Polychaetes associated to a Cymodocea nodosa meadow in the Canary Islands: assemblage structure, temporal variability and vertical distribution compared to other Mediterranean seagrass meadows

Abstract

The structure, diversity and temporal distribution of the infaunal polychaetes associated to Cymodocea nodosa meadows were studied in Tenerife (Canary Islands). The samples were collected monthly throughout a year, to depths between 13-16 m. The sediment was extracted by means of PVC cores, in which four layers were separated (i.e., 0-5 cm, 5-10 cm, 10-20 cm and 20-30 cm). 1,167 polychaete specimens, belonging to 69 taxa were collected, representing one of the most dominant groups in the benthic assemblage throughout all the year. The most common families were Syllidae, Paraonidae and Spionidae, both in terms of abundance and species richness. The dominant species were Streptosyllis bidentata, Aricidea assimilis and Exogone parahomoseta mediterranea, resulting also the only constant species throughout the year. The highest values of species richness, diversity, equitability and abundance of polychaetes occurred in September. The multifactorial analysis of abundances (i.e. cluster analysis and non-metric multi-dimensional scaling) indicated a temporal segregation of samples from July, August and September (i.e. the warmest months) with respect to those of the rest of the year, due to structural differences in the assemblage.Polychaete species have been found up to 30 cm depth in the sediment. Nevertheless, most of them (89%) occurred in the first 5 cm of the sediment, with an increase of specimens in deeper layers in February (i.e., due to punctual episodes of higher hydrodynamics). To compare the vertical distribution of polychaetes, additional core samples were collected in two seagrass meadows (i.e., C. nodosa and Ruppia cirrhosa) at the Ebro's Delta (NW Mediterranenan), in which five layers were separated (i.e. 0-5 cm, 5-10 cm, 10-15 cm, 15-20 cm, 20-25 cm). The results obtained in the R. cirrhosa meadow (98% of the polychaetes within the first 5 cm) agrees with those in the Canarian C. nodosa meadow, while the polychaetes reached up to 15 cm deep in a C. nodosa meadow (i.e., ≈ 39% between 0-5 cm, ≈ 41% between 5-10 cm, .≈ 20% between 10-15 cm). Our results supported that the structural characteristics of the assemblages appeared to be more strongly controlled by the combined characteristics of the sediment (i.e. lack of oxygen, granulometry and degree of compaction) than by the seagrass species building the meadow.2

Distribution patterns of Syllidae (Annelida: Polychaeta) from seagrass (<i>Zostera marina</i> and <i>Z. noltei</i>) meadows in the Ensenada de O Grove (Galicia, NW Spain)

“…In general, seagrass meadows reduce physical stress, trap sediment, reduce suspension, protect small invertebrates from predators, and enhance food availability, also adding complexity to the habitat (Orth et al 1984). In the case of Cymodocea nodosa and Zostera noltei, syllids are among the most abundant polychaete taxa in the foliar and rhizome layers (Giangrande and Gambi 1986, Gambi et al 1998, Brito et al 2005. In fact, the tridimensional structure provided by those seagrasses and especially the rhizome structure make available a variety of microhabitats for small-sized taxa.…”

“…In fact, the tridimensional structure provided by those seagrasses and especially the rhizome structure make available a variety of microhabitats for small-sized taxa. Syllids are mostly interstitial animals and therefore the availability of small spaces along the rhizomes could favour their presence (Giangrande 1985, Somaschini and Gravina 1994, Brito et al 2005. In fact, syllids require spatial structures at microhabitat rather than at macrohabitat level (Abbiati et al 1987, Giangrande 1988, while the interactions among syllids and with other macrofaunal species have also been suggested as factors controlling the abundance and, partially, the variability of syllid assemblages (Musco 2012).…”

“…seagrass, detritus and epiphytes) (Kitting et al 1984, Hily et al 2004, Fredriksen et al 2005 to the associated faunal assemblages. Among them, the most diverse taxa are generally polychaetes, molluscs and crustaceans (Gambi et al 1998, Nakaoka et al 2001, Arroyo et al 2006, which are often represented by small-sized, interstitial species that are also usually present in bare soft sediments (San Martín et al 1985, Sardá 1985, Brito et al 2005. In Zostera meadows, as in other seagrass meadows, these species may be favoured by the sediment retained by the seagrasses (Parapar et al 1994, Fredriksen et al 2010 and by the rhizomes and roots, which create spatial complexity within sediment and enable oxygenation (Tu Do et al 2011 and references therein).…”

Seasonal and diel changes in the structure of a crustacean decapod assemblage associated to a shallow Cymodocea nodosa meadow in northern Tunisia (Mediterranean Sea). An overview of the Mediterranean decapod taxocoenoses.

“…Studies on macrofaunal assemblage associated to small seagrass Cymodocea nodosa have been carried out in some Mediterranean areas and the adjacent Atlantic Ocean (e.g. Ledoyer, 1966Ledoyer, , 1968Scipione et al, 1996;Sánchez-Jerez et al, 1999;Guidetti & Bussotti, 2000;Reed & Manning, 2000;Barbera-Cebrián et al, 2002;Brito et al, 2005;Tuya et al, 2006;Schaffmeister et al, 2006;González et al, 2007;Como et al, 2008). Besides, very few studies have focused on Crustacean decapod assemblages (Števčić, 1991;García Raso et al, 2006;Schaffmeister et al, 2006;Mateo & García Raso, 2012).…”

Changes in seagrass polychaete assemblages after invasion by <i>Caulerpa racemosa</i> var. <i>cylindracea</i> (Chlorophyta: Caulerpales): community structure, trophic guilds and taxonomic distinctness

“…Among benthic invertebrates, the polychaetes are considered to be excellent descriptors of the structure of faunal assemblages, including those in association with seagrasses (Gambi et al, 1998;Brito et al, 2005). Although Posidonia oceanica beds lack exclusive polychaete species, the structure of their assemblages is very characteristic and tends to differ among the leaf stratum and the rhizomes and "matte".…”