Search

Here we present a formal description of Biremis panamae Barka, Witkowski et Weisenborn sp. nov., which was isolated from the marine littoral environment of the Pacific Ocean coast of Panama. The description is based on morphology (light and electron microscopy) and the rbcL, psbC and SSU sequences of one clone of this species. The new species is included in Biremis due to its morphological features; i.e. two marginal rows of foramina, chambered striae, and girdle composed of numerous punctate copulae. The new species also possesses a striated valve face which is not seen in most known representatives of marine littoral Biremis species. In this study we also present the relationship of Biremis to other taxa using morphology, DNA sequence data and observations of auxosporulation. Our results based on these three sources point to an evolutionary relationship between Biremis, Neidium and Scoliopleura. The unusual silicified incunabular caps present in them are known otherwise only in Muelleria, which is probably related to the Neidiaceae and Scoliotropidaceae. We also discuss the relationship between Biremis and the recently described Labellicula and Olifantiella. [ABSTRACT FROM AUTHOR]

The rapid rate of habitat loss in Madagascar urges a comprehensive assessment of the threats that its fauna faces by living in fragmented, secondary and/or exotic forests. The role of habitat disturbance in determining potential boosts of parasite infections in lemurs, for instance, has been only recently investigated. Here, we conducted a preliminary assessment of prevalence and intensity of gastrointestinal parasite infections in two populations of endangered red-collared brown lemurs,Eulemur collaris(Geoffroy, 1812) (Mammalia: Lemuridae), living in two littoral forest fragments of southeastern Madagascar. We collected faecal samples from 45 lemurs. The samples were stored in 70% alcohol, and we used a modified McMaster technique to analyze egg shedding. The analysis revealed only nematode infections. We found a higher prevalence of infection in the more disturbed fragment, while no differences were revealed in terms of infection intensity. Prevalence of infection was found to be sex-biased in the less degraded area, being higher in females. We hypothesize that this might have been caused by female immune suppression due to increased energetic costs during pregnancy and/or to avoid possible harm to the foetus. Since red-collared brown lemurs are the largest seed dispersers in the littoral forest and only small populations survive in a few fragments, the implications of our results should be considered in future conservation plans for this habitat. [ABSTRACT FROM AUTHOR]

We explored δ15N compound-specific amino acid isotope data (CSI-AA) in filter-feeding intertidal mussels (Mytilus californianus) as a new approach to construct integrated isoscapes of coastal primary production. We examined spatial δ15N gradients in the California Upwelling Ecosystem (CUE), determining bulk δ15N values of mussel tissue from 28 sites between Port Orford, Oregon and La Jolla, California, and applying CSI-AA at selected sites to decouple trophic effects from isotopic values at the base of the food web. Bulk δ15N values showed a strong linear trend with latitude, increasing from North to South (from ∼7‰ to ∼12‰, R2 = 0.759). In contrast, CSI-AA trophic position estimates showed no correlation with latitude. The δ15N trend is therefore most consistent with a baseline δ15N gradient, likely due to the mixing of two source waters: low δ15N nitrate from the southward flowing surface California Current, and the northward transport of the California Undercurrent (CUC), with15N-enriched nitrate. This interpretation is strongly supported by a similar linear gradient in δ15N values of phenylalanine (δ15NPhe), the best AA proxy for baseline δ15N values. We hypothesize δ15NPhe values in intertidal mussels can approximate annual integrated δ15N values of coastal phytoplankton primary production. We therefore used δ15NPhe values to generate the first compound-specific nitrogen isoscape for the coastal Northeast Pacific, which indicates a remarkably linear gradient in coastal primary production δ15N values. We propose that δ15NPhe isoscapes derived from filter feeders can directly characterize baseline δ15N values across major biochemical provinces, with potential applications for understanding migratory and feeding patterns of top predators, monitoring effects of climate change, and study of paleo- archives. [ABSTRACT FROM AUTHOR]

