Collaborative Research: Effects of Flow on Feeding Behavior and Growth Rate of Interface-Feeding Benthos: Size Dependent Changes and Recruitment Bottlenecks

Hentschel 0000951成年后以沉积或悬浮颗粒为食的物种的幼体面临着从丰富的幼体食物(浮游生物或蛋黄)到贫乏的成体食物(与沉积物相关的有机物)的转变。较小的体型进一步施加了消化和觅食的限制，这可能会限制幼鱼专门吃沉积物或底栖边界层中相对不稳定的食物(例如底栖硅藻、植物碎屑、富含有机物质的絮状物、动物猎物)。最近的研究揭示了几种界面摄食的多毛类的食物大小相关的变化。尽管改变饮食的证据是明确的，但蠕虫在幼虫成长为成年后摄食活动发生变化的方式仍未解决。对于在沉积物-水界面觅食的物种，已知根据水动力条件在沉积物摄食和悬浮摄食之间进行兼性切换，幼体阶段更频繁的悬浮摄食可能是小虫提高其食物质量和生长速度的一种手段。这种摄食行为和生态位大小相关的变化可能会对种群和群落动态产生戏剧性的影响。如果悬浮摄食是幼体克服特定大小食物限制的主要手段，则栖息地的水动力特性将强烈影响幼体生长和招募到生殖成体阶段的速度。虽然流对扩散和幼虫定居的影响已经引起了相当大的关注，但与流有关的对幼鱼生长的影响是一种相对未被研究的生物-流相互作用，可能会像流对扩散和定居的影响一样显著地影响底栖种群和群落的结构和动态。研究集中在4种蜘蛛多毛类上，因为1)尽管蜘蛛是最好的界面取食者，但与流量有关的取食行为和生长速度尚未被测量到；2)现有数据表明，几种蜘蛛依赖大小的食物变化和与食物有关的补充瓶颈；螺旋藻是许多底栖动物群落中丰富的成员，在食物链和地球化学过程中起着核心作用。为了验证幼体比成体更频繁地悬浮摄食的假设，将在实验室水槽中观察个体在各种流动和食物条件下的大小依赖的摄食行为。为了量化取食行为随大小变化的营养后果，将在四个相同的、反向旋转的环形水槽中测量不同大小类别的生长率，这些水槽将被设置为流体力学上不同的中微体。为了揭示与种内个体大小变化有关的喂食机制和行为的物理约束，将在小体积水槽中量化颗粒捕获的速率和效率。为了更好地将实验室对个体的实验结果外推到密集的野外种群，将测试密度对幼虫生长速度和颗粒摄取的影响。深入了解觅食行为和机制、生长速度、颗粒特征和流动速度之间的联系，将提供对栖息地水动力状况与蜘蛛种群成年期的生长和招募速度之间关系的多方面和机械性的理解。在教育和人力资源方面，合作努力结合并拓宽了博士后助理、初级教员和终身教员导师的专业知识。此外，整合涉及生态、物理和生化参数的行为观察和操控实验，提供了一种理想的形式，向本科生介绍一所主要研究型大学和一所小型文理学院的跨学科研究。

Hentschel 0000951Juveniles of species that, as adults, feed on deposited or suspended particles face a transition from a rich larval diet (plankton or yolk) to a poor adult one (sediment-associated organics). Small body size further imposes digestive and foraging limitations that probably constrain juveniles to specialize on relatively labile foods in the sediment or benthic boundary layer (e.g. benthic diatoms, phytodetritus, organic-rich flocs, animal prey). Recent research has revealed size-dependent changes in the diets of several interface-feeding polychaetes. Although evidence of changing diets is clear, the ways in which worms' feeding activities shift as juveniles grow to adults is unresolved. For species foraging at the sediment-water interface and known to facultatively switch between deposit feeding and suspension feeding in response to hydrodynamic conditions, more frequent suspension feeding during the juvenile stage is a likely means by which small worms might increase the quality of their diet and their rate of growth. Such a size-dependent shift in feeding behavior and niche could have dramatic implications for population and community dynamics. If suspension feeding were the dominant means by which juveniles overcome size-specific food limitation, a habitat's hydrodynamic characteristics would strongly affect rates of juvenile growth and recruitment to the reproductive, adult stage. While flow's influence on dispersal and larval settlement has received considerable attention, flow-related effects on juvenile growth are a relatively unstudied organism-flow interaction that might impact the structure and dynamics of benthic populations and communities as significantly as flow's effects on dispersal and settlement.The study focuses on four species of spionid polychaetes because 1) although spionids are the best studied interface feeders, size-dependent feeding behavior and growth rates have not been measured in relation to flow; 2) existing data point to size-dependent diet changes and food-related recruitment bottlenecks in several spionids; and 3) spionids are abundant members of many benthic communities, playing central roles in food webs and geochemical processes. To test the hypothesis that juveniles tend to suspension feed more often than adults, the size-dependent feeding behavior of individuals will be observed in a laboratory flume under a variety of flow and food conditions. To quantify the nutritional consequences of size-dependent shifts in feeding behavior, growth rates of different size classes will be measured under selected flow and food treatments in four identical, counter-rotating annular flumes that will be set up as hydrodynamically distinct mesocosms. To reveal physical constraints on feeding mechanics and behavior in relation to intraspecific body-size variations, rates and efficiencies of particle capture will be quantified in a small-volume flume. To better extrapolate results from lab experiments on individuals to dense field populations, density--dependent effects on juvenile growth rate and particle ingestion will be tested. Insight into linkages among feeding behaviors and mechanics, growth rates, particle characteristics, and flow speed will provide a multifaceted and mechanistic understanding of the relationships between a habitat's hydrodynamic regime and the rates of growth and recruitment to adulthood in spionid populations.In terms of educational and human resources, the collaborative effort combines and broadens the expertise of a postdoctoral associate, a junior faculty member, and a tenured faculty mentor. In addition, integrating behavioral observations and manipulative experiments involving ecological, physical and biochemical parameters provides an ideal format to introduce undergraduates to interdisciplinary research at both a major research university and a small liberal-arts college.