Mismanaged plastic wate from anthropogenic activities on land inadvertently accumulates in the ocean. Plastic threats to marine wildlife are well documented, however the effects of microplastics (fragments < 5 mm) are still largely unknown. Microplastics have spread to all major oceanic ecosystems including seagrass beds. These unique habitats stabilise sediment and attenuate wave energy, creating a natural barrier to erosion and are ideal nursery grounds for a variety of fauna. However, recent studies have shown that these attributes may cause seagrass beds to act as microplastic sinks, adhering onto seagrass blade biofilms and accumulating in the sediment. If these habitats do act as sinks, enhanced microplastic aggregation may not only harm fauna present but also the seagrass themselves. Microplastics have reduced chlorophyll concentrations and cell viability in algae and freshwater plants, hindering photosynthesis and growth. Similar impacts may also be observed in seagrass. We will present our findings on impacts to seagrass health based on: (1) photosynthetic output and (2) reproductive capacity, in Zostera muelleri, a widespread species throughout Australia’s eastern and southern coasts. As the first study to determine microplastic impacts on seagrass health, this will provide novel data on these key ecosystems already under stress.