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The Segunda Archipelago and the Zambezi river flats

There is an old saying that seeing is believing, while actually seeing is interpreting. We have seen a variety of complex habitats including corral reefs, underwater sea canyons and mud flats. Now it is our task to interpret how these habitats function.

ction.

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Decorator crab – Macropodia sp. (body 5cm long). Photo: Christiane Todt.

The Dr. Fridtjof Nansen is on tour southwards. This weeks priority areas have been the Segunda Archipelago, a collection of sand/reef islands located in the central-northern zone of Mozambique, and the Zambezi river sand and mud flats on the Sofala Bank.

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Mantis shrimp – Squillidae sp. (body 15cm long). Photo: Christiane Todt.

Segunda Archipelago

The islands of the Segunda Archipelago are a marine biologist’s haven. The diversity of colourful marine invertebrate life may take the breath away from anyone. Decorator crabs, sea and brittle stars, sea cucumbers in purple and yellow and sponges of all varieties and colours are taken from the deep. Some may be identified on the spot but the vast majority must be taken back on land to the lab and studied more thoroughly. There is just no literature available to reveal their names. The site is also home to a variety of turtle species including the green turtles (Chelonia mydas) the hawksbill (Eretmochelys imbricata) and the loggerhead (Caretta caretta) and is considered one of the most important turtle nesting sites in the world. If that is not enough, thousands of birds, including a colony of more than 30,000 nests of sooty terns (Sterna fuscata) and the greater crested terns (Sterna bergii), are fighting for space on the small islands. All signs of the high abundance of marine animals that they feed on. Time is short and flies away. Two days are all we have got to try to imprint it. Next stop is the Zambezi River.

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Burrowing crab – not determined yet (body 2cm long). Photo: Christiane Todt.

The Zambezi river mud flats

The Sofala bank outside the opening of the Zambezi River is a completely different ecosystem. The place seemed familiar for us that have worked onboard Dr. Fridtjof Nansen off the West African coast, although with different species, the ecosystem at the first blink resembled shelf areas there. The dominant fish species are pelagic, sardinellas and horse mackerels.

Primary production, the growth of small plankton algae, is the basis for fish production in the shelf areas around the world. The Sofala bank is among the most productive fishing areas in Mozambique due to its high primary production and it is this primary production we have been asked to study.

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Crab – not determined yet (body 7cm long). Photo: Christiane Todt.

During our first night in the area we are welcomed by a group of around 20 bottlenose dolphins that swim around the boat for an hour looking at the various instruments we are putting in the water. They are fed by local scientists with fish previously caught the same day. The days spent in the area are used to carry out an intensive sampling program collecting plankton samples with regular intervals from the same spot and various depths. This will, when the data are analysed in the lab, assists us to understand the ecological processes generating the high primary production on the Sofala Bank.

~see more species

By Jens-Otto Krakstad & Diana Zaera