Robert Lovely, April 10, 2008

NOAA Teacher at Sea
Robert Lovely
Onboard NOAA Ship Gordon Gunter
March 31 – April 12, 2008

Mission: Reef Fish Ecological Survey
Geographical area of cruise: Pulley Ridge and the West Florida Shelf, Gulf of Mexico
Date: April 10, 2008

A bank sea bass (Centropristis ocyurus) tucked in under one of the rock outcrops along the West Florida Shelf.

A bank sea bass (Centropristis ocyurus) tucked in under one of the rock outcrops along the West Florida Shelf.

Weather Data from the Bridge 
Visibility:  12 miles
Wind Direction:  120 degrees
Wind Speed:  16 knots
Sea Wave Height:  2-3 foot
Swell Wave Height:  3-4 foot
Seawater Temp.: 22.1 degrees C.
Present Weather:  Partly Cloudy

Science and Technology Log 

Today we made three ROV dives on the West Florida Shelf, roughly 100 miles off the west coast of Florida. After making our usual CTD profile (see Ship’s Log, April 4, 2008) at about 0730, we lowered the ROV to a depth of 262 feet and followed a transect bearing southwest.  The object was to conduct a fish survey with respect to species presence and abundance as a function of bottom habitat types. Essentially, we were looking for good hard-bottom fish habitats within an area being proposed to the Gulf of Mexico Fishery Management Council as a new Marine Protected Area (MPA).

A blue angelfish (Holacanthus bermudensis).

A blue angelfish (Holacanthus bermudensis).

Each of the video transects revealed a mix of sand and hard bottom, with fish most abundant in areas having some topographic relief. Numerous hard rock outcrops offered attractive habitat for a wide variety of reef fish, such as scamp (Mycteroperca phenax), red porgy (Pagrus pagrus), red snapper (Lutjanus campechanus), almaco jack (Seriola rivoliana) greater amberjack (Seriola dumerili), short bigeye (Pristigenys alta), bank butterflyfish (Chaetodon aya), great barracuda (Sphyraena barracuda), red grouper (Epinephelus morio), blue angelfish (Holacanthus bermudensis), creolefish (Paranthias furcifer) saddle bass (Serranus notospilus) bank sea bass (Centropristis ocyurus) and many others. The sand flats in between ridges and reef outcroppings provided a stark contrast in terms of fish abundance.  Over these areas the ROV would glide for minutes at a time without revealing many fish.  But even in these less productive bottom habitats we would see the occasional fish dart into its hole as we passed over.

A school of jackknife fish (Equetus lanceolatus) captured by the ROV over the West Florida Shelf.

A school of jackknife fish captured by the ROV over the West Florida Shelf.

A sea star (Class: Asteroidea) on the sand flats between reef outcroppings.

A sea star (Class: Asteroidea) on the sand
flats between reef outcroppings.

Personal Log 

The quality and abundance of food on the GORDON GUNTER is remarkable, and I find it impossible to resist (especially the deserts).  I’d rather not return home ten pounds heavier than when I left, so I’ve been trying to visit the weight room whenever I can find the time.  During my first few sessions on the treadmill I had to hang on for dear life due to the rocking motion of the ship. It was pretty comical.  Now, though, I am getting fairly good at going no-handed while compensating for the ship’s motion.  It requires some dexterity, but it’s great practice for getting your sea legs. We also saw other common sea creatures, such as gorgonians, wire coral, basket stars, sea stars, feather sea pens, sea urchins, sponges and snails.

A short bigeye (Pristigenys alta) ready to dart into his hole on the sand flats.

A short bigeye (Pristigenys alta) ready to dart into his hole on the sand flats.

Basket stars (Order: Phrynophiurida) spread their plankton nets near the top of a gorgonian.

Basket stars (Order: Phrynophiurida) spread their plankton nets near the top of a gorgonian.

Robert Lovely, April 5, 2008

NOAA Teacher at Sea
Robert Lovely
Onboard NOAA Ship Gordon Gunter
March 31 – April 12, 2008

Mission: Reef Fish Ecological Survey
Geographical area of cruise: Pulley Ridge and the West Florida Shelf, Gulf of Mexico
Date: April 5, 2008

This sea anemone was part of a remarkably diverse community found on Pulley Ridge at a depth of about 212 feet.

This sea anemone was part of a remarkably diverse community on Pulley Ridge at about 212 feet.

