Thursday, December 14, 2017

Impressive high school senior joins DROPPS lab to analyze bacterial compositions in the Gulf with sophisticated new equipment

Impressive high school senior joins DROPPS lab to analyze bacterial compositions in the Gulf with sophisticated new equipment                                                                  By Lalitha Asirvadam

High school senior Helen Schawe from Veterans Memorial High School in Corpus Christi, TX, is working on some exciting new research in Dr. Jian Sheng’s lab at Texas A&M University-Corpus Christi. Dr. Sheng is a Co-Principal Investigator in the Dispersion Research on Oil: Physics and Plankton Studies (DROPPS) consortia within the Gulf of Mexico Research Initiative. DROPPS is looking at how dispersants and wave action affected the breakup and fate of the oil and how it affected planktonic and bacterial communities during and after the Deep Water Horizon (DWH) Oil Spill. Helen joined Dr. Sheng’s team over the summer and continues to work on the project when she finds time after school and between swim practices. Helen has been working with different bacterial samples from the Deep Water Horizon site and other areas in the Gulf of Mexico in order to assess growth behavior and particulate formation with different bacterial compositions and oil/dispersant concentrations.
Dr. Sheng brought Helen onto the project as an intern in May to look at how dispersants influence bacterial growth and oil degradation. Along with postdoctoral researcher Andrew White, Helen works with six different samples where bacteria compositions may have been affected by the oil - one set from the DWH wellhead and from the water column above; one from the Louisiana Delta sediments and the water column above, and one from Port Aransas sediments and the water column above it. DROPPS researcher and UTMSI professor Zhanfei Liu profiled the samples.

Sample compositions consisted of oil alone, oil with dispersant, and dispersant alone. They are looking at how well bacteria grow in these different conditions and how these conditions affect particulate and bacterial aggregate formation.  Helen is also looking at rheological changes. Bacteria produce extracellular polymerica substances (EPS), which consist of proteins, carbohydrates, nucleic acids and other materials. Using a sophisticated Dynamic Shear Rheometer (DSR), they measure the effective viscosity increases and the viscoelasticity of the medium as the bacteria grow. She is also working with a spectrophotometer which is used daily to measure the optical density of the bacteria samples in order to chart their growth over time. Optical density is a measurement of how much light is absorbed by the bacteria and other particles in the culture. Helen also used a phase contrast microscope to assess bacterial morphology and motility. More recently, she has used a dynamic light scattering (DLS) analyzer to measure particle sizes in bacterial samples in order to assess the impact of dispersant on particulate size and formation.

Dr. Sheng is very excited about some of the preliminary findings. They found that with oil plus dispersant, much smaller particles (80-100 nanometers) were produced and the culture growth was much faster than cultures grown with crude oil only. Helen is cataloging the samples that show the spike in 80-100 nanometers, a unique finding since this not visible in traditional microscopes. Dr. Sheng says this finding is important since these kinds of observations are lacking. These are the “ingredients to promote marine snow”, he says, and since 20-30% of the oil from the BP Oil Spill is still unaccounted for, this could be an answer as to what happened to some of it. Marine snow is organic debris that falls from the upper water column to the deep ocean and can eventually land on the seafloor. These bacterial aggregates may be a perfect vehicle to transport oil down to the seafloor.

Helen submitted a poster detailing this research and will present it at the next Gulf of Mexico Oil Spill & Ecosystem Science Conference in February 2018 in New Orleans, Louisiana. She is graduating from Veteran’s Memorial High School in the spring of 2018 in the top 10% of her class. She has her sights set on Northwestern University, the University of Texas, the University of Pennsylvania, and Massachusetts Institute of Technology. She wishes to study mechanical engineering.

Wednesday, February 1, 2017

Student Presenter Award Winners

Student Presenter Award Winners
Supported by the Gulf Research Program of the National Academies
and the Gulf of Mexico University Research Collaborative
2017 Gulf of Mexico Oil Spill and Ecosystem Science Conference

Congrats DROPPS students! DROPPS had a number of students who received the “Student Presenter Award” for their upcoming presentations that will take place at the 2017 Gulf of Mexico Oil Spill and Ecosystem Science Conference. Below summaries of their presentations. Be sure to check out them out at the conference!

