Parkinson's disease (PD) is a movement neurodegenerative disorder, characterized by bradykinesia, rigidity and tremor, constituting difficulties in walking and abnormal gait. Previous research shows that Drosophila expressing human α-synuclein A30P (A30P) develop deficits in geotaxis climbing; however, geotaxis climbing is a different movement modality from walking. Whether A30P flies would exhibit abnormal walking in a horizontal plane, a measure more relevant to PD, is not known. In this study, we characterized A30P fly walking using a high-speed camera and an automatic behavior tracking system. We found that old but not young A30P flies exhibited walking abnormalities, specifically decreased total moving distance, distance per movement, velocity, angular velocity and others, compared with old control flies. Those features match the definition of bradykinesia. Multivariate analysis further suggested a synergistic effect of aging and A30P, resulting in a distinct pattern of walking deficits, as seen in aged A30P flies. Psychiatric problems are common in PD patients with anxiety affecting 40–69% of patients. Central avoidance is one assessment of anxiety in various animal models. We found old but not young A30P flies exhibited increased centrophobism, suggesting possible elevated anxiety. Here, we report the first quantitative measures of walking qualities in a PD fly model and propose an alternative behavior paradigm for evaluating motor functions apart from climbing assay.

A complex interplay of environmental variables impacts phytoplankton community composition and physiology. Temperature and nutrient availability are two principal factors driving phytoplankton growth and composition, but are often investigated independently and on individual species in the laboratory. To assess the individual and interactive effects of temperature and nutrient concentration on phytoplankton community composition and physiology, we altered both the thermal and nutrient conditions of a cold-adapted spring phytoplankton community in Narragansett Bay, Rhode Island, when surface temperature was 2.6 C and chlorophyll > 9 μg L À1 . Water was incubated in triplicate at À0.5 C, 2.6 C, and 6 C for 10 d. At each temperature, treatments included both nutrient amendments (N, P, Si addition) and controls (no macronutrients added). The interactive effects of temperature and resource availability altered phytoplankton growth and community structure. Nutrient amendments resulted in species sorting and communities dominated by larger species. Under replete nutrients, warming tripled phytoplankton growth rates, but under in situ nutrient conditions, increased temperature acted antagonistically, reducing growth rates by as much as 33%, suggesting communities became nutrient limited. The temperature-nutrient interplay shifted the relative proportions of each species within the phytoplankton community, resulting in more silica rich cells at decreasing temperatures, irrespective of nutrients, and C : N that varied based on resource availability, with nutrient limitation inducing a 47% increase in C : N at increasing temperatures. Our results illustrate how the temperature-nutrient interplay can alter phytoplankton community dynamics, with changes in temperature amplifying or exacerbating the nutrient effect with implications for higher trophic levels and carbon flux.

Lake Baikal, Siberia, is the most biodiverse freshwater lake on Earth. However, despite decades of painstaking limnological research on Baikal, broad spatial data on nutrient (nitrogen (N), phosphorus (P), silica (Si)) concentrations and temperature are sparse, as is our understanding of the bottom‐up factors that limit phytoplankton in the lake. Earlier studies have suggested both N and P as limiting nutrients in Baikal, but the evidence, mostly based on elemental ratios, is limited and somewhat conflicting. We present experimental evidence that N and P co‐limit phytoplankton productivity in some areas of Baikal during summer, along with the results of a comprehensive spatial survey of surface temperature, nutrients and chlorophyll a (Chl a) in Lake Baikal that support the experimental finding of colimitation. Surface water incubations from two trophically contrasting locations revealed co‐limitation by N and P, as well as a positive effect of temperature (fluorescence after 5 d was ∼10% higher at 15°C than at 10°C). In a linear model of the survey data (26 sampling locations), N, P, and their interaction (N × P) were all significant predictors of Chl a concentration, indicating that either N or P (or both) may limit summer phytoplankton, depending on location. In contrast to the incubation experiments, temperature was not a significant predictor of Chl a concentration across the 26 sites we sampled. Lake Baikal is undergoing rapid warming and increased nutrient loading, which may boost phytoplankton productivity in the lake; however, the magnitude of this response will depend on ratios of soluble N and P inputs.

