STUDYING THE GEOLOGY OF BERMUDA, FROM FORAMS TO SUB-SURFACE HYDROCARBON MIGRATION

Two undergraduate research projects undertaken on Bermuda have recently been completed in the Department of Geology at Colby College. The first focused on the environmental parameters influencing the distribution of the dominant benthic foraminiferal taxa in Harrington Sound via statistical analyses. The second studied the migration of hydrocarbon residue from a roadside soakaway through adjacent surficial sediment.

Ekman dredge sampling was initiated from a boat in the first project. Nine bottom sediment samples from varying depths were collected in the southern half of the Harrington Sound in January, 2018. Additional water chemistry samples were collected in June, 2018 and January, 2019 to determine seasonal variations in temperature, dissolved oxygen, salinity, and pH, at the original sites, at cave entrances for salinity variation, and at various tidal levels. The bottom samples were analyzed to determine the dominant benthic foram genera abundance and distribution. Grain counts of 100 were made on each sample and statistical analyses conducted. In testing multivariate response and factorial influence, initial relative effect estimations and subset algorithms for nonparametric MANOVA effectively quantified abundance patterns and indicated salinity, depth, and temperature as most influential.

Sampling for the second study began by obtaining 4 samples from each of the nine 0.9m deep test pits. The sample sites were laid out in a triangular pattern widening from the soakaway to determine the extent of contamination. Samples were analyzed to determine the distribution of polycyclic aromatic hydrocarbons (PAH) and heavy metals generated by the combustion of vehicles on Bermuda. Produced on Bermuda since the late 1940’s, it has only recently been realized to cause abnormalities and growth defects in the native and endemic amphibian and fish populations. This site is in close proximity to the Warwick freshwater lens and Warwick Pond, an important wetland in the avian migratory flyway. Trace metal concentration was determined by use of an inductively coupled plasma optical emissions spectrometer. Results from PAH analyses are pending. Heavy metal concentration increases with depth and proximity to the soakaway, indicating vehicular combustion is the source.