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. Hibino, R. van Woesik J. Exp. Mar. Biol. Ecol. 252 2000 1 –14
test, respectively. These tests were undertaken on four primary variables: 1 net weight change of carbonate tiles; 2 E
. mathaei densities; 3 calcareous encrustation cover; and 4 substrate type. With the exception of net weight change, the results of the a
priori tests revealed that transformations were necessary. A one-way analysis of variance ANOVA was undertaken on net weight change first testing for significant seasonal
differences note that a four-way ANOVA was not possible, testing season, location, windward leeward and depth, because the summer typhoon dislodged numerous tiles.
There was a significant seasonal difference. Therefore, to avoid inappropriate pooling each successive factor was analysed for each season separately and each variable
required a Ln transformation. Both E
. mathaei densities and substrate types failed a priori tests and subsequent transformation attempts, therefore the non-parametric
Kruskal–Wallis one-way ANOVA was used to test the hypotheses that there were no significant differences in 1 E
. mathaei densities among locations, between windward and leeward reefs and between depths, and 2 percentage net weight change according
to substrate type. Least-squares regression analyses were undertaken to examine whether there was a functional relationship between net weight carbonate change in the summer
season and the density of E . mathaei type A. An arcsinsqrtx transformation was
applied to the percentage cover of calcareous organisms on the tiles and each factor was subsequently tested via one-way ANOVA separately and pooled only when significant
differences were not apparent.
3. Results
3.1. Net weight carbonate changes A total of 45 of the tiles remained attached in summer, and 83 in winter. Among
the 307 tiles collected, only two tiles were found to have extensive boreholes. The weight of Porites carbonate tiles increased at all sites except at Location 1 1 m. Net
weight carbonate change was significantly different between seasons P ,0.001 Table 1. Significant differences were also apparent between locations in both seasons
P 50.005, P ,0.001 for summer and winter, respectively Fig. 2a and windward and leeward sites in the winter season P 50.012 Fig. 2b, but not between windward and
leeward sites in summer P 50.522 and between depths P 50.071, P 50.074 for summer and winter, respectively. More positive net weight changes were found in the
summer season than in the winter season for all locations, for windward and leeward reefs at both depths. Location 1 showed generally lower net increases than other
localities, and Location 2 showed higher net increases than other localities.
Table 1 One-way analysis of variance ANOVA for net weight carbonate change according to season
Effect df
MS F
P Season
1 916.3
13.0 ,0.001
Error 305
70.5
K . Hibino, R. van Woesik J. Exp. Mar. Biol. Ecol. 252 2000 1 –14
7
Fig. 2. Mean net weight change of experimental massive Porites spp. tiles a between different seasons and locations and b between different seasons and windward and leeward reefs. Data are mean6S.E. Treatment
results with the same letter above the error bar are not significantly different a 50.05 based on one-way ANOVA tests.
3.2. Echinometra mathaei densities The number of E
. mathaei type A exceeded the combined number of types B, C, and D at all localities except at 1 m on the windward side of Location 2 Table 2. The
density of E . mathaei type A was significantly different between locations H
587.1,
2,240
P ,0.001, windward and leeward reefs H 54.8, P50.028 and depths H
5
1,240 1,240
19.3, P ,0.001. Location 3 had significantly less E . mathaei type A than other
locations. Leeward reefs on average supported a higher density of E . mathaei type A
than windward reefs, and the 1-m habitat supported significantly more E . mathaei type
A than the 5-m habitat. There was a significant negative relationship between the density of E
. mathaei type A and net weight carbonate change of the tiles in the summer season
2
R 50.21, P 50.039, n 521 Fig. 3. This relationship was stronger when one outlier
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. Hibino, R. van Woesik J. Exp. Mar. Biol. Ecol. 252 2000 1 –14 Table 2
Mean Echinometra mathaei densities and percentage hard coral cover in replicate quadrats n 520
2
Echinometra mathaei density m Hard coral
cover Type A
Other types mean 6S.E.
mean 6S.E. mean 6S.E.
