Correction: Niche partitioning and phylogenetic distance of rotifer species revealed by the four-year temporal dynamics in a small mountain lake

Niche partitioning and phylogenetic distance of rotifer species revealed by the four-year temporal dynamics in a small mountain lake

Sediment traps were deployed for periods of 4−5 weeks between May 1990 and September 1991 at depths of 6.5 and 12.5 m in a 15 m deep, rural U.K. lake. Trap material was quantitatively analyzed for 14 PAH compounds, 43 PCB congeners, particle mass, and C and N contents. Derived depositional fluxes of total PAHs (11.7 mg m-2 yr-1) and total PCBs (289 and 463 μg m-2 yr-1 at 6.5 and 12.5 m, respectively) are at the upper ends of the ranges reported in other comparable studies. The annual fluxes of individual PAH compounds are generally similar to accumula tion rates determined for surface sediments at the same location, indicating the absence of significant recycling. The ratios of annual depositional fluxes to surface sediment accumulation rates are substantially greater than 1 in the case of phenanthrene (2.5) and PCBs (6.5−23). These relatively elevated fluxes combined with a consideration of particle dynamics in the lake suggest significant recycling between the sediments and water column, involving remob...

More diverse plant communities are generally more productive than monocultures. This benefit of species diversity is supposed to stem from resource partitioning of species in mixtures where different species use the resources spatially, temporally, or chemically in distinct ways. With respect to water, the simultaneous cultivation of crops with distinct water uptake patterns might reduce niche overlaps and thus result in higher productivity. However, little is known about whether and how spatial water uptake patterns of crop species differ among different planting arrangements and whether these changes result in increased niche partitioning and explain overyielding in mixtures. Stable isotopes of water and a Bayesian model were used to investigate the spatial water uptake patterns of six different crop species and how these patterns change depending on the planting arrangement (monocultures vs mixtures). Niche overlaps and niche widths in spatial water uptake were compared among the different crop diversity levels and linked to productivity. Furthermore, spatial water uptake was related to competition intensity and overyielding in mixtures. We found evidence for increased niche partitioning in spatial water uptake, and therefore complementary spatial root distributions of crop species, and higher expected productivity in mixtures compared to expected productivity in monocultures both due to inherent species‐level differences in water uptake and plasticity in the water uptake pattern of species. We also found a significant relationship of competition and overyielding with observed patterns in spatial water uptake. These results suggest that competition was most intense in shallow soil layers and enhanced overyielding was related to a gradual increase of water uptake in deeper soil layers. Thus, overyielding might be related to a more complete spatial exploitation of available water sources. Synthesis. Differences in spatial water uptake and niche partitioning of intercropped species, driven most likely by a complementary spatial root distribution, might explain why mixtures outperform monocultures. These findings underpin the potential of intercropping systems for a more sustainable agriculture with a more efficient use of soil resources and hence reduced input demands.

Stable isotopes offer an opportunity to investigate lake dynamics in the absence of whole catchment studies. This study considered multi-year δ18O values for six different lakes located in the Italian Alps. We studied δ18O values of two large (L. Caldonazzo and L. Levico) and four small lakes (L. Lavarone, L. Santo di Cembra, L. Serraia, and L. Tovel) characterised by different hydrological regimes (> or <1 year renewal time) and size (> or <50 ha). Differences in isotope composition along the water column, between years and layers were used to investigate the extend of lake water renewal, mixis, stratification, and groundwater infiltration. Lakes with short renewal time had significantly different spring overturn values, while lakes with longer renewal time had substantially constant values. The isotope content of the water column also clarified the extent of mixis for some lakes: Lavarone underwent complete mixing only in some years, while Tovel, previously considered meromictic, could no longer be considered as such. With the exception of L. Tovel, characterised by a peculiar hydrology, thermal stratification was reflected in yearly isotope patterns. Analysis of hypolimnetic isotope values indicated that in L. Lavarone and L. Serraia strong storm events altered summer hypolimnetic δ18O values suggesting groundwater infiltration. Furthermore, epilimnetic isotope enrichment was related to lake elevation by a linear relationship. The extraordinarily hot 2003 summer led to a higher evaporation with respect to other years considered. Multi-annual data on the isotopic values of rainfall for L. Tovel (1178 m a.s.l.) provided the necessary background for data interpretation since precipitation governs isotope inputs. Based on our data, we proposed a general scheme of the seasonal δ18O pattern in temperate lakes distinguishing between small and large lakes.

