Combined effects of temperature and CO2

I Bartsch, MdY Sarker, M Teegen, M Babuder, J-M Seliger, M Olischläger, L Gutow, C Wiencke

Alfred Wegener Institute für Polar and Marine Research - www.awi.de – BIOACID Meeting Kiel l6.-7.11. 2012

Combined effects of temperature and CO ₂ on the growth performance of three intertidal red

macroalgae (Rhodophyta)

Theme 4: Species interactions and community structure in a changing ocean Project 4.1: OA impacts on interactions in and structure of benthic communities

Sub-Project 4.1.1 Effects of ocean acidification on trophic interactions in coastal seaweed and seagrass ecosystems

Summary

Hypothesis

Response pattern

Methods: We investigated growth of three intertidal red algae (Mastocarpus stellatus – high to mid intertidal, Chondrus crispus – mid to low intertidal, Palmaria palmata – low intertidal to subtidal) in pertubation experiments (N=5-6) (Fig 1) during 9-18 days at different CO₂ target concentrations (280 / 700 or 800 / 1200 ppm) and optimal vs. suboptimal growth temperatures. The experiments were performed under saturating light conditions for growth.

Fig 1

Most marine macroalgae possess carbon concentrating mechanisms (CCMs). The CCM performance probably influences the relative sensitivity of the species to CO₂. Published data suggest that the CCM activity changes with habitats and taxonomic classes^1-3. Furthermore, it has been discussed that elevated CO₂ may act through a release of energy saved from reduced CCM activity. As our experimental material possesses major differences in their CCM performance acc. to published evidence^1-3 , we hypothesized (1) that growth increments at elevated CO₂ are species-specific and (2) that the energetic benefit induced by a better CO₂ supply will become more pronounced under sub-optimal growth conditions but again with differences between species.

Growth response of benthic red algae to CO

is species specific: the three investigated species which grow along an intertidal shore gradient, represent three different CO

response types:

• Mastocarpus is insensitive towards CO

variations irrespective of temperature

• Chondrus ameliorates its performance under sub-optimum temperature conditions only

• Palmaria generally benefits from enhanced CO

but to a varying degree depending on the temperature

Results

Optimum 15 °C

Sub-Optimum 25 °C

Mastocarpus stellatus

Chondrus crispus

Palmaria palmata

Optimum 15 °C

Sub-Optimum 24 °C

Sub-Optimum 2 °C

Optimum 8 °C

10 °C 18 °C

pCO₂

Low medium high

Growth

Data from: Seliger 2012

Sarker et al 2012, Bot. Mar. , in press, modified

Data from: Teegen 2011 Data from: Babuder 2012

Data from: Teegen 2011 Fortes and Lüning 1980. Helg. Meeresunters 34: 15-29

Data from: Seliger 2012

Different heights of points represent

significant growth increase or decrease (References: 1:Giordano and Maberly 1989, 2: Murru and Sandgren 2004, 3: Moulin et al. 2011).

Red circles:

Temperatures tested in CO₂ pertubation experiments