Large seasonal or permanent blooms of green macroalgae (Ulva spp.) are one of the most widespread signs of eutrophication in shallow coastal environments. Macroalgal canopies attenuate light affecting negatively, or even fully inhibiting, microphytobenthic primary production at the sediment surface. In addition, macroalgal photosynthetic and respiratory activities affect the oxygen availability in the water column and the sediment, resulting in the reduction of oxygen availability. The reduction of oxygen concentration is particularly severe during the decomposition of the bloom, producing hypoxic or anoxic conditions even in the water column.
Anoxic conditions favour sulfate reduction activity in the decaying macroalgal canopy and in the sediment underneath. The sulphide produced as a result is highly toxic to benthic flora and fauna. Therefore, the presence of macroalgae blooms has significant cascading effects on the biogeochemical cycling of organic matter and nutrients at the sediment surface. Our work so far has focused mainly on the effect of macroalgae on the microphytobentic primary production, sediment net metabolism, and the C and N cycling in the sediment. We have used different experimental approaches, from field studies to both in situ and laboratory experiment.
Selected publications (more can be found here)
García-Robledo, E., Corzo, A., García de Lomas, J. van Bergeijk, S. A. (2008). Biogeochemical effects of macralgae decomposition on intertidal microbenthos: a microcosm experiment. Mar. Ecol. Prog. Ser. 356:139-151.
García-Robledo, E., Corzo, A., van Bergeijk, S. A., Yúfera, M. (2008). Impacto de las acumulaciones de macroalgas en la comunidad biológica intermareal. Revista de la Sociedad Gaditana de Historia Natural. Vol V: 115-137.
Corzo, A., van Bergeijk, S. A., García-Robledo, E. (2009). Effects of green macroalagal blooms on intertidal sediments: Net metabolism and carbon and nitrogen contents. Mar Ecol. Prog. Ser. 380: 81-93.
García-Robledo, E., Corzo, A. (2011). Effects of macroalgal blooms on carbon and nitrogen biogeochemical cycling in photoautotrophic sediments: An experimental mesocosm. Marine Pollution Bull.62:1550-1556.
García-Robledo, E., Corzo, A, Papaspyrou, S., Morris, E. (2012). Photosynthetic activity and community shifts of microphytobenthos covered by green macroalgae. Environmental Microbiology Reports. 4: 316-325.
Bohórquez, J., Papaspyrou, S., Yúfera, M., van Bergeijk, S.A., García-Robledo, E. Jimenez-Arias, J.L. Bright, M., Corzo, A. (2013). Effects of green macroalgal blooms on the meiofauna community structure in the Bay of Cádiz.Marine Pollution Bulletin 70:10-17.
García-Robledo, E. , Revsbech, N.P., Risgaard-Petersen, N., Corzo, A. (2013). Changes in N cycling induced by Ulva detritus enrichment of sediments. Aquatic Microbial Ecology 69: 113-122.
Funding
Ecological responses of microphytobenthos to the accumulation of nitrophilic macroalgae on intertidal sediments. Senescence and early diagenesis of the bloom, (Respuestas ecológicas del microbentos a la acumulación de macroalgas nitrófilas en sedimentos intermareales. Senescencia y diagénesis temprana del Bloom), CTM2006-04015/MAR, CICYT, Spain (110.957 €), PI: Prof. A. Corzo, 2006-2008.
Gestion environnementale des zones lagunaires à vocation aquacole (Gestión medioamabiental de zonas lagunares con vocación acuícola, ECOLAGUNES) SOE1/P2/F153. Interrg. Espacio SUDOE, UE. (220.075 euros), PI: Prof. I. Hernández (Subproyecto UCA), April 2009- April 2011.
Microecology and changes in the biogeochemical cycles of C and N in intertidal sediment induced by macroalgae blooms (Microecología y cambios en los ciclos biogeoquímicos del carbono y del nitrógeno en sedimentos intermareales producidos por floraciones de macroalgas) (CTM2009-10736), CICYT Spain (256.520 euros), PI: A. Corzo, 2010- 2012.
