Download (20MB) - Repository@Napier
Download (20MB) - Repository@Napier Download (20MB) - Repository@Napier
All statistics were performed using Minitab version 10.0, except for the Kolmogorov- Smirnov test which was carried out by hand using the formula given by Zar (1984) and the tables given by Smirnov (1948). Multivariate analyses were carried out on the faunal data to assess (dis)similarities between community assemblages. All multivariate analyses were performed using the PRIMER (Plymouth Routines In Multivariate Ecological Research) package, version 4.0 (see Warwick and Clarke, 1994). Dendrograms were produced by hierarchical agglomerative clustering with group-average linking from the Bray-Curtis similarity matrices. The raw community data were square-root transformed, this was chosen a priori as a compromise between no transformation in which different community assemblages may result from the variability in the most common taxa, and a strong transformation, such as -JAI or log(x+1), in which the rarer species have very strong influences on community (dis)similarities (Warwick and Clarke, 1994). Non-metric Multi-Dimensional Scaling (or MDS) was carried out from which an ordination plot was produced. In ordination plots, the relative distances apart of the samples reflect relative similarity in species composition. Since the MDS ordination represents a multi-dimensional ordination in 2 dimensions, each algorithm has an associated stress value, the influence of which on the reliability of ordination plots is discussed by Warwick and Clarke (1994). The final MDS ordination in each analysis was that with the lowest associated stress value out of 9 iterations. The MDS procedure was repeated 10 times for each analysis to minimise the chance of producing MDS plots with only 'local minimum' stress functions (Warwick and Clarke, 1994), i.e., increasing the number of starting configurations of points in the ordination plots increases the chance of producing the most optimum MDS plot. Testing for significance between patch and non-patch communities was performed using a One-way ANOSIM test (analysis of similarities) in which the null hypothesis (Ho) in each case was that there were no significant community differences between the two plot types. The ANOSIIVI test can be regarded as a non-parametric equivalent of the MANOVA test (e.g., Mardia et al., 1979) in which few, if any, assumptions about the data are made. Benthic community data are usually far from normally 139
distributed (Clarke, 1993) and, therefore, a non-parametric test is usually more suitable. However, no corrections are made for multiple pairwise testing (Warwick and Clarke, 1994), consequently, more emphasis should be placed on the value of R, the test statistic, rather than the p value. The test statistic R will always be between 0 and 1; if R-,-. 1 all replicates within sites are more similar to each other than any other replicates from different sites while if R---0 similarities between and within sites will be the same on average. As with standard univariate tests, it is possible for R to be significantly different from zero yet relatively small if there are many replicates for each site. The ANOSIM test is more reliable for indicating treatment differences than the MDS plot since it works on the full similarity matrix rather than the approximation to it in 2-dimensions (Warwick and Clarke, 1994). 140
- 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.
- Page 152 and 153: emoved since they were the only tax
- 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 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
distributed (Clarke, 1993) and, therefore, a non-parametric test is usually more<br />
suitable. However, no corrections are made for multiple pairwise testing (Warwick<br />
and Clarke, 1994), consequently, more emphasis should be placed on the value of R,<br />
the test statistic, rather than the p value. The test statistic R will always be between 0<br />
and 1; if R-,-. 1 all replicates within sites are more similar to each other than any other<br />
replicates from different sites while if R---0 similarities between and within sites will<br />
be the same on average. As with standard univariate tests, it is possible for R to be<br />
significantly different from zero yet relatively small if there are many replicates for<br />
each site. The ANOSIM test is more reliable for indicating treatment differences than<br />
the MDS plot since it works on the full similarity matrix rather than the approximation<br />
to it in 2-dimensions (Warwick and Clarke, 1994).<br />
140
Change language