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121.
Three procedures for the extraction of coral lipids were compared and a rapid and effective method for future use is suggested. This method was used to measure the lipid content of the branching coral Porites porites (Pallas) and the massive corals Montastrea annularis (Ellis and Solander) and Siderastrea siderea (Ellis and Solander) during July and August 1991. P. porites and M. annularis were sampled on two fringing reefs, each characterised by different water quality affecting light transmission, and at depths of down to 30 m on a barrier reef on the west coast of the island. m. annularis contained, on average, 29% of dry weight as lipid, and there were no significant differences in lipid levels between corals sampled on either fringing reef at 3 and 6 m, or between fringing reefs and the barrier reef at 13, 20 or 30 m depth. Five samples were also taken from a single massive colony of S. siderea at 3 m on a fringing reef and at 13, 20 and 30 m depth on the barrier reef. Values for lipid ranged from 26 to 35% of dry tissue weight. P. porites from 3 and 6 m depth on both fringing reefs contained the same amount of lipid (11% of dry tissue weight). However, at 13 m depth on the barrier reef this coral contained significantly less lipid (8.5% of dry tissue weight). This difference may be attributable to a higher nutritional intake by P. porites on the fringing reefs. 相似文献
122.
The possible involvement of calmodulin-dependent processes in the control of Na+ and Cl- transport pathways has been investigated on isolated, perfused preparations of salt-transporting posterior gills of the euryhaline Chinese crab Eriocheir sinensis (collected near Emden, Germany in autumn 1990). The anti-calmodulin phenothiazine drugs Chlorpromazine and Trifluoperazine induced depolarization of the transepithelial potential only when added to the serosal bathing saline (socalled in). This effect is best interpreted by assuming a disturbance of the conductive Cl- pathways located at the baso-lateral side of the epithelium. In agreement with that conclusion is the fact that Trifluoperazine inhibits the Cl- transepithelial influx. Trifluoperazine also induces inhibition of the Na+ influx when added either to the incubation (out) or to the perfusion (in) medium. These results indicate inhibitory effects of the anticalmodulin drug on both the Na+/K+ pump and leak system located at the serosal side and on the Na+/H+ exchange located at the apical side of the epithelium. 相似文献
123.
Comparative restriction-fragment analysis was used to analyze the nuclear ribosomal DNA, and alcohol dehydrogenase-1 loci of Zostera marina L., for variation within and among populations. Eelgrass is a perennial marine flowering plant that is widespread and ecologically significant throughout the temperate northern hemisphere. A chemical method was developed to obtain restriction-quality DNA without CsCl fractionation from experimentally relevant quantities of seagrass tissues (0.5 to 1.0 g). The yield was 25 g g-1 fresh weight. The three morphologically distinct forms of Z. marina from disjunct populations examined in this study were found to be genetically distinct; morphologically similar populations were indistinguishable genetically. Genetic distinction also correlated with habitat depth, as subtidal and intertidal populations were clearly divergent. Homologous probes for the 17S and 28S ribosomal DNA genes were used to map 24 restriction sites on the rDNA repeat of Z. marina, which was determined to be about 14 kb in length. At least 1 length mutation and 5 restriction-site changes were identified that distinguished Z. marina populations from San Diego and Monterey Bay (Del Monte Beach) from Z. marina populations from Elkhorn Slough and Tomales Bay. Estimated sequence variation (100×p) between eelgrass populations ranged from 0.00 to 0.69. Individual plants were observed to contain as many as four different rDNA-repeat length variants. The mean number of rDNA-repeat length variants per individual in Z. marina was about two. Intrapopulation variation in rDNA-repeat type was observed in only one individual from the Tomales Bay population. 相似文献
124.
Feeding rates and diel vertical migration of copepods near South Georgia: comparison of shelf and oceanic sites 总被引:1,自引:0,他引:1
Seventeen Longhurst Hardy Plankton Recorder profiles were taken over a diel cycle in January 1990 to study the feeding of four major copepods over the South Georgia shelf. Ontogenetic changes in vertical migration were followed and feeding cycles determined by gut fluorometry for Calanoides acutus Stage CV, Calanus sinillimus CV and CVI, C. propinquus CV and Rhincalanus gigas CV and CVI. In common with a neighbouring oceanic site visited two weeks later and reported elsewhere, all four species had a diel cycle of feeding and migration. The vertical distributions of C. simillimus (all stages), R. gigas (nauplii) and Euphausia frigida (postlarvae) were similar at both sites, the night being spent within the chlorophyll maximum at 15 to 30 m. However, the biomass dominants, C. acutus and R. gigas, dwelt below the chlorophyll maximum, about 30 m deeper than their oceanic counterparts. Unlike the oceanic site, feeding at the shelf site was not restricted to darkness, but increased 6 to 10 h before nightfall and finished at dawn; the intervening period coincided with sinking and digestion. Daylight feeding may have been induced by the shorter night, lower light levels or greater food requirements at the shelf site, despite planktonic predators being over three times more abundant. Daily ration estimates for R. gigas at both sites were only 2% body carbon per day. These low values contrast with its smaller competirors, whose rations were in the range 5.6 to 27%. 相似文献
125.
A unique type of integumental formation is described for several members of the copepod family Pontellidae. This surface attachment structure (SAS) consists of a mass of fine setules arranged in two semicircles on a flattened area of the anterodorsal surface of the cephalosome. Using transmission electron microscopy, the SAS was shown to be continous with the cuticle and not linked to chemo- or mechanosensory cells; its function is purely mechanical. This structure is probably an energy-saving means for these large and heavy neustonts to stay attached to the surface film. The SAS is species-specific and may thus be of potential importance to the systematics and phylogeny of the Pontellidae, in the same manner as integumental pores and sensilla, which form patterns characteristic of several copepod families and genera. 相似文献
126.
