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Chautauqua Lake, New York, is a two-basin lake with a deeper, cooler, and less nutrient-rich Northern Basin, and a warmer, shallower, nutrient-replete Southern Basin. The lake is populated by a complex mixture of cyanobacteria, with toxigenic strains that produce microcystins, anatoxins, and paralytic shellfish poisoning toxins (PSTs). Samples collected from 24 sites were analyzed for these three toxin classes over four years spanning 2014–2017. Concentrations of the three toxin groups varied widely both within and between years. During the study, the mean and median concentrations of microcystins, anatoxin-a, and PSTs were 91 and 4.0 μg/L, 0.62 and 0.33 μg/L, and 32 and 16 μg/L, respectively. Dihydro-anatoxin was only detected once in Chautauqua Lake, while homo-anatoxin was never detected. The Northern Basin had larger basin-wide higher biomass blooms with higher concentrations of toxins relative to the more eutrophied Southern Basin, however blooms in the North Basin were infrequent. Chlorophyll concentrations and toxins in the two basins were correlated with different sets of environmental and physical parameters, suggesting that implementing controls to reduce toxin loads may require applications focused on more than reductions in cyanobacterial bloom density (e.g., reduction of phosphorus inputs), and that lake limnological factors and morphology are important determinants in the selection of an appropriate management strategy. Chautauqua Lake is a drinking water source and is also heavily used for recreation. Drinking water from Chautauqua Lake is unlikely to be a significant source of exposure to cyanotoxins due to the location of the intakes in the deeper North Basin, where there were generally low concentrations of toxins in open water; however, toxin levels in many blooms exceeded the US Environmental Protection Agency’s recreational guidelines for exposure to cyanotoxins. Current cyanotoxin monitoring in Chautauqua Lake is focused on microcystins. However, the occurrence of blooms containing neurotoxic cyanotoxins in the absence of the microcystins indicates this restricted monitoring may not be sufficient when aiming to protect against exposure to cyanotoxins. The lake has a large number of tourist visitors; thus, special care should be taken to prevent recreational exposure within this group.

Stable isotope analysis has become a crucial tool for aquatic food web ecologists, but a lack of methodological standardization hinders comparisons between studies. One methodological inconsistency in stable isotope food web research is the decision whether to extract lipids before stable isotope analysis. The depletion in zooplankton stable carbon isotope values (δ13C) due to fatty acid content and the accuracy of mathematical correction models designed to predict this depletion were examined for a range of zooplankton species from nine lakes of diverse size and productivity. Large differences of up to $5\\textperthousand$ observed between δ13C values of nonextracted and lipid-extracted zooplankton samples correlated with zooplankton fatty acid content. A mass balance δ13C correction model for fatty acid content using atomic C:N ratios and directly measured δ13C values of fatty acids accurately predicted (R2 = 0.95) lipid-extracted δ13C values for both copepod and cladoceran zooplankton. Researchers should use mass balance lipid corrections as an efficient method to eliminate bias in comparisons of zooplankton and fish δ13C values and allow their results to be more easily compared with other studies.

Biological and environmental contrasts between aquatic and terrestrial systems have hindered analyses of community and ecosystem structure across Earth's diverse habitats. Ecological stoichiometry 1 , 2 provides an integrative approach for such analyses, as all organisms are composed of the same major elements (C, N, P) whose balance affects production, nutrient cycling, and food-web dynamics 3 , 4 . Here we show both similarities and differences in the C:N:P ratios of primary producers (autotrophs) and invertebrate primary consumers (herbivores) across habitats. Terrestrial food webs are built on an extremely nutrient-poor autotroph base with C:P and C:N ratios higher than in lake particulate matter, although the N:P ratios are nearly identical. Terrestrial herbivores (insects) and their freshwater counterparts (zooplankton) are nutrient-rich and indistinguishable in C:N:P stoichiometry. In both lakes and terrestrial systems, herbivores should have low growth efficiencies (10–30%) when consuming autotrophs with typical carbon-to-nutrient ratios. These stoichiometric constraints on herbivore growth appear to be qualitatively similar and widespread in both environments.

