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Anticipating how biodiversity will respond to climate change is challenged by the fact that climate variables affect individuals in competition with others, but interest lies at the scale of species and landscapes. By omitting the...
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Anticipating how biodiversity will respond to climate change is challenged by the fact that climate variables affect individuals in competition with others, but interest lies at the scale of species and landscapes. By omitting the individual scale, models cannot accommodate the processes that determine future biodiversity. We demonstrate how individual-scale inference can be applied to the problem of anticipating vulnerability of species to climate. The approach places climate vulnerability in the context of competition for light and soil moisture. Sensitivities to climate and competition interactions aggregated from the individual tree scale provide estimates of which species are vulnerable to which variables in different habitats. Vulnerability is explored in terms of specific demographic responses (growth, fecundity and survival) and in terms of the synthetic response (the combination of demographic rates), termed climate tracking. These indices quantify risks for individuals in the context of their competitive environments. However, by aggregating in specific ways (over individuals, years, and other input variables), we provide ways to summarize and rank species in terms of their risks from climate change.
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We recently found that genes involved in mitochondrial dynamics and autophagy are required for removal of UVCinducedmitochondrial DNA damage. However, drp-1 and pink-1, unlike the autophagy and fusion genes tested, were notnecessa...
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We recently found that genes involved in mitochondrial dynamics and autophagy are required for removal of UVCinducedmitochondrial DNA damage. However, drp-1 and pink-1, unlike the autophagy and fusion genes tested, were notnecessary for larval development after exposure. We hypothesized that increased fusion resulting from mutations in thesegenes facilitated recovery of mitochondrial function. In this work, we investigated this hypothesis by studying the effectsof fis-1, fis-2, drp-1 and pink-1 mutations on mitochondrial responses to UVC exposure including ATP levels, mitochondrialDNA copy number, larval development and mitochondrial morphology. Our results suggest that mutations that promotehighly networked mitochondria have the capacity to lessen the effects of mitochondrial genotoxicants on the functionof this organelle.
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We examined the effects of N fertilization on forest soil fungal and bacterial biomass at three long-term experiments in New England (Harvard Forest, MA; Mt. Ascutney, VT; Bear Brook, ME). At Harvard Forest, chronic N fertilizatio...
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We examined the effects of N fertilization on forest soil fungal and bacterial biomass at three long-term experiments in New England (Harvard Forest, MA; Mt. Ascutney, VT; Bear Brook, ME). At Harvard Forest, chronic N fertilization has decreased organic soil microbial biomass C (MBC) by an average of 54% and substrate induced respiration (SIR) was decreased by an average of 45% in hardwood stands. In the pine stand, organic soil MBC was decreased by 40% and SIR decreased by an average of 35%. The fun
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The recent global increase in forest mortality episodes could not have been predicted from current vegetation models that are calibrated to regional climate data. Physiological studies show that mortality results from interactions...
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The recent global increase in forest mortality episodes could not have been predicted from current vegetation models that are calibrated to regional climate data. Physiological studies show that mortality results from interactions between climate and competition at the individual scale. Models of forest response to climate do not include interactions because they are hard to estimate and require long-term observations on individual trees obtained at frequent (annual) intervals. Interactions involve multiple tree responses that can only be quantified if these responses are estimated as a joint distribution. A new approach provides estimates of climate-competition interactions in two critical ways, (i) among individuals, as a joint distribution of responses to combinations of inputs, such as resources and climate, and (ii) within individuals, due to allocation requirements that control outputs, such as demographic rates. Application to 20 years of data from climate and competition gradients shows that interactions control forest responses, and their omission from models leads to inaccurate predictions. Species most vulnerable to increasing aridity are not those that show the largest growth response to precipitation, but rather depend on interactions with the local resource environment. This first assessment of regional species vulnerability that is based on the scale at which climate operates, individual trees competing for carbon and water, supports predictions of potential savannification in the southeastern US.
