Measuring Phytoplankton
What Is The Study Of Phytoplankton?
The study of phytoplankton, which are the microscopic photosynthesizing organisms that form the foundation of the aquatic food web is called “phycology”. We analyze phytoplankton populations to determine the levels of biodiversity, relative species proportions and quantity of phytoplankton present in the water body.
Why Is Phycological Analysis Important?
The quantity and composition of phytoplankton populations serve as key indicators of the degree of eutrophication and the overall health of the aquatic ecosystem.
In a healthy lake, phytoplankton populations are diverse, with a balance of different species that support a robust biodiverse food web. However, as eutrophication progresses, certain species of toxic cyanobacteria begin to dominate at the phytoplankton level, disrupting the ecological balance, leading to a degradation of water quality.
By monitoring phytoplankton populations, we can assess the severity of eutrophication, track changes over time, and evaluate the effectiveness of our remediation efforts.
This information is crucial for developing targeted bioaugmentation strategies and adapting our management approach to achieve the best possible outcomes.
How Do You Analyze Phytoplankton?
Sampling phytoplankton is a relatively simple process. In fact, we often train clients to collect phytoplankton samples and ship them to the lab themselves to contain costs.
The procedure involves taking water samples from the lake, stabilizing them with a special preservative, and sending them to a laboratory for expert analysis. The laboratory uses microscopy and other advanced techniques to identify the various phytoplankton species present in the samples and quantify their relative abundance.
What Does The Analysis Tell You?
Phycological analysis provides insight into extent to which eutrophication has progressed and how close the lake is to being dominated by toxic cyanobacteria. This information is crucial for developing effective bioaugmentation dosing regimens and other remediation strategies.
Tracking changes in phytoplankton biodiversity and populations enables us to assess the effectiveness of our interventions and adapt our management approach as needed.
Once we observe a shift towards greater biodiversity and a reduction in cyanobacteria abundance, we can infer our efforts are having a positive impact on the ecosystem.
Here are some examples taken from Indian Lake, MO to illustrate the value of phycological data:
Taxonomic Bio-Diversity
Each type or taxa of phytoplankton has its own color. Dark blue is non-toxin producing cyanobacteria and pale blue is toxin producing or HAB “taxa”. Taxa is the technical term for “type of” according to taxonomic classification.
Ideally there should be good biodiversity, with many taxa present and not many HAB taxa.
That is obviously not the case here.
The color code shows us the average of how many of each taxa or species are present across several samples. The bottom left corner of the chart is magnified so that more detail can be seen.
It shows that on average only 5 different species of phytoplankton were identified in May 2021, of which 4 were cyanobacteria and only one was a beneficial algae. So there is no competition for the cyanobacteria, and they totally dominate the lake.
So the first objective in restoring phytoplankton balance and preventing toxic cyanobacteria HABs is to build up phytoplankton diversity by increasing the number of beneficial algae species so that there is competition against the cyanobacteria.
This is achieved by providing micronutrients that bio-stimulate beneficial algae growth. The remediation program to Save the Lake Lifestyle began in April 2022.
The chart shows how the number of species present gradually increased during the first summer of the program so that by September 2022 the total number of species present was 28 of which 18 were beneficial algae.
As the remediation program progressed, in 2023 and 2024 the number of cyanobacteria species held in single figures (blue line). The number of beneficial algae species was maintained at 20 or more (light green line).
This meant that there were 20 times more competitor species to cyanobacteria than there had been in May 2021.
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- Taxonomic Bio-Diversity
Taxonomic Bio-Diversity
We are often asked “How can you digest and bio-dredge away organic sediment, and reduce total phytoplankton levels at the same time? How come the nutrients in the sediment that you digest don’t produce even worse algae blooms?”
The answer lies in the facts that
By measuring zooplankton numbers we can gain insight into how the restoration of the food web happens.
The chart below shows the population counts of two of the lowest levels of zooplankton in the food web hierarchy:
• Rotifers which are prey to
• Arthropods
As the prey numbers increase, the predator numbers follow.
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- Zooplankton
Similarly, when we measure the biomass of each type of zooplankton, we note that the predator biomass increases significantly as balance between predator and prey is achieved.
At this level of the food web, the restoration of populations and nutrient clearance capacity as reflected in predator numbers and biomass is clear.
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