共查询到20条相似文献,搜索用时 31 毫秒
1.
We use a conceptual mathematical reaction-diffusion model to investigate the mechanisms of spatial structure formation and complex temporal dynamics of plankton in a heterogeneous environment. We take into account basic trophic interactions, namely, "prey-predator" interactions between phytoplankton, zooplankton, and fish in upper layers of natural waters. We consider plankton as a passive contaminant in turbulent waters. We show that plankton structure formation can result from the difference in phytoplankton growth rate in neighboring habitats. Phytoplankton and zooplankton biomass is shown to undergo both regular and chaotic oscillations. The fish predation rate substantially affects the spatial and temporal dynamics of plankton in a heterogeneous environment. 相似文献
2.
The veliger larva of Hydrobiu ulvue (Pennant) from the west coast of Wales is described and illustrated from veligers hatched in the laboratory and collected in plankton samples. The larvae are planktotrophic and it is estimated that the pelagic phase is of about four weeks duration. In terms of density they form an important constituent of the plankton of inshore waters. The veliger larva of Littorina littoreu (L.) is also described and illustrated, and it is suggested that some of the conflicting reports on the length of the pelagic phase of H. ulvae result from confusion in indentification of the larvae of these two species. 相似文献
3.
Thunell R.; Pride C.; Ziveri P.; Muller-Karger F.; Sancetta C.; Murray D. 《Journal of plankton research》1996,18(11):2017-2026
Distinct increases in plankton productivity occur annually inthe Gulf of California and are related, at least in part, towind-driven changes in upper-ocean conditions. In particular,a rapid increase in plankton shell fluxes occurs in late fall(November), and is associated with a shift to northerly windsand cooling of surface temperatures that induce mixing of theupper ocean. The observed succession in the phytoplankton isattributed to this destabilization of surface waters and mayreflect the ability of different groups to rapond to varyingsurface water nutrient levels. The unraveling of such relationshipsbetween plankton production and hydrographic conditions is criticalto improving our ability to reconstruct quantitatively pastclimates. 相似文献
4.
Carlos Eduardo Falavigna da Rocha 《Hydrobiologia》1984,119(2):107-117
Four new species of Halicyclops are described and figured from plankton samples of the brackish waters of Pomonga River, Sergipe State (NE Brazil). The ornamentation of the median apical setae of the furcal rami is proposed as useful diagnostic character for species distinction. 相似文献
5.
Eutrophication, often resulting from human activity, is a serious threat to aquatic communities. Theoretical analysis of this phenomenon, based on conceptual mathematical models, leads to controversial predictions known as Rosenzweig's paradox of enrichment. At the same time, field observations demonstrate that real plankton communities exhibit various mechanisms of self-regulation which can buffer negative effects of enrichment. In this paper, we study potential effects of zooplankton vertical migration on stability of plankton systems functioning. We consider an intrinsically unstable plankton model, which is characterized by an unlimited phytoplankton multiplication and population oscillations of increasing amplitude, and investigate whether vertical migrations of zooplankton can stabilize such a system at low plankton densities. By means of developing two different models accounting for different ecological situations, e.g. deep waters and shallow waters, we show that vertical migrations of zooplankton can result in stabilization of eutrophic plankton systems. Thus, we show that this mechanism, rarely taken into account in models of plankton dynamics, may be important for resolving the paradox of enrichment in plankton communities. 相似文献
6.
Diurnal variation in a fish pond in Seoni,India 总被引:3,自引:3,他引:0
Mahendra N. Verma 《Hydrobiologia》1967,30(1):129-137
Summary The diurnal variation in the water chemistry and the plankton of Budhwari tank Seoni, India, which is a highly productive tank, has been studied after the monsoon. Not much variation from the other tropical waters in the chemistry has been noted. The plankton showed a little diversion from the normal behaviour in tropical fresh waters. 相似文献
7.
8.
