Goose-mediated nutrient enrichment and planktonic grazer control in arctic freshwater ponds
Goose-mediated nutrient enrichment and planktonic grazer control in arctic freshwater ponds
复制标题
北极淡水池塘中鹅介导的营养富集和浮游食草动物控制
DOI：
10.1007/s00442-007-0770-7
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发表时间：
2007
期刊：
影响因子：
2.7
通讯作者：
E. van Donk
中科院分区：
文献类型：
--
作者：
G. V. van Geest;D. Hessen;P. Spierenburg;G. Dahl;G. Christensen;P. J. Faerøvig;M. Brehm;M. Loonen;E. van Donk
在过去的几十年里，在斯瓦尔巴群岛，鹅的繁殖数量急剧增加。这可能会严重影响北极苔原脆弱的生态系统，因为许多超贫营养淡水系统都从鹅粪中富集。我们调查了21个浅层冻土带池塘，沿着营养物富集的梯度，基于鹅的暴露。冻土带池塘中总磷(P)和溶解无机氮（DIN）的浓度分别为2-76 ~ 2-23 μg l−1，而浮游植物生物量（以叶绿素a测量，范围为0.6 ~ 7.3 μg l−1）沿养分梯度没有显著增加。这种缺乏反应可能是这些生态系统的营养结构的结果，在缺乏鱼类和缺乏无脊椎捕食者的情况下，这些生态系统只有一个双营养级食物链，其中有高生物量的高效浮游动物水蚤。我们的研究结果表明，这可能导致所有池塘中浮游植物的高效放牧控制，这一事实得到了大部分营养池与浮游动物生物量结合的事实的支持。水蚤-氮和水蚤-磷含量占颗粒（海相）氮和磷的中位数百分比分别为338和3009%，与温带湖泊相比极高。我们的数据表明，北极浅水池塘中的水蚤受到来自其他食物来源（细菌、底栖生物膜）的主要能量输入的大量补贴，这可能是水蚤持续对远洋藻类进行强有力的自上而下控制的关键。
A dramatic increase in the breeding population of geese has occurred over the past few decades at Svalbard. This may strongly impact the fragile ecosystems of the Arctic tundra because many of the ultra-oligotrophic freshwater systems experience enrichment from goose feces. We surveyed 21 shallow tundra ponds along a gradient of nutrient enrichment based on exposure to geese. Concentrations of total phosphorus (P) and dissolved inorganic nitrogen (DIN) in the tundra ponds ranged from 2–76 to 2–23 μg l−1 respectively, yet there was no significant increase in phytoplankton biomass (measured as chlorophyll a; range: 0.6–7.3 μg l−1) along the nutrient gradient. This lack of response may be the result of the trophic structure of these ecosystems, which consists of only a two-trophic level food chain with high biomasses of the efficient zooplankton grazer Daphnia in the absence of fish and scarcity of invertebrate predators. Our results indicate that this may cause a highly efficient grazing control of phytoplankton in all ponds, supported by the fact that large fractions of the nutrient pools were bound in zooplankton biomass. The median percentage of Daphnia–N and Daphnia–P content to particulate (sestonic) N and P was 338 and 3009%, respectively, which is extremely high compared to temperate lakes. Our data suggest that Daphnia in shallow arctic ponds is heavily subsidized by major inputs of energy from other food sources (bacteria, benthic biofilm), which may be crucial to the persistence of strong top–down control of pelagic algae by Daphnia.