Paradox Of Plankton Research Articles

Metagenomics and the global ocean survey: what's in it for us, and why should we care?

Recently, a special Oceanic Metagenomics Collection of articles from the J Craig Venter Institute was published in PLoS Biology, available at: http:// collections.plos.org/plosbiology/gos-2007. At first glance, the publication represents a very large (and very welcome) addition of data to the nascent field of marine microbial metagenomics. These data, consisting of more than 7.7 million sequencing reads (46 billion base pairs of sequence), reveal more new genes, more new proteins, more diversity and a more complex ocean than might have been thought: yet they do not begin to touch the real complexity of the ocean ecosystem(s). The data are gathered from 41 sites, primarily marine, covering a transect that includes a sample about every 330 km for more than 8000 km, from the North Atlantic, southwards along the eastern edge of North America, through the Panama Canal, and onward towards the South Pacific. In addition, there is some extensive coverage near and around the Galapogos Islands. Included in the dataset are previously studied samples from the Sargasso (Venter et al., 2004). A deeper look, however, reveals that these impressive numbers are the tip of an intellectual iceberg of fascinating inconsistencies with regard to marine microbial diversity. Indeed, it may well be that what is not in the dataset may offer opportunities for future studies that transcend the opportunities lying in the dataset itself. To understand what is not there, one needs to keep in mind where and how the samples were collected: these are all nearsurface (within a few meters) samples that were filtered multiple times to yield a size fraction in the 0.2–0.8mm range. Thus, the sample can be aptly characterized as the near-surface marine planktonic niche, consisting mostly of unattached, single cells. Other organisms should have been removed on the larger 0.8 mm filters, which remain as a resource for further study. As for what is contained in the dataset, there is something for almost everyone. Rusch et al. (2007) lead off with a synopsis of the gene data – new genes galore, new phylotypes galore and the conclusion that in this niche there is still to be found an impressive array of diversity at both the taxonomic and biochemical levels. This being said, however, the dominant species are remarkably few in number. If one simply removes all ‘abundant’ species that occur at only one site, as well as those that are found only in the non-marine (hypersaline, mangrove and freshwater) sites, the number of dominant groups that characterize this marine planktonic niche decreases to about 10–20 (depending on whether you are a splitter or a grouper). This is quite remarkable, perhaps the paradox of the plankton is not a paradox at all, but is hidden in the way that microbiologists define diversity, and our understanding of what is being competed for in the so-called uniform ocean. Of these, only three (Synechococcus, Prochlorococcus and Pelagibacter ubique, a SAR-11 type) have been cultivated and have genomic sequences available. However, among these abundant species can be found an impressive array of diversity – so impressive that in no case was it possible to assemble a genome from any of them. Thus, while taxonomic/ phylogenetic diversity was quite limited, the diversity at the gene level was remarkably high, an observation fitting with several previous studies of localized sites, but apparently a general feature of the marine planktonic environment. Given these challenges, some new approaches were adopted to try and understand this immense diversity. For example, 584 sequenced genomes in finished or draft form were used for ‘fragment recruitment’ of the entire database. Remarkably, only 30% of the database revealed recruitment to any of the 584 genomes: 15% recruited to three genomes of the ‘marine planktonic niche’ (Pelagibacter, Prochlorococcus and Synechococcus), while 15% recruited to two genomes that appeared at only one site in the global ocean survey (GOS) (Shewanella and Burkholderia). In terms of understanding the nature of diversity in the marine planktonic niche, such information tells us that the sequencing of the other dominant species should be a high-priority item – one that will allow retrospective fragment The ISME Journal (2007) 1, 185–190 & 2007 International Society for Microbial Ecology All rights reserved 1751-7362/07 $30.00

Colourful coexistence of red and green picocyanobacteria in lakes and seas

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.