Parkinson’s disease (PD) is the most common motor neurodegenerative disorder. Olfactory dysfunction is a prevalent feature of PD. It often precedes motor symptoms by several years and is used in assisting PD diagnosis. However, the cellular and molecular bases of olfactory dysfunction in PD are not known. The fruit fly Drosophila melanogaster, expressing human alpha-synuclein protein or its mutant, A30P, captures several hallmarks of PD and has been successfully used to model PD in numerous studies. First, we report olfactory deficits in fly expressing A30P (A30P), showing deficits in two out of three olfactory modalities, tested – olfactory acuity and odor discrimination. The remaining third modality is odor identification/naming. Second, oxidative stress is an important environmental risk factor of PD. We show that oxidative stress exacerbated the two affected olfactory modalities in younger A30P flies. Third, different olfactory receptor neurons are activated differentially by different odors in flies. In a separate experiment, we show that the odor discrimination deficit in A30P flies is general and not restricted to a specific class of chemical structure. Lastly, by restricting A30P expression to dopamine, serotonin or olfactory receptor neurons, we show that A30P expression in dopamine neurons is necessary for development of both acuity and discrimination deficits, while serotonin and olfactory receptor neurons appeared not involved. Our data demonstrate olfactory deficits in a synuclein fly PD model for exploring olfactory pathology and physiology, and for monitoring PD progression and treatment.

Despite increasing interest in winter limnology, few studies have examined under-ice zooplankton communities and the factors shaping them in different types of temperate lakes. To better understand drivers of zooplankton community structure in winter and summer, we sampled 13 lakes across a large trophic status gradient for crustacean zooplankton abundance, taxonomic and functional community composition and C/N stable isotopes. Average winter zooplankton densities were one-third of summer densities across the study lakes. Proportionally, cladocerans were more abundant in summer than winter, with the opposite pattern for calanoids and cyclopoids. In green (eutrophic) lakes, zooplankton densities were higher under the ice than in brown (dystrophic) and blue (oligotrophic) lakes, suggesting better conditions for zooplankton in productive lakes during winter. Overall, zooplankton communities were more similar across lakes under the ice than during the open water season. Feeding group classification showed a decrease in herbivore abundance and an increase in predators from summer to winter. C/N stable isotope results suggested higher lipid content in overwintering zooplankton and potentially increased reliance on the microbial loop by winter zooplankton. Our results show substantial variation in the seasonality of zooplankton communities in different lake types and identify some of the factors responsible for this variation.

words) 13Understanding how microbial communities respond to environmental change requires 14 knowledge of the main drivers of their community structure, diversity and potential resilience. 15For many rapidly changing ecosystems this information is still not available. Lake Baikal in 16Siberia is the most ancient, deep, voluminous, and biologically diverse lake in the world, with 20 17 percent of global unfrozen fresh water, that is undergoing rapid warming. Little is known about 18 its bacterioplankton communities and their drivers. In the first extensive survey of Baikal's 19 microbial communities, we show that temperature, stratification, nutrients, and dissolved 20 oxygen, and not the geographic distance, define major microbial habitats and microbial 21 community similarity. Communities in ML and DW exhibited contrasting patterns of richness, 22 diversity and evenness and comprised different cohesive modules in the whole Baikal OTU co-23 occurrence network. The network exhibited small-world properties that may make it resistant to 24 perturbations but sensitive to changes in the abundances of central, most connected OTUs. 25Functional redundancy, often associated with higher resilience, was low in cold, open water 26 communities and increased with temperature in the mixed layer and with depth in the deep-water 27 samples. Our results suggest that bacterial communities of open waters in Lake Baikal may be 28 45 of microbial diversity and function in various aquatic habitats. However, the environmental 52 drivers of microbial community diversity, community structure, function, and stability remain 53 poorly characterized in many aquatic ecosystems, including the world's most ancient (25 My) 54 lake Baikal -a UNESCO heritage site and known hotspot for endemism of its biota. Baikal is the 55 world's deepest (1643 m) and most voluminous lake, holding about 20% of world's surface 56 unfrozen freshwater (3). Of the approximately 2600 plant and animal species in the lake, two-57 thirds are endemic, including the dominant primary producers, grazers, benthic and pelagic fish 58 and the top predator -world's only freshwater seal (3, 4). 59Hampton et al. (4) showed that water temperatures have risen by 1.2 °C over 60 years of 60 high-resolution time series, contributing to an increase in numbers and kinds of non-endemic 61 zooplankton and algal species, with potential consequences for nutrient cycling, food web 62 structure (3) and microbial communities. Moreover, the Lake Baikal region is predicted to warm 63 by 3-4°C in the next century (5), with ongoing changes likely to continue and even accelerate. 64Because the biota of Lake Baikal, including microbial communities, is adapted to cold 65 temperatures, it may be especially vulnerable to warming. Additionally, other changing 66 environmental factors may also alter the lake's microbial communities. 67The vulnerability of communities to environmental change depends in part on their 68 functional redundancy (FR), linked to the number of species that perform a similar func...

