Chaos and order in plankton dynamics. Complex behavior of a simple model

The role of the diffusive interaction between fish-populated and fish-free habitats in a patchy environment in plankton pattern formation is studied by means of a minimal reaction-diffusion model of the nutrient-plankton-fish food chain. It is shown that such interaction can give rise to spatio-temporal plankton patterns. The fractal dimension of the patterns is shown dependent on the fish predation rate. The spatially averaged plankton dynamics depending on both fish predation rate and distance between fish-populated habitats can exhibit chaotic and regular behavior. The chaotic plankton dynamics is characteristic of a wide parameter range.     

Effect of the rate of phytoplankton growth on the spaced-time dynamics of plankton communities in an homogeneous environment

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.     

Respiration of plankton in two small,polyhumic lakes

The respiration of plankton of two polyhumic lakes was measured as production of carbon dioxide in dark bottles. The method proved to be enough sensitive for use in oligotrophic lakes with low alkalinity. The respiration of plankton followed broadly changes in temperature. However, the primary production of phytoplankton was probably the main factor governing the seasonal pattern of respiration. During summer the respiration of plankton was more than three times higher than the primary production of phytoplankton. This suggests that allochthonous humic substances are an important source of carbon and energy for organisms of polyhumic lakes.     

Small-scale turbulence and plankton contact rates

Theoretical and empirical studies of plankton trophodynamicsare usually based on some function of the relative density ofpredator-and-prey plankton. Such approaches based only on therelative density of predator and prey generally underestimatepredator-prey contact rates because contact depends on boththe relative density and the relative velocity of predator andprey. We estimate the components of predator-and-prey contactthat are due to small-scale turbulence. The small-scale turbulenceeffect suggests reconsidering estimates of plankton food requirements,energy gain-and-loss from foraging and mechanisms associatedwith patch formation and dissipation.     

Vibrio cholerae strains possess multiple strategies for abiotic and biotic surface colonization

Despite its notoriety as a human pathogen, Vibrio cholerae is an aquatic microbe suited to live in freshwater, estuarine, and marine environments where biofilm formation may provide a selective advantage. Here we report characterization of biofilms formed on abiotic and biotic surfaces by two non-O1/O139 V. cholerae strains, TP and SIO, and by the O1 V. cholerae strain N16961 in addition to the isolation of 44 transposon mutants of SIO and TP impaired in biofilm formation. During the course of characterizing the mutants, 30 loci which have not previously been associated with V. cholerae biofilms were identified. These loci code for proteins which perform a wide variety of functions, including amino acid metabolism, ion transport, and gene regulation. Also, when the plankton colonization abilities of strains N16961, SIO, and TP were examined, each strain showed increased colonization of dead plankton compared with colonization of live plankton (the dinoflagellate Lingulodinium polyedrum and the copepod Tigriopus californicus). Surprisingly, most of the biofilm mutants were not impaired in plankton colonization. Only mutants impaired in motility or chemotaxis showed reduced colonization. These results indicate the presence of both conserved and variable genes which influence the surface colonization properties of different V. cholerae subspecies.     

Environmental influences on long-term variability in marine plankton

The major patterns of geographical and seasonal variability of the plankton of the north-east Atlantic and the North Sea are described to provide the background to a presentation of the dominant patterns of year-to-year fluctuations in the abundance of the plankton of the area for the period 1948 to 1984. A feature of the variability is a marked similarity both between species and between areas. The main pattern of year-to-year change has the form of a quasi linear downward trend in abundance with, superimposed on this, an element of variability with a periodicity of about three years. There is a complex relationship between the plankton and an estimate of changes in the frequency of westerly weather which can be interpreted in terms of influences acting over limited periods of the seasonal cycle coupled with persistence in the stocks of zooplankton. Relationships between year-to-year variations in the abundance of phytoplankton and zooplankton can be interpreted in terms of a response by the zooplankton to variations in food supply coupled with feed-back to the phytoplankton involving in situ nutrient regeneration.     

Viable gut passage of cyanobacteria through the filter-feeding fish Atlantic menhaden, Brevoortia tyrannus

We examined the contents of the alimentary tract of juvenileAtlantic menhaden, an obligate filter-feeding fish, with epifluoresencemicroscopy. All plankton taxa and detrital material observedin plankton samples from the sampling area could also be foundin the esophagus of the fish. The corresponding plankton taxawere absent from the pre-feces sampled in the hindgut with theexception of cyanobacteria, which were found intact and fluorescingas they do in nature. The survival of cyanobacteria during gutpassage and their presence in menhaden feces may enhance bothnutrient availability and the delivery of these cells to thebenthos. Additionally, diatoms frustules were found in the pre-feces,which may affect the sequestration of biogenic silica. Theseresults may have bearing on the formation of cyanobacteria blooms,nutrient flow in estuaries and the delivery of material to thesediment.     

