The DIVING-PAM Underwater Fluorometer is a worldwide unique instrument for studying in situ photosynthesis of underwater plants, including sea grasses, macroalgae, and zooxanthellae in corals.
Based on the large experience with chlorophyll fluorescence analyses of terrestrial plants, investigations using the DIVING-PAM have shaped a clearer understanding of underwater photosynthesis under natural conditions.
The DIVING-PAM fluorometer was derived from the particularly robust and reliable MINI-PAM device. A particular feature of the DIVING-PAM is the cylinder-shaped waterproof housing which is comfortable to handle underwater. A highly flexible fiberoptics and a range of purpose-tailored sample holders, as well as light, temperature, and depth sensors complete the basic DIVING-PAM equipment.
All settings and functions of the DIVING-PAM can be accessed by eight retro-reflective photoelectric switches. For long-term assessment of photosynthesis, the instrument can also be operated by a computer via a special underwater cable.
In the stand-alone mode, the measurement of the effective photochemical quantum yield just requires tapping on the START field. Then the fluorescence level, F, and the maximal level, Fm’, are measured. The effective photosynthesis yield is automatically calculated according to Y(II) = (Fm’-F)/Fm’. Data of F, Fm’ and Y(II) are displayed and stored internally for later analysis.
Also, photosynthetic photon flux density (μmol m-2 s-1) at sample level, relative electron transport rate and diving depth are shown. The DIVING-PAM further provides an extensive MODE-menu for determination of fluorescence quenching coefficients (qP, qN, and NPQ) and automatic recording of light and fluorescence induction curves.
|Measuring light source:||Red LED, 650 nm (version DIVING-PAM), or blue LED, 470 nm (DIVING-PAM/B). Standard intensity 0.15 µmol m-2 s-1 PAR. Modulation frequency 0.6 or 20 kHz, Auto 20 kHz function, burst-mode reducing integrated measuring light intensity by 80%|
|Halogen lamp:||8 V/20 W blue enriched, λ-2 s-1 PAR with continuous actinic illumination. Maximal 18000 µmol m-2 s-1 PAR during saturation pulses|
|Signal detection:||PIN-photodiode protected by long-pass filter (λ>710 nm in standard version, λ>650 nm in DIVING-PAM/B), selective window amplifier|
|Data memory:||CMOS RAM 128 kB, providing memory for up to 4000 data sets|
|Measured parameters:||Fo, Fm, Fm’, F, Fv/Fm (max. Yield), ΔF/Fm’ (Yield), qP, qN, NPQ, PAR (using Fiber Quantum Sensor), ETR (i.e. PAR x ΔF/Fm’), water temperature (-10°C to +60°C, in steps of 1°C), water depth (0 to -70 m, in steps of 0.1 m)|
|Display:||2 x 24 character alphanumerical LCD with backlight, character size 4.5 mm|
|User interface:||Eight retro-reflective photoelectric switches|
|PAR measurement:||0 to 20000 µmol m-2 s-1 PAR, in steps of 1 µmol m-2 s-1 PAR using fibre quantum sensor|
|PC-terminal operation:||Via RS 232 interface using WinControl software|
|Data transfer:||Via RS 232 using WinControl software|
|Power supply:||Internal rechargeable battery 12 V/2 Ah, providing power for up to 1000 yield measurements, automatic power/off, Battery Charger MINI-PAM/L|
|Operating temperature:||-5 to +45°C|
|Dimensions:||Diameter 19 cm, length 39 cm|
|Design:||Randomised 70 µm glass fibres forming single plastic shielded bundle with waterproof stainless steel adapter ends|
|Dimensions:||Active diameter 5.5 mm, outer diameter 8 mm; length 1.5 m|
|Fibre Quantum Sensor|
|Design:||Coated single plastic fibre with miniature diffuser|
|PAR measurement:||0 to 20000 µmol m-2 s-1 PAR in conjunction with DIVING-PAM|
|Dimensions:||Active diameter 1mm; length 1.5 m|
|Battery Charger MINI-PAM/L|
|Input:||90 to 264 V AC, 47 to 63 Hz|
|Output:||19 V DC, 3.7 A|
|Operating temperature:||0 to 40°C|
|Dimensions:||15 cm x 6 cm x 3 cm (L x W x H)|
|Dark Leaf Clip DIVING-LC|
|Design:||Three pieces of clips made of white plastic with gasket contact areas and sliding shutter for light-tight closure|
|Dimensions:||Diameter 3.2 cm, length 8 cm|
|Distance Clip 60° 2010-A|
