Title:

Influence of temperature on organic matter consumption and nutrient regeneration by microbial respiration in the Gulf of Maine

Marine microbes are vital to oceanic ecosystems, recycling organic matter to provide essential nutrients to organisms while helping shape global climate through their paramount role in Earth’s biogeochemical cycles. Temperature is known to influence many metabolic rates however, this sensitivity of microbial metabolic rates for dissolved organic matter (DOM) and particulate organic matter (POM) respiration is unknown in the ocean. Temperature controlled incubations of DOM and POM consumption and nutrient regeneration by microbes collected from the Gulf of Maine were conducted for a period of 8 days with nutrient regeneration rates and quantities measured. Microbial respiration favored POM at a higher temperature resulting in a faster rate and a larger quantity of consumption over in situ temperatures and DOM substrates. In addition, a faster rate and a larger quantity of inorganic bioavailable nutrients were produced from the POM higher temperature incubation. POM is larger in size and thought to be more important in the recycling loop in the euphotic zone compared to DOM, which may have other factors controlling its degradation besides temperature. Increased remineralization of POM in the water column with increasing ocean temperatures will reduce the amount of energy sinking to the benthos, potentially reducing the overall productivity of benthic ecosystems. Since microbial respiration of organic matter is ubiquitous in the marine environment, further understanding the impact of increasing temperatures on the recycling of organic matter locally can be applied to the entire ocean as climate continues to change.

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