Light availability in the coastal ocean: Impact on the distribution of benthic photosynthetic organisms and their contribution to primary production

Some photosynthetic organisms can grow deeper than the nominal bottom limit of the coastal ocean (200 m). The minimum irradiance required varies from 0.4 to 5.1 mol photons m⁻² d⁻¹ depending on the group considered. The daily compensation irradiance of benthic communities ranges from 0.24 to 4.4 mol photons m⁻² d⁻¹.

Data on benthic irradiance and light requirements are combined to estimate the surface area of the coastal ocean where (1) light does not limit the distribution of primary producers and (2) net community production (NCP, the balance between gross primary production and community respiration) is positive. Positive benthic NCP can occur over 33% of the global shelf area. The limitations of this approach, related to the spatial resolution of the satellite data, the parameterization used to convert reflectance data to irradiance, the lack of global information on the benthic nepheloid layer, and the relatively limited biological information available, are discussed.