1. Determining the impact of future climate change on ecologically important macroalgae Charlie M. Phelps *, Mary C. Boyce #, Megan J. Huggett *# *Centre for Marine Ecosystem Research, Edith Cowan University # Centre for Ecosystem Management, Edith Cowan University

2. Background Macroalgae are 3D habitat forming primary producers Herbivores have close ties with the algae, inhabiting, consuming and building nests within their host. http://antartica.uab.edu

3. Ocean conditions: Current - pCO 2 approx 394 ppm - pH approx 8.1 - mean summer temp approx. 20.5⁰C Predicted (yr. 2100) - pCO 2 approx 1000 ppm - pH approx 7.6 - temp approx 25.5⁰C Background wikipedia.org Source: M Huggett

4. The impact of climate change on macroalgae Shifts in habitat assemblages from temperate to tropical Source: Wernberg et. al. (2012)

5. Determine how increased temperature and decreased pH affects the performance of Ecklonia radiata and Sargassum sp. in terms of frond toughness, growth, photosynthetic rate and nutrient content; Determine if the feeding rates of mesograzers are impacted by algae that have been subjected to increased temperature and lowered pH conditions Aims

6. Study Species Two brown algal species - Sargassum and the kelp Ecklonia radiata Amphipod - Allorchestes compressa Gastropod – Family Trochidae Source : activeoceans.wordpress.com Source: Dean Janiak Photo: Gary Poore, Museum of Victoria

7. Methods Collection of species Acclimatise 48 hours 4 treatments 5 replicates per treatment (20 algae) Treatment period 14 days Increased temp 25.5 °C pH 8.1 Increased temp & Decreased pH 25.5 °C pH 7.6 Decreased pH 20.5 °C pH 7.6 Ambient 20.5 °C pH 8.1 Sargassum sp.E. radiata

8. Growth Bleaching Dark – adapted yield Blade toughness C:N ratios Plant Performance answermeup.com zhenglik.blogspot.com

9. Growth Growth occurs in the apical tips in Sargassum and in the base fronds in E. radiata Two different methods required : - Total length measurements (Sargassum) - Hole punch method (E. radiata) Source:Mann & Kirkman (1981) Total Growth Total Length

10. Growth E. radiata p = 0.093 Sargassum sp. p = 0.167

11. Bleaching Triggered by increases in temperature and/or UV radiation Daily observations White background used as standard Coverage and severity observations taken as percentage

12. Bleaching AB Sargassum sp. p = 0.035 E. radiata p = 0.282

13. Quantum Efficiency Specimens were dark adapted for 15 minutes to obtain Fv/Fm yields. Measurements taken at three stages : - immediately post collection - prior to initiation of treatments (Day 1) - post treatment period (Day 14) Source: Gina Mohammed / P&M Technologies

14. Quantum Efficiency Sargassum sp. p = <0.001 E. radiata p = 0.101

15. Blade Toughness In increased CO 2 conditions, a higher allocation of carbon to structural carbohydrates occurs Increasing blade toughness New growth blades were pierced with a custom made penetrometer

16. Blade Toughness AB A Sargassum sp. p = 0.19 E. radiata p = 0.023

17. Fresh Feeding Assay No choice feeding assay Herbivores were offered a pieces of fresh new growth blade Feeding occurred over 36 hours

18. Fresh Feeding Assay Sargassum sp. A.compressor p= 0.83 Trochidae p = 0.578 E. radiata A.compressor p= 0.093 Trochidae p = 0.017 A

19. Summary E.radiata was significantly tougher in the decreased ph/increased temp treatment and consumed more by the Trochidae Sargassum sp. bleached at higher levels in increased temp and showed a lower quantum efficiency than ambient conditions

20. Thank you Kabq.org