Each year the KBS LTER program awards two graduate students with summer research fellowships. Here Dustin Kincaid describes the research his summer fellowship supported. Dustin is a Ph.D. student in Steve Hamilton’s lab.
“ . . . the world is mud-luscious and puddle-wonderful” -ee cummings
Mud matters. Especially in shallow water bodies. Or at least I’m convinced it matters—enough to spend most of my 2014 field season hip and often eyeball deep in mud anyways. As water flows across the landscape, interactions with mud, or more appropriately, sediments, influence the fluxes of nutrients to downstream ecosystems. In shallow lakes and wetlands, reactions at the sediment-water interface (SWI) profoundly influence water chemistry by virtue of the their shallow depths and typically high biological demand. And in agricultural watersheds these shallow freshwater ecosystems may ameliorate the effects of nutrient pollution by removing or storing excess nitrogen and phosphorus flowing across the landscape.
Thick accumulations (>10 cm) of loosely consolidated organic sediment—hereafter referred to as flocculent sediments or floc—are typical of many if not most shallow freshwater ecosystems. I’m sure you’re familiar with it if you’ve ever gone for a swim in a pond or shallow lake. It’s that silky ooze you desperately try to avoid by floating on the surface and propelling yourself forward with horizontal frog kicks. The layer is not quite water, and not quite sediment. And who knows how deep you’d sink if you tried to stand up in it.
These accumulations represent a dynamic compartment akin to the well-studied hyporheic zone in lotic (flowing) systems where hydrology, geochemistry, and microbial life interact to drive biogeochemical transformations. Yet compared with stream hyporheic zones, surface and ground water interactions with flocculent sediment layers are poorly described. Most sediment studies collect cores from deeper waters and ignore or avoid any flocculent overlying layer, or lose it when the core impacts the sediment surface. Most limnological studies sample the overlying water, and most aquatic scientists chose to work on deeper water bodies. Little is known about the rates and controls of biogeochemical reactions in floc layers and their effect on exchanges of solutes with the overlying water column.
This summer with the support of a Kellogg Biological Station Long-term Ecological Research (KBS LTER) summer research fellowship, I sampled many small water bodies around KBS and used many approaches to better understand the functional role of flocculent sediments in shallow freshwater ecosystems. The fellowship support allowed me to build several novel sampling tools to characterize chemical processes within floc and at the floc-sediment interface. I now have a better handle on how to work with and in these unique sediments, several substantial data sets, and new hypotheses to explore during the rest of my dissertation research.
The KBS LTER summer research fellowship also supported my travel to the 2014 Joint Aquatic Sciences Meeting in Portland, Oregon.