Resource partitioning is an essential mechanism enabling species coexistence. The resources that are used by an animal are linked to its morphology and ecology. Therefore, similar species should use similar resources. The ecological niche of an individual summarizes all used resources and is therefore composed of several dimensions. Many methods are established to study different dimensions of an animal's niche. The aim of this study was to demonstrate that a combination of suitable methods is needed to study spatial and dietary resource partitioning of sympatric species in detail. We hypothesized that, while each individual method might identify differences between species, the combined results of several methods will lead to a more complete picture of spatial and dietary resource partitioning. As model organisms we chose the sympatric insectivorous bat species Myotis bechsteinii , M. nattereri , and P. auritus . We examined horizontal habitat use by telemetry, vertical habitat use by measuring δ 13 C, trophic position by measuring δ 15 N in wing membrane, and diet composition by molecular fecal analysis. Our results show that each method is able to provide information about spatial/dietary resource partitioning. However, considering further dimensions by combining several methods allows a more comprehensive assessment of dietary and spatial resource partitioning in bats.

Mixing Dynamics in Lakes Across Climatic Zones

Preface. Diatoms, lake acidification and the Surface Water Acidification Programme (SWAP): a review R.W. Battarbee. Lipid storage in Diaptomus kenayi (Copepoda Calanoida): Effects of inter and intraspecific variation in food quality N.M. Butler. Nitrogen in Pyrenean lakes (Spain) J. Catalan, L. Camarero, E. Garcia, E. Ballesteros, M. Felip. Plankton dynamics in a high mountain lake (Las Yeguas, Sierra Nevada, Spain) L. Cruz-Pizarro, I. Reche, P. Carillo. Acidification of lakes in Sumava (Bohemia) and in the High Tatra Mountains (Slovakia) J. Fott, M. Prazakova, E. Stuchlik, Z. Stuchlikova. Chemical characteristics of lakes in the High Tatra Mountains J. Kopacek, E. Stuchlik. Paleolimnological records of carotenoids and carbonaceous particles in sediments of some lakes in the Southern Alps A. Lami, A. Marchetto, P. Gullizzoni, A. Giorgis, J. Massaferro. Algal flora of lakes in the High Tatra Mountains, Slovakia J. Lukavsky. Acidification and weathering processes in high mountain lakes in the Southern Alps A. Marchetto, A. Barbieri, R. Mosello, G.A. Tartari. Reconstruction of pH by chrysophycean scales in some lakes of the Southern Alps A. Marchetto, A. Lami. A survey of water chemistry and plankton in high mountain lakes in Northern Swedish Lapland A. Nauwerck. Cyclops scutifers Sars in Lake Latnjajaure, Swedish Lapland A. Nauwerck. Comparison of diatom communities in remote high mountain lakes using index B and cluster analysis P. Niederhauser, F. Schanz. Zooplankton decline in the Cerne Lake (Sumava Mountains, Bohemia) as reflected in the stratification of cladoceran remains in the sediment M. Prazakova, J. Fott. Characterization of carbonaceous particles from lake sediments N.Rose. Autotrophic picoplankton community dynamics in a pre-alpine lake, British Columbia, Canada J.G. Stockner, K.S. Shortreed. Chemical properties of an acidified humic headwater lake H. Thies. Limnological research on northern Apennine lakes (Italy) in relation to eutrophication and acidification risk P. Viaroli, I. Ferrari, G. Paris, G. Rossetti, P. Menozzi. The effect of anthropogenic acidification on the hydrofauna on the lakes in the West Tatra Mountains M. Varnovsky, I. Krno, F. Sporka, J. Tomajka. Chlorophyll--phosphorus relationship in acidified lakes of the High Tatra Mountains (Slovakia) V. Vyhnalek, J. Fott, J. Kopacek. Acidification of small mountain lakes in the High Tatra Mountains, Poland K. Wojtan, J. Galas.

