Separation of selected PAHs by using high performance capillary electrophoresis with modifiers

The effect of varying SDS concentration in a micellar electrokinetic capillary chromatographic system (MECC) is investigated. In addition, the introduction of -cyclodextrin as modifier to the electrophoretic medium, containing SDS and a phosphate-borate buffer, is shown to give satisfactory separation of the seven selected PAHs. The separation efficiency is increased with the addition of -cyclodextrin.     

Allozyme electrophoretic analysis of the Hediste limnicola — H. diversicolor — H. japonica species complex (Polychaeta: Nereididae)

Three morphologically similar species of the polychaete genus Hediste [H. limnicola (Johnson, 1901), H. diversicolor (O. F. Müller, 1776), and H. japonica (Izuka, 1908)] have been described, respectively, from the west coast of North America, Europe, and Japan. Although these taxa are geographically isolated by oceans, the morphological criteria by which they can be separated are sufficiently variable as to make identification difficult. We have compared these three taxa biochemically using ten allozyme loci and have found that they are genetically distinct and constitute valid species. H. japonica (collected in June 1990 from Kyushu, Japan) appears more closely related to H. limnicola (collected in July 1989 from two sites in California and two in Oregon, USA) than it is to H. diversicolor (collected in October-November 1989 from the Weser estuary and the Jadebusen in Germany). H. limnicola has been recognized previously as a self-fertilizing hermaphrodite, but it is quite polymorphic in the four populations examined and we suggest that some cross-fertilization must occur in the field. Marked allele frequency differences between the two H. diversicolor populations examined, which were separated by only about 30 km, suggested that there was restricted gene flow between populations, or that there had been strong short-term selection.     

Irrigation runoff insecticide pollution of rivers in the Imperial Valley, California (USA)

The Alamo and New Rivers located in the Imperial Valley, California receive large volumes of irrigation runoff and discharge into the ecologically sensitive Salton Sea. Between 1993 and 2002 we conducted a series of studies to assess water quality using three aquatic species: a cladoceran (Ceriodaphnia dubia), a mysid (Neomysis mercedis), and a larval fish (Pimephales promelas). Although no mortality was observed with the P. promelas, high-level toxicity to the invertebrate species was documented in samples from both rivers during many months of each year. Toxicity identifications and chemical analyses identified the organophosphorus insecticides (OP), chlorpyrifos and diazinon, as the cause of C. dubia toxicity. The extent of the C. dubia mortality was highly correlated with quantities of these OPs applied in the river watersheds. C. dubia mortality occurred during more months of our 2001/2002 study than in the 1990s investigations. During 2001/2002, the extensive C. dubia mortality observed in New River samples was caused by OP insecticide pollution that originated from Mexico. Mortality to N. mercedis in New River samples was likely caused by contaminants other than OP insecticides. Our studies document OP insecticide-caused pollution of the Alamo River over a 10-year period and provide the necessary information for remediation efforts.     

Study on the cytotoxicity of microcystin-LR on cultured cells

The toxicity of purified blue-green algal toxin, microcystin-LR, on permanent cell lines KB, NIH/3T3, H-4-II-E, HeLa, Vero, Hep G2, Caco-2 and HL-60 was studied. Assessment of cell viability using colorimetric 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays indicated that purified microcystin-LR induced toxic effect on KB and H-4-II-E cell lines after 96 h incubation at toxin concentrations greater than 18.75 microg/ml. KB cell line was selected for further study when reproducibility, consistency and sensitivity were considered. Significant amounts of lactate dehydrogenase (LDH) were released from KB cells when incubation durations were 72 and 96 h with toxin concentrations of 18.75 microg/ml and higher. Although previous studies suggested that microcystin-LR had no cytotoxic effect on permanent cell lines, LDH release assay performed on KB cells indicated that exposure to microcystin-LR could result in damage to the cell membrane.     

