Limnology and Oceanography

Thompson, R.; Battarbee, R. W.; O'Sullivan, P. E.; Oldfield, F.

doi: 10.4319/lo.1975.20.5.0687pmid: N/A

Initial magnetic susceptibility in Flandrian sediments from Lough Neagh, N. Ireland, is shown to be a function of the detrital titanomagnetite of the sediment. Parallel susceptibility changes are synchronous from core to core and thus potentially valuable for core correlation especially in view of the rapid nondestructive techniques developed for measurement. Changing susceptibility in the lake sediments studied appears to be positively correlated with variations in the amount of inwashed inorganic allochthonous material present in the cores.

doi: 10.4319/lo.1975.20.5.0698pmid: N/A

Sasseville, Dennis R.; Norton, Stephen A.

doi: 10.4319/lo.1975.20.5.0699pmid: N/A

Undisturbed 1‐m cores of profundal sediment and overlying water were collected from four morphometrically paired Maine lakes with differing alkalinities and degrees of cultural development. Vertical variations in sediment chemistry correlate with the onset of European man’s activity in the watersheds of three of the lakes, although behavior is individual for any given element. Precultural core averages of P, S, organic matter, and diatoms are consistently higher in the sediments of the two deep oligotrophic lakes while the sediments of the two shallow mesotrophic lakes contain higher concentrations of quartz and aluminosilicate elements (K, Na, Ca, Mg, Al). This implies strong morphometric control of lacustrine sediment characteristics.

Toth, David J.; Lerman, Abraham

doi: 10.4319/lo.1975.20.5.0715pmid: N/A

Pronounced salt concentration gradients in five antarctic, arctic, and Pacific coastal lakes an be accounted for by diffusional transport of salt out of the deeper saline water layers. The computed values of the mean salt diffusion coefficients, based on the ages of salinity stratification, agree to within an order of magnitude with molecular diffusivities for four out of five lakes. This agreement suggests that no major mixing events occurred in the water column during the late historical stages of the lakes. Upper limit time estimates for the removal of most of the salt from the saline bottom layers range from 5,000 to 35,000 years, depending on lake depth. Historical records of deepening of the Great Bitter Lake owing to dissolution of a salt layer on the bottom suggest that dissolution was a diffusion controlled process. For the saline brines in the Red Sea Deeps, an assumption that they are transient structures leads to the following estimates of the time to mixing with Red Sea water: 103–104 years, if mixing takes place by diffusional transport of salt between the heavier and lighter brines, and 104–105 years, if salt diffuses from the brines upward. The geologically short range of times suggests that the possible recycling of evaporative brines through the deeper ocean could not affect the ocean water salinity for any significant time interval.

Noshkin, V. E.; Wong, K. M.; Eagle, R. J.; Gatrousis, C.

doi: 10.4319/lo.1975.20.5.0729pmid: N/A

X‐radiography and autoradiography of thin vertical sections were used to estimate the growth rate of a specimen of Favites virens from Bikini Lagoon. Discrete bands of radioactivity were identifiable with specific nuclear test series. The coral growth rate of 8.0 mm year−1 determined by autoradiography is in good agreement with the rate of 8.1 ± 2.2 mm year−1 derived from the “seasonal” alternating light and dark bands on X‐radiographs. With these bands as growth rate indicators, the coral was sectioned into yearly increments and analyzed by low‐level, nondestructive gamma spectrometry, radiochemical techniques, and mass spectrometry to reconstruct the variations in the concentration of transuranics and other radionuclides in the marine environment at Bikini since 1954. From the concentration data retained in this indicator species, the exchange rate of radionuclides between the lagoon and the open ocean is computed to be longer than exchange rates based on physical circulation data. There is no constant ratio of plutonium isotopes in the coral growth sections, suggesting that the redistributions of the several plutonium isotopes in the environment may be governed by different biogeochemical processes. Increased levels of 210Po (210Pb) were found in test‐year growth sections, contradicting previous arguments that no 210Pb has resulted from weapons testing.

