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911.
O. Gotsis 《Marine Biology》1982,71(3):217-222
The type of interaction of selenium and mercury, and selenium and copper on the cell growth of the planktonic alga Dunaliella minuta Lerche has been studied. The results for the various selenium/mercury and selenium/copper ratios showed that: (a) although mercury and selenium inhibited the growth of D. minuta when added to its cultures separately at levels greater than their respective threshold concentrations, they had antagonistic effects towards each other when added simulataneously at the beginning of growth; prior exposure of the culture to either metal for 2 d did not alter this antagonistic action; (b) similar antagonism was observed in combinations of selenium and copper for cultures with and without prior exposure to either metal. The reasons for the Se/Hg and Se/Cu antagonism are unknown; several hypotheses concerning possible detoxification mechanisms are proposed. 相似文献
912.
Seasonal growth in Laminaria longicruris: Relations with dissolved inorganic nutrients and internal reserves of nitrogen 总被引:5,自引:0,他引:5
Observations have been made on seasonal fluctuations in dissolved inorganic nutrients, internal reserves of nitrogen and growth rates in Laminaria longicruris. The onset of winter growth in shallow-water stations (6 and 9 m) correlated well with improved dissolved nitrate conditions in the sea. During the winter, reserves of NO
3
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were accumulated by the plants and reached maximum values of 150 moles per g fresh weight in March. This represents a concentration factor of approximately 28,000 over the ambient levels, or an internal nitrogen reserve of 2.1% of the dry weight of the tissue. Depletion of this nitrogen pool followed the disappearance of the external NO
3
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with a lag period of up to 2 months. Rapid kelp growth was measured during this period. Reserves of organic nitrogen also reached maximum values in March and declined slowly throughout the summer into autumn. It is suggested that the combined inorganic and organic nitrogen reserves sustain the rapid growth rates into July and at reduced rate through the late summer. Fertilization of an experimental perimental kelp bed with NaNO3 increased the internal plant reserves of NO
3
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and produced a much improved summer growth rate. The enriched plants developed very small reserves of carbohydrate during the rapid summer growth phase.NRCC No. 15549. 相似文献
913.
Kinetic analyses were made of the stable sodium and radioactive sodium (22Na) in some tissues of the crab Carcinus mediterraneus CSRN. Fast 22Na outflux constant is increased in gills, hepatopancreas, hemolymph, digestive tract and muscles. In the reproductive organs the values of the sodium outflux constant are lower. The values of the fast outflux rates (t=20°C) of sodium amount, in the whole animal, to 22.5 M Na/g/h, in the hemolymph, to 69.3 M Na/g/h; the slow outflux rates have much lower values (0.02 to 0.13 M Na/g/h). Moulting crabs show a rate of sodium outflux 6 times greater than that of intermoulting individuals. 相似文献
914.
D. Đurka P. Pfendt B. Jovančićević O. Cvetković H. Wehner 《Environmental Chemistry Letters》2005,3(1):39-42
Free and associated bitumens were isolated by sequential extraction from Vlasina lake peat (SE Serbia) and were investigated in order to differentiate between oil pollution and natural bitumens. Four peat samples were collected at different depths, on a peat island. Gas chromatographic (GC) and gas chromatography/mass spectrometry (GC/MS) analysis revealed the presence of three markedly different bitumen fractions. Here we show that the free bitumens are representing the native peat bitumens. The two associated bitumens are mainly the products of bacterial rework of organic substance, which were then trapped by two differing mechanisms. The bitumens characteristics and association features exclude a contribution of oil pollution.Selected article from the Regional Symposium on Chemistry and Environment Krusevac, Serbia, June 2003, organised by Dr. Branimir Jovancicevic. 相似文献
915.
J.?I.?CarretoEmail author N.?G.?Montoya H.?R.?Benavides R.?Guerrero M.?O.?Carignan 《Marine Biology》2003,143(5):1013-1027
The surface abundance and species composition of phytoplankton communities were studied in a section across the continental shelf between the Río de La Plata and the oceanic waters of the Subtropical Convergence, during late spring (November 1999). Algal communities were examined using light microscopy and HPLC-derived (high-performance liquid chromatography) pigment concentrations. The CHEMTAX program was used to estimate the chlorophyll a (chl a) biomass of different algal classes. The inclusion of the most abundant members of the chl c pigment family (chl c1, chl c2, chl c3 and chl c2 monogalactosyldiacylglyceride esters) in the pigment matrix improved the CHEMTAX interpretation of field data. Using this novel approach four haptophyte populations were distinguished across the studied section, even though they had qualitatively similar pigment signatures, although one subtype lacked 19-hexanoyloxyfucoxanthin (Hex-Fuco). Five different phytoplankton assemblages, spatially segregated by the prevailing environmental conditions, were distinguished during the studied period. All of them showed a complex community structure, formed by a background of small-sized cells such as cyanobacteria, cryptophytes, haptophytes and prasinophyceans, on which diatom, cryptophyte or some haptophyte blooms were overlapped. In the estuarine assemblage, where maximum chl a concentrations where found, diatoms were always the dominant group (30–60% of total chl a), but cryptophytes (10–40%), prasinophyceans (2–20%) and dinoflagellates (2–12%) were also relevant. In the coastal assemblage diatoms were also the dominant group (35–45%), but haptophytes lacking Hex-Fuco were subdominant (20–35%). The continental shelf assemblage showed an almost exclusive dominance (90%) of haptophytes resembling the coccolithophorid E. huxleyi. Another haptophyte (Phaeocystis sp.) was dominant (75–85%) in the Malvinas Current assemblage. The Brazil Current assemblage was characterized by the codominance of cyanobacteria (45%) and haptophytes (35%). These results are discussed in relationship to the complex hydrographic features of the area.Communicated by O. Kinne, Oldendorf/Luhe 相似文献
916.