Inorganic nitrogen metabolism in blue light was studied for the green algaUlva rigida C. Agardh collected in the south of Spain (Punta Carnero, Algeciras) in the winter of 1987. NH4
+ has been reported to inhibit NO3
- uptake; however,U. rigida showed a net NO3
- uptake even when the NH4
+ concentration of the external medium was three or four times greater than the concentration of NO3
-. NO3
- uptake rates were similar in both darkness and in blue light of various photon fluence rates (PFR) ranging from 17 to 160 mol m-2 s-1. Since NO3
- uptake is an active mechanism involving the consumption of ATP, respiratory metabolism can provide enough ATP to maintain the energetic requirement of NO3
- transport even in darkness. In contrast, NO3
- reduction inU. rigida was highly dependent on the net photosynthetic rate. After 7 h in blue light, intracellular NO3
- concentrations ([NO3
-]
i
) were higher in specimens exposed to intensities below the light compensation point (LCP) than in those incubated at a PFR above the LCP. When PFR is below the light compensation point, NO3
- reduction is low, probably because all the NADH produced by the cells is oxidized in the respiratory chain in order to produce ATP to maintain a steady NO3
- transport rate. The total nitrogen (TN) and carbon (TC) contents decreased from darkness to 33 mol m-2 s-1 in blue light. In this range, catabolic processes prevailed over anabolic ones. In contrast, increases in TN and TC contents were observed above the light compensation point. The C : N ratio increased with light intensity, reaching a stable value of 17 at 78 mol m-2 s-1 in blue light. Intracellular NO3
- concentration and NO3
- reduction appear to be directly controlled by light intensity. This external control of [NO3
-]i and the small capacity ofU. rigida to retain incorporated NO3
-, NO2
- and NH4
+ ions may explain its nitrophilic character. 相似文献
127.
Previous epidemiological studies have shown that dental fluorosis is endemic in the lowland, dry zone of Sri Lanka, which is considered to be an area in which excessive quantities of fluorides are present in the drinking water supplies. It has been found that kaolinitic clay forms a suitable raw material in the defluoridation of water.It is shown that there is a noticeable effect of selenium and media pH on the reactions involved in the interaction of fluoride with clay. In this study, 1 mM fluoride solutions containing SeO
3
2–
(selenite) concentrations of 0 mM, 0.1 mM, 0.5 mM and 1 mM were used in the reactions with kaolinitic clay. The effect of pH was monitored in the range 4 to 8. It was observed that fluoride adsorption was maximum at a pH of 5.6 without either SeO
3
2–
or SeO
4
2–
, the adsorption capacity being 15.2 mol F– g–1 clay. However, when the SeO
3
2–
concentration was increased up to 0.5 mM at this optimum pH, the adsorption capacity reduced to 12.8 mol F– g–1 clay. Monitoring of the effect of SeO
4
2–
and media pH on fluoride adsorption showed that when the SeO
4
2–
concentration increases from zero to 0.1 mM, there is a reduction of fluoride adsorption capacity. However, when the SeO
4
2–
concentration is further increased from 0.1 mM to 1.0 mM, there was an increase in the fluoride adsorption capacity, indicating a more consistent effect of SeO
3
2–
on fluoride-kaolinitic clay interaction than SeO
4
2–
.Fluoride concentrations in drinking water supplies have a marked effect on dental health and the geochemistry of selenium appears to play an important role in the geochemical mobility of fluoride ions. 相似文献
128.
Howells G Dalziel TR Turnpenny AW 《Environmental pollution (Barking, Essex : 1987)》1992,78(1-3):131-139
This project has been successful in meeting its objectives in terms of demonstrating that catchment liming techniques can restore acidified waters to conditions suitable for fish populations for relatively long periods. This improvement in conditions has extended to the inlet stream, which provides vital fish spawning and nursery areas, which are difficult to treat effectively be other means in remote locations. The project has also provided an assessment of the effectiveness of differing rates and modes of lime application, which suggest that only quite restricted parts of a catchment require treatment. This not only maximizes the cost-effectiveness of the treatments, but also helps to minimize any side-effects on, for example, moorland vegetation. The biological monitoring programme at Loch Fleet has also provided an assessment of the overall ecological consequences of adding limestone to naturally acidic and calcium-deficient ecosystems. 相似文献
129.
Ammonia concentration gradients above a Douglas fir canopy were measured from 16 August to 31 December 1989 by two automated high-precision thermodenuders at the location Speulderbos in The Netherlands. Concentration gradients were used to calculate the dry deposition flux of ammonia via flux-gradient theory. Meteorological data were obtained from a nearby tower. Ammonia concentrations were highly variable with highest values during the night. Concentration gradients were very small during daytime and quite large at night. Median values of the calculated deposition flux and deposition velocity were 0.1 microg m(-2) s(-1) and 3.2 cm s(-1) respectively (N=1624). 相似文献
130.
Three simple steady-state water-chemistry models are used to calculate critical loads of sulfur for lakes in Finland. Because of the high concentrations of organic matter in Finnish lakes, the influence of organic anions on the calculation of critical loads has been given special attention. The first two methods are well known ion-balance methods which have been used in many previous lake-acidification studies. The third method, developed for this study, includes the numerical solution of equilibrium equations for organic anions, inorganic carbon species and inorganic monomeric aluminum. The original pH and aluminum concentration of the lakes are estimated with this model, and a method to estimate the original acid neutralizing capacity (ANC) by simulating a Gran-titration is also tested on the lake data. Uncertainty in the predictions is estimated by varying the most critical model parameters. 相似文献