Cruise GU-03-03, Leg I
August 28 - September 11, 2003

We have just finished the first leg of the Fall Plankton cruise. The 2-week trip was the diametric opposite of the mammal cruises in more ways than one. The most obvious difference was the search for miniscule plankton versus gigantic whales and handsome marine mammals. The method of research was different as well; instead of frequently diverting from the trackline to ‘chase’ mammals, the location of the plankton stations was ‘cast in stone'. Plankton net tows were conducted and water samples were collected at 68 stations. These stations were determined 18 years ago and have been occupied once a year ever since. In fact, the accuracy of the research hinges on repeatedly collecting the data from the same exact locations.

The cruise took us close inshore and into the most rig-occupied waters of the Gulf of Mexico. Below is a chart of the area of operation. The turquoise color show water depths less than 20 meters (60 feet) and each black square represents at least one rig (usually, a cluster of rigs).

Area of operation. (Click on image for larger view)

Getting to and from stations was also hindered by numerous wrecks (circled in pencil) whose exact positions were unknown, we gave those a very wide berth. (Click on image for larger view)

Another challenge was vessel traffic. Unlike the rigs and wrecks which are stationary, the vessels move. There are many different types of vessels traversing the waters of the Gulf. The following list represents the ones we see most often and deal with on a daily basis:

Big ships referred to as ‘Deep Drafts’ (i.e., container ships, tankers, etc). Due to size, they are restricted in their ability to maneuver around rigs. To ensure their safe passage, clear navigation paths called ‘fairways’ were established. Smaller vessels like the GORDON GUNTER use the fairways with extreme caution.   Smaller vessels associated with the rigs are called ‘supply’ and ‘crew’ boats. They are often seen either resting alongside the rigs or, moving between them.   Commercial fishing vessels, mostly shrimp boats, frequently change course and speed in search of shrimp and it is a challenge to keep out of their way.

‘Supply’ and ‘crew’ boats alongside a rig.

A typical radar picture.

The ship is at the center of the screen, heading east. Each dot and dash represent an object, referred to as a ‘contact.’ There were over 100 contacts in a 12 mile radius when this picture was taken. The long dashes represent relative motion of the contacts closest to the ship. Of these, most are stationary (rigs) but several are ‘movers’ (the long dashes that do not line up parallel to the ship’s course are the ‘movers’). Radar information is continually interpreted in relation to what we see out the window. Over time, we learn to recognize the vessels by size, speed and heading and maneuver accordingly.

To complete the picture, one more very important factor has to be mentioned – weather. Four days into the trip, tropical storm “Grace” formed, practically on top of us. We escaped the teeth of the storm but had our share of 'rocking and rolling' before the wind calmed down and the seas flattened. The weather held beautifully for the reminder of the trip except for several local thunderstorms. One storm was particularly memorable – it was a lightning ‘show‘ spectacle. The lightning was so intense, for so long, that we had no choice but to cancel operations and evacuate the area. It was beautiful from a distance though.

The above rounds out the report for Leg I. Leg II which began on September 16, will take us to the eastern, less crowded, part of the Gulf of Mexico. Weather permitting, we will occupy 82 stations for a total of 150 for this project. More on the scientific aspect of the Fall Plankton cruise, when we return from Leg II at the end of September.

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•  Updated: September 17, 2003