Decomposition is essential for carbon and nutrients cycling for all ecosystems (Hoorens et al., 2003Hoorens, B., Aerts, R. and Stroetenga, M., 2003. Does initial litter
chemistry explain litter mixture effects on decomposition? Oecologia, vol. 137,
no. 4, p. 578-586. http://dx.doi.org/10.1007/s00442-003-1365-6.
PMid:14505026
http://dx.doi.org/10.1007/s00442-003-136...
). In lentic aquatic
environments (e.g., lakes and reservoirs), aquatic macrophytes are the main
autochthonous detritus source, and their mineralization is fundamental for maintaining
biogeochemical cycles, associated with energy flux and detritus food-webs. (Bianchini Junior et al., 2014BIANCHINI JUNIOR, I., Cunha-Santino, MB., Ribeiro, JU. and Penteado,
DGB., 2014. Implication of anaerobic and aerobic decomposition of .
Eichhornia azurea (Sw.) Kunth. on the carbon cycling in a
subtropical reservoirBrazilian Journal of Biology = Revista Brasileira de
Biologia, vol. 74, no. 1, p. 100-110. http://dx.doi.org/10.1590/1519-6984.17912.
PMid:25055091
http://dx.doi.org/10.1590/1519-6984.1791...
). In disturbed
systems, some of these aquatic plants are potentially invasive due its high growth rates
and elevated productivity (Pieterse and Murphy,
1990Pieterse, AH. and MURPHY, KJ. 1990. Aquatic Weeds. The ecology and
management of nuisance aquatic vegetation. Oxford: Oxford Science Publications.
616 p.). The excessive growth of invasive submerged macrophytes, and
consequently accumulation of biomass, provides increased rates of decomposition, leading
to reductions in dissolved oxygen concentrations, changes of redox potential, increases
of detritus accumulation rates and consequential changes in biogeochemical cycles (Reddy and Delaune, 2008Reddy, KR. and DELAUNE, RD. 2008. Biochemistry of wetlands - science
and applications. Boca Raton: CRC Press. 774
p.). Considering the need for
understand nutrient and carbon cycling processes involving invasive macrophytes, we
compared the aerobic decomposition of two important same niche submerged macrophytes,
the Brazilian native Egeria densa Planch. and the exotic
Hydrilla verticillata (L.f.) Royle.
We collected and processed samples of H. verticillata, E.
densa and water in the Jupiá and Porto Primavera reservoirs, both located
in Paraná River Basin, Brazil (Chiba de Castro et al.,
2013Chiba de Castro, WA., Cunha-Santino, MB. and BIANCHINI JUNIOR, I.,
2013. Anaerobic decomposition of a native and an exotic submersed macrophyte in
two tropical reservoirs. Brazilian Journal of Biology = Revista Brasileira de
Biologia, vol. 73, no. 2, p. 299-307.
http://dx.doi.org/10.1590/S1519-69842013000200010.
PMid:23917557
http://dx.doi.org/10.1590/S1519-69842013...
) and aerobic incubations and carbon fraction estimations were carried
out in the laboratory (Cunha-Santino and Bianchini
Junior, 2002Cunha-Santino, MB. and BIANCHINI JUNIOR, I., 2002. Humic substance
mineralization in a tropical oxbow lake (São Paulo, Brazil). Hydrobiologia, vol.
468, no. 1-3, p. 33-43.
http://dx.doi.org/10.1023/A:1015214005279.
http://dx.doi.org/10.1023/A:101521400527...
) during 80 days. The oxygen consumption (OC) kinetics from
mineralization of aquatic plant detritus was fitted using a non-linear method
(Levenberg-Marquardt iterative algorithm; Bianchini
Junior et al., 2014BIANCHINI JUNIOR, I., Cunha-Santino, MB., Ribeiro, JU. and Penteado,
DGB., 2014. Implication of anaerobic and aerobic decomposition of .
Eichhornia azurea (Sw.) Kunth. on the carbon cycling in a
subtropical reservoirBrazilian Journal of Biology = Revista Brasileira de
Biologia, vol. 74, no. 1, p. 100-110. http://dx.doi.org/10.1590/1519-6984.17912.
PMid:25055091
http://dx.doi.org/10.1590/1519-6984.1791...
). To verify differences among aerobic decomposition, a
co-variance analysis test (ANCOVA) was applied (PAST, v.2.01).
