase caused uplift of Gorringe bank. Plate convergence also deformed sediments atop oceanic basement, aided by the mobility of Triassic-Jurassic evaporites. More recently, probably because of uplift of the Iberian Peninsula during the Pliocene, well-stratified Miocene and younger deposits atop the deformed lower unit slid oceanward away from the peninsula, with the megaslide coming to rest against the Moroccan continental slope. Associated folding also involved the lower deformed sequence.

Climatological Numerical Models of the Surface Mixed Layer of the Ocean

Abstract: Three slab models of the surface mixed layer of the ocean are given simple and fast computer implementations. Actual meteorological data from Ocean Weather Station N are used for a year-long forecast. The results compare quite well with the observations of vertical temperature profiles, with correlations up to 0.98 between predicted and observed sea-surface temperature and of 0.8 between predicted and observed mixed-layer depths. Temperature anomalies introduced in the spring can be covered up in the summer, yet reappear in the winter. A constant-thickness slab is suitable as a lower boundary for some atmospheric climatological studies, if a depth of 25 m is used. The model based on a Foude number criterion worked best for the available data set; this is physically appealing since the model contains no adjustable parameters.

Kinetics of silicic acid uptake and rates of silica dissolution in the marine diatom thalassiosira pseudonana1,2

Abstract: SUMMARY Tracer techniques using the stable isotope 30Si were used to measure rates of silicic acid uptake and silica dissolution in silicon replete and silicon depleted populations of 2 clones of the marine diatom Thalassiosira pseudonana Hasle & Heimdal. Uptake kinetics were describable using the Michaelis-Menten equation for enzyme kinetics, and no threshold concentration for uptake was evident. The maximum specific uptake rate of the estuarine clone 3H (0.062–0.092 · h−1) was higher than that of the Sargasso Sea clone 13-1 (0.028–0.031 · h−1), but half-saturation constants for uptake by the 2 clones were not measurably different (0.8–2.3 μM for 3H; 1.4–1.5 μM for 13-1). There was little or no light dependence of uptake in populations grown under optimal light conditions prior to the experiment. Exponentially growing populations released silicic acid to the medium by dissolution of cellular silica at rates ranging from 6.5 to 15% of the maximum uptake rate.

Observations on the Vertical Polarization and Energy Flux of Near-Inertial Waves

Abstract: Vertical profiles of horizontal ocean currents are used to study the vertical structure and temporal behavior of internal waves in the ocean, particularly those near the local inertial frequency. The polarization, or direction in which the horizontal velocity vector of an internal wave rotates with depth, is an important feature of the vertical structure, since it provides information on the direction and magnitude of the vertical wave energy flux. Analysis of a time series of profiles at one location over smooth topography shows that the observed wave polarization and phase propagation in the vertical are consistent, at least within the limits of the observational technique that was employed, with the linear dispersion relation for internal waves. The fact that the waves are polarized in the clockwise sense with increasing pressure shows that they have a net downward energy flux. A spectral decomposition of the profiles into clockwise and anti-clockwise components provides an estimate of 0.2–0.4...

Microsomal mixed function oxidases in an estuarine fish, Fundulus heteroclitus, and their induction as a result of environmental contamination.

Abstract: 1. 1. An hepatic microsomal mixed function oxidase (MFO) system is described in the estuarine fish, Fundulus heteroclitus . 2. 2. In vitro aldrin ∗ epoxidation rates were measured and compared to those seen in freshwater fish. 3. 3. The oxidases are microsomal, require NADPH, † and were poisoned by carbon monoxide (CO) indicating the involvement of a CO-binding component. 4. 4. Liver microsomal preparations contained the CO-binding cytochrome P-450. 5. 5. High levels of these enzymes were induced both by a drug in the laboratory and by contamination of the aquatic environment by foreign hydrocarbons.

Volcanic rocks and processes of the Mid-Atlantic Ridge rift valley near 36 ° 49′ N

Abstract: Eighty samples of submarine basaltic lava were sampled from an 8 km segment of the floor and walls of the inner rift valley of the Mid-Atlantic Ridge during the French American Mid-Ocean Undersea Study (project Famous). The samples were collected from outcrops and talus slopes by the three submersibles: Alvin, Archimede, and Cyana at water depths of about 2600 meters. The early formed mineral content of the pillow lavas' glassy margins enables classification of the rocks into 5 types: (1) olivine basalt, (2) picritic basalt, (3) plagioclase-olivine-pyroxene basalt, (4) aphyric basalt, and (5) plagioclase-rich basalt. Chemical and mineralogical study indicates that at least 4 types are directly interrelated and that types (1) and (2) are higher-temperature, primitive lavas, and types (3) and (4) are lower-temperature, differentiated lavas derived from the primitive ones by crystal-liquid differentiation. The plagioclase-rich basalts also have a chemical composition of their glass comparable to that of the most differentiated basalts (types 3 and 4) but they differ in their greater amount of early formed plagioclase (12–35%). In general, the mineralogical variation across the rift valley shows an assymetrical distribution of the major basalt types. Despite the mineralogical diversity of the early formed crystals, the chemistry of the basalt glasses indicates a symmetrical and a gradual compositional change across the rift valley. Based primarily on their chemistry, the rock types 1 and 2 occupy an axial zone 1.1 km wide and make up the central volcanic hills. Differentiated lavas (types 3, 4) occupy the margins and walls of the inner rift valley and also occur near the center of the rift valley between the central hills. FeO/MgO ratios of olivine and coexisting melt indicate that the average temperature of eruption was 40 ° C higher for the primitive melts (types 1 and 2). Aside from major elements trends, the higher temperature character of the primitive basalts is shown by their common content of chrome spinel. The thickness of manganese oxide and palagonite on glassy lava provide an estimate of age. In a general fashion the relative age of the various volcanic events follow the compositional zoning observed in the explored area. Most of the youngest samples are olivine basalt of the axial hills. Most older samples occur in the margins of the rift valley (West and N.E. part of explored area) but are significantly younger than the spreading age of the crust on which they are erupted. Intermediate lava types occur mainly east of the rift valley axis and in other areas where plagioclase—olivine—pyroxene basalt and aphyric basalt are present. The above relations indicate that the diverse lava types were erupted from a shallow, zoned magma chamber from fissures distributed over the width of the inner rift valley and elongate parallel to it. Differentiation was accomplished by cooling and crystallization of plagioclase, olivine, and clinopyroxene toward the margins of the chamber. The centrally located hills were built by the piling up of frequent eruption of mainly primitive lavas which also are the youngest flows. In contrast smaller and less frequent eruptions of more differentiated lavas were exposed on both sides of the rift valley axis.

Increased transport of antarctic bottom water in the vema channel during the last ice age.

Abstract: Particle size analyses of surface sediments in the Vema Channel reveal a spatial variation related to the present hydrography. Similar analyses of sediment deposited during the last ice age (18,000 years before the present) indicate a maximum shallowing of the upper limit of Antarctic Bottom Water (AABW) of about 100 meters, coupled with an increase in velocity, which resulted in an increase in AABW transport.