A COMPARISON OF EASTERN AND WESTERN HONG KONG PHYTOPLANKTON FROM WEEKLY SAMPLES (1997-1999)

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Shock chemistry in the molecular clouds associated with SNR IC 443

Several interstellar molecules have been detected toward the highly perturbed B and G clouds associated with the supernova remnant IC 443 via their 3 mm transitions, including N2H+, SiO, SO, CN, HNC, and H13CO+. The (J, K) = (1, 1) and (2, 2) inversion lines of metastable ammonia have also been observed, as well as the J = 3-2 transition of HCO+ at 1.2 mm. Analysis of the (1, 1) and (2, 2) inversion lines of NH3 indicates minimum gas kinetic temperatures of TK = 70 K toward cloud B, and TK = 33 K in cloud G. Modeling of the J = 1-0 and J = 3-2 transitions of HCO+ implies densities greater than 10(5) cm-3 toward both positions. These data clearly show that hot and dense material is present in IC 443, and they suggest the presence of shocks in both regions. A careful analysis of the HCO+ lines indicates that the HCO+ abundance is at most enhanced by factors of a few over that found in cold, quiescent gas. This conclusion contradicts past claims of HCO+ abundance enhancements of several orders of magnitude in the perturbed regions. The N2H+ abundance was also found to be similar to that in cold gas, suggesting that there is no increase in ionization in the clouds. The abundances of SO and CS, as well as CN and NH3, do not appear to differ significantly from those found in cold dark clouds, although chemistry models predict sulfur-containing species to undergo high-temperature enhancements. SiO, however, is found to have an abundance in the perturbed gas 100 times larger than the upper limits observed in the dark cloud TMC 1, a result in agreement with high temperature chemistry models. In addition, the HNC/HCN ratio in both IC 443 B and G was found to be approximately 0.1--far from the ratio of 1 predicted by low-temperature ion-molecule chemistry, but similar to the values observed in clouds where elevated temperatures are present.     

Studies on the plankton and sediment diatoms in Xuanwu Lake,Nanjing, China

The sediment diatom data based on a 16 cm long sediment core removed from near the center of the lake indicated that nutrient pollution tolerant diatoms have replaced pollution intolerant taxa which were common near the base of the core (about 35 years before present). These observations support the hypothesis that there is progressive eutrophication in Xuanwu Lake. This conclusion is corroborated by direct comparisons of the present day phytoplankton and zooplankton species composition within the lake and published accounts of its species composition during the mid 1970s.     

New aspects of the equilibrium pole tide

Summary. We have developed a new spherical harmonic algorithm for the calculation of the loading and self-gravitating equilibrium pole tide. Based on a suggestion of Dahlen, this approach minimizes the distortions in tide height caused by an incomplete representation of the ocean function. With slight modification our approach easily could be used to compute self-gravitating and loading luni-solar tides as well.
Using our algorithm we have compared the static pole tide with tide observations at a variety of locations around the world. We find statistically significant evidence for pole tide enhancements in mid-ocean as well as the shallow seas.
We have also re-investigated the effect of the static tide on the Chandler wobble period. The difference between the wobble period of an oceanless, elastic earth with a fluid core (Smith & Dahlen) and the period of an earth minus static oceans yields a 7.4-day discrepancy. We conclude from tide observations that much of the discrepancy can probably be accounted for by non-equilibrium pole tide behaviour in the deep oceans.     

Changes in phytoplankton following nitrate and phosphate additions to large enclosures in Marion Lake,British Columbia

The addition of nitrate, phosphate and a nitrate phosphate combination to replicated wooden enclosures in Marion Lake resulted in significant increases in primary productivity and algal standing crop in each of the three types of treated enclosures. This indicated that no single nutrient is likely to simultaneously limit the growth of all phytoplankton species present at any one time in the lake epilimnion. The relevance of this to the detergent controversy is discussed. Canadian Contribution to the International Biological Programme No. CCIBP 208.     

Ocean tides for satellite geodesy

Abstract

Spherical harmonic tidal solutions have been obtained at the frequencies of the 32 largest luni‐solar tides using prior theory of the author. That theory was developed for turbulent, nonglobal, self‐gravitating, and loading oceans possessing realistic bathymetry and linearized bottom friction; the oceans satisfy no‐flow boundary conditions at coastlines. In this theory the eddy viscosity and bottom drag coefficients are treated as spatially uniform. Comparison of the predicted degree‐2 components of the Mf, PI, and M2 tides with those from numerical and satellite‐based tide models allows the ocean friction parameters to be estimated at long and short periods. Using the 32 tide solutions, the frequency dependence of tidal admittance is investigated, and the validity of sideband tide models used in satellite orbit analysis is examined. The implications of admittance variability for oceanic resonances are also explored. By extending the theory to include a second constraint derived from tide observations or data‐constrained tide models, it is possible to assess those models from a fluid dynamic perspective. One general conclusion from such exercises is that the large higher‐degree admittances of current short‐period tide models are dynamically incompatible with their degree‐2 admittances. Eventually it may prove possible to produce dynamically sound, observationally consistent tide models by combining the author's tide theory with satellite orbit determination.     

Organochlorines in Hong Kong Fish

Muscle samples from 15 species of fish (n=1) purchased from markets in Hong Kong and 10 liver samples of tilapia (Tilapia mossambica) collected from the Shing Mun River were analysed for organochlorines (polychlorinated biphenyls, ΣDDTs, hexachlorobenzene, hexachlorocyclohexanes, chlordanes, mirex and dieldrin). Polychlorinated biphenyls (PCBs) were detected in 15 market fish samples but the levels were very low (around 1 ng g⁻¹). PCB levels in tilapia livers collected from Tai Wai (29.3–65.1 ng g⁻¹) were higher than those from Fo Tan (3.5–23.2 ng g⁻¹) suggesting that there may be some local point soucres. ΣDDTs were detected in all samples, ranging from 3.3 to 75.6 ng g⁻¹ in the market fish and from 7.1 to 88.8 ng g⁻¹ in tilapia. The DDE/DDT ratios in the market fish (0.12–0.75) showed higher variability than those of tilapia (0.30–0.46), suggesting that some of the market fish may have been collected from areas where DDT was recently used. Results of this preliminary study show that organochlorine levels in Hong Kong market fish are low and do not cause any concern for human consumption. An on-going monitoring program, however, is recommended.