BackgroundPrevailing environmental conditions can modulate the structuring role of biotic interactions. In intertidal habitats, less stressful environmental conditions and/or higher grazer densities may allow grazing effects to be stronger in tide pools than on emergent rocks. To test this hypothesis, we conducted a manipulative experiment on an intertidal rocky shore in Fildes Bay, King George Island, in which the effect of the dominant grazer Nacella polaris on the structure of benthic periphyton communities was compared between emergent rock and tide pool habitats. Also, we determined the spatial variation in density, weight, and maximum length of individuals of N. polaris in both habitats.ResultsThe density of N. polaris was significantly larger in tide pools than on emergent rocks. Contrarily, we observed no significant differences in morphological parameters of N. polaris between both habitats or between intertidal elevations. In the manipulative study, we observed a greater taxonomic richness, diversity, and abundance of periphyton on emergent rocks than in tide pools. These variables also showed, in comparison with control areas, significantly higher values in experimental areas where herbivores were excluded by means of stainless-steel fences. The effects of habitat and grazer exclusion treatments were independent of each other, as no statistically significant interaction between both factors was observed.ConclusionsOur results showed significant, but independent, effects of tide pool habitats and grazing on the early colonisation of these assemblages. Albeit the grazing effects of other herbivores such as amphipods and small gastropods cannot be ruled out, we suggest that traits of N. polaris, such as high mobility and circadian activity, allow this species to exert a firm control on the intertidal Antarctic assemblages across local environmental conditions.

中文翻译：

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放牧和潮汐池栖息地对南极半岛西部潮间带群落早期殖民的独立影响

背景普遍存在的环境条件可以调节生物相互作用的结构作用。在潮间带栖息地，压力较小的环境条件和/或较高的食草动物密度可能使潮汐池中的放牧效应比在涌出的岩石上更强。为了验证这一假设，我们在乔治王岛费尔德斯湾的潮间带岩石海岸上进行了一项操纵性实验，其中比较了新兴岩石和潮汐池栖息地之间优势食草动物 Nacella polaris 对底栖附着生物群落结构的影响。此外，我们还确定了两个栖息地中北极猪的密度、体重和最大长度的空间变化。结果 北极猪的密度在潮汐池中明显大于在涌出的岩石上的密度。相反，我们观察到两个栖息地之间或潮间带海拔之间的北极猪的形态参数没有显着差异。在操纵性研究中，我们观察到，与潮汐池相比，涌出岩石上的附生生物分类丰富度、多样性和丰度更高。这些变量还显示，与对照区域相比，在通过不锈钢围栏排除食草动物的实验区域中，数值明显更高。栖息地和食草动物排斥处理的影响是相互独立的，因为没有观察到两个因素之间具有统计学意义的相互作用。结论我们的结果表明潮池栖息地和放牧对这些组合的早期定植有显着但独立的影响。