See discussions, stats, and author profiles for this publication at: http://www.researchgate.net/publication/267868444 Ascidian-associated polychaetes: ecological implications of aggregation size and tube- building chaetopterids on assemblage structure in the Southeastern Pacific Ocean ARTICLE in MARINE BIODIVERSITY · OCTOBER 2014 Impact Factor: 1.1 · DOI: 10.1007/s12526-014-0283-7 READS 80 5 AUTHORS, INCLUDING: Nicolas Rozbaczylo Christian M. Ibáñez Pontifical Catholic University of Chile Universidad Andrés Bello 63 PUBLICATIONS 373 CITATIONS 42 PUBLICATIONS 298 CITATIONS SEE PROFILE SEE PROFILE Marcelo A. Flores Juan M Cancino Universidad Andrés Bello Catholic University of the Most Holy Conce… 14 PUBLICATIONS 23 CITATIONS 46 PUBLICATIONS 742 CITATIONS SEE PROFILE SEE PROFILE All in-text references underlined in blue are linked to publications on ResearchGate, Available from: Roger D. Sepúlveda letting you access and read them immediately. Retrieved on: 28 December 2015 Mar Biodiv DOI 10.1007/s12526-014-0283-7 ORIGINAL PAPER Ascidian-associated polychaetes: ecological implications of aggregation size and tube-building chaetopterids on assemblage structure in the Southeastern Pacific Ocean Roger D. Sepúlveda & Nicolás Rozbaczylo & Christian M. Ibáñez & Marcelo Flores & Juan M. Cancino Received: 13 May 2014 /Revised: 13 October 2014 /Accepted: 20 October 2014 # Senckenberg Gesellschaft für Naturforschung and Springer-Verlag Berlin Heidelberg 2014 Abstract Epifaunal polychaetes inhabit a range of habitat chaetopterid tubes influenced the polychaete assemblage structures built by other organisms, such as ascidians. Here, structure, evidencing differences between morphotypes. We we examine: i) the polychaete fauna inhabiting aggregations suggest that both sample volume and the habitat structuring of the ascidian Pyura chilensis in central Chile; ii) the rela- capacity of the chaetopterid tubes change the habitat complex- tionship between sample volume (aggregation size) and poly- ity of the ascidian aggregations and, hence, produce differ- chaete assemblage variables; and iii) the effect of a tube- ences between morphotypes related to the polychaete assem- building chaetopterid on the polychaete assemblage structure. blage structure. The chaetopterid tube load on aggregations determines two ascidian morphotypes, those with a high load of chaetopterid Keywords Habitat complexity . Ecosystem engineering . tubes (HT morphotype) and those with a low load of Diversity . Tube-building . Ascidians chaetopterid tubes (LT morphotype). From a total of 38 ag- gregations studied, we found 5,524 specimens belonging to 35 species of polychaetes. Three species were the most abundant Introduction in the aggregations (Phyllochaetopterus socialis, Nicolea lobulata,andTyposyllis magdalena), reaching 22% of total Epifaunal polychaetes are an important component of hard abundance. The number of species and individuals increased and soft bottom marine communities, capable of colonizing a with sample volume, but only the number of species number variety of biogenic substrates such as algae (Fredriksen et al. varied between morphotypes. Sample volume and the 2005; Sánchez-Moyano and García-Asencio 2009), sponges (Cinar and Ergen 1998), mollusks (Thiel and Ullrich 2002; Vasconcelos et al. 2007), worm tubes (Dubois et al. 2002; R. D. Sepúlveda (*) Sepúlveda et al. 2003a), crustaceans (Hoberg et al. 1982; Instituto de Ciencias Ambientales y Evolutivas, Facultad de Ciencias, Hernández et al. 2001), echinoderms (Britayev and Universidad Austral de Chile, Casilla 567, Valdivia, Chile e-mail: [email protected] Zamishliak 1996) and ascidians (Fielding et al. 1994; Cerda and Castilla 2001), among others. Within these biogenic hab- N. Rozbaczylo itats, polychaetes may find food and refuge (Woodin 1978; Departamento de Ecología, Facultad de Ciencias Biológicas, Edgar and Aoki 1993). Moreover, some of these species such Pontificia Universidad Católica de Chile, Santiago, Chile as borers, drillers or tube-builders may change the surround- C. M. Ibáñez ing environmental conditions through perforations, excava- Departamento de Ciencias Ecológicas, Facultad de Ciencias, tions or simply disturbing the surface sediment, thereby af- Universidad de Chile, Santiago, Chile fecting the other components of the fauna (Bolam and M. Flores Fernández 2002;Duboisetal.2002; Sepúlveda et al. 2003a). Departamento de Ecología y Biodiversidad, Facultad de Ecología y Certain species of ascidians are gregarious and capable of Recursos Naturales, Universidad Andres Bello, Santiago, Chile generating complex aggregations of organisms of different sizes living in close proximity. Aggregations of this kind of J. M. Cancino Departamento de Ecología, Facultad de Ciencias, Universidad