Spatial and temporal variability of bacterioplankton communities - PDF document

Spatial and temporal variability of bacterioplankton communities across a river to ocean gradient assessed with tag pyrosequencing Caroline Fortunato Bacterioplankton communities vary across a river to ocean gradient with estuaries as an intermediate environment where freshwater and marine bacteria mix. Spatial and temporal variability were assessed for bacterioplankton communities of the Columbia River, estuary, and coastal ocean using tag pyrosequencing of the 16S rRNA gene. 306 water samples, collected from the river, estuary, and coastal ocean in 2007-2008, were pyrosequenced. An additional 250 samples from 2009-2010 will be sequenced, totaling over 550 samples across four years. Analysis of 2007-2008 samples revealed bacterioplankton communities separated across salinity and depth gradients into seven groups: Columbia River, estuary, plume, epipelagic, mesopelagic, shelf bottom (depth<150 m), and slope bottom (depth>300 m). The great spatial variation of the dataset overwhelmed any seasonal trends as temporal variation was only observed within similar environment types. Community patterns will be compared to simultaneously collected environmental data to identify key environmental factors that strongly influence variability. Understanding why bacterioplankton communities change across a river to ocean gradient allows for better prediction of how these communities, and ecosystems as a whole, might be shaped by environmental change.

Another meadow bites the dust: Interactions between physical and biological processes during desertification of groundwater dependent semi-arid grasslands Kimberly R. Vest , Andrew J. Elmore, James M. Kaste, and Gregory S. Okin Desertification is a human induced global phenomenon causing a loss of biodiversity and ecosystem productivity. Semi-arid grasslands are vulnerable to anthropogenic impacts (i.e., groundwater pumping and surface water diversion) that decrease vegetation cover and increase bare soil area leading to a greater probability of soil erosion, potentially enhancing feedback processes associated with desertification. To enhance our understanding of interactions between anthropogenic, physical, and biological factors causing desertification, this study used a combination of modeling and field observations to examine the relationship between chronic groundwater pumping and vegetation cover change and its effects on soil erosion and stability. The work was conducted in Owens Valley California, where a long history of groundwater pumping and surface water diversion has lead to documented vegetation changes. To understand the mechanisms that drive desertification, we looked at ecological, hydrological, and aeolian factors at thirteen sites across Owens Valley in groundwater pumped areas and control sites (not pumped areas) over three years. At each of the thirteen sites, we analyzed vegetation and gap size along vegetation transects and installed Big Spring Number Eight (BSNE) catchers (up to four heights above the ground surface) to collect aeolian sediments and calculate mass transport from May to September. Desertification in this system is apparently easily initiated through groundwater decline due to the high friability of these meadow soils.

A Spatially-Explicit Age-Structured Model for Identifying Areas of High Larval Sea Lamprey Density In a Large River. Jason Robinson & Michael Wilberg The St. Marys River is the largest contributor of sea lampreys ( Petromyzon marinus ) to Lake Huron and presents a unique challenge to sea lamprey control due to its size. A portion of the sea lamprey control program focuses on controlling the larval life stage through the application of Bayluscide. The goal of these treatments is to reduce sea lamprey induced mortality on other fish species. The St. Marys River has been divided into 71 plots for the purposes of lamprey assessment and control. Decisions about which plots to treat are currently based on only the most recent year’s data, although 18 years of plot-level data are available. Sampling and treatments are conducted on a plot by plot basis, but resources are not available to adequately sample or treat all plots each year. We developed a spatially-explicit age-structured modeling approach that estimated abundance in each plot over time. The model incorporated the full 18-year data set to predict areas of high larval lamprey abundance in the river. Recruitment in each plot was based on adult spawner abundance and a Ricker stock-recruitment model. The parameters of the stock-recruitment relationship and the proportion of recruits that settled in each plot were estimated within the model. Larval mortality was a function of estimated natural mortality and treatment mortality. The probability of a larvae metamorphosing to the transformer life stage was assumed to be zero for ages 1-3, and 0.46, 0.57, and 1.0, for ages 4-6. The model indicated that larval abundance and transformer production were decreased significantly through Bayluscide treatments and that chemical treatments have been an important component of the sea lamprey control program. Model projections of larval abundance corresponded well with observed data. This work will help to refine sampling techniques and provide more accurate assessments of larval sea lamprey abundance leading to more effective and efficient control.

A PCR-based assay for detection of Hematodinium sp. in sediment and water from the Maryland and Virgina Coastal Bays Dyson WE * , Schott E † , Hanif A † , and Pitula JS* *University of Maryland Eastern Shore, Department of Natural Sciences, Backbone Rd., Princess Anne, MD 21853 wedyson@umes.edu † UMCES-Institute of Marine and Environmental Technology, Baltimore, MD 21202 Hematodinium sp. is a parasitic dinoflagellate that infects the blue crab Callinectes sapidus and other crustaceans of economic importance. Using real-time PCR based methodology, we can now detect Hematodinium parasites in various crab tissues down to as little as 10 parasites per sampled tissue. This method will enable us to understand infection progress through the parasitic life cycle. One important question that remains is to understand the mode of initial parasite infection. Crab-to-crab direct transmission has been posited as one likely route. We also sought to discover a potential environmental reservoir through analysis of various ecological sites within MD and VA Coastal Bays, as transmission through dinospores has been posited as one potential mode of transmission. Sediment samples were collected and analyzed using primers that are specific to the Internal Transcribe Spacer region of Hematodinium sp. We report here the discovery of Hematodinium DNA in sediment from the junction between northern Chincoteague Bay and southern Assateague. This Q-PCR result was confirmed through direct cloning of a PCR fragment and comparison with genomic sequence deposited within Genbank. Ongoing studies will seek to confirm this result, and to further understand the biological and environmental factors related to this potential “hot spot” for a putative mode of disease transmission.

Taurine - the missing ingredient for fishmeal free diets for aquaculture? Aaron M. Watson Increasing pressure on wild fish populations has led to a rapid increase in the necessity and potential for intensive aquaculture. However, the production of fishmeal to fuel the growing needs of aquaculture from wild caught fish does not help solve the problems of over-fishing, fishing down the food-chain, or PCB and heavy metal accumulation. Alternate protein and lipid sources need to be explored for potential aquaculture diets in order to meet the demands of a “greener” and more sustainable industry. Limited research has been performed on a number of species to explore the possibilities of complete fishmeal replacement. Plant proteins have been identified as a renewable source of protein that may be potentially useful in fishmeal replacement. Utilizing several species housed at IMET, plant proteins have been used to successfully replace 100% of the fishmeal in diets for marine carnivorous fish. During the course of these trials taurine, a non-protein amino acid, was identified as a critical component of fishmeal that is lacking in plant protein sources. The roles of taurine include photoreceptor protection, osmolyte, antioxidant, feed attractant, and as a bile salt conjugate. There is a taurine biosynthesis pathway in vertebrates, however it appears to be defunct in marine carnivores, thereby necessitating taurine's acquisition through dietary consumption. So far our work has been conducted in an effort to establish taurine as an essential amino acid for marine carnivores, as well as identifying the requirement level for several species and determining where in the biosynthetic pathway the breakdown has occurred.