Changes in the pattern of feeding of kokanee <Emphasis Type="Italic">Oncorhynchus nerka</Emphasis> from Lake Tolmachevskoe during the formation of its population

Analysis of the feeding of kokanee Oncorhynchus nerka from Lake Tolmachevskoe, which was relocated here from Lake Kronotskoe more than 20 years ago, was studied. Lake Kronotskoe is inhabited by two forms of kokanee that differ in the pattern of feeding (plankton-eaters and benthos-eaters) and some morphological characters. According to the number of rakers at the first gill arch, kokanee from Tolmachevskoe Lake corresponds to plankton-eaters from Kronotskoe Lake; however, in the target water body, only single fish and only in the autumn period feed on plankton. The bulk of feeding is comprised of larger organisms: in summer of insect imagines and in autumn of benthos. Feeding of large and small fish in different areas of the lake from July to September is characterized. The change in the lake ecosystem related to the construction of Tolmachevskaya Hydraulic Power Plant and the formation of the reservoir apparently affected the pattern of fish feeding from 2003 to 2007, the number of prey in stomachs and the stomach fullness index considerably decreased, and the proportion in the food bolus of nonfood items, mainly plant remains, drastically increased.     

Population dynamics: Limits of predictability

Problems related to the complex pattern of ecosystem dynamics are discussed. Examples of studies on the complex population dynamics are considered, including those of plankton populations in a spatially heterogeneous environment and of an agroecosystem invaded by pests resistant to Bt toxins produced by genetically modified insecticidal crops.     

Changes in plankton and fish larvae communities across hydrographic fronts off West Greenland

The variability in plankton community structure was studiedin Disko Bay and across important fishing banks off the westcoast of Greenland. The primary goal of the study was to investigatepossible linkages between hydrographical processes and planktonstructures, hypothesizing that hydrographic fronts would bepresent in the area, and that these to a large extent determineplankton distribution, composition and productivity. We sampledalong four cross-shelf transects, one covering Disko Bay andDisko Bank, while the other three covered Store Hellefiske Bank,Lille Hellefiske Bank and Sukkertop Bank. The hydrography wasexamined by CTD profiling, the phytoplankton by fluorescenceprofiling and water bottle sampling, while mesozooplankton andichthyoplankton were sampled by vertical or oblique net hauls,respectively. We observed distinct along-shelf flowing currentsin the area (e.g. the West Greenland Current, the Polar Currentand the Irminger Current), and the physical characteristicsindicated frontogenesis at the shelf slope, in regions of 80–100m water depth. Phytoplankton and ichthyoplankton showed a cross-shelfstructuring with apparent linkages to frontal characteristics,while a more diverse pattern was observed for the mesozooplanktonwhich were dominated by Calanus finmarchicus, Calanus glacialisand Calanus hyperboreus. The relationship between hydrographiccharacteristics and plankton distribution differed among species,and apparently specific plankton communities were establishedin different areas of the shelf. For example the larvae of Boreogadussaida, Ammodytes sp., Reinhardtius hippoglossoides and Stichaeuspunctatus differed markedly in distributional characteristics.In addition to the cross-shelf structuring, marked differencesin species composition and total plankton abundance were observedin the along-shelf (north–south) direction. The latitudinaldifferences in the unicellular plankton communities are interpretedlargely within a seasonal successional framework (i.e. an earlydominance of diatoms followed by increasing importance of smallerunicellular plankton), while the ichthyo- and zooplankton communitiesalso differed by the respective dominance of species with polarversus temperate origin. Our findings suggest that the flowof major currents and the establishment of hydrographical frontsare of primary importance to the plankton communities in theWest Greenland shelf area, influencing the early life of fishand the recruitment to the important fisheries resources.     

Distribution of potentially pathogenic bacteria as free living and plankton associated in a marine coastal zone

AIMS: To determine the abundance of faecal and nonfaecal bacteria related to human and animal health, as free living or associated with small (>64 microm) and large (>200 microm) plankton, samples were collected monthly from the coastal zone at Messina (Italy). METHODS AND RESULTS: Different enrichment and selective cultural methods were used to determine the abundance of bacteria in sea water and plankton. The bacteria were more frequently isolated from water and large plankton than from small plankton. Vibrio and Aeromonas spp. showed different distribution patterns in water and plankton. Faecal indicators were always present in water and the large size class plankton samples. Enterococci associated with large plankton were more abundant than E. coli in the winter. Vibrio species distributions were different in water and plankton samples. Among arcobacters only A. butzleri was isolated from water and plankton samples. Campylobacter spp. was always absent in small plankton and more frequent in large plankton than in water. CONCLUSIONS: The colonization of zooplankton by potentially pathogenic bacteria is a widespread phenomenon. SIGNIFICANCE AND IMPACT OF THE STUDY: The presence of potentially pathogenic bacteria in sea water and associated with plankton can have ecological and epidemiological implications.     

Interdependence of plankton spatial distribution and plancton biomass temporal oscillations: mathematical simulation

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.     

