Disease-Driven Amphibian Declines Alter Ecosystem Processes in a Tropical Stream
Disease-Driven Amphibian Declines Alter Ecosystem Processes in a Tropical Stream
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疾病导致的两栖动物数量减少改变了热带溪流的生态系统过程
DOI：
10.1007/s10021-012-9602-7
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发表时间：
2012
期刊：
影响因子：
3.7
通讯作者：
S. Connelly
中科院分区：
文献类型：
--
作者：
M. Whiles;R. Hall;W. Dodds;P. Verburg;A. Huryn;C. Pringle;K. Lips;S. Kilham;J. C. Colón;A. Rugenski;S. Peterson;S. Connelly
预测生物多样性下降的生态后果是一项紧迫的挑战，特别是在物种减少和损失最严重的淡水栖息地。小规模实验表明了生态系统对物种损失的潜在反应，但最终结论需要在更大范围内进行验证。我们测量了生态系统新陈代谢，并使用全生态系统稳定同位素示踪剂添加来量化两栖动物突然消失之前和之后热带源头溪流中的氮循环。在这种溪流中，蝌蚪通常是主要的食性动物，可共存18种以上，密度往往超过50只m−2。蝌蚪生物量损失98%对应于溪流中藻类和细碎屑生物量增加2倍以上，氮素吸收速率下降50%以上。悬浮和沉积有机沉积物中的氮素周转率在下降后也显著降低。因此，河流的氮循环速度变慢，下游颗粒态氮的出口也减少了。整个河流的呼吸作用在下降后显著降低，表明河流沉积物中的生物活性较低。与我们的预测相反，食草性无脊椎动物或任何无脊椎动物功能群的生物量在失去蝌蚪后的两年内没有增加。因此，与两栖类衰退有关的生态系统过程的减少并没有得到其他功能上多余的消费者的补偿。动物生物多样性的下降会产生生态系统层面的后果，生态冗余可能无法抵消这些后果，即使在新热带等生物多样性的地区也是如此。
Predicting the ecological consequences of declining biodiversity is an urgent challenge, particularly in freshwater habitats where species declines and losses are among the highest. Small-scale experiments suggest potential ecosystem responses to losses of species, but definitive conclusions require verification at larger scales. We measured ecosystem metabolism and used whole-ecosystem stable isotope tracer additions to quantify nitrogen cycling in a tropical headwater stream before and after the sudden loss of amphibians to the fungal pathogen Batrachochytrium dendrobatidis. Tadpoles are normally dominant grazers in such streams, where greater than 18 species may co-occur and densities often exceed 50 individuals m−2. Loss of 98% of tadpole biomass corresponded with greater than 2× increases in algae and fine detritus biomass in the stream and a greater than 50% reduction in nitrogen uptake rate. Nitrogen turnover rates in suspended and deposited organic sediments were also significantly lower after the decline. As a consequence, the stream cycled nitrogen less rapidly, and downstream exports of particulate N were reduced. Whole stream respiration was significantly lower following the decline, indicating less biological activity in the stream sediments. Contrary to our predictions, biomass of grazing invertebrates, or any invertebrate functional groups, did not increase over 2 years following loss of tadpoles. Thus, reductions in ecosystem processes linked to the amphibian decline were not compensated for by other, functionally redundant consumers. Declining animal biodiversity has ecosystem-level consequences that may not be offset by ecological redundancy, even in biologically diverse regions such as the Neotropics.