The CTD

     The CTD device takes water samples at different depths. CTD stands for conductivity, temperature and depth.  Other measurements can be taken if additional sensors are added for things like oxygen level, salinity, pH or chlorophyll.  From the computer station inside the ship, scientists monitor the water that is passing through the CTD as it is lowered into the depths. They can find out what layers of water have the most chlorophyll, whether there is an oxygen  minimum zone or other needed data. These layers are then targeted as water collection points when the CTD is brought back up to the surface.  The CTD has a number of bottles that are deployed open.  This allows water to pass continuously through the bottles as it is moving in the water column.  At specific depths the scientist instructs the device to close one or two bottles to collect the water.   The scientist running the CTD can communicate with the crewman running the winch and the device can be raised or lowered to the desired depth. Typically the CTD is sent down to 1500 meters.  Data are collected from a station at least two different times, once in the daytime around 6 am and once at night around 6 pm.

     The CTD

     In addition to the abiotic factors studied through the water collection, information can also be determined about biotic factors. One of the scientists, Dr. Cole Easson is studying microbes from the different layers of ocean water.  He filters the water from the different layers and extracts the microbes onto a filter.  The filters are taken back to the lab at home where he sequences the DNA of the microbes. A single sample can contain over 7,000 unique microbes.  From the first two DEEPEND research cruises he generated 33.5 million sequences. 

Dr. Cole Easson

Another scientist Travis Richards, is filtering water samples to collect data on primary production.   This allows him to establish what is the base of the food web and correlate this information to his study of stable isotope analysis with fish.  This allows him to predict at what trophic level each animal is located in the food web. 

Filtering water from the CTD