Zostera marina
Ordinary seaweed washed up on the beach
The Common eelgrass ( Zostera marina) is a flowering plant in the family of seagrass plants ( Zosteraceae ). It grows submerged ( submerged ) to the sea coasts of the northern hemisphere, where it forms together with other marine species from the order of plantain -like ( Alismatales ) underwater seagrass meadows which are important habitats for fish for spawning and other marine animals.
Description
The ordinary seaweed grows as an evergreen, perennial herbaceous plant, reaching lengths of 30 to 100 centimeters. It is anchored by a monopodial rhizome in the ground. The leaves have at their base a closed leaf sheath that forms no ears. Simple, for example 3-9 mm wide leaf blade having three to seven parallel nerves and a rounded tip.
The flowers are arranged in two rows on either side of a flattened ears axis (the spadix ) and flowering time in a spathe ( the spathe ) are included. The stem of the spathe is above downward slightly broadened. Each single flower contains both a dust and a carpel. The ordinary seaweed is made of walnut fruits which are cylindrical in shape and have a two-column style on top. Your pollen is thready.
Occurrence
It grows submerged in the coastal waters of the North and Baltic Seas and oceans in near the mainland; there it comes down to a depth of 10 m, occasionally up to 17 m, above. It is spread across the entire Northern Hemisphere. In places, however, its deployment is driven due to anthropogenic influences. Therefore, it is classified in Germany in the Red List of endangered ferns and flowering plants as being at risk ( hazard category 3).
Ecology and pollination biology
Since the 1930s, can be observed in northern Europe, and especially on the German North Sea and Baltic Sea coast, a decline in the structure-forming seagrass meadows of Zostera marina. The observed in recent years in the North Sea strong seagrass death can not be explained by the known population fluctuations in seagrass species. The trigger next to the infestation by parasitic fungi ( Labyrinthulomycetes ) are presumed anthropogenic causes such as increasing water pollution, increasing the degree of turbidity of the water and eutrophication. Seagrass beds are ecologically particularly valuable because they offer protection for numerous species of animals. So make seaweed stocks, for example, often important spawning grounds of fish dar.
The ordinary seaweed blooms from June to September. Pollination of flowers is exclusively submerged. The individual flowers form from a thread-like pollen, which is only spread through the water. Have little nut fruits formed, these are also spread through the water. Often has also been observed that certain birds or fish eat the fruits, thus contributing to the elimination of the exposed seeds for propagation.