Fertilization of the Northwest Pacific Ocean by East Asia Air Pollutants

Abstract

Haze particles as a key air pollutant contain high level of toxins, which were hypothesized to inhibit phytoplankton growth when deposited to the ocean, and thus indirectly affect the climate. However, field observations have yet to provide conclusive evidence to confirm this hypothesis. Onboard microcosm experiments in the Northwest Pacific Ocean (NWPO) show that haze particles collected at the East Asia continent had an inhibition impact on phytoplankton growth only when at very high particle loading (2 mg/L). In contrast, haze particles at low and medium loadings (0.03–0.6 mg/L) stimulated phytoplankton growth and shifted phytoplankton size structure toward larger cells, primarily due to the supply of inorganic nitrogen nutrients from the particles. Model simulations showed that haze particle loading in NWPO surface seawater was usually more than an order of magnitude lower than 2 mg/L. This indicates that haze particles are unlikely to cause harm but to stimulate phytoplankton growth in the nitrogen‐limited NWPO. Ocean biogeochemical modeling further shows that deposited nitrogen significantly enhanced surface ocean chlorophyll a concentration in the winter and spring of 2014. Overall, these results demonstrate that haze particles stimulate rather than inhibit primary production in the NWPO.

Impact of Changes to the Atmospheric Soluble Iron Deposition Flux on Ocean Biogeochemical Cycles in the Anthropocene

“…As the phytoplankton toxicity threshold for copper is tempered by the presence of other metals (e.g., iron and manganese) future studies would need to include a suite of metal aerosols (Mahowald et al, ) to diagnose the overall impact. However, copper concentrations may need to be unrealistically high to reduce marine productivity (Zhang et al, ).…”

“…Understanding how human activity modifies the atmospheric fluxes of metals to the oceans is important due to the impact of the deposited metals on the growth and development of the phytoplankton community (Boyd et al, ; Jickells et al, ; Mahowald et al, ; Moore, Mills, et al, ) and thus their potential to enhance carbon sinks. While deposition of metals such as iron, zinc, and manganese are beneficial for phytoplankton (Morel & Price, ; Wyatt et al, ), other metals such as copper are toxic at high concentrations (Jordi et al, ; Paytan et al, ; Zhang et al, ). Due to iron's critical role as a micronutrient required by ocean biota for primary productivity (Martin, ; Martin et al, ; Tagliabue et al, ), here we focus on how human activity alters the magnitude of atmospheric soluble iron deposition to the oceans and diagnose the resulting impact on ocean biogeochemistry.…”

Iron solubility in fine particles associated with secondary acidic aerosols in east China

“…Although the contribution of anthropogenic sources to Fe T is small compared with that from natural sources, their contribution to %Fe S is much higher (0.06-81%) (Schroth et al, 2009;Oakes et al, 2012). The anthropogenic Fe emissions are strongly associated with anthropogenic combustion sources in regions afflicted with elevated air pollution levels (Guieu et al, 2005;Lough et al, 2005;Sedwick et al, 2007;Zhang et al, 2019). Therefore, it is important to understand %Fe S in continental air polluted by various anthropogenic sources.…”

Anthropogenic Asian aerosols provide Fe to the North Pacific Ocean

“…A role for anthropogenic Fe also bears upon an understanding of macronutrient cycling in the North Pacific Ocean. Industrial emissions have been shown to be a significant source of fixed N to the North Pacific Ocean (40)(41)(42)(43), potentially fueling productivity in the oligotrophic gyre and the Northwest Pacific Ocean. The increase in N availability caused by the deposition of pollutant N in conjunction with the deposition of aerosol Fe from anthropogenic sources could stimulate phytoplankton growth in the subtropics, and potentially switch parts of the subtropical Pacific Ocean from being N-limited to P-limited.…”