Monthly densities of the snail Cerithideopsis (Cerithidea) californica at Carpinteria Salt Marsh, California USA, February 2012 to January 2014

Each month (except March 2012), we collected detailed data on the density, size distribution, and infection status of intertidal snails from ten fixed sites as part of a broader effort to understand food webs in California Estuaries. The study site was Carpinteria Salt Marsh Reserve, California USA, (University of California Natural Reserve System), which comprises 9 Ha tidal channels, 2 Ha salt flats, 17 Ha upland habitat, 6 Ha tidal pans, 52 Ha vegetated marsh, 2 Ha tidal flats. Each site was a fixed location in channel or flat habitat, with a diameter approximately 50m in size, centered at the site location marker used in Kuris et al. (2008). At each site/month, we collected, measured, sexed, and dissected ~58 snails. We collected and measured an additional ~42 snails for size-frequency distributions (7,793 snails total). Transects were placed randomly at flats sites. For channel sites, transects were placed randomly on the channel bank with the highest snail density. Each transect started 20 cm within the vegetated margin, and extended downslope to the deepest part of the channel or interior of the pan or to a maximum length of 10 m. For every 20 cm decrease in elevation, we established a new transect segment, or quadrat. Specifically, we systematically placed transects at intervals stratified within targeted habitat types: channels, pans, or marsh (or planar habitat that was mixed marsh and pan). At a quarter of the quadrats, we also estimated snail size-frequency distributions. Because we recorded the location of each quadrat, these data can be used to map the distribution of snails throughout this estuary.

为系统解析加利福尼亚河口的食物网结构，我们于每月（2012年3月除外）从10个固定样点采集潮间带螺类（intertidal snails）的密度、体型分布及感染状态的详细数据。本研究样地为美国加利福尼亚州卡皮特里亚盐沼保护区（Carpinteria Salt Marsh Reserve），隶属于加州大学自然保护区系统（University of California Natural Reserve System），该保护区包含9公顷潮汐水道、2公顷盐坪、17公顷高地生境、6公顷潮汐浅洼、52公顷有植被覆盖的沼地以及2公顷潮间带滩涂。每个样点均为潮汐水道或滩涂生境内的固定区域，直径约50米，以Kuris等（2008）文中所用的样点定位标记为中心。在每个样点的每次采样中，我们完成了约58只螺类的采集、测量、性别鉴定与解剖操作；此外还额外采集并测量了约42只螺类以构建体型频率分布，本研究累计采集螺类共计7793只。滩涂样点的样带（transects）采用随机布设方式；对于潮汐水道样点，样带则随机设置在螺类密度最高的水道岸坡上。每条样带均从植被带边缘向内20厘米处起始，沿下坡方向延伸至水道最深处、潮汐浅洼内部，或最长不超过10米的位置。每当海拔下降20厘米，我们即布设一个新的样带段或样方（quadrats）。具体而言，我们依据目标生境类型（潮汐水道、潮汐浅洼、沼地，或兼具沼地与浅洼的平面生境）进行分层，按固定间隔系统布设样带。在四分之一的样方中，我们还估算了螺类的体型频率分布。由于我们记录了每个样方的空间位置，上述数据可用于绘制该河口内螺类的完整空间分布图谱。