Food resource partitioning and competition among alvinellid polychaetes of Juan de Fuca Ridge hydrothermal vents

Abstract

Biotic communities in highly variable, frequently perturbed habitats are usually expected to be structured mainly by abiotic factors. In the highly variable deep-sea hydrothermal vent environment, physical and chemical factors are known to play an important role in limiting the distribution and abundance of species, but the importance of biotic interactions remains largely unresolved. The high density and biomass attained by the vent macrofauna suggest that resource partitioning and competition may be significant in these communities. This study of food resource utilisation at northeast Pacific deep-sea hydrothermal vents uses an approach based on stable carbon and nitrogen isotope analyses to characterise trophic interactions between the 3 dominant alvinellid polychaetes, Paralvinella palmiformis, P. sulfincola, and P. pandorae. We also examine size structure in sympatric and allopatric populations of P. palmiformis and P. pandorae. Results indicate that food resource partitioning occurs both intra-and interspecifically in P. palmiformis and P. sulfincola, and we advocate that this process contributes to explaining their co-existence at very high densities. In contrast, P. pandorae has a much more restricted trophic niche, overlaps P. palmiformis in diet and is much smaller in size when found in sympatry with P. palmiformis. P. pandorae is the most likely of the 3 species to be affected by intra-and/or interspecific competition for food, and this may explain the drastic change in the population size structure observed between successive years. Our work indicates that within the limits imposed by environmental conditions, biotic interactions such as food resource partitioning and competition can be significant factors structuring deep-sea hydrothermal vent communities.

Trophic ecology of siphonostomatoid copepods at deep-sea hydrothermal vents in the northeast Pacific

“…Other stable isotope studies have reported evidence for generalist feeding (Levesque et al 2003) in these 2 species, as well as a case of apparently exclusive feeding on a chemoautotrophic microbial food source (Limén et al 2007). Behavioural studies have shown P. sulphincola to limit its feeding activity to sulphide mineral surfaces around its tube opening and the tubes of neighbouring conspecifics (Morineaux et al 2002, Grelon et al 2006.…”

“…Previous studies suggest that P. sulfincola has a mixed diet typical of generalist feeding (Levesque et al 2003). The palm worm P. palmiformis is also known to have a varied diet (Levesque et al 2003), and can occur sympatrically with P. sulfincola under less severe hydrothermal conditions (Sarrazin et al 1999). Another siphonostomatoid copepod species, Benthoxinus spiculifer (Humes 1984), is also found on sulphide chimneys in habitats dominated by less severe fluid flows, where P. palmiformis is present (Tsurumi et al 2003).…”

“…Both sulphide worms (Tunnicliffe et al 1985, Morineaux et al 2002 and copepods may feed on chemoautotrophic bacteria, but the importance of bacteria in their diets remains uncertain. Previous studies suggest that P. sulfincola has a mixed diet typical of generalist feeding (Levesque et al 2003). The palm worm P. palmiformis is also known to have a varied diet (Levesque et al 2003), and can occur sympatrically with P. sulfincola under less severe hydrothermal conditions (Sarrazin et al 1999).…”

“…Stable isotopes (e.g. Van Dover & Fry 1989, Fisher et al 1994, Colaço et al 2002, Van Dover 2002, Levesque et al 2003 and fatty acid biomarkers (e.g. Pranal et al 1996, Pond et al 1997, Phleger et al 2005) have been used to study the feeding ecology of invertebrates in deep-sea hydrothermal vent communities.…”

Understanding population dynamics of a numerically dominant species at hydrothermal vents: a matrix modeling approach

“…In hydrothermal vent habitats, unpredictable fluctuations in the physico-chemical environment (e.g. temperature, O 2 , H 2 S) (Johnson et al 1988, Chevaldonne et al 1997, Sarrazin et al 1997, Tivey et al 2002, as well as variations in habitat complexity (Kelly & Metaxas 2008b), available substratum space (Tsurumi & Tunnicliffe 2003) or access to food resources (Levesque et al 2003 site could result in variations in growth of settlers, influencing subsequent recruitment. In addition, the low elasticities observed for P i and F i also indicate that processes such as predation or competition occurring during the post-settlement stages would be more important to the population dynamics of L. fucensis than those occurring during adult life.…”