Water testing at London Zoo

We like to highlight our customers’ operations in order to demonstrate water quality requirements in different processes. With one of the largest collections of aquatic life in the UK, the aquariums at the Zoological Society of London create some interesting water quality demands.​

Zoological Society of London (ZSL) is a charity with a long and distinguished history in animal protection and conservation. Its headquarters in Regents Park in the centre of London has been there since 1828 and is the site of one of the most famous and oldest zoos in the world, London Zoo. ZSL London Zoo itself has over 18,000 animals across 712 different species on the one site and one of the largest collections of aquatic life in the UK, including fish and amphibians. The aquatic organisms spend all or most of their entire life in water, and therefore ensuring the quality of the water is appropriate for the animal is incredibly important.

Marine life at London Zoo aquarium

One slight change in the conditions can be detrimental to a species, making regular testing critical. The aquarium at the Zoo operates over 3 different halls, each with a different range of aquatic life; seahorses and freshwater habitats, Indo-Pacific coral reefs and Amazon. Each environment has unique water quality requirements. Protecting some of the world’s most rarest species requires the most reliable water testing technology available. The aquarium team ensures a safe aquatic environment by utilising the Photometer 7100 for monitoring chlorine, alkalinity, phosphate, ammonia, nitrite, potassium and pH in each of these halls. The herpetology team also use the Photometer 7100, as well as electrochemical products such as the Micro 600 pH meter and a Micro 800 DO meter, as part of their water quality monitoring protocol.

London Zoo employee using a Palintest water testing kit

The feedwater for the facility is provided by Thames Water. This includes chlorine which must be removed before it comes into contact with any of the aquatic life. At the zoo, much of the water is treated via reverse osmosis (RO) and then remineralised to ensure control of the water quality habitats. Furthermore, chlorine analysis of the feedwater prior to the RO is critical for the protection of the RO membranes. Alkalinity is a way of measuring how a body of water will change on the addition of an acid or an alkaline substance. The more alkalinity in a system, the less responsive that body of water will be to the addition of acids or alkalis. Higher alkalinity is generally preferable to low alkalinity in aquariums so the system is less sensitive to fluctuations in pH. Aquatic life is very sensitive to pH changes and maintaining a good alkalinity level helps maintain a stable environment.

Phosphate testing in aquatic environments is important, especially where coral is concerned. Phosphate inhibits calcification in corals at higher levels – coral reefs have to be maintained in a nutrient poor state.

Phosphate levels are particularly important to monitor in the coral section of the zoo. Coral is predominantly made up of calcium and excess phosphate prevents the uptake of calcium by the coral. Levels must be maintained below 0.1 mg/L.

Ammonia is a waste product of aquatic life and is poisonous to fish, it is broken down by bacteria to nitrite as part of the nitrogen cycle. Nitrite is also hazardous for aquatic life so measuring ammonia and nitrite are essential in understanding the aquatic ecosystem.

A frog swimming in clear water

Lake Oku Clawed Frog Conservation Project

As part of their conservation work, the herpetology section at ZSL London Zoo became the first place in the world to breed the Lake Oku Clawed Frog. This species of frog is incredibly rare and can only be found in the wild in one high altitude crater lake in Cameroon.

The breeding programme at the zoo was groundbreaking as the reproductive biology of the Lake Oku frog was unknown and the keepers had to replicate the specific environmental parameters of Lake Oku.

Primarily using the Palintest Micro 800 DO meter but also the Photometer 7100, the keepers were able to determine that the tadpoles only thrived in an unusual aquatic environment. The findings from the study at the zoo, which were published in Amphibian and Reptile Conservation in 2015 showed that the young frogs only thrived in an environment that contained less than 20 ppm TDS.

In their natural environment in Lake Oku, Cameroon, TDS levels were <10 ppm indicating that this particular species of frog has evolved only to thrive in a single and stable environment.

Images courtesy of ZSL London Zoo

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