Shigan Chu
Johns Hopkins University
Department of Mechanical Engineering

Title:  Effects of bubble and drop dissolution on the plume dynamics in a stratified ambient ocean
The present study uses a horizontally integrated model to study the dynamics of oceanic plumes rising under the action of bubbles and drops injected at the ocean floor in a stratified ambient. Since the bubbles and drops are partly soluble, the plume density changes as they rise due to the addition of dissolved material. The project focuses on various factors affecting the plume dynamics and, in particular, the effect of dissolving hydrocarbons and their mixing with the plume water. It is found that this mixing has a very significant effect on the plume rise and the so-called peel height, namely the maximum height reached by the plume. A parametric study of the sensitivity of the plume to the size of bubbles and drops, to the rate at which they are injected at the base of the plume and to the ambient stratification is also conducted. It is found that the plume is very sensitive to many of these parameters, particularly when the ambient is weakly stratified. In practice, therefore, the plume evolution will depend on the specifics of the situation under which it is generated. For the same reason, it is very difficult to make quantitative predictions of general validity except in extreme cases.

Chi Hung “Charles” Tang
University of Texas Marine Science Institute

Title: Crude oil and dispersant impair the grazing impact of heterotrophic dinoflagellates on phytoplankton.
Microzooplankton grazing is very important when considering the loss of primary production in oceanic surface water. The influence of oil pollution on the grazing impact of heterotrophic dinoflagellates on phytoplankton was studied in the laboratory. Results showed that the grazing rate of the dinoflagellate Oxyhhris marina and growth rate of autotrophic dinoflagellate Isochrysis galbana were most severely impaired when exposed to a combination of crude oil and dispersant. Meanwhile, dispersant-alone treatment did not have any obvious negative effect on both grazers and prey.

Feng Gao
New Jersey Institute of Technology
Department of Civil and Environmental Engineering

Title: Hydrodynamics of Subsurface Oil Release without and with Dispersant:  An Experimental and Numerical Study
 Dispersant has been widely used to mitigate the impact of the Deepwater Horizon oil spill. Dispersants reduce the interfacial tension, allowing larger droplets to breakup into smaller droplets and disperse in water. Not much is known about how dispersants affects submerged oil jet. We conducted two underwater oil releases: one without dispersant and one with oil premixed with dispersant. A high resolution camera and Vectrino Profiler were used to measure the hydrodynamic properties of the jet.  In parallel, we numerically modeled oil jet (with/without dispersant) by Computational Fluid Dynamics (CFD). We find out that the temperature of pre-heated oil has negligible influence on the oil jet hydrodynamics and the spread angle of oil jet premixed with dispersant is closer to that of miscible jet, compared to pure oil jet. The turbulence dissipation rate is increased as dispersant facilitates the generation of smaller droplets. Other jet characteristics (e.g., jet profile, velocity, turbulent kinetic energy, etc.) are also compared and discussed.
By combining experimental measurement and CFD, the results show a robust method to evaluate the effect of dispersant and the hydrodynamics of underwater oil jet, which would provide valuable information for decision makers and researchers.
   (a)    (b)
The instantaneous jet profile of (a) pure crude oil (b) crude oil premixed with dispersant

