ENCENTRUM ESSEXIS SP. N. (MONOGONONTA: DICRANOPHORIDAE), A NEW ROTIFER INHABITING STREAM BENTHOS FROM EAST ENGLAND

A new species of Rotifera belonging to the genus Encentrum (Monogononta, Dicranophoridae) is described from benthos of the Blackwater River, East Anglia, Essex, England, UK. Encentrum essexis sp. n. is characterised by the in dorsal view more or less conical toes having three elongate drop-shaped, light-refracting bodies leading to the tip of the toe. Trophi of Isoencentrum-type; outline of rami hexagonal; intramallei extended towards trophi axis into long spiniform process; inner margin of basal rami chambers with short tooth

Algivory in food webs of three temperate Andean rivers

Food web analyses have been fundamental in understanding community organization and ecosystem functioning. To date, a number of studies demonstrate that stream food webs depend to a large extent on allochthonous detritus, but there are more recent studies that show a high degree of autochthony. Our food-web study was carried out in three Andean rivers (Coilaco, Guampoe and Trancura) within the catchment area of Toltén River in southern Chile. Based on the analyses of 4251 invertebrate gut contents, we found that these Andean stream food webs are dominated by herbivores (range: 50-73% of all species) supported by a species-rich algal (basal) component, and characterized by a low proportion of omnivores (range: 8-27% of all species) and predatory species (range: 10-24%). Significant differences in the number of feeding links of the herbivores Meridialis diguillina and Antarctoperla michaelseni and the omnivore Smicridea chilensis were found between seasons. The spring herbivore Aubertoperla sp. showed significant differences between rivers. S.chilensis fed on 50 different prey items as compared with the herbivores whose maximum number of links ranged between 37 and 40. Web sizes ranged between 93 and 131 species and the proportion of top species was distinctly lower than those of basal (up to 0.651 in Coilaco River) and intermediate species. Direct connectance (links per species2) values were low and similar among rivers (range: 0.051-0.074), whereas mean food chain length ranged between 2.23 and 2.90. The distributions of web property values from the Andean rivers differed from those previously published. In contrast to previous predictions, mean food chain length in these Andean streams displayed a scale-invariant pattern across different web sizes, but it was significantly related to the proportion of intermediate species. © 2011 The Authors. Journal compilation © 2011 Ecological Society of Australia

Trophic positioning of meiofauna revealed by stable isotopes and food-web analyses

Despite important advances in the ecology of river food-webs, the strength and nature of the connection between the meio- and macrofaunal components of the web are still debated. Some unresolved issues are the effects of the inclusion of meiofaunal links and their temporal variations on the overall river food web properties, and the significance of autochtonous and allochtonous material for these components. In the present study we conducted gut content of macro- and meiofauna, and stable isotope analyses of meiofauna to examine seasonal food webs of a chalk stream. The results of the gut content analyses, confirmed by the δ13C signatures, revealed a seasonal shift from a dependence on autochthonous (biofilm) to allochthonous food sources. Here, we demonstrate that aggregating basal or meiofaunal species into single categories affects key web properties such as web size, links, linkage density, and predator-prey ratios. More importantly, seasonal variation in attributes characterized the entire web and these changes persist regardless of taxonomic resolution. Furthermore, our analyses evidenced discrete variations in δ15N across the meiofauna community with a trophic structure that confirms gut content analyses, placing the meiofauna high in the food web. We, therefore, conclude that small body-sized taxa can occur high in dynamic river food webs, questioning assumptions that trophic position increases with body size and that webs are static

Seasonal water level fluctuations: Implications for reservoir limnology and management

With the purpose of finding out whether seasonal water level fluctuations could affect water quality in a reservoir subjected to those changes, trends in environmental variables and in phytoplankton and zooplankton assemblages were analysed. The reservoir’s hydrological cycle was characterized by three regimes. The maximum level phase lasted from January to the beginning of June, the emptying phase existed between mid-June to the beginning of September and the minimum level phase lasted from mid-September to the beginning of the first autumn/winter rain events. The highest values of total phosphorus, soluble reactive phosphorus, nitrate, water colour and chlorophyll a were found during the minimum level phase. The phytoplankton assemblage was dominated by taxa typical of meso-eutrophic environments during the emptying and minimum level phases. However, during the maximum level phase, taxa generally found in more oligotrophic systems were observed here also. Similar to other disturbed systems, the zooplankton assemblage was dominated by Rotifera, except in summer and autumn when the cladoceran Ceriodaphnia quadrangula and/or the copepod Tropocyclops prasinus became dominant. Although those shifts seem to be related to water level variations, further research is needed to evaluate to what extent they might also be induced by other seasonal factors acting independently of water fluctuations. Based upon the obtained data, suggestions for reservoir management are proposed

The influence of submarine groundwater discharges on subtidal meiofauna assemblages in south Portugal (Algarve)

