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As climate change continues to alter weather patterns and amplify the intensity of extreme storm events, the unique and wide-ranging effects on coastal deltaic ecosystems must not be overlooked. This study explores the effects of Hurricane Ida, a category four cyclone that made landfall at Port Fourchon on August 26th, 2021, and its effects on sediment distribution and nutrient cycling in Mississippi Delta topset sediment. Nearshore multi-core sediment samples (0 to 65 centimeters depth) from the top of the seabed were collected at several offshore locations from the proximal coast zone 11 days before the hurricane impacted the region. The locations were again sampled in December 2021, March 2022, June 2022, and August 2022, providing an invaluable opportunity to study the disturbance and recovery of the seabed and its impacts on the local biogeochemical cycles. This study focused on grain size analysis, where distributions of particle sizes could be compared across locations and dates. Change in sediment composition in the year following the hurricane can be used to gain insight on the disturbance to nutrient cycling as a result of Hurricane Ida. Significant recycling of organic and inorganic nutrients occurs between the seabed and the water column, becoming available for use by diatoms and detritivores that help regulate nutrient cycles. Sediment distributions of 170 samples were analyzed using a Mastersizer-3000, a device capable of measuring particles as small as ten nanometers in diameter. Sediment was broken down into individual particles and suspended, after organic material and plastics were carefully removed. Smaller particles including clay and fine silt decreased all the cores following Hurricane Ida, while larger particles such as sand appeared to be more varied at different depths in the seabed. A small increase in finer particle buildup in March and June at one particular location suggested steady deposition following the storm. Between June and August of 2022, there was a spike in smaller particles whereas the sand distribution matched the pre-hurricane distribution more closely. A possible explanation is rapid sediment deposition from the Mississippi River. With the fishing industry in this region generating over half a trillion dollars annually, it is increasingly important for high resolution sampling campaigns to be conducted, as the impacts of climate change continue to develop.
Undergraduate student Geosciences, CU Boulder