The infauna habitat of invasive seagrass Halophila stipulacea on the Dutch Caribbean island of St Eustatius.

Student Report 

Since the opening of the 160km long Suez canal on November 17, 1869, it was possible for large ships to navigate between the Mediterranean and the Red Sea. Halophila stipulacea has very short roots that can be pulled loose from the soil very easily and it is capable of reproduction by fragmentation. A fragment suspended in the water column can survive for approximately two weeks.When the habitat conditions for H. stipulacea are ideal it can resettle and regrow a large seagrass field within months. This way H. stipulacea managed to find his way to Flamingo bay, Grenada in 2002. Since then it rapidly spread across the whole Caribbean sea.


This non-native species pose a threat to the native seagrasses found in the Caribbean around the island, as it is fast-growing and tolerant to a greater range of conditions. This change in seagrass composition could lead to significant habitat change and affect the ecosystem around the island. The aim of this report is to identify the species found resident in the H. stipulacea beds at key dive sites around the island of St. Eustatius.


To determine the habitat usage 20 samples were collected between 18 and 20m depth at two popular dive sites. With a sample corer, the samples were lifted from the soil and placed in a double zipper bag. In total 390 individual animals were found in the samples. The biomass was measured giving the results that most of the plant structure is on or below the ground surface.


Based on this research, further monitoring of the seagrass beds is needed to find out what new habitat H. Stipulacea creates. To give a significant correct answer between the dry biomass and the number of species found / individuals, a statistical analysis is recommended. 



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