Japanese reefs show northernmost distribution of coral diseases
Pink spots disease and pink line response on Porites (Photo E. Weil)

Okiawa and the Kerama Islands, our survey localities, were two hours south by plane. I saw several disease conditions in corals and other organisms. Aside from bleaching which has affected reefs in Japan since the 1980s, few coral diseases have been reported from this region. Common conditions include growth anomalies (GAN), Porites pink block disease (PPBD), black band disease (BBD), and white syndrome (WS) affecting several species of Acropora, Porites, Montipora and Pachyseris. During these surveys however, I found Porites ulcerative white spots (PUWS), brown band disease (BrD) and crustose coralline white syndrome (CCWS), all new reports for Japan.

Several colonies of Porites lobata and P. lutea were observed with PUWS signs in both localities, which represents the northernmost distribution for this disease so far. Pink round spots (pigmentation response) that looked like PUWS lesions but larger and covered with a puffy pink, gel-like secretion were observed in massive Porites in both localities, some of them with PUWS signs.

Brown band disease-like signs produced by ciliates were observed in a couple of branches of Acropora formosa in the Kerama Islands – an expansion of the geographic distribution for this disease. Growth anomalies were the most prevalent in the Kerama Islands affecting table acroporids and Astreopora sp. BBD was observed on a couple of colonies of Pachyseris gemmae in Maehama, near Okinawa, and white syndrome affected several colonies of Acropora florida, A. cytherea and Pachyseris sp. in both localities.

Several massive Porites showed “compromised health conditions” associated with paling patterns and tissue mortality. Other organisms observed with disease signs included the soft coral Lobophyton sp. which had extensive bleached areas, loss of structure and decomposing tissues, and crustose coralline algae with signs similar to those of crustose coralline white syndrome.

These observations indicate that the northern-most coral reefs in the Pacific are susceptible to a higher number of coral diseases than previously thought and that attention must be given to this problem.  

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