Seagrasses comprise 78 species and are rarely invasive. But the seagrass Halophila stipulacea, firstly recorded in the Caribbean in the year 2002, has spread quickly throughout the region. Previous works have described this species as invasive in the Caribbean, forming dense mats that exclude native seagrass species. During a reconnaissance field survey of Caribbean seagrass meadows at the islands of Bonaire and Sint Maarten in 2013, we observed that this species was only extremely dense at 5 out of 10 studied meadows. Compared to areas with sparse growth of H. stipulacea, these dense meadows showed consistently higher nutrient concentrations, as indicated by higher leaf tissue N contents of the seagrass Thalassia testudinum (dense when C:N < 22.5) and sediments (dense when %N > 11.3). Thus, the potential invasiveness of this non-native seagrass most likely depends on the environmental conditions, especially the nutrient concentrations.
This month’s issue focuses on the development of the Dutch Caribbean Biodiversity Database, which addresses one of the biggest gaps for nature conservation on our islands – lack of access to relevant and reliable biodiversity information. The database, which was recently relaunched at www.dcbd.nl is the central repository for all biodiversity-related research and monitoring data, maps and literature for the six islands.
Amongst others, you will find in this sixth issue:
- Overview of Research and Monitoring Efforts
- Mangrove Management for Conservation of the Queen Conch (by Sabine Engel)
- Invasive Seagrass in Lac Bay, Bonaire (by Sabine Engel)
- ‘Research of the Month‘: Dutch Caribbean Biodiversity Database (by Peter Verweij)
- Maritime Incident Response Workshop on St. Maarten
- Calendar of Upcoming Events, Meetings and Workshops
In February 2013 the St. Maarten Nature Foundation confirmed the presence of Halophila stipulacea, an invasive seagrass, in the Simpson Bay Lagoon. The first unconfirmed, anecdotal report of a specimen of H. stipulacea being present in the Simpson Bay Lagoon dates back to 2010, when an EIA on the construction of the Lagoon Causeway was performed.
Extensive beds of H. stipulacea were found at three different locations: Big Key, Little Key and in the southeastern part of the Lagoon. St. Maarten is currently one of only four territories where the species has been found, thus research on controlling measures in the region are still in their infancy. A dedicated, detailed mapping project will show the real extent of distribution.
One of the areas in Simpson Bay where most specimens were found was the planned location for the causeway. The dredging of this site in the near future will result in a definite reduction of H. stipulacea. However, this is not a solution that can be implemented everywhere. Therefore an alternative remedy has to be found to ensure that the species does not gain too much foothold within the ecosystem. The possibility of seeding areas with native grasses in an attempt to control the invasion is currently being investigated.