Seasonal fluctuations in deep-sea sediment community oxygen consumption: central and eastern North Pacific

Historically the deep sea was viewed as a homogeneous environment in time and space characterized by high hydrostatic pressure, low temperature and low food supply^1,2. The highly diverse but low-density communities of organisms^3,4 occupying this environment were dependent on a slow, constant rain of small participate organic matter from the overlying surface water for food. This material slowly settled through thousands of metres of the water column, dampening any pulses in primary production at the surface. The rate at which this `constant' food source was used was found to be slow^5-8. However, there was early evidence^9-12, with much recent support^13-17, that some deep-sea animals exhibited seasonal reproduction. In addition, the flux of small particulate organic matter to the deep-sea floor has been shown to be seasonal and in phase with rates of surface primary productivity^18-20. We report here the first evidence of seasonality in biological rates in the deep sea: in situ rates of sediment community oxygen consumption at two abyssal stations in the central and eastern North Pacific are highest in early summer, decreasing to the lowest rates in late autumn and winter.