Abstract
Terrestrial (trees, shrubs) and marine (seaweeds and seagrasses) organisms act as carbon (C) sinks, but the role of benthic suspension feeders in this regard has been largely neglected so far. Gorgonians are one of the most conspicuous inhabitants of marine animal forests (mainly composed of sessile filter feeders); their seston capture rates influence benthic-pelagic coupling processes and they act as C sinks immobilizing carbon in their long-living structures. Three gorgonian species (Paramuricea clavata, Eunicella singularis and Leptogorgia sarmentosa) were studied coupling data of population size structure, biomass and spatial distribution in a NW Mediterranean area (Cap de Creus, Spain) with feeding, respiration and growth rates. In the study area, we calculated that P. clavata sequestered 0.73 ± 0.71 g C m−2 year−1, E. singularis 0.73 ± 0.89 g C m−2 year−1 and L. sarmentosa 0.03 ± 0.02 g C m−2 year−1. To our knowledge, this is the first attempt to calculate the importance as C sinks of gorgonian species that we consider as a starting point to estimate the importance of marine animal forests in C sequestration, and to ensure appropriate management and protection especially in areas and at depths where they are concentrated.
Highlights
There is a large quantity of literature on the importance of terrestrial ecosystems as carbon (C) sinks[1]: the quantity of C removed by trees[2], bushes and other terrestrial vegetation on land, and even by the soil[3,4] has been already estimated
A total of 269 P. clavata colonies were observed in shallow waters (0–35 m depth), accounting for a total biomass of 1269.66 g ash free dry mass (AFDM) (19.16 ± 16.62 g AFDM m−2, mean ± standard deviation)
A total of 366 P. clavata colonies were observed in deep waters, corresponding to 1258.64 g AFDM (13.41 ± 13.91 g AFDM m−2)
Summary
There is a large quantity of literature on the importance of terrestrial ecosystems as carbon (C) sinks[1]: the quantity of C removed by trees[2], bushes and other terrestrial vegetation on land, and even by the soil[3,4] has been already estimated. Except for mixotrophic species, gorgonians are passive suspension feeders that rely completely on ambient flow and particle abundances in the water masses for feeding[18] Their diet is mainly composed of zooplankton[19,20,21], microplankton[22,23] and detrital particulate organic matter (POM)[24,25]. Through their feeding, they may influence the characteristics of surrounding waters especially when they reach high abundances[26]. Data on C assimilation are obtained by means of in situ or laboratory feeding and respiration experiments[40]
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