Weather Data from the Bridge 
Visibility: 7-8 miles
Wind Direction:  140 degrees (SE)
Wind Speed:  13 knots
Sea Wave Height:  1-2 feet
Swell Wave Height:  2-3 feet
Seawater Temp.: 24.7 degrees C.
Present Weather:  Clear

Science and Technology Log 

Today we made three two-hour ROV dives on Pulley Ridge.  We documented an impressive amount of biodiversity along three transects at depths that ranged from about 190 to 225 feet. Downward still images of the bottom were taken at regular four minute intervals; forward facing still shots were taken whenever something of interest presented itself; and a continuous forward-looking video recording was made of the entire transect.

Agaricia sp., a hermatypic (reef-building) coral we found at about 215 feet.

Agaricia sp., reef-building coral we found at 215 feet.

The ideal cruising speed for the ROV video recording is a very slow one-half knot, which presents significant challenges for the people on the bridge. In fact the Commanding Officer, LCDR Brian Parker, remarked on how good a training exercise this cruise is for his team.  Upon our return to port, and for weeks afterwards, fishery biologist Stacey Harter will analyze the video to derive density estimates for the fishes observed.  She will determine the area covered by each video transect and count individuals of each species that intercepted our transect line.  Abundance estimates then can be extrapolated per unit area.  Others will use similar techniques to determine the aerial extent of living corals.  These data, in turn, will be useful to authorities responsible for managing the fisheries. Pulley Ridge is a drowned barrier island system that formed about 14,000 years ago, when sea levels were lower because a larger portion of the Earth’s water was locked up in glacial ice. While the presence of photosynthetic corals, such as Agaricia spp. was patchy on our dives, we did encounter large fields of green algae in relatively high densities.

The green algae, Anadyomene menziesii, dominated large areas in the southern portion of Pulley Ridge.

The green algae, Anadyomene menziesii, dominated large areas in the southern portion of Pulley Ridge.

This species no doubt is the Anadyomene menziesii described by Robert Halley and his group at the USGS. These striking seascapes resembled large fields of lettuce.  At the southern end of Pulley Ridge this green algae dominated the seabed.  As we moved northward from station to station, however, it occurred in much lower densities, and we began to see higher proportions of the calcareous green algae Halimeda spp. Various species of red coralline algae were also common on Pulley Ridge. Apart from the abundance of Anadyomene menziesii, the other striking observation one makes on this deep coral reef is the presence of conical-shaped mounds and pits.  These structures are almost certainly constructed by fish, such as the sand tilefish (Malacanthus plumieri) and red grouper (Epinephelus morio). Sand tilefish in particular burrow into the coral rubble and pile it up for cover. Red grouper are also industrious excavators.

 A red grouper (Epinephelus morio) at rest in a small pit on Pulley Ridge.


A red grouper at rest in a small pit on Pulley Ridge.

The mounds and pits introduce an element of topographic relief into an otherwise flat seascape along the top of Pulley Ridge.  Because so many other species of fish are attracted to these structures, I would suggest that (at least among the fish) sand tilefish and red grouper represent keystone species in this unique ecosystem.  The removal of these two species would have a significant impact on the rest of the community. Other fauna we observed today were typical of what one might encounter on a shallow-water reef, including sponges, tunicates, lobsters, bryozoans, amberjacks, angelfish, reef butterflyfish, snapper, barracuda, and a loggerhead turtle.

Personal Log 

My favorite place on the ship is the boatswain’s chair way up on the bow. No one else seems to know about it, for I have yet to find it occupied when I want to use it.  It is the quietest, most scenic spot on the ship.  Whenever I get a chance, I sneak up there to watch the flying fish. They are flushed by the ship, and some of them can remain in flight for long periods, perhaps 20 seconds or more. If I am especially lucky, I also get to watch dolphins riding our bow. This is a real treat because they seem so playful.

Our ROV disturbs the nap of a loggerhead turtle (Caretta caretta).

Our ROV disturbs the nap of a loggerhead turtle (Caretta caretta).

A pod of dolphins bow-riding the GORDON GUNTER.

A pod of dolphins bow-riding the ship. 

Robert Lovely, April 4, 2008

NOAA Teacher at Sea
Robert Lovely
Onboard NOAA Ship Gordon Gunter
March 31 – April 12, 2008

Mission: Reef Fish Ecological Survey
Geographical area of cruise: Pulley Ridge and the West Florida Shelf, Gulf of Mexico
Date: April 4, 2008

A “rosette” is used to hold the instrumentation for the CTD.  Here we see the rosette being lowered down into the water column by way of a crane mounted on the GORDON GUNTER.

A “rosette” is used to hold the instrumentation for the CTD. Here it is lowered down into the water by way of a crane.

