Wootton J T, Power M E, Paine R T, Pfister C A
Department of Ecology and Evolution, University of Chicago, 1101 East 57th Street, Chicago, IL 60637, USA.
Proc Natl Acad Sci U S A. 1996 Nov 26;93(24):13855-8. doi: 10.1073/pnas.93.24.13855.
We experimentally manipulated nutrient input to a rocky intertidal community, using nutrient-diffusing flowerpots, to determine (i) whether nutrients limited intertidal productivity, (ii) how a large-scale oceanographic disturbance (an El Niño event) affected patterns of nutrient limitation, (iii) the relative impacts of molluscan grazers and nutrient limitation, and (iv) if responses to experimental nutrient addition among trophic levels were more consistent with prey-dependent or ratio-dependent food chain models. Nutrients measurably increased the abundance of micrograzers (amphipods and chironomid larvae), but not algal biomass, during the summer of an El Niño year. Nutrients had no effects in two non-El Niño years and during the autumn of an El Niño year. Adding nutrients did not affect food chain stability as assessed by temporal variation in algal biomass and micrograzer abundance. Large molluscan grazers caused large reductions in micrograzers and smaller reductions in algae, indicating consistent consumer effects. The results demonstrate that in this intertidal community, nutrient limitation can occur under conditions of nutrient stress, that top-down grazing effects are typically stronger than bottom-up nutrient effects, and that prey-dependent models are more appropriate than ratio-dependent models.
我们利用营养扩散花盆对一个岩石潮间带群落的养分输入进行了实验性操控，以确定：（i）养分是否限制潮间带生产力；（ii）大规模海洋学扰动（厄尔尼诺事件）如何影响养分限制模式；（iii）软体食草动物和养分限制的相对影响；以及（iv）各营养级对实验性养分添加的反应是否更符合猎物依赖型或比率依赖型食物链模型。在厄尔尼诺年的夏季，养分显著增加了微型食草动物（端足类动物和摇蚊幼虫）的数量，但对藻类生物量没有影响。在两个非厄尔尼诺年以及厄尔尼诺年的秋季，养分没有产生影响。添加养分并未影响通过藻类生物量和微型食草动物数量的时间变化评估的食物链稳定性。大型软体食草动物导致微型食草动物数量大幅减少，藻类数量减少幅度较小，表明消费者效应具有一致性。结果表明，在这个潮间带群落中，在养分胁迫条件下可能会出现养分限制，自上而下的放牧效应通常比自下而上的养分效应更强，并且猎物依赖型模型比比率依赖型模型更合适。