The kinetics parameterization obtained from the fitting of experimental data presented
high determination coefficients; H. verticillata presented significant
(ANCOVA; F = 36.42, p<0.001) higher oxygen consumption than E. densa
(Figure 1). The significant differences
between the OC from H. verticillata and E. densa
mineralization can be explained by the lignin content. H. verticillata
presents 50% higher refractory fraction content than E. densa due to
lignin content (Chiba de Castro et al., 2013Chiba de Castro, WA., Cunha-Santino, MB. and BIANCHINI JUNIOR, I.,
2013. Anaerobic decomposition of a native and an exotic submersed macrophyte in
two tropical reservoirs. Brazilian Journal of Biology = Revista Brasileira de
Biologia, vol. 73, no. 2, p. 299-307.
http://dx.doi.org/10.1590/S1519-69842013000200010.
PMid:23917557
http://dx.doi.org/10.1590/S1519-69842013...
).
The most recalcitrant quality of lignin, when compared with the other fibers (i.e.
cellulose and hemicellulose), requires a great proportion of energy allocated to
mineralization (Kourtev et al., 2002Kourtev, PS., Ehrenfeld JG. and HUANG, WZ., 2002. Enzyme activities
during litter decomposition of two exotic and two native plant species in
hardwood forests of New Jersey. Applied Soil Ecology, vol. 34, no. 9, p.
1207-1218.) and
consequently high OC. The accentuated OC in the first days occurred due mineralization
of labile compounds, displaying a high velocity and high oxygen demand. The subsequent
decrease in OC is related with predominance of refractory compounds, with lower
mineralization rates. Refractory fraction can be metabolized 10 to 20 times slower than
the labile fraction (Gillon et al., 1994Gillon, D., Joffre, R. and Ibrahima, A., 1994. Initial litter
properties and decay rate: a microcosm experiment on Mediterranean species.
Canadian Journal of Botany, vol. 72, no. 7, p. 946-954.
http://dx.doi.org/10.1139/b94-120.
http://dx.doi.org/10.1139/b94-120...
).
Changes in the species composition of plant communities could be result in changes in
the enzymatic activities of the microbiota, mainly in heavily invaded communities by
exotic species and could also explain these differences found (Kourtev et al., 2002Kourtev, PS., Ehrenfeld JG. and HUANG, WZ., 2002. Enzyme activities
during litter decomposition of two exotic and two native plant species in
hardwood forests of New Jersey. Applied Soil Ecology, vol. 34, no. 9, p.
1207-1218.). In addition, the temporal evaluation of OC
allows the indirect description of microorganism metabolism as result of decay processes
in aquatic ecosystems, once the recognition the proportionality among the substrate
disappearance and the formation of microbial biomass products (Bianchini Junior et al., 2006BIANCHINI JUNIOR, I., CUNHA-SANTINO, MB. and PERET, AM., 2006. A
mesocosm study of aerobic mineralization of seven aquatic macrophytes. Aquatic
Botany, vol. 85, no. 2, p. 163-167.
http://dx.doi.org/10.1016/j.aquabot.2006.03.001.
http://dx.doi.org/10.1016/j.aquabot.2006...
).
Temporal changes of oxygen consumption (OC) of (a) Hydrilla verticillata and (b) Egeria densa detritus in aerobic incubations.
H. verticillata and Egeria native species have so many
ecological and morphological similarities that they probably compete in the Paraná basin
(Sousa et al., 2009SOUSA, WTZ., THOMAZ, SM., MURPHY, KJ., SILVEIRA, MJ. and MORMUL,
RP., 2009. Environmental predictors of the occurrence of exotic (L. f.) Royle
and native . Hydrilla verticillataEgeria najas
Planch. in a sub-tropical river floodplain: the Upper River Paraná,
BrazilHydrobiologia, vol. 632, no. 1, p. 65-78.
http://dx.doi.org/10.1007/s10750-009-9828-3.
http://dx.doi.org/10.1007/s10750-009-982...
). However, due to faster
growth, H. verticillata would present the highest competitive potential
(Bianchini Junior et al., 2010BIANCHINI JUNIOR, I., CUNHA-SANTINO, MB., MILAN, JAM., RODRIGUES,
CJ. and DIAS, JHP., 2010. Growth of Hydrilla verticillata
(L.f.) Royle under controlled conditions. Hydrobiologia, vol. 644, no. 1, p.
301-312. http://dx.doi.org/10.1007/s10750-010-0191-1.
http://dx.doi.org/10.1007/s10750-010-019...
). The higher
oxygen demand of detritus and the potential dominance upon other submerged native
macrophytes, provides changes in the ecosystem in medium and long term as accumulation
of particulate refractory material in the sediments and the increased of anaerobic
heterotrophy.
