Photo credit: Erik Wurz
Researchers from Wageningen University and the University of Amsterdam report on a fascinating case of competition between an animal and an invasive pIant. In tropical ecosystems, photosynthesizing organisms are continuously competing for space and light. The invasive seagrass Halophila stipulacea has been very successful in new habitats both in the Mediterranean and Caribbean seas. It can quickly colonize these habitats because small fragments break off, remain viable and spread via currents.
In a new paper published in Ecology, the researchers report on their discovery that the invasive seagrass uses little mounds - created by burrowing animals as shrimp or seacucumbers – as a new habitat to settle and expand from. The mounds provide new space with sufficient light, opening up the dense meadows of native seagrass where the invasive seagrass otherwise cannot settle. From there, they observed that the invasive seagrass can spread.
But the researchers found that this can cause problems for native species. ‘The upside-down jellyfish lies upside down because it has photosynthetic algae in its tentacles. Therefore, these organisms also need light and prefer open spaces such as these mounds created by burrowing animals. WUR Msc student Naomi Slikboer recorded the presence of both invasive seagrass and upside-down jellyfish on many of these mounds on the island of Curaçao and found that often, the invasive seagrass pushes the upside-down jellyfish out of these habitats over time’, according to the lead author of the study, Fee Smulders.
Photo credit: Erik Wurz
This probably increases the energetic costs for the jellyfish as it has to move more often due to rapid overgrowth of H. stipulacea. Additionally, the authors hypothesize that the interplay between invasive seagrass and burrowing mounds will lead unstable, dynamic seagrass meadows, unfavorable for valuable native seagrass species. Fee Smulders: ‘We need to keep a close watch on this invasive seagrass and investigate the impact on both native species as well as the seascape patch dynamics in Caribbean seagrass meadows.’
