Table 1. The comparison of sampling methods, area, replicate, depth, identification level, and the data used for PCA analysis of each historical data set.

Year	Survey method	Survey Unit	Number ofReplicates	Survey depth	Methods	Identification level	Data set forPCA analysis	Reference
1985	Photo quadrat	4.5 m 2	1	10	Colony area was estimate from severalphotographs taken to cover the quadrat.	Acropora, Montipora, Pocilloporidae,Poritidae, Faviidae, Heliopora coerulea and other corals. Algaewas not measured	All	[35]
1987 and 1999	Line intercept transect	10 m	25	3 ∼ 23	A transect tape was placed perpendicularto the coast and extended seaward from 3 mdepth to the reef edge at 25 m depth. A 10 mmetal chain was placed parallel to thetransect at 15 m intervals.	Species for Corals Total algae	Only transects between 5 and 10 m depth were used in the PCA	[24], [26]
2003∼2005 2008∼2010	Belt transects	7.5 m2	3	5 ∼ 10	Three permanent belt transects wereestablished along depth contours between5 and10 m. Benthic organisms were quantifiedusing 25×25-cm photo-quadrats (120 frames/30 m transect). The percent cover of thebenthic categories was determined usingCoral Count with Excel Extensions vers. 3.6 [42],with 30 random points per quadrat.Surveys were conducted between Marchand May each year.	Species for coralsMacroalgae Turf algae	All	[43]