Sabellaria alveolata bioconstructions display a great deal of temporal variability within a fairly constant geographic range (e.g. Cunningham et al. 1984, Frost et al. 2004). Even on a shore where S. alveolata is continually present, there is a great deal of variability in terms of abundance and ‘within shore’ distribution. Little is known about the processes (biotic or abiotic) shaping the distribution and abundance of S. alveolata at local scales.
A subset of twelve locations have been selected to establish a network for sustained observations. A hierarchical sampling program will describe the changes in distribution and abundance of S. alveolata at a range of spatial scales (small: cm-m, medium: m-km and large scale: 10-100km) in relation to both biotic (macroalgae cover, competition with other space-occupying species such as oysters, mussels or barnacles) and abiotic factors (air and sea temperature, exposure to wave action, sand inputs and sedimentation processes etc.). Efforts will be made to disentangle the relative contribution of the various processes in determining patterns of distribution throughout the geographic range.
At each station, a similar protocol will be applied for each season, in winter (at the coldest period) and in late summer (at the hottest period), , to address temporal variability. The winter period will provide a status of the bioconstructions after the autumn storms and during the period with the lowest food concentration. Conversely, the summer period will integrate the spring recruitment and will be carried out during the calmest time of the year.
At each location the distribution and abundance of S. alveolata will be quantitatively surveyed in five replicate 5 x 5 m permanent patches established at the mid tidal level. The % cover of S. alveolata, bare rock, sand and other space occupying organisms (e.g. mussels, oysters, algae) within the patch will be surveyed to a high level of precision by subdividing the area into a hundred 1m2 plots which will be surveyed using 1 x 1 m quadrats (100 times 1 m2 - see Figure 1b). Within each quadrat the % cover of S. alveolata, bare rock, sand and other space-occupying organisms will be estimated. Each location will be surveyed 2 times per year during 2 years.
In each of the twelve locations a much larger grid (500 x 500 m) will also be used. This grid will allow a large-scale overview of each survey location. 100 substrate points will be spread throughout the grid and will be regularly surveyed.