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Citation

Lyu, K., L. Zhang, L. Gu, X. Zhu, A. E. Wilson, and Z. Yang. 2017. Cladoceran offspring tolerance to toxic Microcystis is promoted by maternal warming. Environmental Pollution 227:451-459.

Abstract

Elevated temperatures and nutrients can favor phytoplankton dominance by cyanobacteria, which can be toxic to zooplankton. There is growing awareness that maternal effects not only are common but can also significantly impact ecological interactions. Although climate change is broadly studied, relatively little is known regarding its influence on maternal effects in zooplankton. Given that lakes are sentinels for climate change and that elevated temperatures and nutrient pollution can favor phytoplankton dominance by toxic cyanobacteria, this study focused on elucidating the effects of maternal exposure to elevated temperatures on the tolerance of zooplankton offspring to toxic cyanobacteria in the diet. Three different maternal thermal environments were used to examine population fitness in the offspring of two cladoceran species that vary in size, including the larger Daphnia similoides and the smaller Moina macrocopa, directly challenged by toxic Microcystis. Daphnia and Moina mothers exposed to elevated temperatures produced offspring that were more resistant to Microcystis. Such findings may result from life-history optimization of mothers in different temperature environments. Interestingly, offspring from Moina fed with toxic Microcystis performed better than Daphnia offspring, which could partially explain the dominance of small cladocerans typically observed during cyanobacterial blooms. The present study emphasizes the importance of maternal effects on zooplankton resistance to cyanobacteria mediated through environmental warming and further highlights the complexities associated with the abiotic factors that influence zooplankton-cyanobacteria interactions.

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Olsen, B. K., M. F. Chislock, A. Rebelein, and A. E. Wilson. 2017. Nutrient enrichment and vertical mixing mediate 2-methylisoborneol and geosmin concentrations in a drinking water reservoir. Water Science and Technology: Water Supply 17(2):500-507.

Abstract

Few ecosystem-level studies have experimentally determined the physicochemical and biological factors that mediate concentrations of off-flavor compounds in drinking water reservoirs. Consequently, the watershed-scale mechanisms determining production of these compounds are still poorly understood. In a recent study, the addition of both nitrogen and phosphorus significantly increased 2-methylisoborneol (MIB). Not surprisingly, MIB was correlated with cyanobacterial abundance (a well-known producer of off-flavor compounds); however, MIB was most strongly correlated with diatom abundance. To empirically test for differences in the production of two important off-flavor compounds, specifically MIB and geosmin, by either cyanobacteria or diatoms, we conducted a fully factorial experiment that manipulated two factors that typically promote cyanobacteria (nitrogen and phosphorus fertilization) or diatoms (vertical mixing of the water column). As predicted, fertilization promoted cyanobacteria, and vertical mixing favored diatoms. Interestingly, the production of geosmin was rapid and consistent with an increase in cyanobacteria while MIB production increased later in the experiment when cyanobacterial biovolume tended to decline and diatom biovolume increased. Based on our current and previous studies, MIB and geosmin production is associated with cyanobacteria, but the direct or indirect influence of diatoms on production should not be ignored.

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Kollock, R., K. Games, A. E. Wilson, and J. Sefton. 2016. Vehicle exposure and spinal musculature in military warfighters: a meta-analysis. Journal of Athletic Training 51(11):981-990.

Abstract

Context: Spinal musculature fatigue from vehicle exposure may place warfighters at risk for spinal injuries and pain. Research on the relationship between vehicle exposure and spinal musculature fatigue is conflicting. A better understanding of the effect of military duty on musculoskeletal function is needed before sports medicine teams can develop injury-prevention programs. Objective: To determine if the literature supports a definite effect of vehicle exposure on spinal musculature fatigue. Data sources: We searched the MEDLINE, Military & Government Collection (EBSCO), National Institute for Occupational Safety and Health Technical Information Center, PubMed, and Web of Science databases for articles published between January 1990 and September 2015. Study selection: To be included, a study required a clear sampling method, preexposure and postexposure assessments of fatigue, a defined objective measurement of fatigue, a defined exposure time, and a study goal of exposing participants to forces related to vehicle exposure. Data extraction: Sample size, mean preexposure and postexposure measures of fatigue, vehicle type, and exposure time. Data synthesis: Six studies met the inclusion criteria. We used the Scottish Intercollegiate Guidelines Network algorithm to determine the appropriate tool for quality appraisal of each article. Unweighted random-effects model meta-analyses were conducted, and a natural log response ratio was used as the effect metric. The overall meta-analysis demonstrated that vehicle exposure increased fatigue of the spinal musculature (P = .03; natural log response ratio = -0.22, 95% confidence interval = -0.42, -0.02). Using the spinal region as a moderator, we observed that vehicle ride exposure significantly increased fatigue at the lumbar musculature (P = .02; natural log response ratio = -0.27, 95% confidence interval = -0.50, -0.04) but not at the cervical or thoracic region. Conclusions: Vehicle exposure increased fatigue at the lumbar region.

