Physiological changes in crustose coralline algae alter competitive interactions in response to acidification

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1 Physiological changes in crustose coralline algae alter competitive interactions in response to acidification Sophie J. McCoy, Robert T. Paine, Catherine A. Pfister, and J.Timothy Wootton Third International Symposium on the Ocean in a High-CO2 World 24 September, 22

2 Environment affects species distributions effects on physical resources & physiological needs of organisms mediation of species interactions community composition macro scale tropical intertidal temperate intertidal

3 Environment affects species zonation effects on physical resources & physiological needs of organisms mediation of species interactions community composition local scale

4 Ocean acidification as major environmental change..8 Concentration (mol/kg) CO 2 HCO 3 - CO ph decreasing ph CO2 (aq)+ H2O H2CO3 (aq) H + (aq) + HCO3 - (aq) 2H + (aq) + CO3 2- (aq)

5 Inorganic carbon nutrients HCO3 - = bicarbonate used by most aquatic plants/algae for photosynthesis CO3 2- = carbonate used to make skeletons and shells of many marine organisms (e.g., bivalves, corals, sponges)

6 Context for change at Tatoosh Island, WA ph Wootton et al. 28; Wootton et al. in prep

7 Ecological baseline at Tatoosh Island Species dynamics, interactions, and natural history are well-studied

8 Ecological baseline at Tatoosh Island ECOLOGICAL DETERMINISM IN THE COMPETITION FOR SPACE The Robert H. MacArthur Award Lecture Presented on 9 August 983 Grand Forks, North Dakota by R. T. PAINE Department of Zoology, University of Washington, Seattle, Washington 9895 USA 4--,.. '', Paine 984

9 Coralline red algae Maerls and Rhodoliths Corallina Articulated forms Lithophyllum dentatum Phymatolithon calcareum Bossiella P. whidbeyense Encrusting forms Pseudolithophyllum muricatum Lithothamnion phymatodeum HCO3 - = bicarbonate used by most aquatic plants/algae for photosynthesis CO3 2- = carbonate used to make skeletons and shells of many marine organisms (e.g., bivalves, corals, sponges)

10 Coralline red algae (Rhodophyta, Corallinales) use bicarbonate (HCO3 - ) for photosynthesis use carbonate (CO3 2- ) to make skeleton Smith and Roth 979 Bossiella(orbigniana( Growth (Calcification, ct / min tip hr) decreasing [CO3 2- ] becomes limiting I_ 8 ~CZ T QL T H z o U_ 8 6 6O 4 4O 2 _.. 2 [&26] T [o 39]~ [ i,] /I ~.~ (g) ~[o.o4] / ) ~zo) l t(4) III I (4) (6) (6) (3) (6) (5) (6) I I I I J I ph decreasing ph ph increased growth caused by increasing [HCO3 - ]

11 Do we observe ecological responses within or among coralline algae to ocean acidification at Tatoosh Island? Use observed community response to identify important physiological responses that mediate ecological processes

12 Interactions - Herbivore-mediated competitive hierarchy grazers absent Pseudolithophyllum muricatum Lithothamnion phymatodeum Pseudolithophyllum whidbeyense Lithophyllum impressum Bossiella & Corallina sp. Paine 984

13 Position on the hierarchy PM slow growth Fast lateral growth = able to grow faster under low grazing pressure LP PW med/fast growth fast growth LI med/slow growth Art fast growth rapid colonizer

14 Position on the hierarchy PM slow growth Thick, elevated edge = delay overgrowth by another species LP med/fast growth Scenario PW fast growth species A Scenario 2 species B LI med/slow growth species A species B It is harder for species B to win in Scenario 2 because it must travel farther to achieve overgrowth Art fast growth rapid colonizer

15 Growth strategy trade-offs PM very thick thallus elevated edge slow growth Fast lateral growth and thick edge LP med thallus thin edge protuberances med/fast growth Overall thickness = better equipped to resist grazing damage PW thin thallus thin edge fast growth LI med/thick thallus med edge med/slow growth Art very thin thallus articulated segments fast growth rapid colonizer

16 Grazers Katharina tunicata Tonicella lokii crusts must be thickly calcified to withstand heavy grazing Lottia spp. Strongylocentrotus purpuratus Acmea mitra Mopalia ciliata Johnson and Mann 986; Paine 984; Steneck and Paine 986; Steneck, Hacker and Dethier 99

17 Interactions - Herbivore-mediated competitive hierarchy grazers absent Pseudolithophyllum muricatum Lithothamnion phymatodeum Pseudolithophyllum whidbeyense Lithophyllum impressum Bossiella & Corallina sp. Paine 984

18 Interactions - Herbivore-mediated competitive hierarchy low grazer abundance P. muricatum L. phymatodeum P. whidbeyense L. impressum Paine 984 Bossiella & Corallina sp.