Residential development on lake shores is regularly associated with the conversion of natural littoral habitats to riprap, sheet piles, beaches, parks, or marinas. The subsequent loss of littoral vegetation induces a decline of structural diversity and impacts littoral fish communities. These impacts may be shaped by lake morphology. Using boosted regression trees (BRT) to relate fish abundance data from 57 north-east German lowland lakes to various factors characterizing trophic state, lake morphology, and shoreline development, we investigated the response of 11 fish species to shoreline development. The analyses revealed that mean depth followed by trophic level and shoreline length (SL) contributed most in explaining littoral fish abundance. BRT models built for deep and shallow lakes separately confirmed that primarily trophic level and SL influenced fish abundance but that littoral vegetation was relatively more important in deep compared to shallow lakes, indicating that the effects of shoreline development may be more pronounced in deep lakes where the littoral makes up a smaller proportion of the lake area as compared to shallow lakes. The BRT further demonstrated species-specific responses to shoreline degradation, indicating that the reliability of ecological quality assessments of lakes can be improved by applying separate metrics for individual species. [ABSTRACT FROM AUTHOR]

Phragmites australis and Glyceria maxima are fast-growing littoral grasses often competing for similar wetland habitats. Eutrophication affects their competitiveness, but the outcome is not generally predictable due to the complexity of interrelated factors. We hypotheses that pore water N:P and NH:NO modify their growth and metabolic responses to the trophic status of the habitat. The hypothesis was tested under standardized conditions of long-term sand cultures. Application of N + P up to extreme levels in combination with N:P < 10 and NH:NO < 1 triggered positive growth response in both species. In contrast, similar N levels applied in N:P > 90 and NH:NO = 4 caused lower productivity, changes in resource allocation, morphology and metabolic relations (e.g. high shoot density, low shoot diameters and heights, reduced root and rhizome growth). Observed signs of stress resembled the factors associated with the reed retreat at the die-back sites. Unbalanced N levels obviously alter plant susceptibility to stresses (altering, e.g. ventilation efficiency, plant anchorage or below-ground storage capacity). The positive effect of sufficient P supply was pronounced in Glyceria. It might therefore favour Glyceria in competition with Phragmites at highly fertile habitats rich in P. [ABSTRACT FROM AUTHOR]

The main differences between the linear and areal types of littoral habitats are in their shape, structure and the hydro- and litho-dynamic, salinity and ecological gradients between terrestrial and aquatic environments. Understanding the nature of linear littoral habitats is important for interpreting the 'coastal squeeze' effect. The aim of this study is to analyse and compare the integrity of the key linear littoral habitats adjacent to two European lagoons-Lesina Lagoon on the Adriatic Sea and the Curonian Lagoon on the Baltic Sea. Among the four linear habitats selected for this study, we found that the glasswort ( Salicornia spp.) swards showed the highest level of integrity, while the reed beds showed the lowest level of integrity. The linear littoral habitats rely on the dynamic equilibrium conditions. Hence, the strip of glasswort swards and the freshwater dune slack ponds of Bosco Isola di Lesina both depend upon climatic conditions that determine the shape of the salinity gradient. This gradient runs perpendicular to the coast and is based on a transition from fresh groundwater to saline water. The chain of shifting coastal dunes and the reed beds of the Curonian Spit depend upon the long-shore hydro- and litho-dynamic flow conditions. [ABSTRACT FROM AUTHOR]

Coastal zooplankton have been investigated since 1984 at a Long Term Ecological Research station MC (LTER-MC) in the inner Gulf of Naples (Tyrrhenian Sea, Western Mediterranean). The sampling site, located between the littoral and the open sea systems, has very active hydrography that affects plankton communities. The present work was aimed at establishing whether, in such a dynamic and variable environment, species associations and homogeneous periods could be identified as characteristic and stable features of the mesozooplankton over the period 1984–2006. Hierarchical clustering was applied to assess species associations based on a matrix of similarities between species (R-mode), and homogeneous periods based on a matrix of similarities between observations (Q-mode). The Indicator Value index [IndVal, Dufrene and Legendre (1997) Species assemblages and indicator species: the need for a flexible asymmetrical approach. Ecol. Monogr., 67, 345–366] was calculated to identify species characterizing each period. Five taxonomic groups with well-defined composition and abundance were identified as robust associations that likely reflect different modes of community functioning. The temporal course of these associations was largely shaped by strong seasonal forcing comprising both physical and biological (e.g. trophic) signals. These associations persisted over the long term, thus indicating some stable characters in the Naples zooplankton time-series, providing evidence of resilience in communities in highly variable coastal conditions. [ABSTRACT FROM AUTHOR]