Phytoplankton patch patterns: Seascape anatomy in a turbulent ocean

Marine phytoplankton experience competition, predation, infection and aggregation occurring across distances of micrometres to centimetres. However, the consequences of these interactions influence global processes, such as climate and fisheries productivity. There is a long-standing default assumption that these global processes cannot be traced to plankton distributions and interactions below a few metres because of the homogenising effect of turbulence [Hutchinson, G.E., 1961. The paradox of the plankton. Am. Nat. 95, 137–146.; Siegel, D.A., 1998. Resource competition in a discrete environment: Why are plankton distributions paradoxical? Limnol. Oceanogr. 43, 1133–1146.]. We show that, in active turbulence, phytoplankton patches, on the order of 10 cm, have repeatable asymmetry and regular spacing over distances of centimetres to tens of metres. The regularity and hierarchical nature of the patches in mixed ocean water means that phytoplankton are distributed in a dynamic, but definite seascape topography, where groups of patches coalesce between intermittent turbulent eddies. These patches may link large scale processes and microscale interactions, acting as fundamental components of marine ecosystems that influence grazing efficiency, taxonomic diversity, and the initiation of aggregation and subsequent carbon flux.

Power law relationships among hierarchical taxonomic categories in algae reveal a new paradox of the plankton

Aim In this continental-scale study, the biodiversity of benthic and planktonic algal communities was explored. A recent analysis of extinct and extant tree communities by Enquist et al. (2002) showed that richness of higher taxa was a power function of species richness, invariant across temporal and spatial scales. Here we examined whether the relationships between algal richness at hierarchical taxonomic levels conform to power laws as seen for trees, and if these relationships differ between benthic and planktonic habitats. Location Streams from more than 50 major watersheds in the United States. Method A total of 3698 samples were collected from 1277 locations by the National Water-Quality Assessment Program. Three types of stream habitat were sampled: richest targeted habitats, depositional targeted habitats, and phytoplankton. The relationships between taxonomic richness at the species level vs. all higher categories from genus to phylum across the three habitats were examined by ordinary least squares (OLS) regressions after ln-transformation of all variables. The slopes, b, of these regressions represent the exponents of the power functions that scaled the richness of higher taxonomic levels (T) to species richness (S) in the form: T∝Sb. Results Algal richness at hierarchical taxonomic categories (genus to phylum) is a power function of species richness. The scaling exponent of this function, which captures the diversification of higher taxa, i.e. the rate of increase of their richness with the increase of species richness, is significantly different across environments. Main conclusions The differential algal diversification in the three studied habitats emphasizes the fundamental role of the environment in structuring the communities of simple organisms such as algae. The finding that the diversification of higher taxa is greater in the seemingly homogeneous planktonic environment, when compared to benthic habitats, encompassing an array of ecological niches, poses a new paradox of the plankton.

Competing Effects of Toxin-Producing Phytoplankton on Overall Plankton Populations in the Bay of Bengal

The coexistence of a large number of phytoplankton species on a seemingly limited variety of resources is a classical problem in ecology, known as 'the paradox of the plankton'. Strong fluctuations in species abundance due to the external factors or competitive interactions leading to oscillations, chaos and short-term equilibria have been cited so far to explain multi-species coexistence and biodiversity of phytoplankton. However, none of the explanations has been universally accepted. The qualitative view and statistical analysis of our field data establish two distinct roles of toxin-producing phytoplankton (TPP): toxin allelopathy weakens the interspecific competition among phytoplankton groups and the inhibition due to ingestion of toxic substances reduces the abundance of the grazer zooplankton. Structuring the overall plankton population as a combination of nontoxic phytoplankton (NTP), toxic phytoplankton, and zooplankton, here we offer a novel solution to the plankton paradox governed by the activity of TPP. We demonstrate our findings through qualitative analysis of our sample data followed by analysis of a mathematical model.

Power law relationships among hierarchical taxonomic categories in algae reveal a new paradox of the plankton

