Effect of upper beach macrofauna on nutrient cycling of sandy beaches: metabolic rates during wrack decay
Sandy beaches constitute a dynamic interface between marine and terrestrial environments, where inflows of organic matter occur mainly in the form of beach-cast wrack. Decomposition and processing of these inputs stand out as central components of ecosystem functioning and the biogeochemical processes associated with nutrient and carbon cycling. To investigate the effect of upper-beach macrofauna on wrack decomposition and carbon cycling, a manipulative experiment was carried out on Ladeira beach (42°34.33″N; 9°3.16″W—NW Spain) and ran for 43 days from 1 June 2011, where wrack decomposition rates and metabolism in the presence or absence of invertebrate macrofauna were assessed. The results showed that activities carried out by macrofauna inhabiting the upper beach are relevant in the decomposition of wrack deposits. Both the weight losses and the degradation rates were significantly higher in treatments with macrofauna access. CO2 fluxes measured throughout the experiment showed that wrack patches act as ‘hot spots’ of biogeochemical activity, supporting higher metabolic rates with maximum values of CO2 flux recorded in this study ~ 12 µmol C m−2 s−1. Microbial activity was estimated as being the main contributor to the respiration measured during wrack decay, but fragmentation and activities carried out by the macrofauna had significant effects on the mass loss, degradation rates and carbon fluxes associated with wrack decay process.
The authors thank J. Pascual and L. Gestoso for help with experiment placement and fieldwork, and L. Palacios for support in the macrofauna identification process. We would like to thank to two anonymous referees for suggestions and improvements of the manuscript. Thanks are also due to I. Emmett for proofreading the English revision of this manuscript.
This research was supported by the Xunta de Galicia (Regional Autonomous Government of Galicia—GRC 2013-004).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest to disclose.
All applicable international, national and/or institutional guidelines for sampling, care and experimental use of organisms for the study have been followed and all necessary approvals have been obtained.
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