Mangroves occur in coastal areas and are therefore vulnerable to anthropogenic disturbance and exhibit high rates of deforestation. Mexico is among the countries with the highest degree of mangrove deforestation in America; however, precise data on national mangrove coverage in Mexico is incomplete, making it impossible to accurately ascertain the rate of mangrove loss over time. Precise information is necessary to assess changes at local and regional scales to detect the magnitude, trends, and drivers of the transformation. This study aimed to estimate the loss of mangrove cover in the area of Mahahual-Xcalak (Quintana Roo, Mexico) between 1995 and 2007, to calculate the annual deforestation rate and to identify the drivers of deforestation. Landsat TM and ETM+ images from 1995 and 2007 were used to estimate the loss of mangrove cover using a multitemporal analysis. Semi-structured interviews with local residents of Mahahual and Xcalak were undertaken to identify and validate the drivers of deforestation. The image analysis for the 12-year period showed that 1070 ha of mangrove forest have been lost, with an annual deforestation rate of 0.85%—a relatively high value compared with other mangrove regions in Mexico. The main factor that has triggered the reduction of mangrove coverage is the expansion of anthropogenic land uses (e.g., settlements and roads). This study concludes that conservation and rehabilitation programs need to be implemented so that the Mahahual-Xcalak mangrove environment can continue to provide key ecosystem services. [ABSTRACT FROM AUTHOR]

We performed a meta-analysis of published studies and long-term monitoring data sets to evaluate the effects of dreissenid mussels (Dreissena polymorpha and D. rostriformis bugensis), two of the world's most problematic biological invaders, on the biogeochemistry, flora, and fauna of lakes and rivers across North America and Eurasia. Dreissenid effects were structured along two distinct energy pathways. For the pelagic-profundal pathway, large mean reductions in phytoplankton (-35% to -78%) and zooplankton (-40% to -77%) biomass occurred and were dependent on habitat type. The largest effects were found in rivers, followed by littoral and pelagic habitats in lakes. In contrast, benthic energy pathways within littoral habitats of lakes and rivers showed dramatic increases in mean benthic algal and macrophyte biomass (+170% to +180%), sediment-associated bacteria (about +2000%), non-dreissenid zoobenthic biomass (+160% to +210%), and total zoobenthic biomass, which includes dreissenid mussel soft tissues (+2000%). Our study quantifies the remarkable ability of these invasive mussels to shift aquatic food webs and energy flow from pelagic-profundal to benthic-littoral energy pathways, and it provides a basis for forecasting their impacts in diverse freshwater ecosystems. Our meta-analysis approach was a powerful tool for moving beyond the idiosyncrasies of individual case studies and may be equally powerful for assessing impacts of other biological invaders. [ABSTRACT FROM AUTHOR]

Herbivory is typically intense in marine littoral environments; thus, macrophytes are expected to evolve defenses against grazing. Although putative defenses of macrophytes are widely studied, there is lack of studies demonstrating the main premises of defense adaptations: the consequences of herbivory to macrophytes, genetic variation of defense traits and the costs and benefits of defenses in natural environment. We conducted a factorial experiment, where we manipulated amount of herbivory, growing depth and nutrient availability, and measured resistance to herbivory as well as genetic variation and costs of phlorotannins, putative defensive secondary metabolites, in the brown alga Fucus vesiculosus. Herbivory on algae varied with depth: grazing did not cause losses close to the surface, but, most of the algal production was consumed at the deeper end of the algal belt. The higher the genotypic phlorotannin content the less damage the genotype received implying that phlorotannins acted as a resistance trait. Production of phlorotannins was associated with costs for growth. Consistent with the prediction that the cost of defense will be greatest when resources are limiting, the cost appeared only in the deep end of the algal belt where growth was slowed down. Phlorotannins displayed phenotypic plasticity; the three factors influenced phlorotannins interactively, with the main tendencies of nutrient enrichment decreasing and herbivory and increasing depth increasing phlorotannins. Despite this plasticity, variation of phlorotannins was mainly due to the genotype of algae. These results emphasize the role of herbivory as a selective agent for algal defenses and the importance of genetic variation in the constitutive level of phlorotannins in interactions with natural enemies. The cost of phlorotannins may constrain the evolution of resistance in environments where growth is limited by light availability. [ABSTRACT FROM AUTHOR]

