Aumack Craig F, Amsler Charles D, McClintock James B, Baker Bill J
Department of Biology, University of Alabama at Birmingham, Birmingham, Alabama, 35294-1170, USADepartment of Chemistry, University of South Florida, Tampa, Florida 33620, USA.
J Phycol. 2011 Feb;47(1):36-41. doi: 10.1111/j.1529-8817.2010.00927.x. Epub 2010 Dec 6.
It has been hypothesized that the extensive mesograzer community along the western Antarctic Peninsula regulates epiphytic algae as well as emergent filaments from endophytic species. Should grazing limit growth of fouling or potentially pathogenic microphytes, then Antarctic macrophytes may actually benefit from the remarkably high densities of mesograzer amphipods that occur in these waters. Although initially counterintuitive, the negative impacts of epi/endophyte fouling may outweigh stresses caused by limited amphipod grazing on chemically defended macrophytes by reducing stress from endo/epiphyte biomass. If so, then alleviating mesograzing stress should result in significant increases in endo/epiphytic biomass. To test this hypothesis, a mesocosm experiment was conducted. Individuals representing four common species of Antarctic macroalgae were placed in flow-through seawater mesocosms. Amphipods were added to five mesocosms at simulated natural densities, while the other five remained herbivore free. At the end of 7 weeks, endo/epiphytic growth on individual macrophytes was quantified. Most species of macroalgae demonstrated noticeably higher instances of endophyte coverage, epiphytic diversity, and diatom colonization in consumer-free mesocosms than in the presence of amphipods. These data suggest that macroalgae along the western Antarctic Peninsula rely on grazers to control populations of potentially harmful epiphytes. We hypothesize that the chemically defended macroalgal flora lives in mutualism with high densities of mesograzers, providing amphipods with shelter from predation while continually being cleaned of potentially harmful endo/epiphytes.
据推测，南极半岛西部广泛分布的中型食草动物群落对附生藻类以及内生物种的丝状藻起着调节作用。如果食草行为限制了污损生物或潜在致病微生物的生长，那么南极大型植物实际上可能会受益于这些水域中出现的高密度中型食草动物双壳类动物。尽管这一观点乍一看有违直觉，但附生/内生生物污损的负面影响可能超过双壳类动物有限的啃食对具有化学防御能力的大型植物造成的压力，因为前者可减少内生/附生生物量带来的压力。如果真是这样，那么减轻中型食草动物的压力应该会导致内生/附生生物量显著增加。为了验证这一假设，我们进行了一项中宇宙实验。将代表四种常见南极大型藻类的个体放置在流通海水的中宇宙中。在五个中宇宙中以模拟自然密度添加双壳类动物，而其他五个中宇宙则不投放食草动物。在7周结束时，对各个大型植物上的内生/附生生物生长情况进行了量化。与有双壳类动物存在的情况相比，大多数大型藻类物种在无消费者的中宇宙中表现出明显更高的内生植物覆盖率、附生生物多样性和硅藻定殖率。这些数据表明，南极半岛西部的大型藻类依赖食草动物来控制潜在有害附生生物的数量。我们推测，具有化学防御能力的大型藻类植物群与高密度的中型食草动物共生，为双壳类动物提供躲避捕食的场所，同时不断清除潜在有害的内生/附生生物。
