Everglades Geological Society

Upcoming Events

Next meeting and presentation

Tuesday, May 9th, 2017

FGCU, Marieb Hall 100

Seasonal erodibility and bioturbation of cohesive sediments in the

Caloosahatchee River estuary of southwestern Florida

By David Kluesner


5:30-6:00 PM         Social

6:00-6:30 PM         EGS Meeting

6:30-7:30 PM         Presentation


Pollutants and oil spills tend to concentrate in cohesive sediments in low energy depositional environments such as estuaries. It is important to understand the critical bed shear stress, erodibility, and effect of bioturbation on these sediments to provide a baseline and predictive tool for potential movement of pollutants and oil spills. 

The objective is to investigate seasonal variations in erodibility of cohesive sediments at a single site near Beautiful Island in the upper Caloosahatchee River estuary, Fort Myers, Florida. The investigation site is in a quiet area, sixty meters from the river bank, out of the main channel and current, and conducive to deposition of cohesive sediments. FGCU’s U-GEMS laboratory erosion chamber is used to evaluate critical bed shear stress, and erodibility of sediment cores retrieved over three consecutive dry winters, transitional spring, and wet fall seasons in 2013, 2014 and 2015. An additional objective is investigating seasonal variations in bioturbation, and its effect on erodibility through a placing, core, and counting of colored tracer grains redistributed by benthic fauna in the river bed.

Recovery of twenty-one cores with multiple cores per dry winter, transitional spring, and fall wet seasons assess erodibility and twenty-four cores bioturbation.  Seasonal variation in erodibility is evident, with more erodibility in dry winter and transitional spring seasons, less in wet fall seasons.  Bioturbation follows a similar seasonal pattern and may influence erodibility. Changes in cohesive clay, silt, and organic biomass are affecting erodibility, whereas changes in salinity and freshwater releases from Lake Okeechobee are reducing bioturbation and by inference benthic macrofauna. Increasing micro-algae and biofilms with higher nutrient loads from freshwater releases may also be suppressing erodibility.


After obtaining a BS in geology from Indiana University in 1977, David moved to Singapore with Core Laboratories International where he spent three years working offshore Malaysia, Brunei, and Japan as a well site geologist and petroleum engineer.  He joined Shell International Exploration and Production in 1981 and worked in Brunei, Malaysia, Nigeria, and The Netherlands as a petroleum geologist in various technical and leadership roles. He is a Certified Petroleum Geologist and an emeritus member of the American Association of Petroleum Geologists (AAPG). After retiring to Florida with his wife and family in 2010, he completed an MS in Environmental Science at Florida Gulf Coast University with thesis research on the seasonal erodibility and bioturbation of cohesive sediments in the Caloosahatchee River estuary of southwestern Florida. He occasionally teaches as an adjunct professor of geology at FGCU.