SWOT performance in monitoring water level of high-mountain lakes on the Tibetan Plateau

It is often hypothesized that two species competing for the same resource cannot stably coexist unless they partition their resources in space and time. More recently stable isotope analyses have complemented traditional, observation-based niche research by conceptualizing many of the characteristics of communities, for example, trophic niche width and the partitioning of resources. Here we quantify resource partitioning of sympatric small mammal species in an African ecosystem by analysing stable isotope ratios of hair collected from a South African forest-grassland vegetation mosaic, and combine this with known spatial and temporal behavioural data to interpret community competition and resource partitioning. We observe niche separation to different degrees across the entire community, with different species displaying either unique isotopic dietary preferences, or partitioning resources in space and/or time. δ13C values were more enriched in species that inhabited afromontane grassland compared with those that inhabited afromontane forest, a reflection of the dominant vegetation in each habitat. Contrary to expectations, arboreal rodents occupied higher trophic positions than terrestrial rodents and approaching δ15N values similar to insectivorous shrews, suggesting that arboreal rodents feed on items such as arthropods enriched in 15N. While grassland species display phenotypic plasticity in terms of dietary preferences, small mammals that occurred in forests display narrow niche preferences, suggesting these species may be particularly sensitive to habitat modifications. Our results illustrate that the use of stable isotopes can be used in conjunction with spatial and temporal behavioural knowledge to elucidate resource partitioning in small African mammal communities.

Deposit-feeding mechanisms and resource partitioning in tropical holothurians

The trait‐based partitioning of species plays a critical role in biodiversity–ecosystem function relationships. This niche partitioning drives and depends on community structure, yet this link remains elusive in the context of a metacommunity, where local community assembly is dictated by regional dispersal alongside local environmental conditions. Hence, elucidating the coupling of niche partitioning and community structure needs spatially explicit studies. Such studies are particularly necessary in river networks, where local habitats are highly connected by unidirectional water flow in a spatially complex network structure and frequent disturbance makes community structure strongly dependent on recolonization. Here, we show that taxonomic turnover among periphyton communities colonizing deployed bricks (microhabitats) at multiple sampling sites (local habitats) in a river network came along with a turnover in traits. This niche partitioning showed a hump‐shaped relationship with richness of periphyton communities, which increased along river size. Our observations suggest downstream dispersal along the river network to increase the regional metacommunity pool, which then ensures local colonization by taxa possessing diverse traits allowing them to efficiently partition into environmentally different microhabitats. However, at the most downstream sites, the excessive dispersal of widespread generalists drove mass effects which inflated richness with taxa that co‐occupied several microhabitats and swamped niche partitioning. Further, efficient niche partitioning depended on communities rich in rare taxa, an indication for the importance of specialists. Alarmingly, richness and rare taxa declined with high phosphorus concentrations and conductivity, respectively, two environmental variables which potentially reflected anthropogenic activity.

Asexual organisms are ubiquitous. While being members of a single species with the same ecological requirements, multiple asexual genotypes within a species are often found in a single habitat. Niche partitioning in time and space among genotypes has been proposed to explain this phenomenon. However, it is not clear whether these different genotypes co‐occur in the long term. Therefore, we examined the population dynamics of two asexual Daphnia cf. pulex genotypes (JPN1 and JPN2) over 9 years in a small mountain lake. These two genotypes consistently occurred in the same seasons and layers, suggesting that niche partitioning cannot explain their long‐term co‐occurrence. The abundance of JPN1 was typically higher in most years. However, the abundance of dormant eggs in lake sediments was at the same level between the genotypes. Results of a laboratory experiment showed that JPN1 competitively excluded JPN2. However, many JPN2 individuals produced dormant eggs before JPN1 competitively excluded them from the experiment. Furthermore, the competitively inferior JPN2 produced dormant eggs abundantly in the medium containing a crowding cue from JPN1 while no such trend was observed for JPN1. These results showed that a competitively inferior asexual genotype could maintain a population with a competitively superior genotype for a long period of time because it had the ability to detect an increase in competitors and produce dormant eggs each year before being competitively eliminated. Based on these results, we suggest that the variation in genotype‐specific response in dormant egg production to environmental change plays a key role in the long‐term co‐occurrence of different asexual genotypes in single habitats. Read the free Plain Language Summary for this article on the Journal blog.

