勘查深部矿的地电化学方法实际应用的一些情况

对于以分析土壤中多种赋存形式元素为基础的勘查深部矿的地球化学方法已引起全球范围兴趣的增加。基于十余年之经验，作者在这里讨论了这些方法各种地电化学变型的优势及不足之处。     

Molecular evidence for multiple UDP-glucuronosyltransferase gene familes in fish

The presence of multiple distinct UGT genes in fish was derived by analysis of DNA sequence data derived the zebrafish EST project, confirming indications from previous protein purification studies in another fish species, the plaice, for a diversity of isoforms in lower vertebrates. At least 10 different UGTs can be identified from nucleotide sequence data in zebrafish. Phylogenetic analysis of exon 1 sequences of the zebrafish, plaice and human UGTs indicates that six of these genes are related to the 1A, 1B and 2 families and that a further four genes were of more ancient lineage. Importantly data for the 3' sequences of the zebrafish clones, both from the database and our own sequences of the publicly available clones did not provide any evidence for elaboration of family 1A genes by alternative splicing in this lower vertebrate.     

Application of real time PCR determination to assess interanimal variabilities in CYP1A induction in the European flounder (Platichthys flesus)

In both laboratory experiments and field investigations with fish a large interanimal variability in CYP1A expression has been observed which may be attributed to variations in environmental inducer exposure and/or inducer response. We are carrying out laboratory investigations to assess the contribution of a potential genetic component in inducer response of flounder (Platichthy sflesus) CYP1A to PCB exposure and in this paper we report development of a sensitive quantitative RT-PCR procedure (real time PCR) where accumulation of the intercalated dye SYBR Green I is followed during cycling. Preliminary experiments using this procedure with artificially reared Arochlor 1254-treated flounders showed large interanimal differences in response for a single family group indicating that variability does have a genetic basis.     

Consistent fractionation of 13C in nature and in the laboratory: growth-rate effects in some haptophyte algae

The carbon isotopic fractionation accompanying formation of biomass by alkenone-producing algae in natural marine environments varies systematically with the concentration of dissolved phosphate. Specifically, if the fractionation is expressed by epsilon p approximately delta e - delta p, where delta e and delta p are the delta 13C values for dissolved CO2 and for algal biomass (determined by isotopic analysis of C37 alkadienones), respectively, and if Ce is the concentration of dissolved CO2, micromole kg-1, then b = 38 + 160*[PO4], where [PO4] is the concentration of dissolved phosphate, microM, and b = (25 - epsilon p)Ce. The correlation found between b and [PO4] is due to effects linking nutrient levels to growth rates and cellular carbon budgets for alkenone-containing algae, most likely by trace-metal limitations on algal growth. The relationship reported here is characteristic of 39 samples (r2 = 0.95) from the Santa Monica Basin (six different times during the annual cycle), the equatorial Pacific (boreal spring and fall cruises as well as during an iron-enrichment experiment), and the Peru upwelling zone. Points representative of samples from the Sargasso Sea ([PO4] < or = 0.1 microM) fall above the b = f[PO4] line. Analysis of correlations expected between mu (growth rate), epsilon p, and Ce shows that, for our entire data set, most variations in epsilon p result from variations in mu rather than Ce. Accordingly, before concentrations of dissolved CO2 can be estimated from isotopic fractionations, some means of accounting for variations in growth rate must be found, perhaps by drawing on relationships between [PO4] and Cd/Ca ratios in shells of planktonic foraminifera.     

Field observations on correlation of fatty acid profiles between suspended particulate matter and green-lipped mussels in subtropical waters of Hong Kong

By analysis of the fatty acid profiles in mussel tissues and suspended particulate matter (SPM) in water, the present study showed a significant relationship of the trophic linkage between mussels and the SPM. At seven locations from inner to outer areas along the eutrophic Tolo Harbour and Tolo Channel, Hong Kong, the composition (as percentage of total fatty acids) of both monoenoic and polyunsaturated fatty acids in the tissues of green-lipped mussels Perna viridis and SPM in water had significant correlation (p<0.01). In particular, the composition of docosahexaenoic acid (DHA, 22:6n3) (as percentage of total fatty acids) in mussel tissues was statistically correlated with that in SPM (p<0.01), implying that mussels incorporate DHA, the biomarker of dinoflagellates. Principal component analysis further demonstrated that the fatty acid profiles of SPM were different among locations in the harbour, mid and outer channel of the study area, so were the mussel tissue fatty acid profiles. Cluster analysis of phytoplankton data also revealed the dominance of diatoms in the inner harbour and channel areas, whereas dinoflagellates were abundant in the outer channel waters. The possible implications of using benthic suspension feeders such as green-lipped mussels P. viridis for controlling phytoplankton abundance in coastal waters are discussed.     

