The ecological mechanisms of the formation of macrobenthos communities in the coastal area of small diverse lakes

The author analyses trophic structure of macro invertebrates inhabiting samples of litter settled (deciduous leaves) in three small lakes with different hydrochemical characters. In acid lake predators and detritovores-collectors are dominant, in slightly acid lake predators, detritovores-filtrators and collectors are the main types. Trophic structure of acid lakes is formed by acid-tolerant species adopted to low pH. In slightly acid lakes circumneutral species are developed. It was shown that trophic structure is formed mainly under influence of biotic factors and is not strongly depended on pH and trophic levels. Vertical distribution of organisms is determined by oxygen regime.     

Assemblages of bloodsucking mosquito larvae (Diptera: Culicidae) in water bodies of the northern Kulunda steppe

The population structure of bloodsucking mosquito larvae in temporary and constant water bodies of the northern Kulunda steppe was investigated. The seasonal dynamics of the population density, the number of species in different types of reservoirs, and average density of each species are given. The productivity of water reservoirs in relation to mosquitoes of the family Culicidae is analyzed. The basic factors affecting the distribution of larvae of dominant species between different water bodies were revealed. The degree of correlation between the structure of bloodsucking mosquito larva assemblages and the type of the reservoir was established.     

Nonindigenous invertebrates in the periphyton and benthos of upper Volga reservoirs: A review

The mechanisms, ways, and traits of acclimatization of aquatic animals within and outside their historical ranges are reviewed. It is shown on the example of the upper Volga basin that formation still continues of the fauna in reservoirs that began after their impoundment during 1930s–1950s. It is also shown that Ponto-Caspian invaders and intentionally introduced Baikal amphipods play a great role in this process. The data on the traits of biological cycles of mass nonindigenous invertebrates in upper Volga reservoirs are presented. The main ecological factors facilitating expansion of new species in reservoirs are demonstrated. It is shown that the assessment of the functional role of dreissena in waterbodies should include determination of the abundance of the larvae of this species in plankton.     

State of the Ichthyoplankton Community along the Crimean Peninsula in August 2011

Data on species composition, spatial distribution of ichthyoplankton, and feeding of fish larvae in August 2011 are presented for the shelf and the open waters along the Crimean Peninsula from Kerch Strait to Karkinit Bay. In the ichthyoplankton, fish eggs and larvae represented 19 species from 16 families. The average egg abundance was 111 egg/m² and larvae abundance was 22 ind./m². The elimination ratio of the European anchovy Engraulis encrasicolus, which dominates in the plankton from the final stages of development to the prelarvae in 2011, was similar to that observed in 1957. The high number of larvae of the older age group in the western halistatic zone is explained by the peculiarities of the hydrological regime. Decrease in the pressure of predatory jelly macroplankton and an fodder zooplankton (zooplankton abundance) contribute to the survival of the fish larvae.     

Interrelations between chemical composition of water and characteristics of zooplankton in the Novosibirsk reservoir

On the basis of an analysis of the long-term data of hydrochemical and hydrobiological monitoring of the Novosibirsk reservoir, the mutual influence of the chemical composition of water and qualitative and quantitative characteristics of a zooplankton has been revealed. The influence of the hydrochemical factors on the zooplankton is related to the peculiarities of the hydrological regime of the water basin. High correlations between the quantity of zooplankton and pH values, the concentration of nitrites and nitrates, and the values of 5-day biological oxygen demand (BOD₅) are revealed. Three basic parts of the water basin, different in the level of influence of hydrological factors and intrareservoir processes on the hydrochemical and hydrobiological characteristics of the ecosystem of the reservoir, are revealed. It is shown that, as a whole, the intrareservoir processes that occurred in the reservoir improve the quality of water in many hydrochemical indicators.     

On the fauna of chironomidae (Diptera) of the Hrazdan Basin (Armenia)

A faunistic review of larvae and pupae of chironomid midges (Diptera, Chironomidae) from 15 habitats in the Hrazdan River valley (Armenia) is presented. The revealed fauna includes 40 species from 20 genera and 6 families and tribes. Diploid chromosome numbers are specified for 24 species from 13 genera and 4 subfamilies; 23 species from 14 genera and 4 subfamilies are reported from the region for the first time. Predominant oligotrophic status is confirmed for most of the reservoirs studied.     

