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Other theories have been postulated for the observed community differences within tube-beds. Woodin (1978, 1981) suggested that the observed effects result from the 'refuge' provided by the high numbers of tubes. Both predation and local disturbances have been shown to be important structuring forces for soft-bottom infauna (Reise, 1978; Woodin, 1978; Zajac and Whitlatch, 1982a; Ambrose, 1984; Thrush, 1988; Hall et al., 1993) and Woodin (1978) suggested that refuges may be created by organisms whose structures buffer the impact of physiological stress or inhibit the access of predators. Woodin (1976) viewed soft-bottom community structuring from the perspective of 'functional group' interactions in which 'tube- dweller', `bioturbator' and `suspension-feeder' functional groups should each be unfavourable to each other. This 'functional group' interaction hypothesis implied that the maintenance of discrete dense assemblages in infaunal systems was due to interactions between established infaunal individuals and settling larvae. Therefore, a tube-building species would be expected to exhibit increased densities within an assemblage of other tube-builders by this interaction, whilst bioturbators and suspension-feeders would be expected to exhibit lower densities. The main tube-building polychaete species forming dense tube-beds in northern European shallow waters tend to be either Lanice conchilega or Pygospio elegans. Several studies such as Eagle (1973, 1975), Carey (1982) and Ragnarsson (1996) have described the fauna within L. conchilega tube-beds, however, relatively few studies have focused on the beds formed by P. elegans (e.g., Dupont, 1975; Morgan, 1997). The dense tube-beds at Drum Sands allowed an investigation of the effects of this tube-builder on an intertidal sandflat. Specifically, the differences in the biology and the sediments within P. elegans patches and non-patch areas of sand were studied. 203
METHODS The sampling for the investigation described in Chapter 6 was carried out at the same time and within the same patch and non-patch plots as those for the present study. However, a further survey was also carried out in August 1998 for this study. Faunal sampling methods, sample treatment and sorting, faunal identification and statistical analyses for this chapter are as described in Chapter 6. While sediment variables were only measured on one occasion for the investigation described in Chapter 6, the same variables were measured at each sample date for the present study, i.e., April, August and December 1997, and August 1998. In addition to the size measurements of P. elegans, individuals of other species with mean abundances above 20 per core in patch and non-patch samples were measured. P. elegans and C. capitata were measured as 5th setiger and 3rd setiger widths respectively. Small bivalves were measured as shell width using a microscope (x20 magnification) fitted with an eyepiece graticule while larger ones were measured with a pair of calipers. 204
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AN INVESTIGATION INTO THE PROCESSES
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ABSTRACT The spionid polychaete Pyg
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ACKNOWLEDGEMENTS I am indebted to m
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Results. . 65 Size distribution of
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CHAPTER 9. GENERAL DISCUSSION . . 2
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Figure 5.4 Figure 5.5 Figure 6.1 Fi
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LIST OF TABLES Table 2.1 Statistica
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BACKGROUND CHAPTER 1 INTRODUCTION A
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The scales of observation, or the s
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systematic sampling design to inves
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aised sediment within an otherwise
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Fauchald and Jumars (1979) describe
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Dalmeny House and sewage discharged
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E 7— E 6-ac. MHWS MHWN t co 4 —
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variance (TTLQV) techniques (see Lu
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analysis using Moran's and Geary's
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Holme and McIntyre (1984). Percenta
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Pattern Analysis - Grid Surveys Sur
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57 64 1=1 0 0 0 0 0 0 0 O 0 0 0 0 0
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Maps produced by kriging and other
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200 180 1160 140 100 1-3 80 g 60 c.
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2.5 1.5 0.5 0 3 T (i) % Silt/clay%
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v : m pattern Id pattern Ip pattern
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" v : m pattern Id pattern Ip patte
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The results show that at the smalle
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Nephtys hombergii's spatial distrib
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(vii) G. duebeni (ix) % Organic con
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8m survey - spatial patterns Figure
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(1) P. elegans (iii) L. conchilega
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a) Ts 1.4 0.6 u 0.2 -0.2 1.4 'E5 0.
