Background Knowledge
Learn more about algae, chlorophyll and fluorescence
Algae in water – small but important
Algae are a natural component of many bodies of water. They are found in lakes, ponds, rivers and seas, where they fulfil an important function within the ecosystem. At the same time, an excessively high concentration of algae can indicate changes in water quality. It is therefore worth regularly monitoring and measuring algae levels in the water.
What are algae?
Algae are a diverse group of mostly simple organisms that live in water or on damp surfaces. Many algae are microscopically small and cannot be seen with the naked eye. Others, such as larger green algae, can, however, be clearly visible.
Algae contain pigments such as chlorophyll. This enables them to absorb light energy and use it for their growth. This is precisely where photosynthesis comes into play.
What is photosynthesis?
During photosynthesis, algae – much like plants on land – use light, water and carbon dioxide to build up energy-rich organic compounds. This process produces oxygen, which is released into the water.
Put simply: Light + water + carbon dioxide → organic compounds + oxygen
Photosynthesis makes algae important producers in aquatic environments. They form the basis of many food chains and contribute to the oxygen supply in the water.
Why should you measure algae in the water?
Algae are not, in themselves, anything unusual or harmful. Problems can arise, however, if they multiply rapidly. A high concentration of algae can be caused, for example, by an excess of nutrients such as phosphorus and nitrogen. Temperature, light and other environmental conditions also play a role.
Significant algal growth can have various consequences:
- The water may take on a greenish tinge or become cloudy.
- When large quantities of algae die off and decompose, a great deal of oxygen can be consumed.
- This can lead to a reduction in the oxygen supply to the water body.
- Certain algae or cyanobacteria can produce problematic substances under favourable conditions.
- An increasing concentration of algae may be an indication of changes in the water body.
Regular monitoring therefore helps to detect changes at an early stage, track developments and, where necessary, take appropriate action.
What does an algae measurement tell us?
An algae measurement provides information on how much algae, or algae biomass, is present in the water. Depending on the measurement method, different parameters can be recorded.
For example, the chlorophyll-a content is often determined. Chlorophyll-a is an important component of photosynthetically active organisms and is frequently used as a measure of algal biomass.
It is important to note that a single measurement is always just a snapshot. Measurements become particularly meaningful when data is recorded regularly and over a longer period of time. This allows trends to be identified and changes in the water body to be assessed more effectively.
Measuring algae – understanding water better
Measuring algae is therefore a key component of water body monitoring. It links biological processes with measurable data and enables changes in water quality to be detected at an early stage.
Measuring algae provides important insights into the condition and development of a water body.
How does algae measurement work with bbe Moldaenke instruments?
bbe Moldaenke instruments can be used to detect algae in water quickly and reliably. The measurement principle is based on the natural properties of algae pigments – in particular chlorophyll.
The instruments use light to detect algae present in the water. When the measurement light strikes the algae’s pigments, they react in a characteristic way to the light. The instrument can detect this reaction and use it to determine the algae concentration.
Quick measurements instead of time-consuming laboratory analysis
A key advantage of measuring with bbe Moldaenke is that measurements are taken directly in the water. Depending on the instrument and application, algae concentration and other parameters can be measured quickly on site. This gives users an immediate overview of the current condition of the water body.
The measurements can be used, for example, to:
• monitor changes in algae concentration on a regular basis,
• detect changes in the water body at an early stage,
• compare different water bodies or monitoring points with one another,
• observe algae trends over longer periods, and
• initiate targeted further investigations in the event of notable changes.
More than just ‘counting algae’
Modern fluorometers from bbe Moldaenke can utilise the different properties of algal pigments to distinguish between various groups or classes of algae. This allows for a much more nuanced analysis than simply determining the total quantity.
Depending on the measuring instrument used and the application, information can be obtained, for example, on chlorophyll-a, algal classes and cyanobacteria.
The measurement method makes use of a specific effect: photosynthetically active pigments can emit fluorescence when excited by light. This fluorescence is measurable and correlates with the quantity and composition of the photosynthetically active organisms in the water.
From measurement to insights into the water body
Measurements taken with bbe Moldaenke instruments thus provide a quick overview of the biological status of a water body. Regular measurements are particularly valuable: if data are recorded over a longer period, trends and changes can be identified.
In this way, a single measurement becomes a meaningful time series – and algae measurement becomes an important tool for the monitoring and management of water bodies.
In short: with bbe Moldaenke, algae in water can be measured quickly, directly and in detail – enabling a better assessment of water quality and the early detection of changes.
Which bbe Moldaenke solution is suitable for which type of algae measurement?
Depending on whether a rapid measurement directly in the water, a detailed laboratory analysis or continuous monitoring is required, bbe Moldaenke offers a range of different measuring instruments.
All solutions are based on a common principle: the measurement of the fluorescence of chlorophyll and other algal pigments. The algae are excited using light of different wavelengths. The resulting fluorescence is detected and analysed by the measuring instrument. This allows algal concentrations to be determined and – with suitable instruments – different classes of algae to be distinguished.
