Upper Midwest Environmental Sciences Center, United States Geological Survey, La Crosse, Wisconsin, United States of America.
PLoS One. 2013 Aug 5;8(8):e70666. doi: 10.1371/journal.pone.0070666. Print 2013.
Spatial variation in food resources strongly influences many aspects of aquatic consumer ecology. Although large-scale controls over spatial variation in many aspects of food resources are well known, others have received little study. Here we investigated variation in the fatty acid (FA) composition of seston and primary consumers within (i.e., among habitats) and among tributary systems of Lake Michigan, USA. FA composition of food is important because all metazoans require certain FAs for proper growth and development that cannot be produced de novo, including many polyunsaturated fatty acids (PUFAs). Here we sampled three habitat types (river, rivermouth and nearshore zone) in 11 tributaries of Lake Michigan to assess the amount of FA in seston and primary consumers of seston. We hypothesize that among-system and among-habitat variation in FAs at the base of food webs would be related to algal production, which in turn is influenced by three land cover characteristics: 1) combined agriculture and urban lands (an indication of anthropogenic nutrient inputs that fuel algal production), 2) the proportion of surface waters (an indication of water residence times that allow algal producers to accumulate) and 3) the extent of riparian forested buffers (an indication of stream shading that reduces algal production). Of these three land cover characteristics, only intense land use appeared to strongly related to seston and consumer FA and this effect was only strong in rivermouth and nearshore lake sites. River seston and consumer FA composition was highly variable, but that variation does not appear to be driven by the watershed land cover characteristics investigated here. Whether the spatial variation in FA content at the base of these food webs significantly influences the production of economically important species higher in the food web should be a focus of future research.
食物资源的空间变化强烈影响着水生消费者生态的许多方面。尽管人们对食物资源许多方面的大规模控制变化已有充分了解，但其他方面却很少受到研究。在这里，我们研究了美国密歇根湖的溪流系统内（即生境之间）和溪流系统之间的悬浮物和初级消费者的脂肪酸（FA）组成的变化。食物的 FA 组成很重要，因为所有后生动物都需要某些 FA 来正常生长和发育，而这些 FA 不能从头合成，包括许多多不饱和脂肪酸（PUFA）。在这里，我们在密歇根湖的 11 条支流中采样了三种生境类型（河流、河口和近岸区），以评估悬浮物中的 FA 量和悬浮物中的初级消费者。我们假设，食物网基础的 FA 在系统间和生境间的变化将与藻类的产生有关，而藻类的产生又受到三种土地覆盖特征的影响：1）农业和城市用地的综合（指示人为养分输入，为藻类的产生提供燃料），2）地表水的比例（指示允许藻类生产者积累的水停留时间）和 3）河岸森林缓冲区的范围（指示减少藻类产生的溪流遮荫）。在这三个土地覆盖特征中，只有密集的土地利用似乎与悬浮物和消费者 FA 密切相关，而且这种影响仅在河口和近岸湖地区强烈。河流悬浮物和消费者 FA 组成高度可变，但这种变化似乎不是由这里调查的流域土地覆盖特征驱动的。这些食物网基础的 FA 含量的空间变化是否会显著影响食物网中更重要的经济物种的生产，应该是未来研究的重点。