|Design:||Metal clip with fibre holder and 11 mm sample hole: 5.5 cm x 1.4 cm (L x W)|
|Fiber holder:||1.2 cm length, mounted 0.7 cm above base, with lateral screw to fix fibre optics. Angle between fibre optics axis and sample plane: 60°. Two spacer rings to vary the distance between fibre end and leaf surface|
|RS 232 Interface Box DIVING-I|
|Design:||Aluminium housing with sockets for underwater cable, power supply and special RS 232 cable|
|Dimensions:||9.8 cm x 8.5 cm x 3.4 cm (L x W x H)|
|Underwater Cable DIVING-K5|
|Dimensions:||5 m length, 6 mm diameter, 250 g|
|Transport Case DIVING-T|
|Design:||Aluminium case with custom foam packing for DIVING-PAM and accessories|
|Dimensions:||58 cm x 38 cm x 25 cm (L x W x H)|
|System Control and Data Acquisition|
|Software:||WinControl-2 (Windows 3.1x/9x/Me/NT4/2000/XP). WinControl-3 (Windows XP/Vista, Windows 7 and 8).|
|USB-RS 232 adapter and RS 232 cable PAM-2000/K3||Variable specifications, depending on market offers|
|Universal Sample Holder DIVING-USH|
|Design:||Plexiglas bar (15 x 4.5 cm) with upward curved end possessing a port for DIVING-PAM fibre optics. Mounted to the curved end is a 5.5 cm x 7.5 cm (W x H) sample clip consisting of a Plexiglas plate (lower part) and an aluminium frame open to the top (upper part). Featuring a 10 cm long plastic grip with button for triggering measurements via a 1.5 m trigger cable. Including a 1 m long tubular net with zipper to keep together trigger cable and fibre optics.|
|Dimensions:||25 cm x 4.5 cm x 21 cm (L x W x H)|
|Surface Holder DIVING-SH|
|Design:||Holder made of grey PVC, equipped with 3 rubber bands and hooks to be attached to creviced surface (e.g. of coral); nylon screws for distance adjustment|
|Dimensions:||6 cm x 6 cm x 2.5 cm (L x W x H)|
|Magnet Sample Holder DIVING-MLC|
|Design:||Two halves with ring magnets, one with fiberoptics adapter and split rubber hood (dark adaptation), the other serving as buoyancy body|
|Dimensions:||Diameter 37 mm, height 48 mm|
|Weight:||60 g; floating underwater|
|Miniature Fiberoptics DIVING-F1|
|Design:||Single plastic fibre with adapter for DIVING-PAM|
|Dimensions:||Active diameter 2 mm, length 1.5 m|
|Underwater Cable DIVING-K25|
|Dimensions:||25 m length, 6 mm diameter, 1.25 kg|
|Underwater Cable DIVING-K50|
|Dimensions:||50 m length, 6 mm diameter, 2.5 kg. The Battery Charger MINI-PAM/L24 is supplied together with the DIVING-K50 cable|
A prototype of the DIVING-PAM was tested on the Spitsbergen Island under Arctic conditions. The chlorophyll fluorometer was used in the Kongsfjord and exposed to water depths down to 30 m, at a temperature of 0°C. Despite of these somewhat unusual conditions, it functioned without any problems.
For the first time, the saturation-pulse method was applied with simultaneous light measurement for an assessment of the effective quantum yield of photosystem II (ΔF/Fm’) in macroalgae in their natural underwater habitat. The aspect of quantum yield regulation as a function of the light adaptation state at low temperatures was a central subject of this investigation.
The brown alga Alaria esculenta was chosen as object of investigation. In the Kongs Fjord, this alga can reach a height of up to 5 m. This plant takes root in the rocky sea bed and is characterised by an upright stalk, with the top “leaf-region” reaching the water surface.
Measurements proved a clear correlation between the photosynthetic performance of individual “leaf-regions” and their distance from the surface. The most important differences (by about a factor of 3) were measured in the area between the surface (lowest quantum yield) and a depth of 60 cm, where almost maximum quantum yield was observed.
As expected, the relative suppression of photosynthesis reached its highest level at the time of the most intensive solar radiation at noon (the so-called midday depression). This phenomenon seems to reflect an important protection mechanism against damaging effects of excess light energy (heat dissipation). This is especially important when the enzymatic dark reactions are slowed down at low temperatures.