Acute toxicity of copper to sea catfish

Sea catfish (Arius felis) were exposed to aqueous solutions of reagent grade cupric chloride in artificial seawater ($\text{30.0±2.0‰}$, 21–23°C) in four static bioassays. The 24, 48, 72 and 96 h LC₅₀ were calculated and found to be 5.43, 4.17, 3.57 and 2.40 mg l.^?1 copper, respectively. Experimental concentrations of copper producing subtle behavioral changes in this species correspond to less than 0.3% of the 72 h LC₅₀. Based on this comparison with literature values, a new, maximum ‘safe’ concentration for copper in marine waters of 0.01 mg l.^?1 is proposed.     

Comparison of the behavioural and acute toxicity of copper to sheepshead,Atlantic croaker and pinfish

Sheepshead (Archosargus probatocephalus), Atlantic croaker (Micropogon undulatus) and pinfish (Lagodon rhomboides) were each exposed to aqueous solutions of reagent grade cupric chloride in artificial seawater in four static bioassays. The 24, 48, 72 and 96-h TL_m were determined to be, respectively, 4.17, 3.02, 2.19 and 1.14 mg Cu²⁺·I^?1 for sheepshead, 9.15, 7.55, 7.20 and 5.66 mg Cu²⁺·I^?1 for croaker, and 7.33, 4.43, 4.14 and 2.75 mg Cu²⁺·I^?1 for pinfish. These results are compared with literature values of experimental concentrations of copper producing subtle behavioural changes in these species.     

Oxygen isotope fractionation in dissolved oxygen in the deep sea

¹⁸O variations in dissolved oxygen have been measured at five stations from the eastern equatorial Pacific, at the GEOSECS-I and -II intercalibration stations in the North Pacific and North Atlantic, and along an Antarctic-South Pacific section from MONSOON expedition. Relative to atmospheric oxygen, dissolved oxygen in the ocean is enriched in¹⁸O up to a maximum of 14‰, the extreme enrichments occurring in the oxygen-minimum region of the eastern Pacific. The vertical diffusion-advection model has been used to determine the isotopic fractionation of deep-water in-situ oxygen consumption ascribed to bacterial metabolism. The single-stage enrichment, ε, in Pacific Deep Water below 1 km is 10‰ (α = 0.99,¹⁶O consumed preferentially). The model calculations show that the isotopic data cannot be fit without the introduction of a fractionation factor, just as the dissolved oxygen data cannot be fit without an in-situ consumption parameter. The consistency of the positive sign for ε and the negative source term for O₂, observed in all deep Pacific profiles analyzed to date, provide strong evidence that vertical transport and in-situ consumption terms dominate the horizontal tracer flux terms, and indicate the presence of a significant “deep metabolism” in abyssal ocean waters.     

Primordial neon,helium, and hydrogen in oceanic basalts

A primordial neon component in neon from Kilauea Volcano and deep-sea tholeiite glass has been identified by the presence of excess²⁰Ne; relative to atmospheric neon the²⁰Ne enrichments are 5.4% in Kilauea neon and about 2.5% in the basalts. The²⁰Ne anomalies are associated with high³He/⁴He ratios; the ratio in Kilauea helium is 15 times the atmospheric ratio, while mid-ocean ridge basalts from the Atlantic, Pacific, and Red Sea have uniform ratios about 10 times atmospheric. Mantle neon and helium are quite different in isotopic composition from crustal gases, which are highly enriched in radiogenic²¹Ne and⁴He. The²¹Ne/⁴He ratios in crustal gases are consistent with calculated values based on G. Wetherill's¹⁸O (α,n) reaction; the lack of²⁰Ne enrichment in these gases shows that the mantle²⁰Ne anomalies are not radiogenic.²¹Ne enrichments in Kilauea neon and “high-³He” Pacific tholeiites are much less than in crustal neon, about 2 ± 2% vs. present atmospheric neon, as expected from the much lower⁴He/Ne ratios.Neon concentrations in two Atlantic tholeiites were found to be only 1–2% of the values obtained by Dymond and Hogan; helium concentrations are slightly greater and our He/Ne ratios are greater by a factor of 150. The large Ne excess relative to solar wind and meteoritic gases is thus not confirmed. Pacific and Atlantic basalts appear to be quite different in He/Ne ratios however, and He and Ne may be inversely correlated. He concentration variations due to diffusive loss can be distinguished from variations due to two-phase partitioning or mantle heterogeneity by the effects on³He/⁴He ratios. The He isotopic and concentration measurements on “low-³He” basalts are consistent with diffusive loss and dilution of the 3/4 ratio by in-situ radiogenic⁴He, and may provide a method for dating basalt glasses.Deuterium/hydrogen ratios in Atlantic and Pacific tholeiite glasses are 77% lower than the ratio in seawater. The inverse correlation between deuterium and water content observed by Friedman in erupting Kilauea basalts is consistent with a Rayleigh separation process in which magmatic water is separated from an initial melt with the same D/H ratio as observed in deep-sea tholeiites. The consistency of the D/H ratios in tholeiites containing primordial He and Ne components indicates that these ratios are probably characteristic of primordial or juvenile hydrogen in the mantle.     

High-resolution X-Band radar measurements of currents,bathymetry and sea state in highly inhomogeneous coastal areas

In this paper, high-resolution wave, current and water depth fields derived by marine X-Band radar are presented for a coastal region of extreme tidal currents in the presence of inhomogeneous bathymetry at the south coast of New Zealand’s North Island. The current and water depth information for the presented location covers an area of approximately 13 km² with a spatial resolution of 225 m and an update rate of 3 min. The sea state data provides a spatial representation of coastal effects like wave shoaling and refraction forced by bathymetry and current interaction. The near-surface current measurements about 3 km off the coast show expected tidal current pattern with maximum northwest/southeast current of 1.5–2 m/s alongshore. This is in agreement with currents from the RiCOM hydrodynamic model. The spatial resolution of the observed current field exhibits in addition small-scale current features caused by the influence of the local bathymetry. These data demonstrate the insight to be gained in complex, high-energy coastal situations through the use of high-resolution remote sensing techniques.     

Reflections from a randomly grooved interface: ultrasonic modelling and finite-diff erence calculation1

This study utilizes ultrasonic water tank modelling to examine the complexities which can result when seismic energy is diffracted by even a simple 3D interface structure. Ultrasonic laboratory modelling is carried out in our in-house water tank, using an aluminum block to simulate very simple ocean-bottom topography. The topography consists of parallel depressions which simulate valleys running parallel to a mid-ocean spreading ridge. This study shows that the phase and amplitude of primary ocean-bottom reflections can vary strongly with the azimuth of propagation. The trailing energy coda also varies dramatically as a function of propagation direction, showing the importance of developing a seismic model which includes the full 3D azimuthal distribution of interface structure.