Lake Plankton Research Articles

A Biogeographical Debate at the Origins of Limnology in Switzerland and Italy: The Issue over Pelagic Fauna Between Pietro Pavesi and François-Alphonse Forel.

This article explores the early biogeographical debates that shaped the beginning of limnology, focusing on the differences of opinion concerning the origins of pelagic fauna between two pioneering scientists: Pietro Pavesi and François-Alphonse Forel. The study examines how Pavesi's hypothesis of a marine origin for pelagic fauna contrasts with Forel's theory of passive distribution, situating their arguments within a broader Darwinian framework. The first part of the paper provides a historical overview of Italian limnology, highlighting Pavesi's contributions and interpreting Forel's writings to underscore the significance of discovering pelagic fauna in conceptualizing lakes as microcosms. The second part compares Pavesi's and Forel's hypotheses, emphasizing their impact on the scientific understanding of freshwater ecosystems. The importance of this discovery, in both historical and scientific contexts, lies in recognizing the presence of plankton in lakes as a crucial element for the mature formulation of ecological concepts, such as the ecosystem.

Under ice plankton and lipid dynamics in a subarctic lake.

Climate warming causes shorter winters and changes in ice and snow cover in subarctic lakes, highlighting the need to better understand under-ice ecosystem functioning. The plankton community in a subarctic, oligotrophic lake was studied throughout the ice-covered season, focusing on lipid dynamics and life history traits in two actively overwintering copepods, Cyclops scutifer and Eudiaptomus graciloides. Whereas C. scutifer was overwintering in C-IV to C-V stage, E. graciloides reproduced under ice cover. Both species had accumulated lipids prior to ice-on and showed a substantial decrease in total lipid content throughout the ice-covered period: E. graciloides (60%-38% dw) and C. scutifer (73%-33% dw). Polyunsaturated fatty acids of algal origin were highest in E. graciloides and declined strongly in both species. Stearidonic acid (18:4n-3) content in E. graciloides was particularly high and decreased rapidly during the study period by 50%, probably due to reproduction. The copepods differed in feeding behavior, with the omnivore C. scutifer continuing to accumulate lipids until January, whereas the herbivorous E. graciloides accumulated lipids from under-ice primary production during the last months of ice-cover. Our findings emphasize the importance of lipid accumulation and utilization for actively overwintering copepods irrespective of the timing of their reproduction.

PHYTOPLANKTON IN THE LAKES OF THE REPUBLIC OF BASHKORTOSTAN

The phytoplankton in a number of lakes in the Bashkir Trans-Urals (Atavdy, Sultankul (2017), Bursunsy, Kuldybay (2019), Bolshiye Uchaly, Uzunkul (2021)) and Bashkir Pre-Urals (Bolshoy Tolpak, 2022)) was studied. As a result of the study, the taxonomic structure, quantitative characteristics, dominant species, distribution features of main algal groups were reveald, and their ecological and geographical characteristics werre identified. 257 species and intraspecific taxa of algae from 9 divisions were registered in the algal flora. Green algae (33%), cyanoprokaryotes and diatoms (21% each of total species number) show the highest species diversity in the lakes. The algal flora is specific for each lake and has low degree of floristic similarity (0.13–0.57 according to Sørensen coefficients). In the ecological and geographical terms, the algal floras of lake plankton is represented by typical planktonic species, widespread in waterbodies of the globe, indifferent to water salinity, living only in fresh waterbodies and preferring neutral waters. Quantitative indicators of phytoplankton varied in a wide range of values: number of cells from 4.4 to 344 mln cells/L, biomass from 0.23 to 22.97 mg/L. Dominant species in terms of abundance are represented predominantly by cyanoprokaryotes (Snowella lacustris, Aphanocapsa delicatissima, A. incerta, Aphanizomenon flos-aquae, Gloeotrichia echinulata, Merismopedia tenuissima, Pseudanabaena galeata, Planktolyngbya limnetica, Woronichinia compacta, Anathece clathrata, Rhabdoderma lineare), in terms of biomass by green (Oocystis lacustris, O. borgei, O. marssonii, Scenedesmus apiculatus), dinophyte (Peridinium cinctum, Gymnodinium sp., Ceratium furcoides), desmidium algae (Staurodesmus cuspidatus, Cosmarium contractum, C. cucumis) and cyanoprokaryotes (Pseudanabaena galeata, Aphanizomenon flos-aquae, Gloeotrichia echinulata). According to the value of the saprobity index (Pantle – Bucc by number 1.57–2.80), the lake waters correspond to β- and α-mesosaprobic types of waterbodies with III and IV water quality classes (moderately polluted or dirty water).

