April 12, 2004
Today's dive in Portimão Canyon off the southern coast of Portugal took divers to the continental shelf and the slope of the canyon wall. The Delta submersible touched ground on the continental shelf, which is the region of the continent that is under the sea, where the water was about 120 meters (393 feet) deep.
The coastal seas above the continental shelf are important because they provide sources of food and energy, are valuable for business, shipping, and recreation and are greatly impacted by human activities such as fishing, boating, pollution, and development.
The continental slope was rich with crinoids, or Feathered sea stars (Antedon sp.), as well as large Pink shrimp (Parapenaeus longirostris). This abundance of life exists because the area is not heavily fished with trawl nets, which disturb the bottom, digging up the organisms that are attached to the sediment. At about 150 meters (492 feet), a school of mackerel (Scomber sp.) joined the dive by surrounding the submersible. The lights from the sub attracted the zooplankton, which the fish feed on, so they got to enjoy an easy lunch. At one point, the fish had been swimming with the current, but turned around and swam against it so that the current could sweep their prey into their mouths.
Going deeper to 260 meters (853 feet) on a plateau at the head of the canyon, trawl marks were visible, as well as beer cans and bottles, plastic bags, and other trash. Marine animals were nowhere near as plentiful as on the slope, which is not heavily fished.
A brief period of excitement about the discovery of a piece of debris from a potential archeological site quickly faded as the explorers realized that the debris was a metal cable from a modern trawl net.
Tomorrow we will be diving in the deep axis (the middle) of the canyon looking for archeological targets. The objectives of these dives are to search for future archeological study sites to help understand Portuguese heritage.
Cool Fact for Today:
"Marine snow" is made up of particles of organic matter (like plankton) that are suspended in the water column and look just like an underwater snowstorm. Unfortunately the "snow" can reduce the visibility during a dive.
April 13, 2004
Too Much Trawling
“Not a lot of biodiversity, but too much trawling.” Pedro Terrinha, Geologist Trawl nets reach deep! The first dive today took the Delta Submersible to the bottom of the central axis of Portim￣o Canyon at 285 m (935 feet), where it worked its way up the slope to 210 meters (689 feet). The second dive explored the northeast wall of the canyon.
According to geologist Pedro Terrinha, who made the first dive this morning, the central axis of the canyon is not very rich in species diversity. There was strong evidence of heavy fishing in the area, with markings from large trawl nets showing up as paths cut into the sediment on the ocean bottom. See the Cool Fact for more information.
At 285 meters (935 feet), a strong current left ripples in the sand and polychaete worms who live on the sea floor were bent over because of the strength of the water movement. Although the explorers found many trawl marks here, they also found species of Moray eel (Muraenidae sp.) pictured above, Scorpion fish (Scorpaena sp.), anemones (Actiniaria sp.), and brittle stars (Ophiuroidea sp.). Click on the photos to enlarge them.
Tune in tomorrow for an exciting day as staff from Zoomarine, an oceanographic education facility here in Portugal, join us aboard the Portuguese Navy vessel Schultz Xavier to reintroduce injured turtles have been rehabilitated.
Cool Fact for Today:
Trawl marks in the bottom of the canyon are drag marks left by the doors of a trawl fishing net. Trawls can leave an undersea landscape devoid of life.
April 14, 2004
"Back Home Again"
Staff from Zoomarine, an oceanographic education facility in Portugal, joined SEMAPP explorers today to reintroduce 8 Loggerhead turtles (Caretta caretta) back into the sea. The animals were taken out in a smaller boat because they had to be reintroduced far enough away from the ship so that they would not be injured by the propellers.
Andrómeda was a small turtle that was found in northern Portugal during the January 2003 oil spill off the coast of Spain. The Schultz Xavier was one of the ships that responded to that spill, and a crew member aboard today was also on board then. As a kind of reunion, he helped to reintroduce Andrómeda back into the ocean. When she arrived at Zoomarine, Andrómeda was 22 centimeters (8.7 inches) long and weighed 2.2 kilograms (4.9 pounds). When she swam away today, she weighed 6.6 kilograms (14.6 pounds) and was 33.8 centimeters (13.3 inches) long.
Marroquina, now a very large turtle, was caught in a fisherman's net near Faro, Portugal in February of 2001, with her intestines obstructed by a large amount of sand. At that time, she was 27 centimeters (10.6 inches) long and weighed 2.5 kilograms (5.5 pounds). Now she weighs a whopping 44 kilograms (97 pounds) and her carapace measures 61 centimeters (24 inches). (Click on the picture at left to see video of Marroquina.) Marroquina was in the Rehabilitation Center at Zoomarine for three years because she was participating in a study that compared reptile hearts with human hearts.
Marco Bragança, a Biologist and Educator from Zoomarine, commented about today's reintroductions: " We are happy that these turtles are getting back to the wild, but we still have a lot of work to do with the other animals in the rehabilitation center."
Because of the heavy winds and rough seas, SEMAPP explorers were not able to dive in the Delta today.
Cool Facts for Today:
Loggerhead sea turtles are listed as "threatened" throughout the world since 1978 and their status has not changed. All sea turtles return to the same beach on which they were born to lay their eggs. For more information about loggerhead turtles, click here.
April 15, 2004
Delta Down Deep
The Schultz Xavier was called away to an urgent mission, so we were unable to dive in Portimao Canyon today. This log will feature some frequently asked questions and cool facts about the Delta submersible.
1) How deep can the Delta dive?
It can go as deep as 365 meters
2) What is it like inside the sub?
It is a very small space, which holds only a pilot and one observer. Short observers fit more comfortably inside, but still find themselves twisting around to try to look out all of the viewports. It is said that the inside of the sub smells like “submarine,” which is somewhat damp, kind of like the basement of a house.
3) How does the submersible pilot communicate with the ship?
There are two systems of communication. One uses a device called a transponder that pinpoints the location of the sub in relation to the ship. The sub is tracked from the surface on a computer monitor, which is shown in the photo to the right (click to enlarge). The other is a hydrophone, which allows the sub pilot to talk with the people on the ship.
4) What are the tasks for the explorers when they are diving?
They take video to document everything they are seeing so that the data can be quantified. They have to constantly narrate during the dive, which provides another description of their observations. Divers must also fill out a log after their dive to document again everything that they saw, noting particular events or fauna of interest.
5) Why is the Delta submersible being used for this expedition?
Delta is easier and quicker than other submersibles to launch and recover, it allows explorers to come within 6 inches of the sea floor, it is very easy to maneuver, and can dive with a higher sea state than other submersible systems.
6) How is the Delta launched and recovered?
Click on the pictures below to find out.
Cool Facts for Today:
Since 1987, the Delta submersible has made 6189 dives (and counting), has dived Taiwan, Israel, Alaska, Marshall Islands, South Africa, Ireland, and has never lost a day of diving due to technical malfunctions. Delta has seen several famous shipwrecks, such as the Edmund Fitzgerald and the Lusitania.