Tag Archives: low tide

July 13 and 14 – Weekly Census

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Ecological Notes:

  • The sea lion population is growing. For the past few days there have been 18 Steller sea lions hauled out on Middle Rocks. That is up from four sea lions one week ago. One of the sea lions has a brand. It appears to say 620R, although the researcher I contacted in Oregon mentioned it is what they call a bad brand and he was unable to determine the brand from the photos I sent. I will keep a look out for the sea lion and see if I can get a better view. The researcher will check his records to see if he can identify the sea lion and be able to record the resighting.
  • The super moon on Wednesday night rose in the southeast at 10:00pm. It was a big bright orange orb that looked more like the rising sun, than the moon.
  • Today’s extremely low tide of -0.2m or -0.7′ was at 10:13am. The overnight high tide at 00:55am was 3.0m or 9.8′. It is apparently the lowest tide in a decade. I was fascinated to see the extended edge of the water all around the many islands. I looked at the exposed intertidal zone from a distance and up on the jetty, so as not to disturb the many delicate species.
  • See the photo gallery below for more ecological happenings from the past two days.

Weekly Census Results from July 13:

  • Steller/Northern sea lions: 18
  • Sea otter: 1
  • Harbour seals: 133
  • Bald eagles: 2 (1 juvenile and 1 adult)
  • Canada geese: 9 (5 adults, 4 goslings)
  • Black oystercatchers: 11 (8 adults, 3 chicks)
  • Cormorant: 4
  • Glaucous-winged gulls nesting on the main island: 247
  • Glaucous-winged gull chicks: approximately 200 (it is hard to get an exact number due to their camouflage in the grass and hiding under their parents)
  • Gulls not nesting (some glaucous-winged and some other species) on the south end of the main island and outer islands: 96
  • Pigeon guillemots: 142
  • Black turnstones: 2
  • Western sandpiper: 2

Weather:

  • Yesterday (July 13):
    • Sky: Part Cloudy
    • Wind: W 12-32 kts
    • Sea: rippled, then up to 3′ waves in afternoon and evening
    • Temperature Low 12oC, High 16oC
  • Today (July 14):
    • Sky: Part Cloudy
    • Wind: W 15-27 kts
    • Sea: rippled, then up to 2′ chop in afternoon
    • Temperature Low 11oC, High 13oC

Visitors:

  • No visitors

Facility Work:

  • Scrubbed and squeegeed solar panels, routine tidying and checking infrastructure around the island.

Vessel Traffic:

  • Many Canadian and American ecotour boats have been nearby and heading through the waters of the ecological reserve.

Here are photo highlights from the past two days. Click on the photos for larger views and captions.

August 18 -More Sea Lions

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Wind: W 15-29 knots
Sea State: up to 0.5m chop
Visibility: 10-15 NM
Sky: clear in morning, partly cloudy beginning in early afternoon
Temperature: 14-19 °C
Atmospheric CO2: 412.58 ppm (recorded by NOAA at Mauna Loa Observatory, Hawaii)

The groups of steller and california sea lions around the main island and on Middle Rocks have all increased in number. There were two noteworthy sea lions today. In the afternoon, I noticed a lone steller sea lion near the end of the jetty. It had a white and red flasher (fishing lure) hooked to its mouth. Unfortunately, this is a sight that is occasionally seen here. Just last week there was another steller sea lion with a pink and yellow flasher. That sea lion (branded O-19) has not been spotted since. The flashers could have had a fish hooked on the end, which was eaten by the sea lion, or the lure could have appeared to the sea lion to be a fish. The sea lion this afternoon, left the jetty when a large boat went by. A few minutes later, it appeared on Middle Rock where a group of about thirty sea lions were hauled out. I will keep an eye on this sea lion. If it stays around for a few days, it could be a candidate for a rescue from the Marine Mammal Rescue Centre.

When I spotted the sea lion with the flasher haul out on Middle Rock, I noticed a steller sea lion branded 975R. The R means it was branded at Rogue Reef, in Oregon. This animal has been seen here before. See Ecoguardian Anne Stewart’s post from April 6, 2015. The steller was branded as a pup in 2011.

There were about twenty-five eco tour boats that passed through the Ecological Reserve today, some of them repeats. They appeared to be viewing the hauled out sea lions, harbour seals and the floating in the kelp sea otter.

See the photos below for sights and happenings from today:

March 4 and 5

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Wind: yesterday 2-42 knots variable directions, today 0-31 knots from N in am and W in pm
Sea State: yesterday chop up to 1 m, today rippled then up to 1 m chop in afternoon
Visibility: yesterday 10 NM, today 5-15 NM
Sky: yesterday clear, today partly cloudy and rain in afternoon
Temperature: yesterday 5-10 °C, today 5-9 °C
Atmospheric CO2: 413.05 ppm (recorded by NOAA at Mauna Loa Observatory, Hawaii)

The tide has been getting low in the evenings over the past two days, revealing lots of neat intertidal creatures. With no sea lions hanging out on the east side of the island, I was able to explore the rocky shoreline to see feather duster worms, sea stars, barnacles, surf grass, many types of seaweeds and long ago discarded metal pieces from former buildings and equipment at the lightstation that only reveal themselves at low tide.

There are six very stationary elephant seals on the island: one adult female, two adult males, two female pups and one male pup.

Today, I drained the cistern which stores the seawater before it gets treated by the desalinator. The cistern is a large concrete box located between the lighthouse and the main residence. It measures 12 m long by 8 m wide by 3 m deep. It holds a lot of water. The water was slightly turbid and causing the desalinator pre-filters to work harder than needed. The water pump ran for four hours to drain the many thousands of litres of water back into the ocean. I used a long pressure washing wand to reach in to clean the rocks on the bottom and concrete walls, at least the parts I could reach. Tomorrow, I will refill the cistern when the tide is higher and the intake hose can be put off the end of the jetty.