Short Communication: The biodiversity of aquatic organisms in Anak Laut Lake, Aceh Singkil District, Indonesia

Abstract. Muhtadi A, Leidonald R, Yolanda O, Harahap R, Matondang NP, Putri K, Simamora LFM, Sitompul G. 2023. Short Communication: The biodiversity of aquatic organisms in Anak Laut Lake, Aceh Singkil District, Indonesia. Biodiversitas 24: 4837-4844. Anak Laut Lake is a unique and strategic coastal lake, significantly recognized for its diverse marine biota and the potential to be a spawning, nursery, and feeding ground. Therefore, this research aimed to determine the types of aquatic organisms, including plankton, fish, crustaceans, benthos, seagrasses, and mangroves in Anak Laut Lake. The experiment was conducted in October 2022 in the Anak Laut Lake ecosystem, North Singkil Sub-district, Aceh Singkil District, Aceh Province, Indonesia. The plankton was taken using a plankton net tool, extracted vertically from a depth of 2 m, and pulled to the surface. Fish and crustaceans were observed and caught with purse seines, ring nets, and gill nets. Benthic organisms were directly observed on the edge of the lake, along with the identification of mangroves, while at the bottom, the fishermen dove into the water. The data obtained were analyzed descriptively and compared with similar research. The results showed a rich biodiversity in Anak Laut Lake, with at least 165 species/genera of aquatic biota, 9 species of mangroves, and 2 Seagrass species. The marine nekton found consisted of fish (55 species), shrimp (3 species), and crabs (10 species). The macrozoobenthos found in Anak Laut Lake consisted of 13 species of clams, 12 gastropods, 3 sea cucumbers, 2 sand dollars, 2 horseshoe crabs, and 1 sea urchin. Various species of aquatic biota whose existence was threatened in nature and found in this lake included golden sea cucumber (Stichopus herrmanni), seahorse (Hippocampus comes and Hippocampus kuda) with Vulnerable status (VU), tap ray (Maculabatis gerrardi), and sand cucumber (Holothuria scabra) with Endangered species status (EN). This shows that this coastal lake is an important and crucial habitat for several species that are vulnerable to extinction. For this reason, in the future, further studies are needed regarding the habitat characteristics and spatial and temporal distribution of aquatic organisms in Lake Laut, so that more appropriate management can be implemented for the sustainability of the lake.

Summer dynamics of cyanobacteria in an oligo-mesotrophic temperate lake in Northwest Ireland

Despite the potential adverse consequences they can impart on biotopes, cyanobacteria are an understudied component of lake plankton communities in Ireland. This study, in summer 2019, examined cyanobacterial diversity and associated environmental variables in a lake previously impacted by algal blooms, in north-west Ireland. Vertical profiling showed that photosynthetic pigment concentrations were spatially heterogenous for the majority of the survey. However, water column homogeneity was observed towards the end of the survey, coinciding with increases in pigment concentrations. Sunshine hours, nutrient concentrations and wind speed were stable throughout the survey. Spatial homogeneity in pigments was attributed to an increase in minimal temperatures observed in the water column. PCR-DGGE analysis identified patterns in community composition, indicating a rise in cyanobacterial richness concomitant to increase in temperature and photosynthetic pigments. Band sequencing analysis identified phylotypes similar to the toxigenic species Microcystis sp. These were prominent at the end of the survey and coincided with the presence of the mcyE gene and low levels of microcystins, as indicated by real time PCR and ELISA analyses. The summer background presence of toxigenic cyanobacteria with potential bloom-forming capacity highlights the importance of annual lake cyanotoxin monitoring to inform resource management to protect human and animal health.

