Ocean Water Samples

Ocean Water Samples

One of the duties of a lighthouse keeper on some stations, was to do a daily Sea Water sample. It was started very early on (see the story here), before the advent of Global warming, and the observed data has been beneficial in many ways as you will see at the bottom..

Kains Island (Quatsino) lighthouse

In the above-mentioned story from Kains Island lighthouse, the samples started in 1935, so we have seventy-seven (77) years of ocean data. Also in the story is the fact that in the early years . . . 

. . . the small glass bottles of sea water with cork stoppers were stored in wooden boxes with many little squares, one for each bottle1. These boxes would be shipped out when the supply ship re-supplied the station once a year, usually in July. 

At the same time the ship would bring a year’s supply of empty bottles.

The sample bottles were something like these

The water sample was taken one hour before high tide every day during daylight hours. The keeper would would wander off down to the shoreline at a designated spot and throw a weighted bucket on a long rope into the ocean. He would wait for the bucket to sink and then haul it in quickly. Still at the shoreline, he would drop a thermometer into the collected water, wait, and then read and record the water temperature. Removing one of the empty small bottles from his pocket, he would dip it in the water bucket, fill the bottle, and cork it. Later he would label and date the bottle, and insert it into that month’s box in the proper order.

In the wintertime, this process could be a very dangerous duty. The tides on the BC coast average 7 meters (22 feet) twice a day sometimes, and this combined with a winter storm swell makes standing on the shore fishing dangerous, let alone standing there for many minutes while you try and get some water into a wave-tossed bucket. You are alone, and if you ever fell in, you might as well kiss your ass goodbye as they say.

One keeper I knew on Egg Island lighthouse installed a steel cable on steel posts down to the water, to which he clipped himself with a lanyard from his safety belt. At least he would not fall in, but if a large wave came he would be severely injured.

I remember one time when I went down to our  water sample place on McInnes Island lighthouse. There were concrete stairs there built by a former keeper. Just as I was to go down the stairs to the edge of the water, about 30 meters (100 feet) distant, a large swell and sea combined, more than 3 meters (10 feet) deep washed completely across the pathway to the water. I was standing in water at the top of the stairs. If I had been on my way there, or returning, I would have been washed away.

After that experience I asked permission to make the samples off the highline cable instead. Permission granted when I explained the circumstances. With this method I lowered and retrieved the bucket via the highline and did the temperature readings in a safe place on the boat landing. It did not affect the averages at all.

Hydrometer jar, thermometer, hydrometer - www.marinebio.net

In the years I was doing the water samples (1974 – 2001) we used a rubber bucket with a weighted bottom (to help it sink). We also did the temperature and the density measurements at the lighthouse. No more sending in little bottles – only a thermometer, hydrometer, hydrometer jar, and a blank printed page to record the data. It made it faster for the technicians to receive the monthly data.

There was only one problem with this – clumsiness! Those glass hydrometers had such a small glass neck that they were always getting broken. We kept several on hand as replacements. 


Now what did the scientists do with this data? Besides knowing the temperature and density of the water at different locations around the coast, the data has been used for providing proof of Global Warming. (check the readings from the BC lighthouses here at the Fisheries and Oceans website).

In one unusual circumstance the readings were used to forecast the arrival of migrating salmon returning to their spawning grounds on the Fraser River.

Canada and the USA get together annually to decide how many tons of salmon will be allowed for each country’s fish boats.

map provided by: www.worldatlas.com

One year the marine scientists noticed that water temperatures were more favourable for the Fraser River salmon coming north around Vancouver Island rather than into the normal Juan de Fuca Strait2 and being split between American and Canadian boats.

The Canadian negotiators allowed the Americans to believe the salmon were coming in from the normal Juan de Fuca Strait route, and consequently harvested their allowed percentage from the northern run which was off limits to the Americans, while the Juan de Fuca run was poor. (Map used with permission of WorldAtlas. The Juan de Fuca map page lists more information about the strait).


1 One of the tales I heard in my early days on the lighthouse was about the little bottles. if you had 31 bottles to fill in a month, then why not make one sample and fill ALL the bottles with the same sample? Then give a different sea temperature for each sample. Not realizing why the samples were needed in Victoria, the keeper had no idea that the density of the salt water was measured there. If the samples were all the same density every day for a whole month, then they all came from the same sample3. The technician wrote the keeper back and said that at least he could have pee’d in some of the samples to change the density! It never happened again.

2 The Strait of Juan de Fuca (called Juan de Fuca Strait in Canada) is a large body of water about 95 miles (153 km) long that is the Salish Sea outlet to the Pacific Ocean. The international boundary between the United States and Canada runs down the center of the Strait. – Wikipedia

3Temperature and rainfall varied the density of the seawater daily – sometimes not by very much, but different.

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Retired (2001) British Columbia lighthouse keeper after 32 years on the lights.

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