1
ESM: Water flow
2
We obtained rough estimates of the water flow at each sampling location to identify whether there
3
were any obvious differences in water flow among coral categories. Water flow was estimated by
4
measuring the number of seconds that it took a 20 ml volume of red dye to traverse 1 m, and is
5
reported in m s-1. Five measurements were taken at each of the 12 locations at the time of sampling for
6
ecological data. The effect of coral category location on flow was examined using a linear mixed
7
effects model with site (1–4) as a random factor. Categories were locations with corals absent in
8
satellite imagery both before and after subsidence (Absent), corals absent before and present after
9
subsidence (Change) and corals present both before and after subsidence (Present). From this analysis
10
we inferred whether there were any substantial differences in water flow among the Absent, Present,
11
and Change locations.
12
There was no significant effect of coral category on flow (Table 1; Fig.1), suggesting that variations
13
in water flow did not affect whether coral colonized some locations and not others following
14
subsidence. However, data should be interpreted with caution, as water flow varies substantially over
15
coral reef flats depending on wind and tidal conditions, which were not controlled for in this study.
16
Furthermore, to provide conclusive evidence of the effect of water flow on colonization of the reef
17
flat, water flow measurements before and after subsidence would have been required, which were not
18
possible given the circumstances.
19
Table 1 Results of generalized linear mixed-effects models (fixed effects only) for water flow (m s-1)
20
observed in three location categories [corals absent in satellite imagery both before and after
21
subsidence (Absent), corals absent before and present after subsidence (Change) and corals present
22
both before and after subsidence (Present)] on the coral reef flat in Roviana Lagoon, Western
23
Province, Solomon Islands, in May 2013. Estimates are model coefficients, reported with standard
24
errors (SE) and t values.
Estimate
Fixed Effects
SE
t value
Flow
Intercept (Absent)
Change
Present
Pairwise comparisons
0.1202
-0.0074
-0.0076
0.035000
0.013352
0.013352
3.434
-0.555
-0.570
Absent = Change = Present
25
26
2
27
28
29
Fig. 1 Variability in water velocity (m s-1) among location categories on the reef flat at Kundu Kundu,
30
Roviana Lagoon, Solomon Islands, where 0.6 m subsidence occurred in 2007. Absent: corals absent
31
in satellite imagery both before and after subsidence, Change: corals absent before and present after
32
subsidence, Present: corals present both before and after subsidence
33
34
3