Actual status of the sea urchin Diadema aff. antillarum populations and macroalgal cover in marine protected areas compared to a highly fished area (Canary Islands—eastern Atlantic Ocean)

Abstract

The aim was to determine the status of subtidal rocky benthic assemblages in three marine protected areas (MPAs) of the Canary Islands: (1) La Graciosa; (2) Mar de Las Calmas; (3) La Palma. Sea urchin (Diadema aff. antillarum) populations and non‐crustose macroalgal cover were surveyed, and used as an indicator of conservation status in the three MPAs as well as in a highly fished area (HFA‐Tenerife Island). Comparing characteristics between each MPA and the HFA, and considering issues of management and design, it was concluded that the three MPAs each have a different conservation status. ‘Mar de Las Calmas’ marine reserve was found to have the most desirable conservation status, followed by ‘La Palma’ marine reserve based on sea urchin populations and non‐crustose macroalgae assemblages. Conversely, ‘La Graciosa’ had the highest density of D. aff. antillarum and the lowest cover of non‐crustose macroalgae out of the three MPAs. Values were comparable to those at the HFA, which shows ‘La Graciosa’ to have the undesired conservation status. Different spatial distribution patterns of non‐crustose macroalgal as well as different algal composition cover were observed between the three MPAs and the HFA. These differences were principally attributed to the intensity of grazing activity of the key herbivore D. aff. antillarum. It is suggested that the different study areas correspond to different phase shifts that imply differing resilience of systems that should be taken into a count in future conservation strategies. Copyright © 2007 John Wiley & Sons, Ltd.

Effect of temperature on settlement and postsettlement survival in a barrens-forming sea urchin

“…However, it is at barren ground habitats where recruitment levels are highest. Well structured rocky bottom environments with high algal cover, as observed in El Hierro (Hernández et al 2008b), seem to increase postsettlement mortality and limit urchin recruitment. However, healthy macroalgal bed environments are progressively becoming less common and are heavily constrained by intense grazing from existing sea urchins.…”

“…Subsequent recruitment dynamics in complex life cycles are very unpredictable as it involves several stages, each of which can occur in a different habitat (Roughgarden et al 1988). Studying sea urchin recruitment supply processes is particularly relevant to coastal marine communities of the east Atlantic archipelagos, where productive macroalgal beds that remain only in some parts of the islands (Hernández et al 2008b), are vulnerable to severe urchin grazing (Hernández et al 2008a). In Madeira, Selvagean Islands and Canary Islands, urchins can dominate waters up to ~50 m in depth and cover ~89% of the total littoral rocky bottoms (Hernández et al 2008b), generating biodiversity loss and affecting many ecosystem services (Clemente 2007).…”

“…Studying sea urchin recruitment supply processes is particularly relevant to coastal marine communities of the east Atlantic archipelagos, where productive macroalgal beds that remain only in some parts of the islands (Hernández et al 2008b), are vulnerable to severe urchin grazing (Hernández et al 2008a). In Madeira, Selvagean Islands and Canary Islands, urchins can dominate waters up to ~50 m in depth and cover ~89% of the total littoral rocky bottoms (Hernández et al 2008b), generating biodiversity loss and affecting many ecosystem services (Clemente 2007). Yet few studies in these archipelagos have assessed the influence of environmental and biological factors in determining Diadema aff.…”

“…Migration of juvenile sea urchins is very low or undetectable (Rowley 1989) and is not believed to be relevant in their spatial arrangement. Nonetheless, features inherent to stands of the brown algae Lobophora variegata, which are abundant in the macroalgal beds at El Hierro (Hernández et al 2008b), may also affect PS. Alternatively, survival may be lower in these areas due to the complexity of macroalgal bed environments, or the absence of an appropriate habitat for early settlers (e.g.…”

Contrasting effects of protection from harvesting in populations of two limpet species in a recently established marine protected area

“…1). Unprotected areas were chosen along the eastern coastline of the island, with similar environmental conditions and experiencing low wave-exposure levels (Hernández et al 2008a) (Fig. 1).…”