The Environmental Sample Processor (ESP), designed and built by MBARI, is an example of an in situ sensor for probing the microbes living within the ocean. This device can be deployed from a mooring, AUV, ROV, or ship. It detects the presence and abundance of organisms of interest by identifying part of their genetic code. The fact that a detection has been made can be relayed back to shore without the necessity of returning samples to shore. The first application of this device was the remote detection of the onset of harmful algal blooms, responsible for shellfish poisoning. Image courtesy of Davidson Seamount Exploration 2002, MBARI, NOAA/OER.