Glacial deposits and landforms at the terminus of a Laurentide ice stream, Oneida Lake, New York, from multichannel seismic reflection data

The deglaciation record of the Ontario Lowland and Mohawk Valley of North America is important for constraining the retreat history of the Laurentide Ice Sheet, end-Pleistocene paleoclimate, and ice-sheet processes. The Mohawk Valley was an important meltwater drainage route during the last deglaciation, with the area around modern Oneida Lake acting as a valve for meltwater discharge into the North Atlantic Ocean. The Mohawk Valley was occupied by the Oneida Lobe and Oneida Ice Stream during the last deglacial period. Multichannel seismic reflection data can be used to generate images of preglacial surfaces and internal structures of glacial bedforms and proglacial lake deposits, thus contributing to studies of deglaciation. This paper uses 217 km of offshore multichannel seismic reflection data to image the entire Quaternary section of the Oneida basin. A proglacial lake and paleo-calving margin is interpreted, which likely accelerated the Oneida Ice Stream, resulting in elongated bedforms observed west of the lake. The glacial bedforms identified in this study are buried by proglacial lake deposits, indicating the Oneida basin contains a record of glacial meltwater processes, including a 60-m-thick proglacial interval in eastern Oneida Lake.

The quick and the dead: copepods dominate as cladocerans decline following invasion by Hemimysis anomala

The North American invasion of a non-native mysid, Hemimysis anomala, has been expanding since 2006, with the first inland lake invasions detected for Oneida Lake in 2009 and Seneca Lake in 2010. Although we know that Hemimysis primarily consumes zooplankton, our ability to predict the community-level impact of an invasion is hampered by a lack of information on taxon-specific effects. To investigate the effects of Hemimysis on native zooplankton, we conducted two mesocosm experiments that compared composition between communities with and without Hemimysis and studied how the effects of this predator on zooplankton species composition varied across a natural gradient of low to high invader densities (0.01–0.1 individuals·L−1). Our first experiment found that Hemimysis primarily affected cladocerans, and particularly Daphnia, shifting communities towards dominance by copepods. Our second experiment showed that Hemimysis invasions may do little to suppress Daphnia abundances until between 0.067–0.11 individuals·L−1 or higher. Cladocerans are important links in freshwater trophic transfer and the nutrient cycle, and disruption of these linkages following Hemimysis invasion could result in both bottom-up and top-down impacts in nearshore food webs. However, Hemimysis can also fill a similar trophic role as the zooplankton they consume, and longer-term experiments are required to better assess their eventual impacts on native communities.