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o • o -o + 350 — 300 = 250 7 g 200 150 — 100 50 — • Patch O Non-patch % Water % Silt/clay % Organics Figure 6.14: Percentage water content, silt/clay fraction and organics (±S.E. Mean, n=6), for patch and non-patch azoic sediments. No statistical differences were found between the 2 plot types using Two-sample t-tests for any variable. Patch Non-patch 0 lcm 2cm 4cm Sediment depth Figure 6.15: Redox potential values in mV (±S.E. Mean, n=6) for patch and non-patch plots. *** Denotes a significant difference between patch and non-patch means where p
DISCUSSION The present study explicitly addressed three questions with respect to disturbances on intertidal sandflats. These were: (i) do tube-bed communities have different early successional dynamics from non tube-bed communities?; (ii) does the successional stage of a community affect the colonisation mode of early colonisers?; (iii) can sediment disturbance lead to P. elegans patch formation on Drum Sands? Do tube-bed communities have different early successional dynamics from non- tube-bed communities? These experiments compared the initial (3 week) communities colonising defaunated sediments within P. elegans patches with those in non-patch areas. The results indicated that some species colonised the two habitat types in significantly different numbers, at least at certain times of the year. P. elegans larvae colonised in significantly higher numbers in patch azoics than non-patch azoics during April 1997, but showed the opposite trend in August 1997 when larval recruitment was relatively low. Adult P. elegans colonised patch azoics in higher numbers than non-patch ones during August and December, although this was not significant due to high replicate variability. C. capitata consistently colonised in relatively high numbers in all three experiments while C. edule and M. balthica colonised non-patch azoic sediments in significantly higher numbers than patch azoics during April 1997. Multivariate analyses, together with non-parametric ANOS1M tests, revealed that the community composition of the azoic sediments was significantly different between the two habitat types during April 1997 only. These analyses also indicated that there was a strong temporal effect on initial community composition since the April community was markedly different from those of August and December 1997. Sediment measurements taken during December suggested that there were no significant differences between the levels of water, organics or silt/clay in azoic sediments between the two habitat types although the redox potentials at 2 and 4cm sediment depths were significantly lower in non-patch azoics. 164
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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
Page 128 and 129: The sediments could not be sampled
Page 130 and 131: RESULTS Species abundances - Table
Page 132 and 133: 90 — 80 — "-e-' 70 — 60 — 4
Page 134 and 135: 35 — *** 30 25 — 1.) = .-c‘l
Page 136 and 137: Pygospio elegans size distributions
Page 138 and 139: which is difficult to compare with
Page 140 and 141: eason why some invertebrates showed
Page 142 and 143: This study did not set out to expli
Page 144 and 145: This reliance upon the early establ
Page 146 and 147: CHAPTER 6 INITIAL COLONISATION OF D
Page 148 and 149: esulting community at any stage of
Page 150 and 151: ambient sediment had been removed.
Page 152 and 153: emoved since they were the only tax
Page 154 and 155: All statistics were performed using
Page 156 and 157: RESULTS Univariate analysis of spec
Page 158 and 159: 3.5 3 5 2 11 5 1 0.5 0 40 35 Ca 30
Page 160 and 161: 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 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 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
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8.2). This was mainly because of th
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120 100 80 60 - 40 20 0. cn1 c.n (i
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3NP 6NP 4NP 1 NP 5NP 2NP : 3P 1P 6P
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4P 3P 5P 5NP 6P 2P 1P Figure 8.8: T
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Figure 8.10 shows the dendrogram pr
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NP1 NP2 NP2 NP2 NP1 NP1 NP2 NP2 NP2
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Sediment water, organic and silt/cl
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5 350 — 300 250 200 — ISO — 1
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abundances of P. ciliata had more d
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levels of silt/clay and organics. S
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1973; Noji and Noji, 1991). Competi
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shown to consume up to 68% of a 0-g
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In Chapter 7 the micro-scale spatia
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and positions of patches. Consequen
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epresent those found establishing i
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distribution at the micro-scale. Ad
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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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