Patterns of recruitment of epifaunal species at Portsea, Victoria.

This study investigated the temporal and spatial patterns of recruitment of epifaunal species at Portsea. Recruitment panels were immersed at depths of 1 - 2.2 metres for 10 months (25/10/1975 - 11/9/1976) and 24 months (16/11/1977 - 14/11/1979) and at depths of 3 - 3.8m for 18 months (11/9/1976 - 18/5/1978). Each panel was divided into four quadrats (9 x 9cm) and the number of larvae recruits in each quadrat was recorded every 2 months using a binocular microscope. The replicate number of quadrats sampled every 2 months varied between 1 and 30 replicates. The mean number of larval recruits per quadrat for each period was calculated for each species at each depth. An additional treatment ('complex substratum' treatment) was added to 2 panels for 2-month periods from 13/10/1976 to 12/10/1977 to assess the effects of substratum complexity on the recruitment of epifauna. The complex substratum treatment simulated the physical structure of a barnacle and arborescent bryozoan community. On each panel there was 1 quadrat that was a complex substratum treatment and 1 quadrat that was randomly chosen from the 3 remaining to be analysed as the control. Thus, there were 2 replicate quadrats of each treatment (complex substratum and control) per 2-month period. At the completion of each period all individuals and colonies of each species were counted in each quadrat.Availability and abundance of settling larvae varied seasonally and annually. Rates of recruitment of larvae were greatest during spring, summer and autumn. Polychaetes, barnacles, hydroids, tubicolous amphipods and bryozoans recruited in greater abundance and more consistently throughout each year than did ascidians or sponges. A greater diversity of species settled on the complex substratum treatments and the density of settlement of some species was also higher.

本研究针对波特西（Portsea）海域底表动物（epifaunal species）的幼体招募时空格局展开系统探究。实验设置了附着招募板（recruitment panels），并设置了不同的放置时长与水深梯度：分别在1~2.2米水深处放置10个月（1975年10月25日—1976年9月11日）与24个月（1977年11月16日—1979年11月14日）；在3~3.8米水深处放置18个月（1976年9月11日—1978年5月18日）。每块招募板被划分为4个样方（quadrats），单个样方规格为9×9厘米，每2个月使用双目显微镜记录每个样方内的幼体招募个体数。每2个月采样的样方重复数介于1至30之间。针对每个物种与每个水深梯度，计算各实验时段内单个样方的平均幼体招募数量。1976年10月13日—1977年10月12日期间，额外在2块招募板上开展了为期2个月的“复杂基底处理组”实验，以评估基底复杂度对底表动物幼体招募的影响。该复杂基底处理组模拟了藤壶与树状苔藓虫群落的物理结构特征。每块招募板中设有1个施加复杂基底处理的样方，同时从剩余3个样方中随机选取1个作为对照样方。因此，每2个月的实验周期内，两种处理（复杂基底组与对照组）各设有2个重复样方。每个实验时段结束后，统计每个样方内各物种的所有个体及群体数量。研究结果显示，幼体的可获得性与丰度呈现显著的季节与年度变化特征：幼体招募率在春、夏、秋三季达到峰值。多毛类（polychaetes）、藤壶、水螅虫、管栖端足类与苔藓虫的招募丰度与年度持续性均优于被囊动物与海绵。复杂基底处理组上的定居物种多样性更高，部分物种的定居密度也显著提升。