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Wilson, A. E. and Z. A. Osorio. 2016. DEB Numbers: Are aquatic ecologists underrepresented? DEBrief (NSF’s Division of Environmental Biology blog) 11 July 2016.

Abstract

Generalizability has been fundamental to the major advances in environmental biology and is an important trait for current research ideas proposed to NSF. Despite its significance, a disconnect between terrestrial and aquatic ecological research has existed for several decades (Hairston 1990).

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Wilson, A. E. and Z. A. Osorio. 2016. DEB Numbers: Are aquatic ecologists underrepresented? DEBrief (NSF’s Division of Environmental Biology blog) 11 July 2016.

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Olsen, B. K., M. F. Chislock, and A. E. Wilson. 2016. Eutrophication mediates a common off-flavor compound, 2-methylisoborneol, in a drinking water reservoir. Water Research 92:228-234. 

Abstract

Off-flavors, such as 2-methylisoborneol (MIB) and geosmin, cause drinking water to have earthy or musty tastes and odors. Humans can detect such compounds at minute concentrations (10 and 30 ng/L for MIB and geosmin, respectively), and, although not a health risk, off-flavors can promote consumer distrust. Removal of these compounds is costly and often unreliable or only suitable under certain conditions. Minimizing off-flavor production at the watershed-scale may be more cost-effective in addition to improving ecosystem health and aesthetics. Cyanobacteria are considered to be the primary drivers of off-flavors in freshwater systems. Due to their ability to produce toxins, cyanobacteria have been under particular scrutiny, and environmental factors promoting cyanobacterial blooms are relatively well-studied. Using this body of literature, we conducted a seven-week, limnocorral experiment where we manipulated nitrogen and nitrogen-to-phosphorus concentrations to influence phytoplankton community structure and off-flavor production. The addition of a single nutrient across broad ranges (nitrogen or phosphorus) had no effect on MIB. However, the addition of both nitrogen and phosphorus promoted high concentrations of MIB relative to treatments that received no nutrients (448% increase) or only nitrogen or phosphorus (722% increase). Interestingly, cyanobacteria waned during the experiment and were replaced by diatoms, which were the dominant taxa by the end of the experiment. Our findings clearly show that eutrophication affects MIB production, but mechanisms leading to the production of this compound may differ from what has been previously predicted.

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Ger, K. A., P. Urrutia-Cordero, P. C. Frost, L.-A. Hansson, O. Sarnelle, A. E. Wilson, and M. Lurling. 2016. The interaction between cyanobacteria and zooplankton in a more eutrophic world. Harmful Algae 54:128-144.  (Clarivate Analytics Web of Science Highly Cited Paper)

Abstract

As blooms of cyanobacteria expand and intensify in freshwater systems globally, there is increasing interest in their ecological effects. In addition to being public health hazards, cyanobacteria have long been considered a poor quality food for key zooplankton grazers that link phytoplankton to higher trophic levels. While past laboratory studies have found negative effects of nutritional constraints and defensive traits (i.e., toxicity and colonial or filamentous morphology) on the fitness of large generalist grazers (i.e., Daphnia), cyanobacterial blooms often co-exist with high biomass of small-bodied zooplankton in nature. Indeed, recent studies highlight the remarkable diversity and flexibility in zooplankton responses to cyanobacterial prey. Reviewed here are results from a wide range of laboratory and field experiments examining the interaction of cyanobacteria and a diverse zooplankton taxa including cladocerans, copepods, and heterotrophic protists from temperate to tropical freshwater systems. This synthesis shows that longer exposure to cyanobacteria can shift zooplankton communities toward better-adapted species, select for more tolerant genotypes within a species, and induce traits within the lifetime of individual zooplankton. In turn, the function of bloom-dominated plankton ecosystems, the coupling between primary producers and grazers, the stability of blooms, and the potential to use top down biomanipulation for controlling cyanobacteria depend largely on the species, abundance, and traits of interacting cyanobacteria and zooplankton. Understanding the drivers and consequences of zooplankton traits, such as physiological detoxification and selective vs. generalist grazing behavior, are therefore of major importance for future studies. Ultimately, co-evolutionary dynamics between cyanobacteria and their grazers may emerge as a critical regulator of blooms.

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Lyu, K., H. Guan, C. Wu, X. Wang, A. E. Wilson, and Z. Yang. 2016. Maternal consumption of non-toxic Microcystis by Daphnia magna induces tolerance to toxic Microcystis in offspring. Freshwater Biology 61:219-228 

