Lab-based multispectral photography for approximating chlorophyll content in Zostera marina

Reduced light is one of the primary threats to seagrass meadows in the coming decades, with reduced light reaching the benthos due to eutrophication. We assessed a multispectral photography technique using near-infrared photography to estimate chlorophyll content in the seagrass Zostera marina. Using near-infrared and red wavelength cameras in the lab environment, we measured normalized difference vegetation index (NDVI) in photographs of sampled seagrass leaves. In samples taken from three different environments, we found a positive correlation between lab-based NDVI and chlorophyll content, with variation attributable to leaf age. In samples grown under different light conditions, we found high levels of NDVI associated with lower light possibly due to seagrass photoacclimation. This method may be used in addition to existing seagrass monitoring methods to collect data on seagrass photic status and estimate chlorophyll content, and detect possible light limitation due to turbidity or high epibiota cover. The relatively low cost and time required for this method may make it useful where researchers are already collecting and imaging seagrass as part of routine monitoring.