COS 25-1 - Reduced compounds can be alternative source of organic matter for striped catfish Pangasianodon hypophthalmus via chemoautotrophic bacteria in a reservoir

Monday, August 15, 2022

3:30 PM – 3:45 PM EDT

Presenting Author(s)

AM

Ayano Medo

PhD student
Graduate School of Informatics, Kyoto University, Kyoto, Japan

Coauthor(s)

NO

Nobuhito Ohte

Graduate School of Informastics, Kyoto University, Japan
HK

Hiroki Kajitani

Graduate School of Informatics, Kyoto University, Japan
TN

Takashi Nose

Graduate School of Informatics, Japan
YM

Yuki Manabe

Graduate School of Agriculture, Kyoto University, Japan
TS

Tatsuya Sugawara

Graduate School of Agriculture, Kyoto University, Japan
YO

Yuji Onishi

Center for Ecological Research, Kyoto University, Japan
AG

Akiko S. Goto

Center for Ecological Research, Kyoto University, Japan
KK

Keisuke Koba

Center for Ecological Research, Kyoto University, Japan
NA

Nobuaki Arai

National Fisheries University, Japan
YM

Yasushi Mitsunaga

Faculty of Agriculture, Kindai University, Japan
MK

Manabu Kume

Field Science Education and Research Center, Kyoto University, Japan
HN

Hideaki Nishizawa

Graduate School of Informatics, Kyoto University, Japan
DK

Daichi Kojima

Graduate School of Informatics, Kyoto University, Japan
AY

Ayako Yokoyama

Graduate School of Agriculture, Kyoto University, Japan
TY

Toshiro Yamanaka

The Graduate School of Marine Science and Technology, Tokyo University of Marine Science and Technology, Japan
TV

Thavee Viputhanumas

Inland Aquaculture Research and Development Division, Department of Fisheries, Thailand
HM

Hiromichi Mitamura

Field Science Education and Research Center, Kyoto University, Japan

Background/Question/Methods

Recycling inorganic nutrients that sunk to profundal zone is important to increase primary production in an aquatic ecosystem. However, in a reservoir, there has been limited information on vertical transportation of inorganic nutrient generated in anoxic hypolimnion zone to higher trophic levels in oxygenated limnetic zone. The objective of our study was to trace uptake of reduced compound by consumers using multiple stable isotopes (carbon [δ¹³C], nitrogen [δ¹⁵N], and sulfur [δ³⁴S]) and the composition of fatty acids (FAs). Here, we expected the striped catfish (Pangasianodon hypophthalmus) rely on reduced compound in a reservoir due to its high hypoxia tolerance. In the Kaeng Krachan Reservoir, western Thailand, we collected muscle samples of the catfish (n = 25 for juvenile [37–50 cm in total length]; n = 11 for adult [80–106 cm in total length]) for stable isotope and FA composition analysis. δ¹³C and δ¹⁵N of periphyton and particulate organic matter (POM) were used as an endmember of photoautotrophs. Using δ³⁴S, we inferred a use of organic matter derived from anoxic zone and/or oxic-anoxic interfaces in the catfish. In addition, we determined the FA composition of the catfish to estimate the origin of organic matter (algae vs. bacteria).

Results/Conclusions

The striped catfish in the reservoir represented the different isotopic signatures and FA composition between adult and juvenile. For the adult catfish, δ¹³C value were intermediate between periphyton and POM, while the δ¹⁵N value was higher than that of periphyton and POM. The adult catfish also contained more algae-specific FAs than bacteria-specific FAs, suggesting that they were feeding on photoautotrophs. On the other hand, the juvenile catfish showed lower δ¹³C and δ¹⁵N than that of periphyton and POM, suggesting that it used alternative sources of autochthonous organic matter as well as photoautotrophs. The juvenile catfish exhibited lower δ³⁴S value than δ³⁴S–sulfate of water column is likely to be influenced by sulfide. The juvenile catfish was characterized by rich bacterial FAs more than algal FAs. Our findings suggest that inorganic matter pooled in an anoxic zone is converted to organic matter via chemosynthetic bacteria and then consumed by the juvenile catfish. Overall, inorganic nutrient matters derived from the anoxic hypolimnion zone may indirectly support the production of consumers at the oxidation environment in a reservoir.