Yesterday morning, six visitors came to the island: Travis, Hilary, Antoine, Hannah, Val and Greg. There was one tour boat that passed by. Today, two tour boats were in the ecological reserve in the morning.

The Tidal Cycle at Race Rocks and the Abiotic Effects of Tides

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At Race Rocks we have a tidal range of about 3 metres.

For tidal Level predictions , from the closest station at Pedder Bay see this link

https://tides.gc.ca/en/stations/07080/predictions

 

 

 

The link below is for the Race Passage Current tables.  .. See this file for the result of original work done by Pearson College Divers assisting the Institute of Ocean Sciences in the deployment of the current meter to gather a year’s worth of data from which these tables are constructed. 

 

 

 

 

 
Marine Science teacher at Pearson College Laura Verhegge was interviewed on CBC radio about what was a “Negative tide”. Listen below.

 

The role of the moon is a major factor in determining the rise and fall of the tides.The view of it from Race Rocks in a full sky is often stunning. 

And of course the other component causing tides is the sun. See this file for Solar energy records for Race Rocks .  

 

 

See this file for the Abiotic Effect of Solar energy on Organisms at Race Rocks

 

 

THE ABIOTIC EFFECTS OF TIDAL LEVEL CHANGES:

The rich variety of life in the intertidal zones of Race Rocks provide habitat for many animals which have adapted to living part of their life exposed . “ANITA’S ISLAND” on the West side of Great Race Rocks provides an excellent example,  in the month of June when the tidal level often drops below zero datum so one can really appreciate the effects of the daily changing tidal levels on intertidal life. This island is actually a peninsula which you can walk out onto when the tides drop to -0.0m, but is totally submerged at high tide, (around 2.6 meters). You can often see the top of it from remote camera1  ( It looks black because it is covered with mussels.)

For several years in the 1990s  we did research with Dr. Anita Brinckmann-Voss on these low tides in June. We only had a half hour or so until the isthmus joining the island to Great Race Island was flooded however. Each year that we went out, Anita found a great many of the hydroid samples from which she identified for the Ecological Reserve.  

THE INTERTIDAL ZONE: The island is totally covered on every square centimeter with some form of life, either invertebrate or plant.

    • Those organisms nearer the top or in the high intertidal area, are more resistant to changing temperatures, and changing salinity. Exposure in a rain storm means they have to tolerate fresh water, and changing salinity.  On a hot sunny day , the surface temperatures can elevate quickly. 
    • Other hazards of this habitat between sea and land create an extreme environment for survival. Predation from Birds and other animals is possible when exposed at low tide , wheres the same organisms are exposed to predation from fish and predatory invertebrates such as sea stars when the tide is in. 
    • This zone also makes the organism vulnerable to pounding waves and surf, so built in resilience is necessary to hold on and remain attached , and not be crushed by the force of the water.
  • Living in this zone also leaves an organism exposed to wind driven foreign objects.. At Race Rocks drifting logs are often present on the surface and these can exert a powerful force when striking a shoreline, 
RESEARCH ESSAYS: The implications for an organism living at different elevations on the intertidal zone are very significant. Over the years several students have done research in the intertidal zone at Race Rocks and have examined how different organisms have adapted. Check this file for examples 
TIDEPOOLS: In our tidepool file , you will find an index with links to a set of tidepools where we have recorded the effects of the tide being out for different lengths of time. The abiotic conditions in the pools change significantly as the tide levels go up and down. Salinity and Temperature are especially variable and they influence the type of organisms that lives within the pools.
Intertidal TRANSECT Studies.We use transects to quantify the interrelations of organisms as they are distributed throughout the intertidal zone on the shore. Tidal levels are a major factor in determining this zonation. In this file you are invited to examine some of our data, and create your own transect baseline studies as well. They may have nothing to do with tides, but they can serve as an excellent record which you may use to base measurements showing change or stability of the ecosystem in the future
The Effects of CURRENTS. 

Tidal Currents are also a result of the tidal cycle . This file documents aspects of the currents at Race Rocks

Other tidal heights from along the coast of Vancouver Island and British Columbia

An interesting exercise is to compare the tidal heights at several locations around Vancouver Island. There is a significant difference, with times as well as tidal ranges varying depending where the station is located. There are many factors which determine tide levels, the most obvious being the stages of the moon and the position of the sun, but here you can see that geography has a major role to play as well.

Tidal Cycle at Race Rocks Video

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 This clip was produced on 8.11.2002. As Race Rocks Marine Protected Area is a place where large (3 meter) tidal range occurs, it is a good location to observe the raising and lowering of the water . A rock in Race Passage near the West shore of Great Race Rock was chosen and a camera was installed in front of the window of the research room in the Marine Science Centre. Video clips were taken for 15 seconds every hour of daylight, high tide occurred during noontime. The second part of the clip shows the tide going in fast motion, a day at the rock passes in 25 seconds.” Jeremias Prassti, ( PC yr 28)

From Victoria Tide tables for this date.. 8.11.2002. :

time… tidal height (ft)………….(meters)
0910 …………………..8.9……………..2.7
1100………………….. 8.5……………..2.6
1445………………….. 9.2……………..2.8
2345………………….. 1.0………………0.3

PROJECT IDEA:
1. On graph paper, using the data above, plot the tidal variation for the day. Then pause the video on each of the levels, measure the height of an exposed piece of the rock and then plot it on the graph. In this way you should be able to determine the elevation of the top of the rock.

2. Link to the physical factor page for Race Rocks – Go to the Tidal calculator links available and compare the shape of the graph for November 8, 2002 with the graph you have made here