Weather Data from the Bridge 
Visibility:  12 miles
Wind Direction:  150° (SE)
Wind Speed:  18 knots
Sea Wave Height:  2-3 foot
Swell Wave Height:  1-2 foot
Seawater Temp: 24.4 degrees C.
Present Weather:  Clear

Science and Technology Log 

We begin and end each day by making a CTD profile of the water column at our sampling site.  CTD refers to conductivity, temperature, and depth, but other parameters, such as dissolved oxygen (DO), also may be measured.  Conductivity is an expression of salinity, which at our location on Pulley Ridge is pretty uniform throughout the water column.  As we see from the graph below, however, both DO and water temperature do vary with depth. Temperature is uniform in the top layer of water and then begins to drop steadily with increasing depth from about 20 meters down.  This portion of the water column, where temperature declines rapidly with depth, is called the thermocline.  The temperature profile on our graph shows that a subtle thermocline extends nearly to the bottom at Pulley Ridge. This may help explain why certain shallow-water organisms are able to survive in this relatively deep water. In other locations the same depth may be well below the thermocline and therefore in water too cold for shallow-water species to live.

Above is a graph of the CTD profiles generated at Pulley Ridge on April 4, 2008.  Software linked to the CTD instrumentation on the rosette generates salinity, temperature, depth and oxygen profiles of the water column.  Note that the double lines on the graph result from the roundtrip made by the rosette down to the bottom and back.

Graph of the CTD profiles from Pulley Ridge. Software linked to the CTD instrumentation on the rosette generates salinity, temperature, depth and oxygen profiles of the water. The double lines on the graph result from the roundtrip down to the bottom and back.

Dissolved oxygen is normally high at the surface due to the mixing effect of wave action. But oxygen concentrations can be high in the deeper thermocline as well simply because cold water can hold more oxygen than warm water.  Our graph above illustrates this relationship by exhibiting an increase in dissolved oxygen concentrations at depths between 20-45 meters.

This remotely operated vehicle (ROV) carries both a video camera and a still camera.  The yellow umbilical shown in the foreground supplies power and control signals from the GORDON GUNTER.

This remotely operated vehicle (ROV) carries both a video camera and a still camera. The yellow umbilical shown in the foreground supplies power and control signals

Marine scientists employ different types of underwater vehicles to collect data on deep coral reefs, and the different vehicle types may seem a bit confusing at first.  Three important underwater vehicles are Submersibles, AUVs, and ROVs.  Submersibles typically refer to human-occupied vehicles, where a pilot climbs inside and drives the vehicle around like a small submarine.  The most famous example is Alvin, a submarine operated by the Woods Hole Oceanographic Institution. AUVs, in contrast, are Autonomous Underwater Vehicles that are programmed to perform specific functions, such as bathymetric mapping.  AUVs are robotic— they are completely independent, having no wires to the surface.  Finally, ROVs are Remotely Operated Vehicles, which are tethered to the ship by means of a cable and umbilical.  The ROV captures video and still images, and is driven by a pilot from a control room onboard the ship.  While utilizing bathymetric charts created during earlier cruises, our mission on Pulley Ridge and the West Florida Shelf employs only the ROV.

Rob finds out that it’s interesting, but difficult, driving the ROV.

Rob finds out that it’s interesting, but difficult, driving the ROV.

Today we made three video transects (dives) with the ROV, each lasting about two hours.  Each dive followed a predetermined course, as we began working our way north along Pulley Ridge.  The depth of our dives normally ranged between 200-230 feet, with the ROV gliding about three feet above the reef. The ship towed the ROV at speeds that typically ranged from .5 to 1.3 knots.  However, because of the slack in the tether, the ROV itself had a remarkable range of speeds. In fact, skilled pilots can bring the ROV to a dead stop (while the ship continues to move) in order to pause for nice steady close-up shots of bottom organisms.  I was very impressed by this flexibility of motion and the freedom it offered the pilot to search around the reef for organisms hiding in nooks and crannies.

Personal Log 

I was given the opportunity to take the helm of the ROV during one of our video transects. I found this experience to be fun and somewhat akin to playing a video game.  However, I also found driving the ROV to be much more difficult than it looks.  It gave me a greater appreciation for the skill of our veteran pilots, Lance Horn and Glenn Taylor. 

Robert Lovely, April 2, 2008

NOAA Teacher at Sea
Robert Lovely
Onboard NOAA Ship Gordon Gunter
March 31 – April 12, 2008

Mission: Reef Fish Ecological Survey
Geographical area of cruise: Pulley Ridge and the West Florida Shelf, Gulf of Mexico
Date: April 2, 2008

NOAA ship GORDON GUNTER at the dock in its home port of Pascagoula, MS.

NOAA ship GORDON GUNTER at the dock in its home port of Pascagoula, MS.

