Figure 1.
Location of Okinawa Island and monthly means of sea surface temperature (SST) during the period 1994–2009.
(A) Okinawa Island, located on the Ryukyu Islands in the Northwest Pacific. Open circles and numbers show the study sites. Location of Sesoko Island characterized by non-turbid reefs is also shown in the figure. (B) Sea surface temperatures were observed at Motobu Peninsula, central Okinawa Island. Data are from the Japan Oceanographic Data Center (http://www.jodc.go.jp/data/coastal/obs_data_index.html) and the Geological Survey of Hokkaido (http://www.gsh.pref.hokkaido.jp/download/temperature_data/index.html). Two thermal stress events, in 1998 and 2001, are indicated by arrows.
Figure 2.
Observed changes in the percent coral cover (mean ± SD) on Okinawa Island reefs from 1995 to 2009 (excluding 1997, during which no surveys were conducted).
The number of study sites each year is shown in Table S1.
Figure 3.
Temporal changes in the abundance of genera (m−2) on Okinawa Island during the period 1995–2009.
(A): Acropora, (B): Stylophora, (C): Pocillopora, (D): Millepora, (E): Stylocoeniella, (F): Dipsastraea, (G): Favites, (H): Goniastrea, (I): Leptastrea, (J): Montipora, (K): Pavona, and (L): Porites. Significant changes (asterisks) in the abundance were determined by Kruskal–Wallis test. Other genera are shown in Table S3.
Figure 4.
Generic rank in abundance from 1995 to 2001 (A) and the period 2002–2009 (B); a comparison of rankings for the two time periods represents the effects of severe thermal stress events in 1998 and 2001.
Abundances for each genus are shown in Table S3. Some notable genera are shown in colored fonts.
Figure 5.
Temporal trends in the abundances of species and species complexes (m−2) on Okinawa Island reefs from 1995 to 2009.
(A): Acropora digitifera, (B): Acropora hyacinthus/cytherea, (C): Acropora intermedia/muricata, (D): Pocillopora damicornis, (E): Stylophora pistillata, (F): Dipsastraea pallida/speciosa/favus, (G): Goniastrea aspera, (H): Leptastrea purpurea, (I): Montipora digitata, (J): Oulastrea crispata, (K): Porites cylindrica, and (L): Porites lutea/australiensis. Significant changes (asterisks) in the abundance were determined by Kruskal–Wallis test. Other species are shown in Table S3.
Figure 6.
Specific rank in abundance from 1995 to 2001 (A) and from 2002 to 2009 (B); a comparison of rankings for the two time periods represents the effects of severe thermal stress events in 1998 and 2001.
Abundances for each species are shown in Table S3. Some notable species are shown in colored fonts. Species rank in abundance for all species (included identified species and spp.) are also shown in the figure.
Figure 7.
Conceptual model response to thermal stresses on anthropogenically turbid reefs (A), naturally turbid reefs (B), and clear-water reefs (C).
Given the result of this study, the model would be most applicable to western Pacific region. (A) Tabular (ta.) and branching (br.) Acropora (e.g., A. digitifera) from anthropogenically turbid reefs, influenced by recent increasing terrestrial runoff, are intolerant to severe thermal stresses and no recovery as a result of low resistance and low resilience and no adaptation to a condition of turbid. (B) Tabular and branching Acropora and massive corals from naturally turbid reefs, adapted to a condition of turbid, are tolerant to severe thermal stresses as a result of high resistance and high resilience. (C) Tabular and branching Acropora from clear-water reefs are intolerant to severe thermal stresses as a result of low resistance, but the coral recover the abundance as a result of high resilience. Massive corals are generally tolerant to thermal stresses. Corals are symbolized in coaches in blue (tabular and branching Acropora) and in yellow (massive corals). Thermal stresses are symbolized in some slopes in the railway.