SPECIES COMPOSITION OF PHYTOPLANKTON OF THE BLAGODATNOYE LAKE (ITURUP ISLAND, KURIL ISLANDS, RUSSIA)

Algological studies conducted in June–August 2021 on the lagoon Blagodatnoye Lake (Iturup Island) and showed a high diversity of species composition of cyanobacteria and algae (274 species and intraspecifi c taxa from eight divisions: Cyanobacteria, Miozoa, Bacillariophyta, Chlorophyta, Charophyta, Criptista, Ochrophyta, Euglenozoa). Diatoms make up a signifi cant share in the formation of algofl ora (73,2 % of the total number of species). Complexes of dominant species in lake plankton are represented by cyanobacteria and diatoms: Aulacoseira granulata and it’s variation A. granulata var. angustissima Aphanizomenon fl os-aquae (August). The maximum values of quantitative indicators of the main dominants reached: N = 1323,3 thousand cells/l, B = 685,5 mg/l for Asterionella formosa, and N = 3646 thousand cells/l, B = 4579,4 mg/l for Aulacoseira granulata. The ecological and geographical characteristics of the algal fl ora of Blagodatnoe Lake were carried out: benthic species (48,2 % of the total number of taxa), indiff erent to salinity change (68,6 %), alkaliphilic (42,3 %), cosmopolitan (70,1 %) species were predominance, and oligosaprobionts and betamesosaprobionts were 35,4 and 33,9 %, respectively.

The sedimentary filling differences of subsags and their impacts on oil shale and coal accumulation in a rift lacustrine sag: A case study from the Lower Cretaceous in the Zhangqiang sag, southern Songliao Basin, Northeast China

In order to characterize the sedimentary filling differences of two rift lacustrine subsags and their control factors and to construct the depositional model for coal and oil shale, the Lower Cretaceous Jiufotang and Shahai formations in the Qijiazi and Zhanggutai subsags, Zhangqiang sag, Songliao Basin, one of the most petroliferous basins in Northeast China have been analyzed. Seven facies were identified in the Lower Cretaceous strata of two subsags and were grouped into three facies associations, namely alluvial fan, fan delta and lacustrine. During the deposition of Jiufotang Formation, the Qijiazi subsag is mainly characterized by alluvial fan deposits, while the Zhanggutai subsag is dominated by fan delta and littoral-sublittoral lacustrine deposits. During the deposition of Shahai Formation, the Qijiazi subsag is characterized by fan delta, littoral-sublittoral lacustrine, and deep lacustrine deposits, whereas the Zhanggutai subsag is filled with fan delta and littoral-sublittoral lacustrine deposits. Coal and oil shale deposits are only preserved in the Shahai Formation of the Qijiazi subsag. Total organic carbon content, organic matter type, vitrinite reflectance, thermal alteration index and total reduced sulfur content also show that there are differences in organic matter preservation and redox conditions between two subsags. In the Jiufotang Formation, the total organic carbon contents are relatively low, the kerogen type is dominated by type III and the source rocks entered a mature phase in the Zhanggutai subsag, and the total reduced sulfur contents show a suboxic to oxidized environment in the Zhanggutai subsag and an oxidized environment in the Qijiazi subsag. In the Shahai Formation, the total organic carbon contents are relatively high, the kerogen type is dominated by type II and the source rocks entered an immature to mature phase in the Zhanggutai subsag, whereas the kerogen type is dominated by type III and the source rocks display an overall mature phase in the Qijiazi subsag. The total reduced sulfur contents of the Shahai Formation show the reduced environment in two subsags. Tectonics, sediment supply and redox conditions control the temporal and spatial differences in sedimentary filling and distribution of organic-rich rocks in two subsags. A comparison of rift lacustrine Qijiazi subsag and Fushun Basin shows that the rift basins are both characterized by deepening-upward to shallowing-upward successions controlled by tectonic subsidence and climate changes. The relatively high subsidence along with warmer climate resulted in the enhanced input of lake plankton and the decrease in higher plant input and triggered the transition from coal to oil shale formation.