A. Jarernpornnipat O. Pedersen K. R. Jensen S. Boromthanarat S. Vongvisessomjai P. Choncheanchob 《Journal of Coastal Conservation》2003,9(2):135-146
Bandon Bay (Surat Thani Province) is one of the most productive coastal areas in southern Thailand. The Tapi River and 18
channels are the main sources of freshwater, nutrients, organic matter and sediment to the bay and the loading of freshwater
and nutrients provide essential support for the production of phytoplankton in the estuarine ecosystem. Bandon Bay is important
as natural spawning, nursery and feeding grounds for shellfish such as oysters, blood cockles, green mussels, short-necked
clams, mud crabs and shrimps, and the estuary also serves as an excellent area for mariculturing of shellfish. In fact, oysters
and blood cockles cultured in Bandon Bay are now being exported worldwide. However, Bandon Bay is also a textbook example
of overexploitation of coastal resources in the tropics including all the derived changes in the estuarial ecosystem with
severe socio-economic consequences. Hence, there is an urgent need for setting up an integrated management plant for a sustainable
use of shellfish resources in Bandon Bay. The present study attempts to integrate water quality simulation results, socio-economic
data and information on existing shellfish resource use in the process of proposing a set of sustainable management strategies
for shellfish resources in Bandon Bay. These strategies involve: (1) using water quality modeling to monitor ecological and
environmental changes in shellfish culture beds and their natural habitats in the process of setting up a master plan for
management of waste water discharge into Bandon Bay; (2) zoning of shellfish mariculture in the coastal area in order to solve
conflicts between resource users; (3) setting up a clear system for taxation of mariculture where the revenue may be used
for (4) setting up and managing mangrove strips as filters of pollution and sediment around Bandon Bay; and finally (5) it
is suggested to form a committee with members representing all relevant stakeholders plus the local government in order to
work on resolving the existing and potential future conflicts over resource usage in Bandon Bay. This methodology may be seen
as an important contribution towards a Bandon Bay sustainable management approach, based on the principles of integrated coastal
zone management because it is science-based and takes into consideration the needs and perceptions of people involved in coastal
resource extraction. 相似文献
917.
We describe two applications of a recently introduced system for very precise, continuous measurement of water oxygen saturation. Oxygen microoptodes (based on the dynamic fluorescence quenching principle) with a tip diameter of ~50 µm, an eight-channel optode array, an intermittent flow system, and online data registration were used to perform two types of experiments. The metabolic activity of Antarctic invertebrates (sponges and scallops) was estimated in respiration experiments, and, secondly, oxygen saturation inside living sponge tissue was determined in different flow regimes. Even in long-term experiments (several days) no drift was detectable in between calibrations. Data obtained were in excellent correspondence with control measurements performed with a modified Winkler method. Antarctic invertebrates in our study showed low oxygen consumption rates, ranging from 0.03-0.19 cm3 O2 h-1 ind.-1. Oxygen saturation inside living sponge specimens was affected by flow regime and culturing conditions of sponges. Our results suggest that oxygen optodes are a reliable tool for oxygen measurements beyond the methodological limits of traditional methods. 相似文献
918.
Abstract: Populations of Marianas fruit bats, Pteropus mariannus, were surveyed on each of the 15 Mariana Islands in 1983–1984. It is estimated that a minimum of 8,700–9,000 fruit bats occur in the archipelago, with about 8245% of these bats found on the nine northernmost and largely uninhabited islands. The islands of Anatahan, Pagan, and Agrihan had the largest populations, with minimum population estimates of 3,000, 2,500, and 1,000 bats, respectively. Smaller populations of about 400–1,000 fruit bats occurred on Asuncion, Guam, Rota, and Guam. The remaining is-ands in the archipelago were each estimated to have fewer than 125 bats. Population densities of fruit bats were highest on islands with little bunting but were generally much lower on human-inhabited islands where bunting was common. Quantity and quality of existing habitat were other important factors regulating the size of fruit bat populations in the Marianas. Increased enforcement of existing laws protecting bats and a public awareness program are important tasks needed to conserve and manage fmit bats in the Marianu Islands. The census techniques used in this study may be applicable to other fypes of colonial, mobile wildlife that inhabit islands. 相似文献
919.
Summary Home ranges, areas of intensive use, and locations of nest sites were determined for female Columbian ground squirrels and their daughters over seven years from a low-density population in southwestern Alberta. Adult females usually retained similar home ranges from year to year. However, they moved their nest sites more often than expected in years when a yearling daughter was present. Core areas and centres of activity also changed when the nest site was moved. Most daughters settled on their natal areas. The relinquishing of nest sites by females to their daughters is seen as a form of parental investment. 相似文献
920.