Submersible PAR sensors (MKV-L, Alec Electronics, Japan) are used to
measure instantaneous irradiance at the surface and on the seafloor.
The measuring range of these sensors is 0-2000 µmol
m-2 s-1 with
resolution to 0.5 µmol m-2
s-1. There are two types of sensors, one
set calibrated for water and another for air.
In 2016, MKV spherical sensors were replaced with DEFI-L planar
sensors. Spherical and planar sensors were deployed side by side at 3
sites for 6 weeks. These paired measurements of irradiance were used
to estimate the relationship between irradiance measured from planar
sensors and irradiance measured from spherical sensors. Daily
irradiance values beginning in April, 2016 are estimates of irradiance
from spherical sensors generated using measurements of irradiance from
More details sensor deployment and retrieve can be seen in protocol.