Spatio-temporal changes of marine macrobenthic community in sub-tropical waters upon recovery from eutrophication. II. Life-history traits and feeding guilds of polychaete community

A two-year study was conducted in the vicinity of a harbour in sub-tropical Hong Kong, to examine the progress of recovery of macrobenthic community, based on analyses of both life-history traits and trophic guilds of polychaetes, upon cessation of organic pollution caused by sewage discharge. Seventy seven out of 83 species collected were classified under four ecological groups based on the life-history traits and sensitivity to organic gradients. The mean ATZI marine biotic index (AMBI) derived from these ecological groups showed spatial difference among the five sampling locations. In particular, the presence of different percentages of polychaete species from Groups III (unbalanced community) and IV (polluted community) suggested the presence of pollution stress in certain degree at all sampling locations. However, no significant temporal changes were noted over the study period. From all polychaete species identified, they were classified into 13 feeding guilds. The mean diversity of these feeding guilds at most of the sampling locations was significantly higher than that at one of the inside-harbour locations. The composition of feeding guilds was also significantly different spatially. At one of the inside-harbour locations, the dominant feeding guilds were motile/discretely motile surface deposit feeders with tentaculates or unarmed pharynx, and motile omnivores with jawed pharynx in the first year of study, but were replaced by motile, jawed carnivores in the second year of study. The increased proportion of carnivores over the study period can be seen as a sign of recovery in the community structure since abundance of predators is commonly higher in habitats with better environmental quality. The implications of using life-history traits and feeding guild analyses for benthic community are discussed.     

Effects of nutrient enrichment derived from fish farming activities on macroinvertebrate assemblages in a subtropical region of Hong Kong

To study the correlation between nutrient enrichment derived from fish farming activities and changes in macrobenthic assemblages, a one-year field study was conducted in Kau Sai Bay marine fish culture zone of Hong Kong. Bimonthly sediment samples were collected at six stations: two at the fish cages, two near the boundary of the fish culture area, and two reference sites further away from the culture area. Sediment physico-chemical characteristics in terms of silt/clay fraction, moisture content, total organic carbon (TOC), total Kjeldahl nitrogen (TKN) and total phosphorus (TP) were analyzed. The macrobenthos (>0.5 mm) present in the sediment were sorted, identified and enumerated. On average, TOC, TKN and TP levels at the fish cage stations were 82.8%, 128.5% and 1315.7% higher than those at the reference stations, respectively. As a result, the N:P molar ratio was greatly reduced from 8.75 at the reference stations to 1.83 at the fish cage stations. Univariate and multivariate analyses revealed that diversity of macrofauna was significantly reduced and community structure differed at the fish cage stations relative to the reference sites. The intermediary stations near the fish culture area showed a transitional state of disturbance. Faunal diversity was negatively correlated with nutrient level, reflecting the adverse impacts of nutrient enrichment derived from fish farming activities on the benthic assemblages. Whilst in subtropical Asia-Pacific trash fish is the major feed for fish culture resulting in a higher nutrient loading and nutrient ratio accumulated in the sediment beneath the fish rafts, the effects of nutrient enrichment on macrobenthic assemblages are comparable to that in temperate waters owing to relatively high sediment metabolism rate and smaller fish culture scale in Hong Kong.     

Intermittent exposure to reduced oxygen levels affects prey size selection and consumption in swimming crab Thalamita danae Stimpson

Portunid crabs Thalamita danae (carapace width: 46–56 mm) were exposed to low oxygen level (4.0 mg O₂ l⁻¹) and hypoxia (1.5 mg O₂ l⁻¹) for 6 h each day with three size classes (large: 15.0–19.9 mm, medium: 10.0–14.9 mm, small: 5.0–9.9 mm) of mussels Brachidontes variabilis offered as food. Consumption rate, prey size preference, and prey handling including breaking time, handling time, eating time and prey value, were studied during the time the crabs were exposed to reduced oxygen levels and results were compared with the crabs maintained at high oxygen level (8.0 mg O₂ l⁻¹) throughout the experiment. Consumption of mussels from all size classes was significantly higher at high oxygen level than at reduced oxygen levels. No mussel size preference was observed for crabs exposed to 4.0 or 8.0 mg O₂ l⁻¹ but those crabs exposed to 1.5 mg O₂ l⁻¹ preferred medium mussels. Both breaking time and handling time increased with mussel size but did not vary with oxygen level. Prey value of each mussel consumed (mg dry wt eaten crab⁻¹ s⁻¹) was calculated by dividing the estimated dry weight of the mussel by the observed handling time. Mean prey value varied significantly with mussel size, with values obtained for large mussels being higher than small mussels at 4.0 and 8.0 mg O₂ l⁻¹; the effect of oxygen level, however, was insignificant. In view of portunid crabs as major predators of mussels, results may help explain dominance of mussels in eutrophic harbours in Hong Kong.