Seagrass under siege: Investigating microplastic effects on seagrass ecosystems

Microplastics (MPs) are ubiquitous in all major oceanic ecosystems including seagrass meadows. These unique habitats form ideal nursery grounds for important fauna while also capturing particulate matter, stabilising the surrounding sediment and creating a natural barrier to erosion. These same attributes have led to suggestions that these habitats act as a sink for MPs by adhering to seagrass blades and accumulating in sediment. Enhanced MP aggregation may not only harm local fauna, but also the seagrass themselves. Very limited data exists on MP effects on seagrass health, and only in short-term ( 14 day) experiments. We present our findings from a 90-day manipulative experiment on Zostera muelleri, a widespread species throughout the Indo-Pacific region. Various health performance indicators were negatively impacted after 90 days of exposure to synthetic playground rubber crumb and low-density polyethylene (LDPE) MPs in sediment. Most notably, leaf count, rhizome length, and biomass were significantly reduced with increased exposure (885 - 8850 MP/kg). Other morphological effects are discussed, in addition to findings related to microbiome and leachate analysis. The findings of this research provides novel data for stakeholders and policy-makers regarding the health of seagrass habitats already under threat. Also see: https://micro2024.sciencesconf.org/556090/document