Weather Data from the Bridge 
Visibility:  10-12 miles
Wind Direction:  East (080)
Wind Speed:  10 knots
Sea Wave Height:  1-2 foot
Swell Wave Height:  1-2 foot
Seawater Temperature: 23.93 C.
Present Weather Conditions:  Partly cloudy

Science and Technology Log 

After spinning around in circles in the harbor area so that a specialist could synchronize all the compasses onboard the ship, we left the Port of Pascagoula at about 10 a.m. on Monday, March 31. We would have two full days and nights of transit to our first station at Pulley Ridge, which lies about 54 nautical miles west of the Dry Tortugas (see map above).  The weather was cold, cloudy, and windy on the first day, and the waves ranged from four to six feet high.  This set the stage for a very rocky first day at sea. On day two, however, the seas flattened out, and the weather was beautiful, with a clear blue sky and only light winds. I could see for miles in every direction, but there was no land in sight. 

Southern Florida

Southern Florida

One of the main objectives of our mission is to identify the extent of live stony corals (order: scleractinia) on Pulley Ridge.  This approximately 20-mile long three-mile wide undersea ridge has been designated as a habitat area of particular concern, and consequently carries certain fishing restrictions.  Trawling gear, in particular, may not be used.  Moreover, fishers are not allowed to drop anchor, use long lines, bottom traps and other equipment that is apt to kill or damage the coral. Because the corals serve as prime breeding habitat for many commercially-important species of fish, it is in the long-term interest of the commercial fisheries to protect areas such as Pulley Ridge. Apart from its importance as fish habitat, though, Pulley Ridge also is unique because it contains the deepest known photosynthetic coral reefs on the U.S. continental shelf.  Scleractinian corals, such as Agaricia spp., thrive along with sponges and common species of reef algae in water some 250-feet deep.

Pulley Ridge dive sites.  The red dots indicate start and stop points for individual dive transects. Map by Marta Ribera.

Pulley Ridge dive sites. The red dots indicate start and stop points for individual dive transects.

Because the Pulley Ridge reefs lie well below the safe-diving limit of 130 feet, the most practical and efficient way to explore these unique habitats is by means of a remotely-operated vehicle (ROV) equipped with digital still and video cameras.  When deployed, the ROV is tethered to the ship by means of a long umbilical and driven by an operator in the control room.  The umbilical delivers electric power and control signals to the ROV. From the control room the ROV pilot watches a video monitor and steers the unit much like one would play a video game.  Video of the sea bottom is recorded continuously, while high resolution digital still frames are recorded at specific time intervals, such as every two minutes.  The scientific field party on this mission consists of six individuals, two of whom are dedicated to the operation and maintenance of the ROV.  The rest are biologists.  The ship itself carries a crew of 18. Long before we left port, Andrew David, the chief scientist, developed a cruise plan, which called for the ROV to make dives along specific transects. We reached our station for the first transect at about 7:30 this morning.

ROV team Lance Horn (left) and Glenn Taylor prepare the ROV for deployment.

ROV team Lance Horn and Glenn Taylor prepare the ROV for deployment.

After considerable setup, the ROV was deployed and lowered down to the bottom, about 300 feet below the surface.  ROV pilot Lance Horn drove the unit about a meter or two above the bottom, recording video continuously and taking digital still images at two-minute intervals.  Biologist Stacey Harter added narration to the video by identifying the different fishes and bottom conditions she saw on the monitors. Everything ran quite smoothly for the first half of the transect. But then the video light flooded and popped a breaker, causing the ROV to lose power. The unit had to be brought back onboard the ship for repairs.  That was it for the day. “The deep sea bottom is such an extreme environment,” said Andrew David, “that equipment break-downs like today’s are practically a routine part of doing science at sea.”

Personal Log 

While watching today’s operations, I couldn’t help but think how easy I have it when I take a class of students out onto Wisconsin lakes to do basic limnology.  We work from a small, easyto-maneuver pontoon boat.  None of our equipment is too heavy for a student to lift over the side and drop in. Our depths rarely exceed 20 meters.  Finally, we collect a considerable amount of data in just a three-hour lab period.

Chief scientist Andrew David feeds out the ROV’s umbilical during deployment.

Chief scientist Andrew David feeds out the ROV’s umbilical during deployment.

The ROV is lowered into the water.

The ROV is lowered into the water.

The ship’s dry lab serves as a control room for the ROV. From left to right: Marta Ribera (GIS specialist), ROV pilot Lance Horn, and Stacey Harter (fish biologist).

The ship’s dry lab serves as a control room for the ROV. From left to right: Marta Ribera (GIS specialist), ROV pilot Lance Horn, and Stacey Harter (fish biologist).