Distribution and functional traits of polychaetes in a CO2 vent system: winners and losers among closely related species

Abstract

This authors' personal copy may not be publicly or systematically copied or distributed, or posted on the Open Web, except with written permission of the copyright holder(s). It may be distributed to interested individuals on request. MARINE ECOLOGY PROGRESS SERIES Mar Ecol Prog Ser Vol. 550: 121–134, 2016 doi: 10.3354/meps11727 Published May 25 Distribution and functional traits of polychaetes in a CO 2 vent system: winners and losers among closely related species M. C. Gambi 1 , L. Musco 2, 6, *, A. Giangrande 3 , F. Badalamenti 2 , F. Micheli 4 , K. J. Kroeker 5 Stazione Zoologica Anton Dohrn - Integrative Marine Ecology, Villa Dohrn-Benthic Ecology Center, 80077 Ischia, Napoli, Italy Laboratory of Marine Ecology - IAMC - CNR, 91014 Castellammare del Golfo, Italy University of Salento, DiSTeBA, 73100 Lecce, Italy Hopkins Marine Station, Stanford University, Pacific Grove, CA 93950, USA University of California at Santa Cruz, Santa Cruz, CA 95064, USA Present address: Stazione Zoologica Anton Dohrn, 80121 Napoli, Italy ABSTRACT: We report on fine taxonomic and functional analyses of polychaetes associated with rocky reefs along a gradient of ocean acidification (OA) at the volcanic CO 2 vent system off the Castello Aragonese (Ischia Island, Italy). Percent cover of algae and sessile invertebrates (a deter- minant of polychaete distribution) was classified into functional groups to disentangle the direct effects of low pH on polychaete abundance from the indirect effects of pH on habitat and other species associations. A total of 6459 polychaete specimens belonging to 83 taxa were collected. Polychaete species richness and abundance dramatically dropped under the extreme low pH con- ditions due to the disappearance of both calcifying and non-calcifying species. Differences in dis- tribution patterns indicate that the decreasing pH modified the structure and biological traits of polychaete assemblages independent of changes in habitat. A detailed taxonomic analysis high- lighted species-specific responses to OA, with closely related species having opposing responses to decreasing pH. This resulted in an increase in the abundance of filter feeders and herbivores with decreasing pH, while sessile polychaetes disappeared in the extreme low pH zones, and were replaced by discretely motile forms. Reproductive traits of the polychaete assemblages changed as well, with brooding species dominating the most acidified zones. The few taxa that were abundant in extreme low pH conditions showed high tolerance to OA (e.g. Amphiglena mediterranea, Syllis prolifera, Platynereis cf. dumerilii, Parafabricia mazzellae, Brifacia aragonen- sis), and are promising models for further studies on the responses of benthic organisms to the effects of reduced pH. KEY WORDS: Annelida · Algal cover · Ocean acidification · Hard bottoms · pH gradient · Covariation · Mediterranean Sea · Functional trait analysis Resale or republication not permitted without written consent of the publisher Increased anthropogenic CO 2 emissions are pre- dicted to be among the major drivers of global change in the coming century in both terrestrial and marine ecosystems (Gattuso & Buddemeier 2000, IPCC 2014). Large among-species variation in bio- logical responses to CO 2 -induced ocean acidification (OA) is evident in the literature, but it is biased towards calcifying organisms (Ries et al. 2009, Kroeker et al. 2010, 2013a), with most available data derived from laboratory or mesocosm studies (Fabry et al. 2008, Feely et al. 2009, Kroeker et al. 2010, 2013a). However, recent studies performed in natu- *Corresponding author: luigi.musco@szn.it © Inter-Research 2016 · www.int-res.com INTRODUCTION