On this page you can find a series of small videos called «Things we do in CIMA», which will help us to explain what we do and how we do it. All this to approach the world of marine biology and oceanography.
– «Things we do in CIMA» #7: Underwater quadrants: Do you remember the video in which we were talking about the cartography of plant species? There we´ve mentioned you the purpose of transects with video camera for cartographing the submarine plant species (in this particular case, Cymodocea nodosa).
Just like on land, sometimes we need to study the populations throughly and sample the underwater vegetation in more details.
In order to do it, we submerge within the area of Cymodocea nodosa meadows, according to the cartography previously obtained by the company or according to the data provided by other studies. We mark new transects by random extensions of the metric tape within the meadow and then we use 25 x 25 cm quadrants. We place it along the transects and it helps us to determine the plants density, coverage and frequency.
The sampling is carried out by means of non-destructive methods with the help of the abovementioned quadrant and a board that has a ruler imprint into one of its sides. The board is also used for recording all the data obtained as well as information from the sampling spot that needs to be highlighted.
Each sampling consists of two parts:
– Density determination: is calculated by the number of shoots contained in the 25 x 25 cm quadrant;
– Shoots’ height: 10 leaves from inside the centre of the quadrant have to be measured. Each plant usually has 2 or 3 leaves, so we measure the highest leave of the plant.
In this way we can accurately describe the actual state of the meadow, determining the zones of higher, medium and lower density of plants and track its changes in further studies.
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