19 Interactions - Herbivore-mediated competitive hierarchy high grazer abundance P. muricatum L. phymatodeum L. impressum P. whidbeyense Bossiella & Corallina sp. Paine 984

20 Overgrowth interactions experimental setup Hedophyllum Cove 2-23 grazers present x3 grazers removed x3 2 replicates / plot 2 July 2 27 Aug 2

21 Results from competitive bouts Competitive ability index ranges from - CAI = # wins # wins + # losses Losers (Overgrown) 2-22 grazers removed Winners PM LP PW LI Art PM 2 4 LP 6 2 PW LI July 2 27 Aug 2 Art 7 2 5

22 Altered competitive interactions archival data modern data with grazers PM LP PW LI Art McCoy et al. in prep

23 Altered competitive interactions archival data modern data with grazers no grazers PM LP PW LI Art McCoy et al. in prep

24 Altered competitive interactions archival data modern data with grazers no grazers PM LP PW LI Art McCoy et al. in prep

25 What mechanisms might be responsible for these observed changes in species interactions?

26 Effect of morphology? archival data modern data with grazers no grazers PM LP PW LI Art very thick thallus elevated edge med thallus thin edge protuberances thin thallus thin edge med/thick thallus med edge very thin basal thallus, articulated segments McCoy et al. in prep

27 Effect of morphology? Reduced competitive ability is associated with traits requiring more calcified tissue: ) thicker algal crust 2) thick, elevated growing edge Ocean acidification reduces CO3 2- available for calcification.

28 Effect of morphology? Reduced competitive ability is associated with traits requiring more calcified tissue: ) thicker algal crust 2) thick, elevated growing edge Ocean acidification reduces CO3 2- available for calcification. Thus, in P. muricatum we might expect: ) decreased calcified tissue density 2) decreased edge thickness

29 Testing hypotheses in P. muricatum SEM imaging ) % calcified tissue (by area) 2) thickness at growing edge growing edge of crust {

30 % calcified tissue in P. muricatum a.7 NS.65 b Calcite density Tissue density n = 6 n = 6 c(,.8) McCoy in prep

31 Thallus thickness, µm Thickness at growing edge in P. muricatum Thallus thickness, um p <. p=2.36e Distance from growing edge, µm Distance from growing edge, um McCoy in prep

32 Thickness at growing edge in P. muricatum McCoy in prep

33 Conclusions Competitive interactions show response to OA in the field when compared to historical baselines. - Former competitive dominant now wins < 5% competitive bouts - Physiological response to OA has direct effect on species interactions in nature Implications for intertidal biodiversity - Coralline algae important to the recruitment of seagrasses and many invertebrates - Overgrowth boundaries provide substrate irregularity for attachment

34 Acknowledgements Co-authors: Bob Paine, Cathy Pfister, Tim Wootton Makah Tribe for access to field sites Qiti Guo and the Chicago Materials Research Center for assistance with the SEM Pfister-Wootton Lab Orissa Moulton and Pete Zaykoski for help with grazer removals Funding: Department of Defense NDSEG Fellowship NSF Graduate Research Fellowship ARCS Foundation NSF Doctoral Dissertation Improvement Grant Ecology GAANN The University of Chicago Hinds Fund Geological Society of America Phycological Society of America

35 Grazer abundance Abundance Katharina Abundance Tunicata / m Site - Hedophyllum Cove Site 2 - Simon's Landing

36 Altered competitive interactions - 2 sites with grazers no grazers archival data modern data modern data, Simon s Landing PM LP PW LI Art McCoy et al. in prep

37 δ 3 C at Tatoosh Island context for ph trend AD decline.53 decline closer look at / year δ 3 C ( ) Pfister et al. 2

38 SST at Tatoosh Island 8 Cape Elizabeth Tatoosh Island 6 ElizTempMonth[, 3] SST (ºC) ElizTempDate