Category Archives: Coastal Waters Research

Islands in the Oil

The following is a summary of “Islands in the oil: Quantifying salt marsh shoreline erosion after the Deepwater Horizon oiling” written by R. Eugene Turner, Giovanna McClenachan and Andrew W. Tweel, published in the Marine Pollution Bulletin in September 2016 (Volume 110, Issue 1, 15 September 2016, Pages 316–323)


The 2010 Deepwater Horizon disaster was the worst oil spill event in U.S. history. Approximately 4.9 million barrels of Macondo oil were released into the Gulf of Mexico just 66km from the Louisiana coast. As clean up and restoration efforts began, it became clear that there was a severe lack of baseline data for the ecosystems and wildlife in the region. There has been a concerted effort over the past six years to monitor and record the short and long-term impacts of the spill in order to understand the extent to which oil affects an environment. Conveniently (from the scientific viewpoint), the marshes and islands of Louisiana were inconsistently oiled and provided a “potential natural laboratory” of control and experimental sites. Scientists could observe oiled and unoiled marshes that experienced the same natural tides, weather conditions, and human impacts over the same period of time. This type of experimental conditions are rare outside of a controlled laboratory situation.

Photo Credit: NOAA Office of Response and Restoration


Drs. Eugene Turner, Giovanna McClenachan and Andrew Tweel used this opportunity to monitor shoreline erosion – a key issue for Louisiana salt marshes. They had three primary questions: 1) How much faster did oiled shorelines retreat?, 2) How long do the effects of oiling last?, and 3) Is there recovery?.  Using Google Earth satellite and aerial imagery and classifications from a multi-agency damage assessment organization (SCAT – Shoreline Cleanup Assessment Technique), 46 islands in Barataria and Terrebonne Bays were selected as study sites. Islands classified as heavily, moderately or lightly oiled were used as ‘oiled sites’ while those given the no oil designation were used as ‘unoiled sites’. Imagery stored publically on Google Earth provided images of the selected sites from 1989 to 2012 and enabled the scientists to measure the length and width of each island over time. Using these images, they were able to determine the erosion rate for the 20 years prior to the oil spill and establish a baseline to compare with the erosion rate following the spill.

This figure was taken from the Supplemental Material of the referenced article (Turner, McClenachan, and Tweel, 2016)


After analyzing the data, the scientists determined that the rate of erosion at oiled islands for the first 12 months following the spill was 275% of the pre-spill erosion rate. That translates to an erosion rate nearly three times as fast as that seen before the spill and at unoiled sites. However, there was no detectable difference between the rates at oiled and unoiled sites after a year and a half. This suggests that there was some degree of recovery or stabilization over those 18 months. These results are consistent with those from other studies that tracked erosion rates after a shoreline was exposed to oil. Turner, McClenachan and Tweel stated that the resiliency and strength of the marsh sediment comes from the belowground biomass – the root system. Without the stability from the roots, sediment is easily washed away by the tides and regular wave action. This study demonstrated that the increased erosion rate caused by exposure to oil does slow over time but did not provide any evidence of recovery in affected marshes. Additionally, these scientists do not believe there can be a reversal to the damage without management intervention.

This is one of many studies examining Louisiana’s coastline and waterways. They are focused on a number of different issues pertaining to erosion, vegetation, food webs, soil, and microbial communities, but there are a few consistent messages emerging: a loss of habitat stability ripples through to all aspects of the community. Salt marshes and estuaries are vital nursery grounds for marine life that form the bedrock of Louisiana’s economy. The islands serve as resting spots and nesting grounds from local and migratory birds. In fact, 11 of the 30 Brown Pelican nesting sites along the Gulf are in Barataria and Terrebonne Bays. Without the islands and marshes, mainland Louisiana is at a higher risk for hurricane damage and sea level rise. They are essential habitats for the social and economic future of the state.

To read the full article:

Using GoPro cameras to monitor land loss

In order to collect data and answer scientific questions, scientists design and run experiments and conduct extensive fieldwork. These require planning, preparation, patience and a healthy dose of creativity. So what if you are trying to monitor the amount of land lost in a salt marsh over the course of a year? Does it require going out and physically measuring the marsh edge on a regular basis or could you capture the changes digitally? For the latter, you would need something reliable, tough and waterproof to stand up to the changing tides and the harsh weather conditions of a coastal salt marsh. CWC scientists Giovanna McClenachan and R. Eugene Turner, both of Louisiana State University’s Department of Oceanography and Coastal Science, tackled this challenge with every surfer, paddler and adventurer’s best friend – the GoPro®!

