Måling af antallet af blågrønalger

Hej,
Jeg sidder her med en biologi aflevering, hvor jeg skal besvare dette spørgsmål:
Hvordan kan man måle antallet af blågrønalger i en prøve, diskuter problemer med målinger af antal og mulige løsninger.

For at besvare spørgsmålet skal jeg læse denne tekst, men selvom jeg læser teksten, så ved jeg stadig ikke, hvordan spørgsmålet skal besvares. 

Håber der er nogle, der vil hjælpe, tak. :)

(Tekst)
Measuring Blue-Green Algae:
Blue-green algae, or cyanobacteria, are the only phytoplankton that contain phycocyanin and phycoerythrin, making the pigments good indicators of the amount of cyanobacteria in a body of water. While chlorophyll measurements can be used to estimate entire phytoplankton populations en masse, the accessory pigments phycocyanin and phycoerythrin can be measured to estimate cyanobacteria concentrations specifically. Marine cyanobacteria have higher levels of phycoerythrin, while freshwater species have dominating amounts of phycocyanin. Like chlorophyll sensors, blue-green algae sensors rely on fluorescence to detect the pigment concentration. Phycoerythrin sensors use a wavelength around 540 nm, while phycocyanin sensors emit a wavelength at 600 nm. Due to the differences in secondary pigment concentrations between species, it is recommended to use the phycocyanin BGA sensor in freshwater applications, and the phycoerythrin BGA sensor in saltwater.