Expedition 2006 - South Africa and Lake Malawi

JBL Expedition 2006 - South Africa and Lake Malawi

Forschung

Summary of research results: All values measured are listed in the following tables

Water analysis in South Africa and Lake Malawi

Material, methods and results:

  1. JBL Water tests: pH, GH, KH, Mg, Ca, O₂, NH₄, NO₂, NO₃, PO₄
  2. JBL Precision Hydrometer
  3. JBL Precision Thermometer
  4. WTW Multi-testing device 340i for conductivity, oxygen, temperature and pH measurement.
  5. GPS device eTrex by GARMIN
  6. Water depth measuring with mares diving computer M1 RGBM
  7. Water temperature measuring when diving with mares diving computer M1 RGBM
  8. Underwater samples: A 250 ml JBL flask, filled at the surface, was taken to the depth at which a water sample was to be taken. The bottle was opened there, inverted and filled with air from the reserve regulator (Octopus), forcing the water out of the flask. The flask was then turned round again and filled with water once more. Evaluation took place after a maximum of 30 minutes.
  9. Results: The hardness levels clearly show that hardness is in the middle range and not, as many aquarium keepers believe, in the higher range! This is also reflected in the low conductivity. Moreover, it is clear that the soda sources, which feed the lake with sodium bicarbonate containing water, raise the KH without increasing the GH. The result is a higher carbonate hardness than the general hardness, as sodium does not count towards the total hardness (only Mg and Ca).
  10. Photos: All photos were taken with analogue Canon mirror reflex cameras (EOS 1V and EOS 3) in carbon underwater casings from BS-Kinetics. Films: Kodak Extra Colour 100 ASA. As flash equipment Subtronic Mega was used. Lenses: Canon EF 100 mm Makro USM, Canon EF 20-35 mm USM, Canon EF 28 mm 1:1.8 USM, Sigma 50 mm 1:2.8 Makro and Sigma 14 mm 1:3.5. For differing focal lengths the corresponding front ports for the underwater casings were used.

Water analysis - Lake Malawi / Simbawe Rock, 20.09.2006, 16:20

435 m a.s.l. / S 13° 59.970 / E 34° 50.942

   1 m depth  42 m depth
 Temperature  25° C  21° C
 KH  7° dKH  7° dKH
 GH  5.5° dGH  5° dGH
 pH  8.6  8.5
 Ammonium/Nitrite/Nitrate   0  0
 Oxygen in mg/l  8.0  7.5
 Calcium  not measurable    not measurable 
 Magnesium  not measurable   not measurable 
 Conductivity  243 µS/cm  237 µS/cm at 25.5° C 

Water analysis - South Africa / Aliwal Shoal, 10.09.2006, 15:30

S 30° 16.641 / E 30° 45.546

 Temperature  24° C
 KH  7° dKH
 pH  8.2
 Oxygen in mg/l  6
 Calcium  480 mg/l
 Magnesium  1200 mg/l
 Density  1.026
 Light measurements above water, cloudy   16,200 Lux

Water analysis - South Africa / Shark Alley 15.09.2006, 10:30

S 34° 51 / E 19° 24

 Temperature  13° C
 KH  7° dKH
 pH  8.2
 Ammonium/Nitrite/Nitrate  0 mg/l
 Oxygen in mg/l  6
 Calcium  460 mg/l
 Magnesium  1200 mg/l
 Density  1.024
 Conductivity  51.2 mS/cm 

Light measurements in South Africa and on Lake Malawi

Materials, methods and results:

  1. Luxmeter from PCE Group: PCE-174
  2. UV meter from PCE Group: PCE-UV34
  3. UV-A 390 filter from Hama
  4. GPS device eTrex from GARMIN
  5. Taking measurements:
    On land, the sensor of the meter was held in direct sunlight when possible, until the highest reading was shown on the display. Under water the luxmeter was placed in a watertight video camera casing. The light sensor was directly under the glass pane, where the lens of the camera would otherwise be positioned. The display of the meter could be read through the transparent casing. UV measurements: The sensor was moved and turned in the light until the highest possible stable reading was displayed. The UV-A radiation was blocked with a UV-A filter which filtered out the all rays up to 390 nm, leaving the UV-B value.
    Results:
    All the terrarium tubes on the market will soon be tested in detail for UV radiation and compared with the results measured. The results of the lux measurements clearly show that the water surface reflects almost 50% of the light, practically halving the lux level! Below the surface of the water the light intensity gradually decreases. For aquariums, the relevant range is to a depth of 100 cm.

