NOAA Teacher at Sea
Aboard NOAA Ship Oregon II
July 8-19, 2019
Mission: Leg III of SEAMAP Summer Groundfish Survey
Geographic Area of Cruise: Gulf of Mexico
Date: July 11, 2019
Weather Data from the Bridge:
Latitude: 28.29° N
Longitude: 83.18° W
Wave Height: 1-2 feet
Wind Speed: 11 knots
Wind Direction: 190
Visibility: 10 nm
Air Temperature: 29.8°C
Barometric Pressure: 1013.6 mb
Sky: Few clouds
As I mentioned in my introductory post, the purpose of the SEAMAP Summer Groundfish Survey is to collect data for managing commercial fisheries in the Gulf of Mexico. However, the science involved is much more complex than counting and measuring fish varieties.
The research crew gathers data in three ways. The first way involves trawling for fish. The bulk of the work on-board focuses on trawling or dragging a 42-foot net along the bottom of the Gulf floor for 30 minutes. Then cranes haul the net and its catch, and the research team and other personnel weigh the catch. The shift team sorts the haul which involves pulling out all of the shrimp and red snapper, which are the most commercially important species, and taking random samples of the rest. Then the team counts each species in the sample and record weights and measurements in a database called FSCS (Fisheries Scientific Computer System).
SEAMAP can be used by various government, educational, and private entities. For example, in the Gulf data is used to protect the shrimp and red snapper populations. For several years, Gulf states have been closing the shrimp fishery and putting limits on the snapper catches seasonally to allow the population to reproduce and grow. The SEAMAP data helps determine the length of the season and size limits for each species.
Another method of data collection is conductivity, temperature, and depth measurements (CTD). The process involves taking readings on the surface, the bottom of Gulf floor, and at least two other points between in order to create a CTD profile of the water sampled at each trawling locations. The data becomes important in order to assess the extent of hypoxia or “dead zones” in the Gulf (see how compounded data is used to build maps of hypoxic areas of the Gulf: https://www.noaa.gov/media-release/noaa-forecasts-very-large-dead-zone-for-gulf-of-mexico). Plotting and measuring characteristics of hypoxia have become a major part of fishery research especially in the Gulf, which has the second largest area of seasonal hypoxia in the world around the Mississippi Delta area. SEAMAP data collected since the early 1980s show that the zone of hypoxia in the Gulf has been spreading, unfortunately. One recent research sample taken near Corpus Christi, TX indicated that hypoxia was occurring further south than in the past. This summer, during surveys two CTD devices are being used. The first is a large cylinder-shaped machine that travels the depth of the water for its readings. It provides a single snapshot. The second CTD is called a “Manta,” which is a multi-parameter water quality sonde (or probe). While it can be used for many kinds of water quality tests, NOAA is using it to test for hypoxia across a swath of sea while pulling the trawling net. This help determine the rate of oxygenation at a different depth in the water and across a wider field than the other CTD can provide.
Did You Know?
Algae is a major problem in the Gulf of Mexico. Hypoxia is often associated with the overgrowth of certain species of algae, which can lead to oxygen depletion when they die, sink to the bottom, and decompose. Two major outbreaks of algae contamination have occurred in the past three years. From 2017-2018, red algae, which is common in the Gulf, began washing ashore in Florida. “Red Tide” is the common name for these algae blooms, which are large concentrations of aquatic microorganisms, such as protozoans and unicellular algae. The upwelling of nutrients from the sea floor, often following massive storms, provides for the algae and triggers bloom events. The wave of hurricanes (including Irma and during this period caused the bloom. The second is more recent. Currently, beaches nearest the Mississippi Delta have been closed due to an abundance of green algae. This toxic algae bloom resulted from large amounts of nutrients, pesticides, fertilizers being released into the Bonnet Carre Spillway in Louisiana because of the record-high Mississippi River levels near Lake Pontchartrain. The spillway opening is being blamed for high mortality rates of dolphins, oysters and other aquatic life, as well as the algae blooms plaguing Louisiana and Mississippi waters.
Pulling away from Pascagoula yesterday, I knew we were headed into open waters for the next day and half as we traveled east down the coast to the Tampa Bay, FL area. I stood on the fore deck and watched Oregon II cruise past the shipyard, the old naval station, the refinery, navigation buoys, barrier islands, and returning vessels. The Gulf is a busy place. While the two major oceans that flank either side of the U.S. seem so dominant, the Gulf as the ninth largest body of water in the world and has just as much importance. As a basin linked to the Atlantic Ocean, the tidal ranges in the Gulf are extremely small due to the narrow connection with the ocean. This means that outside of major weather, the Gulf is relatively calm, which is not the case with our trip.
As we cruise into open waters, along the horizon we can see drilling platforms jutting out of the Gulf like skyscrapers or resorts lining the distant shore. Oil and gas extraction are huge in this region. Steaming alongside us are oil tankers coming up from the south and cargo ships with towering containers moving back and forth between Latin America and the US Coast. What’s in the Gulf (marine wildlife and natural resources) has geographic importance, but what comes across the Gulf has strategic value too.
The further we cruised away from Mississippi, the water became choppy. The storm clouds that delayed our departure the day before were now overhead. In the distances, rain connected the sky to sea. While the storm is predicted to move northwest, the hope is that we can avoid its intensification over the Gulf Stream as we move southeasterly.
I learned that water in the Gulf this July is much warmer than normal. As a result, locally produced tropical storms have formed over the Gulf. Typically, tropical storms (the prelude to a hurricane) form over the Atlantic closer to the Equator and move North. Sometimes they can form in isolated areas like the Gulf. Near us, an isolated tropical storm (named Barry) is pushing us toward research stations closer to the coast in order to avoid more turbulent and windy working conditions. While the research we are conducting is important, safety and security aboard the ship comes first.