Abstract

  1. Freshwater cyanobacterial blooms are a worldwide environmental issue. These blooms often comprise both non-toxic and toxic species and strains. Populations of some zooplankton, including Daphnia, have been shown to adapt locally to toxic Microcystis through maternal effects. However, Microcystis populations vary spatially and temporally in the absolute and relative abundances of non-toxic and toxic genotypes.
  2. We examined variation in induction of tolerance to toxic cyanobacteria in offspring from two Daphnia magna clones (JS and AH) fed diets containing Scenedesmus by itself or in combination with either a non-toxic or a toxic clone of Microcystis aeruginosa. The diets containing Microcystis included relatively more cyanobacteria within each week of the 3 week experiment (week 1–10%, week 2–20%, week 3–40%). Daphnia neonates were collected from these three treatments at the end of the third week and fed a diet containing Scenedesmus and toxic Microcystis for 3 weeks before a suite of life-history, physiological and biochemical measurements were made on the surviving animals.
  3. Neonates from mothers fed toxic and non-toxic Microcystis showed enhanced growth and reproduction compared to neonates produced from mothers fed only Scenedesmus. Our results showed that Daphnia neonates could be induced to tolerate toxic cyanobacteria when their mothers were fed diets containing non-toxic or toxic strains of cyanobacteria. Furthermore, elevated RNA–DNA ratios, superoxide dismutase activity and catalase activity in neonates fed diets containing non-toxic or toxic Microcystis clones suggested that the mechanisms behind these changes involved processes associated with metabolism and antioxidation.

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Kollock, R., C. Andrews, A. Johnston, T. Elliott, A. E. Wilson, K. Games, and J. Sefton. 2016. A meta-analysis to determine if lower extremity muscle strengthening should be included in military knee overuse injury prevention programs. Journal of Athletic Training 51(11):919-926.

Abstract

Context: Knee overuse injuries are the most common musculoskeletal complaints in military trainees and are common in active-duty warfighters. Muscle strengthening is usually recommended; however, research is conflicting in this area, which makes it difficult to develop effective screening, prevention, and training interventions for warfighters. Objective: To determine if lower extremity muscular weakness contributes to knee overuse injuries and identify specific muscular involvement. Data sources: We searched MEDLINE, PubMed, Web of Science, SPORTDiscus, CINAHL, and Military & Government Collection and reference lists of relevant articles published between January 1, 2000, and January 1, 2013. Study selection: For inclusion, requirements were uninjured and injured groups; provision of the sample size, means, and standard deviations for all groups; identification of the specific muscles assessed; and clearly defined knee injury. Data extraction: Sample size, sex, and muscle strength means and standard deviations. Data synthesis: Twenty-five studies met these criteria. We used the Scottish Intercollegiate Guidelines Network algorithm to determine the appropriate tool for appraising article quality. Unweighted random-effects model meta-analyses were conducted. Separate meta-analyses were performed for the moderators of strength measurement scale (absolute or normalized muscle strength), muscle group, and sex. A weighted random-effects model with a Hedges g effect metric and 95% confidence intervals were used for comparison across studies. Conclusions: Our meta-analysis suggests that individuals with symptoms of a knee overuse injury have lower absolute and normalized hip muscle strength. Specifically, they had lower absolute hip external-rotator, knee-extensor, and knee-flexor strength, as well as lower normalized hip external-rotator, hip-extensor, and hip-abductor strength, compared with asymptomatic control participants. The findings suggest a possible link between lower hip and thigh strength and knee overuse injuries. Further research is needed to determine if weakness is a cause or a result of knee overuse injuries before screening and intervention can be developed for at-risk warfighters.

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Koch, R. E., A. E. Wilson, and G. E. Hill. 2016. The importance of carotenoid dose in supplementation studies with songbirds. Physiological and Biochemical Zoology 89(1):61-71.

Abstract

Carotenoid coloration is the one of the most frequently studied ornamental traits in animals. Many studies of carotenoid coloration test the associations between carotenoid coloration and measures of performance, such as immunocompetence and oxidative state, proceeding from the premise that carotenoids are limited resources. Such studies commonly involve supplementing the diets of captive birds with carotenoids. In many cases, however, the amount of carotenoid administered is poorly justified, and even supposedly carotenoid-limited diets may saturate birds’ systems. To quantify the relationships among the amount of carotenoids administered in experiments, levels of circulating carotenoids, and quantities of carotenoids deposited into colored ornaments, we performed a meta-analysis of 15 published studies that supplemented carotenoids to one of seven songbird species. We used allometric scaling equations to estimate the per-gram carotenoid consumption of each study’s subjects, and we used meta-regression to evaluate the effects of this carotenoid dose on differences in coloration and plasma carotenoid levels between supplemented and control groups of birds. After accounting for supplementation duration and species, we observed a significant positive correlation between carotenoid intake and response of plasma carotenoid level to supplementation. The presence of supplemental carotenoids also tended to increase the expression of ornamental coloration, but the magnitude of the carotenoid dose did not significantly affect how strongly coloration changed with supplementation. Further, coloration effect sizes had no significant relationship with plasma carotenoid effect sizes. We also found significant heterogeneity in responses among studies and species, and the parameters used to measure color significantly affected response to supplementation. Our results emphasize the importance of performing dosage trials to determine what supplementation levels provide limited versus surplus carotenoids and of measuring the natural level of carotenoid intake by the study species to validate the appropriateness of supplementation levels for a particular study species and experimental design.

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