Lake Baikal (Siberia, Russia) is the oldest, the deepest and the most voluminous lake on Earth. During the last century, Baikal has experienced gradual increases in temperature but remains highly oligotrophic with increases in primary productivity limited to the warmest parts of the lake. Using whole body RNA:DNA ratio as an indicator of metabolic rate, we demonstrate that the key primary consumer in Baikal's plankton, Epischura baikalensis (Copepoda: Calanoida), is a capital breeder that relies on lipid storage to maintain productivity. In individuals from nature, the RNA:DNA ratio correlated with lipid content in samples from cold, low phytoplankton density locations from Baikal's North and Central basins, but not in samples from warmer South basin and Maloe More strait. Lipid reserves, both visually assessed and measured by Nile Red fluorescence, correlated positively with phytoplankton density. In laboratory experiments the RNA:DNA ratio responded to starvation and temperature in non-reproducing, low lipid storage females, but not in individuals with developed ovaries or high lipid storage. This indicates that, unlike many other zooplankton crustaceans, E. baikalensis uses resource storage to support current reproduction, which buffers the dependency of metabolic rate on current feeding conditions. We discuss possible effects of such buffering on E. baikalensis competition with non-endemic, largely income-feeding zooplankton species whose frequency is currently increasing in Baikal pelagia.

Marine microbial communities in coastal environments are subject to both seasonal fluctuations and anthropogenic alterations of environmental conditions. The separate influences of temperature and resource‐dependency on phytoplankton growth, community, and ecosystem metabolism are relatively well understood. However, winners and losers in the ocean are determined based on the interplay among often rapidly changing biological, chemical and physical drivers. The direct, indirect, and interactive effects of these conditions on planktonic food web structure and function are poorly constrained. Here, we investigated how simultaneous manipulation of temperature and nutrient availability affects trophic transfer from phytoplankton to herbivorous protists, and their resulting implications at the ecosystem level. Temperature directly affected herbivorous protist composition; ciliates dominated (66%) in colder treatment and dinoflagellates (60%) at warmer temperatures. Throughout the experiments, grazing rates were < 0.1 d−1, with higher rates at subzero temperatures. Overall, the nutrient–temperature interplay affected trophic transfer rates antagonistically when nutrients were amended, and synergistically, when nutrients were not added. This interaction resulted in higher percentages of primary production consumed under nutrient unamended compared to nutrient amended conditions. At the ecosystem level, these changes may determine the fate of primary production, with most of the production likely exported out of the pelagic zone in high‐temperature and nutrient conditions, while high‐temperature and low‐nutrient availability strengthened food web coupling and enhanced trophic transfer. These results imply that in warming oceans, management of coastal nutrient loading will be a critical determinant of the degree of primary production removal by microzooplankton and dependent ecosystem production.