Manipulation of the seagrass-associated microbiome reduces disease severity.

Host-associated microbes influence host health and function and can be a first line of defence against infections. While research increasingly shows that terrestrial plant microbiomes contribute to bacterial, fungal, and oomycete disease resistance, no comparable experimental work has investigated marine plant microbiomes or more diverse disease agents. We test the hypothesis that the eelgrass (Zostera marina) leaf microbiome increases resistance to seagrass wasting disease. From field eelgrass with paired diseased and asymptomatic tissue, 16S rRNA gene amplicon sequencing revealed that bacterial composition and richness varied markedly between diseased and asymptomatic tissue in one of the two years. This suggests that the influence of disease on eelgrass microbial communities may vary with environmental conditions. We next experimentally reduced the eelgrass microbiome with antibiotics and bleach, then inoculated plants with Labyrinthula zosterae, the causative agent of wasting disease. We detected significantly higher disease severity in eelgrass with a native microbiome than an experimentally reduced microbiome. Our results over multiple experiments do not support a protective role of the eelgrass microbiome against L. zosterae. Further studies of these marine host-microbe-pathogen relationships may continue to show new relationships between plant microbiomes and diseases.

Field Collection and Laboratory Maintenance of Canopy-Forming Giant Kelp to Facilitate Restoration.

Canopy-forming kelps are essential foundation species, supporting biodiversity and providing ecosystem services valued at more than USD$500 billion annually. The global decline of giant kelp forests due to climate-driven ecological stressors underscores the need for innovative restoration strategies. An emerging restoration technique known as 'green gravel' aims to seed young kelps over large areas without extensive underwater labor and represents a promising restoration tool due to cost-effectiveness and scalability. This video article illustrates a protocol and tools for culturing giant kelp, Macrocystis pyrifera. It also provides a resource for further studies to address the successes and limitations of this method in field settings. We outline field and laboratory-based methods for collecting reproductive tissue, sporulating, inoculating, rearing, maintaining, and monitoring substrates seeded with early life stages using the 'green gravel' technique. The protocol simplifies and centralizes current restoration practices in this field to support researchers, managers, and stakeholders in meeting kelp conservation objectives.