Role of nematodes in decomposition processes: Does within-trophic group diversity matter?

Abstract

The importance of biodiversity for the functioning of ecosystems is still very unclear. Many hypotheses, mainly based on terrestrial studies, have been formulated, focussing on the plant diversity-productivity relationship. In this study, diversity-related and species-specific effects of bacterivorous nematodes on the decomposition rate of cordgrass detritus Spartina anglica and on the associated microbial community were investigated using laboratory microcosm experiments. Four bacterivorous nematode species (Diplolaimelloides meyli, Diplolaimelloides oschei, Diplolaimella dievengatensis and Panagrolaimus paetzoldi) were added either separately or in combinations of 2 or 3 species to the microcosms. In contrast with previous reports, no stimulation of the decomposition process was observed in the presence of nematodes. Still, clear differences in process rates were found between nematode treatments. P. paetzoldi, reaching considerably higher densities than the other nematode species, suppressed bacterial activity and diversity, probably due to overgrazing. This was, however, not translated into slower decomposition. Within treatments exclusively containing monhysterid nematode species (D. meyli, D. oschei and D. dievengatensis), differences in microbial activity and decomposition rates were found, but again no link was observed between activity and decomposition. Our data did not support any hypothesis predicting enhancement of process rates with an (initial) increase in numbers of nematode species, or redundancy among the studied species. Rather, we obtained support for an idiosyncratic diversity model, as differences in the effect of bacterivore nematode species and species combinations could not be predicted at the start of the experiment. This could be explained by the inhibitory interactions between nematode species.

Is the meiofauna a good indicator for climate change and anthropogenic impacts?

“…However, shallow-water softsediment studies show that species identity and function seems to be more important than species richness for the maintenance of ecosystem functioning (Radwell and Brown 2008). For example, in an experimental study, De Mesel et al (2006) provide evidence for an idiosyncratic relationship between nematode species diversity and function in low-diversity systems. Furthermore, limited functional overlap between nematode species is observed in low diversity systems (De Mesel et al 2006;Gingold et al 2013).…”

“…For example, in an experimental study, De Mesel et al (2006) provide evidence for an idiosyncratic relationship between nematode species diversity and function in low-diversity systems. Furthermore, limited functional overlap between nematode species is observed in low diversity systems (De Mesel et al 2006;Gingold et al 2013). Using deep-sea nematodes as model organisms, Danovaro et al (2008) suggest that high nematode diversity may have a positive impact on deep-sea ecosystem functioning.…”

Unravelling the environmental drivers of deep-sea nematode biodiversity and its relation with carbon mineralisation along a longitudinal primary productivity gradient

“…A fourth point is that total nematode respiration was here estimated on the basis of total nematode biomass and temperature (de Bovée and Labat, 1993) and may not truthfully reflect in situ respiration by the nematode community. Environmental factors other than temperature (Braeckman et al, 2013) and biotic interactions (De Mesel et al, 2006) may influence nematode carbon processing rates. Sounder results would have been obtained from the direct measurement of oxygen consumption or carbon dioxide production by nematode communities in deep-sea sediments.…”

Populations of two prey nematodes and their interaction are controlled by a predatory nematode

“…These 2 bacterivorous species negatively affect each other's population development in laboratory microcosm experiments in the absence of predators, with D. meyli having a stronger inhibitory effect on D. oschei than vice versa (De Mesel et al 2006, dos Santos et al 2009. They have been shown to be very suitable prey for Enoploides (Moens et al 1999, 2000.…”

“…Moreover, the local diversity of nematode assemblages tends to be (very) high (Heip et al 1985, Wall & Moore 1999, Yeates et al 2009, and competitive, facilitative, and inhibitory interactions, even among closely related species, are important in shaping these assemblages (Mikola 1998, Ilieva-Makulec 2001, PostmaBlaauw et al 2005, De Mesel et al 2006, dos Santos et al 2009). It is unclear whether, and to what extent, predatory forces interfere with these horizontal interactions and affect assemblage structure and diversity.…”