Variability of Organic Matter Processing in a Mediterranean Coastal Lagoon

Abstract

The spatial variability of plant organic matter processing was studied experimentally in a shallow coastal lagoon (Tancada lagoon, average depth: 37 cm, area: 1.8 km 2 ) in the Ebro River Delta (NE Spain). To determine the effect of hydrology and sediment characteristics on plant organic matter processing, leaves of Phragmites australis at the end of its vegetative cycle and whole plants of Ruppia cirrhosa (PETAGNA) GRANDE, just abscised, were enclosed in litter bags. Two different mesh sizes (100 µm and 2 mm) were used to study the effect of macroinvertebrates on decomposition. The bags were placed in the water column and approximately 15 cm above the sediment at 6 different locations in the lagoon. The experiment was performed twice, in autumn-winter and spring-summer. The effect of macroinvertebrates on decomposition rate was not significant in Tancada lagoon. Breakdown rates showed spatial differences only in spring-summer. In the autumn-winter experiment, the effect of strong wind masked the effects of environmental variables and hydrology on decomposition rate. In the spring-summer experiment, characterised by high stability of the water column, dissolved inorganic nitrogen (DIN) concentration in the water column and organic matter in the sediment were the main factors determining the variability of organic matter processing. A positive relationship was calculated between P. australis decomposition rate and dissolved inorganic nitrogen in spring-summer (r 2 = 0.92, p < 0.001).

Detritus accumulation and decomposition in a coastal lake (Acquatina–southern Italy)

“…On average the decomposition process slowed down from the upper part of the basin to the mouth following the salinity gradient in accordance with other decomposition studies (Odum and Heywood, 1978;Odum, 1988;Rossi and Costantini, 2000), but it accelerated in the central area which was also characterized by increasing water movements. P. australis was decomposed most rapidly among the three plant species with decay coefficients similar to those obtained in brackish waters at the same latitudes (Rossi and Costantini, 2000;Mene´ndez et al, 2004). In contrast, the decomposition rate of P. oceanica litter was slightly lower than observed in other studies (Romero et al, 1992;Cebrian and Duarte, 2001).…”

Spatial distribution and biomass of aquatic rooted macrophytes and their relevance in the metabolism of a Mediterranean coastal lagoon

“…The increase in DIC is actually delayed in relation to SRP and could also be related to carbonate dissolution due to low pH. On the other hand, a fast release of nutrients is expected due to the high decomposition rate of R. cirrhosa biomass (Menéndez et al, 2003;Menéndez et al, 2004). The average expected time to decompose 50% of R. cirrhosa biomass in the Albufera des Grau is 2 months (calculated from measured decomposition rates in the Albufera des Grau, authors' unpublished data), and the whole macrophyte community is mineralised after a year cycle (230 days to decompose the 95% of biomass).…”

Environmental factors affecting Phragmites australis litter decomposition in Mediterranean and Black Sea transitional waters

“…Litter breakdown has been widely studied in streams and rivers (Grac -a and Pereira, 1995;Diez et al, 2002;Pinna et al, 2003) and lakes (Gupta et al, 1996;van Dokkum et al, 2002); in contrast, studies of leaf litter decomposition in transitional aquatic ecosystems, such as coastal lagoons or river mouths, are less common (Rossi and Costantini, 2000;Mene´ndez et al, 2004;Bayo et al, 2005). In this type of ecosystem, plant litter decomposition may vary considerably from site to site in relation to many factors (Mendelssohn et al, 1999;Sangiorgio et al, 2004) such as water nutrient concentration (Mene´ndez et al, 2003(Mene´ndez et al, , 2004Bayo et al, 2005), and water salinity (Mendelssohn et al, 1999).…”

“…In this type of ecosystem, plant litter decomposition may vary considerably from site to site in relation to many factors (Mendelssohn et al, 1999;Sangiorgio et al, 2004) such as water nutrient concentration (Mene´ndez et al, 2003(Mene´ndez et al, , 2004Bayo et al, 2005), and water salinity (Mendelssohn et al, 1999).…”