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Marine Ecology Progress Series

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MEPS 309:55-65 (2006)  -  doi:10.3354/meps309055

Thermal effects on heterotrophic processes in a coastal ecosystem adjacent to a nuclear power plant

Fuh-Kwo Shiah1,2,*, Tsong-Han Wu3, Kuo-Yuan Li3, Shui-Ji Kao2, Yu-Feng Tseng3, Jia-Lu Chung3, Sen Jan4

1Institute of Marine Environmental Chemistry and Ecology, National Taiwan Ocean University, Keelung, Taiwan
2Research Center for Environment Changes, Academia Sinica, NanKang, Taipei, Taiwan
3Institute of Oceanography, National Taiwan University, Taipei, Taiwan
4Institute of Hydrological Sciences, National Central University, Chung-Li, Taiwan
*Email: fkshiah@

ABSTRACT: During the period October 2001 to August 2002, weekly sampling on bacterial respiration (BR, 3 to 22 mg C m–3 d–1) and microplankton community respiration (CR, size fraction <300 µm, 2 to 90 mg C m–3 d–1) was conducted in the inlet and outlet of Taiwan Nuclear Power Plant II (TNP-II). In addition, 3 transect surveys were conducted across the warm plume outside the TNP-II outlet. All measurements except dissolved organic carbon (DOC, 18 to 45 g C m–3) varied seasonally and spatially with temperature. On average, BR constituted 41% of the total CR. The BR/CR ratios were negatively correlated with CR, the first observation of this trend that we are aware of. The positive temperature responses of rate and/or biomass-normalized rate parameters indicated a very low probability of bottom-up (substrate supply) control on the growth of heterotrophic organisms in these systems. The Q10 (i.e. the increase of rate with a temperature increase of 10°C) values for BR, CR, biomass-normalized bacterial respiration (0.07 to 1.31 d–1) and particulate organic carbon–normalized CR (0.04 to 0.52 d–1) ranged from 1.3 to 3.7. Similar Arrhenius expressions of heterotrophic processes in the field surveys and short-term temperature-manipulation experiments showed that, in this high DOC system, most planktoners were eury-thermal and that their respiration increased with temperature up to >35°C. Such a phenomenon might be related to a temperature–substrate interaction.

KEY WORDS: Bacterial production · Community respiration · Bottom-up control · Q10 · Trophic status

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