Xinzhi Xue
Johns Hopkins University
Department of Mechanical Engineering

Title: Refractive Index-matched Turbulent Immiscible Buoyant Oil Jet Breakup in Water
This study is about near field oil jet/plume fragmentation. It is traditionally difficult to visualize and quantify this process due to the opaque plume and dense oil droplets, so an index matched experiment was designed to overcome the challenge. Silicone oil and sugar water solution pair is used to surrogate crude oil and seawater. During the experiment, they were able to maintain the same density, viscosity and interfacial tension ratio while having the two phases of fluid refractive index matched. The oil is fluorescently dyed and both phases are seeded with PIV particles. This enables the use of a plane laser sheet to dissect the near field jet/plume, having simultaneous results of oil water interface distribution and the entire flow field. Results demonstrated the jet entrain ambient water, deformed into long stretching ligaments and then breakup to droplets. The droplets often contain water or smaller oil droplets inside forming nesting, "Russian Doll" like phenomenon. While this alone is fascinating, this phenomenon actually indicates that the inertia and effective buoyancy would be quite different than those pure oil droplets of the same size; therefore, affected their consequent far field transport. PIV results show that the resulting droplets size correlates with initial shear stress and droplets size based buoyancy affects the plume spreading rate.

Cheng Li
Johns Hopkins University
Department of Mechanical Engineering

Title: Measurements of Droplet Size Distribution Generated by Breaking Waves Acting on an Oil Slick

The droplet size distributions generated by the impact of breaking waves on oil slicks are of fundamental importance to predictions of the fate of oil spills. An extensive series of experiments examine the physical mechanisms involved, and the time evolution of size distribution over several hours, starting from the initial breakup phase. Investigated parameters include wave energy, oil viscosity and density, as well as oil-seawater interfacial tension. The experiments are performed in a transparent wave tank, with waves ranging from spilling to plunging breakers. The oil properties are varied by using crude, fish, and motor oils, with viscosities in the 9.4-306.5 cSt range. Interfacial tensions varying from 0.28 to 19mN/m are achieved by premixing the oil with Corexit 9500A at dispersant to oil ratios of 0.0, 1:25, 1:100, and 1:500. The size distributions are measured in-situ using high speed digital holography at resolutions of 11.1 and 1.1μm/pixel. Collected samples are also examined microscopically. Results show that decreasing the interfacial tension increases the generation of 2-10μm droplets by orders of magnitude and steepens the slope of the number size distribution. For DOR 1:25, the volumetric size distribution already peaks around 10μm. Being smaller than turbulence scales, these droplets are generated by micro-threading. A fraction of them remains suspended well over a day, and submicron droplets persist for longer periods.  Droplets larger than 100μm are generated by turbulent shearing; hence, their initial concentration increases with wave energy. Within this range, the size distribution slope steepens rather abruptly at a certain size, which depends on oil properties and time. The transition occurs for crude at a diameter smaller than that of more viscous oils. Due to buoyancy, the concentration of large droplets decreases with time, while smaller droplets remain suspended. Trends are consistent with those expected based on the droplet rise velocity.

Tuesday, March 8, 2016

New DROPPS Researchers at the University of Texas Marine Science Institute
By Lalitha Asirvadam, DROPPS Program Coordinator

The New Year brings new talent to the Dispersion Research on Oil: Physics and Plankton Studies (DROPPS) consortia! Since last fall, DROPPS has added three new post-doctoral researchers and one PhD student to the team at the University of Texas Marine Science Institute (UTMSI). Maud Moison, Tatiana Severin, Charles Tang and Sarah Cosgrove are working with Dr. Ed Buskey and Dr. Deana Erdner on research involving various zooplankton and phytoplankton-bacteria interactions in relation to oil exposure. They each bring a wealth of diverse knowledge to our consortia. Read about their past experiences, research interests and what inspired them to work with DROPPS at UTMSI.

