Pablo G. Navarro

Patrones de abundancia y talla de Holothuria sanctori, Holothuria mammata y Holothuria arguinensis (Echinodermata: Holoturoidea) en la isla de Gran Canaria, Atlántico oriental

Se estudiaron los patrones espacio-temporales de abundancia y talla de Holothuria sanctori, H. mammata y H. arguinensis desde febrero de 2009 a enero de 2010...

Contrasting patterns of amphipod dispersion in a seagrass meadow between day and night: consistency through a lunar cycle

ABSTRACT Changes in light intensity, typically over the course of a day, affect the dispersion of aquatic organisms at short temporal scales. Amphipods, for example, have strong behavioural responses to light conditions. In this study, we used amphipod assemblages inhabiting a Cymodocea nodosa seagrass meadow on the east coast of Gran Canaria Island (eastern Atlantic) to test whether short-term dispersion of seagrass-associated amphipods differed between day and night, testing the consistency throughout an entire lunar cycle. Replicated artificial seagrass units were deployed, and subsequently retrieved, during the day (from 8:00 am to 18:00 pm) and the night (from 18:00 pm to 8:00 am) on three consecutive days within each of the four moon phases of a complete lunar cycle. We collected 13,467 amphipods corresponding to 32 species and 17 families. Significantly larger abundances of amphipods were collected during the night through the entire moon cycle. The total abundance of amphipods was also affected by the moon phases; under full moon, larger abundances of amphipods dispersed into the artificial seagrass units followed by the third quarter, the new moon and the first quarter. The species density of amphipods per unit followed the same pattern. In conclusion, the short-term dispersion of amphipods living in a seagrass meadow was considerably greater during the night than the day, while dispersion of amphipods was more intense under full moon.

Colonization patterns of decapods into artificial collectors: seasonality between habitat patches

Understanding colonization of new habitats by recruits is essential to comprehend local abundance patterns of adult populations. Colonization of benthic habitats by new colonizers is achieved through the influx of larvae from the water column and movements from adjacent habitats. Colonization, i.e., the composition and abundance of new colonizers, into a focal habitat may be affected by surrounding habitats. In this study, we investigated seasonal variation through an annual cycle in postlarval settlement patterns of decapod crustaceans colonizing artificial collectors on different habitats, in particular: Cymodocea nodosa seagrass meadows, sandy patches, ‘urchin-grazed’ barrens and macroalgal-dominated beds, which are arranged in patches within seascapes in the eastern Atlantic. Our results showed that: 1) decapods, at least some species, settle preferentially on artificial collectors deployed on vegetated substrates when compared to those deployed on unvegetated substrates; 2) despite most decapods have a planktonic larval phase with wide oceanic dispersal, the presence of crustaceans in particular habitats suggests a great specificity at their early post-larval stages; and 3) although subtropical waters of Gran Canaria have a weak seasonal variation, early postlarval stages of decapod crustaceans showed two distinct settlement periods, i.e., a ‘cold’ and a ‘warm’ season.

Colonization of Prosobranch Gastropods onto Artificial Substrates: Seasonal Patterns between Habitat Patches

Abstract: We used artificial substrates to investigate the seasonal variation in colonization patterns of subtidal prosobranch gastropods in Gran Canaria (Canary Island, Spain, north-eastern Atlantic), via monthly deployment of artificial substrates throughout an entire annual cycle from February 2009 to January 2010, on each of four habitat patches (seagrasses, sandy patches, ‘urchin-grazed’ barrens and macroalgaldominated beds) within a coastal landscape. A total of 8,524 prosobranch gastropods, including 12 dominant taxa, were collected as postlarval, juvenile, and adult individuals. In general the amount of variability explained by the type of habitat slightly dominated over seasonal variation, which was outweighed by variation from month to month, to explain colonization patterns. Throughout the study, larger numbers of colonizers of Bittium spp. (Leach in Gray, 1847), Columbella adansoni (Menke, 1853), Gibberula caelata (Monterosato, 1877), Mitra spp. (Lamarck, 1798), Rissoa spp. (Freminville in Desmarest, 1814), and Smaragdia viridis (Linnaeus, 1758) were observed in artificial substrates deployed in vegetated substrates, highlighting the relevance of vegetation as a matrix habitat for subtidal prosobranch gastropods. Cerithium rupestre (Risso, 1986) and Clavatula mystica (Reeve, 1843), however, were mainly observed on sandy patches. Rissoa spp. showed a peak in the arrival of new colonizers during spring-early summer whereas Tricolia pullus canarica (Nordsieck, 1973) showed a peak during winterearly spring. Importantly, the other prosobranch gastropods did not show significant differences in the arrival of colonizers between annual seasons. In summary, these results demonstrate that seasonality is strongly outweighed by small-scale temporal variability (here variation from month to month) and the type of habitat patch as drivers of prosobranch gastropod colonization patterns in coastal landscapes.