Cruise GU-03-03, Leg II
September 16 - September 29, 2003

The second leg of the Fall Plankton cruise took us to the eastern, less crowded part of the Gulf of Mexico. As mentioned in the report from Leg I, the plankton research is based on repeatedly collecting data from the same stations. These stations have been visited, weather permitting, every year since 1985. The map below shows the distribution of the plankton stations throughout the Gulf.

Overview of all the SEAMAP stations. Stations in blue were occupied on Leg I, stations in red were occupied on Leg II.

The primary objective of the survey is to estimate the abundance and distribution of different fish, in their larval and small juvenile stages. The data, in addition to information collected through other venues, provides fishery managers the means to establish policies and guidelines concerning the fishing industry in the Gulf of Mexico.

We conducted two types of tows to collect plankton samples. Neuston tows were conducted to collect samples on or near the surface while Bongo tows were conducted to collect samples from up to 200 m deep.

Bongo nets are 2 sleeves of very fine mesh that are shaped like a funnel. At the small end of the funnel is a cod end which can be made of mesh or hard plastic, the cod end is what the plankton is collected in and the contents are emptied on board to study in the lab. The 2 nets are connected to side by side metal rings.

The nets are lowered to just above the seafloor (or as deep as 200 m, whichever is shallower) and then brought to the surface at a predetermined rate of speed. The ship constantly adjusts its course and speed to keep the wire at a 45 degree angle. Variables such as wind, current, and sea surface conditions are significant factors in maintaining this angle.

The bongo nets are lowered into the water. Tow duration varies with depth.

SF Tom Sherman operates the winch while scientist Glen Zapfe measures the wire angle with the "frying pan".

A Neuston net is a fine mesh funnel shaped sleeve connected to a 7 ft x 3 1/2 ft (2 m x 1 m) metal frame, as with the Bongo net there is a cod end at the small end of the funnel where the plankton is collected.

It is towed alongside the ship for 10 minutes skimming the surface of the water for plankton.

The Neuston net is partially submerged during the 10 minute tow.

A closer look at the "mouth" of the Neuston net.

In addition to the plankton nets, temperature, salinity, fluorescence, chlorophyll and dissolved oxygen data was also collected at each station. This data was collected with a CTD (Conductivity, Temperature and Depth) unit. While the ship held station, the CTD unit was lowered into the water. The cast depths were to just above the seafloor or 200 m, whichever was shallower. The unit was then brought to the surface at a constant rate of speed. Water samples from maximum depth, mid-water depth and the surface were collected in the bottles attached to the CTD stand during the cast.

ENS Kurelja observes the CTD deployment from the bridge wing.

F Ropiak operates the winch while scientist Pamela Bond watches from the rail.

SF Barbosa and Scientist Glen Zapfe bring the CTD back onboard.

We occupied 75 stations on Leg II, we feel this was a great accomplishment considering it was hurricane season. In fact, we completed the second leg of the Fall Plankton cruise just in time to escape the effects of Tropical Storm Larry.

A few snapshots of life onboard the Gordon Gunter.

ENS Levine makes adjustments to the ship's speed during a Bongo tow in the quest for the 'perfect' 45-degree angle.	Ensigns Kurelja and Didier prepare to demonstrate the use of foam to extinguish a fire.	ENS Didier plots stations and courses on various charts.
SF Jorge Barbosa takes advantage of the nice weather for painting.	The ship's crew assembles on the fantail for a demonstration of the foam fire extinguishing system.	It's 'steak night'... 2nd Cook Lito Llena, always smiling, serves the best steaks in the Gulf.

The Deep Bottom Trawl cruise begins on October 7. Check our web page at the end of October to read the details and see the pictures from that trip!