Organic matter cycling in a neotropical reservoir: effects of temperature and experimental conditions

Abstract

AIM:This study reports a comparison between decomposition kinetics of detritus derived from two macrophyte species (Polygonum lapathifolium L.: Polygonaceae; Eichhornia azurea (Sw.) Kunth.: Pontederiaceae) growing in a neotropical reservoir (Brazil), under laboratory and field conditions, in order to assess hypotheses on the main differences in factors affecting organic matter cycling, including the effect of temperature. METHODS: Plant and water samples were collected from the reservoir in August 2009. In field incubation mass loss was assessed using a litter bag technique and in the laboratory the decay was followed using a decomposition chamber maintained under controlled conditions (i.e. in the dark, at 15 ºC and 25 ºC). A kinetic model was adopted to explain and compare the organic matter decay, ANOVA (Repeated Measures) testing was used to describe the differences between the treatments and a linear correlation was used to compare in situ and in vitro experiments. RESULTS: The mass decay was faster in natural conditions with rapid release of the labile-soluble portion. The simulated values of mineralization rates of dissolved organic matter and refractory organic matter were rapid in high temperatures (25 ºC). The high Q10 results (mainly for E. azurea), and experimental conditions, and outcomes of ANOVA testing indicate the temperature variation (10 ºC) influence the rates of mass decay. CONCLUSIONS: The results suggested rapid organic matter cycling in warm months (from October to December) supporting the microbial loop. Although the particulate organic matter losses are high in field conditions the results are of the same magnitude in both conditions suggesting an equivalence of the mass decay kinetic.

Pb and Zn contamination as rate-regulation agents on decomposition of two emergent macrophytes: a systemic approach

“…This correlation is often found in decomposition studies. Q 10 values found have presented similar values of that found by Bottino et al (2013). Temperature affects microorganism metabolic rates by increasing enzymatic reactions velocity (Davidson & Janssens, 2006) until a certain limit, from which rates begins to decrease due enzyme denaturation.…”

“…The concentration of DOC leachated from the H. coronarium detritus showed an increasing pattern over the experimental period. Decomposition studies usually reports an initial increase of DOC followed by a decrease tendency concomitant with MC formation (Bottino et al, 2013). The DOC increasing concentrations trend suggests a refractory nature of DOC (Cunha-Santino et al, 2010) or that this fraction was not rather used by heterotrophic microorganisms and owning of the metal presence.…”

The effect of hydrostatic pressure on the decomposition of inundated terrestrial plant detritus of different quality in simulated reservoir formation

“…At a later stage of decomposition, the 3rd mineralization route predominates, with the detritus exhibiting slow decomposition, and being more susceptible to variations in environmental factors (Bianchini & Cunha‐Santino ; Bottino et al . ; Fonseca et al . ; Quintão et al .…”

“…Other studies analysing the influence of physical and chemical variables on decomposition, such as temperature (Bottino et al . ), abrasion (Fonseca et al . ) and trophic status (Quintão et al .…”

“…Many physical and chemical conditions regarding plant detritus control the decomposition process (van der Valk ; Bottino et al . ; Fonseca et al . ).…”