The effect of macrofauna, meiofauna and microfauna on the degradation of Spartina maritima detritus from a salt marsh area

Abstract

-Decomposition of salt marsh plants results from physical, chemical and biological processes including abiotic and biotic fragmentation, microbial decay and chemical transformation. According to literature data, only a few species have the ability to feed directly on living plant material, so fungi and bacteria seem to be the principal competitors for the organic substrates. Nevertheless, by consuming bacteria, protists and fungi associated to the detritus, macrofauna and meiofauna recycle the incorporated nutrients. Moreover, this nutrient regeneration may be seen as an effective factor in maintaining and stimulating bacterial production. In fact, it is well known that many detritus feeding species have very low assimilation efficiencies. The objective of the present study was to compare the nutrient mass balance of carbon; nitrogen and phosphorus in Spartina maritima covered areas and bare bottom sediment, with and without contribution of macrofauna, meiofauna and microbial populations. Nutrients mass balance was studied taking into account the initial and final nutrient concentrations in the sediment, water and plant material. Faunal activity was measured as a function of remineralised carbon, nitrogen and phosphorus. The experimental set-up included sixteen sub-experiments, which varied with respect to type of fauna, plant biomass and oxic status. Each sub-experiment was performed in small glass containers (3 L) containing about 900 g wwt sediment and 2.5 L estuarine water. Plant material, cut from intact plants, sediment cores and estuarine water were brought from the southern arm of the Mondego estuary (Portugal). The results showed that although the bacterial activity was responsible for the Spartina maritima degradation, the presence of meiofauna and macrofauna significantly enhanced the process. Moreover, the presence of Spartina maritima positively affected the mineralisation of the sediment carbon and nitrogen, especially when the three faunal components were present, and denitrification rates were highest in the presence of the macrofauna and meiofauna. The present study suggests that macrofauna and meiofauna have an important role on the ecosystem nutrient flux and that fauna might function as a sink for excess nutrients, that otherwise could be exported to the coastal waters. © 1999 Éditions scientifiques et médicales Elsevier SAS Spartina maritima / decomposition / fauna / nutrient mass balance

Population structure, dynamics and production of Hydrobia ulvae (Pennant) (Mollusca: Prosobranchia) along an eutrophication gradient in the Mondego estuary (Portugal)

“…Although, a large part of the southern arm intertidal area still remains more or less unchanged, exhibiting sand muddy bottoms covered by Spartina maritima marshes [27] and Zostera noltii meadows, macroalgal blooms of Enteromorpha spp. have been regularly observed during the last 15 years.…”

The faunal role in the degradation of the common intertidal salt marsh plant Scirpus maritimus

“…The degradation period of Scirpus maritimus leaves in the presence of macrofauna was faster than that observed for Spartina maritima under similar experimental conditions (Lillebø et al, 1999a). The degradation periods, estimated according to 90% of mass loss, were respectively 57 days and 99 days, while initial C:N ratio was 16 (2.3% N and 38% C) and 16 (2.5% N and 40% C).…”

“…The initial biomass was calculated in ash free dry weight (g AFDW) and the mean value per glass container corresponded to 0.30 g S. plana, 1.99 g N. diversicolor, 1.88 g H. ulvae and 0.63 g C. carinata. To calculate the macrofauna initial biomass in ash free dry weight (g AFDW), the sorted specimens were measured (mm) or weighed (g wwt-wet weight), according to previous established length-weight relationships (Lillebø et al, 1999a;Ferreira et al, 2004;Verdelhos et al, 2005).…”

The benthic regeneration of N and P in the Great Brak estuary, South Africa

“…There have been no such studies conducted in TOCEs that link the benthic nutrient flux to different faunal groups in the overlying water column in South African estuaries. Studies from other parts of the world (Vetter and Hoppkinson, 1985;Hansen and Kristensen, 1998;Kristensen and Hansen, 1999;Lillebo et al, 1999;Lavrentyev et al, 2000;Webb and Eyre, 2004) have found that macrofauna enhance benthic reactivity and increase the efficiency of both inorganic nutrients and oxygen consumption between the water column and benthos. Trypaea australiensis Dana (formally Callianassa australiensis) increased benthic oxygen demand by 80% and approximately 15% was used for respiration by the shrimp while the remainder was used for oxidation reactions and microbial respiration (Webb and Eyre, 2004).…”