Increased benthic grazing: An alternative explanation for low phytoplankton biomass in northern San Francisco Bay during the 1976–1977 drought
Increased benthic grazing: An alternative explanation for low phytoplankton biomass in northern San Francisco Bay during the 1976–1977 drought
复制标题
底栖放牧增加：1976-1977 年干旱期间旧金山湾北部浮游植物生物量低的另一种解释
DOI：
10.1016/0272-7714(85)90018-6
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发表时间：
1985
影响因子：
2.8
通讯作者：
F. Nichols
中科院分区：
文献类型：
--
作者：
F. Nichols
在两年的干旱期间，弗朗西斯科湾北方的河水流量极低，其后果包括：（1）盐度逐渐增加，（2）叶绿素浓度异常下降，（3）河口底栖无脊椎动物向上游迁移到海湾的正常咸水区。在1977年夏季，一个浅水监测点的底栖生物总丰度从正常的2000个增加到超过20000个m-2，可能是对盐度增加的反应。1977年期间，从文献中的公式得出的其中一个物种--悬食性双壳海蛤的估计过滤速率范围为1至4 m3 m − 2 day − 1，取决于取样日期的丰度和平均大小。由于该地点的水深不到2米，Myaca可以每天过滤一次水柱中的所有颗粒（包括硅藻）。其他几种移民物种无疑也有助于从近底层水中去除颗粒。因此，底栖动物放牧的增加可能是干旱期间浮游植物生物量极低的原因。这些结果表明，在长期的低流量和盐度增加的河流底栖食物网可能会变得更重要，比浮游生物的食物网在河口的上部。
Among the consequences of extremely low river flow into northern San Francisco Bay during a two-year drought were (1) a gradual increase in salinity, (2) an unusual decline in chlorophyllaconcentration, and (3) the upstream migration of estuarine benthic invertebrates to the normally brackish area of the bay. Total abundance in the benthos at a shallow monitoring site increased from a normal 2000 to greater than 20 000 individuals m−2during the summer of 1977, presumably in response to the increased salinity. Estimated filtration rates derived from equations in the literature for one of the species, the suspended-feeding bivalveMya arenariaranged from 1 to 4 m3m−2day−1during 1977 depending on abundance and mean size on sampling dates. Because water depth at this site is less than 2 m,Myacould have filtered all of the particles (including diatoms) from the water column on the order of once per day. Several other immigrant species undoubtedly contributed to the removal of particles from the near-bottom water as well. Increased benthic grazing, therefore, could have accounted for the anomalously low phytoplankton biomass observed during the drought. These results suggest that during periods of prolonged low river flow and increased salinity benthic food webs could become more important than planktonic food webs in the upper part of the estuary.