Hereu B et al. (2012), Multiple processes regulate long-term populatio...

ECB-ART-42438

PLoS One 2012 Jan 01;75:e36901. doi: 10.1371/journal.pone.0036901.

Show Gene links Show Anatomy links

Multiple processes regulate long-term population dynamics of sea urchins on Mediterranean rocky reefs.

Hereu B , Linares C , Sala E , Garrabou J , Garcia-Rubies A , Diaz D , Zabala M .

Abstract
We annually monitored the abundance and size structure of herbivorous sea urchin populations (Paracentrotus lividus and Arbacia lixula) inside and outside a marine reserve in the Northwestern Mediterranean on two distinct habitats (boulders and vertical walls) over a period of 20 years, with the aim of analyzing changes at different temporal scales in relation to biotic and abiotic drivers. P. lividus exhibited significant variability in density over time on boulder bottoms but not on vertical walls, and temporal trends were not significantly different between the protection levels. Differences in densities were caused primarily by variance in recruitment, which was less pronounced inside the MPA and was correlated with adult density, indicating density-dependent recruitment under high predation pressure, as well as some positive feedback mechanisms that may facilitate higher urchin abundances despite higher predator abundance. Populations within the reserve were less variable in abundance and did not exhibit the hyper-abundances observed outside the reserve, suggesting that predation effects maybe more subtle than simply lowering the numbers of urchins in reserves. A. lixula densities were an order of magnitude lower than P. lividus densities and varied within sites and over time on boulder bottoms but did not differ between protection levels. In December 2008, an exceptionally violent storm reduced sea urchin densities drastically (by 50% to 80%) on boulder substrates, resulting in the lowest values observed over the entire study period, which remained at that level for at least two years (up to the present). Our results also showed great variability in the biological and physical processes acting at different temporal scales. This study highlights the need for appropriate temporal scales for studies to fully understand ecosystem functioning, the concepts of which are fundamental to successful conservation and management.

PubMed ID: 22606306
PMC ID: PMC3350477
Article link: PLoS One

Genes referenced: LOC100887844

Article Images: [+] show captions

References [+] :

Babcock, Decadal trends in marine reserves reveal differential rates of change in direct and indirect effects. 2010, Pubmed

Babcock, Decadal trends in marine reserves reveal differential rates of change in direct and indirect effects. 2010, Pubmed
Ballesteros, A new methodology based on littoral community cartography dominated by macroalgae for the implementation of the European Water Framework Directive. 2007, Pubmed
Coma, Global warming-enhanced stratification and mass mortality events in the Mediterranean. 2009, Pubmed
Duggins, Interspecific facilitation in a guild of benthic marine herbivores. 1981, Pubmed
Duran, Genetic diversity and population structure of the commercially harvested sea urchin Paracentrotus lividus (Echinodermata, Echinoidea). 2004, Pubmed , Echinobase
Estes, Killer whale predation on sea otters linking oceanic and nearshore ecosystems. 1998, Pubmed , Echinobase
Guidetti, Marine reserves reestablish lost predatory interactions and cause community changes in rocky reefs. 2006, Pubmed , Echinobase
Guidetti, Relationships among predatory fish, sea urchins and barrens in Mediterranean rocky reefs across a latitudinal gradient. 2007, Pubmed , Echinobase
Hereu, Multiple controls of community structure and dynamics in a sublittoral marine environment. 2008, Pubmed , Echinobase
Hughes, Catastrophes, phase shifts, and large-scale degradation of a Caribbean coral reef. 1994, Pubmed
Jackson, Historical overfishing and the recent collapse of coastal ecosystems. 2001, Pubmed
Pinedo, Rocky-shore communities as indicators of water quality: a case study in the Northwestern Mediterranean. 2007, Pubmed
Sala, The structure of Mediterranean rocky reef ecosystems across environmental and human gradients, and conservation implications. 2012, Pubmed
Shears, Toxic cascades: multiple anthropogenic stressors have complex and unanticipated interactive effects on temperate reefs. 2010, Pubmed , Echinobase
Shears, Context-dependent effects of fishing: variation in trophic cascades across environmental gradients. 2008, Pubmed , Echinobase
Tegner, Sea urchin recruitment patterns and implications of commercial fishing. 1977, Pubmed , Echinobase
Thibaut, Long-term decline of the populations of Fucales (Cystoseira spp. and Sargassum spp.) in the Albères coast (France, North-western Mediterranean). 2005, Pubmed , Echinobase

	Figure 1. Study site.Medes Islands Marine Reserve. Locations of study sites inside (Tascons, Freueto, Vaca and Carall) and outside (Falaguer, Molinet, and Punta Salines) the reserve. The red line represents the limits of the Marine Reserve, where all fishing is prohibited.
	Figure 2. Paracentrotus lividus density over time.Number of Paracentrotus lividus (>1 cm diameter) per 10 m2 (mean ± SE) over time at each site in MIMR on a) boulder substrates and (b) vertical walls. Solid symbols represent sites within the reserve (R); open symbols represent sites in the nearby unprotected area (NR). Note the different scales on both types of habitat.

	Figure 4. Arbacia lixula density over time.The number of Arbacia lixula (>1 cm diameter) per 10 m2 (mean ± SE) over time at each site in the MIMR on a) boulder substrates and (b) vertical walls. Solid symbols represent sites within the reserve (R); open symbols represent sites in the nearby unprotected area (NR). Note the different scales of both types of habitat.