JBL workshop Žralok Bahamy 2018

Testing water amongst the sharks

Almost all the participants of the JBL Shark Workshop were aquarists too. This meant we were also interested in the water values of the Caribbean. We had taken along our JBL water tests, a hydrometer for density measurements, a refractometer (also for density measurements), a conductivity meter, a light meter with waterproof sensor (for lux measurements) and a PAR meter (for measuring the photosynthetically active radiation) with a waterproof cover.

Our JBL sales manager Didier insisted on doing the water tests out on the reef at the sharks. The water values were absolutely identical to the values at the beach, but it was more fun with the sharks around us! And our dive master Chad tested enthusiastically and worked for the first time with a conductivity meter. The sharks briefly examined the electrode dangling in the water, but did not find it very exciting.

The water values were much more exciting for us, because even if the oceans are the most water-stable systems on earth, there are regional differences. We started with measurements at the stern of the boat outside on the reef and continued the measurements in shallow water directly in front of the south beach.

The pH value at the reef and at the beach was 8.2, which was normal for marine water. The conductivity meter showed 55.1 mS/cm at 30.7 ° C near the beach. A measurement of the salinity using the refractometer and the JBL hydrometer led to an identical density result of 1.024.

As always, the light measurements were very informative. Lux values of around 100,000 above water have already lost 10 % through waves and reflection alone just below the water surface. In 50 cm water depth and crystal clear Caribbean water only 70 % of the overwater values still remained. But 70,000 lux are still significantly more than 1000 lux with standard LEDs at the bottom of the aquarium!

We wanted to finish by carrying out some PAR measurements. The PAR value of the light indicates how much photosythetically active radiation is present. A pure red or blue light source would produce practically no radiation for plants to use for photosynthesis. Sunlight generates about 1800 μmol m2 s. With increasing depth not only is red light absorbed, but also photosynthetically active radiation. At a depth of 40 cm, the PAR value as already dropped to 1000 μmol m2 s.

With the help of the JBL water tests we determined the carbonate hardness (7 ° dKH), the calcium content (440 mg/l) and the magnesium content (1600 mg/l). These values on the reef were also identical with those near the beach.