by Brady Mears
[51K] Undergraduate students in the honors section of Assistant Professor Ben Giese's oceanography course. Front (left to right): Sarah Fischer and Ben Giese. Middle: Carrie Misak, Amy Schrader, Erin Crone, Brady Mears, and Lisa Frantzen. Back: Jennifer Wicecarver, J.T. Townley, and Andrew Jordan.
The first experiment involved collection of plankton. Zooplankton were caught with a 333 µm mesh net, which was towed for a prescribed amount of time. The volume of water that passed through the net was measured using the number of rotations of a propeller, and with that figure we calculated the concentration of zooplankton in the water. Later, we examined the zooplankton samples in the laboratory and observed copepods, salps, and radiolaria. Phytoplankton were collected in a net of much finer mesh (20 µm) that was hauled vertically. It caught many types of diatoms. We were able to observe plankton bioluminescence at night, and it was exciting to see other marine life in the gulf such as rays, dolphins, and jellyfish.
At each station, we deployed the conductivity, temperature, and depth profiler (CTD) rosette multisampler. This is a large, very heavy device, and to launch it required three strong students and an on-board winch. The rosette is a ring of cylinders with lids on each end. To collect water samples, the instrument package was slowly lowered through the water column, and at specific depths determined from temperature and salinity characteristics the lids of the individual cylinders were triggered to snap closed. When the instrument package was hoisted back onto the deck, the teams bottled the samples and measured the temperature and salinity of each one. From the CTD multisampler experiments we noted three main observations. First, as we left Galveston Bay, there was a significant increase in salinity. Second, salinity increases and temperature decreases as a function of depth. Finally, our analysis of the bottle samples showed that the water column in the gulf near Galveston is, on average, well-mixed.
[136K]The Earth Scan Laboratory at Louisiana State University (LSU) cooperated with Texas A&M University to provide images of sea-surface temperature from satellite overflights on April 1st and 2nd. Dr. Larry Rouse of LSU provided this AVHRR-MCSST image of our field area from 3 passes of the NOAA-14 satellite. The dark line shows the path of the R/V Gyre during the Oceanography 251 cruise. Various shades of grey show different surface temperatures in the northwest Gulf of Mexico. These remote sensing data allow local observations of salinity and temperature to be interpreted in wider, regional context.
The third experiment involved discovering what materials lie on the sea-floor. A device called a box core was dropped to the bottom of the water column, and the sediments it collected were dumped onto the deck. This activity appealed to the kid in each of us as we dug through the muddy clay scavenging for interesting shells and slimy organisms.
The weather on the trip could not have been more pleasant -- clear and sunny with a cool sea breeze. Even though some of us needed a little dramamine, we enjoyed our time at sea, especially in the free time between the experiment stations. We ate three full meals on board including a fried seafood dinner. We also read, talked, sunbathed, and some of us tried to take naps, but our captain decided to play a joke on us and sounded his foghorn inside our cabin! For most of the cruise the shore was out of range, and we felt free from civilization. We stargazed on Saturday night, saw a clear, bright sunrise Sunday at dawn, and a colorful sunset on Sunday evening. We arrived back in port at 9:30 p.m. and returned to College Station about three hours later feeling weary but accomplished.
On the whole, it was a very interesting and memorable trip. Everyone enjoyed experiencing firsthand what we studied in class and practicing the activities of professional oceanographers. It is not often that undergraduate college students have that kind of an opportunity. When can we do it again?!
Oceanography, Texas A&M University
Updated September 13, 1995