Toxicity of atmospheric aerosols on marine phytoplankton

Abstract

Atmospheric aerosol deposition is an important source of nutrients and trace metals to the open ocean that can enhance ocean productivity and carbon sequestration and thus influence atmospheric carbon dioxide concentrations and climate. Using aerosol samples from different back trajectories in incubation experiments with natural communities, we demonstrate that the response of phytoplankton growth to aerosol additions depends on specific components in aerosols and differs across phytoplankton species. Aerosol additions enhanced growth by releasing nitrogen and phosphorus, but not all aerosols stimulated growth. Toxic effects were observed with some aerosols, where the toxicity affected picoeukaryotes and Synechococcus but not Prochlorococcus. We suggest that the toxicity could be due to high copper concentrations in these aerosols and support this by laboratory copper toxicity tests preformed with Synechococcus cultures. However, it is possible that other elements present in the aerosols or unknown synergistic effects between these elements could have also contributed to the toxic effect. Anthropogenic emissions are increasing atmospheric copper deposition sharply, and based on coupled atmosphere-ocean calculations, we show that this deposition can potentially alter patterns of marine primary production and community structure in high aerosol, low chlorophyll areas, particularly in the Bay of Bengal and downwind of South and East Asia.L aboratory experiments, field observations, and numerical simulations all link atmospheric deposition events to increases in ocean chlorophyll concentrations and phytoplankton biomass (1-3), suggesting that atmospheric deposition of nutrients and trace metals can stimulate phytoplankton growth. Indeed, enrichment experiments with iron (a required nutrient scarce in seawater and enriched in dust) show that in highnutrient low-chlorophyll areas (representing 20-40% of the ocean), iron addition can increase primary production, export production, and carbon sequestration (4-7). In areas where phosphorus and nitrogen concentrations are low, aerosol deposition can supply both iron and phosphate, nutrients that stimulate nitrogen fixation (8-9). It has been suggested that increases in dust deposition during glacial periods have been responsible for lowering atmospheric carbon dioxide concentrations thus impacting climate (10-12).Aerosol particles consist of many natural and anthropogenic components, including mineral dust, soot, organic molecules, sea salt crystals, spores, bacteria, and other microscopic particles (13), and can supply many elements and compounds to seawater (14-16). Little research has been done to elucidate what specific component(s) in aerosols affect phytoplankton at the level of community or individual species or how certain taxa within the community respond to distinct aerosol deposition events and to aerosols of different composition. Results and DiscussionTo assess the short-term response of phytoplankton communities to aerosol deposition, we performed bioassay e...

Copper aerosols inhibit phytoplankton growth in the Mediterranean Sea

“…Merged satellite chlorophyll (Chl) data were used as an indicator of total phytoplankton biomass (18). Daily Chl variations (ΔChl) were calculated during Cu pulses, as the toxic response of phytoplankton to Cu was previously shown to be evident already on the first day of a Cu event (9,10,19). As seen in Fig.…”

“…In fact, bioassay experiments have demonstrated that the addition of aerosols containing high copper concentrations to ocean water samples can have detrimental effects on phytoplankton communities (10). Nonetheless, the bulk oceanic response to Cu aerosol deposition has only been assessed based on a coupled atmosphere-ocean model (10). This lack of direct evidence is in itself a cause for major concern because human activities have increased the amount of atmospheric aerosols and specifically those carrying Cu and other metals (11,12).…”

“…For example, Cu is highly toxic even at relatively low concentrations (9), and its toxic effects can be exerted following its release from aerosol particles. In fact, bioassay experiments have demonstrated that the addition of aerosols containing high copper concentrations to ocean water samples can have detrimental effects on phytoplankton communities (10). Nonetheless, the bulk oceanic response to Cu aerosol deposition has only been assessed based on a coupled atmosphere-ocean model (10).…”

Evolving research directions in Surface Ocean - Lower Atmosphere (SOLAS) science

“…[122] Conversely, ship fuels contain high levels of heavy metals, many of which are toxic, which may influence biodiversity and productivity of marine ecosystems. [92] A full assessment of the effect of ship emissions on ocean biogeochemistry, including the effect of nutrient v. toxin input, has yet to be undertaken but coordination with the Atmospheric Nutrient and Oceanderived Aerosols research strategies (see previous two sections) will assist in the development of this emerging SOLAS research theme.…”

“…Cu and Pb). [90][91][92] Consequently deposition represents an important source of new nutrients and particles for large regions of the open ocean. [90,91] This deposition is being perturbed directly and indirectly by anthropogenic activities; for example, atmospheric pollution has greatly increased the deposition of nitrogen, [7] and the magnitude of dust deposition to the oceans has been shown to be climate dependent.…”