The Size Structure of Unicellular Plankton (Size–Taxonomic and Size–Trophic Spectra) in a Hypertrophic Urban Lake

The Size Structure of Unicellular Plankton (Size–Taxonomic and Size–Trophic Spectra) in a Hypertrophic Urban Lake

Unicellular Plankton Size Structure (Size-Taxonomic and Size-Trophic Spectra) in a Hypertrophic Urban Lake

The results of an analysis of the size spectra of unicellular plankton (bacteria, algae, ciliates) in the hypertrophic freshwater urban lake (L. Bolshoe Vasilyevskoe, Togliatti, Russia) are presented. Two types of size spectra have been identified in the seasonal cycle. Strong nanoplanctonic maximum formed mainly by phototrophic cyanobacteria and Chlorophyta was found during the period of open water (spring to autumn); picoplankton maximum/maxima (mainly heterotrophic bacteria) and increased proportion of microplankton (heterotrophic and mixotrophic ciliates)–in the ice period. The peculiarity of the studied lake, in contrast to less productive ones is the stability of the plankton size structure over the past 25 years.

The feeding habits of small-bodied fishes mediate the strength of top-down effects on plankton and water quality in shallow subtropical lakes

The proliferation of small-bodied fishes in lakes is often accompanied by deterioration of water quality and ecosystem function. However, the potential impacts of different types of small-bodied fish species (e.g., obligate zooplanktivores and omnivores) on subtropical lake ecosystems in particular have been overlooked mainly due to their small size, shorter life spans and lower economic value. Therefore, we conducted a mesocosm experiment to elucidate how plankton communities and water quality respond to different types of small-bodied fishes, including a common zooplanktivorous fish (thin sharpbelly Toxabramis swinhonis) and other small-bodied omnivorous fishes (bitterling Acheilognathus macropterus, crucian carp Carassius auratus and sharpbelly Hemiculter leucisculus). During the experiment, the mean weekly total nitrogen (TN), total phosphorus (TP), chemical oxygen demand (CODMn), turbidity, chlorophyll-a (Chl.α) and trophic level index (TLI) values were generally higher in treatments where fish were present compared to treatments where fish were absent, but responses varied. At the end of the experiment, phytoplankton abundance and biomass and the relative abundance and biomass of cyanophyta were higher while the abundance and biomass of large-bodied zooplankton were lower in the fish-present treatments. Moreover, the mean weekly TP, CODMn, Chl.α and TLI values were generally higher in treatments with the obligate zooplanktivore, thin sharpbelly, when compared to treatments with omnivorous fishes. Also, the ratio of zooplankton to phytoplankton biomass was the lowest, and the ratio of Chl.α to TP was the highest in treatments with thin sharpbelly. Collectively, these general findings indicate that an overabundance of small-bodied fishes can have adverse effects on water quality and plankton communities and that small-bodied zooplanktivorous fishes likely induce stronger top-down effects on plankton and water quality than omnivorous fishes. Our results emphasise that small-bodied fishes should be monitored and controlled if overabundant when managing or restoring shallow subtropical lakes. From the perspective of environmental protection, the combined stocking of different piscivorous fish species that feed in different habitat types could be a way forward to control small-bodied fishes with different feeding habits, but more research is needed to assess the feasibility of this approach.

Photosynthetic activity of plankton in saline lakes under climatic fluctuations conditions

Climate change causes the alternation of high-water and low-water years, which is reflected in morphometric characteristics of lakes. Changes in the depth and volume of water bodies affect the structural and functional activity of the ecosystem, including the growth and development of primary producers. The photosynthetic activity of water body plankton was shown on the example of Dabasa-nor lake and Kudzhertai lake located in the steppe territory of the South-Eastern Transbaikalia. The studied lakes differ in their hydrochemical composition. The content of chlorophyllain Dabasa-nor lake is lower than in Kudzhertai lake. Degraded form of chlorophylla- pheophytin is present only in Dabasa-nor lake, which currently has the least depth of its filling. Carotenoids, as more stable forms of pigments, dominate in the pigment diversity of lake plankton. Chlorophyllcwas not detected in any of the plankton of both lakes. Factor analysis of the main components showed the interdependence of a number of abiotic agents with the pigment characteristic of phytoplankton. Thus, under the current conditions of the period of lake water availability recovery after a long dry period, the photosynthetic activity of the water body ecosystem is experiencing certain difficulties.

