Invasive seagrass

Invasive Seagrass and its effects on Juvenile Queen Conch

As invasive seagrass continues to expand and replace native species, populations such as the queen conch are seeing significant changes to their habitat and subsequent negative impact in food source availability. With potential consequence for the resilience of such species in a changing world. A recently published study from St. Barthelemy, St. Eustatius and St. Maarten, worked to understand how native and invasive seagrasses influence juvenile queen conch’s development by studying both dietary composition and growth rate.

 

This article was published in BioNews29

More information: Boman, E.M., Bervoets, T., de Graaf, M., Dewenter, J., Maitz, A., Meijer Zu Schlochtern, M.P., Stapel, J., Smaal, A.C., Nagelkerke, L.A.J., 2019. Diet and growth of juvenile queen conch Lobatus gigas (Gastropoda: Strombidae) in native, mixed and invasive seagrass habitats. MARINE ECOLOGY PROGRESS SERIES. Vol. 621: 143–154, 2019 https://doi.org/10.3354/meps12990

 

 

 

Date
2019
Data type
Media
Theme
Education and outreach
Research and monitoring
Geographic location
St. Eustatius
St. Maarten
Author

Invasive seagrass mega herbivore interactions

Invasive seagrass mega herbivore interactions
a study on the invasion of seagrass Halophila stipulacea in a Southern Caribbean lagoon affected by C. mydas grazing
In the Caribbean, the recent invasion of the seagrass species Halophila stipulacea has raised concerns regarding its impact on the invaded seagrass ecosystem and its associated flora and fauna. The main purpose of the experimental set-up was to understand the mechanisms and impacts of invasive species on a native seagrass in interaction with grazing impacts by the green sea turtle (C. mydas). The aims of the study were i.) to determine the colonization capacity of native seagrass species T. testudinum as affected by the presence of the invasive species (Halophila stipulacea) and vice-versa in a Caribbean lagoon (Lac Bay, Bonaire); ii.) To determine whether sexually and/or vegetatively colonization is affected by turtle grazing. and iii) to determine whether architectural properties of T.testudinum and H. stipulacea are affected by presence of other species and whether these are related to C. mydas grazing. For this study, four seagrass bed types were selected that naturally occur in the bay: (1) monoculture of T. testudinum, (2) monoculture of H. stipulacea , (3) mixed bed of H. stipulacea and T. testudinum and (4) mixed bed containing H. stipulacea, T. testudinum and S. filiforme. In each seagrass bed type, 12 experimental units were created divided over three experimental periods of six weeks. Within each unit, two patches of 150 x 150 mm were cleared of above and below ground biomass. Cages were placed over half of the cleared patches to prevent turtle grazing. After six weeks, recolonization of the patches by native species and invasive species were measured by resampling biomass. To assess whether turtle grazing changed architectural properties, measurements on length and width with and without grazing were taken. Lastly, lines around two T. testudinum turtle grazing plots were placed to measure the lateral expansion rate of the surrounding H. stipulacea patches.
Our results indicate that H. stipulacea is a ~11 times faster colonizer than T. testudinum. Effects of grazing on their colonization rate were different with T. testudinum colonization rate under C. mydas grazing being lower and H. stipulacea’s colonization rate being higher. These effects were not statistically proven, but strong trends were observed. The presence of other seagrass species did not seem to influence competitive abilities (colonization capacity and architectural properties). C. mydas grazing, on the other hand, clearly influenced T. testudinum’s architectural properties. Regarding T. testudinum’s grazing plots, an average lateral expansion of 0.35 cm day-1 by H. stipulacea was detected.
This study demonstrates that there is no direct competition between T. testudinum and H. stipulacea. It seems that H. stipulacea is colonizing areas unsuitable to T. testudinum. Sea turtle grazing creates less dense seagrass beds and therefore might further stimulate the expansion of H. stipulacea. The impact of the establishment of H. stipulacea on C. mydas is not yet clear: Even though it seems not to be the preferred seagrass species, C. mydas does graze on the invasive species in Lac Bay. It is, however, unknown how this new food resource will affect their fitness. Though the invasive may alter abiotic conditions in their habitat, the sea turtles may benefit from an extended cover of seagrass beds as the invasive seagrass is able to grow in places where native seagrass species currently cannot survive. It is recommended to keep monitoring changes and investigating the impact of H. stipulacea on the whole ecosystem.
 
Retreived from http://www.bonaireturtles.org on Aprile 13, 2015
 

Date
2014
Data type
Other resources
Theme
Research and monitoring
Geographic location
Bonaire

Continued expansion of the trans-Atlantic invasive marine angiosperm Halophila stipulacea in the Eastern Caribbean

Abstract:

Halophila stipulacea (Hydrocharitaceae) is reported for the first time from Aruba, Curaçao, Grenadines (Grenada), St. Eustatius, St. John (US Virgin Islands), St. Martin (France), and St. Vincent and the Grenadines, bringing the total number of known occurrences from eastern Caribbean islands to 19. Native to the Red Sea and western Indian Ocean, H. stipulacea spread to the Mediterranean Sea in the late 1800s and became established in the eastern Caribbean in 2002. The species has dispersed north and south of its first sighting in Grenada and now spans a latitudinal distance of 6° (>700 km), most likely facilitated by a combination of commercial and recreational boat traffic. The continuing range expansion of H. stipulacea indicates the species has successfully acclimated to surviving in the Caribbean environment, warranting further investigation into its ecological interactions with the indigenous seagrasses.

Date
2013
Data type
Scientific article
Theme
Research and monitoring
Document
Journal
Geographic location
Aruba
Curacao
St. Eustatius
St. Maarten

BioNews 6 - June/July 2013

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:

Date
2013
Data type
Media
Theme
Education and outreach
Research and monitoring
Geographic location
Aruba
Bonaire
Curacao
Saba
St. Eustatius
St. Maarten
Author

Results of Nature Foundation Research into invasive Seagrass H. stipulacea in the Simpson Bay Lagoon

Abstract:

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.

Management Recommendations:

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.

 

Date
2013
Data type
Research report
Theme
Research and monitoring
Geographic location
St. Maarten
Author