Maud Moison
 I was born and raised in France, in a small city by the sea in Brittany. After graduating from high school, I went to a two-year college in the south of Brittany and then transferred to the University of Rennes 1 where I obtained a B.S. in biology. After a short stint as a laboratory assistant in IFREMER in Brest, France, I moved back to the University IUEM for graduate school. I obtained my PhD in marine ecology from the University of Lille 1. I then moved to Germany, and later to Taiwan to continue my research work. I finally arrived at UTMSI as postdoctoral researcher in September 2015.
My research interests have focused on marine zooplankton behavior. I am particularly interested in small scale mechanisms that drive individual behavior change under both anthropogenic and climatic forces. For example, My PhD thesis provided a quantitative description of the seasonal change of copepod swimming activity, as well as evaluated the impact of different environmental factors on the copepod behavior.
My research also aims to analyze multiscale ecological responses of plankton communities to external forcing. Specifically, this part of my research involves using adequate methodologies to face the challenge of scale-dependent processes in plankton ecosystem, and the nonlinearity and non-stationarity of time series data.
Within the DROPPS consortium, I am going to study the sublethal effects of low concentrations of crude oil and dispersants on marine zooplankton. More specifically, my current research topics will try to answer to these questions: (1) Does the exposure to PAHs decrease the behavioral adaptations ability of zooplankton and then disturb their migration, feeding or mating activity? (2) Does the exposure to PAHs increase the vulnerability to other stress such UV? (3) What are the long term consequences (i.e. consequences over generations) of a short exposure to PAHs?
Working at UTMSI with Dr. Buskey gives me the opportunity to broaden my experience in individual animal behavior using state of the art optical techniques, while playing an active role in understanding and protecting the marine environment.

Tatiana Severin
I finished my PhD in 2015 at the Oceanological Observatory of  Banyuls-sur-mer, France. I worked on the impact of the convection process in the Northwestern Mediterranean Sea on the nutrient budget and the microbial compartment. The nutrient supply driven by the upwelled deep waters during one convection event revealed to be significantly higher than the annual rivers discharges of the Northwestern basin, and was able to sustain the entire spring bloom. Sequencing analyses of the 16S rRNA gene revealed that the bacterial community structure was deeply mixed in the convection cell, with the presence of both surface and deep OTUs from 0 to 1500 m depth. This mixed community persisted after the water column stratification and was entrapped in the new-formed deep waters.
To reinforce my specialization in the ecology of phytoplankton and prokaryotes, I came to UTMSI to work with Dr. Deana Erdner and Dr. Edward Buskey. In DROPPS-II, I aim to understand the impact of oil on the phytoplankton-bacteria interactions. After an oil spill, some phytoplankton species turned out to be resistant, while others were not. The strong interactions existing between bacteria and the host-phytoplankton could be at the origin of this resistance. During my researches in DROPPS-II, I will characterize these interactions and follow the physiological responses of some xenic and axenic phytoplankton strains after an oil exposition.

Chi Hung "Charles" Tang
I graduated from the Chinese University of Hong Kong (CUHK) as a marine ecologist.  I decided to pursue a research career in the field of marine plankton. I am impressed by the faculty team at UT Marine Science Institute, as it comprises many well-established research scientists in this field. Particularly, I am interested in the work of Dr. Edward Buskey. The first time I heard about Dr. Buskey was when I came across an article about the interaction between persisting brown-tide alga and planktonic grazers when I was in CUHK. Since my previous research experience is related to the grazing impact of micrograzers on algal blooms, I found the article very insightful. Later, I learned more about Dr. Buskey's work by reading his publications about the effects of dispersant-treated petroleum on marine plankton. I have become interested in how the treated oil affects planktonic organisms and animas up the trophic levels. Therefore, it is my pleasure to take part in the DROPPS research program as a doctoral student. I plan to investigate the effects of crude oil and dispersant on the eco-toxicology, adaptive behavior and population community of marine zooplankton and micrograzers.