Submarine groundwater discharges (SGD) have been documented as contributing to the biological productivity of coastal areas, through a bottom-up support to higher trophic levels. Nevertheless, the effects on the bottom levels of the coastal food web, namely the meiofauna, are still very poorly known. The “Olhos de Água” beach is the only area on the South coast of Portugal where submarine freshwater seepages have been identified. In this study, meiofauna assemblages in the area impacted by SGD were compared with the meiofauna from a similar area, but without SGD. Samples were taken in Spring and Summer 2011, under different hydrological regimes, aquifer recharge (after Winter) and dryness (after Spring), respectively. The major changes in the community were recorded at a seasonal level, with higher abundances and number of taxa in Spring, when compared to Summer. This may be explained by better sediment aeration during spring along with higher food availability from the sedimentation of spring phytoplankton blooms. Although no significant differences were detected by multivariate analysis on the meiofauna abundances between Control and Impact areas, pair-wise tests on the interactions between factors in number of taxa (S) and species richness (Margalef's d) suggested that the discharge of groundwater stimulated an increase in meiofauna diversity. Such effect can be observed between the meiofauna assemblages from impacted and control areas and also between periods with different discharge regimes (Spring and Summer) in the impacted area. These findings highlight the role that freshwater discharges from coastal aquifers have on meiofauna assemblages and suggest that SGD contribute to enhance the transfer of energy from the lower levels of the trophic web to upper levels

A First Search for coincident Gravitational Waves and High Energy Neutrinos using LIGO, Virgo and ANTARES data from 2007

We present the results of the first search for gravitational wave bursts associated with high energy neutrinos. Together, these messengers could reveal new, hidden sources that are not observed by conventional photon astronomy, particularly at high energy. Our search uses neutrinos detected by the underwater neutrino telescope ANTARES in its 5 line configuration during the period January - September 2007, which coincided with the fifth and first science runs of LIGO and Virgo, respectively. The LIGO-Virgo data were analysed for candidate gravitational-wave signals coincident in time and direction with the neutrino events. No significant coincident events were observed. We place limits on the density of joint high energy neutrino - gravitational wave emission events in the local universe, and compare them with densities of merger and core-collapse events.Comment: 19 pages, 8 figures, science summary page at http://www.ligo.org/science/Publication-S5LV_ANTARES/index.php. Public access area to figures, tables at https://dcc.ligo.org/cgi-bin/DocDB/ShowDocument?docid=p120000

Exotic crayfish in a brown water stream: effects on juvenile trout, invertebrates and algae

1. The impact of the introduced omnivorous signal crayfish (Pacifastacus leniusculus ) on trout fry, macroinvertebrates and algae was evaluated in a brown water stream in southern Sweden using in situ enclosures. We also examined the gut content of all surviving crayfish in the enclosures. Two crayfish densities in addition to a control without crayfish were used in replicate enclosures (1.26 m(2)) in a 1-month experiment. Additionally, 20 trout fry (Salmo trutta ) were stocked in each enclosure to assess the effects of crayfish on trout survival and growth. 2. Detritus was the most common food item in crayfish guts. Animal fragments were also frequent while algae and macrophytes were scarcer. Crayfish exuviae were found in crayfish guts, but the frequency of cannibalism was low. 3. Trout survival in enclosures was positively related to water velocity but was unaffected by crayfish. 4. Total invertebrate biomass and taxon richness were lower in crayfish treatments. The biomass of all predatory invertebrate taxa was reduced but only three of six non-predatory taxa were reduced in the crayfish treatments. 5. Epiphytic algal biomass (measured as chlorophyll a , on plastic strips) was not related to crayfish density, whereas the biomass of epilithic algae (measured as chlorophyll a ) was enhanced by high water velocity and high crayfish density. The latter was possibly mediated via improved light and nutrient conditions, as active crayfish re-suspend and/or remove detritus and senescent algal cells during periods of low water velocity. 6. We conclude that the introduced signal crayfish may affect stream communities directly and indirectly. Invaded communities will have reduced macroinvertebrate taxon richness and the signal crayfish will replace vulnerable invertebrate predators such as leeches. In streams that transport large amounts of sediment or organic matter, a high density of crayfish is likely to enhance benthic algal production through physical activity rather than via trophic effects

A Replicated Network Approach to 'Big Data' in Ecology

International audienceGlobal environmental change is a pressing issue as evidenced by the rise of extreme weather conditions in many parts of the world, threatening the survival of vulnerable species and habitats. Effective monitoring of climatic and anthropogenic impacts is therefore critical to safeguarding ecosystems, and it would allow us to better understand their response to stressors and predict long-term impacts. Ecological networks provide a biomonitoring framework for examining the system-level response and functioning of an ecosystem, but have been, until recently, constrained by limited empirical data due to the laborious nature of their construction. Hence, most experimental designs have been confined to a single network or a small number of replicate networks, resulting in statistical uncertainty, low resolution, limited spatiotemporal scale and oversimplified assumptions. Advances in data sampling and curation methodologies, such as next-generation sequencing (NGS) and the Internet 'Cloud', have facilitated the emergence of the 'Big Data' phenomenon in Ecology, enabling the construction of ecological networks to be carried out effectively and efficiently. This provides to ecologists an excellent opportunity to expand the way they study ecological networks. In particular, highly replicated networks are now within our grasp if new NGS technologies are combined with machine learning to develop network building methods. A replicated network approach will allow temporal and spatial variations embedded in the data to be taken into consideration, overcoming the limitations in the current 'single network' approach. We are still at the embryonic stage in exploring replicated networks, and with these new opportunities we also face new challenges. In this chapter, we discuss some of these challenges and highlight potential approaches that will help us build and analyse replicated networks to better understand how complex ecosystems operate, and the services and functioning they provide, paving the way for deciphering ecological big data reliably in the future