Lux measurements Lake Malawi, 20.09.2006, 15.45

 Location   Lux 
 directly above the water surface  25.600 
 directly below the water surface   10.200 
 at 50 cm depth  8.000 
 at 1 m depth  7.600 
 at 2 m depth  6.800 
 at 3 m depth  6.800 
 at 4 m depth   6.600 
 at 5 m depth   6.200 

UV measurements (UV-A & UV-B) South Africa, 20.09.2006

 8:30 a.m. 0,33 
11:40 In the sun 1,63 
 shielded by paper 0,66 
 in the sun 4,22 
 shade 0,50 
 UV filter (390 nm) shield in sun   2,00 

UV measurements (UV-A & UV-B) Malawi, 22.09.2006

8:30 a.m
S 13° 59.970 / E 34° 50.942
435 m a.s.l.
Clear cloudless sky

 In the sun 4.25 
 UV-A (390 nm) filter shield 2.13 
 Shielded by paper 0.66 

Underwater feeding trials

On dives to the reefs near Aliwal Shoal and Protea Banks the divers took JBL MariPearls 250 ml cans with them, which were filled with water at the surface. When fish gathered, the cans were opened and the granulate offered to the fish. In Lake Malawi JBL NovoRift (250 ml) and JBL NovoGranoMix (250 ml) was fed at a depth of 10 m. The cans were filled with water at the surface and opened again at depth.

Underwater feeding trials - Results

Indian Ocean: Anthias and butterfly fish are still “difficult” candidates. Their natural food is so special (plankton or coral polyps), that getting them used to any replacement food takes a long time. All (!) other fish species immediately consumed the JBL food, although feeding had never been attempted on this reef because of the large number of sharks. Lake Malawi: It was observed that cichlids preferred food with fish protein to “green food”. However, this is not surprising. Fish protein is a rarity for the algae growth eaters and is regarded by them as a treat. Algae growth is available in practically unlimited quantities and therefore green food is not especially attractive to the fish.

Humidity and temperature measurements on land

The relative humidity and the temperature in the shade were measured using the JBL TerraControl hygrometer and thermometer. In order to carry out the measurements at night, a camera (Canon 30D) was connected to a Canon remote control release (TC 80 N3) which took a photo every 2 hours. In order to assign the photos to a time, a wristwatch was photographed at the same time. As in measurements taken previously in the Amazon rainforest, the difference between day and night is relevant. This should always be taken into consideration when keeping terrarium animals.

Time  Relative humidity in %   Temperature in °C 
07:43 52  22 
11:38 34  29 
17:42 39  27 
18:42 39.5  27 
19:42 40.5  26 
20:42 40.5  26 
21:30 40.5  25 
23:30 40.5  25 

Humidity measurements - Hluhluwe Nature Reserve, 13.09.2006

Time  Relative humidity in %   Temperature in °C 
 morning: 07:00  76  18 
 midday: 11:30  41  33 
 evening:17:50  67  19 

Shark school

The world-renowned shark experts, Andy Cobb and Dr. Erich Ritter, gave lectures to the JBL Team. Andy Cobb lives in Durban and is considered the most experienced specialist in sand tiger sharks. In order to observe sand tiger sharks in peace, it is important not to actively approach the sharks, but to wait until the sharks extend their swimming circles and approach the divers. This could be confirmed later on the dives in Aliwal Shoal. Dr. Erich Ritter prepared the team for their encounters with the great white sharks and lectured on the topic of the body language of the shark. In over 6000 encounters with sharks, Dr. Erich Ritter has gathered an immense wealth of knowledge of sharks and passes this on with humor and understanding. Erich Ritter´s observations of white sharks give interesting insights, even these shark do not eat fowl. After chewing for a short time, a seagull was quickly spat out again! The rule: Like eats like doesn´t only apply to aquarium fish.