Sarah Cosgrove
I completed my Marine Science degree at The National University of Ireland, Galway along the West Coast of Ireland during the period of 2006 - 2010. It was during my final year when I became increasingly interested in the smaller things in life i.e. plankton! My undergraduate thesis focused on the resting ‘cyst’ stage of dinoflagellate species in an archipelago region located north of Scotland known as the Shetland Isles.
My supervisor Dr. Robin Raine was an incredibly enthusiastic and supportive mentor and I ended up sticking around following the completion of my degree to work in his department as a research assistant. I continued to develop a passion for marine microbiology studies, especially within the area of Harmful Algal Blooms (HABs) and I became part of an on-going monitoring effort along the south coast of Ireland involving the saxitoxin producing species Alexandrium minutum. From here I gained funding for a three year PhD project where my primary objective was to take a closer look at the life history stages of A. minutum and at how both asexual and sexual reproductive phases can impact upon their population dynamics. A. minutum bloom initiation and termination were modeled based on observed variations in environmental parameters and sexual reproductive stages. Aside from the role physiological changes played in A. minutum cell behavior and population dynamics, an attempt was also made to determine the level of control parasitism exerted on the functional ecology of the population. It was after the completion of my PhD that the road to oil studies began. Following my thesis submission, I became employed as post-doctoral researcher as part of a European project called ‘Kill-Spill’. Involving over 30 organizations, the motive of ‘Kill-Spill’ is to develop environmentally and economically viable bio-technological tools to combat marine oil spills. My area of work focused on the eco-toxicology testing of bio-surfactants and plant-derived dispersants.
During the end of this research, I applied for the position of post-doctoral researcher with DROPPS-II and here I am! I’m delighted to be part of the team and under the supervision of Prof. Buskey. I have been following developments and research undertaken regarding the Deepwater Horizon oil spill since its occurrence and feel privileged to be contributing to on-going studies of such importance.
My research while at UTMSI is predominately aimed at utilizing mesocosm experimentation to analyze natural alterations in planktonic community structures following oil pollution events. As all planktonic groups are linked through complex direct and/or indirect interactions, it is important to focus on the long term impacts caused by oil pollution under a variety of environmental parameters. The physiological changes and recovery abilities of various protozoan and phytoplankton species will be assessed over time following the introduction of oil and dispersant to the controlled systems. As both of these groups play crucial roles in the tropic food chain, I will also aim to determine their level of contribution in the bio-transfer of Polycyclic Aromatic Hydrocarbons to higher tropic levels. Overall, the research intends to gain a greater understanding of the interactions between oil droplets and key planktonic organisms by means of mimicking the natural environment.

Wednesday, August 12, 2015

Research Experiences for Undergraduates (REU) Student Chris Payne Presents DROPPS Research

Every summer, the University of Texas Marine Science Institute (UTMSI) admits Research Experiences for Undergraduates (REU) interns to participate in exciting research, giving them valuable experience that will prepare them for careers in marine science. After choosing a research topic and mentors, they spend the summer working on their projects and give a final presentation at the REU Symposium at the end of the summer. 

Chris Payne, a marine biology major from Boston University, is one such student. He decided to work with DROPPS because he realized the value of studying oil spills and wanted to help be a part of the solution to this complicated problem.

There have been many studies on how oil affects macrofauna, but not as many studies on the impacts it has to the base of the marine food chain: plankton.  These tiny organisms are important for many reasons. Plankton are important contributors to primary and secondary production. Also, toxic species can cause harmful algal blooms when they are in large numbers. They also form important links in the marine food web, and finally, they provide organic matter to deep sea ecosystems through marine snow.

Research Questions
Chris Payne presents at the REUfest
2015 Summer Symposium
Credit: Lalitha Asirvadam
Chris’ research focused on these questions: What effect does oil and dispersant have on natural plankton populations? How do changes in oil and dispersant concentrations affect natural plankton communities? Chris worked closely with his mentors, Dr. Brad Gemmell and Dr. Ed Buskey from DROPPS, to try and find answers to these questions.

In preliminary experiments, Dr. Gemmell has looked at the dinoflagellate Prorocentrum and its ciliate grazers. He exposed them to oil and dispersants and observed changes in populations. His results indicated that dispersants inhibit ciliate growth which led to population increases in dinoflagellates. Chris wondered if similar results can be seen in natural plankton populations.

His study consisted of three experiments: two using nearshore water and one using offshore water. The water was filtered to remove large zooplankton. Each experiment used three treatments: filtered sea water, seawater with crude oil, and seawater with crude oil and dispersant. Both offshore and nearshore experiments were exposed to 20 µL Lˉ̄ ¹ of crude oil, while an additional treatment was conducted for nearshore water with 50 µL Lˉ̄ ¹ concentration of oil. A 20:1 ratio of crude oil to dispersant was used in all three experiments. For the nearshore experiments, 10 mL samples were taken daily and Chris counted diatoms, dinoflagellates, and ciliates using microscopy, FlowCAM, and flow cytometry. The offshore samples had to be settled in 50 mL settling chambers and were counted using microscopy.

