| Summary: | The NE Pacific has one of the longest open ocean time series, primarily as a result of the weathership station at Station P from the 1950s to 1981. In the 1960s and 70s, the observation that nitrate was never depleted by phytoplankton in summer, was explained by extensive zooplankton grazing and cloudy weather (light limitation). This turned out to be the wrong explanation because certain critical measurements were not available. In the mid 1980s, the late John Martin made the first relatively uncontaminated measurements of iron and revealed that iron concentrations were very low and limited phytoplankton growth. This was a revolutionary discovery, because up to that point, we thought that oceanic productivity was mainly limited by macronutrients such as nitrate and phosphate and possibly silicate and that micronutrients or trace elements were less important Now there are at least three large areas of the world's oceans where nitrate is never depleted and chlorophyll (phytoplankton biomass) is low because of iron limitation. The N Pacific, equatorial Pacific and the Southern Ocean are referred to High Nitrate, Low Chlorophyll (HNLC) regions. Dust from the Gobi Desert in China is an episodic source of iron that reaches the NE Pacific. An episodic iron input was simulated in the recent mesoscale iron enrichment experiment at Stn P and some results will be presented. Through a series of large international/Canadian programs such as JGOFS and SOLAS, our understanding of how iron limitation influences the ecosystem dynamics of the NE Pacific is evolving.
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