Petrochenko R.A.1, Lishchenko F.V.1,2, Nguyen T.H.2, Britayev T.A.1* 2025. Ectosymbiont community shifts driven by partial mortality in Pocillopora coral colonies // Invert. Zool. Vol.22. No.4. P.553–564 [in English].
1 Laboratory of Marine Invertebrate Morphology and Ecology, A.N. Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences (RAS), Moscow, Leninsky Prospect 33, 119071 Russia.
2 Coastal Branch of the Joint Vietnam-Russia Tropical Science and Technology Research Center, Nha Trang, Nguyễn Thiện Thuật 30, 650000 Vietnam.
* Corresponding author
Roman Petrochenko: petrochenko.roman.2017@post.bio.msu.ru
Fedor Lishchenko: fedor-ln@yandex.ru ORCID https://orcid.org/0000-0001-8340-346X
Hai Thanh Nguyen: haithanh_2008@yahoo.com ORCID https://orcid.org/0000-0001-7716-6859
Temir Britayev: britayev@yandex.ru ORCID https://orcid.org/0000-0003-4707-3496
doi: 10.15298/invertzool.22.4.03
ABSTRACT: Scleractinian corals host rich communities of specialized ectosymbiotic animals that can act as parasites or mutualists, thereby influencing coral health and survival. The structure of these communities is shaped by multiple environmental factors, many of which remain poorly understood. Here, we examine how partial mortality (PM) of live coral tissue affects the diversity and abundance of ectosymbionts in nursery-reared colonies of Pocillopora verrucosa. We tested the hypothesis that PM promotes a shift from obligate to facultative symbionts. We analyzed 200 one-year-old colonies, documenting colony metrics and bleaching status, and then collecting, counting, and identifying all associated symbionts. PM was observed in 36% (72) of colonies, with 62 surviving the entire experiment. Among these, only one showed PM on more than 75% of its surface, 48 on less than 25%, and 13 on 25–50%. Across all samples, we identified 79 ectosymbiotic species: 49 facultative and 17 obligate in colonies with PM, and 45 facultative and 14 obligate in healthy colonies. Generalized linear models revealed significant effects of PM and colony density on community structure, while bleaching exerted only a weak influence and colony size had no significant effect. Facultative symbionts were significantly richer and more abundant in colonies with PM, whereas obligate symbionts showed no detectable response. These contrasting patterns likely reflect differing ecological requirements and tolerance ranges of these two groups of symbionts. Our findings highlight PM as a key driver of symbiont community restructuring in P. verrucosa, with important implications for understanding coral-associated biodiversity and its resilience under environmental stress.
KEY WORDS: Pocillopora verrucosa, partial mortality, obligate symbionts, facultative symbionts, diversity, abundance.
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