For the 20 µL Lˉ̄ ¹ crude oil nearshore experiment, Chris found no significant differences among the total populations of the control, oil, and oil plus dispersant treatments. The 50 µL Lˉ̄ ¹ nearshore experiment, however, showed significant differences among the total populations of each treatment.

In summary, Chris observed that oil and dispersants have a negative effect on diatoms; however, dinoflagellates appear to be resistant to the toxicity of oil and dispersants. In addition, higher concentrations of oil have a more significant impact on plankton populations while offshore populations were more affected by 20 µL Lˉ̄ ¹ concentration of crude oil than the nearshore populations.  And finally, a population of small (approximately 2 micron) organisms becomes much more abundant in oil and oil + dispersant treatments. It may be that small nanoplankton (such as Synechococcus) are resistant to oil and dispersant.

Chris gave his final presentation on August 5, 2015. He said that he learned a lot and enjoyed his time as an REU student at UTMSI. He is currently thinking about a future in marine conservation.

Research sponsored by the Gulf of Mexico Research Initiative 

Wednesday, July 15, 2015

Oil and Plankton: DROPPS Takes a Closer Look Using Laser Technology

The interactions of plankton with oil droplets is a fascinating but relatively unexplored area. Scientists in the DROPPS Consortium previously looked at oil droplets rising though thin layer of plankton to see how they interact with oil. This time DROPPS wanted to look further into what may have happened in the dispersed oil layers between the well head, at approximately 5000 feet below sea level, and the ocean surface. DROPPS Scientists used holography technology, small scale experiments in the lab, and a recently constructed tower tank, measuring approximately 4 meters tall, for their latest experiments.

During the week of June 22nd 2015, DROPPS scientists Ed Buskey, Brad Gemmell, Jian Sheng, Joe Katz, David Murphy, Cheng Li, Larry David, Vincent d'Albignac and Jeffrey Cordero convened at the University of Texas Marine Science Institute (UTMSI) in Port Aransas, Texas to participate in the experiments.

DROPPS’ recent experiments involved holography technology which allows you to construct volume in 3D. This shows a 3D distribution of water and how it interacts with particles. DROPPS scientists were able to take a closer look at what could have happened to plumes of oil released from the Deepwater Horizon well head that had been mixed with dispersant. Studies showed dispersants created subsurface plumes of tiny oil droplets.  DROPPS recreated this in the laboratory by creating a layer of microscopic droplets (by adding dispersant to oil and mixing it up with seawater using stir plates), mimicking the subsurface layers associated with the Deepwater Horizon. They also created varying density layers in the water (by slightly changing the salinity), with the most dense water at the bottom, intermediate water in the middle, and lighter water at the top. They wanted to see how quickly oil would diffuse through these layers. Seawater density can change throughout the water column, with the most rapid changes often occurring near the bottom of the thermocline.  With the tower tank experiments, they set up layers to see how the micro oil droplets would disperse naturally, with and without small organisms swimming through it or with larger organisms stirring up the water.  This would help measure the importance of biogenic mixing (mixing of the ocean by animals), an idea that has recently been of great interest to biologists and oceanographers.

Small scale experiment in lab. Photo by Jeffery Cordero

First, DROPPS scientists conducted small scale experiments in the lab. In these experiments, they added small zooplankton, copepods mostly, and used PIV to examine how or if they mixed a layer of oil. The copepods did not seem to have much effect on the dispersion of the oil layer, probably because they were too small.  Tiny oil droplets have natural fluorescence so they glow when exposed to certain wavelengths of light. This allows DROPPS scientists to measure how well the animals mix the oil-water emulsion layer in comparison to natural diffusion.

A ctenophore suspended in water. Photo by Jeffery Cordero
 In the large tower tank experiment, they produced physical dispersion by using larger organisms (jellyfish), which had more of an effect on the layer containing dispersed oil.

