Articles | Volume 14, issue 7
https://doi.org/10.5194/bg-14-1903-2017
https://doi.org/10.5194/bg-14-1903-2017
Research article
 | 
07 Apr 2017
Research article |  | 07 Apr 2017

The effects of different environmental factors on the biochemical composition of particulate organic matter in Gwangyang Bay, South Korea

Jang Han Lee, Dabin Lee, Jae Joong Kang, Hui Tae Joo, Jae Hyung Lee, Ho Won Lee, So Hyun Ahn, Chang Keun Kang, and Sang Heon Lee

Abstract. The biochemical composition of particulate organic matter (POM) produced through phytoplankton photosynthesis is important in determining food quality for planktonic consumers as well as the physiological conditions of phytoplankton. Major environmental factors controlling the biochemical composition were seasonally investigated in Gwangyang Bay, South Korea, which has only natural conditions (e.g., no artificial dams). Water samples for the biochemical compositions were obtained from three different light depths (100, 30, and 1 %) mainly at three sites in Gwangyang Bay from April 2012 to April 2013. Different biochemical classes (carbohydrates, CHO; proteins, PRT; and lipids, LIP) were extracted, and then the concentrations were determined by the optical density measured with a spectrophotometer. The highest and lowest PRT compositions among the three biochemical classes were found in April 2012 (58.0 %) and August 2012 (21.2 %), whereas the highest and lowest LIP compositions were found in August 2012 (49.0 %) and April 2012 (24.8 %), respectively. The CHO composition was recorded as high in January 2013 and remained above 25 % during the study period. The calorific contents of the food material (FM) ranged from 1.0 to 6.1 Kcal m−3 (annual average ± SD  =  2.8 ± 1.1 Kcal m−3). Based on a Pearson's correlation coefficient analysis, a major governing factor in the biochemical composition of POM was dissolved inorganic nitrogen loading from the river input in Gwangyang Bay. In conclusion, a relatively larger amount of FM and the higher calorific contents of POM found in this study compared to other regions reflected good nutritive conditions for sustaining productive shellfish and fish populations in Gwangyang Bay. Continuous observations are needed to monitor the marine ecosystem response to potential environmental perturbations in Gwangyang Bay.

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Short summary
Based on the seasonal biochemical compositions in this study, the calorific contents of the food material were 1.0–6.1 Kcal m−3. We found that a major governing factor in the biochemical composition of POM was dissolved inorganic nitrogen loading from river input. The relatively larger amount of food material and the higher calorific content of the POM found in this study reflected good nutritive conditions for sustaining productive shellfish and fish populations in Gwangyang Bay, South Korea.
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