Direct coupling of supercritical fluid extraction-supercritical fluid chromatography for the determination of selected polycyclic aromatic hydrocarbons in aqueous environmental samples

A rapid and simple method is described for the quantitative determination of polycyclic aromatic hydrocarbons in aqueous environmental samples. A microscale on-line supercritical fluid extraction-supercritical fluid chromatography system using carbon dioxide is employed. The extract is analysed using capillary supercritical fluid chromatography with UV detection. Detection was carried out at 254 nm. An extraction efficiency of as high as 91% was obtained for the PAHs.     

Photoperiodic regulation of parturition in the self-fertilizing viviparous polychaete Neanthes limnicola from central California

Seasonally-changing photoperiod controls the timing of parturition in the viviparous, self-fertilizing polychaete Neanthes limnicola (Johnson, 1901) from Watsonville Slough, a central California estuary. During 1987 to 1989, worms in the field gave birth mainly in the spring. Those born in late February from field-collected parents and maintained in the laboratory under in-phase photoperiodic conditions reproduced in 12 to 13 mo, under spring light-regimes. When maintained under light conditions 6 mo out of phase,they required only about 6 to 8 mo to reproduce, giving birth in the fall, but under spring light-regimes. Worms born in the laboratory in fall and then maintained in phase reproduced in the ambient spring, at 6 to 8 mo of age; those maintained out of phase took 12 to 13 mo, giving birth the following fall under spring light-regimes. Photoperiod treatments had no consistent effect on the number of young produced, and age and fecundity were only weakly correlated. Highest fecundities were in salinities of 15 to 20,with lower fecundities at higher salinities. Worms maintained in fullstrength sea water(33 S) showed abnormal development and produced very few or no young. Salinity did not affect timing of parturition. Temperature differences of 3 to 7 C° between treatments had no effect on timing of parturition or number of young produced, and marginal effects on life span. These results indicate that photoperiod regulates the timing of reproduction in N. limnicola in central California, while salinity mainly influences fecundity.     

滇池水生植物研究概述

在总结前人工作的基础上，分别从滇池大型水生植物种类、滇池水生植物群落、水生植物与水生生态环境相互关系和滇池水生植物与水生生态系统等方面，对滇池水生植物群落动态和演替及其与环境的相互关系进行分析，为滇池大型水生植物群落恢复、重建及调控提供科学依据。     

Using opportunistic green macroalgae as indicators of nitrogen supply and sources to estuaries.

Nutrient inputs to estuaries are increasing worldwide, and anthropogenic contributions are increasingly complex and difficult to distinguish. Measurement of integrated effects of salinity and nutrient changes simultaneously can help ascertain whether N sources of similar magnitude and stable isotope (sigma15N) signatures are river dominated. We used Enteromorpha spp., an opportunistic macroalga, to obtain integrated measures of salinity, nutrient supply, and nutrient source in estuaries. We outplanted cultured algae in the field along spatial gradients within three southern California estuaries for 24 hours in wet and dry seasons. Tissue was analyzed for potassium (K+) to measure osmoregulatory changes, total nitrogen to examine changes in nutrient supply, and sigma15N to assess nutrient sources. Discrete measures of water salinity correlated with tissue K+ content; however, there was significant variability in the relationship, suggesting that the algae were subject to considerable variation in salinity over a tidal cycle. Tissue total N was not always related to snapshot measures of water column dissolved inorganic nitrogen (DIN), suggesting that integrated measures may be better at capturing the temporal and spatial complexity of nutrient availability. The combination of tissue K+, total N, and sigma15N measures revealed that inflowing rivers delivered N from watershed sources to Mugu Lagoon and Carpinteria Salt Marsh, while both the inflowing river and a mid estuary source were important sources of high sigma15N N in Upper Newport Bay. These experiments revealed complex patterns of supply and sources of N and demonstrate the usefulness of macroalgal indicators over water sampling to detect these patterns.