Changes in microcystin content and environmental parameters over the course of a toxic cyanobacteria bloom in a hypertrophic regulated river, South Korea

Cyanobacterial blooms and associated microcystins in hypertrophic stagnant West-Nakdong River were investigated at weekly intervals from April to August, 1999. Microcystis spp. accounted for over 85% of the numeric abundance of total phytoplankton. Microcystins were present in the blooms sampled between May and August. The peak of total microcystin (microcystin-LR + -RR) levels (maximum level; 612 microg g(-1)) was detected in the initial stage of the bloom (mid May), at the same time as high N/P ratio and high Microcystis biomass. This study indicated that total microcystins of this regulated river was positively correlated to Microcystis biomass, absolute nutrient concentration and TN/TP ratio.     

Simultaneous sorption of lead and chlorobenzene by organobentonite

Clays or organoclays have been used as a barrier to prevent the transport of hazardous contaminants in landfills. However, clays are known to effectively sorb mostly inorganic contaminants, while organoclays are mainly used for organic contaminants. Since the organoclays are basically clay particles modified with cationic surfactants, there might exist an optimal coverage of cationic surfactant on the clay particles to sorb both inorganic and organic contaminants. In order to determine the optimal mass of cationic surfactants on the bentonites, sodium bentonites were treated with various ratios of hexadecyltrimethylammonium (HDTMA) to bentonites. Chlorobenzene and lead were selected as representative contaminants. When either chlorobenzene or lead exists as a single contaminant, chlorobenzene sorption increased with increasing HDTMA to bentonite ratios, and lead sorption decreased with increasing HDTMA to bentonite ratios. Sorption of chlorobenzene was a function of HDTMA coverage on the bentonites, while lead sorption was much more influenced by the initial lead concentration rather than the mass of HDTMA added to the bentonites.     

Estrogenic effects of phenolic compounds on glucose-6-phosphate dehydrogenase in MCF-7 cells and uterine glutathione peroxidase in rats

In this study, we tested phenolic compounds such as bisphenol A (BPA), 4-nonylphenol (NP), 4-octylphenol (OP) and 4-propylphenol (PP) by using glucose-6-phosphate dehydrogenase (G6PD) in estrogen sensitive human breast cancer cells (MCF-7 cells) and glutathione peroxidase (GPx) in female immature Sprague-Dawley (SD) rats. This study was designed to investigate whether phenolic compounds have estrogenic effects in these useful screening methods for endocrine disruptors. We chose 6 h as the incubation period for the G6PD assay through a preliminary experiment using 17beta-estradiol (E2). Above the concentration of 1 x 10(-8) M, BPA significantly increased the G6PD activity in a concentration-dependent manner, relative to the control. NP (over the concentration of 1 x 10(-9) M) also enhanced the G6PD activity by about 1.8 times that of the control. OP produced weaker effects on G6PD than NP, and showed a tendency to increase the G6PD activity. PP did not affect the G6PD activity. These results show that BPA and NP have the effect of enhancing G6PD activities in MCF-7 cells. In the in vivo GPx assay, both BPA and E2 significantly increased the uterus wet weights and dramatically enhanced uterine GPx activities in immature female rats in a dose-dependent manner. Treatment with NP (500 mg/kg/day) increased significantly both the uterine GPx activity and the uterus wet weights in immature female rats. OP (500 mg/kg/day) also caused a significant increase in uterine GPx activity, but had no effect on the uterus wet weights. This finding indicates that the change in uterine GPx activities could be a more sensitive parameter than that of uterus wet weights in immature rats. This study implies that phenolic compounds have a weak estrogenic effects.     

The digestibility of waste activated sludges.

Laboratory digestion studies using waste activated sludges (WAS) were conducted to compare the digestion performance between anaerobic and aerobic processes. Nine samples of WAS from seven wastewater treatment plants were collected and batch-digested under both anaerobic and aerobic conditions for 30 days at 25 degrees C. The cation content of wastewater (both floc and solution phases) and solution biopolymer (protein and polysaccharide) was measured before and after digestion and compared with volatile solids destruction data. The study revealed that each digestion process was associated with a distinct biopolymer fraction, which accounted for differences in volatile solids reduction under anaerobic and aerobic conditions. The anaerobic digestion data showed strong correlations between soluble protein generation, ammonium production, percent volatile solids reduction, and floc iron (Fe). These data suggest that the amount of volatile solids destroyed by anaerobic digestion depends on the Fe content of floc. In aerobic digestion, polysaccharide accumulated in solution along with calcium and magnesium. For aerobic digestion, correlations between divalent cation release and the production of inorganic nitrogen were found. This implies that divalent cation-bound biopolymer, thought to be lectin-like protein, was the primary organic fraction degraded under aerobic conditions. The results of the study show that the cation content in wastewater is an important indicator of the material that will digest under anaerobic or aerobic conditions and that some of the volatile solids will digest only under either anaerobic or aerobic conditions.     

