Zooplankton abundance for two shelf stations off Galicia (NW Spain) from 1994 to 2006

Zooplankton was sampled by project RADIALES at Vigo (E3VI) and A Coruña (E2CO) between 1994 and 2006. Samples were collected using 50-cm diameter Juday-Bogorov (A Coruña) or 40-cm diameter bongo plankton nets (Vigo) equipped with 200-µm mesh size. Tows were double oblique from surface to near bottom (90 and 70 m in Vigo and A Coruña, respectively). All samples were collected between 10:00 and 14:00 o'clock (local time). Samples were preserved in 2-4% sodium borate-buffered formaldehyde. For the purpose of this study, the original coastal time series were categorized in copepods representative of crustacean zooplankton) and gelatinous plankton (medusae and tunicates). Medusae included Hydrozoans and Scyphozoa, and tunicates included salps, pyrosomes, doliolids, and appendicularia. Plankton identification and counts were performed by Ana Miranda and M. Teresa Álvarez-Ossorio for samples from Vigo and A Coruña, respectively. Different trends were found for gelatinous plankton in the two coastal sites, characterized by increases in either medusae or tunicates. Multiyear periods of relative dominance of gelatinous vs. copepod plankton were evident. In general, copepod periods were observed in positive phases of the main modes of regional climatic variability. Conversely, gelatinous periods occurred during negative climatic phases. However, the low correlations between gelatinous plankton and either climatic, oceanographic, or fishery variables suggest that local factors play a major role in their proliferations.

1994至2006年间，RADIALES项目在西班牙维哥（E3VI）与拉科鲁尼亚（E2CO）两个沿岸站点开展了浮游动物采样工作。采样分别采用50cm直径的朱代-博戈罗夫（Juday-Bogorov）浮游生物网（拉科鲁尼亚站点）与40cm直径的邦戈（bongo）浮游生物网（维哥站点），两类网具均配备200μm网目尺寸。拖网作业均采用从表层至近底的双斜拖曳方式，维哥与拉科鲁尼亚站点的作业水深分别为90米与70米。所有样本均采集于当地时间10:00至14:00时段。样本采用2%~4%硼酸钠缓冲甲醛溶液进行固定保存。为满足本研究需求，原始沿岸时间序列样本被划分为两大类别：代表甲壳类浮游动物的桡足类（copepods），以及胶质浮游动物（包含水母类与被囊类）。其中水母类涵盖水螅虫纲（Hydrozoans）与钵水母纲（Scyphozoa）物种，被囊类则包括樽海鞘、火体虫、纽鳃樽以及尾海鞘（appendicularia）。维哥与拉科鲁尼亚站点的浮游动物鉴定与计数工作，分别由Ana Miranda与M. Teresa Álvarez-Ossorio完成。两个沿岸站点的胶质浮游动物呈现出迥异的变化趋势，分别表现为水母类种群扩张或被囊类种群扩张。胶质浮游动物与桡足类浮游动物交替占据相对优势的多年周期特征十分显著。总体而言，桡足类占据优势的时段对应区域气候变率主要模态的正相位阶段。反之，胶质浮游动物占据优势的时段则对应气候变率的负相位阶段。但胶质浮游动物与气候、海洋学或渔业变量之间均呈现较低相关性，这表明局部环境因子在其种群增殖过程中发挥了主导作用。