METHODS AND MATERIALS

Sampling took place during a research cruise to the SBIC by the CCGS Vector in April 2002. Eight sediment-water interface samples were collected using a Smith-Mac grab sampler in Belize Inlet (BE1, BE2, BE3, BE5, BE7) and Alison Sound (ALS1, ALS2 and ALS3; Figure 1). In addition, one 145 cm freeze core, FC04, was collected in Belize Inlet at a water depth of 274 m (Figure 1). Subsequent to collection, the grab samples were treated with alcohol as a preservative, stored in plastic vials, and shipped by air to Carleton University, where they were stored prior to processing in a cool room at +4°C.

The freeze core was stored in a freezer aboard the CCGS Vector until the vessel returned to port, at which point the core was transported to the Pacific Geoscience Centre (PGC) in Sidney, BC. At the PGC, the outer layer of the freeze core was removed in situ to reduce the risk of contamination. The core was then subdivided longitudinally into ~1 x 2 cm subsections using a band saw, and then subdivided laterally to facilitate handling and x-raying. One complete set of freeze core subsections was transported frozen to Carleton University for subsequent analysis, where they were kept at a constant temperature of –9°C.

Examination of the grab samples in 2004 revealed no discernable deterioration. Samples from Alison Sound, where dysoxic conditions prevailed, were characterized by a slight sulfurous smell, as well as darker color than those from the more oxygenated Belize Inlet. Ten cm3 aliquots were taken from each grab sample and wet sieved through a 63 mm screen to retain foraminifera and a 500 mm screen to remove coarse organic material. The samples were subsequently split into two fractions using a 125 µm screen, dried under low heat (50°C) in an oven, and weighed. Splitting dry samples into fractions prior to quantitative analysis was done in order to avoid counting errors, as the focus of the microscope does not have to be continually changed (Schröder et al. 1987).

Freeze core FC04 was also taken out of the freezer in 2004 and inspected. As no visible deterioration was detected on the surface, such as desiccation cracks or evidence of mold, it was deemed suitable for analysis. The sediments comprising the freeze core FC04 were very fine grained and soupy, and would have been impossible to recover using conventional coring methods. The core was subdivided using a ceramic knife into 121, 1 cm thick samples for foraminiferal analysis. Ceramic knives are particularly useful for subdividing freeze cores, as the blade is extremely thin and sharp and permits the production of extremely thin slices when required. A few subsamples were selected for dating of the core with ¹⁴C and ²¹⁰Pb, which revealed that it was comprised of sediments deposited between ~ 900 AD and 2002 AD. The rest of the freeze core samples were sieved and processed using the same procedure described above for the grab samples.

Since almost two years had passed between the collection of the samples and the laboratory analysis, it was concluded that the staining of the microfossils with Rose Bengal, used to distinguish between live and dead populations, would not provide reliable results. It was assumed that all the cytoplasmic material would already be dead by the time of analysis.

These sediment-water interface grab and freeze core samples were quantitatively analyzed for foraminifera under an Olympus SZH10 stereo microscope. All foraminiferal specimens were picked and stored on gridded micropaleontological slides, and identified following the classification of Loeblich and Tappan (1987). Scanning electron photomicrographs were obtained using a JEOL 6400 Scanning Electron Microscope at the Carleton University Research Facility for Electron Microscopy (CURFEM), and the digital images were later converted into figures.