ABSTRACTAim In this continental‐scale study, the biodiversity of benthic and planktonic algal communities was explored. A recent analysis of extinct and extant tree communities by Enquist et al. (2002) showed that richness of higher taxa was a power function of species richness, invariant across temporal and spatial scales. Here we examined whether the relationships between algal richness at hierarchical taxonomic levels conform to power laws as seen for trees, and if these relationships differ between benthic and planktonic habitats.Location Streams from more than 50 major watersheds in the United States.Method A total of 3698 samples were collected from 1277 locations by the National Water‐Quality Assessment Program. Three types of stream habitat were sampled: richest targeted habitats, depositional targeted habitats, and phytoplankton. The relationships between taxonomic richness at the species level vs. all higher categories from genus to phylum across the three habitats were examined by ordinary least squares (OLS) regressions after ln‐transformation of all variables. The slopes, b, of these regressions represent the exponents of the power functions that scaled the richness of higher taxonomic levels (T) to species richness (S) in the form: T∝Sb.Results Algal richness at hierarchical taxonomic categories (genus to phylum) is a power function of species richness. The scaling exponent of this function, which captures the diversification of higher taxa, i.e. the rate of increase of their richness with the increase of species richness, is significantly different across environments.Main conclusions The differential algal diversification in the three studied habitats emphasizes the fundamental role of the environment in structuring the communities of simple organisms such as algae. The finding that the diversification of higher taxa is greater in the seemingly homogeneous planktonic environment, when compared to benthic habitats, encompassing an array of ecological niches, poses a new paradox of the plankton.

Spatial coexistence of phytoplankton species in ecological timescale

AbstractThe species diversity of phytoplankton is usually very high in wild aquatic systems, as seen in the paradox of plankton. Coexistence of many competitive phytoplankton species is extremely common in nature. However, experiments and mathematical theories show that interspecific competition often leads to the extinction of most inferior species. Here, we present a lattice version of a multi‐species Lotka–Volterra competition model to demonstrate the importance of local interaction. Its mathematical equilibrium is the exclusion of all but one superior species. However, temporal coexistence of many competitive species is possible in an ecological time scale if interactions are local instead of global. This implies that the time scale is elongated many orders when interactions are local. Extremely high species diversity of phytoplankton in aquatic systems may be maintained by spatial coexistence in an ecological time scale.

Diversity and biomass dynamics of marine algae in Biosphere II's tropical reef macrocosm

Macrocosms can be used to study complex ecological processes in a small physical space, but the validity of the studies depends on how well the macrocosm simulates natural ecosystem functions. We measured the standing crop of macroalgae and nutrient levels over 4 years in the Biosphere II macrocosm tropical reef biome at Oracle, Arizona. Ten years after this system was closed to outside introductions, it still contained 35 species of macroalgae, within the range found on natural reefs. The macroalgae community was recognizable as a late-successional, coralline algal turf community similar to those found in the low-energy portions of inner tropical reefs. However, biomass values for the most abundant species were in a continual state of flux over the study, and no single species was dominant. Nutrient levels were also unexpectedly dynamic, with dissolved inorganic phosphorous, nitrate, and ammonium each varying by a factor of 10 over the study. The dynamic nature of biomass and nutrient cycles would make it difficult to use this macrocosm for controlled studies. On the other hand, the community dynamics in the Biosphere II ocean may shed light on processes controlling biodiversity and succession on natural reefs. The apparently chaotic swings in biomass and nutrient levels suggested that the paradox of the plankton, which explains how seemingly uniform aquatic environments can support a wide diversity of planktonic forms, may apply to reef macroalgae as well. The Biosphere II ocean biome demonstrates that a diverse macroalgal reef community can be restored relatively easily, supporting the feasibility of actively restoring damaged natural reefs. Macrocosms such as this could be used in manipulative experiments to study the effects of nutrient enrichment and herbivory on coral–algal phase shifts.

The neutral theory of biodiversity: do the numbers add up?

