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Michelle C. Jackson Tian Zhao Antoine Lecerf J. Robert Britton Julien Cucherousset 《Freshwater Biology》2017,62(9):1501-1510
- The trophic ecology of invasive species has important implications for their impacts on recipient ecosystems, with omnivorous invaders potentially affecting native species and processes over multiple trophic levels. The trophic ecology of invaders might be affected by both their body size and the characteristics of their habitat due to variation in energy requirements and resource availability.
- Here, using stable‐isotope analysis, we investigated the trophic ecology of the invasive crayfish Procambarus clarkii in 15 populations in southwest France over a gradient of individual (crayfish body size), population (crayfish abundance) and ecosystem (lake size, productivity and predation pressure) characteristics. We predicted that population niche width, level of omnivory and trophic position of individuals would change with abiotic and biotic conditions, but that these relationships would vary with lake size.
- The trophic position of individual crayfish increased with body size in lakes with low productivity, but decreased with body size in more productive lakes. As crayfish abundance increased (and therefore potential intraspecific competition), individual trophic position and population niche width decreased. This was most apparent in smaller lakes, suggesting it related to an increase in encounter rates with conspecifics.
- Body size, population abundance, lake size and lake productivity influenced the trophic ecology of invasive crayfish, which can affect their interactions with native species. Our results demonstrated that the trophic ecology of invasive species can be variable across invaded landscapes, with implications for their ecological impacts on native communities. This emphasizes the importance of characterising the diet of invasive species across their non‐native range and environmental gradients to better predict and manage their impacts.
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Katya E. Kovalenko Euan D. Reavie J. David Allan Meijun Cai Sigrid D. P. Smith Lucinda B. Johnson 《Freshwater Biology》2017,62(2):366-381
- Phytoplankton communities can experience nonlinear responses to changing nutrient concentrations, but the nature of species shifts within phytoplankton is not well understood and few studies have explored responses of pelagic assemblages in large lakes.
- Using pelagic phytoplankton data from the Great Lakes, we assessed phytoplankton assemblage change‐point responses to nutrients and invasive Dreissena, characterising community responses in a multi‐stressor environment and determine whether species responses to in situ nutrients can be approximated from nutrient loading.
- We demonstrate assemblage shifts in phytoplankton communities along major stressor gradients, particularly prominent in spring assemblages, providing insight into community thresholds at the lower end of the phosphorus gradient and species‐stressor responses in a multi‐stressor environment. We show that responses to water nutrient concentrations could not be estimated from large‐scale nutrient loading data likely due to lake‐specific retention time and long‐term accumulation of nutrients.
- These findings highlight the potential for significant accumulation of nitrates in ultra‐oligotrophic systems, nonlinear responses of phytoplankton at nutrient concentrations relevant to current water quality standards and system‐specific (e.g. lake or ecozone) differences in phytoplankton responses likely due to differences in nutrient co‐limitation and effects of dreissenids.
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Gretchen J. A. Hansen Jordan S. Read Jonathan F. Hansen Luke A. Winslow 《Global Change Biology》2017,23(4):1463-1476
Temperate lakes may contain both coolwater fish species such as walleye (Sander vitreus) and warmwater fish species such as largemouth bass (Micropterus salmoides). Recent declining walleye and increasing largemouth bass populations have raised questions regarding the future trajectories and management actions for these species. We developed a thermodynamic model of water temperatures driven by downscaled climate data and lake‐specific characteristics to estimate daily water temperature profiles for 2148 lakes in Wisconsin, US, under contemporary (1989–2014) and future (2040–2064 and 2065–2089) conditions. We correlated contemporary walleye recruitment and largemouth bass relative abundance to modeled water temperature, lake morphometry, and lake productivity, and projected lake‐specific changes in each species under future climate conditions. Walleye recruitment success was negatively related and largemouth bass abundance was positively related to water temperature degree days. Both species exhibited a threshold response at the same degree day value, albeit in opposite directions. Degree days were predicted to increase in the future, although the magnitude of increase varied among lakes, time periods, and global circulation models (GCMs). Under future conditions, we predicted a loss of walleye recruitment in 33–75% of lakes where recruitment is currently supported and a 27–60% increase in the number of lakes suitable for high largemouth bass abundance. The percentage of lakes capable of supporting abundant largemouth bass but failed walleye recruitment was predicted to increase from 58% in contemporary conditions to 86% by mid‐century and to 91% of lakes by late century, based on median projections across GCMs. Conversely, the percentage of lakes with successful walleye recruitment and low largemouth bass abundance was predicted to decline from 9% of lakes in contemporary conditions to only 1% of lakes in both future periods. Importantly, we identify up to 85 resilient lakes predicted to continue to support natural walleye recruitment. Management resources could target preserving these resilient walleye populations. 相似文献
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