Research ArticleECOLOGY

Coral reef diversity losses in China’s Greater Bay Area were driven by regional stressors

See allHide authors and affiliations

Science Advances  02 Oct 2020:
Vol. 6, no. 40, eabb1046
DOI: 10.1126/sciadv.abb1046
  • Fig. 1 Map of Hong Kong SAR.

    (A) Close-up of the study area and the sampling effort. Elongated rectangles denote locations where replicate sediment push cores were taken, and circles denote areas where replicate benthic transects were surveyed. The sampling effort is separated into the South region (red hues) and the East region (blue hues) for analysis. Cores with 14C dated subfossils are labeled next to their sampling location. (B) The study area and its location in the southeastern portion of the GBA of China, approximately 700 km from the coral triangle. (B) also highlights the Pearl River watershed that discharges just west of Hong Kong into the Pearl River Estuary. (C) Close-up of the area and sampling effort for coral surveys from the 1980s. The gray circles and the black outlined triangles highlight the northwest area of Mirs Bay and Tolo Harbor survey sites, used to produce Fig. 3 (A and B). Descriptions of the data and analyses used to produce figures throughout this study are detailed in the table below the map.

  • Fig. 2 Coral community composition through time.

    (A) Observed generic richness between the South and East regions in the past (subfossil) and modern (transect) datasets. The Chao2 diversity index was used to extrapolate generic richness for the region. The error bars represent 95% confidence intervals. A log transformation was used for all estimators so that the lower bound of the resulting interval is at least the number of observed species. Asterisks indicate significant differences in coral diversity in the modern data. (B) Relative abundances of coral from the South and East regions in Hong Kong, for subfossil and modern data. The dashed lines separate the genera into three different coral life-history strategies as outlined in Darling et al. (72): competitive, weedy, and stress tolerant. The two genera Goniopora and Lithophyllon were not included in the Darling et al. (72) analysis and are not grouped accordingly. The error bars represent 95% confidence intervals.

  • Fig. 3 Recent declines in coral communities.

    (A) Generic richness and coral cover for the northwest area of Mirs Bay (gray) and Tolo Harbor (white). Data were pooled into four time bins based on available surveys collected from 1980 to 2013 (56, 6471). Asterisks indicate significant differences in means from the first surveys in 1980. (B) Proportion of sites that recorded Acropora for all surveys from (A) combined. Jittered points for each time bin represent the raw presence/absence data (1 or 0, respectively) and are color-coordinated to locations from (A) (Northwest Mirs Bay: gray; Tolo Harbor: black with white outline). The error bars represent 95% confidence intervals. The sizes of the Acropora animations are proportional to 1980, which represents presence in 75% of surveys. The asterisk indicates significant differences in means from the first surveys in 1980.

  • Fig. 4 Acropora range contraction within the Hong Kong SAR.

    This map encompasses the same study area as Fig. 1, with the Pearl River discharging to the west. Red filled circles indicate sites where live Acropora were found during diving surveys; white open circles indicate areas where Acropora subfossils were found among seafloor sediments during dive surveys, or on the nearest beach. Asterisks indicate sites where no live or dead Acropora were found. The red dashed line and light-red shaded area are interpolations of the past and modern Acropora range, respectively. The past range determination was made by considering sites where only subfossils were found to be those that have hosted live Acropora in the past, but presently do not support live populations.

  • Fig. 5 nMDS of coral community composition.

    (A) nMDS showing subfossil (black) and modern (light gray) community composition data for East (circles) and South (triangles) regions. Ellipses are of SD. (B) Stress vectors created using envfit with the coral genera scores, shown only for genera that are statistically significant in driving the spread shown in the nMDS.

  • Fig. 6 nMDS of modern coral community composition versus EPD water quality parameters.

    (A) Modern coral community and water quality data (table S2) were combined based on their EPD grids in fig. S3. Ellipses represent SD ordinance ellipses. Stress vectors using envfit were calculated from the EPD water quality data and overlaid onto the coral composition data. Only the water quality parameters that were significantly driving coral composition were plotted. (B) Stress vectors created using envfit with the coral genera scores, shown only for genera that are statistically significant in driving the spread shown in the nMDS.

Supplementary Materials

  • Supplementary Materials

    Coral reef diversity losses in China’s Greater Bay Area were driven by regional stressors

    Jonathan D. Cybulski, Stefan M. Husa, Nicolas N. Duprey, Briony L. Mamo, Toby P. N. Tsang, Moriaki Yasuhara, James Y. Xie, Jian-Wen Qiu, Yusuke Yokoyama, David M. Baker

    Download Supplement

    This PDF file includes:

    • Supplementary Methods
    • Figs. S1 to S5
    • Tables S1 to S5

    Files in this Data Supplement:

Stay Connected to Science Advances

Navigate This Article