PhD Oral Defense: Impacts of dissolved organic carbon on productivity of fish and benthic macroinvertebrates in north temperate lakes

PhD Oral Defense of Nicola Craig, Natural Resource Sciences

Over the past several decades, increases in concentrations of dissolved organic carbon (DOC) have been observed in many north temperate aquatic ecosystems, a phenomenon known as aquatic 'browning'. However the ecological consequences of this increase are not well understood. DOC from terrestrial sources stain lake waters a dark brown color, and can have strong effects on the physical and biological structure of lake ecosystems. This occurs through its associated light and heat attenuating properties, which reduce thermocline depths, and thus the area of light, warm, and well-oxygenated habitat in DOC-rich lakes. Recent work has shown that fish productivity decreases along a gradient of increasing DOC, however the mechanisms behind this have not been fully explored. Here, Nicola demonstrates potential mechanisms for this loss in productivity by determining how DOC affects zoobenthos, a primary prey item for many fish, as well as how DOC affects fish feeding efficiency and life history strategies.

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