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P. elegans larvae at Drum Sands have a prolonged planktonic larval phase compared to those reported by Hannerz (1956). Larval measurements for the August, September and December samples were not taken due to the small number of females brooding larvae. However, observations suggested that the larvae present were also of the 3 to 5 setiger stage and resembled those previously described. 20 gr" 0 5 0 20 0 (i) March 1997 (iii) May 1997 20 115 If, 0 20 15 :;• 5 J 0 5 (ii) April 1997 (iv) Junc 1997 (vi) Fcbruary 1998 I I I Figures 3.5(i-vi) : Size-frequency histograms of P. elegans larvae from adult female tubes between March to July 1997 and February 1998 (n=50 for each month). No significant differences between size distributions for any month were observed (Kolmogorov-Smirnov test with Bonferroni correction) 73 d ,1 C;
DISCUSSION The aim of this study was specifically to investigate the population structure and reproductive biology of P. elegans on Drum Sands, Firth of Forth, and to elucidate the significance of these factors for population maintenance and the generation of the spatial patterns exhibited by P. elegans on this sandflat. Population structure and reproduction of Pygospio elegans at Drum Sands. This study has indicated that P. elegans on Drum Sands has adopted a planktonic mode of reproduction. No evidence of asexual reproduction and/or the production of benthic larvae was found between March 1997 and February 1998 for this population. At peak periods of larval development, approximately 50% of the adult female tubes contained embryos and/or larvae during the spring of 1997, although the following year, during February 1998, this reached 80% of the adult female population. Larvae were released at the 3-5 setiger stage into the water column. Settlement occurred during two main recruitment phases: the first, and numerically the most significant occurred during April/May 1997 while the second occurred during November/December 1997. Larvae settled at a size of approximately 0.13-0.17mm 5th setiger width, or 20 setigers, and grew rapidly (around 23 setigers/month) reaching sexual maturation size within 3 months after settlement. The adult population always consisted of a greater proportion of females than males, especially during the summer when the female:male ratio reached 6.19±0.48. Sampling was carried out from high density patches only and it is assumed that the same reproductive strategy and population structure occurred in lower density areas, although sampling in these areas would have been necessary to confirm this. Since P. elegans has been shown to exhibit very different reproductive strategies in different localities, it is not possible to predict the reproductive biology of a particular population. This point was addressed by Levin (1984b) who stated 'we should not assume that life history traits reported in the literature for a particular population will necessarily be accurate for different populations'. Consequently, assessing the timing and method of reproduction and the mode of larval development were prerequisites for the study of the processes affecting the spatial distribution of the P. elegans population at Drum Sands. 74
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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
Page 38 and 39: 57 64 1=1 0 0 0 0 0 0 0 O 0 0 0 0 0
Page 40 and 41: Maps produced by kriging and other
Page 42 and 43: 200 180 1160 140 100 1-3 80 g 60 c.
Page 44 and 45: 2.5 1.5 0.5 0 3 T (i) % Silt/clay%
Page 46 and 47: v : m pattern Id pattern Ip pattern
Page 48 and 49: " 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 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 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
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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
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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
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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
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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., .
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P . en .2 Co in ,.. ne .- cq . -- -
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