Differential Responses of Calcifying and Non-Calcifying Epibionts of a Brown Macroalga to Present-Day and Future Upwelling pCO2.

Saderne, Vincent and Wahl, Martin (2013) Differential Responses of Calcifying and Non-Calcifying Epibionts of a Brown Macroalga to Present-Day and Future Upwelling pCO2. Open Access PLoS ONE, 8 (7). e70455. DOI 10.1371/journal.pone.0070455.

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Abstract

Seaweeds are key species of the Baltic Sea benthic ecosystems. They are the substratum of numerous fouling epibionts like bryozoans and tubeworms. Several of these epibionts bear calcified structures and could be impacted by the high pCO2 events of the late summer upwellings in the Baltic nearshores. Those events are expected to increase in strength and duration with global change and ocean acidification. If calcifying epibionts are impacted by transient acidification as driven by upwelling events, their increasing prevalence could cause a shift of the fouling communities toward fleshy species. The aim of the present study was to test the sensitivity of selected seaweed macrofoulers to transient elevation of pCO2 in their natural microenvironment, i.e. the boundary layer covering the thallus surface of brown seaweeds. Fragments of the macroalga Fucus serratus bearing an epibiotic community composed of the calcifiers Spirorbis spirorbis (Annelida) and Electra pilosa (Bryozoa) and the non-calcifier Alcyonidium hirsutum (Bryozoa) were maintained for 30 days under three pCO2 conditions: natural 460±59 µatm, present-day upwelling1193±166 µatm and future upwelling 3150±446 µatm. Only the highest pCO2 caused a significant reduction of growth rates and settlement of S. spirorbis individuals. Additionally, S. spirorbis settled juveniles exhibited enhanced calcification of 40% during daylight hours compared to dark hours, possibly reflecting a day-night alternation of an acidification-modulating effect by algal photosynthesis as opposed to an acidification-enhancing effect of algal respiration. E. pilosa colonies showed significantly increased growth rates at intermediate pCO2 (1193 µatm) but no response to higher pCO2. No effect of acidification on A. hirsutum colonies growth rates was observed. The results suggest a remarkable resistance of the algal macro-epibionts to levels of acidification occurring at present day upwellings in the Baltic. Only extreme future upwelling conditions impacted the tubeworm S. spirorbis, but not the bryozoans.

Document Type: Article
Funder compliance: info:eu-repo/grantAgreement/EC/FP7/215157
Additional Information: WOS:000325211000210
Keywords: BRYOZOAN ELECTRA-PILOSA; FUCUS-SERRATUS L; CO2-DRIVEN OCEAN ACIDIFICATION; MARINE BRYOZOAN; BALTIC SEA; MEMBRANIPORA-MEMBRANACEA; POLYCHAETA-SERPULIDAE; SPIRORBIS POLYCHAETA; ENCRUSTING BRYOZOANS; MACROCYSTIS-PYRIFERA
Research affiliation: OceanRep > The Future Ocean - Cluster of Excellence > FO-R08
OceanRep > The Future Ocean - Cluster of Excellence
Kiel University
OceanRep > GEOMAR > FB3 Marine Ecology > FB3-EOE-B Experimental Ecology - Benthic Ecology
Refereed: Yes
Open Access Journal?: Yes
DOI etc.: 10.1371/journal.pone.0070455
ISSN: 1932-6203
Projects: CalMarO, Future Ocean
Date Deposited: 24 Jul 2013 08:30
Last Modified: 22 Jun 2017 07:39
URI: http://oceanrep.geomar.de/id/eprint/21846

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