Four previously unknown species of hydromedusae are described from plankton samples collected during oceanographic cruises undertaken along the south-western coast of Africa. The Anthomedusa Bythotiara capensis sp.n., known from a single specimen, was found in shallow waters of the Cape region (South Africa). The Leptomedusa Margalefia intermedia gen. et sp.n. collected in Namibian waters, possesses desmoneme cnidocysts. This category of cnidocysts is previously unreported in the Leptomedusae, but is common in Anthomedusae and in the limnomedusan family Proboscidactylidae. Margalefia seems to occupy a position intermediate between the families Tirannidae and Laodiceidae. Two species of Limnomedusae, Aglauropsis edwardsii sp.n. and Proboscidactyla menoni sp.n. were frequent at several stations in Namibian waters between depths of 50 m and the surface. 相似文献
9.
V. P. Semenchenko 《Contemporary Problems of Ecology》2012,5(4):386-390
The ecological risk of changes in the content of essential polyunsaturated fatty acids (PUFAs) in plankton of lakes due to
global warming is assessed. The analyzed hazards are temperature, dissolved phosphorus and nitrogen, and the phyto- and zooplankton
structure. The main risks are related not only to the temperature increase, but indirect effects of warming. The critical
link in PUFA risk assessment is the phytoplankton structure due to the particularly favorable growth conditions for cyanobacteria
in nutrient rich waters in shallow lakes and reservoirs. 相似文献
10.
The NW Black Sea is an area with peculiar hydrological, hydrochemicaland biological features (river plume dynamics, coastal upwelling,intense eutrophication, blooms algae). We determined the abundanceand distribution of the two major groups of Archaea (Crenarchaeotaand Euryarchaeota) in three contrasting sites of the NW BlackSea from May to August 2004 to estimate the contribution ofnon-extremophilic Archaea to the coastal prokaryotic plankton.Using catalyzed reporter deposition-fluorescence in situ hybridization,Euryarchaeota were found to be particularly prominent (1122%of total prokaryotic plankton) in the low-salinity waters duringlate-spring and summer, whereas Crenarchaeota contributed only5% to the prokaryotic community in these waters. The abundanceof Crenarchaeota was highest in nutrient- and particle-richwaters and lowest in offshore Black Sea surface waters. Theseresults confirm recent studies on the distribution of planktonicArchaea with Euryarchaeota dominating the archaeal communityin surface waters. Statistical analyses indicated significantcorrelations between crenarchaeotal abundance, ammonia and nitrateconcentrations at each sites. Our data show that the archaealplankton constitute an important and dynamic component of theprokaryotic plankton in the coastal oxygenated waters of theNW Black Sea and might play a significant role in the nitrogencycle. 相似文献
11.
M. Kaliyamurthy 《Hydrobiologia》1973,41(1):3-11
Marked sectoral and seasonal variations were observed in the transparency of the waters of the Pulicat lake.No tidal effect was noticed on the turbidity of the waters.The transparency of the waters in relation to the production of plankton has been discussed. 相似文献
12.
Fergus C. O'Hara 《Hydrobiologia》1984,111(2):103-105
A new automated plankton sampler is described that collects, compartmentalizes and preserves up to twelve individual samples, from any depth up to 400 meters, in fast or slow flowing waters. The unit combines the already well established features characteristic of other modern samplers but offers many distinct advantages. The O'Hara sampler features a novel fully automated self generating flow through system that is electronically preset by the operator, and upon submergence need not be retrieved for a period up to several days. The unit is simple in its design and challenging in its applications for use in pure and applied scientific research. 相似文献
13.
INGGARD ARNE BLAKAR 《Freshwater Biology》1978,8(6):533-537
SUMMARY. A lightweight, free-flushing water and plankton sampler constructed of readily available, inexpensive material is described. Easily interchangeable tubes of varying volumes allow sampling flexibility. The sampler is activated by a messenger and is shut by two plastic funnels. For analyses in highly stratified waters, the sampler can be adjusted into the horizontal position. Several samplers may be tripped in series. The sampler has proved a versatile and reliable instrument in ecological studies.
