Zooplankton Abundance and Biomass Retrospective

Zooplankton abundance and biomass were measured during spring and late summer on the inner shelf of the southeastern Bering Sea in years of climate extremes. Samples were taken during late spring and late summer of three years: 1997, a year of moderate spring ice cover and unusually warm, calm summer conditions; 1998, a year of warm, but stormy summer conditions with very little spring ice cover; and 1999, a year of extensive spring ice cover, cold spring conditions and storms during spring and summer. Mean water column temperature was significantly lower during June 1999 than June 1998 and 1997. Copepod abundance and biomass during June were correlated with mean water column temperature and mean temperature below the thermocline. Mean calanoid abundance during June 1999 was 8 - 52 % of the mean abundance during 1998 and 1997. Significantly lower abundances during June 1999 were observed for Calanus marshallae, Acartia spp., Pseudocalanus spp. and calanoid nauplii. Significant interannual differences in mean water column temperature and calanoid abundance during late summer (late July-early September) were not detected. The Hirst-Lampitt equations were used to estimate the mean daily copepod production during the warm and cold years.本研究于极端气候年份的春季与夏末期间，在白令海东南部陆架内侧海域开展浮游动物丰度与生物量的测定工作。采样工作分别于三年的晚春与夏末开展：1997年春季海冰覆盖程度中等，夏季异常温暖且海况平静；1998年春季海冰覆盖极少，夏季温暖但多风暴；1999年春季海冰覆盖范围广泛，春季与夏季海况寒冷且多风暴。1999年6月的水柱平均温度显著低于1998年与1997年同期。6月桡足类（Copepod）的丰度与生物量与水柱平均温度及温跃层下方平均温度显著相关。1999年6月哲水蚤目（Calanoida）平均丰度仅为1998年与1997年同期平均丰度的8%至52%。1999年6月，马绍尔纺锤水蚤（Calanus marshallae）、歪水蚤属（Acartia spp.）、拟哲水蚤属（Pseudocalanus spp.）及哲水蚤无节幼体的丰度均显著降低。晚夏季（7月下旬至9月初）的水柱平均温度与哲水蚤目丰度未检测到显著的年际差异。本研究采用赫斯特-兰皮特方程（Hirst-Lampitt equations）估算了暖年与冷年的桡足类日均生产量。