Plankton and Water Chemistry

Since 1992 a boat has gone to fifteen fixed stations about ten times a year and measured what is in the water. The chemistry is still being measured. The plankton is not.

This is the other half of Species Recorded in the Lake. That page can list what is in the lake and cannot state how much of anything there is, because an occurrence record reflects how many people were looking rather than how many organisms there were. This one counts organisms and water chemistry, at known places, on a known schedule.

What was measured, and until when

Every series in the program, as a bar from its first year to its last. The chemistry runs to the present. The two biological series do not.

An amber bar is a series still being measured; a gray bar is a series that has ended. The number after each bar is how many samples are behind it, across all stations and years. A plankton count needs a taxonomist at a microscope, so it is a cost that can be cut from a budget in a way that a chlorophyll assay is not.

Values at each of the fifteen stations, by year

The lake-wide line below is an average of fifteen stations, and the stations are not all alike. Missisquoi Bay and the Main Lake have the highest and lowest values of every measure the program takes. Pick a year and a measure; the color is fixed across the whole record, so a bright station means the same thing in 1994 as in 2024.

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▶ RUN

How much algae there is

Chlorophyll-a, the pigment assay, as the mean of the station means for each year. It measures the amount of algae, not the kind, and it is the series that is still being collected.

Total phosphorus

Chlorophyll and phosphorus compared with bloom reports, by segment

This site already carries thirteen seasons of the Vermont Health Department's cyanobacteria reports, on Cyanobacteria Blooms. Here it is set beside the chemistry. Each point below is one segment in one year: the monitoring stations' mean against the share of that segment's volunteer reports filed at alert level.

Phytoplankton by division, 2006 to 2015

Net phytoplankton biovolume by division, 2006 to 2015. This is the series that can tell a diatom from a cyanobacterium, and it is the one that stopped.

Zooplankton: four series listed

The program's own parameter table offers four zooplankton series from the New York lab, 1993 to 2013: total density, copepods, cladocerans, rotifers. The query tool returns no rows for any of them, at any of the fifteen stations, over any span — asked through its own form and through a request built by hand.

The query tool returns no zooplankton data. Whether those counts still exist somewhere else, in the New York lab's files or in EPA's STORET database, is not known.

Summary of the record