A day in the lives of the Oceanography Team

By Danny Merritt

Day 1 of operations at French Frigate Shoals was a good example of a typical day for the oceanography team, which is to say, there is no typical day. Unlike most of the teams on RAMP cruises which have very specific tasks to perform every day, the oceanography team performs a range of activities that are ever changing. In fact, “Oceanography Team” is a bit of a misnomer, starting with the makeup of the team itself.

Russell Reardon and Danny Merritt in the Oceanography Team launch “Rubber Duck” (photo by Frank Mancini)

The only true oceanographer on the team is Jamie Gove who earned his M.S. degree in Physical Oceanography and is currently working on his Ph.D. in Biological Oceanography. Frank Mancini has spent his life around the water from New Jersey to Palau working on a multitude of projects. He is currently CRED’s oceanographic data manager. Russell Reardon works his day job as part of CRED’s marine debris program and facilities logistics. I’m an ocean engineer and tend to work with all of CRED’s programs.

The team started the day by replacing a sea surface temperature buoy (SST buoy). One of the unique tasks that the oceanography team performs are called “Working Dives.” SCUBA diving safety rules are set by the Occupational Safety and Health Agency (OSHA). Several decades ago, both recreational and scientific diving agencies successfully lobbied the government to get exemptions to several of the OSHA rules. Nearly all of CRED’s diving falls under these scientific exemptions allowing us to dive using Nitrox and dive without surface diving support. For a few of our dives, however, mostly involving heavy weights or power equipment, the OSHA rules still apply. The 250 lb SST buoy anchors require us to follow these rules. To meet the requirements, we enlisted the help of chief scientist Peter Vroom and Cristi Richards to act as our topside safety divers, making our little 19’ boat feel more cramped than usual.

Frank Mancini and Jamison Gove performing a lift bag operation of a 250lb SST anchor (photo by Danny Merritt)

The SST buoys are tethered to this 250lb anchor. The anchors are lifted and dropped using lift bags. By filling these bags with air, enough water is displaced to lift heavy objects. Air compresses and expands at different depths, however, so the diver controlling the weight is constantly having to adjust the buoyancy of the bag by adding air or releasing it.

These buoys are able to telemeter temperature data to our computers back in Honolulu via satellite 6 times a day in near real-time. This allows us to remotely monitor SST throughout the year. The data also help scientists to ground-truth satellite derived temperature data which tends to measure temperature over broad areas and has trouble collecting data through clouds and near land. Water near land or reefs is much more dynamic than in open-ocean water and therefore satellite derived temperatures do not always match what is happening near the reefs.

Next, the team deployed and recovered a subsurface temperature recorder (STR). We place these temperature sensors at multiple locations to monitor temperatures on the reefs every 30 minutes for the entire 2 year period between visits to islands and atolls. Temperature is a relatively easy and inexpensive parameter to measure over a long period of time, but it can tell us a lot about the physical oceanography that the reefs are experiencing. CRED’s temperature sensors are also very precise and accurate instruments that will allow us to insure that any changes we measure over time are associated with long-term environmental changes and not due to errors in the instrument itself.

Jamie Gove installing a STR (photo by Danny Merritt)

For the final dive of the day, we installed calcification acidification units (CAUs), collected water samples, and took a shallow conductivity-temperature-depth (CTD) cast. CTD casts are one of the main tools oceanographers have been using to study the ocean for decades. Most casts are performed from large ships in very deep water; however, CRED also conducts these casts in much shallower waters around coral reefs to measure the water that is actually interacting with the reef. In addition to the standard salinity, temperature and depth sensors on our CTD, we also measure dissolved oxygen levels, and we have a transmissometer attached which essentially measures the amount of particulate matter in the water. Furthermore, we have been collecting nutrient and chlorophyll grab samples to measure the waters basic productive capacity and primary productivity levels.

Jamie Gove installing a CAU stake (photo by Danny Merritt)

In more recent years, CRED has been making strides to understand the effects of increased carbon in the nearshore reef waters. The ocean is absorbing a large portion of the increased carbon dioxide that has been released into the atmosphere since industrialization. While that process removes excess greenhouse gases from the atmosphere, it makes the ocean less basic. The pH scale goes from 0 (acid) to 14 (base) with 7 being neutral. Most ocean waters are slightly basic on the pH scale, usually measuring in the 8’s. Increased carbon levels are moving ocean waters towards the neutral level making it more difficult for anything that creates a calcium carbonate shell, such as coral reefs, to grow. In order to better understand the chemistry that is happening due to these processes, CRED collects dissolved inorganic carbon (DIC) and total alkalinity (TA) water samples. Further, as a way of directly measuring calcification rates on the reefs (i.e. how fast reef is growing), CRED and its partners at Scripps Oceanographic Institute developed CAU’s, which are simply a pair of 4 inch square plates that are mounted to the bottom. In 2 years, the plates will be collected and calcium carbonate growth on the plates will be measured directly (see previous posting from Cristi Richards).

All this was done just in time to get back to the ship, clean gear, shower, eat, download instruments, process data, assist the ships survey technician with night time operations and prepare our gear for another day on the water do any number of jobs.