학술논문
Synergistic control of C[O.sub.2] emissions by fish and nutrients in a humic tropical lake
Document Type
Academic Journal
Source
Oecologia. March 1, 2012, Vol. 168 Issue 3, p839, 9 p.
Subject
Language
English
ISSN
0029-8549
Abstract
Introduction The supersaturation of lake waters with C[O.sub.2] drives a globally significant C[O.sub.2] flux to the atmosphere (Cole et al. 1994, 2007; Duarte and Prairie 2005; Marotta et al. 2009a). [...]
Using experimental mesocosms, we tested the strength of bottom-up controls by nutrients and top-down controls by an omnivorous fish (Hyphessobrycon bifasciatus; family Characidae), and the interaction between them on the C[O.sub.2] partial pressure (pC[O.sub.2]) in the surface waters of a tropical humic lake (Lake Cabmnas, Brazil). The experiment included the addition of nutrients and fish to the mesocosms in a factorial design. Overall, persistent C[O.sub.2] emissions to the atmosphere, supported by an intense net heterotrophy, were observed in all treatments and replicates over the 6-week study period. The C[O.sub.2] efflux (average ± standard error) integrated over the experiment was similar among the control mesocosms and those receiving only fish or only nutrients (309 ± 2, 303 ± 16, and 297 ± 17 mmol C[O.sub.2] [m.sup.-2] [day.sup.-1], respectively). However, the addition of nutrients in the presence of fish resulted in a high algal biomass and daytime net autotrophy, reducing the C[O.sub.2] emissions by 35% (by 193 ± 7 mmol C[O.sub.2] [m.sup.-2] da[y.sup.-1]). These results indicate that high C[O.sub.2] emissions persist following the eutrophication of humic waters, but that the magnitude of these emissions might depend on the structure of the food web. In conclusion, fish and nutrients may act in a synergistic manner to modulate persistent C[O.sub.2] emissions from tropical humic lakes. Keywords C[O.sub.2] * Eutrophication * Hyphessobrycon bifasciatus * Humic lake * Tropical lake
Using experimental mesocosms, we tested the strength of bottom-up controls by nutrients and top-down controls by an omnivorous fish (Hyphessobrycon bifasciatus; family Characidae), and the interaction between them on the C[O.sub.2] partial pressure (pC[O.sub.2]) in the surface waters of a tropical humic lake (Lake Cabmnas, Brazil). The experiment included the addition of nutrients and fish to the mesocosms in a factorial design. Overall, persistent C[O.sub.2] emissions to the atmosphere, supported by an intense net heterotrophy, were observed in all treatments and replicates over the 6-week study period. The C[O.sub.2] efflux (average ± standard error) integrated over the experiment was similar among the control mesocosms and those receiving only fish or only nutrients (309 ± 2, 303 ± 16, and 297 ± 17 mmol C[O.sub.2] [m.sup.-2] [day.sup.-1], respectively). However, the addition of nutrients in the presence of fish resulted in a high algal biomass and daytime net autotrophy, reducing the C[O.sub.2] emissions by 35% (by 193 ± 7 mmol C[O.sub.2] [m.sup.-2] da[y.sup.-1]). These results indicate that high C[O.sub.2] emissions persist following the eutrophication of humic waters, but that the magnitude of these emissions might depend on the structure of the food web. In conclusion, fish and nutrients may act in a synergistic manner to modulate persistent C[O.sub.2] emissions from tropical humic lakes. Keywords C[O.sub.2] * Eutrophication * Hyphessobrycon bifasciatus * Humic lake * Tropical lake