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111.
We present methods developed for the small-sizedDaphnia species,D. galeata, D. hyalina, D. cucullata, and their hybrids, which facilitate the use of DNA variation in population studies. Described are large-scale production of material from single genotypes ofDaphnia and subsequent extraction of total DNA. The average DNA yields ranged between 6 µg per gram wet weight (D. cucullata) and 12 µg per gram wet weight (D. galeata). For comparison, the large-sized speciesD. pulex was tested and yielded an average of 28 µg DNA per gram wet weight. The DNA isolated in this manner lends itself well to molecular genetic techniques suited for population studies.Reprint requests to B. Streit. 相似文献
112.
The zooplankton community of the Mpenjati Estuary, a South African temporarily open/closed system 总被引:2,自引:0,他引:2
The aim of this study was to examine spatial and temporal variability in zooplankton abundance and biomass, both during the closed (dry season) and open (wet season) phases of the Mpenjati Estuary, South Africa. On average, nighttime abundance values were 1–3 orders of magnitude higher than daytime values. A total of 51 and 36 zooplankton taxa were identified during the open and closed phases, respectively. The estuarine species Pseudodiaptomus hessei, Acartia natalensis and Gastrosaccus brevifissura dominated the assemblage during both phases. During the open phase marine zooplankton species entered the estuary and increased the zooplankton species diversity. At the same time, the biomass of the estuarine zooplankton species decreased substantially due to scouring of the sediment, increase in salinity and turbulence, and possibly also in grazing pressure. Conversely, during the closed phase the zooplankton diversity decreased, since no marine organisms entered the estuary, but the biomass of typical estuarine species increased due to the stability of the estuary. The fluctuations in the zooplankton community structure between the closed and the open phases suggest that the opening and the closing of the estuary are very important processes in determining the food web of the estuary. 相似文献
113.
Abstract. The estuarine ecosystem of the Amvrakikos Gulf, a semi-enclosed embayment of the Ionian Sea, was surveyed at 9 stations in June, 1980. Quantitative and qualitative relationships among the phytoplanktonic, zooplanktonic and benthic populations were examined and related to environmental parameters. It was found that quantitative maxima of each of the three components occurred at different stations. When stations were grouped according to a similarity index of each community, it could be shown that the stations were very similar with regard to phytoplankton and slightly less similar with regard to zooplankton. The stations differed considerably as far as the benthos is concerned. The phytoplankton also exhibited a lower species diversity (0.08-0.82 bits-indiv.-1 ) than the zooplankton (1.08-2.10 bits indiv.-1 ) and the benthos (0.85-5.06 bits indiv.-1 ). Differences in salinity among stations showed no significant correlation with the abundance or species diversity of phytoplankton, zooplankton or benthos. 相似文献
114.
We measured the ammonium excretion, phosphate excretion and respiration rates of the scyphomedusa Aurelia aurita from Ondo Strait, in the central part of the Inland Sea of Japan, at 28 and 20°C. The rates measured at 28°C were converted
to those at 20°C using the Q10 values, i.e. 1.56, 1.57 and 2.80, for ammonium excretion, phosphate excretion and respiration rates, respectively. The composite
relationships between metabolic rates and wet weight of a medusa (WW, g, range 11–1330 g) at 20°C were expressed by the following allometric equations. For ammonium excretion rate (N, μmoles N medusa−1d−1): N = 0.497WW
1.09, phosphate excretion rate (P, μmoles P medusa−1d−1): P = 0.453WW
0.84, and respiration rate (R, μmoles O2 medusa−1d−1): R = 96.9WW
1.06. Mean O:N ratios (i.e. atomic ratios of 16.9 and 11.0 at 28 and 20°C, respectively) indicated that the metabolism of A. aurita medusae was protein-dominated. These metabolic parameters enabled us to estimate the nitrogen and phosphorus regeneration
rates of an A. aurita medusa population typical of early summer in the Ondo Strait (means of water temperature, medusa individual weight and population
biomass: 20°C, 200 g WW and 50.8 g WW m−3, respectively). Regenerated nitrogen and phosphorus were equivalent to 10.0 and 21.6% of phytoplankton uptake rates, respectively,
nearly twice that estimated for mesozooplankton, demonstrating that A. aurita medusae are key components of the plankton community, influencing the trophic and nutrient dynamics in the Ondo Strait during
early summer. 相似文献
115.
根据1990年春季至1991年冬季采自南日岛海域浮游动物样本,初步鉴定出98种浮游动物和12类浮游幼虫。桡足类种类和数量均占优势。精致真刺水蚤、中华哲水蚤、肥胖箭虫、中华假磷虾和短尾类氵蚤状幼虫为优势种。本文报道了浮游动物总生物量,总个体数和种类数的季节分布及平面分布,讨论其分布与环境的关系。 相似文献
116.
117.
本文分析了Corexit 9527分散剂和中国胜利原油对海洋实验生态系中浮游动物群落的影响,得出的主要结论是:1.单独的Corexit 9527对草食性桡足类的生长发育稍有抑制作用,但种群可得恢复和发展,对肉食性桡足类及其他各类浮游动物没有影响;2.Corexit 9527和原油的混合物对所有类别浮游动物均有极大的抑制作用,它导致种群的迅速缩小且无法得以恢复。 相似文献
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