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Effects of low ΔT power plant temperatures on estuarine invertebrates
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.
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.