Early detection of aquatic invasive species, such as Nitellopsis obtusa, is often critical to reduce their long-term negative effects. This macroalga resembles native taxa and can invade deep locations in littoral zones of lakes in North America. Studies in which effects of Nitellopsis on macrophyte communities were quantified are rare. We surveyed 4 lakes in central New York where Nitellopsis is present to document whether macrophyte communities are negatively affected by this invasive macroalgae and to test whether Nitellopsis was found more frequently in deeper- than in shallow-water habitats. We found lower macrophyte species richness when Nitellopsis was abundant. This pattern was consistent at 3 water depths (shallow [>1 m], intermediate [1–2 m], and deep [>2 m]). Macrophyte biomasses (total, including native and other nonnative species, and only native species) were significantly lower in quadrats with greater abundance of Nitellopsis. Nitellopsis biomass exceeded the combined biomass of macrophytes in some lakes. Nitellopsis was present more frequently in deeper than in shallow water in 2 of the study lakes. Our results suggest that Nitellopsis can have negative effects on macrophyte communities and indicate that this taxon can become dominant in littoral zones of invaded lakes. It is more likely to be present in deeper water, which may prevent casual observation, so personnel responsible for monitoring programs should establish protocols and methods tailored to detect this spreading, cryptic invasive species.

Theory suggests that in a new habitat, initial levels of genetic or species diversity can influence subsequent community assembly. Nevertheless, empirical investigations of these diversity effects in newly created habitats remain rare at both the genetic and species level, especially for animal systems. To test this theory, we conducted a field experiment in which initial stocking diversity (both intra‐ and interspecific) of freshwater zooplankton in newly constructed pools was manipulated in a 2 × 2 fully factorial design. Zooplankton communities were sampled every 2 weeks from May to August in 2011 and 2012, and once in May of 2013 and 2014. Estimates of overland dispersal were measured in 2012. Despite theoretical predictions, we found no difference in taxonomic richness among stocking treatments after 4 yr. A total of 24 species was recorded in the experimental pool metacommunity, with average cumulative taxonomic richness ranging from 6.1 to 7.6 species per pool. Using dispersal traps, we found that dispersal of zooplankton was rapid, with eight taxa dispersing within 7 d; we found no difference in the number of dispersed propagules based on number of neighboring source pools. Despite theoretical predictions regarding diversity and community assembly, our study suggests that initial diversity may have no effect on early successional community species richness.

Presence and abundance of invasive species depend on likelihood of introduction and environmental limitations to their distributions. Propagule pressure and anthropogenic disturbance are hypothesized to increase invasions, yet assessing the importance of propagule pressure and anthropogenic factors independently is challenging, and properties of invaded systems (e.g., habitat availability) likely contribute to invasions. We sampled macrophyte assemblages in 20 lakes in New York, varying in boater visitations and number of previous waterbodies visited, to test if increased propagule risk (proxy for propagule pressure measuring potential for introducing invasives from different sources) resulted in greater species richness, biomass (g/m2) and dominance (% invasive biomass) of invasive macrophytes. We then tested watershed land use, in-lake water properties, and lake morphology on presence, abundance, and dominance of invasive macrophytes. Increased propagule risk resulted in greater species richness of invasive macrophytes. In invaded lakes, increased abundance of invasive macrophytes was correlated with increased agriculture in watersheds and littoral:total area. Increased dominance of invasive macrophytes was observed in lakes with greater littoral:total areas. Results suggest propagule risk can explain spatial variability in macrophyte invasions, while area-specific biomass in invaded lakes can be correlated with watershed and in-lake water properties. In lakes with increased suitable habitat (relative proportion of littoral:total area ratio), invasive macrophytes may dominate aquatic plant assemblages. Many factors correlated with the abundance of invasive macrophytes are not easily managed (e.g., watershed agricultural land use and lake morphology). Limiting introductions of propagules is likely the best approach to prevent macrophyte invasions, especially at high risk lakes.

