ALBERT

Description: Redd (nest) surveys for resident brook trout ( Salvelinus fontinalis ) were conducted annually in a mountain lake in northern New York for 11 years with multiple surveys conducted during the spawning season in eight of those years. Repeated surveys throughout the spawning season allowed us to fit an individually based parametric model and estimate the day of year on which spawning was initiated, reached its midpoint, and ended during each year. Spawning phenology was then assessed relative to (1) mean of maximum daily air temperature and (2) mean of maximum daily water temperature at the lake bottom during summer in each year using a linear model. Elevated temperatures in summer were correlated with a delay in spawning and a reduction in the total number of redds constructed. Increasing the summer mean of maximum daily air temperatures by 1 °C delayed spawning by approximately 1 week and decreased the total number of redds constructed by nearly 65. Lake spawning brook trout select redd sites based on the presence of discharging groundwater that is relatively constant in temperature within and across years, leading to relatively consistent egg incubation times. Therefore, delayed spawning is likely to delay fry emergence, which could influence emergence synchrony with prey items. This work highlights non-lethal and sub-lethal effects of elevated summer temperatures on native resident salmonids in aquatic environments with limited thermal refugia.

Description: Redd (nest) surveys for resident brook trout ( Salvelinus fontinalis ) were conducted annually in a mountain lake in northern New York for eleven years with multiple surveys conducted during the spawning season in eight of those years. Repeated surveys throughout the spawning season allowed us to fit an individually-based parametric model and estimate the day of year on which spawning was initiated, reached its midpoint, and ended during each year. Spawning phenology was then assessed relative to (1) mean of maximum daily air temperature and (2) mean of maximum daily water temperature at the lake bottom during summer in each year using a linear model. Elevated temperatures in summer were correlated with a delay in spawning and a reduction in the total number of redds constructed. Increasing the summer mean of maximum daily air temperatures by one degree C delayed spawning by approximately one week and decreased the total number of redds constructed by nearly 65. Lake spawning brook trout select redd sites based on the presence of discharging groundwater that is relatively constant in temperature within and across years, leading to relatively consistent egg incubation times. Therefore, delayed spawning is likely to delay fry emergence, which could influence emergence synchrony with prey items. This work highlights non-lethal and sub-lethal effects of elevated summer temperatures on native resident salmonids in aquatic environments with limited thermal refugia.

Description: Ceramide is a member of the sphingolipid family of bioactive molecules demonstrated to have profound, diverse biological activities. Ceramide is a potential chemotherapeutic agent via the induction of apoptosis. Exposure to ceramide activates extracellular-signal-regulated kinases (ERK)1/2- and p38 kinase-dependent apoptosis in human ovarian cancer OVCAR-3 cells, concomitant with an increase in the expression of COX-2 and p53 phosphorylation. Blockade of cyclooxygenase-2 (COX-2) activity by siRNA or NS398 correspondingly inhibited ceramide-induced p53 Ser-15 phosphorylation and apoptosis; thus COX-2 appears at the apex of the p38 kinase-mediated signaling cascade induced by ceramide. Induction of apoptosis by ceramide or resveratrol was inhibited by the endocytosis inhibitor, cytochalasin D (CytD); however, cells exposed to resveratrol showed greater sensitivity than ceramide-treated cells. Ceramide-treated cells underwent a dose-dependent reduction in trans-membrane potential. Although both ceramide and resveratrol induced the expressions of caspase-3 and -7, the effect of inducible COX-2 was different in caspase-7 expression induced by ceramide compared to resveratrol. In summary, resveratrol and ceramide converge on an endocytosis-requiring, ERK1/2-dependent signal transduction pathway and induction of COX-expression as an essential molecular antecedent for subsequent p53-dependent apoptosis. In addition, expressions of caspase-3 and -7 are observed. However, a p38 kinase-dependent signal transduction pathway and change in mitochondrial potential are also involved in ceramide-induced apoptosis. J. Cell. Biochem. © 2013 Wiley Periodicals, Inc.

