Biology subjects

Kraemer, B. M.

Publications and source records attributed to Kraemer, B. M..

4 recordsLinked to original sources

bioRxiv2025

Political legacies shape bear use of anthropogenic spaces

Romania hosts Europes largest brown bear population west of Russia, but rising human-bear encounters and related casualties raise concerns about their drivers and future population management. Using >10,000 encounter reports (2019-2024) in a hierarchical occupancy model accounting for detection processes, we show that bear presence in human-dominated spaces is linked to food conditioning, habituation, and shaped by historical management. Bears occur more often in high wildland-urban interface areas, especially those closer to communist-era elite-hunting grounds with feeding sites. These patterns reflect a long-term legacy of 1960s population management policies interacting with environmental and behavioral processes to shape recent bear behavior. We call for management addressing ecological and social sustainability by phasing out supplemental feeding, reducing habituation through a restored landscape of fear, improving public knowledge of bear ecology, and recognizing historical legacies to promote coexistence. HighlightsO_LIWe used hierarchical species occupancy models to analyze brown bears use of human-dominated spaces in Romania. C_LIO_LIBear detectability depends strongly on activity patterns of both bears and humans C_LIO_LIBear occurrence in anthropogenic spaces is strongly associated with high wildland-urban interface areas and abundant anthropogenic food waste. C_LIO_LIBear occurrence in WUI areas is modulated by historical population management legacies. C_LI

ecology↗

bioRxiv2023

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↗

bioRxiv2019

Depth-discrete eco-genomics of Lake Tanganyika reveals roles of diverse microbes, including candidate phyla, in tropical freshwater nutrient cycling

Lake Tanganyika (LT) is the largest tropical freshwater lake, and the largest body of anoxic freshwater on Earths surface. LTs mixed oxygenated surface waters float atop a permanently anoxic layer and host rich animal biodiversity. However, little is known about microorganisms inhabiting LTs 1470 m deep water column and their contributions to nutrient cycling, which affect ecosystem-level function and productivity. Here, we applied genome-resolved metagenomics and environmental analyses to link specific taxa to key biogeochemical processes across a vertical depth gradient in LT. We reconstructed 523 unique metagenome-assembled genomes (MAGs) from 21 bacterial and archaeal phyla, including many rarely observed in freshwater lakes. We identified sharp contrasts in community composition and metabolic potential with an abundance of typical freshwater taxa in oxygenated mixed upper layers, and Archaea and uncultured Candidate Phyla in deep anoxic waters. Genomic capacity for nitrogen and sulfur cycling was abundant in MAGs recovered from anoxic waters, highlighting microbial contributions to the productive surface layers via recycling of upwelled nutrients, and greenhouse gases such as nitrous oxide. Overall, our study provides a blueprint for incorporation of aquatic microbial genomics in the representation of tropical freshwater lakes, especially in the context of ongoing climate change which is predicted to bring increased stratification and anoxia to freshwater lakes.

microbiology↗

bioRxiv2019

Adoption and consequences of new light-fishing technology (LEDs) on Lake Tanganyika, East Africa

Maintaining sustainable fisheries requires understanding the influence of technological advances on catch efficiency. Fisheries using light sources for attraction could be widely impacted by the shift to light emitting diode (LED) light systems. We studied the transition from kerosene lanterns to LED lamps in Lake Tanganyika, East Africa, examining factors that led to adoption as well as the impact of the new light sources on fish catch and composition. We used a combination of field experiments with catch assessments, fisher surveys, underwater light spectra measurements, and cost assessments to evaluate the impact of switching from kerosene to LED lamps. Overall, we found a very rapid rate of adoption of homemade outdoor LED light systems in Lake Tanganyika. Most of the batteries used to power these lamps were charged from the city power grid, rather than photovoltaic cells. The LED light spectra was distinct from the kerosene light and penetrated much deeper into the water column. Regardless of light type, most of the fish caught within the two dominant species were below maturity, indicating that current fishery is not sustainable. Although the LED lamps were associated with a slight increase in catch, environmental factors, particularly distance offshore, were generally more important in determining fish catch size and composition. The main advantages of the LED lamps were the lower operating costs and their robustness in bad weather. Overall, the use of battery-powered LED lighting systems to attract fish in Lake Tanganyika appears to reduce economic costs but not contribute new impacts on the fishery.

scientific communication and education↗