Data from: Bay-scale patterns in the distribution, aggregation and spatial variability of larvae of benthic invertebrates

This study aimed to investigate mechanisms of pattern formation in the
larval distributions of benthic invertebrates by relating the spatial and
temporal variability in the larval distributions to that in physical and
biological variables, such as temperature, salinity, fluorescence and
current velocity. Larvae were sampled at 11 sites on 7-8, and 11-12 Aug
2008 and at 16 sites on Aug 2-4, 2009, with a 200-μm plankton ring net
(0.75-m diameter) towed for 5 min at 3 m and 12 m depth (in and below the
mixed layer, respectively) in St. George’s Bay, Nova Scotia, Canada. In
2009, density, temperature, salinity, and fluorescence were measured with
a CTD cast at each station, and currents were quantified with an ADCP
moored at 5 locations throughout the bay. In 2008, we only measured
temperature. Gastropod, bivalve and, to a lesser extent, bryozoan larvae
had very similar spatial distributions, but the distribution of decapod
larvae followed a different pattern. These findings suggest that taxonomic
groups that have functionally (i.e. swimming ability) similar larvae (e.g.
bivalves and gastropods) also show similar dispersion properties
(distribution and spatial variability), while the opposite is true for
groups with functionally dissimilar larvae (e.g. bivalves and decapods).
We also found that larval distributions of all taxa were significantly
aggregated, although the degree of aggregation varied among taxa. Using an
aggregation-diffusion model, we demonstrated that horizontal swimming was
not an effective means of forming aggregations even at modest levels of
diffusion. We hypothesize that patterns in observed horizontal
distribution at this scale (< 40 km) are determined during the
larval phase, and that the primary mechanism for pattern formation is
larval interaction with physical oceanographic structures (e.g.
stratification and tidal currents).

本研究旨在探究底栖无脊椎动物幼体分布模式的形成机制，通过将幼体分布的时空变异性与温度、盐度、荧光及流速等物理和生物变量的变异性相关联。

2008年8月7-8日及11-12日，研究人员在加拿大新斯科舍省圣乔治湾的11个站点采集幼体；2009年8月2-4日，则在该区域16个站点采集幼体。采样采用直径0.75米的200微米浮游生物环网（plankton ring net），分别在3米（混合层内,mixed layer）和12米（混合层以下,mixed layer）深度拖网5分钟。

2009年，每个站点通过CTD（电导率-温度-深度剖面仪,CTD）测量密度、温度、盐度和荧光；全海湾5个位置布放的ADCP（声学多普勒流速剖面仪,ADCP）用于量化海流。2008年仅测量温度。

腹足类（gastropod）、双壳类（bivalve）以及（程度较轻的）苔藓虫（bryozoan）幼体的空间分布极为相似，但十足目（decapod）幼体的分布模式不同。

这些发现表明，幼体功能（即游泳能力）相似的分类群（taxonomic group）（如双壳类和腹足类）也表现出相似的扩散特性（dispersion property）（分布和空间变异性）；而幼体功能不同的类群（如双壳类和十足目）则呈现相反趋势。

我们还发现，所有类群的幼体分布均显著聚集（aggregation），尽管聚集程度因类群而异。

通过聚集-扩散模型（aggregation-diffusion model），我们证明即使在中等扩散水平下，水平游泳也不是形成聚集的有效方式。

我们假设，在此尺度（<40 km）下观测到的水平分布模式由幼体阶段决定，且模式形成的主要机制是幼体与物理海洋结构（physical oceanographic structure）（如分层（stratification）和潮流（tidal current））的相互作用。