Description: Determining the factors that limit abundance and biomass of fish is fundamental to effective fisheries management. In streams, pool availability, cover, and habitat complexity often limit fish—particularly salmonids—and many restoration efforts are directed toward addressing physical habitat factors. However, the availability of prey, and the factors that influence prey abundance, can also influence the abundance, biomass, and growth of fish and other consumers. Both habitat and prey availability can be influenced by characteristics of the riparian forest in headwaters. In this study, we evaluate how variables associated with stream habitat, primary production, and macroinvertebrate biomass account for variability in the biomass of cutthroat trout and total vertebrates (fish and salamanders) across a series of paired stream reaches with contrasting forest structure. Each of nine stream pairs consisted of an old-growth reach and a reach bordered by 40- to 60-yr-old second-growth riparian forest. We evaluated relationships between response and explanatory variables for each forest structure type using correlation analysis, regression analysis, and AICc model comparison analyses. We also conducted correlation and regression analyses on within-stream reach pair differences across the nine study streams. Canopy openness, nitrate concentration, periphyton chlorophyll a accrual, total invertebrate biomass, predatory invertebrate biomass, cutthroat trout biomass, and total vertebrate biomass were all positively correlated with each other, while temperature was negatively correlated with biotic variables. Within reach pairs, canopy openness emerged as the strongest correlate with top predators, with differences in canopy openness explaining 84% of the variation in vertebrate biomass differences in the paired analysis. Other habitat metrics were poorly correlated with invertebrate, fish, and salamander biomass for all analyses. Overall, these results suggest that for the stream reaches surveyed here, resource availability—as regulated through bottom-up, autotrophic pathways—is a dominant control on fish and other consumers. This highlights the importance of food resource limitation for fish and top predators in headwater streams, and illustrates how differences in canopy structure can affect bottom-up drivers of stream food webs.

Description: Light availability influences temperature, primary production, nutrient dynamics, and secondary production in aquatic ecosystems. In forested freshwater ecosystems, shading by streamside (riparian) vegetation is a dominant control on light flux and represents an important interaction at the aquatic–terrestrial interface. Changes in forest structure over time, particularly tree mortality processes that gradually increase light penetration through maturing forest canopies, are likely to influence stream light fluxes and associated ecosystem functions. We provide a set of conceptual models describing how stream light dynamics change with the development of complex canopy structure and how changes in light availability are likely to affect stream ecosystem processes. Shortly after a stand-replacing event, light flux to the stream is high, but light fluxes decline as canopies reestablish and close. Tree density, the degree of understory growth, patterns of tree mortality, and small-scale disturbances interact as drivers of multiple pathways of forest structural development. Changes in canopy structure will, in turn, influence stream light, which is expected to impact primary production and stream nutrient dynamics as well as the amount of autochthonous carbon supporting aquatic food webs. Ultimately, these conceptual models stress the importance of recovery from historic forest disturbances as well as future forest change as important factors influencing the long-term trajectories of ecosystem processes in headwaters.

Description: From the 1970s to 1990s, more stringent air quality regulations were implemented across North America and Europe to reduce chemical emissions that contribute to acid rain. Surface water pH slowly increased during the following decades, but biological recovery lagged behind chemical recovery. Fortunately, this situation is changing. In the past few years, northeastern US fish populations have begun to recover in lakes that were historically incapable of sustaining wild fish due to acidic conditions. As lake ecosystems across the eastern United States recover from acid deposition, the stress to the most susceptible populations of native coldwater fish appears to be shifting from acidification effects to thermal impacts associated with changing climate. Extreme summer temperature events – which are expected to occur with increasing frequency in the coming century – can stress and ultimately kill native coldwater fish in lakes where thermal stratification is absent or highly limited. Based on data from northeastern North America, we argue that recovery from acid deposition has the potential to improve the resilience of coldwater fish populations in some lakes to impacts of climate change. This will occur as the amount of dissolved organic carbon (DOC) in the water increases with increasing lake pH. Increased DOC will reduce water clarity and lead to shallower and more persistent lake thermoclines that can provide larger areas of coldwater thermal refuge habitat. Recovery from acidification will not eliminate the threat of climate change to coldwater fish, but secondary effects of acid recovery may improve the resistance of coldwater fish populations in lakes to the effects of elevated summer temperatures in historically acidified ecosystems. This analysis highlights the importance of considering the legacy of past ecosystem impacts and how recovery or persistence of those effects may interact with climate change impacts on biota in the coming decades. Declines in acid deposition have lead to recovery of trout in many mountain lake ecosystems across eastern North America. However, trout populations in these lakes are now under threat from increasing frequency and severity of hot summers. An unexpected by-product of recovery from acid rain may help mitigate against these climate change impacts. With acid recovery, dissolved organic matter is mobilized from soil, decreasing lake water clarity, which strengthens thermal stratification and enhances coldwater refuge for trout.