An approach towards a systematic revision of Marionina Michaelsen, 1890 is made through an historical overview of its nomenclature and definition, and a thorough characterization of its type species, the South Georgian marine littoral Pachydrilus georgianus Michaelsen, 1888. Relevant sections of early enchytraeid literature provide the background for appreciating the complex taxonomic history of the genus and giving a final word as to the controversial validity of its name, authority and date. Marionina in its current acceptation comprises about 100 nominal species, but the paper documents how, since its establishment, the genus has been an artificial assemblage of unrelated taxa, whose taxonomy cannot be sorted out (1) without finding new morphological characters and improving the standard of descriptions, and (2) without using a total evidence approach (morphology and molecules) within a phylogenetic framework. Confusion about the identity of the type species, originally briefly described and only partially figured, is unravelled upon examination of the syntypes available in Hamburg and Berlin. Since neither series proved to be monospecific, a lectotype is designated to assure correct and consistent application of the name in the future. [ABSTRACT FROM AUTHOR]

Deglaciation took place in eastern Jämtland and Ångermanland in central Sweden c. 10 500–10 200 cal. yr BP. In the present study, vegetation development and shore displacement during the earliest ice-free period are investigated by 14C dating of sediment from six isolated lake basins and by pollen analysis. A brief but distinct peak in Hippophaë occurs in all pollen diagrams coincident with basin isolation, followed by up to 500 years (varying locally) by an Alnus rise. The Alnus curve does not display a synchronous rise in the area. Its expansion below the highest shore level is time-transgressive and controlled mainly by the timing of basin isolation. The relationship between regional Alnus expansion and changes in hydrology and climate is discussed. The pollen diagrams show Pinus predominance with Corylus to the east (more coastal areas) and Betula predominance (though less pronounced) to the west during the period 10 200–9000 cal. yr BP. However, comparisons between sites suggest marked variability in the forest development. Shore displacement in easternmost Jämtland c. 10 300–9000 cal. yr BP is equal to or slightly more rapid than that of SE Ångermanland, contrary to the present pattern of isostatic recovery. A rapid shore level regression c. 10 300–10 000 cal. yr BP may be related to drainage of the Ancylus Lake. [ABSTRACT FROM AUTHOR]

Residential development of lakeshores affects the structure and function of riparian and littoral habitats. Organic detritus in sediments is a critical component of littoral food webs, but the effects of urbanization on sediment characteristics are unexplored. We characterized the quantity of organic sediments in Pacific Northwest lakes along a development gradient and found a 10-fold decline in the proportion of detritus in littoral sediments associated with density of lakeshore dwellings. In a comparison between two fully developed lakes and two undeveloped reference lakes, we examined several possible controls on sedimentary organic content, including terrestrial inputs, decomposition rates and associated macroinvertebrate communities, and physical retention by coarse wood. The littoral sediments of undeveloped lakes ranged from 34 to 77% organic by mass, whereas the range on urban lakes was an order of magnitude less, ranging from 1 to 3% organic. We found no significant differences in terrestrial litter inputs between the two sets of lakes. Leaf litter decomposition rates did not vary significantly between the two sets of lakes, and we found higher densities of shredder macroinvertebrate taxa in the littoral zones of undeveloped lakes. Sedimentary organic matter on undeveloped lakes accumulated in shallow waters and declined with distance from shore, whereas the opposite pattern existed on urban lakes. Our results suggest that coarse wood physically retains organic matter in littoral zones where it can enter the detrital energy pathway, and the loss of this feature on urban lakes alters littoral sediment characteristics, with potentially far-reaching consequences for lake food webs. [ABSTRACT FROM AUTHOR]

Analysis of pmoA and 16S rRNA gene clone libraries of methanotrophic bacteria in Lake Constance revealed an overall dominance of type I methanotrophs in both littoral and profundal sediments. The sediments exhibited minor differences in their methanotrophic community structures. Type X methanotrophs made up a significant part of the clone libraries only in the profundal sediment and were also found only there as a prominent peak by T-RFLP analyses. [ABSTRACT FROM AUTHOR]

We measured fluxes of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) simultaneously in two typical fringing zones, sandy shore and salt marsh, of coastal lagoon, Lake Nakaumi, Japan, in mid-summer 2003. Our aim was to quantify net the greenhouse gases (GHGs) fluxes and examine key factors, which control variation of the GHGs fluxes in the two sites. Net CO2 and CH4 fluxes were markedly different between the two sites; magnitudes and variations of the both fluxes in sandy shore were lower than those of salt marsh. Meanwhile, magnitude and variation of net N2O flux in the two sites were similar. In sandy shore, temporal and spatial variation of the three GHGs fluxes were highly controlled by water level fluctuation derived from astronomic tide. In salt marsh, spatial variation of the three GHGs fluxes were correlated with aboveground biomass, and temporal variation of CO2 and CH4 fluxes were correlated with soil temperature. The sum of global warming potential, which was roughly estimated using the observed GHGs fluxes, was ca. 174-fold higher in salt marsh than in sandy shore. [Copyright &y& Elsevier]