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200m 150m 100m 50m (ix) C. edule 56
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73 ‘a• el 1.4 (ix) G. duebeni 1
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DISCUSSION The main aims of this st
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formed patches less than 1m2 and th
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stutchbutyi, at Wirroa island, New
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exhibited by the tube-building poly
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CHAPTER 3 THE POPULATION STRUCTURE
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Asexual reproduction by fragmentati
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METHODS Survey design - It has been
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RESULTS The species abundances in e
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corresponds to 44 setigers using Eq
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1 0000000 00 rg 0 00 d- - Xauanbau
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Reproductive activity of Pygospio e
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P. elegans larvae at Drum Sands hav
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Pygospio elegans showed great seaso
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Previous studies have produced simi
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The sole reliance on a planktonic m
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abundance are highly seasonal, were
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CHAPTER 4 THE EFFECTS OF MACROALGAL
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studies may have been completely di
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METHODS Study site - The exact posi
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1 C N W 4----111" 1.5m 2 NW C Contr
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sediment sampling, together with re
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RESULTS Species abundances - The me
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; 15 35 — 30 — 25 — 10 — 5
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statistical difference from net plo
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Pygospio elegans size distribution
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used, approximately equivalent to t
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artefacts associated with the metho
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present in high numbers around sewa
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lack, hydrogen sulphide-smelling se
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CHAPTER 5 THE EFFECTS OF MACROALGAL
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METHODS Survey design - During late
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The sediments could not be sampled
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RESULTS Species abundances - Table
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90 — 80 — "-e-' 70 — 60 — 4
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35 — *** 30 25 — 1.) = .-c‘l
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Pygospio elegans size distributions
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which is difficult to compare with
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eason why some invertebrates showed
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This study did not set out to expli
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This reliance upon the early establ
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CHAPTER 6 INITIAL COLONISATION OF D
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esulting community at any stage of
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ambient sediment had been removed.
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emoved since they were the only tax
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All statistics were performed using
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RESULTS Univariate analysis of spec
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3.5 3 5 2 11 5 1 0.5 0 40 35 Ca 30
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of non-patch areas (Figure 6.3(vi))
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the individuals colonising patch az
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Multivariate analysis of community
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Month Sample statistic (Global R) N
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2NP 3NP 4NP .•,, 6NP 5NP 6P 1NP i
Page 170 and 171: Figure 6.8: Two-dimensional MDS ord
Page 172 and 173: - - 5P ... 4P . 6P • .‘2NP 1NP
Page 174 and 175: I 50. 1 60. 70. 80. 90. 100. BRAY-C
Page 176 and 177: 'P2-AZ P3-AZ N2-AZ .- - - " .„ ..
Page 178 and 179: o • o -o + 350 — 300 = 250 7 g
Page 180 and 181: The importance of the ambient commu
Page 182 and 183: In April, when P. elegans larval av
Page 184 and 185: not only for errant polychaetes, bu
Page 186 and 187: observed in this study. How crucial
Page 188 and 189: Micro-scale spatial patterns of mac
Page 190 and 191: METHODS Experimental design - A pre
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 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 242 and 243: 5 350 — 300 250 200 — ISO — 1
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
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Hall SI, Raffaeni D.G., Basford DJ.
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Keckler D., 1997. Surfer for Window
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Levin L.A. and Creed E.L., 1986. Ef
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Mileikovsky S.A., 1971. Types of la
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Ong B. and Krishnan S., 1995. Chang
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Raffaelli D.G., Hildrew A.G. and Gi
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Scheltema R.S., 1974. Biological in
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Soulsby P.G., Lowthion D., Houston
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McArdle B.H., Morrisey D., Schneide
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Wharfe J.R., 1977. An ecological su
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Zajac R.N. and Whitlatch R.B., 1982
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- C'e) oc0000mooF,o•-ooNtn-coo-00
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APPENDIX 1.2: SPECIES ABUNDANCES FR
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ON In co In ° ken n00000N---0g0N-.
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o m000eno,-0-. 0 0000en ,-. 0.-00 o
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APPENDIX 2: SPECIES ABUNDANCES FROM
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0.- CV N - , .- CI E.104 ..r cv g.,
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cv en 0 a .- ,- .- .- g c', ,- ,- g
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PI — — — Pi n — — - R., .
Page 308 and 309:
P . en .2 Co in ,.. ne .- cq . -- -
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