FAQ General Knowledge

Phytoplankton are microscopic organisms that live in water and use sunlight to produce energy through photosynthesis. They are an important part of aquatic ecosystems because they form the base of the food web and produce oxygen.

Phytoplankton include many different types of organisms, including microalgae and cyanobacteria (blue-green algae). Therefore, phytoplankton and microalgae are not exactly the same, although the terms are sometimes used interchangeably.

In simple terms, microalgae are a major group of phytoplankton, while phytoplankton is a broader term that describes microscopic, mostly photosynthetic organisms that drift or float in aquatic environments.

High levels of nutrients such as phosphorus, nitrogen, and silica, together with certain climatic conditions, can promote the growth of microalgae. When these organisms grow rapidly and reach high concentrations, algal blooms can develop. These blooms can cause serious ecological and economic damage.

As algae die and decompose, they can consume large amounts of oxygen in the water. This oxygen depletion can negatively affect aquatic life. In addition, some species can produce toxins that are harmful to humans and animals. Toxic blooms caused by algae and cyanobacteria are known as harmful algal blooms (HABs).

Human activities can make these problems worse. For example, sedimentation and artificial eutrophication, often caused by pollution from both specific and diffuse sources, are becoming more common worldwide. These processes can be particularly strong in tropical environments. Seasonal changes, including hot and humid summers followed by cooler and drier winters, can increase nutrient uptake and support the rapid growth of algae and aquatic plants.

Because some algae can produce harmful toxins, their presence in water is a serious concern. Early detection and continuous monitoring of algal growth are therefore important for protecting water quality and public health.

Algal blooms and changes in nutrient levels can also cause important water quality parameters to move outside their normal ranges. As a result, reservoirs may no longer be suitable for all of their intended uses. This is a common challenge in large urban areas, where the complex dynamics of aquatic environments make effective monitoring more difficult.

Chlorophyll-a (Chl-a) is a photosynthetic pigment found in phytoplankton. It can be used as an indicator of eutrophication, which makes it an important parameter for monitoring water quality and supporting effective control measures.  There are several methods available to measure Chl-a. The most traditional methods are based on laboratory analysis, such as spectrophotometry and high-performance liquid chromatography (HPLC). These methods can provide accurate and reliable results. However, they require laboratory equipment and several preparation steps. They also use chemical reagents that may affect the algae during the extraction process.

In addition, laboratory analysis can be time-consuming and may require large sample volumes. It can also involve high analytical and logistical costs. As a result, obtaining results can take time, which may delay early responses to changes in water quality. To address these limitations, new technologies have been developed that can provide data in real time.

Among these technologies, fluorescence-based optical sensors are particularly promising. They can measure Chl-a directly in living organisms without destroying the sample. They are also easy to use and can provide fast, continuous measurements with good precision and accuracy.

a comprehensive answer will fill a book that is not yet written today. But here, in short, my comments:

Algae class means an allocation to a distinct class of algae with similar pigment apparatus. The composition of photosynthetic pigments for each class is comparable. The complex pigment apparatus comprehends the chlorophyll a and accessory pigments.  These pigments are used for the trapping of light and thus for energy supply of the cells.  Based on fundamental research we investigated the unique features of the spectrofluorometric fingerprints of microalgae and cyanobacteria.  The classification is related to taxonomical classes as shown in the attached table. With the bbe fluorometer up to 5 different algae classes can distinguish as described in the attachment. The calibration with “standardized” algae and cyanobacteria enables the quantification of the chlorophyll a for each class.

I want to specify this question a little more.  Do the specific algae affect the environment at all and under which conditions? Exactly no one will give an exact answer at this time because of the high complexity of the food chain where different types of organisms interact. Microalgae and cyanobacteria are only an intermediate link in the food chain. Please keep in mind there are microbes like bacteria, microalgae as part of the phytoplankton, zooplankton, fish, etc. Additional factors like sunlight, temperature, salinity make a statement even more difficult. However, when the concentration of one algae class is low, we can expect in general small impacts on the environment as well as on other algae classes determined as chlorophyll a. The situation changes when one algae class becomes dominant. Here we cannot list all the effects and generalize these for a forecast in China or elsewhere.

We can indicate some examples and their impacts on the environment. Like in early spring the diatoms show a strong proliferation. Prominent factors are increasing day time and bright irradiation at rather low water temperature. Here algae from other algae classes cannot compete. But also, microalgae from the same class as dinoflagellates cannot compete as they prefer other environmental conditions. They prefer higher temperatures at summertime where they then compete with other microalgae for the nutrients in the water. The limitation for diatoms comes from the limited pool of silicon which is needed for the construction of the diatom shells. So, after a bloom usually follows a decay of the biomass with the survival of some types of this class in a resting mode. Another well-known fact is the blooming of cyanobacteria. Here a plentiful proliferation suppresses other microalgae for several reasons: the cyanobacteria cover the surface of the water with high amounts of biomass. The light intensity for the photosynthesis of other classes is reduced which lowers their reproduction. Nutrients like phosphorus and nitrogen are bound to the cyanobacterial cells and are no longer or only less available for the other algae classes. This can cause a sink of oxygen in the water body. Another effect is the release of biotoxins. Their effects are known in regard to higher organisms like fish and human beings but not of different algae classes. Here it will be more interesting to look for the microalgae at the level of genus and species. The fluorometric approach helps to sort this and reduces the number of samples for a detailed analysis. When nutrients become exhausted a more serious effect occurs – the death of the blooming cells which leads to oxygen depletion (hypoxia) during accompanied by bacterial degradation. The consequence for all organisms is the formation of dead zones where only some specialists of microalgae can survive.

Roughly generalized: strong growing microalgae or cyanobacteria proliferates at the expense of the other classes if they share the same space and nutrients. They all will affect the environment if present in excess. However, this statement is not enough for an effective monitoring. Especially the dynamics of the ups and down already at low concentrations of the different phytoplankton enables meaningful information in regard to management and taking actions. Here the fluorometric approach provides an unmatched overview of the present status in real-time.

Chlorophyll-a measurements according to DIN 38412-L16 and fluorometric measurements are based on different principles.

The DIN method is an in vitro method. The algae are removed from the water and the chlorophyll is extracted before it is measured.

Fluorescence measurements, on the other hand, are performed in vivo. The fluorometer measures chlorophyll directly in living cells, providing information about the chlorophyll that is currently present and active in the cells.

This can be an important advantage. Because the measurement is performed directly on living algae, fluorescence measurements can provide a more direct indication of biological activity and primary production.

During chemical extraction, some cells may already be damaged or dead. In addition, chlorophyll breakdown products such as chlorophyllides can also be detected as chlorophyll.

Chlorophyllides are early breakdown products of chlorophyll and can already form during the extraction process with hot ethanol. When the sample is analyzed by HPLC, these compounds can appear as small additional peaks next to the main chlorophyll-a peak.

For this reason, fluorometric measurements can provide a picture that is closer to the actual condition of the algae in the water, while extraction-based laboratory methods measure chlorophyll after the cells have been removed and processed.