共查询到20条相似文献,搜索用时 31 毫秒
1.
The dynamics of aquatic biological communities in a patchy environment is of great interest in respect to interrelations between phenomena at various spatial and time scales. To study the complex plankton dynamics in relation to variations of such a biologically essential parameter as the fish predation rate, we use a simple reaction-diffusion model of trophic interactions between phytoplankton, zooplankton, and fish. We suggest that plankton is distributed between two habitats one of which is fish-free due to hydrological inhomogeneity, while the other is fish-populated. We show that temporal variations in the fish predation rate do not violate the strong correspondence between the character of spatial distribution of plankton and changes of plankton biomass in time: regular temporal oscillations of plankton biomass correspond to large-scale plankton patches, while chaotic oscillations correspond to small-scale plankton patterns. As in the case of the constant fish predation rate, the chaotic plankton dynamics is characterized by coexistence of the chaotic attractor and limit cycle. 相似文献
2.
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
3.
We consider the spatio-temporal dynamics of a spatially-structured generalization of the phytoplankton-zooplankton-fish larvae
model system proposed earlier (Biktashev et al., 2003, J. Plankton Res. 5, 21–33; James et al., 2003, Ecol. Model. 160, 77–90). In contrast to Pitchford and Brindley (2001, Bull. Math. Biol. 63, 527–546), who were concerned with small scale patchiness (i.e., 1–10m), on which the (stochastic) raptorial behaviour of
individual larvae is important, we address here the much larger scale ‘patchy’ problems (i.e., 10–100 km), on which both larvae
and plankton may be regarded as passive tracers of the fluid motion, dispersed and mixed by the turbulent diffusion processes.
In particular, we study the dependence of the fish recruitment on carrying capacities of the plankton subsystem and on spatio-temporal
evolution of that subsystem with respect to the larvae hatching site(s). It is shown that the main features found both in
the nonstructured and age-structured spatially uniform models are observed in the spatially structured case, but that spatial
effects can significantly modify the overall quantitative outcome.
Spatial patterns in the metamorphosed fish distribution are a consequence of quasi-local interaction of larvae with plankton,
in which the dispersion of larvae by large scale turbulent eddies plays little part due to the relatively short timescale
of the larvae development. As a result, in a strong phyto/zooplankton subsystem, with fast reproduction rate and large carrying
capacity of phytoplankton and high conversion ratio of zooplankton, recruitment success depends only on the localization and
timing of the hatching with respect to the plankton patches. In a weak phyto/zooplankton system, with slow reproduction rate
and small carrying capacity of phytoplankton and low conversion ratio of zooplankton, the larvae may significantly influence
the evolution of the plankton patches, which may lead to nontrivial cooperative effects between different patches of larvae.
However, in this case, recruitment is very low. 相似文献
5.
Global warming is a major threat to the natural environment worldwide with potential adverse impact on plankton community. This will ultimately lead to a change in the dynamics of aquatic food webs. In this study we used seasonally forced multi-species version of the classic Rosenzweig–MacArthur predator–prey model to understand the role and stochastic influence of increasing temperature on marine plankton. First, stable coexistence of four phytoplankton and three zooplankton species was created in a system and then the level of temperature changed to achieve our research goal. We found that the stable coexistence of phytoplankton and zooplankton was related to periodic shifts in species biomass, variation in inter-specific competition and niche configuration. Warming significantly reduced total plankton biomass and changed turnover time of a species, with gradual warming breaking the stable coexistence of phytoplankton and zooplankton. In addition, we found that warming make specialist species more vulnerable than generalist species. After adding noise, a significant variation was observed in plankton biomass and amplification of noise was higher for phytoplankton compared to zooplankton. These results suggest that stochastic or unpredictable nature of temperature fluctuations may create a window of opportunity for the emergence of new species. Overall, warming would induce a shift in plankton dynamics and thereby exert pressure on plankton dependent communities such as fish in the long run. 相似文献
7.
Infochemicals released by marine phytoplankton play important roles in food web interactions by influencing the feeding behavior and selectivity of zooplanktonic predators. Recent modeling efforts have focused on the role of such chemicals as toxic grazing deterrents in phytoplankton competition. However, infochemicals may also be utilized as grazing cues, leading predators to profitable foraging patches. Here we investigate the role of infochemical mediated zooplankton grazing in a standard 3-species phytoplankton competition model, with the aim of further elucidating the ecological role of phytoplankton derived infochemicals. We then extend this to consider a more realistic 4-species model. The models produce a range of solutions depending on the strength of competition and microzooplankton grazing selectivity. Our key result is that infochemical chemoattractants, which increase the susceptibility of the producer to grazing, can provide a refuge for both competing phytoplankton species by attracting carnivorous copepods to consume microzooplankton grazers in a multi-trophic interaction. Our results indicate that infochemicals potentially have important consequences for the dynamics of marine food webs. 相似文献
8.
