BC lake · 75 ha · Campbell River watershed

Merrill Lake

Its median summer total phosphorus over 2016–2019 was 12 µg/L, from 15 readings. Higher than 63% of the 95 BC lakes with enough recent readings. It lies in Strathcona, Electoral Area A.

The readings

16 summer readings from open water on record from 1996 to 2019, at 2 sampling sites.

	Median since 2012	Compared with BC lakes
Total phosphorus	12 µg/L 2016–2019, 15 readings	Higher than 63% of the 95 BC lakes with enough recent readings.

Total phosphorus the nutrient that most often feeds algae in BC lakes

Median each year (bigger dot, more readings)Middle half of BC lakesBC median

Source: BC Environmental Monitoring Data System (EnMoDS) results, Environmental Monitoring and Analysis Branch, Province of BC, records to September 19, 2026 (Open Government Licence – British Columbia); lake outlines and names: Freshwater Atlas lakes, Province of BC (Open Government Licence – British Columbia). Summaries by PlaceDossier.

Nutrient level Inferred

Reads as mesotrophic (moderate nutrients and algae).

	Index	Class
From total phosphorus (12 µg/L, 2016–2019)	40	mesotrophic

Inferred by us, not a provincial classification. The index was built for summer readings from the middle of a lake; ours mix sites and months, so treat the class as a rough guide.

How we worked this out

Carlson's trophic state index (Carlson 1977, Limnology and Oceanography 22:361) turns each median into a score: 60 − 14.41 ln(Secchi m), 14.42 ln(phosphorus µg/L) + 4.15, 9.81 ln(chlorophyll µg/L) + 30.6. Classes after Carlson and Simpson (1996): under 40 oligotrophic, 40 to 50 mesotrophic, 50 to 70 eutrophic, 70 and over hypereutrophic.

Year by year

Year	Total phosphorus
2019	5.0 µg/L (2)
2018	6.9 µg/L (5)
2017	12 µg/L (5)
2016	12 µg/L (3)
1996	3.0 µg/L (1)

Median of each year's May to October readings; the number of readings is in brackets.

Where it was sampled

E306174 Merril Lake deep station 15 readings
E223558 Main site 1 reading

Site names are tidied from the provincial records; the IDs find each site's full record there.

What this record doesn't cover

Algae bloom reports and invasive mussel checks aren't in this record: the province's Algae Watch map and mussel monitoring aren't published as open data. For swimming, check the regional health authority's beach advisories; for blooms and mussels, ask the province's regional environment office or the local lake association.

Readings are from the province's monitoring database: samples taken by provincial staff, volunteer lake monitors, and companies and local governments that sample under their permits. We keep the ice-free season (May to October), and for phosphorus and chlorophyll only samples from the top 5 m. We leave out sites whose names put them at a water intake, a sewage or industrial outfall, a mine, or a permit holder's works or the water receiving its discharge, or on the shore (a beach, dock or boat launch): water there can differ a lot from the open lake. Each year's figure is the median of that year's readings. We give a lake a summary, a comparison with other lakes and a nutrient level only when it has at least 10 summer readings from open water, spread over at least 3 different years, since 2012; the summary is the median of those readings. With fewer, or only older ones, we show the readings and say there are too few to judge the lake. A reading below the lab's detection limit counts at that limit. One site can be a bay rather than the open lake, so a lake's figures can differ from one end to the other.

Water quality changes with the season, the weather and the part of the lake. These are past readings, not a test of the water today: before you buy, ask the local government and the lake association what's known, and test a drinking-water intake yourself.