Microbial release from seeded beach sediments during wave conditions

- Artificial seeded sand was successfully created to mimic attachment of bacteria to natural beach sand.
- A wave tank and shearing assay were developed to measure the release of bacteria from sand.
- Percentage released by waves was not different than bench top shearing assay.
- Maximum percentage of microbes released governed by factors other than agitation.
- Biofilms and adhesion of bacteria to sand grains are suspected to control release.

Beach sands can sustain indigenous and introduced populations of enterococci. The objective of this study was to evaluate wave action in promoting the release of introduced bacteria. To accomplish this objective this study developed a method to assess attachment and identified conditions under which introduced bacteria are integrated into the sand. A new “shearing assay” showed that attachment of the introduced spike mimicked that of the natural sand when the spike was allowed to integrate into the sand for 24 h at room temperature at a sand moisture content of 20%. Experiments in a wave flume showed that waves were capable of releasing about 60% of the total bacteria added. This suggests that for the range of wave conditions evaluated (height: 1.9-10.5 cm, period:1-2.7 s), waves were incapable of releasing all of the bacteria. Further study is needed to evaluate bacteria attachment mechanisms.