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DNA damage is an important mechanism of toxicity for a variety of pollutants, and therefore, is often used asan indicator of pollutant effects in ecotoxicological studies. Here, we adapted a PCR-based assay for nuclearand mitochon...
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DNA damage is an important mechanism of toxicity for a variety of pollutants, and therefore, is often used asan indicator of pollutant effects in ecotoxicological studies. Here, we adapted a PCR-based assay for nuclearand mitochondrial DNA damage for use in an important environmental model, the Atlantic killifish (Fundulusheteroclitus). We refer to this assay as the long amplicon quantitative PCR (LA-QPCR) assay. To validate thismethod in killifish, DNA damage was measured in liver, brain, and muscle of fish dosed with 10 mg/kg benzo[alpyrene. This exposure caused 0.4-0.8 lesions/10 kb. We also measured DNA damage in liver and muscletissues from killifish inhabiting a Superfund site, confirming the utility of this method for biomonitoring. Inboth cases, damage levels were comparable in nuclear DNA (nDNA) and mitochondrial DNA (mtDNA). Sinceextensive nDNA sequence data are not readily available for many environmentally relevant species, butmitochondrial genomes are frequently fully sequenced, this assay can be adapted to examine mtDNA damagein virtually any species with little development. Therefore, we argue that this assay will be a valuable tool inassessing DNA damage in ecotoxicological studies.
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Low survival rates of juveniles in populations of the endangered Hawaiian monk seal (Monachus schauinslandi) in the Northwestern Hawaiian Islands are believed to be the leading cause of the species' decline. One hypothesis is that...
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Low survival rates of juveniles in populations of the endangered Hawaiian monk seal (Monachus schauinslandi) in the Northwestern Hawaiian Islands are believed to be the leading cause of the species' decline. One hypothesis is that younger seals are starving due to poor foraging success. Because high mortality of young seals poses a significant risk to population-level survival, increased knowledge of the specifics of weaned pup and juvenile foraging is of paramount importance. We used telemetry dataand the most recent movement modeling techniques to compare monk seals' home ranges across various age and sex groups among five of the six primary breeding colonies in the Hawaiian Islands. We found significant differences in size and spatial patterns of home ranges at the regional and colony level, following a decreasing productivity gradient from the northwest to the southeast. Home range size was significantly smaller in the three northwestern colonies than the two central-northeastern colonies. Adult seals in one colony at the lower end of the productivity gradient had smaller home ranges than younger seals, perhaps indicating that lower levels of prey abundance are forcing younger seals to forage further away from the colony where larger adult seals outcompete them. Uniqueness in seal movement on Pearl & Hermes Reef might be associated with increased southerly latitudinal movement of the Transition Zone Chlorophyll Front, which brings nutrient rich waters and a potential surge in productivity, supporting the theory that better prey availability reduces home range size. The wide variability in home range sizes and locations suggests that a universal approach to managing monk seals on different colonies would be unsuccessful. Results here suggestthat animals from different colonies may perceive habitat differently; these differences should be taken into account when translocating animals to new habitat.
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Vengosh et al. (2022) presented integrated geochemical data that includedmajor and trace elements coupled with strontiumisotope variations in groundwater that were used to elucidate the source of salinization of groundwater and Ei...
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Vengosh et al. (2022) presented integrated geochemical data that includedmajor and trace elements coupled with strontiumisotope variations in groundwater that were used to elucidate the source of salinization of groundwater and Ein Bokek spring in the northeastern Negev in Israel. The study included analyses of phosphate rocks and wastewater from the phosphate mine and fertilizer production operations in Mishor Rotem Industries. The study revealed that the phosphatemining generates wastewater with distinctive geochemical and strontiumisotope compositions. Since the geochemical and Sr isotope compositions of the salinized groundwater were different from those of the phosphate wastewater but similar to a different wastewater source, Vengosh et al. (2022) excluded the phosphate mining effluent as themajor contamination source. These results contradict previous studies (e.g., Burg and Guttman, 2019) that claimed that phosphate mining was the major source of contamination without characterizing the geochemical composition of wastewaters from the phosphate rock mining. We are thankful to Burg et al. (2023) for raising important issues related to the salinization of groundwater in the northeastern Negev in Israel and for highlighting the novelty of using strontium isotopes for elucidating the source of groundwater contamination in the context of phosphate mining and fertilizer production.
