The Curious Case of the Bonnet Carré Spillway

This week, like last, I have focused on completing some small projects while the lab is in its last calm before we begin preparing for the fall semester and upcoming events. We have so many exciting events, including a conference in San Antonio, a welcome event for our new students, welcoming our own new student to the lab, and then the Community Day at the lab in mid-October. This week I have also been searching for additional data for my own research--hence the title of this week's blog--and I will continue my research project next week after making what I think might be a breakthrough. However, like all good mysteries, I'm going to start off by setting the scene and explaining what has lead to this point in the investigation.

As I have explained in a previous blog, the Bonnet Carré Spillway is a flood control structure built in response to the Great Mississippi Flood of 1927 that diverts excess Mississippi River water to Lake Pontchartrain and out to the Mississippi Sound. The U.S. Army Corps of Engineers operates the Spillway to prevent the flooding of New Orleans, but because the freshwater enters the Mississippi Sound it alters the water temperature, salinity, dissolved oxygen concentration, and other environmental factors that can create more or less habitable environments for marine organisms in the area. The Mississippi Department of Marine Resources (MDMR) Shellfish Bureau has been monitoring the health of the oyster reefs in Mississippi Sound for a few decades, with monitoring really ramping up in response to the Deep Water Horizon event. Since 2011, most of the oyster monitoring data have been made publicly available and easy to access because of the NOAA Natural Resource Damage Assessment DIVER--an online database of restoration and management projects after disasters. 

Before I started working at USM, Kim--my boss--requested a lot of data from different states for our modeling work, and among these data were oyster counts and environmental data. I have been using the Mississippi oyster data to understand what environmental factors have contributed to the oyster mortality in the Mississippi Sound and to compare the local mortalities to oyster mortalities across North America. For this project, I am using statistical modeling to understand how the response variable--oyster mortality--changes because of predictor variables--environmental variables. Additionally, because the Bonnet Carré Spillway openings uniquely contribute to oyster health in this area, I also need to consider the effects of infrequent openings on the mortality rates. In 2019, the Spillway was opened twice, which reportedly caused 100% mortality of oysters in the Mississippi Sound. Unfortunately, the data I have from the MDMR Shellfish Bureau is quite sparse for 2019, and I only have a few measurements at the middle-to-end of the second opening, which seems odd considering the novelty of this disaster. However, I have seen, in multiple places, data or figures showing information about oyster mortality or numbers of oysters throughout the openings. Hence, the mystery I've been trying to solve. 

It turns out that data were collected on oyster reefs every week of the 2019 Spillway openings but they likely were organized or characterized in a unique way which meant Kim's initial data request didn't lead the MDMR team to the 2019 data. I reached out to the MDMR team through a public records request and today I was informed that they have the records ready. I am really excited to finally get these data, even though I'm not sure what I will find. I'm hoping to get detailed numbers with environmental variable measurements, which have been standard for the other MDMR data sets, as my model requires complete environmental data to explain variability in the mortality values. I will need to send in payment and then get the files digitally, but I'm hoping that by next week's blog I may have the numbers and can provide more information.

Stay tuned!