Spatio-temporal distribution of nitrogen was examined along the gradient from open water to lakeshore in Lake Taihu, China. Two types of undulating littoral zones were selected: natural reed belt and bare lakeshore. The reed belt affected nitrogen transformation and was sink for internal-lake nitrogen, whereas the bare lakeshore showed little effect. During the growing season, NO-N concentration increased by up to 3–5 times from open water to reed belt, while NH-N concentration decreased. It suggested that nitrification was the main nitrogen process in reed belt. Total dissolved nitrogen (TDN) showed little spatial variation, indicating that most of nitrogen released from sediment did not move into open water again. Significant temporal variation of dissolved nitrogen occurred and was similar in both the littoral zone and the open water. Maximum TDN and NH-N concentrations occurred in January, and NO-N in March. Minimum NH-N and NO-N concentrations occurred in July and August, respectively. An increasing total soil nitrogen was found in the surface sediments from reed belt to open water. This further suggested that the reed-covered littoral zone had strong nitrogen transformation potential. [ABSTRACT FROM AUTHOR]

Toxic cyanobacteria can have harmful or fatal impacts on aquatic organisms. In the archipelagos of the northern Baltic Sea, the open sea blooms often drift into littoral areas, where they decompose and release toxins and other chemical compounds in the water. However, the effects of cyanobacteria on the littoral organisms have not previously been investigated. We studied the effects of three cyanobacteria species (toxic Nodularia spumigena, non-toxic N. sphaerocarpa and non-toxic Aphanizomenon flos-aquae) and purified dissolved nodularin (produced by N. spumigena) on a common littoral amphipod Gammarus zaddachi. Nodularin was transferred to eggs, juveniles and adults of G. zaddachi, but no significant negative effects of dissolved nodularin were detected on adults, eggs or juveniles. However, survival of adults decreased by the exposure to toxic N. spumigena cells. The egg hatching rate and juvenile survival were not affected when exposed to the three cyanobacteria species. In contrast, a weak decrease in the egg production and an increased abortion of embryos from the brood pouch of females was observed, the later indicating a failure in parental care. Further, a decrease in grazing rate on the filamentous green alga Enteromorpha intestinalis was observed. The results suggest that toxic cyanobacteria blooms are not extremely fatal, but may have, in high concentrations, negative effects on the adult survival, fecundity, and feeding behaviour of gammarids inhabiting the littoral zone. [ABSTRACT FROM AUTHOR]

We used natural abundance stable isotopes to establish the structure of the littoral zone food web of an oligotrophic, perched dune lake on Fraser Island, Australia. Mixing model analyses incorporating riparian vegetation, seston, and periphyton sources indicated that periphyton carbon was the most significant food resource for aquatic consumers, despite the abundance of allochthonous carbon sources. In order to examine the consequences of nutrient inputs from tourists visiting this remote lake, repeated additions of low levels of phosphate and 15N-enriched ammonium nitrate were made to three littoral zone sites. Additions led to significant increases in periphyton chlorophyll a (Chl a) concentrations in enriched sites but had no measurable effect on phytoplankton Chl a concentrations. Periphyton collected 5 h after the first nutrient addition had substantially enriched δ15N signatures, suggesting that periphyton rapidly assimilated the added nutrients (and 15N-tracer). After l0 d of additions, all other primary food sources for consumers also became 15N-enriched, indicating that ongoing nutrient inputs are likely to lead to increased primary production and detrital processing. Substantially enriched consumer δ15N signatures were also measured, indicating that the added nutrients were assimilated and passed through multiple trophic levels. Our results indicate that ongoing low-level nutrient additions by tourists to oligotrophic lakes could lead to increased primary (periphyton) and secondary (consumer) production. However, increases in periphyton production and biomass accrual could eventually escape control by grazers, leading to adverse ecological and aesthetic effects. [ABSTRACT FROM AUTHOR]

