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5 350 — 300 250 200 — ISO — 100 — 50 — 0 350 — 300 — 250 — 200 — 150 — 100 — 50 — 0 350 — 150 100 — 350 E 300 .E 250 50 lcm 2cm 4cm 300 ---- 250 — 200 — 50 — (i) April 1997 Sediment depth (iii) December 1997 ............... 1 cm 2cm 4cm Sediment depth (iv) August 1998 Patch Non-patch lcm 2cm 4cm Sediment depth (ii) August 1997 Patch Non-patch Patch Non-patch 0 lcm 2cm 4cm Sediment depth Figures 8.13(i-iv) : Mean redox potential results (±S.E.Mean, n.6) for each sampling month showing the results of Two-sample t-tests between patch and non-patch values. ** Denotes a statistical difference between patch and non-patch means at 0.01 level of significance and *** at 0.001. 225
DISCUSSION This study monitored the faunal and sediment conditions of P. elegans patches and non-patch areas between April 1997 and August 1998. This discussion will firstly address the faunal differences observed between the two habitat types, and secondly, the differences observed in their sediment variables. Finally, since the results obtained at the end of this study revealed the demise of the P. elegans patches, this discussion will conclude with the faunal changes occurring within patches and the possible processes causing their decline on Drum Sands. Faunal differences between P. elegans patches and non-patch areas. The results indicated that many species showed significant differences in abundance between these two areas. C. capitata (April 1997), C. edule (April and August 1997, August 1998), M. balthica (December 1997 and August 1998) and C. volutator (April to December 1997) were all significantly more abundant in P. elegans patches compared with non-patch areas while no species were significantly more abundant in non-patch areas. The size distributions of certain species, i.e., P. elegans (April to December 1997) and C. capitata (December 1997), were also significantly different between the two habitat types. Multivariate analysis together with non-parametric ANOSIIVI tests revealed that the community compositions were always significantly different between the two habitat types and this was consistently due to several species such as C. edule, C. cap itata and C. volutator. The significant differences between the fauna of P. elegans patches compared with those of non-patch areas in this study support the results of previous studies. Fager (1964) noted that several species, the isopod Munna ubiquita, the pycnogonid Oropallene heterodentata, the hermit crab Pa gurus sp. and the anemone Zaolitus actius were only found in the stabilised sediments within the dense Owenia fusiformis tube-beds in his study. Similarly, Sanders et al. (1962) found that the small amphipod Listriella clymenella was only found within the tube arrays of the maldanid Clymenella torquata in the intertidal flats of Barnstable Harbor, Massachusetts. Woodin (1981) experimentally demonstrated that increases in the density of Diopatra cuprea tubes resulted in increases in macroinvertebrate species richness and abundances. Within the spionids, Noji (1994) noted that areas with moderate 226
- Page 192 and 193: study. These individuals would not
- Page 194 and 195: RESULTS Pilot survey - The pilot su
- Page 196 and 197: Transect survey - Micro-scale patte
- Page 198 and 199: Month v:m ratio pattern Id pattern
- Page 200 and 201: (i) March 1997, replicate 1 -iAlmiA
- Page 202 and 203: (xix) October 1997, replicate 1 (ra
- Page 204 and 205: The new recruits were only sufficie
- Page 206 and 207: The results of correlation analyses
- Page 208 and 209: cf.) . crt N ,—, Cr) C,1 ,—, Cr
- Page 210 and 211: 1.2 -0.4 "a 0.8 > (i) % Water conte
- Page 212 and 213: examine the micro-scale spatial pat
- Page 214 and 215: Invertebrate larvae, those of polyc
- Page 216 and 217: laboratory observations are needed
- Page 218 and 219: CHAPTER 8 THE FAUNAL COMMUNITIES OF
- Page 220 and 221: Other theories have been postulated
- Page 222 and 223: RESULTS Univariate analysis of spec
- Page 224 and 225: -T. g 80 g 50 40 30 20 10 (i) Adult
- Page 226 and 227: in significant differences in size
- Page 228 and 229: 8.2). This was mainly because of th
- Page 230 and 231: 120 100 80 60 - 40 20 0. cn1 c.n (i
- Page 232 and 233: 3NP 6NP 4NP 1 NP 5NP 2NP : 3P 1P 6P
- Page 234 and 235: 4P 3P 5P 5NP 6P 2P 1P Figure 8.8: T
- Page 236 and 237: Figure 8.10 shows the dendrogram pr
- Page 238 and 239: NP1 NP2 NP2 NP2 NP1 NP1 NP2 NP2 NP2
- Page 240 and 241: Sediment water, organic and silt/cl
- Page 244 and 245: abundances of P. ciliata had more d
- Page 246 and 247: levels of silt/clay and organics. S
- Page 248 and 249: 1973; Noji and Noji, 1991). Competi
- Page 250 and 251: shown to consume up to 68% of a 0-g
- Page 252 and 253: In Chapter 7 the micro-scale spatia
- Page 254 and 255: and positions of patches. Consequen
- Page 256 and 257: epresent those found establishing i
- Page 258 and 259: distribution at the micro-scale. Ad
- Page 260 and 261: provide a rich food source for deme
- Page 262 and 263: Armonies W., 1988. Active emergence
- Page 264 and 265: Cha M.W., in prep. Macroalgal mats
- Page 266 and 267: Dobbs F.C. and Vozarik J.M., 1983.
- Page 268 and 269: Flach E.C., 1996. The influence of
- Page 270 and 271: Hall SI, Raffaeni D.G., Basford DJ.
- Page 272 and 273: Keckler D., 1997. Surfer for Window
- Page 274 and 275: Levin L.A. and Creed E.L., 1986. Ef
- Page 276 and 277: Mileikovsky S.A., 1971. Types of la
- Page 278 and 279: Ong B. and Krishnan S., 1995. Chang
- Page 280 and 281: Raffaelli D.G., Hildrew A.G. and Gi
- Page 282 and 283: Scheltema R.S., 1974. Biological in
- Page 284 and 285: Soulsby P.G., Lowthion D., Houston
- Page 286 and 287: McArdle B.H., Morrisey D., Schneide
- Page 288 and 289: Wharfe J.R., 1977. An ecological su
- Page 290 and 291: Zajac R.N. and Whitlatch R.B., 1982
5<br />
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(i) April 1997<br />
Sediment depth<br />
(iii) December 1997<br />
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1 cm 2cm 4cm<br />
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(iv) August 1998<br />
Patch<br />
Non-patch<br />
lcm 2cm 4cm<br />
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Patch<br />
Non-patch<br />
Patch<br />
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Sediment depth<br />
Figures 8.13(i-iv) : Mean redox potential results (±S.E.Mean, n.6) for each sampling<br />
month showing the results of Two-sample t-tests between patch and non-patch values.<br />
** Denotes a statistical difference between patch and non-patch means at 0.01 level of<br />
significance and *** at 0.001.<br />
225
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