Shelter
Shelter Inlet is the second north-westernmost inlet, located between Sydney Inlet and Herbert Inlet. It runs to the north of Flores Island. Obstruction Island lies between Shelter and Herbert, but they are connected by Sulphur Passage, Hayden Passage and Millar Channel. Several small creeks feed into Shelter Inlet, but the most prominent is the Megin River, which enters the inlet near its head from the north. The largest tributary to the Megin River is Talbot Creek, which joins the lower end of the river before entering the inlet. Watta Creek flows into the head of the inlet.
Clayoquot Sound is an estuary made up of inlets that were carved out by glaciers during the last ice age. Shelter Inlet has a sill at a depth of about 80 meters and a ~10 km wide basin. The inlet is 10 nautical miles long, with a mean width of 0.7 nautical miles, a mean mid-inlet depth of 80 meters, maximum depth of 175 meters and outer sill depth of 25 meters.
Cermaq is a fish farming company with several locations in Clayoquot Sound. One of their salmon pens is located in Dixon Bay, which is just north of Station 74 in Shelter Inlet (see map in the following section). This site was operational as recently as 2018, but it is currently listed as inactive. It was one of the Cermaq sites in the area to not be significantly affected by harmful algal blooms that caused die-offs in 2016 and 2019.
There has also been some logging of old growth forest from 1993-2016 around the the Dixon Bay area and opposite Dixon Bay on Flores Island.
Sampling Conditions
Shelter Inlet had a total of 9 sampling sites (72, 73, 74, 75, 76, 77, 78, 79, 80) at which this data was collected.
Atmospheric conditions at Tofino Airport on sampling date (9/11/2014).
Tides
Nutrients
The following choropleth maps show cross sections of nutrient distributions at the surface of the inlet, the layer where chlorophyll is most concentrated, and the bottom. Nutrients are generally expected to be relatively depleted at the surface where phytoplankton are consuming them at higher rates and densest at the bottom of the inlet where they are sinking and collecting. Nutrient concentrations are given in units of micromolar (μM).
Nitrate (NO₃)
Surface
Low-to-moderate surface nitrate concentration near mouth that starts to decrease past Dixon Bay and stays low up to head of inlet.
Chlorophyll Max
Only station 78 appears for Shelter Inlet at the c-max level regardless of the nutrient. Moderate nitrate concentration.
Bottom
Consistently high bottom nitrate concentration.
Phosphate (PO₄)
Surface
Low surface phosphate concentration. Slightly higher at mouth and head.
Chlorophyll Max
Low-to-moderate phosphate concentration at station 78 near Megin River outlet.
Bottom
High bottom phosphate concentration, similar to Herbert and Sydney. Lower near head.
Silicate (Si(OH)₄)
Surface
Moderate surface silicate concentration, with greater concentrations at the mouth and head.
Chlorophyll Max
Low-to-moderate silicate concentration at station 78 near Megin River outlet.
Bottom
Relatively high bottom silicate concentration, most similar to Herbert. Lower near head.
Water Properties
Temperature
Shelter has relatively low temperatures compared to Bedwell and Tofino. Its temperature range is similar to that of Herbert and Sydney, with a relatively even distribution that only varies dramatically at the surface/near the head of the inlet, where the water is much warmer, and exhibits some vertical stratification.
Salinity
Shelter Inlet exhibits almost uniform salinity, which is consistently higher than both Bedwell and Tofino. It has a similar distribution to Sydney Inlet, which is also almost uniformly near 31.5 PSU. Herbert Inlet comes close, but exhibits a gradient of decreasing salinity from mouth to head . The uniformity would seemingly have something to do with good mixing, seeing that Shelter Inlet has a much lower sill compared to all other inlets, but the high salinity suggests less flushing, which may have something to do with the obstruction of Flores Island between the inlet and the ocean.
Density
Similar to temperature, Shelter Inlet shows a very neatly layered gradient from bottom to top that doesn't increase very much at all. It has a higher overall density than every inlet besides Sydney, which also reaches 24.5 kg/m³ in the basin. However, while the surface/near head layers in Shelter, Sydney and Herbert are all less dense than the rest of the water, Shelter does not decrease in density as much/as dramatically as the other two. Perhaps the river inflow from Watta Creek at the head of Shelter Inlet is not as intense as it is at Herbert and Sydney.
Dissolved Oxygen
Dissolved oxygen shows a less uniform distribution than Shelter's other depth profiles, with layers that have entered from the ocean and haven't been evenly mixed yet. There appears to be more intense vertical stratification at Shelter than at any other inlet, with a very thin surface layer of oxygen-rich water. Oxygen levels at the base of the inlet do not quite get as low as they do at Sydney, Herbert, and Tofino outlets, but it does seem generally a little more depleted than Tofino and Bedwell. This may have something to do with the obstruction of Flores Island.
Fluorescence
Fluorescence indicates the presence of phytoplankton. Similar to all inlets other than Tofino, Shelter has only a small patch of fluorescence near the surface, though it extends further horizontally than those other inlets, and gets up to the 5-10 mg/m³ range where all other inlets besides Tofino max out at the 2.5-5 mg/m³ range. For some reason there is a healthy layer of phytoplankton all along the length of Shelter Inlet that is not present at other inlets, which are more patchy. The pattern of fluorescence indicates that phytoplankton have a preference for living near the surface in the photic zone.
Transmissivity
Transmissivity indicates the presence of solid matter, with lower values (symbolized with a darker color) indicating more "stuff" in the water. There are pockets of matter on the bottom of the inlet and on the surface of the sill, likely decaying organic matter that sunk to the bottom, and a thicker layer at the surface that indicates the presence of phytoplankton. No other inlets appear to have debris collection at the basin, besides maybe Bedwell. The transmissitvity pattern is unlike that of Bedwell, Sydney, and Tofino, which have wide swaths of debris. Perhaps this indicates that Shelter and Herbert are less well mixed.
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