organisms are called ecosystem engineers (Jones et al. 1994) Católica de la Santísima Concepción, Concepción, Chile because they modify the primary substrate, providing Mar Biodiv interstices and holes that serve as habitat for a diverse and Materials and methods abundant marine fauna (Guiler 1959; Cerda and Castilla 2001; Sepúlveda et al. 2003b). They also act as a biogenic substrate Study area and sample collection since the surface of the aggregation is a suitable substrate for direct settlement of many sessile organisms. Such aggrega- A total of 38 aggregations of the ascidian P. chilensis were tions therefore enhance local biodiversity by providing living obtained in San Vicente Bay, central Chile in 2000. From habitats that increase complexity (Voultsiadou et al. 2010). aggregations analysed and studied, 21 corresponded to aggre- The study of epibionts on ascidian aggregations is increasing gations with high density (average 0.465 tubes/ml., “hairy” because potential changes in the biogenic substrate resulting appearance, hereafter HT morphotype) and 17 to aggregations from disturbance or contamination will also impact the with low density (average 0.076 tubes/ml., “bald” appearance, associated fauna (Roberts et al. 2008). Moreover, some hereafter LT morphotype) of chaetopterid tubes (i.e., the load ascidians are commercially collected for human con- is six times greater in the HT than in LT morphotype). The sumption and their exploitation might produce cascading load of chaetopterid tubes displayed influences the number effects on the associated communities (Coleman and and size of individual ascidians, showing one to three ascid- Williams 2002; Monteiro et al. 2002). ians of small size in the HT morphotype, and two to six Pyura chilensis Molina, 1782, is a solitary ascidian species ascidians of medium size in the LT morphotype (Sepúlveda, that forms massive aggregations and/or patches on the subtidal pers. obs.). The LT morphotype samples were collected near seafloor, made up of one or several individuals (Guiler 1959). Roca Navia (36°44′49.71′S, 73°10′37.66”W) at a depth of Its geographic distribution range is between 10 and 44°S in the approximately 5 m below MLW, while the HT morphotype Southeast Pacific Ocean from the intertidal zone to a depth of samples were also collected at a depth of 5 m near playa 70 m (Vásquez 1983; Lancellotti and Vásquez 2000;Astorga Ramuntcho (36°45′11.99′S, 73°11′12.57”W) (Fig. 1); sam- and Ortíz 2006). Due to their high commercial value, these ples were collected by a diver equipped with “hookah” breath- ascidian aggregations are locally exploited along the Chilean ing gear. Samples of ascidians aggregations were removed coast by fishermen who recognize two types of aggregations from the rocky substrates using a spatula and metal hooks and depending on harvest location, “hairy” and “bald”; these two were wrapped in situ in a 1 mm-mesh polypropylene netting types can occur within the same area. The difference between to retain all associated polychaetes. The size (measured as aggregations is due to the high or low (or absent) load of tubes volume) of each aggregation was determined immersing the built by the chaetopterid polychaete Phyllochaetopterus sample in a 1,000-ml graduated cylinder and determining the socialis Claparède, 1869, which, when occurring at high volume of seawater displaced by the sample. Polychaetes densities on some ascidian aggregations, produces the “hairy” from each aggregation were separated with the aid of a ste- appearance. The polychaetes tubes are of considerable size reomicroscope and fixed in 10% formalin-seawater solution. (20–40 mm) and, since they are stiff and located on the surface Determination of total and per-sample taxonomic composition of the ascidian aggregation, change the external morphology of polychaete fauna was performed to the lowest possible as well as the effective size of the aggregations. Consequently, taxonomic level. Species abundance of all polychaetes was these tubes may change the hydrodynamics, increase the counted manually, and each species was assigned to trophic habitat complexity and oxygen demands and even produce and locomotion functional groups of polychaetes, following heterogeneous habitats in a uniform environment (Callaway Fauchald and Jumars (1979) and Jumars et al. (2014). 2006; Van Hoey et al. 2008). These effects of tube-building Although the results show differences between morphotypes, polychaetes may also influence larval settlement, dispersal we assume that the variations in polychaete assemblage may be patterns and, therefore, produce changes in the community due to the collection sites, since this study does not have variables and structure (Woodin 1978; Trueblood 1991;Qian replicated