We propose a model for explaining both red tides and recurring phytoplankton blooms. Three assumptions are made, namely the presence of toxin producing phytoplankton, the satiation phenomenon in zooplankton's feeding, modelled by a Holling type II response, and phytoplankton aggregation leading to formation of patches. The dynamics of the plankton population is shown to depend on the fraction of the phytoplankton population that aggregates to form colonies and on the number of the latter. 相似文献
9.
The decoupling of trophic interactions is potentially one of the most severe consequences of climate warming. In lakes and oceans the timing of phytoplankton blooms affects competition within the plankton community as well as food–web interactions with zooplankton and fish. Using Upper Lake Constance as an example, we present a model‐based analysis that predicts that in a future warmer climate, the onset of the spring phytoplankton bloom will occur earlier in the year than it does at present. This is a result of the earlier occurrence of the transition from strong to weak vertical mixing in spring, and of the associated earlier onset of stratification. According to our simulations a shift in the timing of phytoplankton growth resulting from a consistently warmer climate will exceed that resulting from a single unusually warm year. The numerical simulations are complemented by a statistical analysis of long‐term data from Upper Lake Constance which demonstrates that oligotrophication has a negligible effect on the timing of phytoplankton growth in spring and that an early onset of the spring phytoplankton bloom is associated with high air temperatures and low wind speeds. 相似文献
11.
Here we consider a reaction diffusion system of three plankton populations, a zooplankton feeding on two phytoplankton populations,
in two different settings. Firstly, the two phytoplanktons are both non-toxic and both enhance the growth of the grazing zooplankton.
Secondly, we assume that one of the phytoplankton releases toxin and thereby inhibits the growth of the zooplankton. Our analytic
and numerical study shows that the spatiotemporal distribution of the plankton species is uniform when both phytoplankton
populations are non-toxic. However, in the presence of toxin-producing phytoplankton, the biomass distribution of all the
plankton populations becomes inhomogeneous. 相似文献
12.
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
13.
It is increasingly recognised that viruses are a significant active component of oceanic plankton ecosystems. They play an important role in biogeochemical cycles as well as being implicated in observed patterns of species abundance and diversity. The influence of viral infection in plankton ecosystems is not fully understood. Here we use a number of well-founded mathematical models to investigate the interplay of the ecological and epidemiological interactions of plankton and viruses in the sea. Of particular interest is the role of nutrient on the population dynamics. Nutrient forcing has been suggested as a means of absorbing excess anthropogenic atmospheric carbon dioxide by stimulating increased phytoplankton primary productivity. Here we show that enriching nutrient levels in the sea may decrease the amount of infected phytoplankton species thereby additionally enhancing the efficiency of the biological pump, a means by which carbon is transferred from the atmosphere to the deep ocean. 相似文献
14.
In homogeneous environments, by overturning the possibility of competitive exclusion among phytoplankton species, and by regulating
the dynamics of overall plankton population, toxin-producing phytoplankton (TPP) potentially help in maintaining plankton
diversity—a result shown recently. Here, I explore the competitive effects of TPP on phytoplankton and zooplankton species
undergoing spatial movements in the subsurface water. The spatial interactions among the species are represented in the form
of reaction-diffusion equations. Suitable parametric conditions under which Turing patterns may or may not evolve are investigated.
Spatiotemporal distributions of species biomass are simulated using the diffusivity assumptions realistic for natural planktonic
systems. The study demonstrates that spatial movements of planktonic systems in the presence of TPP generate and maintain
inhomogeneous biomass distribution of competing phytoplankton, as well as grazer zooplankton, thereby ensuring the persistence
of multiple species in space and time. The overall results may potentially explain the sustainability of biodiversity and
the spatiotemporal emergence of phytoplankton and zooplankton species under the influence of TPP combined with their physical
movement in the subsurface water. 相似文献
15.
