Fig 1.
Changes in downwelling photosynthetic active radiation (PAR) and spectral composition of the underwater light in different depths in the Gulf of Aqaba off the Interuniversity Institute in Eilat on the 29th October 2015.
(a) Percentage of PAR at various depths expressed as % of surface PAR (1400 μmol*m-2*s-1). The inset shows the values for mesophotic depths. (b) Depth-dependent changes in spectral irradiance.
Fig 2.
In-situ survey of fluorescence in mesophotic corals.
(a) Green fluorescence of Euphyllia paradivisia and (b) Orange-red fluorescence of Dipsastraea favus photographed under excitation by the blue-dominated natural light at depths of ~60 m. (c) Fluorescence imaging system photography showing the orange-red fluorescence emission of Echinophyllia aspera and the green fluorescence of Alveopora ocellata at ~53 m prior to collection for laboratory analyses.
Fig 3.
Fluorescence signature of corals collected from mesophotic depths in the Gulf of Eilat/Aqaba.
Photographs show the appearance of representative specimens under daylight (left column) or imaged under blue light through a yellow long-pass filter (Nightsea) (middle column). Fluorescence spectra (right column) were recorded after excitation with 450 nm light. Peak positions are indicated by arrows. (a) Oxypora egyptensis, (b) Alveopora ocellata, (c) Goniopora minor, (d) Pleuractis granulosa and (e) Echinophyllia aspera.
Fig 4.
Colour polymorphism of Goniopora somaliensis.
Representative colonies of the (a) green, (b) yellow and (c) red colour morphs were imaged in situ at 50–60 m depth by flashlight photography (left column). Their fluorescence, excited by the natural, down-welling blue-dominated light during daytime was bright enough to be photographed using a yellow long-pass barrier filter (Nightsea) (middle column). Fluorescence emission spectra were recorded under blue light excitation (450 nm) after transfer of the corals to the laboratory (right column). Peak positions are indicated by arrows.
Fig 5.
Changes in fluorescence of colour morphs of Euphyllia paradivisa from mesophotic depths in response to altered light environments.
The daylight appearance and blue-light- induced fluorescence of the green (a), red (b) and yellow (c) colour morphs are imaged after one year of culture under low intensity daylight (upper row) and in complete darkness (lower row). Fluorescence emission spectra in the range of GFP-like proteins (450–650 nm) and chlorophyll (650–800 nm), measured by excitation with ~450 nm, are shown for the displayed individuals. Peak positions are indicated by arrows.
Table 1.
Fluorescence emission maxima of corals and corallimorpharians from Eilat reefs.
Fig 6.
Fluorescence of S. pistillata and A. squarrosa from depths ≥60 m.
Images, taken after the specimens were collected, show the daylight appearance (left column) and the blue-light-induced fluorescence of the upper and underside of the branches (middle/right column).
Fig 7.
Changes in the tissue fluorescence of Echinophyllia sp. in response to experimentally-altered light environments.
(a) The daylight appearance (upper panel) and blue-light-induced fluorescence (lower panel) were imaged after 6 months of culture under low intensity, full spectrum white light (violet light [+]) or cyan light (~480 nm, violet light [-]). (b) Fluorescence emission per area upon excitation with 420 nm light was quantified for violet light [+] and violet light [–] treated corals. Spectra represent the means of 10 individual measurements taken from 3 different replicate colonies exposed to the corresponding light environments. Peak positions are indicated by arrows. (c) A violet light [–] treated specimen was photographed with a Leica digital video camera attached to an Olympus fluorescence stereomicroscope using a GFP filter set before (upper image) and after (lower image) exposure of the region of interest (ROI) to focused 380 nm light.