Data from: When environmental factors become stressors: interactive effects of vermetid gastropods and sedimentation on corals

Environmental stressors often interact, but most studies of multiple stressors have focused on combinations of abiotic stressors. Here we examined the potential interaction between a biotic stressor, the vermetid snail Ceraesignum maximum, and an abiotic stressor, high sedimentation, on the growth of reef-building corals. In a field experiment, we subjected juvenile massive Porites corals to four treatments: (i) neither stressor, (ii) sedimentation, (iii) vermetids or (iv) both stressors. Unexpectedly, we found no effect of either stressor in isolation, but a significant decrease in coral growth in the presence of both stressors. Additionally, seven times more sediment remained on corals in the presence (versus absence) of vermetids, likely owing to adhesion of sediments to corals via vermetid mucus. Thus, vermetid snails and high sedimentation can interact to drive deleterious effects on reef-building corals. More generally, our study illustrates that environmental factors can combine to have negative interactive effects even when individual effects are not detectable. Such ‘ecological surprises' may be easily overlooked, leading to environmental degradation that cannot be anticipated through the study of isolated factors.

环境胁迫因子（environmental stressor）通常存在交互作用，但目前多数多重胁迫因子研究多聚焦于非生物胁迫因子（abiotic stressor）的组合效应。本研究探讨了一种生物胁迫因子——蛀𧊕螺（vermetid snail, *Ceraesignum maximum*）与非生物胁迫因子——高沉积作用对造礁珊瑚（reef-building coral）生长的潜在交互效应。本研究通过野外实验（field experiment），将块状滨珊瑚（Porites）幼体设置为四组处理：（i）无胁迫组，（ii）高沉积组，（iii）蛀𧊕螺胁迫组，（iv）双重胁迫组。出乎意料的是，单一胁迫因子未对珊瑚生长产生显著影响，但当两种胁迫因子共同存在时，珊瑚生长量显著下降。此外，有蛀𧊕螺存在时，珊瑚表面留存的沉积物量是无蛀𧊕螺组的7倍，这可能源于沉积物通过蛀𧊕螺分泌的黏液粘附于珊瑚表面。综上，蛀𧊕螺与高沉积作用可产生交互作用，对造礁珊瑚造成有害影响。从更普遍的意义上来说，本研究表明，即便单一环境因子的效应无法被检测到，多种环境因子组合仍可能产生负面的交互效应。这类‘生态意外’往往极易被忽视，若仅通过单一因子的研究开展环境评估，将无法预判此类环境退化问题。