Emerson, Steve

doi: 10.4319/lo.1975.20.5.0743pmid: N/A

The exchange of carbon dioxide between the atmosphere and water is governed by the kinetics of diffusion and reaction in the interfacial boundary layer. Previous derivations of the equations describing this process are not always applicable to lakes. A general model, developed to explain the CO2 exchange rate in eutrophic Lake 227 of the Experimental Lakes Area, indicates that carbon dioxide invasion into this lake is five to ten times that predicted if there were no reaction. The model results conform with data from laboratory CO2 invasion experiments. The large chemical enchancement in Lake 227 is caused by a strong CO2 gradient resulting from an epilimnion depleted of carbon dioxide by eutrophication. These results indicate that calculations of the CO2 gas exchange rate, especially in eutrophic lakes, must consider the possibility of a relatively large enhancement factor.

Emerson, Steve

doi: 10.4319/lo.1975.20.5.0754pmid: N/A

A method for determining the transfer rate of gases between water and the atmosphere in the ocean, using the isotope pair 220Ra and 222Rn, is extended to small lakes in northwestern Ontario. Three independent experiments from 1971 through 1972 have established the gas exchange velocity in these lakes to be 0.2 ± 0.1 m day−1 (corresponding to a “boundary layer” of about 600 µ). This rate is one of the lowest observed in natural waters to date— less than a tenth of oceanic values and several times less than in the U.S. Great Basin lakes. A compilation of diverse gas exchange results, where wind velocity has also been measured, indicates that the results of laboratory experiments comparing wind velocity with gas transfer conform fairly well with the natural situation.

Blanchard, Duncan C.; Syzdek, Lawrence D.

doi: 10.4319/lo.1975.20.5.0762pmid: N/A

Jet and film drops from bubbles bursting in the presence of an electric field will be charged by electrostatic induction. If the field is sufficiently high, the drops move rapidly upward under the influence of an electrical force to impact on any suitable collecting surface. Magnesium oxide‐coated glass slides make an excellent collector for determination of the size distribution of either jet or film drops. An agar plate collector can be used to collect all of the jet drops for bacterial analysis. Combining the two types of electrostatic collectors provides evidence that suggests that the enrichment of bacteria in jet drops is highest on the top or uppermost drop and decreases progressively to a minimum value for the last few jet drops to be ejected from the bubble.

Kitchen, James C.; Menzies, David; Pak, Hasong; Ronald, J.; Zaneveld, V.

doi: 10.4319/lo.1975.20.5.0775pmid: N/A

Particle size distributions (8–105‐µm diameter), chlorophyll a, and particulate carbon were measured off the Oregon coast during July 1973. The particle counts were transformed to volume concentration and then subjected to characteristic vector analysis. Ninety‐two percent of the variance was accounted for by linear combinations of the first two characteristic vectors. Two weighting factors define the proportions of the two characteristic vectors which will, when added to the mean volume concentration curve, approximate the actual data for each sample. Variations in the first weighting factor correspond well with variations in total volume. Changes in the second weighting factor indicate which segment of the size range contains the largest proportion of the particulate volume. Comparison with temperature and salinity data indicated that the near surface water with proportionately large volumes of particles less than 20 µm was warmer and less saline than the surface waters with large volumes between 20 and 50 µm. High correlation with particulate carbon and chlorophyll suggests that in both cases a large proportion of the particles is phytoplankton.

Kelley, J. C.; Whitledge, T. E.; Dugdale, R. C.

doi: 10.4319/lo.1975.20.5.0785pmid: N/A

Sea surface maps of temperature, salinity, nitrate, silicate, phosphate, and fluorescence were produced almost daily during a 6‐week cruise (PISCO) in the Peru upwelling system in the austral fall, 1969. The maps were produced by a shipboard computer from data gathered with the ship underway. The maps show persistent “plumes” of freshly upwelled water associated with coastal irregularities and prominent bathymetric features. The information on the location, orientation, and extent of these plumes was used to locate stations where primary productivity experiments were carried out. The definition of persistent plumes has led to the development of successful two‐dimensional simulation models of the ecosystem.