Distribution of nutrient salts in waters of the middle and the southern Adriatic sea

Distribution of nutrient salts in waters of the middle and the southern Adriatic sea

Oceanographic Abstracts 259 BROWN B.E., J. A. BRENNAN, M. D. GROSSLE1N, E. G. HEYERDAHL and R. C. HENNEMUTH, 1976. The effect of fishing on the mari...

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Oceanographic Abstracts

259

BROWN B.E., J. A. BRENNAN, M. D. GROSSLE1N, E. G. HEYERDAHL and R. C. HENNEMUTH, 1976. The effect of fishing on the marine finfish biomass in the northwest Atlantic from the Gulf of Maine to Cape Hatteras. Int. Commn NI~ Atlantic Fish. Res. Bull., 12: 49-68. Relationships between fishing effort, total finfish community biomass, and yield are determined using data on finfish biomass measured by research vessel trawl surveys and commercial catch and effort statistics. Combined individual species stock assessments and the Schaefer (1954) equilibrium }ield model are utilized to estimate potential yields. The fishing effort of different gear types are combined to provide a standardized index of fishing effort in terms of days fished as reported to the International Commission for the Northwest Atlantic Fisheries (ICNAF). A multiplicative learning function is applied as a correction factor to reported days fished of newly developing fisheries, i.e., those deployed in areas and on stocks not previously fished. This correction factor adjusts data of fleets entering a fishery to the level of efficiency achieved by the third year in the fishery. These analyses demonstrate a six-fold increase in fishing intensity, and a 55% decline in finfish abundance during the period 1961 - 72. Plots of yield versus standardized fishing effort indicate that fishing mortality since 1968 has exceeded that which would result in sustaining a maximum yield from the stocks under equilibrium conditions. The projected maximum sustainable yield (MST) from Schaefer yield curves is 900,000 tons 2, while the sum of the MSY's from individual assessment studies is 1,300,000 tons. It is suggested that because of species interactions summing the MSY's from individual assessments may be an overestimate of the total MSY. BROWN G. W. Jr., 1976. Effects of polluting substances on enzymes of aquatic organisms. Z Fish. Res. Bd Can., 33 (9): 2018-2022. The toxicity of heavy metal cations often considered as pollutants is discussed with respect to several enzymes of nitrogen metabolism in the trout Salmo gairdneri and the polychaete Eudistylia vancouveri. Data on trout liver ornithine aminotransferase (EC 2.6.1.13) activity under inhibition by mercuric ion yield a straight line when percent inhibition on a probability axis is plotted vs. logarithm of mercuric ion concentration. Allantoinase (EC 3.5.2.5) of E. vancouveri is inhibited by divalent cations of Cu, Hg, Zn, Pb, and Cd. At low concentrations ( ~ lO-SM) these ions lead to an enhancement of activity of allantoinase. A short review is provided on the adaptation of fish to environmental changes. BUBNOV V.A., K. V. MOROSHKIN, V. D. EGOR1KH1N and Z. N. MATVEEVA, 1976. Variability of currents in the Equatorial Atlantic. (In Russian; English abstract.) Okeanologiia, 16 (3): 408~,15. Analysis is made of the oceanographic measurements accomplished from aboard the R/V Akademik Kurchatov on the meridional section of five buoy stations along 23°30'W longitude in the equatorial region during the GATE - 74 international expedition. A zonal water transport was recorded m the upper 40 m layer during three phases of GATE. The boundary between the South Equatorial Current and the Lomonosov Current was found at depths of 30 - 35 m. The Lomonosov Current core with more than 70 cm/sec -~ velocity was on the average as deep as 75 m. The West Intermediate Equatorial Current was absent during the first and the second phases and appeared during the third phase. Wave displacements of the Lomonosov Current axis with respect to the Equator with an amplitude of nearly 1° of latitude and a period of about 18 days recorded by the Akademik Kurchatov were noted also by the US research ship C. lselin at 28°W longitude. BUCKLEY J. R. and S. POND, 1976. Wind and the surface circulation of a fjord. Z Fish. Res. Bd Can., 33 (10): 2265-2271. An experiment has been carried out recently to investigate the relative effects of wind, tide, and river runoff on the circulation of the surface layer of a small fjord. Drogues were tracked with a radar set for several days at four locations. Data were recorded photographically and digitized for computer processing to produce the velocity and acceleration of each drogue along its track. Wind forcing was dominant. The river input was important too, causing large horizontal shears in the flow. Tidal effects appeared to be negligible. Frictional coupling between the surface layer and the water below appeared to be very small. A mechanism for the surface layer behavior is proposed with the layer nearly decoupled from the underlying water by a strong pycnocline. The basic assumptions of this mechanism applied to the data set yield an average drag coefficient of 1 to 2 × 1 0 - 3 . BULJAN M., L. STOJANOSK1 and 1. VUKADIN, 1974/75. Distribution of nutrient salts in waters of the middle and the southern Adriatic Sea. ThalassiaJugosl., 11 (1/2): 139-149. The paper contains the results of the investigations on nutrient salts made at four strategic points controlling the Adriatic Sea: (a) both of the Adriatic pits (deep up to 1,200 m), (b) the Palagru~a sill, and (c) a sea bay placed close to a larger town. The investigations covered all the seasons of 1973. The distribution in the areas and depths are discussed in terms of the following parameters: NO3-N, NO2-N, NH4-N, PO4-P, P-org., P-tot, and the resulting characteristics allow the regions to be identified as consumers or suppliers of nutrient salts.

