Effects of aerobic respiration and nitrification on dissolved inorganic nitrogen and carbon dioxide in human-perturbed eastern Jiaozhou Bay, China

Abstract

Aerobic respiration and nitrification are important processes for dissolved inorganic nitrogen (DIN) composition change and CO₂ production in human-perturbed coastal waters. On-site incubations and field investigations were conducted in the eastern Jiaozhou Bay, a high-urbanization region, from May to August 2014. Results show that aerobic respiration rates reached 15.58μmolO₂L^-1d^-1, and NH₄⁺ and NO₂^- oxidation rates were 0.53 and 0.13μmolNL^-1d^-1, respectively, in the human-perturbed northeastern area. The intense aerobic respiration there contributed to high-concentration NH₄⁺, and meanwhile caused a pH decrease of 0.042units and a pCO₂ increase of 166μatm per day. Moreover, the linear relationship between excess CO₂ and apparent oxygen utilization suggested that the excess CO₂ in the entire eastern Jiaozhou Bay was mainly from the aerobic respiration. This study may help us better understand the role of aerobic respiration in DIN composition and CO₂ sink/source pattern in coastal waters.

Keywords: Aerobic respiration; Carbon dioxide; Dissolved inorganic nitrogen composition; Eastern Jiaozhou Bay; Nitrification.