Methane (CH4) emissions from aquatic systems have recently been comprised to account for up to 50% of global CH4 emissions, with lakes representing one of the largest CH4 sources within this pool. However, there is large uncertainty associated with CH4 emissions from freshwater environments to the atmosphere, because of a lack of understanding in the spatial and temporal dynamics of CH4 sources and sinks, as well as underlying mechanisms and processes. In this study, we investigated the concentrations and stable carbon (δ13C-CH4) and hydrogen (δ2H-CH4) isotope composition of CH4 in a small eutrophic lake (Lake Willersinnweiher) with seasonal stratification and its spatial and temporal variation. We found that while supersaturation of CH4 in the entire water column was present throughout the whole year, the isotopic composition of CH4 in sediment and water column varied depending on lake stratification, physiochemical conditions, and lake depth. During the stratification period, isotopic characteristics of pelagic surface water CH4 differed from littoral and sedimentary CH4, suggesting likely mixing of CH4 from different sources including vertical and lateral input as well as groundwater input and potentially oxic methane production in the mixed surface water layer. Aerobic CH4 oxidation indicated by a strong increase in both δ13C-CH4 and δ2H-CH4 values at the bottom of the oxycline was found to significantly reduce upward migrating CH4 released at the sediment-water interface. In the sediment, stable isotope characteristics of CH4 showed an increasing dominance of the acetoclastic CH4 formation pathway from the pelagic towards the littoral area. Furthermore, the occurrence of sulfate-dependent anaerobic methane oxidation in the sediment was suggested by an increase in δ13C-CH4 and δ2H-CH4 values. During the mixing period, the isotopic CH4 composition of the water column was distinctively less negative than during the stratification period potentially resulting from a greater impact of groundwater CH4 input compared to the stratification period. Our findings implicate that the application of concentrations and dual isotope measurements of CH4 is a promising approach for constraining CH4 sinks and sources in Lake Willersinnweiher and potentially other small lakes to clearly disentangle the complex CH4 dynamics in lakes both spatially and seasonally.

Niche concept is a core tenet of ecology that has recently been applied in marine microbial research to describe the partitioning of taxa based either on adaptations to specific conditions across environments or on adaptations to specialised substrates. In this study, we combine spatiotemporal dynamics and predicted substrate utilisation to describe species-level niche partitioning within the NS5 Marine Group. Despite NS5 representing one of the most abundant marine flavobacterial clades from across the world’s oceans, our knowledge on their phylogenetic diversity and ecological functions is limited. Using novel and database-derived 16S rRNA gene and ribosomal protein sequences, we delineate the NS5 into 35 distinct species-level clusters, contained within four novel candidate genera. One candidate species, “Arcticimaribacter forsetii AHE01FL”, includes a novel cultured isolate, for which we provide a complete genome sequence—the first of an NS5—along with morphological insights using transmission electron microscopy. Assessing species’ spatial distribution dynamics across the Tara Oceans dataset, we identify depth as a key influencing factor, with 32 species preferring surface waters, as well as distinct patterns in relation to temperature, oxygen and salinity. Each species harbours a unique substrate-degradation potential along with predicted substrates conserved at the genus-level, e.g. alginate in NS5_F. Successional dynamics were observed for three species in a time-series dataset, likely driven by specialised substrate adaptations. We propose that the ecological niche partitioning of NS5 species is mainly based on specific abiotic factors, which define the niche space, and substrate availability that drive the species-specific temporal dynamics.

Fate of organochlorine contaminants in arctic and subarctic lakes estimated by mass balance modelling