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Ecology

Title:		Multiple controls of community structure and dynamics in a sublittoral marine environment
Author(s):		Hereu B; Zabala M; Sala E;
Address:		"Departament d'Ecologia, Facultat de Biologia, Universitat de Barcelona, Diagonal 645, 08028 Barcelona, Spain. hereu@ub.edu"
Journal Title:		Ecology
Year:		2008
Volume:		89
Issue:		12
Page Number:		3423 - 3435
DOI:		10.1890/07-0613.1
ISSN/ISBN:		0012-9658 (Print) 0012-9658 (Linking)
Abstract:		"The structure and dynamics of ecological communities can be determined by both top-down (e.g., predation) and bottom-up (e.g., energy inputs) processes, which can act synergistically and across spatial and temporal scales. Here we aimed at understanding the role of multiple controls in a Mediterranean rocky sublittoral marine community that harbors a diverse algal community and strongly interacting herbivores, and which is subject to marked seasonality in energy inputs. We conducted an experiment by manipulating densities of the major consumers of benthic algae (fishes and sea urchins) in approximately 100-m2 enclosures in a marine reserve, and monitored algal assemblages over two and a half years. Most algae showed a marked annual cycle, with a biomass peak in late spring/summer and low biomass in winter, following seasonal fluctuations in resource availability, indicating the existence of bottom-up processes. Sea urchins reduced the abundance of most algal species, indicating the existence of top-down processes. The effect of fish grazing on algal abundances was significantly weaker. Sea urchin grazing was inhibited when predatory fish were present. Multivariate analysis showed that the interaction between seasonal resource inputs and herbivory induced the formation of algal assemblages characterized by different species abundances. The organization of algal assemblages was determined by the synergistic interaction between top-down and bottom-up processes: top-down control regulated total algal abundance, while bottom-up control determined seasonal fluctuations"
Keywords:		Animals *Biomass *Ecosystem Eukaryota/*physiology Fishes/physiology *Food Chain Mediterranean Sea Multivariate Analysis Population Dynamics Predatory Behavior/*physiology Sea Urchins/physiology Seasons;
Notes:		"MedlineHereu, Bernat Zabala, Mikel Sala, Enric eng Research Support, Non-U.S. Gov't 2009/01/14 Ecology. 2008 Dec; 89(12):3423-35. doi: 10.1890/07-0613.1"