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studies may have been completely different environments and, therefore, not comparable. Controlled, experimental manipulations are much more objective and less equivocal ways of investigating the effects of weed mats on the sediments and their fauna. Unfortunately, of the few experiments previously carried out, Everett (1991) suggested that the interpretation of the results is often difficult due to the lack of experimental controls (Olafsson, 1988) or lack of replication (Reise, 1983a). Such experiments have been carried out either by implanting weed into the sediments of areas where weed mats are not present (e.g., Thrush 1986a; Hull, 1987) or by removing algae from the sediments within algal-affected areas (e.g., Reise, 1985; Everett, 1991). These two approaches have been shown to produce similar results (Raffaelli et al., 1999). The algal-removal method, however, makes two assumptions. Firstly, it assumes that the physical removal of weed has no effect on the sediment and its fauna, and secondly, that the effect of the weed upon hydrodynamics is very localised, i.e., algal-free plots are not affected by the surrounding weed. The latter may be an unreasonable assumption for weed species which form long strands such as Enteromorpha spp.. However, an experimental approach overcomes the inherent problem of surveys (i.e., the large-scale separation of weed-affected and weed-free areas) and allows variables known to affect the sediment and its invertebate fauna, e.g., weed species, biomass, weed-mat size and the timing of weed establishment, to be controlled. Furthermore, treatments can be fully interspersed (Krebs, 1989). During the summer of 1996, part of the present study area within Drum Sands (Figure 4.1) was covered with weed mats. The weed (mainly Vaucheria subsimplex, with some Enteromorpha prolifera) occurred in patches, covering approximately 30-40% of the total sediments and 100% within patches. Unfortunately, Drum Sands is not regularly monitored and therefore it is not known whether this was an annual occurrence. In order to investigate the faunal effects of these weed mats within this area of Drum Sands, a controlled weed-implantation experiment was conducted during the summer of 1997. It has been shown (see Chapter 3) that the life-history and the reproductive 85
mode of development exhibited by P. elegans on Drum Sands made this species particularly suited to increase in numbers following a large-scale disturbance, particularly during early summer and mid-winter. Algal-mat formation is potentially an important large-scale disturbance at Drum Sands and, therefore, it was interesting to test the hypothesis that weed mats play an important role in structuring species distributions on Drum Sands, P. elegans in particular. The patchy nature of weed mat formation suggested that it could have been a potentially important structuring force in the production of the mosaic of communities revealed in Chapter 2. Therefore, this study specifically aimed at investigating the ecological effects of macroalgal mats on intertidal sandflats and whether such mats potentially played a role in P. elegans patch formation on Drum Sands. 86
Page 1 and 2:
AN INVESTIGATION INTO THE PROCESSES
Page 3 and 4:
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
Page 50 and 51: The results show that at the smalle
Page 52 and 53: Nephtys hombergii's spatial distrib
Page 54 and 55: (vii) G. duebeni (ix) % Organic con
Page 56 and 57: 8m survey - spatial patterns Figure
Page 58 and 59: (1) P. elegans (iii) L. conchilega
Page 60 and 61: a) Ts 1.4 0.6 u 0.2 -0.2 1.4 'E5 0.
Page 62 and 63: 200m 150m 100m 50m (ix) C. edule 56
Page 64 and 65: 73 ‘a• el 1.4 (ix) G. duebeni 1
Page 66 and 67: DISCUSSION The main aims of this st
Page 68 and 69: formed patches less than 1m2 and th
Page 70 and 71: 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 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 122 and 123: lack, hydrogen sulphide-smelling se
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.
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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
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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
Page 222 and 223:
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
Page 242 and 243:
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
Page 252 and 253:
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
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
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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
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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-.
Page 298 and 299:
o m000eno,-0-. 0 0000en ,-. 0.-00 o
Page 300 and 301:
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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