Liz Collazo, University of Puerto Rico Humacao

Class Year:

2024

Mentor:

Sairah Malkin, Ph.D.

Abstract:

Cable bacteria are long filamentous sediment-associated microbes capable of electron transport along their filaments from sulfide to oxygen. Their activity is often responsible for a majority of the oxygen consumption and sulfide depletion in sediments. They may also serve as electron acceptors, where oxygen is not available, potentially stimulating the activity of other beneficial microbes in the sediment environment. A previous experiment suggested there may be enhanced activity of cable bacteria following an experimental cutting treatment. However, this was not observed directly. A stimulation of activity could occur if a cutting treatment stimulated cable bacteria to migrate upward in the sediment, to re-connect with oxygen. Here, using pH and electric potential (EP) microsensors, I assessed the activity of cable bacteria before and after manipulating the sediment to directly observe if cable bacteria activity may be stimulated by a cutting treatment. To a subset of sediment cores, I performed a cutting treatment by passing a fishing line horizontally through the sediment, and I left control sediment cores intact. Unexpectedly, I found that moving the sediment prior to our targeted experimental treatment inhibited the activity of the cable bacteria, and counter to my hypothesis, that the cutting treatment did not detectably influence the activity of cable bacteria. I suggest several improvements that should be considered for future experiments, including reducing salinity gradients between the overlying water and the sediments, and setting up the sediment initially with an extra piece of acrylic core liner already in place to minimize pre-treatment manipulations.

Location:

Horn Point Laboratory