Rocky shores

A By plotting the occurrence of organisms on transects, and making reference to tide tables, investigate the relationships of the littoral fringe, eulittoral zone and sublittoral fringe (see Hawkins and Jones, 1992) to the tidal levels of the shore. Compare the extent and levels of these zones on different shores, for example algal-dominated and barnacle-dominated shores. B Using the notation given below (see page 444), plot the zonation of organisms on shores of various aspects, and attempt to relate to Exposure Scales (Ballantine, 1961; Lewis, 1964). C Investigate the vital statistics of populations of selected shore molluscs, for example Gibbula cineraria, Monodonta lineata, Littorina littorea, Nucella lapillus, Patella spp. by plotting size/frequency curves from convenient shell measurements, for example height or maximum diameter. Compare the populations of different levels and different shores. D In appropriate quadrats on various shores and/or levels, investigate the correlations between the following pairs of measurements (a)/(b), and discuss your findings.

(a) Percentage cover or wet weight of macroflora.

(b) Numbers or wet weights of Patella vulgata, Littorina obtusata and L. littorea.

(a) Percentage cover, rough weights or numbers of barnacles.

(b) Rough weights or numbers of Nucella lapillus.

(a) Ratio of shell height/length in Patella occupying surfaces of similar slope and aspect.

(a) Mean size of Patella shells.

(b) Numbers of Patella per unit area.

E Marking experiments. For studying movements and homing tendencies, mark mollusc shells, for example Patella, Nucella, littorinids and trochids, with waterproof paint. Alternatively, plastic numbers (e.g. 'Dynotape') can be stuck on the shell with epoxy-resin after first drying the shell with alcohol. In the course of these observations, a visit to the shore during a night-time low tide should be made to compare the positions of specimens during day and night.

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