Variations in the attenuation of photosynthetically available radiation were analysed using extensive spatial sampling in two seasons in a subtropical wetland lake. Simultaneously with the attenuation measurements, the principal absorption and scattering components of the water column were also measured. The elevated spatial resolution used in the study allowed the determination of spatially distinct optical water classes within the lake. Changes in dissolved organic matter, phytoplankton and tripton concentrations led to a wide variation in the vertical attenuation coefficients. These changes depended on local characteristics of the ecosystem and time of year. The spatial distribution of the attenuation coefficients was examined in relation to the hydrological and geomorphological characteristics of the littoral area of the lake. The impacts of two small rivers on the light environment and attenuation components are shown. Finally, the resulting model was used to examine the possible impacts of changes in light availability at the lake bottom in relation to recent changes in lake water level. [ABSTRACT FROM AUTHOR]

We studied the structural characteristics of the littoral epilithon in nine lentic water bodies at Hope Bay, Antarctic Peninsula, during summer 2002. At each site we measured the main physical and chemical variables and took epilithic samples for the analysis of dry weigh, ash, ash-free dry weight and chlorophyll a concentration. Distance from the sea of each water body was also considered. One site was selected for sampling lakes and ponds, except for Boeckella lake, where two sampling sites (A and B) were selected due to the heterogeneity of its littoral zone. Three stones for chlorophyll a analysis and another three to estimate dry weight, ash and ash-free dry weight, were taken randomly about 1 m away from the shore-line of each sampling site. Measurements of physical and chemical characteristics were obtained similarly. Water samples for chemical analysis were taken sub-superficially. Lakatos's system of classification and the Autotrophic Index were used to make functional inferences about the epilithic communities. Two PCA analyses were made to classify the water bodies according to environmental features and epilithic variables. In the latter, major patterns in data of epilithon were subsequently interpreted based on environmental data using external validation. Pingüi pond, located in the middle of the penguin rookery, was considered as a passive sample in both PCA analyses due to its extreme characteristics. Limnological features of the studied water bodies were similar to those of other Maritime Antarctic lakes. According to the Lakatos's index, 60% of the sampled lakes had high epilithic mass and a same proportion showed an inorganic type of epilithon The fact that 40% of the water bodies were autotrophic confirmed the importance of benthos as primary producer. According to environmental features, the well-defined groups of lakes emerged from the PCA were mainly determined by distance from the sea, pH, conductivity and salinity, and corresponded to the principal hydrological basins found in the region. Based on the results of the second PCA, littoral epilithon was affected by nitrate concentration and conductivity. In this ordination, water bodies from the same hydrological basin were separated probably as a result of a very complex inter-play of factors with a site-specific response to particular microhabitat characteristics. [ABSTRACT FROM AUTHOR]

Diversity and community structure of aerobic methane-oxidizing bacteria in the littoral sediment of Lake Constance was investigated by cloning analysis and terminal restriction fragment length polymorphism (T-RFLP) fingerprinting of the pmoA gene. Phylogenetic analysis revealed a high diversity of type I and type II methanotrophs in the oxygenated uppermost centimeter of the sediment. T-RFLP profiles indicated a high similarity between the active methanotrophic community in the oxic layer and the inactive community in an anoxic sediment layer at a 10-cm depth. There were also no major changes in community structure between littoral sediment cores sampled in summer and winter. By contrast, the fingerprint patterns showed substantial differences between the methanotrophic communities of littoral and profundal sediments. [ABSTRACT FROM AUTHOR]

In situ mesocosm experiments were performed under summer (1997) and winter (1999) conditions in the littoral zone of a subtropical lake in Florida, USA. The objective was to quantify phosphorus (P) accumulation by various components of the community after adding pulsed doses of dissolved inorganic P. A short-term experiment also was done to quantify the rate of P loss from the water column, with simultaneous use of an inert tracer to confirm that P depletion was not due to leakage of the tanks. In the experiments, added P was rapidly removed from the water; samples collected 3–4 days after adding spikes of near 100 μg l-1 P contained little or no soluble reactive P. In the short-term experiment, we documented that the half-life of added P was approximately 6–8 h in the water column, and that the tanks were not exchanging water with the surrounding lake. Little of the added P ended up in plankton, rooted vascular plants, or sediments. The main sink for P was periphyton, including surface algal mats, benthic algal mats and detritus, and epiphyton. In the summer 1997 experiment, the periphyton was intimately associated with a non-rooted plant (Utricularia), which also may have sequestered P from the water. Structure of the littoral community varied between summer and winter, and this influenced which periphyton component accounted for most of the P removal. In regard to P mass balances, we accounted for 54% of the added P in 1997, when coarse sampling was done. In 1999, when there was more detailed sampling of the community, 92% of the added P was located in various community components. Subtropical littoral periphyton can be a large sink for P, as long as depth and underwater irradiance conditions favor its growth. [ABSTRACT FROM AUTHOR]