Effects of common carp (<Emphasis Type="Italic">Cyprinus carpio</Emphasis>) and bream (<Emphasis Type="Italic">Abramis brama</Emphasis>) on the structure of the littoral community in a mesotrophic lake (Mesocosm Experiments)

The effect of common carp and bream on hydrochemical parameters, abundance, and structure of phyto-, zooplankton, and macrozoobenthos has been studied in semienclosed mesocosms installed in the littoral zone of a mesotrophic lake. Significant differences in the biomass of different algal groups in mesocosms with fish in respect to the control were established only for diatoms and were not found for other phytoplankton groups. Common carp had a greater effect on the abundance of large zooplankton species (Diaphanosoma brachyurum) compared to bream. The abundance of the small Bosmina longirostris increased in mesocosms both with bream and common carp. The macrozoobenthos biomass reduced at higher rates in mesocosms with common carp than in those with bream, with the strongest effect of common carp on mayfly larvae. The differences between the consumption of chironomid and oligochaete larvae were not established in mesocosms with common carp. Bream mainly affected the larvae of mayflies and oligochaetes and, to a lesser degree, the chironomid larvae.     

Chironomids (Diptera,Chironomidae) fauna of reservoirs in Bashkortostan

An annotated list of chironomid species from small reservoirs located in the Republic of Bashkortostan in the basins of Kama, Ural, and Ob rivers is given. The list includes 54 valid species. In addition, data on the abundance of larvae in the studied waters are presented. A total of 60 species of 31 genera from 3 subfamilies, Tanypodinae (5), Orthocladiinae (18), and Chironominae (37), are recorded. The largest number of species is registered in the Sakmara Reservoir. Palearctic species dominate.     

The role of food plant and pathogen-induced behaviour in the persistence of a nucleopolyhedrovirus

Insect baculoviruses can survive between epidemics as infectious particles external to the host. Many pathogens persist in reservoirs, i.e., microhabitats where survival is enhanced, for example due to protection from the degrading effects of UV irradiation. However, the probability of infecting new susceptible hosts is usually reduced. Persistence of pathogens and their movement in and out of reservoirs is an important, albeit little understood, aspect of insect pathogen ecology. This study investigated interactions between the behaviour of infected insect hosts, virus distribution and plant species on the persistence of the winter moth (Operophtera brumata) nucleopolyhedrovirus. Habitat influenced the persistence of infectious baculovirus in the field: virus on Sitka spruce (Picea sitchensis) and oak (Quercus robur) in forested areas retained more infectivity than virus on heather (Calluna vulgaris) in an unshaded habitat. Plant species per se did not directly affect the persistence of virus on the foliage of potted seedlings. Virally infected insects had altered behaviour and moved down plants relative to control insects, whereas in other systems larvae show height-seeking behaviour. Consequently, the majority of virus particles were distributed on plant stems. In two experiments (one using winter moth NPV and one Mamestra brassicae NPV) virus persisted better on plant stems relative to foliage. Neonate larvae were shown to be able to acquire infections from tree stems contaminated with a low level of virus. These data suggest that plant stems may be important reservoirs for between-year persistence of this pathogen. The observed virus-induced changes in host behaviour in winter moth could enhance the viral persistence by increasing the deposition of occlusion bodies in these reservoirs.     

Fish in Reservoirs

In all reservoirs the fish fauna is recruited from their riverine antecedents. The nature of the riverine environment, created by its unstable hydrological regime, favours the evolution of generalist species. Of these species, only a few are preadapted to lacustrine conditions. When riverine fish communities are trapped in a reservoir, most of the fish stay close to the shore, the mouth of tributaries and in shallows. The pelagic and deep waters are poorly utilized and the yield of fish is below the natural productivity of these water bodies, especially in the case of deep and large reservoirs. This occurs unless the dammed river contains fish species from families which are preadapted for lacustrine conditions. A positive correlation between the percentage of pelagic fish and the total yield of fish in reservoirs indicates that the pelagial represents a vacant habitat, only seldom invaded by riverine species. This situation probably applies to the deep water of reservoirs too, although sufficient data to demonstrate this are not available. The littoral region of reservoirs is utilized by some generalists of euryoecious species derived from the indigenous riverine fauna which may be preadapted for lacustrine conditions. If such preadapted lacustrine species are not present, the introduction of lacustrine species or those preadapted for the lacustrine environment is desirable under certain circumstances. However, caution must be exercised in any introduction.     