In the 1960s the new technique of gel electrophoresis revealed what was then considered to be an astonishing amount of molecular variation in natural populations, with about 30% of genetic loci being polymorphic. It was thought at the time that natural selection the dominant principle in evolutionary biology could not account for such high levels of variability the costs of selection would be too high. This prompted the proposal of the neutral theory of molecular evolution (Kimura 1968; King & Jukes 1969; Kimura 1983), which postulated that most molecular evolution did not involve natural selection at all: in this model, selectively neutral mutations arose and their frequencies simply fluctuated at random, as is inevitable in a finite population. Tropical forests pose a similar puzzle for ecologists. The enormous numbers of species seem to challenge our classical notions that coexistence requires that each species has its own unique niche: how can so many species construct unique niches from such a small number of requirements sun, water, a patch of ground? The same puzzle in a different context became known as the 'paradox of the plankton' (Hutchinson 1961). As in molecular evolution, so too in ecology a neutral theory has been proposed which may resolve our puzzle (Bell 2001; Hubbell 2001) and is attracting much attention. The theory's advocates have more in mind than tropical trees, but I will restrict myself to trees to make the discussion specific. This was the context in which the theory was first proposed (Hubbell 1979) and one of the main biological areas where we have a puzzle apparently requiring a radical solution. Hereafter I will refer to the neutral theory of biodiversity as NTB. The underlying stochastic theory is the same in the two areas, although it has been studied for much longer in population genetics, as neutral advocates point out (Hubbell 2001; Volkov et al. 2003). This means we can import many results from the population genetics literature, simply interpreting the biology in a different way. In this paper I will import an important result concerning the time-scale of the neutral process, which raises serious difficulties for the NTB as an explanation of tropical forest diversity. This difficulty has been noted before (Leigh 1999; Lande et al. 2003), but does not appear to be as widely known as it should. Nonetheless, as I will discuss, neutral theory can still provide useful null models for the interpretation of data. In the fir t section, I gather together some basic theoretical results that are common to both population genetics and NTB. This is for two reasons. First of all, it serves to emphasize that we really are talking about the same theory, giving us the confidence to bring into the body of NTB an important result from population genetics concerning the time-scale of the neutral process. This will be done in the third section. Secondly, people may find it useful to have these basic results gathered toget er in one place they are currently somewhat scattered about. Having emphasized the underlying identity of the theory, I then briefly explore the implications of the biological differences between the worlds of molecular evolution and biodiversity for the likely future development of the theory in the biodiversity context.

Coexistence of cryptic rotifer species: ecological and genetic characterisation of Brachionus plicatilis

Summary1. The coexistence of five cryptic species of the rotifer species complex Brachionus plicatilis was investigated in four coastal Mediterranean ponds. Monthly sampling was undertaken for 15 months and species were characterised using allozyme electrophoresis.2. We describe species‐diagnostic allozyme loci that can be used for rapid identification of these species.3. The five species overlapped to some extent in their temporal use of the ponds, although some seasonal segregation was observed.4. The match between temporal and spatial distribution and limnological conditions suggested ecological specialisation in some cases, although we found striking examples of extensive seasonal overlap.5. Our results indicate that sympatry of cryptic rotifer species is largely because of seasonal ecological specialisation, which allows seasonal succession and partitioning of resources. The processes that might be involved in the long periods of overlapping seasonal distributions of species which are potentially competitors are discussed. This example illustrates that the ‘paradox of the plankton’ is more the rule than the exception.

Why plankton communities have no equilibrium: solutions to the paradox

In a classical paper, Hutchinson (1961) argued that the large number of species in most plankton communities is remarkable in view of the competitive exclusion principle, which suggests that in homogeneous, well-mixed environments species that compete for the same resources cannot coexist. Few ideas in aquatic ecology have evoked more research than this `paradox of the plankton'. This review is an effort to put the main solutions to the paradox that have been proposed over the years into perspective. Hutchinson himself already suggested that the explanation could be that plankton communities are not in equilibrium at all due to weather-driven fluctuations. Subsequent research confirmed that such externally imposed variability can allow many species to coexist. Another important point is that in practice the homogeneous well-mixed conditions assumed in the competitive exclusion principle hardly exist. Even the open ocean, for instance, has a spatial complexity resulting from meso-scale vortices and fronts that can facilitate coexistence of species. Perhaps most excitingly, theoretical work on species interactions has given a counter-intuitive new dimension to the understanding of diversity. Various competition and predation models suggest that even in homogeneous and constant environments plankton will never settle to equilibrium. Instead, interactions between multiple species may give rise to oscillations and chaos, with a continuous wax and wane of species within the community. Long-term laboratory experiments support this view. This chaotic behavior implies among other things that plankton dynamics are intrinsically unpredictable in the long run when viewed in detail. Nonetheless, on a higher aggregation level, indicators such as total algal biomass may show quite regular patterns.