OBSERVATIONS ON CHAETOCEROS BUCEROS (BACILLARIOPHYCEAE), A RARE TROPICAL PLANKTONIC SPECIES COLLECTED FROM THE MEXICAN PACIFIC1

Examination of net plankton samples from the Gulf of Tehuantepec (Mexican Pacific) yielded a rare tropical species of the genus Chaetoceros, C. buceros Karsten. This species is conspicuous because of its relatively large size, type of chain formation, and shape of the terminal setae. Electron microscopic study revealed other interesting characteristics: the intercalary values are more lightly silicified than the terminal valves and show a pattern of costae radiating form the center with various annuli (“central hyaline fields”) in the center of the valve face; both kind of valves are perforated by small poroids. Terminal valves possess several (21–30) slitlike and randomly oriented rimoportulae. Important morphological differences exist between the intercalary and the terminal setae. Morphological characters, comparision with related species, and the systematic position are discussed. A new section of the subgenus Hyalochaete, Conspicua, is proposed to include C. buceros.     

Nutrients and toxin producing phytoplankton control algal blooms — a spatio-temporal study in a noisy environment

A phytoplankton-zooplankton prey-predator model has been investigated for temporal, spatial and spatio-temporal dissipative pattern formation in a deterministic and noisy environment, respectively. The overall carrying capacity for the phytoplankton population depends on the nutrient level. The role of nutrient concentrations and toxin producing phytoplankton for controlling the algal blooms has been discussed. The local analysis yields a number of stationary and/or oscillatory regimes and their combinations. Correspondingly interesting is the spatio-temporal behaviour, modelled by stochastic reaction-diffusion equations. The present study also reveals the fact that the rate of toxin production by toxin producing phytoplankton (TPP) plays an important role for controlling oscillations in the plankton system. We also observe that different mortality functions of zooplankton due to TPP have significant influence in controlling oscillations, coexistence, survival or extinction of the zoo-plankton population. External noise can enhance the survival and spread of zooplankton that would go extinct in the deterministic system due to a high rate of toxin production.     

Role of the daily food ration of perch fry (Perca fluvialis) in infestation with Bunodera luciopercae (Trematoda, Allocreadiidae)

The list of intermediate hosts of Bunodera luciopercae is given. In Lake Syamozero they are represented by crustaceans Heterocope, Ophryoxus. Data on their role in the ration of juvenile perch are given. Diurnal dynamics of the ratio between infected and noninfected plankton in feeding and the process of the formation of fish infection have been studied.     

Contribution of biofilm‐dwelling consumers to pelagic–benthic coupling in a large river

1. Over the course of this 17‐month study, we assessed the potential loss of plankton (bacteria, algae, heterotrophic flagellates) to consumers (ciliates and rotifers) within mature biofilms established on natural substrata exposed to the main current of the River Rhine (Germany). Once a month, in flow cells in a bypass system to the River Rhine, we measured the clearance rates of the biofilm‐associated consumers on the different groups within the natural plankton. 2. Ciliates were the most dominant consumers, among which planktivorous groups, particularly peritrichs and (in spring and summer) heterotrichs dominated. Consumer biomass varied with season, with the highest density occurring directly after the appearance of the phytoplankton spring peak. 3. Clearance rates on plankton ranged from 96 to 565 L m^?2 d^?1 for bacteria and 66–749 L m^?2 d^?1 for algae, with a preference for algae in summer and for bacteria in winter. This pattern coincided with seasonal changes in the structures of the grazer communities. The consumers (both ciliates and rotifers with total standing stocks ranging between 19 and 572 mg C m^?2) imported a substantial amount of organic matter (between 15 and 137 mg C m^?2 d^?1) into the biofilm. 4. These results highlight the potential importance of consumers in the biofilm as a trophic link between the plankton and the benthos, a function that has hitherto mostly been attributed to filter‐feeding bivalves. In contrast to bivalves, the biofilm‐dwelling consumers show a more dynamic response towards the plankton density and composition. Such dynamic components need to be considered when estimating total plankton consumption by the benthos.     

Attempt at ecological prognosis of the plankton in the man-made lake ‘Parana medio (Chapeton transect)’, Argentina

Characteristics of the projected man-made lake on the Middle Parana are described, as well as environmental conditions in the river and their modifications in the future lake. The sources of the future plankton are considered. The formation of the future pelagic ecosystem, mainly of the zooplankton, during the initial and the subsequent stage is discussed.     

Application of autonomous underwater vehicle and image analysis for detecting the three-dimensional distribution of freshwater red tide Uroglena americana (Chrysophyceae)

The spatial structure of Uroglena americana was detected usingan autonomous underwater vehicle equipped with a submersiblemicroscope, video recording system and water quality monitoringsensors. Uroglena americana colonies were enumerated via imageanalysis and pattern recognition methods. This quantitativetechnique is useful for understanding plankton assemblages,distributions and their potential to become nuisance algal blooms.     

Lake eutrophication and community structure

The role of external and internal phosphorus loading in the lake eutrophication was estimated according to published data and our own. The role of plankton and benthos animals has been determined in phosphorus excretion and the formation of internal nutrient load. It is shown that the term “eutrophication” is valid both in the anthropogenic and natural increases in the trophic status of the water body.