Threatened Species
Johnson's seagrass (Halophila johnsonii)
National Marine Fisheries Service
Office of Protected Resources
Siltation due to human disturbance and increased land-use can also threaten viability of the species. Degradation of water quality due to human impact is also a threat to the viability of ecologically important seagrass communities. Nutrient over enrichment, caused by inorganic and organic nitrogen and phosphorus loading via urban and agricultural land run-off, can stimulate increased algal growth that may smother Johnson's seagrass by shading rooted vegetation and diminishing the oxygen content of the water.