Settlement and recruitment of the sea urchin Paracentrotus lividus in two contrasting habitats in the Mediterranean

Abstract

We measured settlement and recruitment of one of the main invertebrate herbivores in the Mediterranean, the sea urchin Paracentrotus lividus, in 2 neighbouring and contrasting habitats: a seagrass meadow and a vertical rock wall. We quantified and compared temporal and bathymetrical variability in settlement and compared settlement with recruitment over a 4 yr period. Two settlement peaks were observed each year, a main peak in spring-early summer and a second peak in autumn-early winter. Interannual variability in settlement was very high (ca. 1 order of magnitude). Settlement was generally higher on the rock wall than in the seagrass meadow. No appreciable successful recruitment was observed in the meadow during the 4 yr studied despite the arrival of settlers. The few juvenile urchins found in the meadow were encountered at the shallow part and were completely hidden between the rhizomes. However, no differential settlement on the rhizome stratum was observed. In contrast to the seagrass meadow, recruitment occurred every year on the rock wall. Despite the arrival of settlers in both habitats, the population in the seagrass meadow appears to be recruitment-limited and probably mainly sustained by immigration, while settlement and recruitment appear to determine, to a certain extent, adult population structure and dynamics on the rock wall.

Herbivore control in connected seascapes: habitat determines when population regulation occurs in the life history of a key herbivore

“…In contrast, post-settlement survival was a critical factor explaining adult populations in macroalgal habitats. As shown in previous studies on P. lividus (López et al 1998, Tomas et al 2004, Prado et al 2012) and other benthic species (Hunt and Scheibling 1997), post-settlement mortality can represent an important filter of adult communities at this stage.…”

“…This method has been successfully used to determine settlement rates in seagrasses and macroalgal substrates with the assumption that it reflects the natural settlement rates that occur in those habitats (Hereu et al 2004, Prado et al 2012. We placed one collector in each area and habitat within each location at two times in the peak settlement period (May-June, see Tomas et al 2004). The collectors were weighed down to the bottom and floated ~20 cm in the water column, fixed to a buoy at one end to maintain the collector in a vertical position.…”

“…After an additional 15 days (T2) we recovered the new collectors (1 collector x 2 times x 3 areas x 2 habitats x 8 locations = 96 collectors). We used this procedure to maximize the probability of capturing the peak settlement period, which is related to seasonal increases in seawater temperature (Tomas et al 2004). Once in the laboratory, we washed the collectors under flowing water and filtered the water through a 250 µm mesh net.…”

Population Dynamics of Edible Sea Urchins Associated with Variability of Seaweed Beds in Northern Japan

“…14). The magnitude of settlement can vary by orders of magnitude interannually with some years showing little to no settlement Scheibling 2000, 2001;Tomas et al 2004;Jennings and Hunt 2010). The duration of the larval stage of M. nudus is also affected by kinds of food, amount of planktonic diatoms (Otaki et al 1984;Tenjin and Ishii 1984) and the water temperature, being about 15 days and 18-25 days at water temperatures of 20-23°C and 19.4°C, respectively.…”

Predation upon <i>Diadema</i> aff. <i>Zantillarum</i> in barren grounds in the Canary Islands

“…However, other factors such as topography and substrate complexity (McClanahan, 1994;McClanahan et al, 1999;Tomas et al, 2004;Hernández, 2006); recruitment (Underwood and Fairweather, 1989;Hereu et al, 2004); pollution and disease; and the variability of oceanographic events may also be important (see review in Pinnegar et al, 2000). The increased prevalence of urchin-dominated barrens throughout the Canary Islands could also be considered as one symptom of long-standing and intense use of the littoral and fishing resources (Aguilera et al, 1994;Tuya et al, 2004b).…”