Passage:
For decades, paleoceanographers attributed the pronounced decrease in atmospheric carbon dioxide during glacial maxima primarily to enhanced iron fertilization of the Southern Ocean. According to this traditional framework, wind-borne dust delivered abundant iron to high-nutrient, low-chlorophyll marine zones, dramatically stimulating phytoplankton growth and drawing atmospheric carbon down into the deep ocean. However, recent sediment core analyses from sub-Antarctic basins reveal a critical structural limitation in this single-nutrient mechanism. While iron influx indeed stimulated transient diatom blooms, long-term carbon sequestration was fundamentally constrained by the concurrent exhaustion of dissolved silicic acid, which is essential for diatom frustule synthesis. When silicic acid levels plummeted, non-silicified phytoplankton species replaced diatoms; these alternative taxa were far less efficient at exporting organic carbon past the thermocline due to their lower sinking velocity and higher remineralization rates in shallow waters. Consequently, rather than validating the iron-fertilization model as a sufficient standalone explanation for glacial carbon drawdown, these empirical findings demonstrate that sustained oceanic carbon storage depended on a delicate biogeochemical synergy between micronutrient supply and lower-latitude nutrient upwelling. Ultimately, the researchers contend that climate models isolating iron dust deposition as the sole driver of glacial-interglacial atmospheric fluctuations significantly overstate its efficacy while overlooking the structural dependencies of marine food webs.
Based on the passage above, determine whether the following statement correctly identifies the primary purpose of the passage:
The primary purpose of the passage is to argue that iron fertilization was entirely ineffective in increasing biological productivity during glacial maxima.
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