Feeding ecology and interannual variations in diet of larval jack mackerel,Trachurus declivis (Pisces: Carangidae), from coastal waters of eastern Tasmania

Changes in the biochemical composition of the digestive gland and in the proteins of the mantle muscle of Sepia officinalis L, collected in September 1989 from the Ria de Vigo (northwest Spain), were measured during periods of 2, 4, 10 and >53 d starvation. The digestive gland lost weight faster than the rest of the body throughout the whole period of starvation. In the digestive gland, carbohydrate and protein contents did not change during starvation; however, lipid levels decreased significantly after 53 d. Phospholipid content increased during longterm starvation. The content of free fatty acids rose after 16 d. Sterols, diacylglycerylethers, triacylglycerols and carotenoids contents did not change significantly. Of the total fatty acids, 18:0, 20:2n6, 20:4n6 and the monounsaturated moieties were preferentially consumed; others, such as 22:5n3, 22:6n3 and 16:4n1, were selectively retained. In the mantle muscle, water content increased and total protein content decreased. The myofibrillar proteins decreased after 53 d starvation, whereas the sarcoplasmic fraction did not change and the stromatic proteins increased. No changes were observed in the electrophoretic patterns of sarcoplasmic and myofibrillar proteins. The digestive gland of S. officinalis does not seem to be an important reserve organ during long-term starvation, but does seem to be important during shortterm starvation.     

Factors controlling spatial distribution of the sea cucumber Psolus chitonoides: Settling and post-settling behavior

Substratum selection experiments were carried out in situ with larvae of the holothurian Psolus chitonoides Clark in the rocky subtidal of the San Juan Islands, Washington. The experiments indicated, in agreement with laboratory findings, that pentactula larvae settle gregariously, either on the adult, or (when the bivium is obscured by epizooites) by clustering around the margin of the adult sole. Late larvae and early juveniles are strongly photonegative. Following metamorphosis, juveniles migrate from the adults into nearby shaded habitats, where they may take up residence indefinitely. Although adults retain the capacity to move, they relocate only when their living conditions become unsuitable; in most circumstances they are effectively sessile. Small-scale spatial pattern of the adults, which was documented quantitatively on subtidal rock walls, boulders and cobbles, correlates well with microtopographical features. The aggregation observed in the field is primarily due to post-settling migration rather than larval substratum choice at settlement.     

Documentation of selected constructs and parameter values in the aquatic model cleaner

Process representations critical to the phytoplankton and zooplankton submodels are described. These include constructs for: light- and nutrient-limitations and their interaction, temperature, consumption, and population-age structure. Values for key parameters are documented with reference to the literature on aquatic ecology and ecological modelling. Time-course relationships of the processes affecting the phytoplankton, zooplankton, phosphorus and nitrogen compartments are presented and discussed. These serve as additional documentation and are an important result of modelling synthesis.     

Morphological and genetic evidence for vicariance and refugium in Atlantic and Gulf of Mexico populations of the hermit crab Pagurus longicarpus

The number and wide variety of southeastern United States marine taxa with significant differentiation between Gulf of Mexico and Atlantic Ocean populations suggests that these taxa may have experienced major vicariance events, whereby populations were subdivided by geological or ecological barriers. The present study compared variation in morphology, allozymes, and mtDNA in Gulf of Mexico and western Atlantic populations of the longwrist hermit crab Pagurus longicarpus Say collected during 1997 and 1998. Combined Atlantic populations had significantly fewer denticles on the second segment of the third maxilliped than did Gulf of Mexico populations, and the mean ratio of dactyl length to propodus length was significantly greater in the Atlantic crabs than in the Gulf of Mexico crabs. Allozyme allele frequencies at three loci showed genetic differentiation between a Gulf of Mexico population and two Atlantic populations. Analysis of mtDNA sequence data revealed a clear reciprocal monophyly between Gulf and Atlantic populations, with an estimated divergence age of ~0.6 million years ago. This estimated age of divergence is significantly more recent than an age previously estimated for its congener Pagurus pollicaris (~4 million years ago), suggesting that species with a similar genetic break between Gulf and Atlantic populations may not necessarily share an identical history. Surprisingly, there is evidence of geographic subdivision within Atlantic populations of P. longicarpus along the east coast of North America. This differentiation is especially strong between Nova Scotia and southern populations, suggesting that the Nova Scotia population may represent survivors from a northern refugium during the last glacial maximum.     

First trimester diagnosis of cystinosis using intact chorionic villi

Cystinosis was diagnosed in the first trimester of pregnancy by studies of uptake and retention of [³⁵S]-cystine by intact biopsy samples of chorionic villi. The diagnosis was confirmed by similar studies on cell cultures of villi and fetal skin fibroblasts.