DOI: 10.5061/dryad.0rxwdbs35
title: Fine intervals are required when using point intercept transects to assess coral reef status

description: The Point Intercept Transect (PIT) method has commonly been used in recent
 decades for estimating the status of coral reef benthic communities. It is
 a simple method that is efficiently performed underwater, as benthic
 components are recorded only as presence or absence at specific interval
 points along transects. Therefore, PIT is also popular in citizen science
 activities such as Reef Check programs. Longer intervals are commonly
 associated with longer transects, yet sampling interval length can
 significantly influence benthic coverage calculations. Despite this, the
 relative accuracy of longer or shorter intervals related to transect
 length has not been tested for PIT. In this study, we tested the optimum
 intervals of PIT for several commonly used transect lengths using the
 bootstrap method on empirical data collected on tropical coral reefs and
 non-reefal coral communities. Our results recommend fine intervals of
 10 cm or shorter, depending on the length of the transect, to
 increase the accuracy of estimating benthic community status on coral
 reefs. Permanent transects should also be considered in long-term
 monitoring programs to improve data quality.
description: This dataset was collected at
 six sites
 on four reefs across
 Taiwan’s tropical and subtropical regions between April and July
 2019. The two reefs in the tropical region
 were Tiaoshi in the
 south and Kihaw in the southeast of Taiwan Island. The other two reefs in the
 subtropical region were Chinwan Inner Bay in the Penghu
 Archipelago and
 Yehliu in
 northern
 Taiwan. The six sites included two depths in Yehliu (3 m and 6 m) and Tiaoshi (5 m and 10 m), but only one depth each in Kihaw
 (3 m) and Chinwan Inner Bay (3 m) because these two had no
 suitable reef
 communities located deeper
 than 5 m.  Three
 consecutive transects were placed, according to reef contouring,
 continuously a few meters apart along depth contours parallel to the
 shoreline at each site. Alternatively, three transects were deployed in
 parallel for short reefs. The standard transect length used in this
 dataset was 15 m. However, one transect at the shallow
 depth of Tiaoshi was 14 m long because of operator
 error. A total of
 18 transects at
 six sites were
 surveyed. We applied the ten categories of Reef
 Check’s Tropical Program
 protocol (Hodgson et al., 2006) to classify benthos and
 substrates, including hard
 coral (HC), soft coral (SC), recently killed coral (RKC), nutrient
 indicator algae (NIA), sponge (SP), rock (RC), rubble (RB), sand (SD),
 silt/clay (SI), and other substrates (OT). In addition, hard corals, including the
 scleractinians, <em>Heliopora </em>and <em>Millepora</em>, were identified to species level, and rock was divided into rock (RC), turf algae (TF), and crustose coralline algae (CCA). The quantification of each benthic category on each transect was first calculated using the Line Intercept Transect (LIT) method. Briefly, the substrate type at each sampling point with one cm interval was assigned to one of the categories above. The percentage cover of each category on each transect was calculated by dividing the cumulative points of the category by the total points of the transect (1400 or 1500 points for 14 or 15 m transects, respectively). 
description: Detailed information is listed in the
 "README_Kuo_et_al_2022_BenthicCommunityComposition_raw.txt"
 file.