Scientists have been studying coastal marsh erosion (or land loss) in Louisiana and along the Gulf Coast for years because salt marshes are vital to local fisheries and tourism. Erosion of the marsh edges can occur naturally due to tidal and wave action but there is also evidence that human related activities and disturbances are causing the rate of erosion to increase in some locations.  McClenachan and Turner are specifically interested in how exposure to oil (like from the 2010 spill) effects the rate of erosion. They chose a study site in Bay Batiste in Plaquemines Parish, Louisiana to try out their GoPro camera setup and were able to capture photos at two-hour intervals during four to six-week periods from August 2014 to September 2015!

McClenachan and Turner attached two GoPro cameras to a PVC pole that was initially 1.5m from the marsh edge and aimed at a target pole. Additional poles were placed to the left and right of the study site to serve as reference markers in the pictures. The cameras, designed to function in any number of conditions, took photos throughout each day capturing the changing tides, passing storms and the gradual decrease in soil around the marsh grass roots. Using these images, the scientists saw that more sediment was lost during times when the roots of the marsh grass were dead. This happens naturally each year but can also occur when the marsh is exposed to oil and other pollutants. The marsh grass dies or their root systems are damaged and they can no longer serve as a stabilizer for the sediment. Moreover, since studies are showing that remnants of oil can remain in the sediment for years, scientists are worried about the long term impacts of the spill on the stability of marshland.


We don’t have all of McClenachan and Turner’s data, as they haven’t published this study yet, but it seems safe to make some general conclusions: 1) land loss is happening, 2) healthy grass and root systems help stabilize marsh sediment, 3) exposure to oil appears to increase the rate of land loss in marshes, and 4) there is a lot more research that needs to be done.

**McClenachan and Turner put together a time-lapse video to show the dramatic changes to this segment of marsh during the study period. Watch carefully and you will notice the additional poles added to mark the new marsh edge as sediment erodes away.**

The Myth of Science – – written by Leandra Darden

Researcher with marsh rice rat

If you ask students what a scientist does, they will tell you, it is someone who does experiments. If you then ask them how many experiments they are running at a time, they will generally tell you one. Most of the time students are picturing someone in a lab with a lab coat mixing chemicals, and shouting “EUREKA” when they come up with the answer to their question. Cartoons have conditioned kids to believe that science is done inside with chemicals, and beakers, and an assistant named Igor. We are here to debunk some of the myths.

Myth 1: Science is done inside.


That is not true at all. Did Charles Darwin study animals inside? Did Galileo study the stars inside? The answer is no. To understand the natural world, you have to conduct science outside in the heat, cold, with bugs, wind, and sometimes rain. Nature is a beautiful interconnected world, and you have to preform experiments in situ. This means in the actual environment to begin to comprehend the intricacies of patterns. That is why scientists will set up experiments outside. Scientists will build study sites, generally near each other so they experience similar situations during the study time, which will include at least one treatment and a control. Then they have to check progress to collect data. This can mean daily, weekly, monthly or yearly trips out to the study site. While this often the best way to understand exactly what is going on, it can be time consuming, costly, and sometimes hard to understand what factor might be influencing the focus of the experiment. To try and alleviate some of the parameters scientists will build mesocasms, small versions of the environment that they can manipulate to get better results. This allows the scientist to fine tune any differences between treatments and begin to understand how they are affecting the results.

Myth 2: Scientists run one experiment at a time.

When you talk to various scientists they will tell you that one of the reasons that they chose the profession is because they had a lot of questions. After you run an experiment, you will begin to see more questions actually arise from your experiments than those you answer. Scientists will have many different projects running that may overlap but are seeking to find different answers.

Myth 3: Scientists work alone or with one assistant.

While in college many people would tell me that they wanted to be a scientist because they would not have to deal with people. The reality is that scientists are NOT loners, they are in fact, team oriented. In order to answer the many questions, process the massive amounts of data and samples, and just plain keep things in order a scientist will be a part of a lab. This lab generally includes research assistants, a lab manager, undergraduate students, graduate students, and post-docs all working together and on separate projects. Are there days where you are so caught up in your job that you may not see anyone, yes, but for the most part you are going to be part of a well-oiled machine that helps to identify and answer life’s questions.

Myth 4: All scientists wear a lab coat.


This is true and not true. Most scientists do not wear a lab coat all the time and some do not wear one at all. Even in more biologically focused labs, chemicals may be necessary to process samples. A lab coat is not for show, it is to protect yourself and your clothing from anything harmful. A lot of the equipment being used needs to be kept at low temperatures so the lab coat has the added bonus of keeping you warm!

Myth 5: Scientists yell “Eureka” when they make a discovery.

It is fun to think that all scientists have that lightbulb moment and they remember to yell that iconic phrase…but the reality is not so. During a discovery you are more likely to hear a “FINALLY” or a “Hmmm, this is weird” or “I don’t understand what is happening” than anything else.


Hopefully we have successfully refuted some of the myths behind science!