Influence of long-standing changes of hydrological and hydrochemical regime of Novosibirsk reservoir on ecological conditions of water use

The paper investigates the potential use of Novosibirsk reservoir for organizing water supply, including drinking water, of the large city and adjacent territory. The characteristics are given of the long-standing formation of hydrological and hydrochemical regime of the reservoir and its influence on the ecological conditions of water use.     

Planktonic Fauna of Small Reservoirs in the Komi Republic

One hundred and eight species and forms of planktonic organisms have been revealed in three small reservoirs in the Komi Republic (the northeast of European Russia). Species that were not previously known for the water bodies of the Vychegda River Basin (Limnosida frontosa) and the Republic of Komi (Lecane mira, Macrochaetus subquadratus, Filinia longiseta limnetica, and Rhynchotalona falcata) have been found. It has been established that the richness of the planktonic fauna depends on the age of the water body: the maximum number of species is found in the oldest reservoir, namely, the Kazhim Reservoir. The planktonic communities of artificial reservoirs are distinguished by a low level of similarity of faunas both with each other and in comparison with the natural lakes of the region. The fauna distribution in the old reservoirs is uneven. The relatively large fauna richness of planktonic communities in the littoral zones is due to the water-level regime in the reservoirs.     

Effects of prey density and short term food deprivation on the growth and survival of American shad larvae

Growth and survival of 16-and 18-day-old American larvae ( Alosa sapidissima ) increased with prey density (0, 500, and 1000 Artemia l⁻¹), though differences were not always significant. Significant differences were not observed in growth parameters and survival for larvae fed 500 v . 1000 Artemia 1⁻¹ in laboratory experiments. Food deprivation for as little as 2 days had significant effects on survival but growth effects were not detectable until 4 days of starvation. These findings have application to the Susquehanna River where c . 11 million 2.5-week-old shad larvae are released annually as part of a basin wide effort to restore the species. Larvae released at upriver sites where food may be limiting would drift for 2–3 days to reach reservoirs with higher prey densities. Based on these laboratory findings, survival of shad may be reduced significantly if larvae do not feed prior to reaching reservoir environments.     

Reach-scale distribution dynamics of a grazing stream insect, Micrasema quadriloba Martynov (Brachycentridae, Trichoptera), in relation to current velocity and periphyton abundance

Reach-scale temporal shifts in the distribution of larvae of a grazing caddisfly, Micrasema quadriloba (Brachycentridae), were investigated in a Japanese mountain stream. The larvae showed an aggregated distribution within the reach at the beginning of the immigration, then became randomly dispersed throughout the reach as the immigration progressed. The abundance of periphyton in the reach decreased dramatically with increasing dispersal of the larvae. Simple regression analyses revealed that the stream's flow regime was the most important environmental factor that determined the reach-scale distribution of the larvae and that the relationship between the flow regime and the distribution of the larvae shifted temporally. In addition, our results suggest that only this species of grazing insect, which was dominant in the study reach, controlled the reach-scale abundance of the periphyton.     

Prepared for the future: A strong signal of evolution toward the adult benthic niche during the pelagic stage in Labrid fishes

The morphology of organisms reflects a balance between their evolutionary history, functional demands, and biomechanical constraints imposed by the immediate environment. In many fish species, a marked shift in the selection regime is evident when pelagic larvae, which swim and feed in the open ocean, settle in their adult benthic habitat. This shift is particularly dramatic in coral‐reef fishes, where the adult habitat is immensely complex. However, whether the adult trophic ecotype affects the morphology of early‐life stages is unclear. We measured a suite of 26 functional‐morphological traits in the head and body of larvae from an ontogenetic series of 16 labrid species. Using phylogenetic comparative methods, we reconstructed the location of adaptive peaks of larvae whose adults are associated with different trophic ecotypes. We found that the morphospace occupation in these larvae is largely driven by divergent adaptations to the adult benthic habitats. The disparity between adaptive peaks is achieved early and does not monotonically increase with size. Our findings thus refute the notion that larvae rapidly acquire the trophic‐specific traits during a metamorphic period immediately prior to settlement. This early specialization might be due to the highly complex musculoskeletal system of the head that cannot be rapidly modified.     

