“Sun-shade” adaptation in microbenthic algae from the Øresund

Changes in the “sun-shade” adaptation in microbenthic algae in the Øresund have been investigated. At 8 m water depth the algae of the sediment surface were “shade”-adapted during most of the time. The maximum Ik-value reached was about 9 klux. At 0.3 m water depth a maximum Ik-value of about 21 klux was found. At both localities the lowest Ik reached was about 4 klux. There was no significant difference in Ik between the pseudo-benthic algae (free-living algae) and the psammophytic algae (algae attached to the sand grains). Also the adaptation-change of algae buried at various depths in the sediment has been investigated. In October-November, algae from 6–7 cm depth have an Ik similar to that of the surface algae, indicating occasional vertical mixing of the sediment.