260

Oceanographic Abstracts

The Bay of Ka~tela shows eutrophication of the waters. The values found for the ratio N/P are discussed and compared with those of other authors. On the basis of yearly averages the Bay Ka~tela was found to have the most favourable conditions for biological activity of the four investigated areas. There is a relatively rich content of nitrogen salts (nitrate and amonium forms) in the Jabuka and in the South Adriatic Pit. The opinion that N-salts should be the minimum productivity factor of the Adriatic Sea has been rejected. Taking the N/P ratio as the starting point it is concluded that phosphate is the salt which plays that role. BUMPUS D. F., 1976. Review of the physical oceanography of Georges Bank. Int. Commn NWAtlantic Fish. Res. Bull., 12: 119-134. Previously published information on the bathymetry, rotating tidal currents, temperature.salinity distribution and general circulation of the Gulf of Maine and Georges Bank are discussed. New information on surface temperature fi'onts in relation to monthly Ekman transport vectors is presented. Data on the distribution of herring larvae during successive periods during the autumns of 1972, 1973, and 1974 are used as evidence of dispersion and advection. Feasible approaches toward development of a circulation model are mentioned. BURTON D.T., L. B. RICHARDSON, S. L. MARGREY and P. R. ABELL, 1976. Effects of low A T power plant temperatures on estuarine invertebrates. J. Wat. Pollut. Control Fed., 48 (I0): 2259-2272. This study was initiated to assess thermal impact that may occur to estuarine macroinvertebrates entrained through low /x T (5°C maximum) steam-electric generating stations with once-through cooling systems designed for rapid mixing in receiving streams. The time-temperature model used in this study did not cause any immediate or latent mortality of any species at the seasonal temperatures studied; therefore, the question of "sublethal" thermal stress was addressed by using changes in whole animal oxygen consumption patterns as an indicator of stress. Although some species responded by a signficant increase in oxygen consumption when exposed to the time-temperature model, the response was determined to be a normal physiological temperature compensation response and not a response indicative of thermal stress. This study suggests that thermal impact to estuarine macroinvertebrates entrained through low A T power plants with once-through cooling systems designed for rapid mixing in receiving streams should be minimal and should therefore allow utilities to meet many current federal and state discharge temperature regulation requirements. BUTLER R.F., S. K. BANERJEE and J. H. STOUT, 1976. Magnetic properties of oceanic pillow basalts: evidence from Macquarie Island. Geophys Jl R. astr. Soc., 47 (1): 179-196. A combined palaeomagnetic, hysteresis, thermomagnetic, and electron microprobe study has been carried out on pillow basalts from Late Tertiary oceanic crust exposed on Macquarie Island. Oriented cores were collected from four sites in the North Head region where the basalts are unmetamorphosed but have suffered pervasive seafloor weathering and at four sites near Langdon Point where the pillow lavas have experienced metamorphism to the greenschist facies. Field geological and petrologic evidence suggests that the North Head samples are representative of the weathered zone of Late Tertiary oceanic crust while the specimens from Langdon Point are represenzative of pillow basalts from > 500 m into the oceanic lithosphere. Geometric mean intensities of natural remanence (NRM) were 0.7 X 10 -3 G for North Head samples and 0.6 X 10 -3 G for specimens from Langdon Point. The geometric mean values of low field susceptibility (×) and Koenigsberger ratio (Q) for North Head samples (0.1 X 1 0 -3 G Oe -j and 9.8) are similar to those of DSDP basalts. The mean value of X and Q for Langdon Point samples (2.8 X t0 -3 GOe -~ and 0.3) is similar to those observed in metabasalt dredged from oceanic escarpments. Hysteresis, thermomagnetic and electron microprobe data indicate that the titanomaghemites in the North Head samples have suffered a high degree of low temperature oxidation. Langdon Point samples show reversible thermomagnetic curves with a magnetic Curie temperature (580 °C), indicating that metamorphism has altered the magnetic mineralogy. This metamorphism is thought to occur at or near the ridge during the seafloor spreading process. Thus, the NRM of the metamorphosed pillow basalts would still record geomagnetic reversals and contribute to magnetic lineations. The low NRM intensities are ascribed to prolonged seafloor weathering of North Head samples and to metamorphism of the basalts from Langdon Point. Since the 10 -3 G NRM intensities of pillow basalts are too low to account for the observed amplitude of marine magnetic anomalies, the underlying basaltic and doleritic sheeted dyke complex must also contribute to the anomalies. CATO D.H., 1976. Ambient sea noise in waters near Australia. Z acoust. Soc. Am., 60 (2): 320-328. Ambient sea noise has been meas~ared at 40 positions in mainly tropical waters near Australia: in the Indian Ocean; the Arafura and Timor Seas; and in the Coral and Tasman Seas (Pacific Ocean). Wind speed dependence was observed at all frequencies of measurement from 22 to 5,000 Hz. At hydrophones suspended at depths between 8 and 25 m, the wind-dependent noise appeared to be independent of bottom depth which varied from 26 to 6,700 m. The rate at which wind-dependent noise increased with increasing wind speed was found to be significantly less than has been observed in the North Atlantic Ocean. Non-wind-dependent noise, observed at frequencies below 250 Hz, varied by about 10 dB within a particular sea and by up to 20 dB between seas, and could be broadly related to the relative shipping densities and propagation conditions in the invididual seas. In the shallow Arafura and Timor Seas north of Australia, there is evidence that noise of distant shipping is not a significant component of the ambient noise. A model of traffic noise in the Tasman Sea predicts levels in agreement with observed noise levels.