Beach sand as a biofilter: enzymatic activity and organic matter relationships in oligotrophic sites differently influenced by anthropogenic pressures and morphodynamism
Sandy beaches provide a number of ecosystem services, such as the breakdown of organic matter (OM), nutrient mineralisation and water filtration. These environments may be considered as biofilters, able to regulate the transport and transformation of OM from land to sea and vice-versa, due to the porous structure of the sediment and the colonisation by microorganisms. The efficiency of OM recycling performed by enzymatic activities (EAs) was evaluated in three beaches of the NW Mediterranean Sea, characterised by different anthropogenic pressure (urbanisation), and morphodynamic characteristics (exposition to waves). The sampling was focused on the area that includes the swash zone and the wet emerged beach. Urbanisation significantly influenced EAs, leading to a decoupling between the lipolytic EAs and the lipid content of sediment. Natural and anthropogenic lipids, showing higher turnover times than other OM (proteins), accumulated in the sediment, notwithstanding the very high lipolytic activities. In the sheltered side of the urbanised sites, significant correlations between EAs, sedimentary OM and seawater inorganic nutrients were recorded, confirming the biofilter activity. In the exposed sites, the wave action increased the exchanges with the sea by water flushing inside the sediment, and EAs were related mainly to salinity. Especially in the least urbanised beach, coarse texture, higher pendency and heterogeneity of the sediment decreased the biofilter activity, allowing photosynthetic producers to increase their biomass. In this case, the beach hosted production of fresh OM, contributing to fulfil the trophic web requirements.
This work was funded by the project “Environmental quality of urban and urbanised beaches of the Ligurian coastal area and ecological effects on benthic communities”, in the framework of the Research Projects of the University of Genova, 2012. We thank the three reviewers.
All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by CM and ACH. The first draft of the manuscript was written by CM and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.
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Conflict of interest
The authors declare that they have no conflict of interest.
- Caddy JF, Defeo O (2003) Enhancing or restoring the productivity of natural populations of shellfish and other marine invertebrate resources. FAO Fish Tech Pap 448, FAO, RomeGoogle Scholar
- Clarke KR, Warwick RM (2001) Changes in marine communities: an approach to statistical analysis and interpretation, 2nd edn. PRIMER-E, PlymouthGoogle Scholar
- Griggs GB (2005) The impacts of coastal armoring. Shore Beach 73:13–22Google Scholar
- Hansen HP, Grasshoff K (1983) Automated chemical analysis. In: Grassoff K, Ehrhardt M, Kremling K (eds) Methods of seawater analysis. Verlag Chemie, Weinheim, pp 347–379Google Scholar
- Hoppe HG (1993) Use of fluorogenic model substrates for extracellular enzyme activity (EEA) measurement of bacteria. In: Kemp PF, Sherr BF, Sherr EB, Cole JJ (eds) Handbook of methods in aquatic microbial ecology. Lewis Publishers, Boca Raton, pp 423–431Google Scholar
- Innocenti L, Pranzini E (1993) Geomorphological evolution and sedimentology of the Ombrone river delta, Italy. J Coastal Res 9:481–493Google Scholar
- Lorenzen C, Jeffrey J (1980) Determination of chlorophyll in seawater. UNESCO Tech Pap Mar Sci 35:1–20Google Scholar
- Mudryk Z, Podgórska B (2005) Spatial variability in the activity of hydrolytic enzymes in a marine beach (southern Baltic sea). Pol J Ecol 53:255Google Scholar
- Mudryk ZJ, Podgórska B, Ameryk A (2001) Bacteriological characterisation of a Baltic sandy beach in summer. Ecohydrol Hydrobiol 1:503–509Google Scholar
- Salvo V-S, Marin V, Misic C, Moreno M, Fabiano M (2003) Ecological response to the wave action in the swash zone of aLigurian beach (NW Mediterranean). In: Proceedings of the 6th international conference on the Mediterranean coastal environment MEDCOAST 03: Coastal Ecosystems, Ravenna, 7–11 October 2003Google Scholar
- Tomaselli A, Spinetti I, De Falco L, Brandino A, Grita M (2008) Studio relativo alla disponibilità idrica dei corpi idrici non significativi ricadenti nel versante ligure Il bacino del torrente Sturla Provincia di Genova, p 72. https://cartogis.cittametropolitana.genova.it/cartogis/pdb/bilancio_idrico/bilancio_idrico/ambito14/testi/relazione%20sturla.pdf. Accessed 2014