Organic matter processing in arctic lake sediments

Lakes are a common landscape feature in the arctic and interact with carbon cycling through the sequestration of organic matter in their sediments. My research assessed the relative importance of landscape- and within-lake-scale factors on organic matter cycling in arctic lake sediments. Sediment organic matter mineralization (measured as sediment oxygen demand) varied between -8 and 40 mmol O2 m-2 d-1 and was proportional to water temperature and oxygen concentration. There was greater variation in organic matter mineralization within lakes than between lakes, suggesting that variation in mineralization occurs primarily at the within-lake scale. At the both the landscape- and within-lake-scale, sediment slurries with greater percent organic matter had a higher rate of dissolved inorganic carbon (DIC) production and the effect of oxygen exposure on DIC production was greatest in those sediments with the lowest percent organic matter. Despite the variation in mineralization, organic matter content of the sediments (17 to 69%) varied primarily among lakes (i.e., at the landscape-scale) and was driven by organic matter inputs via benthic primary production. My results suggest that the attenuation of light by dissolved organic carbon in the water indirectly influences organic matter storage in arctic lake sediments. In addition to the direct limitations of organic matter input via benthic photosynthesis, the amount of light attenuation indirectly alters sediment organic matter cycling via changes to the distribution of temperature and oxygen within the lake. Light attenuation was inversely proportional to the depth of thermal stratification, which determines the distribution of temperature and oxygen in stratified lakes. I estimated that a doubling of the light attenuation would result in a 30% decrease in the area of the sediments exposed to the relatively warm and oxygenated waters of the epilimnion. The interconnection between these factors provides a potential climate change feedback to arctic carbon cycling. Changes in terrestrial organic matter inputs to lakes due to climate change will alter transparency and the depth of the thermocline, changing the distribution of light, temperature and oxygen in the lake and thus the factors limiting the production and decomposition of organic matter in the lake sediments

Does A Predator Transition Determine The Distribution Of Crayfish In The New River, NC?

The stream-dwelling crayfish fauna of the New River in western NC, consists of three common species (Orconectes cristavarius, Cambarus chasmodactylus, and Cambarus bartonni) and a rare species (Cambarus aspermanus) . . . In this study I evaluated the factors that may be responsible for the virtual absence of C. chasmodactylus YOY from the New River, despite the presence of the adults . . . The importance of abiotic factors and competition was tested using a target-neighbor design field experiment where a uniform density of C. chasmodactylus YOY was enclosed in the New River with O. cristavarius YOY at densities ranging from none to approximately two times ambient density . . . The results of this study suggest that this shift in predatory fish type may be important in determining the distribution of crayfish species in the New River

Relationships between lake transparency, thermocline depth, and sediment oxygen demand in Arctic lakes

The burial of organic matter within lake sediments can be a significant component of landscape carbon cycling. Whether organic matter deposited in lake sediments is sequestered or mineralized depends on factors limiting the decomposition rate of organic matter, such as temperature and the availability of oxygen. In stratified lakes, the distribution of temperature and oxygen is determined by the depth of the thermocline, and therefore sediment organic matter burial should be sensitive to changes in thermocline depth. Using a survey of more than 30 lakes over 3 years in the Alaskan Arctic, we found that thermocline depth during the summer was positively correlated with water transparency. Furthermore, using sediment incubations from 3 lakes, we found that variation in sediment oxygen demand is primarily affected by variation in temperature and the availability of oxygen with limited effect of the source of the sediments. Because variation in temperature and oxygen concentration in stratified lakes is mainly determined by the depth of thermocline, these results indicate that changes in transparency can have indirect effects on the rate of organic matter mineralization in lakes. A reduction in thermocline depth that results from decreased lake transparency may decrease the breakdown of sediment organic matter and increase the storage of organic carbon in lake sediments

Biomarkers of nanomaterials hazard from multi-layer data

Nanomaterials have a range of potential applications, however, toxicity remains a concern, limiting application and requiring extensive testing. Here, the authors report on a predictive framework made using a range of tests linking materials properties with toxicity, allowing the prediction of toxicity from physiochemical and biological properties.There is an urgent need to apply effective, data-driven approaches to reliably predict engineered nanomaterial (ENM) toxicity. Here we introduce a predictive computational framework based on the molecular and phenotypic effects of a large panel of ENMs across multiple in vitro and in vivo models. Our methodology allows for the grouping of ENMs based on multi-omics approaches combined with robust toxicity tests. Importantly, we identify mRNA-based toxicity markers and extensively replicate them in multiple independent datasets. We find that models based on combinations of omics-derived features and material intrinsic properties display significantly improved predictive accuracy as compared to physicochemical properties alone.Peer reviewe

Sediments Somewhat Alter the Decomposition of Leaf Litter in Small Man-made Ponds in Central Virginia.

Poster for the 2016 ASB meeting in Concord N

Implementation of the Longwood Environmental Observatory

Poster on LEO for SFS 201

Impacts of terrestrial leaf litter on the sediments of small man-made ponds in central VA

Talk at SFS 201

The connections between the small and the global: dynamics of small pond carbon cycling

<p>These are the slides from my Oct. 6 2014 Blackwell Seminar at Longwood University.</p

Leaf litter processing is primed by pond sediments

SFS 2017 presentatio

Functional diversity affects organic matter processing in the sediments of a shallow man-made pond

<p>These are the slides from my presentation at the 2013 annual meeting of the Society for Freshwater Science in Jacksonville, FL</p