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Regime shifts in shallow lakes are often associated with anthropogenic impacts, such as land-use change, non-point source nutrient loading, and overfishing. These shifts have mostly been examined in lakes in temperate and boreal r...
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Regime shifts in shallow lakes are often associated with anthropogenic impacts, such as land-use change, non-point source nutrient loading, and overfishing. These shifts have mostly been examined in lakes in temperate and boreal regions and within anthropogenically disturbed basins. Here, it is demonstrated that tropical floodplain lakes in a region of virtually no human disturbance naturally undergo frequent regime shifts. We demonstrate this using satellite imagery to provide a 23-year time seriesof 22-oxbow lakes or “cochas” along 300 km of the Manu River in SE Perú. In any year, a majority of these lakes is in a macrophyte-free, phytoplankton-dominated state. However, over the 23 years covered by images, roughly a third of the lakes experienced abrupt shifts to a floating macrophyte state. Macrophyte cover persisted for ≤ 3 year. Analysis of water level fluctuations sampled on a subset of the lakes for 1 year suggests that lake isolation from streams and the main river facilitates regime shifts. Multiple forcing factors, both internal and external to the lakes themselves, could drive the observed regime shifts, but insufficient data exist from this remote region to identify the key processes.
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In-stream nutrient concentrations are well known to exhibit a strong relationship with river flow. The use of flow measurements to predict nutrient concentrations and subsequently nutrient loads is common in water quality modeling...
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In-stream nutrient concentrations are well known to exhibit a strong relationship with river flow. The use of flow measurements to predict nutrient concentrations and subsequently nutrient loads is common in water quality modeling. Nevertheless, most adopted models assume that the relationship between flow and concentration is fixed across time as well as across different flow regimes. In this study, we developed a Bayesian change-point-threshold model that relaxes these constraints and allows for the identification and quantification of any changes in the underlying flow-concentration relationship across time. The results from our study support the occurrence of a changepoint in time around the year 1999, which coincided with the period of implementing nitrogen control measures as part of the TMDL program developed for the Neuse Estuary in North Carolina. The occurrence of the changepoint challenges the underlying assumption of temporal invari-ance in the flow-concentrations relationship. The model results also point towards a transition in the river nitrogen delivery system from a point source dominated loading system towards a more complicated nonlinear system, where non-point source nutrient delivery plays a major role. Moreover, we use the developed model to assess the effectiveness of the nitrogen reduction measures in achieving a 30% drop in loading. The results indicate that while there is a strong evidence of a load reduction, there still remains a high level of uncertainty associated with the mean nitrogen load reduction. We show that the level of uncertainty around the estimated load reduction is not random but is flow related.
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We develop a Bayesian network (BN) model that describes estuarine chlorophyll dynamics in the upper section of the Neuse River Estuary in North Carolina, using automated constraint based structure learning algorithms. We examine t...
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We develop a Bayesian network (BN) model that describes estuarine chlorophyll dynamics in the upper section of the Neuse River Estuary in North Carolina, using automated constraint based structure learning algorithms. We examine the functionality and usefulness of the structure learning algorithms in building model topology with real-time data under different scenarios. Generated BN models are evaluated and a final model is selected. Model results indicate that although the effect of water temperature and river flow on chlorophyll dynamics has remained unchanged following the implementation of the nitrogen Total Maximum Daily Load (TMDL) program; the response of chlorophyll levels to nutrient concentrations has been altered. The results stress the importance of incorporating expert defined constraints and links in conjunction with the automated structure learning algorithms to generate more plausible structures and minimize the sensitivity of the learning algorithms. This hybrid approach towards structure learning allows for the incorporation of existing knowledge while limiting the scope of the learning algorithms to defining the links between environmental variables for which the expert has little or no information.
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