Variability of polychaete secondary production in intertidal creek networks along a stream-order gradient.

Tianjiang Chu,Qiang Sheng,Jihua Wu,Sikai Wang

doi:10.1371/journal.pone.0097287

Abstract

Dendritic tidal creek networks are important habitats for sustaining biodiversity and ecosystem functioning in salt marsh wetlands. To evaluate the importance of creek heterogeneity in supporting benthic secondary production, we assess the spatial distribution and secondary production of a representative polychaete species (Dentinephtys glabra) in creek networks along a stream-order gradient in a Yangtze River estuarine marsh. Density, biomass, and secondary production of polychaetes were found to be highest in intermediate order creeks. In high order (3rd and 4th) creeks, the density and biomass of D. glabra were higher in creek edge sites than in creek bottom sites, whereas the reverse was true for low order (1st and 2nd) creeks. Secondary production was highest in 2nd order creeks (559.7 mg AFDM m−2 year−1) and was ca. 2 folds higher than in 1st and 4th order creeks. Top fitting AIC models indicated that the secondary production of D. glabra was mainly associated with geomorphological characters including cross-sectional area and bank slope. This suggests that hydrodynamic forces are essential factors influencing secondary production of macrobenthos in salt marshes. This study emphasizes the importance of microhabitat variability when evaluating secondary production and ecosystem functions.

Highlights

The primary production in salt marshes can exceed 3900 g C m22yr21, making them among the most productive ecosystems in the world [1]
Researchers estimated that the secondary production of crabs (Chiromantes dehaani, Helice tientsinensis) in a Yangtze River estuarine salt marsh was 49.4 g AFDM m22year21, which is higher than that reported from other types of coastal wetlands at a similar latitude [5]
The density and biomass of D. glabra was highest in the 3rd order creeks (332.0 ind m22, 296.6 mg AFDM m22), followed by the 2nd order creeks (283.9 ind m22, 238.5 mg AFDM m22) and 1st order creeks (205.6 ind m22, 183.3 mg AFDM m22), and were lowest in the 4th order creeks (157.1 ind m22, 136.3 mg AFDM m22) (Figure 2)

Summary

Introduction

The primary production in salt marshes can exceed 3900 g C m22yr, making them among the most productive ecosystems in the world [1] This high level of primary production forms the energy base for abundant animal consumers, including benthic macrofauna, nekton, and shorebirds, and thereby sustains a high level of secondary production [2,3]. Secondary production is the formation of heterotrophic biomass through time [6]. It represents the cumulative responses of a population to abiotic and biotic stresses, and is an essential variable when quantifying food webs and ecosystem functioning such as material cycling and energy flow [7]. A better understanding of the spatial differences in production, especially at local scales, would be helpful to assess the spatial variability of ecosystem functioning

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