Anthropogenic nitrate in the North Pacific

For those who remember, if any, the acid deposition presentation (past Friday), I focused on the effects of acid deposition on FRESHWATER ecosystems. I also tried to sneak in the sentence “there is enough literature on the effects on ocean ecosystems to make another presentation”. Thought I’d post this.

The article uses an analysis can separate the human-derived nitrogen from natural nitrogen fixation. The study reveled (*surprise*) oceanic nitrate concentration increased significantly over the last 30 years in surface waters of the North Pacific. The cause (*surprise again*) enhanced deposition of nitrogen from the atmosphere from industrial and agricultural processes.

Oceanic biological activity is limited by nitrate availability so this input of new nitrogen from the atmosphere can increase photosynthesis which leads to an the movement of carbon-rich organic material from ocean surface into the depths (VIDEO on how such a big ocean can be “limiting”). Similar to freshwater ecosystems, nitrogen deposition can alter the base of the marine food web (ultimately changing the structure of the entire ecosystems NO MATTER HOW BIG).

The addition of a limiting nutrient can cause a composition shift as non-dominant species can be dominant due to this nutrient shift. In this case, marine organisms that thrive under the high nitrate and low phosphorus conditions will become more abundant (possibly at the expense of those species that thrive in low nitrate concentrations). Just another example of how the processes we scarcely think of (transportation and agriculture) have PROFOUND effects on EVERY CORNER OF THIS WORLD.

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