麻豆淫院

Air pollution has become an ever-pressing issue since the Industrial Revolution began in the mid-18th century. Progressive urbanization, industrialization and agricultural development over more recent decades have been linked to a plethora of consequences for the environment and health of humans and wildlife.

New research, in Frontiers in Marine Science, has considered how air pollution in South Asia has impacted the neighboring marine environment. In particular, a focus on how nitrogen released from fossil fuel combustion and agricultural practices affects the northern Indian Ocean.

Researcher Manon Malsang of France's Sorbonne Universit茅 and colleagues analyzed the ocean's primary productivity in response to enhanced anthropogenic nitrogen deposition. Primary productivity refers to the rate at which organisms, such as microscopic phytoplankton, produce organic matter by harnessing energy from light (photosynthesis) or chemicals (chemosynthesis). This forms the foundation of food chains in the ocean and is consumed by secondary producers like zooplankton.

Furthermore, warming of the marine realm due to climate change has increased ocean stratification, where distinct layers occur based on density due to differences in temperature and salinity. Ultimately, this restricts the recycling of nutrients through the water column available for primary and secondary producers.

As such, the researchers examined the balance between anthropogenic nitrogen deposition and ocean warming on productivity via computer modeling (using baseline data from the 1980s and exploring this through a "climate trend" of ocean warming and "nitrogen trend" based on increased pollutant input), as well as evaluating surface chlorophyll via satellite images.

The baseline data showed hotspots of primary phytoplankton and secondary zooplankton productivity, as well as organic carbon export below 100m in zones of nutrient upwelling, such as the western Arabian Sea. However, the lowest productivity and export occurred in the southeastern Arabian Sea and the central Bay of Bengal, where nutrients were limited by a warming ocean, deepening the nitracline (the vertical gradient in the ocean where nitrate concentrations increase with depth). This was further exacerbated under the "climate trend" modeling scenario.

Conversely, they found a small increase (0.6%) in primary and secondary productivity in the northern Indian Ocean in response to a 60% rise in nitrogen deposition. In fact, since 1980, there has been a doubling of anthropogenic nitrogen input from India alone, with additional notable increases along the coasts of Bangladesh and Myanmar.

The researchers note that this is enough of a compensatory fertilizing mechanism to offset a 40-year declining trend of primary productivity, particularly in hotspots near sources of nitrogen deposition, such as the central Arabian Sea and the western Bay of Bengal. Here, the ocean stratification is also less intense, with a deeper mixed layer. Indeed, nitrogen deposition offsets climate change-induced ocean warming impacts on productivity by 70% and 100% in each location, respectively.

Further adding to the complexity are the effects of seasonal monsoons, which can enhance the mixing of ocean layers and, thus, the recycling of nutrients for primary and secondary productivity. This intensifies even more with the deposition of iron from Arabian dust blown into the region. Yet, analysis of chlorophyll abundance from satellite images does not correlate with primary productivity trends and highlights the challenge of interpretations based on ocean color.

Nevertheless, this research highlights the role of atmospheric nitrogen deposits in the ocean having a compensatory effect on the decline in primary productivity linked to ocean warming, however small. Plus, the research doesn't account for dissolved organic nitrogen, nitrogen fixation and riverine input, which could contribute to the ocean's nitrogen budget and enhance the mitigation effect.

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