Abstract
The exchange of genetic material between seagrass meadows is fundamental to maintaining their genetic diversity and, consequently, resilience against stressors and disturbances. Increasingly, biophysical models are being used to predict the movement and dispersal of seagrass propagules (i.e. fruits, seeds, vegetative fragments) to better understand connectivity among populations. Describing how propagules behave under different hydrodynamic and environmental conditions is critical to ensuring the accuracy and reliability of such models. However, this information is lacking for vegetative fragments which have been relatively understudied compared to sexual propagules as a vector for long-distance dispersal. To address this knowledge gap, we investigated: (i) the effects of shading on the decay rates, buoyancy and morphometrics of fragments in two tropical seagrass species (Halophila ovalis and Thalassia hemprichii) over time; and (ii) the transport speeds of fragments of four species (T. hemprichii, Cymodocea rotundata, H. ovalis and Halodule uninervis) under varying wind, wave and current conditions in a flume. Our study revealed that higher shading resulted in a faster rate of fragment decay and buoyancy loss over time. Various morphometric measurements also decreased with lower light levels after the month-long experiment. Through our flume experiments, we found that winds can contribute to the transport of seagrass fragments, although the average wind drag of 0.915% was lower than the 4% previously documented for reproductive seagrass shoots. Additionally, small waves (those with smaller wave height and lower frequency) led to faster transport speeds than large waves. The results of this study provide important experimentally-obtained parameters that are crucial for the development of accurate predictive models for seagrass fragment dispersal.
| Original language | English |
|---|---|
| Article number | 106430 |
| Journal | Estuarine, Coastal and Shelf Science |
| Volume | 232 |
| DOIs | |
| Publication status | Published - 5 Jan 2020 |
| Externally published | Yes |
Funding
This research was supported by National Parks Board (NParks), Singapore Coastal and Marine Environment Research Grant ( R-154-000-670-490 , 2015). Seagrass samples were collected under permit number NP/RP16-011d issued by the National Parks Board . The authors would like to thank the staff and students at the Experimental Marine Ecology Laboratory, National University of Singapore , for their support in the field and in the laboratory. Special thanks to the Royal Netherlands Institute for Sea Research (NIOZ) in Yerseke, for the use of their flume, and a heartfelt thank you to the staff at the NIOZ-Yerseke, especially Bert Sinke, Jeroen van Dalen, Lennart van IJzerloo, and Zhu Zhenchang for their help in the preparation and set up of the flume, and for lending a hand when we needed help troubleshooting. The authors would like to acknowledge the St. John's Island National Marine Laboratory for providing the facility necessary for conducting the research. The Laboratory is a National Research Infrastructure under the National Research Foundation Singapore. Appendix A
Keywords
- Connectivity
- Cymodocea rotundata
- Halodule uninervis
- Halophila ovalis
- Movement ecology
- Thalassia hemprichii