Graduate Research Symposium 2017 Presentation Topics

Session 1: Critters, Creatures, and the Law

Session Chaired by Dante Torio, Postdoctoral Researcher

Wilton Burns research aboard ship.

Wilton Burns, MS, Earth Sciences

Effects of small-scale turbulence on phytoplankton growth and metabolism.
Our current understanding of how turbulence affects small planktonic organisms is based on fluid dynamic theory, ocean models, and laboratory experiments that often have conflicting results. Atmospheric models predict that global temperature rise associated with climate change will affect turbulence patterns within the marine photic zone, where phytoplankton reside. To investigate how small-scale turbulence affects growth (growth rates, cell counts and extracted chlorophyll, and nutrient quotas) and metabolism (production of transparent exopolymer particles (TEP)) of marine primary producers, phytoplankton in monoculture and natural assemblages were incubated under a range of turbulent treatments. Results indicate that early in exponential growth of the monocultures, cell-specific TEP was higher with increased turbulence. During mid- and late exponential growth, there were no measurable differences in phytoplankton growth and TEP production as a function of turbulence. However, nutrient quotas were higher in the more turbulent tanks in phytoplankton cells >15 µm in length. Data from this study suggest that changes in turbulence in marine photic zones could result in increased nutrient storage in larger phytoplankton cells, as predicted by numerical models, but may not greatly affect the global carbon cycle via changes in TEP production.

Oysters.

Meghan Hartwick, PhD candidate, Molecular, Cellular, and Biomedical Sciences

Estimating Seasonal Variation of Vibrio parahaemolyticus concentrations in Oysters from the Great Bay Estuary

Horseshoe crab.

Meghan Owings, MS, Biological Sciences

Effects of the biomedical bleeding process on the behavior and physiology of the American horseshoe crab, Limulus polyphemus.
The hemolymph from the American horseshoe crab, Limulus polyphemus, is used to produce Limulus Amebocyte Lysate (LAL), which is used to test medical devices and vaccines for Gram-negative bacteria. This process has a 10-30% mortality rate, as well as several sublethal impacts. The goals of this study were to: 1) investigate the effects of the bleeding procedure on the behavior of horseshoe crabs in their natural environment and; 2) determine which bleeding process stressors (blood loss, air exposure, or increased temperature) have the most deleterious effects. For the field study, 14 control and 14 bled animals were fitted with ultrasonic transmitters and released into the Great Bay Estuary, and their depth preferences and locomotor activity were recorded from May-December of 2016. Lab experiments were conducted in outdoor tanks where animals were exposed to combinations of stressors. Accelerometers were attached to 64 animals to measure activity; and blood samples were repeatedly drawn to monitor hemocyanin levels. The telemetry study showed that control and bled animals exhibited similar activity patterns and seasonal migrations with females being slightly more impacted by the bleeding process in the first few weeks after they were released. In the lab, hemocyanin concentrations and activity were significantly impacted by different combinations of stressors, but not individual stressors. We hope that when this study is completed, the findings can be utilized to more sustainably bleed horseshoe crabs.

Lindsey Williams performing field work.

Lindsey Williams, PhD candidate, Natural Resources & Earth Systems Sciences

Information needs of coastal decision-makers and resource users: an exploration of information flow, timescale, and systems perspectives
Despite increasing calls to connect science with decision-makers, challenges remain in facilitating the flow of information across sectors.  In some cases, these challenges stem from lack of resources or other capacity limitations, in others from a fundamental lack for awareness of what information is most needed by decision makers and how information flows between groups.  In this study, we focus on the information needs and sources as reported by business and government decision makers in coastal New England.  Through analysis of semi-structured interviews, we focus on what types of information needs are identified and what sources of information business and government decision-makers rely on for their jobs.  Within these sectors, we also explore 1) the timescale of the information needs as context for understanding how the different sectors conceptualize the challenges they face, and 2) the systems scale as context for understanding conceptualization of the system within which they operate. If we are to meet the calls for management relevant science and science based decision-making, understanding these factors of information flow will be a key component.

Kaitlin Von Volkom, MS, Biological Sciences

Effects of introduced tunicates on the growth and reproduction of the blood star Henricia sanguinolenta

Session 2: Got Gas? And other urgent ocean questions

Session Chaired by Kerri Seger, Postdoctoral Researcher

Oil flume.

Melissa Gloekler, MS

Movement and Erosion of Alberta Bitumen along the Bottom as a Function of Temperature, Water Velocity and Salinity
While many trajectory models exist to predict the movement of oil floating in or on water, few are designed to address heavy oil on the bottom of water bodies. In addition, remobilization (erosion) of the material into the water column is also difficult to predict. While properties such as adhesion, viscosity and density of oil may be readily measured, the critical shear stress (CSS) and the effect of (current) velocity, salinity, and temperature are virtually unknown for most heavy oils. The Center for Spills and Environmental Hazards (CSE) has a 4,000 L annular flume, with a water depth of 0.43 m. An inner rectangular flume (1.2 m length, 0.2m width, 0.9 m height), placed inside the annular flume, was preceded by two flow straighteners to reduced turbulence and produce a uniform, one dimensional flow field. The current is generated by an electric thrust motor and measured in 3D by a Nortek AS (Norway) Vectrino II Profiling Velocimeter. A 20g circle of Alberta bitumen (SG = 0.998) was placed on a laminated grid (1cm2 square pattern) at the bottom of the straight flume. A total of 2.3m3 of water was then gradually added to the flume. The electric motor was started and the profiler began collecting data. Two cameras, placed along the side and above the oil, collected video of the erosions and length/width changes of the oil. Conditions were held steady for one hour once the desired current velocity was achieved. Temperatures, current velocity (X, Y, Z), and digital videographic data were collected during each run. Erosions and percent lengthening of the oil was monitored as a function of water temperature, salinity and velocity. The turbulent kinetic energy (TKE) method was used to calculate the bed shear stress (BSS). In addition to the expected impact of higher temperature on the movement along the bed and erosion into the water column, the viscoelastic and shear-thinning properties of the bitumen played a role in its behavior (lowering of viscosity at higher BSS slowing erosions and movement) and must be considered when predicting its behavior during a spill.