AlgaeTorch – fast and direct measurement in the water
The AlgaeTorch is a compact, handheld measuring device for rapid on-site algae monitoring. The principle is simple: switch on the device, immerse it in the water and take a reading.
The AlgaeTorch determines the total microalgae content as well as the chlorophyll-a content of cyanobacteria (commonly known as ‘blue-green algae’). The measurement is carried out directly in the water and requires no complex sampling or sample preparation. A measurement result is available within a few seconds.
Particularly suitable for:
• regular monitoring measurements in lakes, rivers and reservoirs,
• the monitoring of bathing waters,
• rapid screening for cyanobacteria,
• field measurement campaigns and
• the recording of changes in algae concentration.
In short: the AlgaeTorch is the ideal solution when quick and straightforward on-site measurements are required.
FluoroProbe – Distinguishing between algae classes and creating depth profiles
If you are interested not only in the total amount of algae but also in their composition, the FluoroProbe provides significantly more information.
It can determine the chlorophyll concentration of various algal classes. These include, in particular, green algae, cyanobacteria, diatoms and cryptophytes. The different pigments in the algae produce characteristic fluorescence patterns – so-called ‘fingerprints’. The FluoroProbe uses these to differentiate between the algal classes.
Measurements can be taken directly in the water. This makes it possible, for example, to investigate how algae are distributed at different water depths. Depending on the model, the FluoroProbe can be used at depths of up to 100 m, or optionally up to 200 m. In addition, corrections for yellow substance and turbidity, amongst others, are available.
Particularly suitable for:
• lakes and reservoirs,
• limnological and oceanographic research,
• the investigation of algal blooms,
• bathing water and drinking water monitoring,
• depth profiles and
• detailed analysis of algal composition.
In short: the FluoroProbe is ideal if you want to know how much algae is present, which algae classes dominate and how they are distributed within the water body.
AlgaeLabAnalyser – detailed algal analysis in the laboratory
For analyses under controlled laboratory conditions, bbe Moldaenke offers the AlgaeLabAnalyser.
The instrument determines the chlorophyll concentration and can classify the algae into different groups. Optionally, the photosynthetic activity of the microalgae can also be determined. The measurement is carried out in a 25-ml cuvette and requires no complex sample preparation involving filtration or solvents.
In addition to the standard classes of green algae, cyanobacteria, diatoms and cryptophytes, other specific algal fingerprints can also be taken into account.
Particularly suitable for:
• laboratory analyses,
• scientific investigations,
• routine analysis,
• the examination of algal cultures,
• the determination of photosynthetic activity and
• detailed comparisons of different water samples.
In short: The AlgaeLabAnalyser is ideal when a detailed and reproducible analysis of water samples is required in the laboratory.
AlgaeOnlineAnalyser – continuous monitoring
Where a one-off measurement is insufficient and algae growth needs to be monitored continuously, online systems are used.
The AlgaeOnlineAnalyser II enables the online determination of chlorophyll concentration, algal classes and photosynthetic activity in a flow-through configuration. The device is designed for simple, low-maintenance operation
Particularly suitable for:
• continuous water monitoring,
• monitoring stations,
• waterworks and drinking water monitoring,
• process monitoring,
• early warning systems and
• applications where changes need to be detected as early as possible.
In short: online systems are the right solution when the aim is not just to take occasional measurements, but to monitor algae development on a continuous basis.
But what if the algae are growing on a substrate?
Not all algae float freely in the water. So-called benthic algae can grow on stones, sediments or other surfaces.
The BenthoTorch was developed for this application. It measures chlorophyll-a fluorescence directly on various substrates and can distinguish between green algae, cyanobacteria and diatoms. A single measurement takes around 20 seconds.
Particularly suitable for:
• investigating algal growth on rocks and sediments,
• ecological water assessments,
• field measurements and
• the rapid assessment of benthic algal biomass.
The right measurement technology for every application
Whether it’s a quick on-site measurement, a detailed laboratory analysis or continuous monitoring – with the various bbe-Moldaenke instruments, algae measurements can be tailored to the specific application.
| Question | Suitable solution |
| How much algae is currently present in the water? | AlgaeTorch |
| What is the proportion of cyanobacteria? | AlgaeTorch |
| Which classes of algae are present? | FluoroProbe / AlgaeLabAnalyser |
| How is the algae distributed across the water column? | FluoroProbe |
| How active are the algae in terms of photosynthesis? | AlgaeLabAnalyser / AlgaeOnlineAnalyser |
| How is the algae concentration changing over time? | AlgaeOnlineAnalyser |
| How much algae growth is there on stones or sediments? | BenthoTorch |
The common principle: measurement using fluorescence
Despite their different areas of application, the instruments are based on a common fundamental principle: living algae possess photosynthetically active pigments. When these are excited by suitable light, fluorescence is produced. This fluorescence can be measured and analysed.
This transforms a property invisible to the human eye into a measurable signal. Depending on the instrument, this can be used to determine the chlorophyll concentration, the algal biomass, the distribution of different algal classes or even photosynthetic activity.
In this way, bbe-Moldaenke instruments enable a rapid, direct and, as far as possible, straightforward analysis of algae – from individual field measurements to the continuous monitoring of a body of water.