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lack, hydrogen sulphide-smelling sediments, suggesting that oxygen exchange between the sediments and the overlying water column was severely reduced. Raffaelli et al. (1999) suggested that the differences observed between the studies by Everett (1994) and Hull (1987) was due to M. balthica in Hull's study being settling spat while they were adults in Everett's study. The low ambient abundances of the two bivalve species in the present study were probably partly responsible for the lack of a significant weed effect, although increased food and more reducing sediments could have been two opposing factors. Macroalgal mats and P. elegans patch formation. The results of this experiment support the conclusion of Thrush (1986a) who proposed that patchily distributed accumulations of macroalgae result in spatial variations in the faunal structure of the benthos. However, the results showed that the E. prolifera implanted during this experiment on Drum Sands did not, at least in the short term, result in increased numbers of P. elegans and, therefore, did not support the suggestion that macroalgal mat formation has a role in P. elegans patch establishment. Instead, the faunal communities under weed mats shortly after implantation, to just after weed disappearance 20 weeks later, were dominated by C. capitata, with increased numbers of oligochaetes and gammarids. Unfortunately, monitoring P. elegans densities in weed treatment plots in the longer term was rendered impossible due to mussel colonisation onto the plastic netting in the weed treatment and net plots. Therefore, although E. prolifera had a negative effect on P. elegans, both on the post- larval population and on larval recruitment, the potentiality of P. elegans later increasing in numbers remains unresolved. An increase in P. elegans population density would only have been possible during late November/early December when larval recruitment occurred (Chapter 3), a time when weed-affected areas would have been numerically dominated by C. capitata. Controlled, manipulation experiments potentially allow a less equivocal way of determining the effects of weed mats on intertidal sandflats. However, since the biotic and abiotic responses are dependent upon factors such as weed type, biomass and timing of establishment, experiments are unlikely to unequivocally link macroalgal mat establishment with invertebrate patch formation in a particular environment 107
unless all these factors in the experiment closely mimic those of naturally occurring weed mats. Logistically, it is very difficult to closely mimic all these factors in an experiment. For this reason, a descriptive survey of the effects of natural weed mats on Drum Sands was considered necessary and is discussed in Chapter 5. 108
Page 1 and 2:
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
Page 72 and 73: exhibited by the tube-building poly
Page 74 and 75: CHAPTER 3 THE POPULATION STRUCTURE
Page 76 and 77: Asexual reproduction by fragmentati
Page 78 and 79: METHODS Survey design - It has been
Page 80 and 81: RESULTS The species abundances in e
Page 82 and 83: corresponds to 44 setigers using Eq
Page 84 and 85: 1 0000000 00 rg 0 00 d- - Xauanbau
Page 86 and 87: Reproductive activity of Pygospio e
Page 88 and 89: P. elegans larvae at Drum Sands hav
Page 90 and 91: Pygospio elegans showed great seaso
Page 92 and 93: Previous studies have produced simi
Page 94 and 95: The sole reliance on a planktonic m
Page 96 and 97: abundance are highly seasonal, were
Page 98 and 99: CHAPTER 4 THE EFFECTS OF MACROALGAL
Page 100 and 101: studies may have been completely di
Page 102 and 103: METHODS Study site - The exact posi
Page 104 and 105: 1 C N W 4----111" 1.5m 2 NW C Contr
Page 106 and 107: sediment sampling, together with re
Page 108 and 109: RESULTS Species abundances - The me
Page 110 and 111: ; 15 35 — 30 — 25 — 10 — 5
Page 112 and 113: statistical difference from net plo
Page 114 and 115: Pygospio elegans size distribution
Page 116 and 117: used, approximately equivalent to t
Page 118 and 119: artefacts associated with the metho
Page 120 and 121: present in high numbers around sewa
Page 124 and 125: CHAPTER 5 THE EFFECTS OF MACROALGAL
Page 126 and 127: 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
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- - 5P ... 4P . 6P • .‘2NP 1NP
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I 50. 1 60. 70. 80. 90. 100. BRAY-C
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'P2-AZ P3-AZ N2-AZ .- - - " .„ ..
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o • o -o + 350 — 300 = 250 7 g
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The importance of the ambient commu
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In April, when P. elegans larval av
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not only for errant polychaetes, bu
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observed in this study. How crucial
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Micro-scale spatial patterns of mac
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METHODS Experimental design - A pre
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study. These individuals would not
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RESULTS Pilot survey - The pilot su
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Transect survey - Micro-scale patte
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Month v:m ratio pattern Id pattern
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(i) March 1997, replicate 1 -iAlmiA
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(xix) October 1997, replicate 1 (ra
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The new recruits were only sufficie
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The results of correlation analyses
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cf.) . crt N ,—, Cr) C,1 ,—, Cr
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1.2 -0.4 "a 0.8 > (i) % Water conte
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examine the micro-scale spatial pat
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Invertebrate larvae, those of polyc
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laboratory observations are needed
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CHAPTER 8 THE FAUNAL COMMUNITIES OF
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Other theories have been postulated
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RESULTS Univariate analysis of spec
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-T. g 80 g 50 40 30 20 10 (i) Adult
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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
Page 262 and 263:
Armonies W., 1988. Active emergence
Page 264 and 265:
Cha M.W., in prep. Macroalgal mats
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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
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Levin L.A. and Creed E.L., 1986. Ef
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Mileikovsky S.A., 1971. Types of la
Page 278 and 279:
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
Page 284 and 285:
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
Page 302 and 303:
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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