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examine the micro-scale spatial patterns of spionids in soft sediments. Different inter- individual patterns have been observed which have been related to, and supposedly generated by, intraspecific interactions. For example, Levin (1981) found individuals of Pseudopolydora cf. paucibranchiata to be uniformly distributed on the intertidal mudflats of Mission Bay, San Diego. She suggested, following observations on its feeding behaviour, that this distribution in this large, aggressive spionid resulted from defensive behaviour and guarding of food, space and tube-building materials. She also found that Streblospio benedicti, a smaller spionid polychaete, was randomly distributed suggesting a greater tolerance to intraspecific encounters. However, at their highest densities, 16,500/m2, Levin (1981) found that S. benedicti was also uniformly distributed indicating some density-dependent competition. Morgan (1997) found, by superimposing a 10x10 grid of 2mm 2 squares onto the surface of a larger core, that P. elegans was randomly distributed at high densities (47,500/m2- 82,500/m2). That P. elegans did not exhibit a uniform distribution at these densities suggested that this species was very high-density tolerant, in contrast to P. cf. branchiata and S. benedicti, the latter being similar in size and having a similar feeding behaviour to P. elegans. This is supported by the observations of Brey (1991) who reported no signs of aggressive behaviour between P. elegans individuals. It is difficult to relate the present findings with those of the above studies because of sampling-scale differences. Since P. elegans abundances were too low to sample at the scale of an individual's influence (i.e., 2mm 2) in this study, the results cannot unequivocally be compared with the results of Morgan (1997) or the plotless sampling methods of Levin (1981). For example, plotless sampling, within the micro-scale P. elegans patches observed in this study, might have revealed a localised uniform distribution (and hence possibly negative intraspecific interactions) and similarly, sampling with 3cm 2 cores in the studies by Levin (1981) and Morgan (1997) might have revealed clumped distributions in much the same way as in the present study. The relatively low overall P. elegans densities within small-scale patches on Drum Sands indicated that in order to investigate the inter-individual spatial distribution and hence provide evidence for intraspecific interactions, plotless sampling would have been necessary. However, what this study has revealed is the presence of micro-scale 196
patchiness within which P. elegans abundances were high enough to allow the possibility of inter-individual interactions. The presence of these patches support the view that P. elegans is relatively tolerant of intraspecific interactions. The processes possibly giving rise to such patches are discussed below. The roles of larval recruitment, interspecific interactions and abiotic variables in determining micro-scale spatial patterns of P. elegans. The results from this study indicated that the micro-scale patches of adult P. elegans, within the 1-1.5m 2 patches of increased density defined in Chapter 2, were neither positively nor negatively correlated with any other species of sufficient abundance for analysis during the study period (except for a positive correlation with C. edule in one replicate during July 1997). The abundances of P. elegans new recruits (
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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))
Page 162 and 163: the individuals colonising patch az
Page 164 and 165: Multivariate analysis of community
Page 166 and 167: Month Sample statistic (Global R) N
Page 168 and 169: 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 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 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
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Armonies W., 1988. Active emergence
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Cha M.W., in prep. Macroalgal mats
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Dobbs F.C. and Vozarik J.M., 1983.
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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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