Intertidal biofilms on rocky substratum can play a major role in estuarine carbon and nutrient dynamics

• Type: Article in International Scientific Journal
• Date: 2003

Authors

Magalhaes, CM (Author) Other; Adriano Bordalo (Author) ICBAS; Wiebe, WJ (Author) Other

Journal

Title: Marine Ecology - Progress Series

Vol. 258

Pages: 275-281

ISSN: 0171-8630

Publisher: Inter-Research Science Publishing

Indexing

ISI Web of Knowledge - 27 Citations

Scopus - 28 Citations

Other information

Authenticus ID: P-000-K4B

DOI: 10.3354/meps258275

Abstract (EN): Problems associated with increasing eutrophication of estuaries have stimulated many investigators to examine primary productivity and nutrient dynamics and transformations within and between the water column and sediments. Surprisingly, rocky surfaces, both natural and man-made, while comprising significant areas of many estuaries, have received virtually no investigation. In the Douro River estuary (Portugal), a flooded granitic valley, human intervention has progressively replaced intertidal soft sediments with hard surface areas. In this study we examine the role of the inorganic nutrient and metabolic dynamics of intertidal rocky biofilms in the lower estuary. Hourly net primary production (389 +/- 168 mg O-2 m(-2) h(-1)) greatly exceeded hourly net respiration rates (50 +/- 18 mg O-2 m(-2) h(-1)), results comparable to those of adjacent muddy and sandy sediments. These rocky biofilms consistently removed NO3+ and SiO44- from the water column (-595.4 +/- 236.7 and -305.7 +/- 209.6 mumoles m(-2) h(-1), respectively), whereas the net flux of NH4+ depended on light conditions (-123.15 +/- 22.45, 144.54 +/- 151.90 mumoles m(-2) h(-1), for light and dark treatments respectively). NO2- and PO43- net fluxes were low, with no clear trends in flux direction (-0.57 +/- 9.1 mumoles NO2- m(-2) h(-1) and 1.4 +/- 10.5 mumoles PO43- m(-2) h(-1)). Although rocky substrata constitute only 21% of the total planar intertidal zone of Douro estuary, they were responsible for 43% of the nitrate and 45% of the silicate uptake when compared to sandy and muddy sediment hourly rates within the total intertidal area. Thus intertidal rocky biofilms can represent important sites for biogeochemical activity.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 7