Map of mud fraction in Little Bay.

Joshua Humberston, PhD candidate, Earth Sciences

Estimating surficial seafloor mud fraction in the tidally dominated Little Bay using principal component analysis of acoustic backscatter envelope properties
Field observations from an Odom Echotrac vertical-incidence 200 kHz echosounder were used to estimate seafloor mud fraction (fractional sediment size distribution less than 62.5 mm) in a tidally-dominated estuary with sediment distribution ranging 0–78% mud. Observations were obtained in water depths ranging 0.5–24 m in the Little Bay, New Hampshire. Backscatter waveform envelopes associated with the first acoustic interaction with the seafloor were analyzed and defined by seven properties: maximum and mean intensity, waveform width, area, skewness, kurtosis, and leading edge rise time. The spatial variability in these properties were decomposed into orthogonal eigenvectors using standard principle component analysis. The spatial weighting of the first principal component (representing 95% of the variance) was compared to observed surficial mud fraction. A simple logarithmic curve fit to the data accounted for 41% of the variability and well estimated (13% RMS error) the spatial pattern of mud across the bay from deep channels (no mud) to the flats (high mud content). The calibrated logarithmic function is used to estimate mud fraction spanning the estuary. Systematic deviations from the model are associated with regions with lower sediment porosity. When these anomalous data are removed from the analysis, the logarithmic model accounts for 62% of the variance. Application of the model along two cross-estuary transects in the Great Bay (independent from model development) resulted in similar RMS errors (15%) in predicted mud fraction showing that the empirical model works well for the Great Bay region provided the same sonar and settings are used.

Ocean acidification in coastal waters.

Christopher Hunt, PhD candidate, Natural Resources & Earth Systems Sciences

Coastal Alkalinity: What we know (and don’t know) about neutralizing Ocean Acidification
Ocean Acidification (OA) is a complex problem in coastal waters, affecting a variety of stakeholder groups (commercial, environmental, governmental) across a wide range of spatial and temporal scales. Assessing and projecting OA impacts is difficult given the contributions of several processes, a lack of recent historical baseline data in many areas, and the dynamic nature of the coastal environment. Alkalinity is the ocean's primary buffer against climate-driven acidification.  While the alkalinity of the ocean has long been studied, the variability of alkalinity in the coastal zone and the processes affecting alkalinity have received less attention.  However, new technological advancements coupled with improved understanding of the chemistry of alkaline species may offer new insights into buffering against OA.  Researchers in the UNH Ocean Process Analysis Laboratory are currently conducting two projects examining coastal alkalinity across a variety of settings.  This presentation will discuss the state of knowledge regarding coastal alkalinity, outline the approach of each OPAL project, present new data and maps, and synthesize how these projects will advance our understanding of coastal alkalinity and acidification.

Kara Koetje performing field research

Kara Kotje, MS, Ocean Engineering

Boundary Layer Dynamics in the Great Bay: Working Towards Resolving Estuarine Nutrient Fluxes
Quantifying the coupled physical and geochemical processes in the fluid-sediment interface is critical to managing coastal resources. This is of particular importance during times of enhanced hydrodynamic forcing where extreme tide or wind events can have a significant impact on water quality. A combination of field and laboratory experiments were used to examine the relationship between large-scale fluid shear stresses and geochemical fluxes at the fluid-sediment interface in the Great Bay Estuary, New Hampshire. Sediment geochemical measurements paired with flow field observations over several tidal cycles provide nutrient load estimates for the Bay. Sampling during typical tidal flow conditions along estuary-wide transects, an unexpected rotational flow field in the near-bed region of the water column was observed, which could have significant impact on the resultant nutrient release and nutrient budget estimates.

Elizabeth Weidner aboard a research vessel.

Elizabeth Weidner, MS, Earth Sciences

Estimation of Marine Seep Flux on the East Siberian Arctic Shelf
An estimated 1400 gigatons of methane are held in subsea reservoirs on the shallow (<50 m average depth) Eastern Siberian Arctic Shelf (ESAS). Marine gas seeps and high methane concentrations in surface waters indicate these reservoirs are releasing methane via ebullition. Bubbles ebullated from the ESAS seafloor have a relatively short pathway through the water column and can facilitate the transport of methane directly to the atmosphere without oxidation. Methane seeps were mapped with a calibrated broadband split-beam echosounder on the ESAS in order to directly and quantitatively address the magnitude of methane flux and the fate of rising bubbles. Acoustic measurements were made over a broad range of frequencies (16 to 29 kHz), which allowed for very high range resolution and the identification of single bubbles in the water column. Seep bubble size distribution (BSD) were determined by exploiting bubble target strength models over the broad range of frequencies. By coupling BSD with bubble rise velocity measurements, made possible by split-beam target tracking, gas flux can be estimated.