RUI: Organic Matter Processing by Filter Feeders in Stream Ecosystems

细颗粒有机物质（FPOM）在大多数河流生态系统中主导着宏观消费食物网。然而，溶解的有机物质（DOM），被认为只对微消费者可用，往往是最大的有机物质池。黑蝇的密集聚集，经常发生在湖出口和基岩瀑布上，似乎过滤了进入聚集的FPOM的很大一部分，但这个池的质量在穿过聚集时并不减少；它增加。初步数据表明，进入这些聚集体的FPOM通过黑蝇的摄食和排泄被DOM增加。建议的工作目标是：1)确定DOM和FPOM馈送到流中的FPOM和DOM池的重要性；2)评价其在黑蝇取食中的作用。为了实现这些目标，将通过一系列的上下游比较、稳定同位素和染料示踪实验、滤料去除实验和实验室饲养实验来测量：1)通过滤料聚集体的FPOM，包括颗粒的质量、尺寸分布和叶绿素浓度；2) DOM到FPOM的转换；3) DOM池不同大小组分（分子量）对黑蝇的可用性。在这些密集的群落中发生的相同过程也可能发生在更多样化的溪流群落中；然而，影响将更难检测。因此，虽然这些实验侧重于特殊情况，但它们可能对流有机质动力学具有广泛的适用性。

Hershey Fine particulate organic matter (FPOM) dominates macroconsumer food webs in most stream ecosystems. However, dissolved organic matter (DOM), thought to be available only to microconsumers, is often the largest pool of organic matter present. Dense aggregations of black flies, which often occur at lake outlets an on bedrock cascades, appear to filter a very large portion of the FPOM entering the aggregation, but mass of this pool does not decrease as it passes across the aggregations; it increases. Preliminary data suggest that the FPOM entering these aggregations is augmented by DOM, via black fly feeding and egestion. The objectives of the proposed work are: 1) to determine the importance of DOM and FPOM feeding to FPOM and DOM pools in streams; and 2) to evaluate the role in black fly feeding. To meet these objectives, a series of upstream and downstream comparisons, stable isotope and dye tracer experiments, filter-feeder removal experiments, and laboratory feeding experiments will be used to measure: 1) FPOM passing through a filter-feeder aggregation, including mass, size distribution of particles, and chlorophyll concentration; 2) transformation of DOM to FPOM; and 3) availability of different size fractions (molecular weights) of the DOM pool to black flies. The same processes that occur in these dense aggregations could also occur in more diverse stream communities; however, effects would be harder to detect. Thus, although these experiments focus on special cases, they may have broad applicability to stream organic matter dynamics.