Effects of Lake Geo-Engineering on Plankton in a Typical Shallow Urban Lake: Evidence Based on 10-year Data

Effects of Lake Geo-Engineering on Plankton in a Typical Shallow Urban Lake: Evidence Based on 10-year Data

Formation and evolution mechanisms of coal and oil shale from the Middle Jurassic Shimengou Formation, northern Qaidam Basin, China

Thick coal and oil shale layers are present in the Middle Jurassic Shimengou Formation of northern Qaidam Basin (NQB). However, the formation and evolution mechanisms of these coals and oil shales remain unclear. In this study, these mechanisms were revealed through sedimentological and geochemical analyses of the coal- and oil shale-bearing interval from Shimengou Formation of NQB. The results show that the coals were formed in a swamp with flourishing conifer plants under a humid climate, which greatly enriched the organic matter (OM) supply during coal formation. The restricted swamp environment with suboxic and brackish water favored OM preservation during peat accumulation. With rapid subsidence, the swamp-shallow lake was evolved into deep and semi-deep lake sedimentary system, in which the oil shales were deposited. Lake expansion resulted in a more reducing water column and more lake plankton input during oil shales deposition. Disturbance of arid climate triggered lake salinization along with water column stratification and salt-tolerant algal blooms during the late deposition of Shimengou Formation. The algal blooms and anoxic bottom water greatly promoted the formation of oil shale with high OM richness, hydrocarbon potential and excellent kerogen types. Therefore, the lake expansion caused by rapid subsidence of basin triggered the transformation from coal to oil shale formation, while the climate aridity during oil shale deposition further promoted the quality of oil shale. This study not only reveals the formation and evolution mechanisms of coal and oil shales from Shimengou Formation in QNB, but also presents a typical sample for the prediction of coal and oil shales in the other similar Mesozoic-Cenozoic faulted basins in China.

Increasing diversity and biotic homogenization of lake plankton during recovery from acidification

Determining biodiversity responses to environmental change, such as acidification, is critical for ecosystem projections under future global change scenarios. Here, we analyzed three plankton communities of phytoplankton, crustaceans and rotifers in 28 lakes in the Adirondack Park, USA, during 1994–2012, and examined the spatiotemporal trends in their alpha and beta diversity during recovery from acidification. For all plankton assemblages, Shannon diversity increased towards recent years and high lake pH, and there was an increasing community dissimilarity with pH changes. The spatial mean Bray-Curtis dissimilarities across all lakes decreased over time for phytoplankton and rotifers leading to an increase in spatial homogenization. Such a homogenization cooccurred however with the overall increasing diversity in this region, which contrasts with the previous classic view that homogenization is mainly driven by loss of species and results in biodiversity loss. We further observed lower temporal mean beta diversity in low-pH lakes for crustaceans and rotifers, but not for phytoplankton. Generally, spatial and temporal mean beta diversity of the three taxonomic groups were primarily driven by lake-water ion variables, and rotifers were also constrained by nutrients and climate. Collectively, our results show how and why plankton community compositions vary over space along with acidification recovery, and further highlight the importance of spatiotemporal studies combined with long-term monitoring programs in assessing biodiversity change during the recovery of disturbed ecosystems.

How phytoplankton biomass controls metal(loid) bioaccumulation in size-fractionated plankton in anthropogenic-impacted subtropical lakes: A comprehensive study in the Yangtze River Delta, China

Phytoplankton biomass can significantly affect metal(loid) bioaccumulation in plankton, but the underlying mechanisms are still controversial. We investigated the bioaccumulation of eight metal(loid)s (As, Co, Cu, Hg, Mn, Pb, Se, and Zn) in three size categories of planktonic organisms – seston (0.7–64 μm), mesozooplankton (200–500 μm), and macrozooplankton (>500 μm) – sampled from six freshwater lakes in two seasons in the Yangtze River Delta, China. Our results highlight phytoplankton biomass is the major driver on metal(loid) bioaccumulation in the studied anthropogenic-impacted subtropical lakes, mainly via affecting site-specific water physiochemical characteristics and plankton communities. However, such impact is highly dependent on chlorophyll a (Chl-a) concentration. The bioaccumulation of metal(loid)s in size-fractionated plankton declined significantly with increasing phytoplankton biomass when Chl-a was below ∼50 μg L−1, mainly owing to the reduced metal(loid) bioavailability and subsequent bioaccumulation at more productive sites (with elevated pH and dissolved organic carbon), rather than algal bloom dilution. To a lesser extent, phytoplankton growth dilution and the smaller body-size of zooplankton at more productive sites also contributed to the lower metal(loid) bioaccumulation. The bioaccumulation of metal(loid)s was enhanced under severe algal bloom conditions (when Chl-a concentration was higher than ∼50 μg L−1). Although the underlying mechanisms still require further investigations, the potential risks of metal(loid) bioaccumulation under severe algal bloom conditions deserve special attention.

