Vegetative fragment production as a means of propagule dispersal for tropical seagrass meadows

S J Tol; A B Carter; P H York; J C Jarvis; A Grech; B C Congdon; R G Coles

doi:10.1016/j.marenvres.2023.106160

Vegetative fragment production as a means of propagule dispersal for tropical seagrass meadows

Mar Environ Res. 2023 Oct:191:106160. doi: 10.1016/j.marenvres.2023.106160. Epub 2023 Sep 4.

Authors

S J Tol¹, A B Carter², P H York², J C Jarvis³, A Grech⁴, B C Congdon⁵, R G Coles²

Affiliations

¹ Centre for Tropical Water and Aquatic Ecosystem Research (TropWATER), James Cook University, Cairns, Australia; College of Science and Engineering, James Cook University, Cairns, Australia. Electronic address: samantha.tol@jcu.edu.au.
² Centre for Tropical Water and Aquatic Ecosystem Research (TropWATER), James Cook University, Cairns, Australia.
³ University of North Carolina Wilmington, USA.
⁴ ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Australia.
⁵ College of Science and Engineering, James Cook University, Cairns, Australia.

PMID: 37678099
DOI: 10.1016/j.marenvres.2023.106160

Abstract

Background and aims: Long distance dispersal (LDD) contributes to the replenishment and recovery of tropical seagrass habitats exposed to disturbance, such as cyclones and infrastructure development. However, our current knowledge regarding the physical attributes of seagrass fragments that influence LDD predominantly stems from temperate species and regions. The goal of this paper is to measure seagrass fragment density and viability in two tropical species, assessing various factors influencing their distribution.

Methods: We measured the density and viability of floating seagrass fragments for two tropical seagrass species (Zostera muelleri and Halodule uninervis) in two coastal seagrass meadows in the central Great Barrier Reef World Heritage Area, Australia. We assessed the effect of wind speed, wind direction, seagrass growing/senescent season, seagrass meadow density, meadow location and dugong foraging intensity on fragment density. We also measured seagrass fragment structure and fragment viability; i.e., potential to establish into a new plant.

Key results: We found that seagrass meadow density, season, wind direction and wind speed influenced total fragment density, while season and wind speed influenced the density of viable fragments. Dugong foraging intensity did not influence fragment density. Our results indicate that wave action from winds combined with high seagrass meadow density increases seagrass fragment creation, and that more fragments are produced during the growing than the senescent season. Seagrass fragments classified as viable for Z. muelleri and H. uninervis had significantly more shoots and leaves than non-viable fragments. We collected 0.63 (±0.08 SE) floating viable fragments 100 m^-2 in the growing season, and 0.13 (±0.03 SE) viable fragments 100 m^-2 in the senescent season. Over a third (38%) of all fragments collected were viable.

Conclusion: There is likely to be a large number of viable seagrass fragments available for long distance dispersal. This study's outputs can inform dispersal and connectivity models that are used to direct seagrass ecosystem management and conservation strategies.

Keywords: Connectivity; Dispersal; Dugong; Fragment; Great barrier reef; Halodule uninervis; Halophila ovalis; Marine herbivore; Propagule; Zostera muelleri.

MeSH terms

Alismatales*
Animals
Australia
Dugong*
Ecosystem
Zosteraceae*