Location 1 Windward
1 m 29.0 62.5
0.1 60.1 4.1 61.6
Site 1 5 m
2.5 60.5 0.9 60.4
8.8 61.8 Leeward
1 m 22.3 62.8
0.6 60.2 1.3 60.7
Site 2 5 m
12.3 62.1 0.0
1.3 60.6 Location 2
Windward 1 m
4.2 61.2 9.4 61.4
22.8 62.4 Site 1
5 m 8.3 60.9
0.0 28.1 63.4
Leeward 1 m
15.4 62.0 0.1 60.1
19.1 62.9 Site 2
5 m 5.3 60.9
0.0 26.9 63.7
Location 3 Windward
1 m 4.8 62.1
0.4 60.2 31.9 66.7
Site 1 5 m
0.1 60.1 0.0
71.9 64.4 Leeward
1 m 1.8 60.4
0.7 60.2 47.8 65.2
Site 2 5 m
0.9 60.2 0.0
22.5 63.3
representing station 2 of the 1-m habitat, leeward, Location 2; marked with an arrow in
2
Fig. 3 was removed R 50.39, P 50.003, n 520. 3.3. Accretion
Coralline algal cover on massive Porites spp. tiles exceeded other calcareous
Fig. 3. Simple linear regression of Echinometra mathaei type A density and net weight change on experimental massive Porites spp. tiles during the 1996 summer season. One circle represents 10 replicate
quadrat samples of E . mathaei and replicate tiles at each depth per station n521. The dashed lines show the
95 confidence limits for the regression line; the arrow points to an outlier, which when removed changed the
2 2
2
variance expressed, or R , from R 50.21 P 50.039 to R 50.39 P 50.003.
K . Hibino, R. van Woesik J. Exp. Mar. Biol. Ecol. 252 2000 1 –14
9
encrusters in percentage space occupation mean values; 13.7 and 0.8 for coralline algae and other encrusters, respectively. Coralline algal cover also varied significantly
between seasons P 50.013, among locations P 50.032 and P ,0.001 for summer and winter, respectively Fig. 4a, and between windward and leeward reefs P 50.001 and
P ,0.001 for summer and winter, respectively Fig. 4b, but did not significantly differ between depths P 50.141 and P 5137 for summer and winter, respectively. The
summer months had higher coralline algal cover 15.7 than winter months 12.6. Highest coralline algal cover occurred at Location 3 Fig. 4a. Windward reefs, on
average, revealed a higher coverage than leeward reefs Fig. 4b. Coralline algal cover
2
was not significantly correlated with net weight carbonate change R 50.09, P 50.155, n 524.
Fig. 4. Mean coralline algal cover on experimental massive Porites spp. tiles a between different seasons and locations and b between different seasons and windward and leeward reefs. Data are mean6S.E. Treatment
results with the same letter above the error bar are not significantly different a 50.05 based on one-way ANOVA tests.
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. Hibino, R. van Woesik J. Exp. Mar. Biol. Ecol. 252 2000 1 –14
3.4. Substrate type Experiments undertaken in the lee of Location 1 showed that all three substrates,
Holocene Porites, Holocene A . hyacinthus, and Pleistocene, decreased in weight except
for Porites tiles at 5 m. The percentage of net weight change varied significantly among substrate types H
510.0, P50.007. A. hyacinthus was more resistant to net weight
2, 93
loss than either massive Porites or Pleistocene carbonate Fig. 5a. The amount of coralline algae encrusting the different substrates also differed significantly H
5
2, 93
13.2, P 50.001. Porites tiles showed generally lower coralline algal accumulation than Acropora and Pleistocene tiles, especially at 1 m Fig. 5b, which was coincident with
high net weight loss Fig. 5a,b.
Fig. 5. a Mean percentage net weight changes of three substrate types at two depths in the winter season at Location 1, site 2. b Mean coralline algal cover on three substrate types at two depths. Data are mean6S.E.
Treatment results with the same letter above the error bar are not significantly different a 50.05 based on paired Kruskal–Wallis tests.
K . Hibino, R. van Woesik J. Exp. Mar. Biol. Ecol. 252 2000 1 –14
11
4. Discussion
