In search of the tiniest Pontocaspian plants in Romania

During the first PRIDE training meeting thirteen Early Stage Researchers (ESRs) gathered in Romania to learn about different field techniques and collect their first data. Among them Manuel, a Spanish biologist working at the Brunel University in London.

Manuel's goal during these two weeks was to collect information on the diversity of tiny (± 0.2 to 0.0005 cm) “plants” and seeds respectively called dinoflagellates and dinocysts. Dinoflagellates and its dinocysts are found living in open seas and lakes as a part of what is called phytoplankton. Phytoplankton is formed by mostly microscopic “plants” as dinoflagellates, freely floating in the water. Among many other services, they are important due to their production of oxygen, which we use to breath.

Picture 1 and 2: Dinoflagellates. Photos by Manuel Sala

Manuel: “We started in the Razim lake complex situated on the Romanian Black Sea coast. This set of lakes straddles the coast for 40 km from the Danube delta in the north to the city of Constanţa in the south. It is a very good place to start because different salinity gradients (from fresh to brackish water) within the complex create different environments for these organisms.” We collected the dinoflagellates by towing a phytoplankton net horizontally behind the boat for two minutes. We captured the dinoflagellates within the net and transferred them to plastic bottles.

Besides filtering the water with a net, we checked the sediment of the lake floor for the presence of dinocysts. We collected sand and clay using a tool called Van Veen grab, which works as if two metal hands ‘grab’ the top layer of the lake floor. Once the sediments were pulled up on the boat we could scrap off the top layer and collect this in small plastic bags (pictures below).

After the successful data collection on the smaller lakes, it was time to do similar work on a bigger scale. While thick grey clouds packed together above the Black Sea, the huge research vessel Mare Nigrum was waiting in the harbor of Constanţa for the scientists to board. From there the ship would navigate to different sampling locations on the Black Sea, so each of the researchers could collect his or her data.

Pictures 3 and 4: Van Veen grab (left) and Manuel collecting sediment samples (right). Photos by Anouk D’Hont

Unfortunately for Manuel, there were no phytoplankton nets available on the ship, but they did have a fancy apparatus called CTD bottle water sampler offering a solution. This device takes water samples at different depths in the sea. These water samples were filtered by Manuel to concentrate the dinoflagellates in a smaller volume and kept in plastic tubes the next day in the lab. Here we also took sediment samples using a bigger version of the Van Veen grab, and another special tool called multicorer. The multicorer is a man-high device containing four Plexiglas tubes which are pushed into the seafloor sediment giving us four cores. With these cores we can look at life in the seafloor but also study its recent history.

Picture 5: The multicorer (left) and a CTD bottle water sampler (right) on board of the Mare Nigrum. Photo by Sabrina van de Velde

After two weeks in Romania, we returned to London with a beautiful sample set. In the future we will report results and much more about these tiny but hugely interesting “plants”!

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Authors: Anouk D’Hont, Sabrina van de Velde, Manuel Sala Pérez

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