Intrinsic dynamics and stability properties of size-structured pelagic ecosystem models

Although pelagic ecosystem models, coupled with ocean circulation models, are being widely used to quantify fluxes of nutrients and carbon in the ocean at regional and basin scales, relatively little work has been done on understanding their intrinsic dynamics independently of physical forcing. In this study, the dynamics of three common formulations for the NPZD class of models (nutrient, phytoplankton, zooplankton and detritus) using two different types of predation functional response are analysed and compared. Our goal is to characterize the stability properties of this class of models with respect to variations in light and total nutrient concentrations. Despite important structural differences, the different model formulations all show asymptotic stable equilibria at low total nutrient concentrations and high to moderate light intensities, and limit cycle oscillations at low light intensities and high total nitrogen concentrations. Limit cycles are formed through a Hopf bifurcation as a phase lag develops between predator (Z i ) and prey (P i or Z i-1 ) due to a relatively sharp increase in the growth rate of the prey in relation to that of the predator. The use of variable preferences in the functional response provides a density-dependent mechanism that allows the system to self-regulate, increasing system stability considerably, but does not eliminate the instabilities completely. Instabilities occur at light and nutrient levels that correspond to those observed on the bottom of the euphotic zone near the nutricline, where the deep chlorophyll maximum is usually located. This suggests that the deep chlorophyll maximum might be dynamically unstable. This dynamic disequilibrium in species composition and the characteristically long transient times would allow species persistence in the presence of seasonal and mesoscale variations and provide a mechanism for species coexistence in the relatively homogeneous open ocean environment, thereby providing a potential solution for the 'paradox of plankton'. In the multi-species models, the higher diversity of species (wider range of values for the biological parameters) allows biological activity (photosynthesis, grazing and predation) to occur under a wider range of light and nutrient conditions, resulting in higher primary and secondary production and lower nutrient concentrations at light intensities equivalent to those in the upper part of the euphotic zone, than in the single-species model.

Chemical warfare between microbes promotes biodiversity

Evolutionary processes generating biodiversity and ecological mechanisms maintaining biodiversity seem to be diverse themselves. Conventional explanations of biodiversity such as niche differentiation, density-dependent predation pressure, or habitat heterogeneity seem satisfactory to explain diversity in communities of macrobial organisms such as higher plants and animals. For a long time the often high diversity among microscopic organisms in seemingly uniform environments, the famous "paradox of the plankton," has been difficult to understand. The biodiversity in bacterial communities has been shown to be sometimes orders of magnitudes higher than the diversity of known macrobial systems. Based on a spatially explicit game theoretical model with multiply cyclic dominance structures, we suggest that antibiotic interactions within microbial communities may be very effective in maintaining diversity.

Does “supersaturated coexistence” resolve the “paradox of the plankton”?

In contradiction with field observations, theory predicts that the number of coexisting plankton species at equilibrium cannot exceed the number of limiting resources, which is called the “paradox of the plankton”. Recently, Huisman & Weissing (1999, 2000) showed, in a model study, that the number of coexisting species may exceed the number of limiting resources when internal system feedback induces oscillations or chaos. In this paper, we use the term “supersaturated coexistence” for this phenomenon. On the basis of these findings, they claimed that the paradox of the plankton is solved. We investigated the prerequisites for supersaturated coexistence in the same model. Our results indicate that supersaturated coexistence is a rare phenomenon in parameter space, requires a very precise parameterization of the community members and is sensitive to the introduction of new species and the removal of the present species. This raises the question of whether supersaturated coexistence is likely to occur in nature. We conclude that the claim by Huisman & Weissing (1999, 2000) is premature.

Towards a solution of the plankton paradox: the importance of physiology and life history

Phytoplankton communities reveal an astonishing biodiversity, whereas classical competition theory seems to suggest that only a few competing species can survive. Recently we suggested a new solution to this plankton paradox. In theory, at least, competition between multiple species can generate complex dynamics that can support a large number of species. How likely is it then, in reality, that competitive chaos indeed promotes biodiversity? To obtain some insight, we simulated multispecies competition according to five different physiological scenarios. For random species parameters, biodiversity was generally low. Assuming plausible physiological trade‐offs, the simulations revealed switches back and forth between equilibrium and nonequilibrium dynamics, and a higher biodiversity. An extremely high biodiversity, with sometimes more than 100 species on three resources, was observed in simulations that assumed a cyclic relation between competitive abilities and resource contents. We conclude that physiological and life‐history patterns have a major impact on the likelihood of nonequilibrium dynamics and on the biodiversity of plankton communities.

