Marine Ecology Research Group, School of Biological Sciences, University of Canterbury, Christchurch, New Zealand.
PLoS One. 2011;6(10):e26986. doi: 10.1371/journal.pone.0026986. Epub 2011 Oct 31.
Macroalgal assemblages are some of the most productive systems on earth and they contribute significantly to nearshore ecosystems. Globally, macroalgal assemblages are increasingly threatened by anthropogenic activities such as sedimentation, eutrophication and climate change. Despite this, very little research has considered the potential effects of canopy loss on primary productivity, although the literature is rich with evidence showing the ecological effects of canopy disturbance. In this study we used experimental removal plots of habitat-dominating algae (Order Fucales) that had been initiated several years previously to construct a chronosequence of disturbed macroalgal communities and to test if there were legacy effects of canopy loss on primary productivity. We used in situ photo-respirometry to test the primary productivity of algal assemblages in control and removal plots at two intertidal elevations. In the mid tidal zone assemblage, the removal plots at two sites had average primary productivity values of only 40% and 60% that of control areas after 90 months. Differences in productivity were associated with lower biomass and density of the fucoid algal canopy and lower taxa richness in the removal plots after 90 months. Low-shore plots, established three years earlier, showed that the loss of the large, dominant fucoid resulted in at least 50% less primary productivity of the algal assemblage than controls, which lasted for 90 months; other smaller fucoid species had recruited but they were far less productive. The long term reduction in primary productivity following a single episode of canopy loss of a dominant species in two tidal zones suggests that these assemblages are not very resilient to large perturbations. Decreased production output may have severe and long-lasting consequences on the surrounding communities and has the potential to alter nutrient cycling in the wider nearshore environment.
大型藻类组合是地球上生产力最高的系统之一，它们对近岸生态系统有重要贡献。在全球范围内，大型藻类组合越来越受到人为活动的威胁，如沉降、富营养化和气候变化。尽管如此，很少有研究考虑过树冠损失对初级生产力的潜在影响，尽管文献中有大量证据表明树冠干扰的生态影响。在这项研究中，我们使用了几年前开始的栖息地优势藻类（Order Fucales）的实验去除斑块来构建受干扰的大型藻类群落的时间序列，并测试树冠损失对初级生产力是否存在遗留效应。我们使用原位光呼吸测定法在两个潮间带高度的对照和去除斑块中测试藻类组合的初级生产力。在中潮带组合中，两个地点的去除斑块在 90 个月后的平均初级生产力值仅为对照区的 40%和 60%。生产力的差异与去除斑块中褐藻树冠的生物量和密度较低以及去除斑块中低等分类群的丰富度较低有关。建立于三年前的低岸斑块表明，大型优势褐藻的损失导致藻类组合的初级生产力比对照区至少减少 50%，这种情况持续了 90 个月；其他较小的褐藻物种已经招募，但它们的生产力要低得多。在两个潮带中，单一的优势物种树冠损失后，初级生产力长期减少，这表明这些组合对大的干扰不太具有弹性。生产输出的减少可能对周围社区产生严重和持久的影响，并有可能改变更广泛近岸环境中的养分循环。
