Download (20MB) - Repository@Napier

METHODS
Scales of Spatial Variability - Transect Survey
Survey design - The `transece survey for investigating the scales of spatial variability
was carried out between the 17 and 18th of March, 1996. This survey used 16 plots
arranged as shown in Figure 2.1. This design enabled the investigation of different
scales of variation (patchiness) within the site using replicates within plots. The
design can be described as 4 transects, 133m apart, with 4 plots along each, separated
by 20m, 80m and 150m. Therefore, maximum scales of variability, in one direction
only, within the area of relatively homogeneous sediments outlined in Figure 1.2 were
investigated with this design.
Within each plot (1x1m), 3 randomly positioned box-core samples (25x25cm, 15cm
depth) were taken and the sediments sieved through a 0.5mm mesh sieve. The
samples were then fixed and preserved with saline formaldehyde solution (10%),
neutralised with 0.2% sodium tetraborate (Borax) with a Rose Bengal (0.01%) stain
and stored. The samples were later washed with water to remove the formaldehyde
and the fauna sorted in a sorting tray with the aid of a magnifying lens and stored in
70% ethyl alcohol before identification. The fauna were identified to the lowest
possible taxonomic level and counted. Capitella spp., which is known to be
comprised of a morphologically similar but genetically distinct, sibling species were
recorded as Capitella capitata (Grassle, 1984) for all of the studies carried out on
Drum Sands. Pleijel and Dales (1991) suggested that Eteone flava and Eteone longa
could represent two sibling species and that it is difficult to distinguish between them
with preserved samples. Consequently, these individuals are called Eteone cfflava for
this study.
Sediment samples were taken for organic carbon analysis and particle size analysis
using a corer (2.4cm internal diameter) to a depth of 3cm and frozen at -20°C for
storage. These samples were taken to 3cm depth since preliminary studies found the
majority of the fauna inhabited sediments above this depth. Three randomly placed
sediment samples were taken within each plot and pooled. Organic carbon content
determination was done by weight loss on ignition at 480°C for 4 hours. Particle size
distribution analysis was performed using the 'clean beach sand' method described in
19