Calculate plankton concentration and density from sample counts using microscopy counting methods for marine and freshwater samples.
Plankton Density
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Density per Liter
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Estimated Biomass
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Concentration Level
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Marine plankton typically have higher salt tolerance and different size distributions compared to freshwater species. The calculation methods are similar, but typical concentration ranges and biomass estimates vary between environments.
The volume counted depends on your counting method. For hemocytometers, use the chamber specifications (typically 0.1 mL). For Sedgwick-Rafter chambers, the standard volume is 1 mL.
Dilute samples when cell density is too high for accurate counting (typically >500 cells per field). Use serial dilutions and multiply your final count by the dilution factor.
Use hemocytometers for small phytoplankton, Sedgwick-Rafter chambers for larger organisms, and inverted microscopes for detailed taxonomic studies. Each method has specific volume calculations.
Biomass estimates are approximations based on average cell volumes and carbon content. Actual biomass can vary significantly based on species composition, cell size, and physiological state.
Marine waters typically range from 10³ to 10⁶ cells/L, freshwater lakes from 10⁴ to 10⁷ cells/L, and brackish waters fall between these ranges. Seasonal and geographic variations are common.