The predictability of plankton response to reductions of planktivorous fish was investigated by comparing the plankton community in three biomanipulated lakes and ten unmanipulated lakes differing in intensity of fish predation. Data collected on total phosphorus, phytoplankton and zooplankton biomass and share of cyanobacteria and large grazers, as well as specific growth rate of phytoplankton, were further used to test some of the proposed underlying response-mechanisms. In the biomanipulated lakes the algal biomass and share of cyanobacteria decreased, specific growth rate of phytoplankton increased, and zooplankton biomass and share of large grazers increased or remained unchanged. This pattern was largely reflected in the differences in food-chain structure between the unmanipulated lakes with highversus those with low fish predation. The qualitative response to planktivorous fish reduction thus seems largely predictable. The biomanipulated lakes differed, however, in magnitude of response: the smallest hypertrophic, rotenone-treated lake (Helgetjern) showed the most dramatic response, whereas the large, deep mesotrophic lake (Gjersjøen), which was stocked with piscivorous fish, showed more moderate response, probably approaching a new steady state. These differences in response magnitude may be related to different perturbation intensity (rotenone-treatmentversus stocking with piscivores), food-chain complexity and trophic state. Both decreased phosphorus concentration and increased zooplankton grazing are probably important mechanisms underlying plankton response to biomanipulation in many lakes. The results provide tentative support to the hypothesis that under conditions of phosphorus limitation, increased zooplankton grazing can decrease algal biomassvia two separate mechanisms: reduction of the phosphorus pool in the phytoplankton, and reduction of the internal C:P-ratio in the phytoplankton cells. 相似文献
16.
Human activity causes ocean acidification (OA) though the dissolution of anthropogenically generated CO 2 into seawater, and eutrophication through the addition of inorganic nutrients. Eutrophication increases the phytoplankton biomass that can be supported during a bloom, and the resultant uptake of dissolved inorganic carbon during photosynthesis increases water-column pH (bloom-induced basification). This increased pH can adversely affect plankton growth. With OA, basification commences at a lower pH. Using experimental analyses of the growth of three contrasting phytoplankton under different pH scenarios, coupled with mathematical models describing growth and death as functions of pH and nutrient status, we show how different conditions of pH modify the scope for competitive interactions between phytoplankton species. We then use the models previously configured against experimental data to explore how the commencement of bloom-induced basification at lower pH with OA, and operating against a background of changing patterns in nutrient loads, may modify phytoplankton growth and competition. We conclude that OA and changed nutrient supply into shelf seas with eutrophication or de-eutrophication (the latter owing to pollution control) has clear scope to alter phytoplankton succession, thus affecting future trophic dynamics and impacting both biogeochemical cycling and fisheries. 相似文献
17.
Information on the effects of water level changes on microbial planktonic communities in lakes is limited but vital for understanding ecosystem dynamics in Mediterranean lakes subjected to major intra- and inter-annual variations in water level. We performed an in situ mesocosm experiment in an eutrophic Turkish lake at two different depths crossed with presence/absence of fish in order to explore the effects of water level variations and the role of top-down regulation at contrasting depths. Strong effects of fish were found on zooplankton, weakening through the food chain to ciliates, HNF and bacterioplankton, whereas the effect of water level variations was overall modest. Presence of fish resulted in lower biomass of zooplankton and higher biomasses of phytoplankton, ciliates and total plankton. The cascading effects of fish were strongest in the shallow mesocosms as evidenced by a lower zooplankton contribution to total plankton biomass and lower zooplankton:ciliate and HNF:bacteria biomass ratios. Our results suggest that a lowering of the water level in warm shallow lakes will enhance the contribution of bacteria, HNF and ciliates to the plankton biomass, likely due to increased density of submerged macrophytes (less phytoplankton); this effect will, however, be less pronounced in the presence of fish. 相似文献
18.
A model of the lower trophic levels that consists of a system of coupled
ordinary differential equations was developed to investigate the
time-dependent behavior of doliolid populations associated with upwelling
features on the outer southeastern US continental shelf. Model equations
describe the interactions of doliolids with two phytoplankton size
fractions, five copepod developmental states and detrital pool. Additional
equations describe nitrate and ammonia. Model dynamics are based primarily
upon data obtained from field and laboratory experiments for southeastern
US continental shelf plankton populations. Variations on a reference
simulation, which represents average upwelling conditions without
doliolids, were carried out to determine the effect of inclusion of
doliolids, temperature and nutrient variations, and variations in ambient
food concentrations on the basic plankton community structure. These
simulations provide a measure of the role of environmental versus
biological interactions in structuring the planktonic food web on the
southeastern US continental shelf. Simulations show that he copepod
population is significantly reduce when doliolids are present. This happens
primarily as a result of direct predation of the doliolids on copepod eggs
and juveniles as opposed to an increase in competition for phytoplankton,
the primary food source. Additional simulations show that the cooler
temperatures associated with the newly upwelled water temporarily decrease
the growth rates of doliolids and copepods, bestowing an event greater
advantage on the rapidly reproducing doliolids.
相似文献
19.
This work is focused on the processes underlying the dynamics of spatially inhomogeneous plankton communities. We demonstrate
that reaction-diffusion mathematical models are an appropriate tool for searching and understanding basic mechanisms of complex
spatio-temporal plankton dynamics and fractal properties of planktivorous fish school walks. 相似文献
|