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Ibelings, B. W.

Publications and source records attributed to Ibelings, B. W..

3 recordsLinked to original sources

An abundant future for quagga mussels in deep European lakes

Quagga mussels have expanded their range across the northern hemisphere in recent decades owing to their dispersal abilities, prolific reproduction rates, and broad ecological tolerances. Their remarkable capacity to filter particulates from the water column has had profound effects on inland aquatic ecosystems. In the North American Great Lakes, quagga mussel populations have increased inexorably since the late 1980s, but it remains unclear whether quagga mussels will follow a similar trajectory in Europe where they have appeared more recently. Here we apply knowledge from a 33-year quagga population monitoring effort in the North American lakes to predict future quagga populations in deep European lakes, where quaggas are quickly becoming a conspicuous part of the underwater landscape. We predict that quagga mussel biomass in Lakes Biel, Constance, and Geneva may increase by a factor of 9 - 20 by 2045. Like in North America, this increase may be characterized by a shift to larger individuals and deeper depths as the population matures. If realized, this rapid expansion of quagga mussels would likely drive the largest aquatic ecosystem change in deep European lakes since the eutrophication period of the mid-20th century.

ecology↗

Temperature and resources interact to shape phytoplankton size-abundance relationships at a continental scale

Communities contain more individuals of small species and fewer individuals of large species. The observed -3/4 slope relating mean size and mean abundance across communities (the cross-community scaling relationship or CCSR) is thought to arise from a 3/4-power scaling of metabolic rate with body size. Assuming that 3/4-power metabolic scaling is universal, as claimed by the metabolic theory of ecology (MTE), size-abundance relationships should also be invariant with a scaling exponent of -3/4 or nearly so, across environmental conditions. However, we find that the CCSR slope is actually -1 overall (perhaps due to isometric metabolic scaling), and varies substantially across temperature and nutrient gradients in 1048 freshwater lake phytoplankton communities in the USA. The size-abundance relationship is most shallow at low temperatures and high nutrients, and steeper and relatively insensitive to nutrients at high temperatures. Phytoplankton communities have orders of magnitude more small or large cells depending on environmental conditions than would be predicted from the MTE. Although based on observational data, these results suggest that the environment alters either metabolic scaling or other poorly understood processes shaping community size distributions.

ecology↗

Complex effects of chytrid parasites on the growth of the cyanobacterium Planktothrix rubescens across interacting temperature and light gradients

Chytrids are important drivers of aquatic ecosystems as phytoplankton parasites. The interaction between these parasites and their hosts are shaped by abiotic factors such as temperature and light. Here, we performed a full-factorial experiment to study how temperature and light interact to affect the dynamics of the bloom-forming toxic cyanobacterium Planktothrix rubescens and its chytrid parasite. We used a dynamic host-parasite model to explore how temperature and light affect long term dynamics. At low temperatures, chytrids do not survive. Higher light and temperature levels stimulated both phytoplankton and chytrid growth, with complex effects on their dynamics. Model exploration indicates that increasing temperature and light shifts equilibrium outcomes from P. rubescens persisting alone to stable coexistence and then to limit cycles. This provides an alternative biological explanation for why P. rubescens is mainly found in the relatively cold and dark lake metalimnion - it may enable avoidance of its parasite. Our study emphasizes the importance of investigating how abiotic factors interact with biotic interactions to drive complex outcomes.

ecology↗