The tripping mechanism may also be used to release reversing thermometers and closing nets. 相似文献
The tripping mechanism may also be used to release reversing thermometers and closing nets. 相似文献
14.
Based on plankton samples collected from 100–0 m depths in the years 1979–1980, the duration of biological seasons was determined and the seasonal succession of plankton was followed in five surface water modification zones: Kuril, Subarctic, Subtropical transformed, Oyashio (cold), and Soya (warm). The bloom of phytoplankton off the southern Kuril Islands begins in the months March–May and continues until June in waters of warm currents and until September in cold waters. Succession rates vary among the zones. In cold-water zones, the change in the plankton community from the spring to the summer state occurs about half a month later than in warm waters. The reason for this lag is the slower sea surface heating and the later stratification in cold-water zones. 相似文献
15.
Stomp M Huisman J Vörös L Pick FR Laamanen M Haverkamp T Stal LJ 《Ecology letters》2007,10(4):290-298
Hutchinson's paradox of the plankton inspired many studies on the mechanisms of species coexistence. Recent laboratory experiments showed that partitioning of white light allows stable coexistence of red and green picocyanobacteria. Here, we investigate to what extent these laboratory findings can be extrapolated to natural waters. We predict from a parameterized competition model that the underwater light colour of lakes and seas provides ample opportunities for coexistence of red and green phytoplankton species. To test this prediction, we sampled picocyanobacteria of 70 aquatic ecosystems, ranging from clear blue oceans to turbid brown peat lakes. As predicted, red picocyanobacteria dominated in clear waters, whereas green picocyanobacteria dominated in turbid waters. We found widespread coexistence of red and green picocyanobacteria in waters of intermediate turbidity. These field data support the hypothesis that niche differentiation along the light spectrum promotes phytoplankton biodiversity, thus providing a colourful solution to the paradox of the plankton. 相似文献
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17.
A. V. Krylov A. V. Romanenko D. V. Trankvilevsky M. I. Chubirko J. I. Stepkin 《Biology Bulletin》2011,38(10):985-991
The differences in the bacterio- and zooplankton communities of small- and medium-sized watercourses classified on the specifics
of natural processes and consequences of anthropogenic activity in the territory of Voronezh oblast are described. Soil erosion,
along with contamination of surface waters by industrial and municipal sewage and pesticides, has the greatest impact. The
water current velocity, contamination by organic matter and nutrients, and the extent of macrophyte overgrowth affect the
quantitative and qualitative composition of plankton in local parts of the studied watercourses. 相似文献
18.
K. Krishnamurthy W. Damodara Naidu R. Santhanam 《International Review of Hydrobiology》1978,63(5):721-726
Knowledge of plankton biogeography for the Indian and adjacent seas is necessary for an understanding of the regional characteristics and changes in the plankton composition. Some of the plankters will serve as good biogeographical indicator species. Some phytoplankters and tintinnids among zooplankton are promising for use as such labels for the presence of different waters in the Porto Novo (Coromandel coast, Bay of Bengal) region. A biogeographical classification of the local phytoplankton and peculiarities in the distribution of some rare tintinnids occurring there are discussed. 相似文献
19.
Summary Diurnal variations in water chemistry and plankton in this eutrophic tropical freshwater ponds were quite apparent. Large fluctuations were noted in dissolved oxygen, pH, carbonate and bicarbonate concentrations. The pond water gets oversaturated with oxygen during day (24.2 p.p.m.) and depleted in the night (1.2 p.p.m.). Diurnal migrations of plankton were not in conformity with temperate waters. 相似文献
20.
A new species of pelagic amphipod, Lestrigonus ducrayi sp. nov.,from eastern Australia, is described and illustrated. It isvery similar to Lestrigonus bengalensis Giles, 1887, but isreadily distinguished by a relatively shorter telson (aboutone-third peduncle uropod 3) and, in mature males, pereonites15 are fused as in females. The two species often occurtogether in the same plankton sample; the new species beingmore abundant inshore, although both species seem to preferinshore waters. A key to the species of Lestrigonus is provided. 相似文献