Multiscale effects of wind‐induced hydrodynamics on lake plankton distribution

AbstractIn this study, we used a combination of high‐intensity sampling technologies, and a 3D hydrodynamic model of a medium‐sized lake in southern Ontario, Canada to investigate physical–biological relationships at spatial scales from 100 m to 6 km and temporal scales from hours to months. At the scale of the whole study basin, we predicted that stronger winds would lead to higher zooplankton biomass downwind relative to upwind. The hydrodynamic model suggests rapid downwind displacement of progressively deeper surface mixed layers with increasing winds, and we found a statistically higher downwind biomass of small‐bodied zooplankton on windy days, but not large zooplankton. At a fine spatial scale (hundreds of meters), we predicted that zooplankton patchiness would decrease with increasing wind mixing of the upper water column and confirmed this for small‐bodied but not large‐bodied zooplankton. At this fine‐scale cross‐correlations of zooplankton biomass with water temperature and chlorophyll fluorescence suggested that zooplankton are not simply moved passively by water masses. We also found a clear change in the cross‐correlation between large‐ and small‐bodied zooplankton biomass, with out‐of‐phase spatial distributions during calm periods becoming in‐phase with increasing winds. Overall these results indicate that the response of zooplankton to wind‐driven physical forces is strongly dependent on an interaction between their body size, which determines their swimming speed and capacity to position themselves vertically in the water column, and the spatial scale and intensity of the wind‐generated physical forces. We discuss the implications for food web interactions.

Organic petrologic and geochemical characterization of petroleum source rocks in the Middle Jurassic Dameigou Formation, Qaidam Basin, northwestern China: Insights into paleo-depositional environment and organic matter accumulation

The organic matter-rich mudstones of the Middle Jurassic Dameigou Formation in the northern Qaidam Basin are regarded as the principal petroleum source rocks for unconventional resource exploration in China. In this study, a detailed investigation on the organic petrography, inorganic geochemistry as well as bulk and molecular organic geochemistry is presented. Three different source rock units were identified with TOC contents and VRr ranging from 1.5–39.2% and 0.35–0.57%, respectively. Carbonaceous mudstone and organic matter-rich mudstone in unit 1 with high Pr/Ph (4.79–7.25) and low Gam index (0.02–0.03) values mainly developed in an oxic freshwater column under warm and humid climatic conditions and strong weathering intensity. Organic matter in unit 1 with high proportions of C29 ααα 20R steranes (61–74%) is interpreted to be derived from terrestrial higher plants. By contrast, units 2 (Pr/Ph: 2.56–4.23; Gam index: 0.03–0.14) and 3 (Pr/Ph: 0.73; Gam index: 0.48) were deposited in sub-oxic to oxic freshwater and anoxic saline environments, respectively. Progressive aridification during the deposition of units 2 and 3 are reflected by decreasing CIA values (59.97–86.68) resulting in weakened weathering intensity and lower terrestrial influx. A mixture of terrestrial higher plants and algal biomass was the main source of organic matter in unit 2 with moderate C19/C23 Tri (0.96–5.44), C20/C23 Tri (1.28–3.87) and C24 Tet/C26 Tri (1.10–2.54) ratios, while unit 3 with the lowest C19/C23 Tri (0.25), C20/C23 Tri (0.95), and C24 Tet/C26 Tri (0.65) ratios and highest proportions of C27 ααα 20R steranes (69%) is characterized by a decrease in terrigenous organic matter content. The dominant source of organic matter is lake plankton, including halophilic algae and cyanobacteria. Organic matter accumulation in unit 1 is associated with a warm and humid climate, weathering intensity, and terrigenous organic matter input. Primary productivity is the most important factor controlling the enrichment of organic matter in units 2 and 3.

