Flume Studies of the Effects of Reproductive Mode, Larval Concentration and Hydrodynamics on Larval Settlement Rate of Infaunal Invertebrates

本实验室水槽研究的目的是量化不同繁殖模式的底栖无脊椎动物（即浮游营养型或卵泡营养型幼虫）和分类亲和力（多毛类和双壳类）的幼虫可用性的沉降率。幼虫可得性，这里定义为幼虫向床的供应，是幼虫浓度和速度项的乘积。因此，我们专门设计了实验来测试这两个因素对沉降率的相对影响。将测试三个假设。Hl：沉降率随繁殖方式的变化而变化；较低的沉降率和较高的沉降变异性与浮游营养化的幼虫相比。H2：沉降率随着浮游生物幼虫浓度的增加而增加，直到它达到一个渐近值，此时床是饱和的。H3：幼虫到床的通量可以描述为一个涡流扩散过程，其中关键的水动力参数是边界剪切速度。在验证这些假设的过程中，本研究还将确定(1)水流中幼虫的体积浓度与幼虫到床的流量之间的关系，(2)幼虫沉降是否与幼虫可得性成正比，以及(3)沉降概率（即幼虫沉积后留在床上的概率）。本研究的长期目标是根据幼虫可得性和流量数据预测田间沉降率，因此将进行实验，以便建立一个通用的定量表达式来预测从幼虫通量到河床的沉降。

The objective of this laboratory flume study is to quantify settlement rate as a function of larval availability for species of benthic invertebrates that vary in reproductive mode (i.e., with planktotrophic or lecithotrophic larvae) and taxonomic affinity (polychaetes and bivalves). Larval availability, here defined as the supply of larvae to the bed, is a product of a larval concentration and a velocity term. Thus, experiments are designed specifically to test the relative influence of these two factors on settlement rate. Three hypotheses will be tested. Hl: Settlement rate varies as a function of reproductive mode; lower settlement rates and higher settlement variability are associated with planktotrophic as compared with lecithotrophic larvae. H2: Settlement rate increases with increasing planktonic larval concentration until it reaches an asymptotic value, at which point the bed is saturated. H3: Larval flux to the bed can be described as an eddy diffusion process, where the key hydrodynamic parameter is the boundary shear velocity. In the course of testing these hypotheses, this study will also determine (1) the relationship between bulk concentration of larvae in the flow and flux of larvae to the bed, (2) if larval settlement is directly proportional to larval availability, and (3) the probability of settlement (i.e., of a larva remaining on the bed once deposited). A long term goal of this research is the prediction of settlement rate in the field from data on larval availability and flow, and thus experiments will be conducted so that a general, quantitative expression can be developed to predict settlement from larval flux to the bed.