Mulhollem J.J.,Kaskaskia Biological Station |
Mulhollem J.J.,University of Illinois at Urbana - Champaign |
Mulhollem J.J.,Vermont Agency of Natural Resources |
Colombo R.E.,Eastern Illinois University |
And 2 more authors.
Aquatic Sciences | Year: 2016
Numerous simulation studies have considered the effects of impending climate change on lakes. Predictive models exist for the responses of a multitude of variables to a warmer climate, and potential effects on food webs and ecosystem functions. Although these predictions are numerous, there is a need for manipulative experiments testing for the effects of warming on actual lake systems. We used power plant lakes across the central Midwestern US as a substitute for future climate change effects. These treatment lakes receive heated effluent and are typically 2–6 °C warmer than other regional lakes. We collected data from 1997 to 2010 on a number of abiotic and biotic variables from three of these treatment lakes and six control lakes that were of similar size and location but did not have an artificial thermal regime. Phosphorus and phytoplankton concentrations were similar between treatment groups, although treatment lakes had greater phosphorus and less phytoplankton in September. No differences existed in turbidity (measured as Secchi depth transparency). Zooplankton were less abundant in treatment lakes than in control lakes throughout our sampling period (May–October), with differences in cladocerans driving this disparity. There was evidence of earlier spawning of gizzard shad (Dorosoma cepedianum) due to the warmer temperature regime, but not for bluegill (Lepomis macrochirus). Average sizes of juvenile bluegill were larger in warmed systems in July and August. Juvenile largemouth bass (Micropterus salmoides) were larger in heated systems in June, but no differences existed in July or August. Growth of adult largemouth bass was greater in systems with a warmer thermal regime. Our results provide insights into patterns that can be expected in the future, and may be used to further understand the wide-reaching implications of climate change. © 2016 Springer International Publishing
Shoup D.E.,Kaskaskia Biological Station |
Shoup D.E.,Oklahoma State University |
Wahl D.H.,Kaskaskia Biological Station
Transactions of the American Fisheries Society | Year: 2011
For many species of fish, size-specific overwinter mortality is an important factor structuring year-class strength. Protracted spawning by bluegill Lepomis macrochirus leads to extreme variation in individual size going into winter that could result in strong, size-specific overwinter mortality, particularly in locations with limited food resources or long, cold winters. We performed laboratory trials to test the effects of winter temperature (4°C or 9°C) and food availability (food present or no food) on the survival of two size-classes (20-30 or 50-60 mm total length) of young-ofyear bluegills. Mortality was strongly size selective and appeared to be related to relative condition, suggesting that energy limitation was the primary mechanism of mortality. Fish of both sizes were less active at colder temperatures, leading to increased survival (presumably via reduced energy expenditure). Bluegills fed heavily in food treatments (wet weight/d consumed was typically 2-4% for both large and small fish in the warm treatment, 1-2.5% for small fish in the cold treatment, and 0.4-0.8% for large fish in the cold treatment) and experienced increased survival. However, small fish in all treatments had more than 55% mortality after 150 d, indicating that some of the mortality was not due to starvation. It appears that late-spawned, small fish are unlikely to survive lengthy periods of winter conditions and will therefore be selected against at northern latitudes. Mechanisms other than overwinter mortality that lead to increased lifetime reproductive success may explain the persistence of late-summer or fall spawning at these latitudes. © American Fisheries Society 2011.
O'Connor C.M.,Carleton University |
O'Connor C.M.,McMaster University |
Nannini M.,Sam Parr Biological Station |
Wahl D.H.,Kaskaskia Biological Station |
And 3 more authors.
Journal of Experimental Zoology Part A: Ecological Genetics and Physiology | Year: 2013
Experimental implants were used to investigate the effect of elevated cortisol (the primary stress hormone in teleost fish) on energetic and physiological condition prior to reproduction in male and female largemouth bass (Micropterus salmoides). Fish were wild-caught from lakes in Illinois, and held in experimental ponds for the duration of the study. Between 9 and 13 days after cortisol treatment, and immediately prior to the start of the reproductive period, treated and control animals were sampled. Females exhibited lower muscle lipid content, lower liver glycogen content, and higher hepatosomatic indices than males, regardless of treatment. Also, cortisol-treated females had higher hepatosomatic indices and lower final mass than control females, whereas males showed no differences between treatment groups. Finally, cortisol-treated females had higher gonadal cortisol concentrations than control females. In general, we found evidence of reduced energetic stores in female fish relative to male fish, likely due to timing differences in the allocation of resources during reproduction between males and females. Perhaps driven by the difference in energetic reserves, our data further suggest that females are more sensitive than males to elevated cortisol during the period immediately prior to reproduction. © 2012 Wiley Periodicals, Inc.
DeBoom C.S.,Kaskaskia Biological Station |
DeBoom C.S.,Urbana University |
Wahl D.H.,Kaskaskia Biological Station |
Wahl D.H.,Urbana University
Hydrobiologia | Year: 2014
Recent syntheses of trophic cascade and biomanipulation research have suggested that the effects of piscivores on planktivorous fish populations are reduced, when planktivores are capable of outgrowing predator gape limitation and in systems with complex food web interactions. These hypotheses, however, have not been tested in long-term, whole-lake, experiments where processes such as fish recruitment and compensatory food web responses may be important. We conducted a replicated whole-lake experiment to test for the effects of supplemental piscivore introductions on food webs of eutrophic lakes dominated by deep-bodied planktivores. Responses to piscivore enhancement were compared between lakes differing in food web structure due to the presence of omnivorous gizzard shad (Dorosoma cepedianum). A significant decrease in the relative abundance of juvenile planktivorous fish, and an increase in total benthic macroinvertebrate density was observed in lakes containing mainly bluegills (Lepomus machrochirus). In contrast, lakes containing gizzard shad exhibited no significant responses to piscivore manipulation. Our results support the hypothesis that food webs in lakes dominated by deep-bodied planktivorous fish species respond weakly to piscivore enhancement. In addition, our findings support the hypothesis that cascading trophic interactions are weaker in lake ecosystems with more complex food web interactions such as those containing gizzard shad. © 2014 Springer International Publishing Switzerland.
Vanlandeghem M.M.,Kaskaskia Biological Station |
Carey M.P.,National Oceanic and Atmospheric Administration |
Wahl D.H.,Kaskaskia Biological Station
Ecology of Freshwater Fish | Year: 2011
In natural systems, prey frequently interact with multiple predators and the outcome often cannot be predicted by summing the effects of individual predator species. Multiple predator interactions can create emergent effects for prey, but how those change across environmental gradients is poorly understood. Turbidity is an environmental factor in aquatic systems that may influence multiple predator effects on prey. Interactions between a cruising predator (largemouth bass Micropterus salmoides) and an ambush predator (muskellunge Esox masquinongy) and their combination foraging on a shared prey (bluegill Lepomis macrochirus) were examined across a turbidity gradient. Turbidity modified multiple predator effects on prey. In clear water, combined predators consumed in total more prey than expected from individual predator treatments, suggesting risk enhancement for prey. In moderately turbid water, the predators consumed fewer prey together than expected, suggesting a risk reduction for prey. At high turbidity, there were no apparent emergent effects; however, the cruising predator consumed more prey than the ambush predator, suggesting an advantage for this predator. Understanding multiple predator traits across a gradient of turbidity increases our understanding of how complex natural systems function. © 2011 John Wiley & Sons A/S.