During the last ten years two new species of gammarids, Gmelinoides fasciatus (Stebb.) and Pontoganunarus robustoides (Sars), invaded the Gulf of Finland. We studied the distribution and abundance of these species and their effects on littoral communities in the Neva estuary in 1998 -- 2002. The study was performed in three types of habitats: Phragmites australis beds, exposed stone littoral, and Cladophora glomerata mats on stones. Feeding rates of the gammarids consuming filamentous algae and benthic invertebrates were estimated experimentally. Intensive consumption of plant food (Cladophora, roots and debris of Phragmites) by gammarids resulted in the production of faeces that increases organic matter availability for benthic detritivores. At the same time, gammarid predation resulted in a decrease of benthic invertebrates. The magnitude of the effects depended on the density of the established species and the type of habitat. In addition, an experimental study of interactions between G. fasciatus and P. robustoides revealed the existence of intraguild predation, which was the strongest in the case of P. robustoides. [ABSTRACT FROM AUTHOR]

Top predators in food webs can have substantial effects on species lower down in several levels of a food web. Most trophic levels in natural systems are heterogeneous, that is, they consist of many species that differ in a number of ecological characteristics including vulnerability to predators. Use of resources and response to abiotic factors showed theoretically that a wider range of responses to enrichment are possible in multitrophic levels systems, when each trophic level consists of more than one species rather than when treated in the aggregate, as in the classical theory.

Three successive emergent macrophytes (Typha latifolia L., Phragmites australis (Cay.) Steudel and Glyceria maxima (Hartman) Holmbly) were each grown in substrates collected from three different zones of shoreline vegetation development (non-vegetated sediment, the interface between T. latifolia and P. australis, and degenerating P. australis). The aim of the study was to assess whether accumulation of litter changes growth conditions of P. australis, and to determine its effects on pre- and post successional plant species. The study was carried out by means of pot experiments in a glasshouse. Seedlings of the three species were cultured in fertilized and unfertilized substrates under both waterlogged and drained conditions. In its own litter, growth of P. australis was strongly reduced, compared with the productivity of plants in substrates from preceeding successional stages, and could not be compensated for by fertilization or soil drainage. The redox potential of the substrate was not strongly reduced and the sediment density was well above the critical level. Soil sterilization by gamma-irradiation did not improve growth substantially, although there was some positive effect in unfertilized substrate. Phytotoxic compounds might have caused poor growth of P. australis in its own litter. T. latifolia and G. maxima were relatively less affected by the P. australis litter. The possible importance of litter accumulation on species replacement in shoreline vegetation is discussed. It is concluded that the accumulation of organic matter should be considered as a factor affecting spatio-temporal processes in littoral vegetation owing to its specific impact on the functioning of individual dominant plant species. [ABSTRACT FROM AUTHOR]

Cottage development in central Ontario affected mink habitat and food selection by altering vegetation structure and distribution, species composition of vegetation, and prey availability. Lot-clearing activities by cottagers reduced tree and shrub densities, foliage volume, deadfalls and shade-loving ground species while increasing the number of alien or domesticated plant species. The littoral zone was simplified by the removal of submerged snags, large boulders or stones, submergent, emergent, and floating vegetation in favour of sand beaches and docks. Mink activity decreased with increasing levels of development, as measured by a development index, and increased with increasing coniferous composition. Deciduous shorelines were not used much by mink regardless of the level of development. The occurrence of fish, amphibians and crustaceans in the diet was affected by the intensity of development while the occurrence of mammals, crustaceans and amphibians in the diet was affected by the coniferous composition of the habitat. It is important to understand these changes in order to manage the development to minimize negative impacts on wildlife. [ABSTRACT FROM AUTHOR]

An abstract of the article "Ostracod assemblages in various littoral plant communities of a shallow lake (Lake Swidwie, Poland)," by Agnieszka Szlauer-Łukaszewska is presented.