Isotope Composition of Nitrogen and Stoichiometric Ratios of Elements in Biomass of Spirogyra in Lake Baikal.

Using stable isotope analysis of nitrogen, for the first time the hypothesis on different sources of inorganic nutrients for two groups of littoral algae in Lake Baikal was confirmed. Strongly attached filamentous algae of genus Ulothrix, which developed in the wave-braking zone at depth 0.5 m, and loosely attached filamentous algae of genus Spirogyra, which developed in deeper layers 3.0-5.0 m in a low-turbulence zone, get inorganic nutrients presumably from surface discharge and groundwater inputs, respectively. Besides, stoichiometric ratios C:N and N:P in biomass of the algae indicated that growth of Spirogyra in Lake Baikal was likely limited by nitrogen, while growth of Ulothrix was limited by phosphorus.

Impact of the third-order dispersion on the modulation instability gain of pulsed signals.

We demonstrate that modulation instability gain of time-localized signals (i.e., pulsed signals) depends strongly on the third-order dispersion, contrary to the well-known case of time-extended signals (cw signals). This surprising contribution of an odd dispersion term on this four-photon-mixing process is established analytically and confirmed by numerical simulations.

Observation of extreme temporal events in CW-pumped supercontinuum.

We study experimentally and numerically the temporal features of supercontinuum generated with a continuous-wave ytterbium-doped fiber laser. We show that the temporal output of the supercontinuum is characterized by strong and brief power fluctuations, i.e. so-called optical rogue waves. We demonstrate numerically that these rare and strong events that appear and disappear from nowhere result from solitonic collisions.

[Self-similar properties of the spatial structure of intertidal macro- and microbenthic communities].

Spatial distribution (SD) of White Sea intertidal soft-bottom communities was studied at scales from decimetres to dozens of kilometres on the basis of an extensive dataset (464 samples of macrofauna, 349 samples of ciliates, and 333 samples of diatoms). We used the information index of structural heterogeneity D(I) (Azovsky et al., 2000 // Mar. Biol. 136 (3): 581-590) to characterize spatial variability in the species composition of the communities at different extent (total area surveyed) and grain (finest spatial resolution). The type of distribution was determined via the relation between D(I) and parameters of the spatial scale (extent and grain). At small scale (in terms of extent), all the communities were distributed randomly (mosaic SD). At larger scales, the estimated spatial variability depended neither on extent nor grain, exclusively on their ratio, i.e., was scale-invariant. This means that at some scale the spatial patterns of communities display self-similar properties (fractal SD). Such SD was found at a rather wide range of scales scales: 10(1)-10(4) m for the macrofauna, 10(0)-10(3) m for the ciliates, and 10(-1)-10(2) m for the diatoms. At still greater scales, patchy or gradient patters were observed. Thus, the ranges of fractal distribution were proportional to the average size of the organisms (approximately 10(4)-10(7) times the body size). We suppose that such spatial pattern reflects community self-organization in a relatively homogeneous environment and may be the most efficient way to realize the highest structural diversity on the basis of pre-formed complexes of predominant species. We also suppose that fractal-like patterns may be a general feature of the spatial organization of communities.

[Initiation of self-organization processes in community of marine microbenthos by application of nutrients in super-high concentrations]. / Initsiirovanie protsessov samoorganizatsii v soobshchestve morskogo mikrobentosa sverkhvysokimi kontsentratsiiami biogennykh élementov.

The influence of high concentrations of mineral nitrogen, phosphorus and their mixtures on species structure of microbenthos of a sand intertidal zone of the White Sea was studies in field experiment. The increase in concentration of nutrients (in comparison with natural) reduces the species diversity and organism abundance in grazing chains, but stimulates the development of organisms of detrital food chain. At abnormally high concentration of nutrients the response of community does not strictly depend on chemical composition of fertilizers and N:P atomic ratio. The high concentration of nutrients act as distructive agent on the complex organized system and simultaneously as a specific trigger of self organization processes, which re resulted in formation of highly coherent commynity of r-strategists (bacteria and protists). After termination of the experiment and resetting of environment to the previous state, the new community for a long time (measured by dozens of generations of unicellular organisms) retains its structure.

[Annual cyclic changes and self-organization processes in the marine sea-bottom organisms]. / Godovye tsiklicheskie izmeneniia i protsessy samoorganizatsii v soobshchestve morskogo mikrobentosa.

The dynamics of marine microbenthos species structure shows clear annual cycle. From late winter till early autumn community changes towards increasing complexity and orderliness. The sharp increase in available energy (light and heat) in the beginning of the winter acts as trigger of these processes. The further development of the community is connected with system fluctuations arising as a result of interactions or organisms between each other and their environment (feeding, competition, predation). In the end of summer these processes are terminated by the state of high species diversity, maximum species coordination, expansion of inhabited zone within the sediments, and the distinct segregation of space and nutrient resources among species (i.e., achievement of ecological complementarity). Decrease in light and temperature causes the reverse process--weakening of organism coordination and significant simplification of the community structure. In general, these changes correspond to the theory of self-organization in nonequilibrium systems (Prigogine, Stengers, 2001). The most important distinction of observed processes from the classical self-organization is their cyclic dynamics, i.e. the annual return of community to its most simple state at the end of winter.