Biomass loss and change in species dominance shift stream community excretion stoichiometry during severe drought
Biomass loss and change in species dominance shift stream community excretion stoichiometry during severe drought
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严重干旱期间生物量损失和物种优势的变化改变了河流群落排泄化学计量
DOI：
10.1111/fwb.13433
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发表时间：
2019
影响因子：
2.7
通讯作者：
Bruckerhoff, Lindsey A.
中科院分区：
文献类型：
--
作者：
Hopper, Garrett W.;Gido, Keith B.;Pennock, Casey A.;Hedden, Skyler C.;Guinnip, James P.;Fisher, Molly A.;Tobler, Courtney M.;Hedden, Crosby K.;Bruckerhoff, Lindsey A.
动物通过排泄对营养循环做出了重大贡献，但大多数研究都考虑了它们在相对良性的非生物条件下的影响。干旱等干扰可能会通过物种组成和生物量的变化来改变动物的营养贡献。水源溪流特别容易受到极端气候事件的影响，因此可能会表现出溪流生物群及其生态系统效应的快速变化。我们测试了干旱期间间歇性草原溪流群落的生物量和随后的生态系统效应(养分循环)是如何变化的。我们量化了12个孤立池塘中由鱼、小龙虾和蝌蚪组成的群落的生物量和对营养循环的贡献，时间跨度为3个月，包括美国KS国王克里克有记录以来最严重的干旱。我们预测，大消费者生物量将随着池塘表面积的下降而下降，大消费者生物量和分类组成的差异将导致池集合对营养循环的不同贡献。池集合的生物量随着池塘规模的减小而下降，这种模式显然是由死亡、迁出或变形驱动的。我们还观察到干旱期间干燥池的组合结构相对于池大小的变化，将优势转移到具有更多抗旱特性的物种。因此，随着池塘生物量的减少，聚集态氮(N)的排泄率下降，导致表层生物膜可利用的N减少了58%。磷(P)排泄率从6-7月下降，但在8月增加，因为排磷率高的物种保持了相似的生物量比例，而非本地鱼的生物量增加。在整个干旱过程中，池塘组合的摩尔N：P排泄量显著下降，并与南方红腹鱼的丧失相吻合。动物介导的营养循环因生物量和化学计量学特征的丧失而改变，这些分类群在干旱期间的出现和耐受非生物条件的能力不同。在干旱条件下，孤立水池中溶解氮有效性的提高可能会增加生物膜对N的吸收速率，这表明聚集的大消费者，特别是具有独特化学计量特征的大消费者排泄的N的重要性。虽然淡水群落组成向生态系统转变的重要性并不完全为人所知，但在发生严重干旱之后，生态系统功能的进一步损失和群落结构的变化可能会出现。
Animals contribute significantly to nutrient cycling through excretion, but most studies consider their effects under relatively benign abiotic conditions. Disturbances such as drought may alter animals’ nutrient contributions through shifts in species composition and biomass. Headwater streams are particularly vulnerable to extreme climate events and thus might show rapid changes in stream biota and their ecosystem effects.We tested how biomass and subsequent ecosystem effects (nutrient cycling) of an intermittent prairie stream community changed during a drought. We quantified the biomass and contributions to nutrient cycling for assemblages comprising fishes, crayfish, and tadpoles in 12 isolated pools over 3 months encompassing the harshest drought on record for Kings Creek, KS, U.S.A. We predicted that macroconsumer biomass would decline with pool surface area and that differences in macroconsumer biomass and taxonomic composition would lead to different contributions of pool assemblages to nutrient cycling.The biomass of pool assemblages declined with decreasing pool size, a pattern apparently driven by mortality, emigration, or metamorphosis. We also observed a change in assemblage structure of drying pools during drought relative to pool size, shifting dominance toward species with more drought‐resistant traits. Accordingly, assemblage nitrogen (N) excretion rates declined as pool biomass was reduced, leading to a 58% reduction in N available to epilithic biofilms. Phosphorus (P) excretion rates declined from June to July, but increased in August, as species with high P excretion rates maintained similar proportional biomass and biomass of a non‐native fish increased. Molar N:P of pool assemblage excretion declined significantly throughout the drought and coincided with loss of southern redbelly dace (Chrosomus erythrogaster: Cyprinidae).Animal‐mediated nutrient cycling was altered by the loss of biomass and stoichiometric traits of taxa that differed in their occurrences and ability to tolerate abiotic conditions during drought. Elevated availability of dissolved N in isolated pools may increase N uptake rates by biofilms during drought conditions, indicating the importance of N excreted by aggregated macroconsumers, especially those with unique stoichiometric traits. While the significance of shifts in the composition of freshwater communities to ecosystems is not entirely known, additional losses in ecosystem function and changes in community structure may follow episodes of severe drought.
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