Biotopic distribution and conditions for development of bloodsucking mosquitoes from the subfamily culicinae in Daghestan

The distribution of 21 species of bloodsucking mosquitoes was studied in Daghestan. The relationships between the distribution and number of mosquitoes and the environmental conditions were determined. The hydrological regime, specific features of overgrowing and warming of water bodies affect the distribution of mosquito larvae.     

The potential for cryopreserving larvae of the sea urchin, Evechinus chloroticus

Larvae of the sea urchin, Evechinus chloroticus, at varying stages of development, were assessed for their potential to survive cryopreservation. Ethylene glycol (EG) and dimethyl sulphoxide (Me2SO), at concentrations of 1-2 M, were evaluated as cryoprotectants (CPAs) in freezing regimes initially based on methods established for freezing larvae of other sea urchin species. Subsequent work varied cooling rate, holding temperature, holding time, and plunge temperature. Ethylene glycol was less toxic to larvae than Me2SO. However, no larvae survived freezing and thawing in EG. Larvae frozen in Me2SO at the gastrula stage and 4-armed pluteus stage regained motility post-thawing. The most successful freezing regime cooled straws containing larvae in 1.5 M Me2SO from 0 to -35 degrees C at 2.5 degrees C min(-1), held at -35 degrees C for 5 min, then plunged straws into liquid nitrogen. Motility was high 2-4 h post-thawing using this regime but decreased markedly within 24 h. Some 4-armed pluteus larvae that survived beyond this time developed through to metamorphosis and settled. Different Me2SO concentrations and supplementary trehalose did not improve long-term survival. Large variation in post-thaw survival was observed among batches of larvae produced from different females.     

Chironomus species (Diptera: Chironomidae) in the profundal benthos of Spanish reservoirs and lakes: factors affecting distribution patterns

• 1 The taxonomy, distribution and habitat preferences of Chironomus larvae from profundal benthos of reservoirs and natural lakes in Spain are presented. The 114 water bodies studied were medium to large reservoirs and lakes throughout Spain, and were visited on at least two occasions (summer and winter). Out of the natural lakes investigated, Chironomus larvae were found only in one karstic lake (Banyoles), and to date, these have not been found in the high mountain lakes of the Spanish Pyrenees or Sierra Nevada, or in Spain's largest oligotrophic lake (Sanabria).
• 2 Multiple regression with environmental data from reservoirs showed that the density of Chironomus larvae was inversely correlated with water depth, temperature and sulphide content of the bottom water, but positively correlated with alkalinity and particulate organic nitrogen (PON) content of bottom water. Thus, the density of Chironomus larvae was higher in shallow reservoirs from the eastern part of Spain (calcareous water and higher PON), but markedly lower in southern reservoirs (higher temperature and higher sulphide).
• 3 According to morphological and cytological characteristics, three species of this genus have been identified in the samples examined: C. bernensis, C. plumosus and C. nuditarsis. Reasons for the absence of other widespread European species are discussed.
• 4 Using canonical correspondence analysis to relate species and environmental variables, C. bernensis showed a significant preference for reservoirs with higher oxygen concentrations in bottom water and lower total reactive phosphorus (TRP) content at the surface than those reservoirs where C. plumosus‐type were found. This suggests that the smaller C. bernensis prefers mesotrophic reservoirs and the larger C. plumosus‐type (C. plumosus + C. nuditarsis) prefers eutrophic reservoirs. Taking into account the TRP/depth index for those samples collected at depths below the thermocline, and thus, where oxygen can be a limiting factor, C. bernensis and C. nuditarsis were present in reservoirs in which the index was low (< 1:170 for C. bernensis and >1:800 for C. nuditarsis), while C. plumosus thrived in reservoirs with higher index values (<1:20). These differences may reflect the preference of C. bernensis and C. nuditarsis for detrital material, while C. plumosus prefers phytoplankton. These observations are in agreement with the depth distribution of each species: C. plumosus was restricted to reservoirs less than 46 m deep, whereas the other two species (i.e. C. bernensis and C. nuditarsis) were found up to depths of 65 and 80 m, respectively.
• 5 Data from a transect (5–20 m deep) in Lake Banyoles are consistent with the general pattern described in reservoirs. In this lake, a high density of C. bernensis was recorded from littoral and sublittoral areas with abundant oxygen (above or close to the thermocline), whereas C. plumosus was scarce in several parts of the lake, especially in oxygen‐deficient areas during the summer. This karstic, oligotrophic lake has a low TRP/depth index, and therefore, we expected C. bernensis to be dominant in the littoral, as is the case. Nevertheless, the severe depletion of oxygen caused by meromixis, and the high hydrogen sulphide concentration benefit C. plumosus in deeper zones. Chironomus nuditarsis was scarce in Lake Banyoles and only found at considerable depths.