Road Salt versus Urban Snow Effects on Lake Microbial Communities

Freshwater salinization is an ongoing concern for north temperate lakes; however, little is known about its impacts on microbial communities, particularly for bacteria. We tested the hypotheses that road de-icing salt induces changes in the microbial community structure of lake plankton, and that changes due to chloride would differ from those due to urban snowmelt because of additional chemicals in the snowmelt. In a laboratory incubator experiment, an overwintering plankton community in lake water was exposed for two weeks to either NaCl or municipal road snow with the same level of chloride. Microbial community structure as determined by 16S (prokaryotes) and 18S (eukaryotes) rRNA transcript analysis showed changes in response to the chloride-only enrichment, with some rare taxa becoming more prominent. Consistent with our hypothesis, the salt and the snow treatments induced different community changes. These results indicate that ecotoxicology assays based on a single salt addition may not reflect the in situ effects of salt-contaminated urban snow, and that the combined chemical effects of urban snowmelt require direct testing.

Isotopic evidence for bioaccumulation of aerosol lead in fish and wildlife of western Canada

Lead (Pb) is a toxic element which is released as a result of anthropogenic activities, and Pb stable isotope ratios provide a means to distinguish sources and transport pathways in receiving environments. In this study, isotopes of bioaccumulated Pb (204Pb, 206Pb, 207Pb, 208Pb) were examined for diverse terrestrial and aquatic biota from three areas in western Canada: (a) otter, marten, gulls, terns, and wood frogs in the Alberta Oil Sands Region (AOSR), (b) fish, plankton, and gulls of Great Slave Lake (Yellowknife, Northwest Territories), and (c) wolverine from the Yukon. Aquatic and terrestrial biota from different habitats and a broad geographic area showed a remarkable similarity in their Pb isotope composition (grand mean ± 1 standard deviation: 206Pb/207Pb = 1.189 ± 0.007, 208Pb/207Pb = 2.435 ± 0.009, n = 116). Comparisons with Pb isotope ratios of local sources and environmental receptors showed that values in biota were most similar to those of atmospheric Pb, either measured in local aerosols influenced by industrial activities in the AOSR or in lichens (an aerosol proxy) near Yellowknife and in the Yukon. Biotic Pb isotope ratios were different from those of local geogenic Pb. Although the Pb isotope measurements could not unambiguously identify the specific anthropogenic sources of atmospheric Pb in biota, initial evidence points to the importance of fossil fuels currently used in transportation and power generation. Further research should characterize bioavailable chemical species of Pb in aerosols and important emission sources in western Canada.

Variation in the predictability of lake plankton metric types

AbstractStatistical and climate models are frequently used for biodiversity projections under future climatic changes, but their predictive capacity for freshwater plankton may vary among different species and community metrics. Here, we used random forests to model plankton species and community metrics as a function of biological, climatic, physical, and chemical data from long‐term (2000–2017) monitoring data collected from Lake Müggelsee Berlin, Germany. We (1) compared the predictability of well‐known lake plankton metric types (biomass, abundance, taxonomic diversity, Shannon diversity, Simpson diversity, evenness, taxonomic distinctness, and taxonomic richness) and (2) assessed how the relative influence of different environmental drivers varies across lake plankton metric models. Overall, the metric predictability was highest for biomass and abundance followed by taxonomic richness. The biomass of dominant phytoplankton taxonomic groups such as cyanobacteria (adjusted‐R2 = 0.53) and the abundance of dominant zooplankton taxonomic groups such as rotifers (adjusted‐R2 = 0.59) and daphnids (adjusted‐R2 = 0.51) were more predictable than other metric types. The plankton metric predictability increased when grouping phytoplankton species according to their functional traits (adjusted‐R2 = 0.37 ± 0.14, mean ± SD, n = 36 functional groups) compared to higher taxonomic units (adjusted‐R2 = 0.25 ± 0.15, n = 22 taxonomic groups). Light, nutrients, water temperature, and seasonality for phytoplankton and food resources for zooplankton were the main drivers of both taxonomic and functional groups, giving confidence that our models captured the expected major environmental drivers. Our quantitative analyses highlight the multidimensionality of lake planktonic responses to environmental drivers and have implications for our capacity to select appropriate metrics for forecasting the future of lake ecosystems under global change scenarios.