Tower Tank. Photo by Jeffery Cordero

 In the future they hope to use intermediate sized organisms such as shrimp and small fish to examine their effects of biogenic mixing of dispersed oil. In the future, DROPPS scientists also wanted to study how these organisms interact with the dispersed oil layers; do copepods and other small zooplankton feed on the oil? Does this make them more susceptible to their predators (jellyfish and small fish)?

Video by Jeffery Cordero

Research sponsored by the Gulf of Mexico Research Initiative 

Wednesday, October 8, 2014

Hi everyone! My name is Colbi Gemmell and I am the Outreach Coordinator for DROPPS. I conduct outreach and educational activities related to our research such as: K-12 classroom visits, participation in local events, keeping up with social media, and coordinating news about our team members. I have also been organizing the DROPPS reading group which is comprised of ten DROPPS graduate students, post-docs, and staff members. Participants are from the University of Texas Marine Science Institute (Hernando Bacosa, Meredith Evans, Brad Gemmell, Colbi Gemmell, and Tracy Harvey), Johns Hopkins University (Cheng Li and David Murphy), Texas Tech University (Maryam Jalali-Mousavi), and the University of Pennsylvania (Tagbo Niepa and Liana Vaccari).

In December of 2013, the DROPPS reading group began as a monthly meeting where members got together to discuss papers relevant to the field of oil spill science. After a few of these meetings, the group determined that we wanted to do more than simply discuss the current literature. DROPPS Research Associate Dr. Brad Gemmell came up with the idea of conducting an extensive oil spill literature review with the goal of putting together a publishable manuscript on global, long-term trends. The idea was based on reading groups that he had previously been involved in. The group agreed that this was an exciting direction that allowed group members exposure to a large portion of oil spill literature across a wide variety of years and disciplines. The group worked together to develop a plan for obtaining, analyzing and completing such a large literature review. 

After determining the keywords to use, important questions to be addressed and doing several rounds of controls to ensure consistency, the DROPPS reading group started the official literature review. Each participant had to review a predetermined number of papers for assigned years to ensure that we were reviewing at least 10% of the available literature during each 5-year period dating back to 1968. Data collection took a total of six weeks and included the review of approximately 1100 papers. Currently, participants are in the process of analyzing the data in order to start putting together the manuscript. We are really excited to see what story our data tells. 

Reading group members discuss oil spill papers during a recent meeting. 
Research sponsored by the Gulf of Mexico Research Initiative 

Tuesday, September 23, 2014

Hi! My name is Sarah Horn and I’m an undergraduate Biology student at University Wisconsin-Milwaukee. I’m working with Professor Rudi Strickler at the Global Water Center. I was given the opportunity to work with DROPPS through the UW-Milwaukee’s Undergraduate Research Opportunity Program. I began working in the spring semester of 2014. 

Me feeding Daphnia an algae mixture.
I’m working on a project to observe how the freshwater zooplankton Daphnia pulex will react to oil droplets. Oil droplets of a set size are generated to simulate dispersed oil. Daphnia are placed in a Kreisel tank filled with oil droplets and algae. Water is pumped into the Kreisel tank creating a current along the edges of the tank, which keeps the Daphnia from getting too close to the edge. Daphnia behavior when surrounded by oil droplets is documented by taking a high speed video using laser holography. Using holography means that the Daphnia can be out of focus while it is being filmed, and reconstructed with imaging software later. This is necessary because of the Daphnia’s constant movement. After the video is taken, the size of oil droplets is measured to see if the Daphnia have attempted to eat the dispersed oil. Additionally, the behavior of Daphnia when surrounded by oil droplets is observed.

Kreisel tank
Freshwater zooplankton are used because they are easy for us to access. We get our zooplankton from the Menomonee River, Milwaukee River, Kinnickinnic River and Lake Michigan, all which are located less than a mile away from the lab. Once we obtain adequate results using the freshwater zooplanktona species of saltwater zooplankton will be used.