Reply: Coexistence and resource competition

How can we explain the biodiversity of rainforests and coral reefs if we do not understand the species diversity of phytoplankton in a droplet of water1? In our attempt2 to solve the plankton paradox, we showed that multispecies competition may generate oscillations and chaos and that these fluctuations create opportunities for the coexistence of many species. Lundberg et al. question the novelty of our findings and argue that the plankton paradox was resolved 25 years ago.

A model for resolving the plankton paradox: coexistence in open flows

1. Recent developments in the field of chaotic advection in hydrodynamical/environmental flows encourage us to revisit the population dynamics of competing species in open aquatic systems. 2. We assume that these species are in competition for a common limiting resource in open flows with chaotic advection dynamics. As an illustrative example, we consider a time periodic two‐dimensional flow of viscous fluid (water) around a cylindrical obstacle. 3. Individuals accumulate along a fractal set in the wake of the cylinder, which acts as a catalyst for the biological reproduction process. While in homogeneous, well mixed environments only one species could survive this competition, coexistence of competitors is typical in our hydrodynamical system. 4. It is shown that a steady state sets in after sufficiently long times. In this state, the relative density of competitors is determined rather by the fractal nature of the spatial distribution of the advected species, and by their initial conditions, than by their competitive abilities. We argue that two factors, the strong chaotic mixing along a fractal set and the boundary layer around the obstacle, are responsible for the coexistence.

Mesoscale vortices and the paradox of the plankton.

Coexistence of competitive species is severely limited by the availability of resources and the characteristics of the environment. In particular, the so-called 'competitive exclusion principle' states that, at equilibrium, the number of coexisting species cannot be larger than the number of resources for which they compete. However, many in situ observations have revealed prolonged coexistence of a large number of competitive plankton species, a phenomenon known as 'the paradox of the plankton'. Here we investigate this problem and show that ocean mesoscale vortices generate transport barriers and incomplete horizontal mixing, allowing for a prolonged survival of the less-fit species, even for fully homogeneous resource distributions. In such a situation, the temporarily less-fit plankton species are protected from competition by the action of the vortices.

Phytoplankton species diversity control through competitive exclusion and physical disturbances

Competitive exclusion theory suggests that phytoplankton species number in an assemblage at equilibrium will be limited to the number of simultaneously limiting resources, generally three or fewer. However, natural phyto‐plankton assemblages usually exhibit high species diversity, hence the concept of Hutchinson's “paradox of the plankton”. Recent works have suggested that this apparent paradox is a result of disturbances intermediate in frequency relative to the time period necessary for species succession to lead to equilibrium conditions (sensu Connell's intermediate disturbance hypothesis [IDH]). Moreover, evidence indicates that disturbances of intermediate intensities are also conducive to maintenance of high species diversity in phytoplankton communities. Using a long‐term data record from hypereutrophic subtropical Hartbeespoort Dam (South Africa) that was typically dominated by a single species, but annually subjected to physical disturbance, we demonstrate here that disturbances can indeed enhance phytoplankton species diversity. However, these data fail to support Connell's IDH per se, as moderate‐and high‐intensity disturbances yielded similarly high species diversity. These data also suggest that community resilience (the ability or time to return to predisturbed conditions) is negatively related to disturbance intensity, such that higher intensity disturbances maintained high diversity for longer periods of time relative to lower intensity disturbances.

Fractality, chaos, and reactions in imperfectly mixed open hydrodynamical flows

We investigate the dynamics of tracer particles in time-dependent open flows. If the advection is passive the tracer dynamics is shown to be typically transiently chaotic. This implies the appearance of stable fractal patterns, so-called unstable manifolds, traced out by ensembles of particles. Next, the advection of chemically or biologically active tracers is investigated. Since the tracers spend a long time in the vicinity of a fractal curve, the unstable manifold, this fractal structure serves as a catalyst for the active process. The permanent competition between the enhanced activity along the unstable manifold and the escape due to advection results in a steady state of constant production rate. This observation provides a possible solution for the so-called “paradox of plankton”, that several competing plankton species are able to coexists in spite of the competitive exclusion predicted by classical studies. We point out that the derivation of the reaction (or population dynamics) equations is analog to that of the macroscopic transport equations based on a microscopic kinetic theory whose support is a fractal subset of the full phase space.