Acknowledgements
This study was supported by CESP (P&D ANEEL, proc. nº 0061-011/2006), CNPq (proc. nº 302935/2007-0 and 131406/2010-8) and FAPESP (proc. nº 2007/002683-7).
References
- BIANCHINI JUNIOR, I., CUNHA-SANTINO, MB. and PERET, AM., 2006. A mesocosm study of aerobic mineralization of seven aquatic macrophytes. Aquatic Botany, vol. 85, no. 2, p. 163-167. http://dx.doi.org/10.1016/j.aquabot.2006.03.001.
» http://dx.doi.org/10.1016/j.aquabot.2006.03.001 - BIANCHINI JUNIOR, I., CUNHA-SANTINO, MB., MILAN, JAM., RODRIGUES, CJ. and DIAS, JHP., 2010. Growth of Hydrilla verticillata (L.f.) Royle under controlled conditions. Hydrobiologia, vol. 644, no. 1, p. 301-312. http://dx.doi.org/10.1007/s10750-010-0191-1.
» http://dx.doi.org/10.1007/s10750-010-0191-1 - BIANCHINI JUNIOR, I., Cunha-Santino, MB., Ribeiro, JU. and Penteado, DGB., 2014. Implication of anaerobic and aerobic decomposition of . Eichhornia azurea (Sw.) Kunth. on the carbon cycling in a subtropical reservoirBrazilian Journal of Biology = Revista Brasileira de Biologia, vol. 74, no. 1, p. 100-110. http://dx.doi.org/10.1590/1519-6984.17912. PMid:25055091
» http://dx.doi.org/10.1590/1519-6984.17912 - Chiba de Castro, WA., Cunha-Santino, MB. and BIANCHINI JUNIOR, I., 2013. Anaerobic decomposition of a native and an exotic submersed macrophyte in two tropical reservoirs. Brazilian Journal of Biology = Revista Brasileira de Biologia, vol. 73, no. 2, p. 299-307. http://dx.doi.org/10.1590/S1519-69842013000200010. PMid:23917557
» http://dx.doi.org/10.1590/S1519-69842013000200010 - Cunha-Santino, MB. and BIANCHINI JUNIOR, I., 2002. Humic substance mineralization in a tropical oxbow lake (São Paulo, Brazil). Hydrobiologia, vol. 468, no. 1-3, p. 33-43. http://dx.doi.org/10.1023/A:1015214005279.
» http://dx.doi.org/10.1023/A:1015214005279 - Gillon, D., Joffre, R. and Ibrahima, A., 1994. Initial litter properties and decay rate: a microcosm experiment on Mediterranean species. Canadian Journal of Botany, vol. 72, no. 7, p. 946-954. http://dx.doi.org/10.1139/b94-120.
» http://dx.doi.org/10.1139/b94-120 - Hoorens, B., Aerts, R. and Stroetenga, M., 2003. Does initial litter chemistry explain litter mixture effects on decomposition? Oecologia, vol. 137, no. 4, p. 578-586. http://dx.doi.org/10.1007/s00442-003-1365-6. PMid:14505026
» http://dx.doi.org/10.1007/s00442-003-1365-6 - Kourtev, PS., Ehrenfeld JG. and HUANG, WZ., 2002. Enzyme activities during litter decomposition of two exotic and two native plant species in hardwood forests of New Jersey. Applied Soil Ecology, vol. 34, no. 9, p. 1207-1218.
- Pieterse, AH. and MURPHY, KJ. 1990. Aquatic Weeds. The ecology and management of nuisance aquatic vegetation. Oxford: Oxford Science Publications. 616 p.
- Reddy, KR. and DELAUNE, RD. 2008. Biochemistry of wetlands - science and applications. Boca Raton: CRC Press. 774 p.
- SOUSA, WTZ., THOMAZ, SM., MURPHY, KJ., SILVEIRA, MJ. and MORMUL, RP., 2009. Environmental predictors of the occurrence of exotic (L. f.) Royle and native . Hydrilla verticillataEgeria najas Planch. in a sub-tropical river floodplain: the Upper River Paraná, BrazilHydrobiologia, vol. 632, no. 1, p. 65-78. http://dx.doi.org/10.1007/s10750-009-9828-3.
» http://dx.doi.org/10.1007/s10750-009-9828-3
-
(With 1 figure)
Publication Dates
-
Publication in this collection
May 2015
History
-
Received
08 Aug 2014 -
Accepted
14 Oct 2014