The filamentous chlorophyte Ostreobium sp. dominates shallow marine carbonate microboring communities, and is one of the major agents of reef bioerosion. While its large genetic diversity has emerged, its physiology remains little known, with unexplored relationship between genotypes and phenotypes (endolithic versus free‐living growth forms). Here, we isolated nine strains affiliated to two lineages of Ostreobium (>8% sequence divergence of the plastid gene rbcL), one of which was assigned to the family Odoaceae, from the fast‐growing coral host Pocillopora acuta Lamarck 1816. Free‐living isolates maintained their bioerosive potential, colonizing pre‐bleached coral carbonate skeletons. We compared phenotypes, highlighting shifts in pigment and fatty acid compositions, carbon to nitrogen ratios and stable isotope compositions (δ¹³C and δ¹⁵N). Our data show a pattern of higher chlorophyll b and lower arachidonic acid (20:4ω6) content in endolithic versus free‐living Ostreobium. Photosynthetic carbon fixation and nitrate uptake, quantified via 8 h pulse‐labeling with ¹³C‐bicarbonate and ¹⁵N‐nitrate, showed lower isotopic enrichment in endolithic compared to free‐living filaments. Our results highlight the functional plasticity of Ostreobium phenotypes. The isotope tracer approach opens the way to further study the biogeochemical cycling and trophic ecology of these cryptic algae at coral holobiont and reef scales.

中文翻译：

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从珊瑚中分离出的微孔性骨re藻的功能多样性

丝状绿藻Ostreobium sp。在浅海海洋碳酸盐微孔群落中占主导地位，是珊瑚礁生物侵蚀的主要因素之一。尽管已经出现了巨大的遗传多样性，但其生理学仍然鲜为人知，在基因型和表型（内吞型与自由生长型）之间的关系尚待探索。在这里，我们从快速生长的珊瑚寄主Pocillopora acuta中分离了9个菌株，这些菌株分别属于两个骨of系（> 8％的质体基因rbc L序列差异），其中一个属于Odoaceae家族。Lamarck1816。自由生存的分离物保持了其生物侵蚀的潜能，使预先漂白的碳酸钙骨架得以定殖。我们比较了表型，突出在颜料的变化和脂肪酸组合物，碳氮比和稳定同位素组合物（δ ¹³ C和δ ¹⁵ N）。我们的数据显示，与自由生活的骨生骨灰质相比，内石器中叶绿素b含量较高和花生四烯酸（20：4ω6）含量较低的模式。光合碳固定和硝酸盐吸收，通过8 h脉冲标记用¹³ C-碳酸氢盐和^15进行定量与自由活动的细丝相比，N-硝酸盐显示出较低的同位素富集。我们的结果突出了Ostreobium表型的功能可塑性。同位素示踪法为进一步研究这些隐藻的珊瑚地球和珊瑚礁尺度的生物地球化学循环和营养生态学开辟了道路。