     

How to survive as a pioneer species in the Antarctic benthos: minimum dispersal distance as a function of lifetime and disturbance

Very few details exists concerning the dispersal traits of Antarctic species and dispersal distances in particular are mostly unknown. Especially the general low number of mesoplanktonic larvae has caught attention, leading to the formulation of Thorson’s rule. From this concept, originally concerning only trophic aspects, sometimes a reduced dispersal distance is deduced. Using a generic simulation model we show that in a benthic habitat exposed to iceberg scouring, even short dispersal phases of few hours are sufficient for a pioneer species to persist. This is very surprising for a pioneer species which should be able to disperse widely and colonise distant disturbed areas which are free of superior competitors. Our model revealed that the reason for this is the non-linear dependence of the dispersal distance on the disturbance regime and on species longevity. Thus, it is the combined effect of life history and disturbance traits which is important here: a sufficiently high disturbance frequency due to iceberg scouring and a long individual lifetime due to the low temperature decrease minimum dispersal distances required for persistence and thus coexistence and present an additional explanation for the relative rarity of planktonic larvae.     

Annual dynamics of the abundance of fish larvae and its relationship with hydrological variation in the Pearl River

We studied daily periodicity, taxonomic composition and annual variation of fish larvae abundance from a survey of the Zhaoqing section of the Pearl River over a 3-year period, 2006–2008, and collected 52 species, in eight families and 16 orders. The fish larval samples were numerically dominated by six species, Barbel Chub (Squaliobarbus curriculus) 33.1%, Black Guangdong Bream (Megalobrama hoffmanni) 20.6%, Yellowfin (Xenocypris argentea) 15.4%, Mud Carp (Cirrhina molitorella) 10%, Common Sawbelly (Hemiculter leucisculus) 4.3%, and Freshwater Bream (Parabramis pekinensis) 3.1%. These six species accounted for 86.5% of total numbers. Black Carp (Mylopharyngodon piceus), Grass Carp (Ctenopharyngodon idellus), Silver Carp (Hypophthalmichthys molitrix) and Bighead Carp (Aristichthys nobilis) are four of the most economically important fish species in China, and accounted for approximately 4.6% of the total. When compared with historical records from 1931, there are obvious changes in the fish larvae community. Chinese Sturgeon (Acipenser sinensis), Seasonal Shad (Macrura reevesi) and Long Spiky-head Carp (Luciobrama macrocephalus) populations have disappeared and there are also decreases in several other economically important fish populations. We observed a delay in spawning time of Black Carp, Grass Carp, Silver Carp and Bighead Carp, which may be the result of the hydrological regime change in the Pearl River. We used canonical correspondence analysis (CCA) and cross-covariance function (CCF) to analyze the relationship between fish larvae and environmental variables. Our results clearly show that discharge affects the majority of fish larvae, with the various species having different responses. Larval abundances of 15 species such as Black Carp, Grass Carp, Silver Carp, Bighead Carp, Mud Carp and Black Guangdong Bream are significantly and positively related to the discharge. Other species such as Chinese Noodlefish (Leucosoma chinensis) and Rhinogobius olivaceus are negatively related to the discharge. Abundances of larval Mosquitofish (Gambusia affinis), Common Carp (Cyprinus carpio) and Eleotris oxycephala were not related to the discharge. As most economic fish species are affected by discharge, we also conclude that changes of hydrological regime, mainly caused by river damming, will result in the decline of fisheries resources in the Pearl River. The findings of this study have important implications for our ability to model the responses of fish larvae to environmental flows for the purpose of river regulation.