Table_1_Nutrient Pollution and Predation Differentially Affect Innate Immune Pathways in the Coral Porites porites.docx

Reef-building corals face a multitude of threats not only from global climate change but also local stressors such as nutrient pollution. Nutrient enrichment can amplify the negative effects of predation on corals by facilitating dysbiosis in the coral microbiome that leads to coral mortality. These patterns suggest that nutrient pollution might suppress the capacity of the coral immune system to respond to microbial infections that follow mechanical injury from predation. Here, we measured the impact of nutrient enrichment and predation on tyrosinase-type and laccase-type phenoloxidase (PO) activities, which are key components of immune defense pathway involved in melanin synthesis and wound healing in corals. Corals were exposed in situ to either ambient or enriched nutrient levels in combination with either no damage, mechanical damage, or predation damage from parrotfishes. The activity of PO enzymes in response to both tyrosinase-type substrates significantly decreased under nutrient enrichment, suggesting that corals became immune-compromised. Predation damage also increased laccase activity, implicating it in tissue repair and potentially defense from pathogens. Our findings highlight the need to mitigate nutrient pollution on coral reefs, as higher nutrient levels suppress important coral immune pathways and likely contribute to patterns of increased coral disease and subsequent mortality on reefs plagued by nutrient enrichment.

构建珊瑚礁的珊瑚物种不仅面临着全球气候变化带来的诸多威胁，亦承受着诸如营养污染等局部压力源的影响。营养富集通过促进珊瑚微生物群落的失调，加剧了对珊瑚捕食的负面影响，从而导致了珊瑚的死亡。这些模式表明，营养污染可能抑制了珊瑚免疫系统对捕食后机械损伤引发的微生物感染的反应能力。在本研究中，我们测量了营养富集和捕食对酪氨酸酶型和木聚糖型酚氧化酶（PO）活性的影响，这些酶是参与黑色素合成和珊瑚伤口愈合的免疫防御途径中的关键成分。珊瑚在原位暴露于环境或富集的营养水平，并结合无损伤、机械损伤或来自鹦鹉鱼的捕食损伤。在营养富集下，对酪氨酸酶型底物的PO酶活性显著降低，这表明珊瑚的免疫功能受损。捕食损伤还增加了木聚糖酶活性，暗示其在组织修复和可能防御病原体中的作用。我们的研究结果突显了减轻珊瑚礁上营养污染的必要性，因为较高的营养水平会抑制重要的珊瑚免疫途径，并可能加剧珊瑚疾病和随后的死亡模式，尤其是在营养富集的珊瑚礁上。