The temperature profile transect of Hood Canal shows cold dense saltwater settling near the bottom of the basin and the warmer freshwater near the surface.  Near the northern entrance sill (station 1)of Hood Canal, the mixing of cold and warm water is more prevalent and the presence of a thermocline is less pronounced.  In the southern half of the basin, a temperature gradient formed due to a lack of efficient water mixing.  This temperature gradient results in a thermocline located between 3 and 8 meters in depth.

The salinity profile of Hood Canal displays efficient mixing of water in the northern half of the basin with no halocline forming.  In the southern half there is a definite salinity gradient with a halocline forming at between 5 and 10 meters.  The sill at the mouth of Hood Canal (station 1) is restricting the water from flowing into the mouth of the canal allowing circulation of the waters to be strong in the northern half.  In the southern half there is no circulation due to the deep fjord basin of Hood Canal, and there is a halocline forming between the saltwater resting beneath and fresh water on the top.

This density profile displays dense, cool saltwater at the bottom in the southern half where no mixing is occurring.   In the northern half dense saltwater is mixing with less dense fresh water.  In the southern half of the basin the cool, more dense saltwater has settled beneath the warmer, less dense freshwater. When comparing the density profile to the temperature and salinity profiles, it is apparent that density is being driven by salinity as opposed to temperature. Due to increased temperatures and tributary inflows (see introductory page) occurring a week prior to sampling, a snow melt originating in the Olympic Mountains to the west of the basin had increased freshwater flow into Hood Canal. Inadequate mixing caused by the basin’s low flushing rate, allows for a thick layer of freshwater to rest near the surface resulting in stratification, particularly in the southern end of the canal.

This transect plot shows the transmissivity profiles reproduced from CTD data from both the northern and southern legs of the Hood Canal cruise.  Transmissivity is related to turbidity in that both are non-discriminant measures of suspended particles within the water column. Percent transimissivity is high  above the entrance sill (station 1) due to turbulence  caused by incoming/outflowing water from the basin. Percent transmissivity near Lynch Cove (station 23) is high and is related to fluorescence resulting from a massive phytoplankton bloom.

This transect plot shows the fluoresence profile of the Hood Canal. Peaks in fluorescence concentration varied from the northern end of the canal to the southern end. Fluorescence peaked at the northern stations between 15 and 20m, whereas the peak in fluorescence amongst southern stations can be observed closer to 10m beneath the surface. This data suggests that nutrient availability and light penetration required by photosynthetic organisms varies amongst the two ends of the canal. A phytoplankton bloom is apparent just beneath the surface of the water near the thermocline along the length of the basin. Phytoplankton are highly concentrated at the southern end of the Hood Canal near Lynch Cover (station 23).

Chlorophyll a concentrations can be compared to the CTD data to determine whether or not field or lab equipment is functioning properly. Fluorescence and chlorophyll concentrations are determined using different techniques that account for photosynthetic pigments present in organisms in the water. The r² value shows a large variation between the two sampling methods, with a moderate correlation when using both the UWT and Trilogy models of fluorometer. The trend line associated with the UWT fluorometer accounts for 64.57% of the variance between the two sampling methods. This value is higher than the cholorphyll data produced by the Triology fluorometer which accounts for only 41.93% of the variance between the two sampling methods.  Due to the fact that the research team has had issues with both fluorometers used to analyze discrete samples of chlorophyll a, there is a large probability that the discrete samples did not produce reliable data and that the CTD made more precise measurements. The Trilogy fluorometer began malfunctioning while processing the samples from the northern leg of the trip, and ultimately was not used to measure chlorophyll a concentrations when standards were required between most samples.

This figure compares the data produced by both the UWT and Trilogy fluorometers to one another. The trend line accounts for nearly 54% of the variance between the data from each fluorometer. This moderate correlation suggest that the two fluorometers were not functioning the same and suggests that one of the fluorometers, most likely the Trilogy model, was malfunctioning. 

This transect plot displays the dissolved oxygen profile of the Hood Canal. At all stations along the length of the Hood Canal, dissolved oxygen concentrations increase beneath the surface before rapidly decreasing with increasing depth. These low concentrations are a result of insufficient outflow of water from the Hood Canal basin of the Puget Sound. Due to the fact that water remains within this basin for extended periods of time, highly oxygenated water near the surface interacts little with mixed water lacking oxygen beneath it.

Water samples taken from the Niskin and Thoreson bottles can be also compared to the CTD data to account for any discrepancies in the data. Typically issues with the CTD, the laboratory equipment, or discrete sample collection can be identified after comparing the two sets of data. This graph represents the relationship between the dissolved oxygen concentrations measured by the CTD and the discrete dissolved oxygen concentrations obtained from bottle samples taken on the boat and fixed immediately after sample collection. The r² value provides the amount of variance between the two sampling methods at any given depth and location. The average of all discrete dissolved oxygen samples collects were compared to the CTD reading for each depth and location sampled. With an r² value of 0.9638, this trend line accounts for over 96% of the variance between the two collection methods. This high correlation between the two sampling methods suggest that not only was the CTD functioning properly, but discrete water samples taken in the field were fixed correctly and ultimately titrated properly (Winkler Method) in the lab to determine the dissolved oxygen concentrations within the Hood Canal.

        The secchi disk was used at each station to visually determine the relative turbidity of each station. Secchi readings ranged from 3m to 8.5m beneath the surface of the water. Although turbidity varied from station to station, the general trend shows light penetration highest within the northern stations of the Hood Canal and lower levels of light penetration near the southern end of the canal. Stations at the southern end of the canal are generally shallower, suggesting that particles suspended within the water are stirred up from the benthic zone by currents and tidal flows. Stations near the northern end of the Hood Canal are much deeper and particles suspended in the water may be from incoming saltwater as opposed to being the result of stirred up sediments from the benthic zone. The fact that readings were taken on two separate days must also be taken into account when considering differences in readings.

Sediment samples from station 2 (northern), 8 (central), and 23 (southern) were collected and analyzed to determine sedimentary composition in the Hood Canal.  All samples were taken near the shore at shallow depths.  The sediments were measured, and the most abundant size was 250 micrometers.  Comparing the most abundant size of the sediments to the Wentworth scale, it can be concluded that the sediment is between medium and fine sand along the length of Hood Canal. Total organic carbon was also measured within these samples, and is between 1.5 and 2.5 percent.  1.5 to 2.5 percent total carbon is fairly high.  This is expected in the Hood Canal since the flushing rate and mixing rate is low.

Phytoplankton samples collected using a 20um net were qualitatively analyzed to determine relative abundance of individual genera at each station (Phytoplankton Relative Abundances Table). Pseudo-nitzschia spp. was blooming at each station sampled on the Hood Canal. Phytoplankton of the genera Chaetoceros spp. and Protoperidinium spp. were also observed at each station sampled, however differed in abundance from station to station. Other organisms such as zooplankton and sea squirts were observed at several stations. Pollen was evident at two locations along the canal. The genera Actinopitychus spp., Dictyocha spp., Ditylum spp., Nocticluca spp., and Skeletonema spp. were also observed frequently.  All other genera of phytoplankton observed were found in relatively lower abundances, being classified as rare.