Nutritional and contaminant stressors influence organismal physiology, trophic interactions, community structure, and ecosystem-level processes; however, the interactions between toxicity and elemental imbalance in food resources have been examined in only a few ecotoxicity studies. Integrating well-developed ecological theories that cross all levels of biological organization can enhance our understanding of ecotoxicology. In the present article, we underline the opportunity to couple concepts and approaches used in the theory of ecological stoichiometry (ES) to ask ecotoxicological questions and introduce stoichiometric ecotoxicology, a subfield in ecology that examines how contaminant stress, nutrient supply, and elemental constraints interact throughout all levels of biological organization. This conceptual framework unifying ecotoxicology with ES offers potential for both empirical and theoretical studies to deepen our mechanistic understanding of the adverse outcomes of chemicals across ecological scales and improve the predictive powers of ecotoxicology.

Despite advances in metapopulation theory, recent studies have emphasized the difficulty in understanding and accurately predicting dynamics in nature. We address this knowledge gap by coupling 4 years of population data for the freshwater zooplankter Daphnia pulex, inhabiting 38 newly established ponds in Upstate New York, with (i) a spatially explicit stochastic model and (ii) a deterministic model where we have averaged the spatial dependencies. By modifying the identity of ponds stocked/removed in our model, we examine the effects of network structure on metapopulation dynamics and local occupancy patterns. From these modeling exercises, we show that the centrality of ponds (stocked or removed) has contrasting effects on metapopulation persistence when selecting ponds to initially stock versus preserve. The pond network was not robust to the removal of centrally located ponds as the simulated removal of these ponds resulted in rapid collapse of the metapopulation. However, when initially founding a metapopulation, the location of patches did not influence occupancy dynamics. Because stochastic simulations can be computationally expensive, we also introduce a quantity for use in a simple differential equation model that encompasses all spatial information in a single variable. Using this quantity, we show how the output of our simple differential equation model matched the quasi-steady state of the stochastic simulations in networks characterized by high connectivity. The method we use is general enough to be applied in other systems and can provide insights for habitat conservation and restoration efforts including how network structure can drive spatiotemporal metapopulation dynamics.

Mercury (Hg) deposited onto the landscape can be transformed into methylmercury (MeHg), a neurotoxin that bioaccumulates up the aquatic food chain. Here, we report on Hg concentrations in snapping turtles ( Chelydra serpentina ) across New York State, USA. The objectives of this study were to: (1) test which landscape, water, and biometric characteristics correlate with total Hg (THg) concentrations in snapping turtles; and (2) determine whether soft tissue THg concentrations correlate with scute (shell) concentrations. Forty-eight turtles were sampled non-lethally from ten lakes and wetlands across New York to observe patterns under a range of ecosystem variables and water chemistry conditions. THg concentrations ranged from 0.041 to 1.50 μg/g and 0.47 to 7.43 μg/g wet weight of muscle tissue and shell, respectively. The vast majority of mercury (~94%) was in the MeHg form. Sixty-one percent of turtle muscle samples exceeded U.S. Environmental Protection Agency (U.S. EPA) consumption advisory limit of 0.3 μg Hg/g for fish. Muscle THg concentrations were significantly correlated with sulfate in water and the maximum elevation of the watershed. Shell THg concentrations were significantly correlated with the acid neutralizing capacity (ANC) of water, the maximum elevation of the watershed, the percent open water in the watershed, the lake to watershed size, and various forms of atmospheric Hg deposition. Thus, our results demonstrate that THg concentrations in snapping turtles are spatially variable, frequently exceed advisory limits, and are significantly correlated with several landscape and water characteristics.

Evidence suggests that marine and freshwater zooplankton generally experience food levels above subsistence values in terms of carbon. However, the quality of this food may be poor due to an insufficiency of other essential nutrients. In this review, we examine recent progress in three main areas of food quality research: (1) elemental (especially P) limitation, (2) digestion resistance, and (3) biochemical (especially fatty acids) limitation. We evaluate laboratory and field evidence in each of these areas, look at new evidence about the life history implications of the elemental limitation hypothesis, and suggest future avenues for research. From a rather large number of seemingly heterogeneous studies, a single consistent picture of food quality emerges: both P and essential fatty acids are predicted to be important dietary factors, but at different places and times. Nevertheless, despite an abundance of valuable laboratory studies, our knowledge of food quality limitation in the field is still poor.[PUBLICATION ABSTRACT]