pH Variability Exacerbates Effects of Ocean Acidification on a Caribbean Crustose Coralline Alga
Crustose coralline algae (CCA) are among the most sensitive marine taxa to the pH changes predicted with ocean acidification (OA). However, many CCA exist in habitats where diel cycles in pH can surpass near-future OA projections. The prevailing theory that natural variability increases the toleranc...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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Frontiers Media S.A.
2019-03-01
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| Series: | Frontiers in Marine Science |
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| Online Access: | https://www.frontiersin.org/article/10.3389/fmars.2019.00150/full |
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| author | Maggie D. Johnson Maggie D. Johnson Maggie D. Johnson Lucia M. Rodriguez Bravo Shevonne E. O’Connor Nicholas F. Varley Andrew H. Altieri Andrew H. Altieri |
| author_facet | Maggie D. Johnson Maggie D. Johnson Maggie D. Johnson Lucia M. Rodriguez Bravo Shevonne E. O’Connor Nicholas F. Varley Andrew H. Altieri Andrew H. Altieri |
| author_sort | Maggie D. Johnson |
| collection | DOAJ |
| description | Crustose coralline algae (CCA) are among the most sensitive marine taxa to the pH changes predicted with ocean acidification (OA). However, many CCA exist in habitats where diel cycles in pH can surpass near-future OA projections. The prevailing theory that natural variability increases the tolerance of calcifiers to OA has not been widely tested with tropical CCA. Here, we assess the response of the reef-building species Lithophyllum congestum to stable and variable pH treatments, including an ambient control (amb/stable). The amb/variable treatment simulated an ambient diel cycle in pH (7.65–7.95), OA/stable simulated constant low pH reflecting worst-case year 2100 predictions (7.7), and OA/variable combined diel cycling with lower mean pH (7.45–7.75). We monitored the effects of pH on total calcification rate and photophysiology (maximum quantum yield) over 16 weeks. To assess the potential for acclimatization, we also quantified calcification rates during the first (0–8 weeks), and second (8–16 weeks) halves of the experiment. Calcification rates were lower in all pH treatments relative to ambient controls and photophysiology was unaffected. At the end of the 16-week experiment, total calcification rates were similarly low in the amb/variable and OA/stable treatment (27–29%), whereas rates declined by double in the OA/variable treatment (60%). When comparing the first and second halves of the experiment, there was no acclimatization in stable treatments as calcification rates remained unchanged in both the amb/stable and OA/stable treatments. In contrast, calcification rates deteriorated between periods in the variable treatments: from a 16–47% reduction in the amb/variable treatment to a 49–79% reduction in the OA/variable treatment, relative to controls. Our findings provide compelling evidence that pH variability can heighten CCA sensitivity to reductions in pH. Moreover, the decline in calcification rate over time directly contrasts prevailing theory that variability inherently increases organismal tolerances to low pH, and suggests that mechanisms of tolerance may become limited with increasing time of exposure. The significant role of diel pH cycling in CCA responses to OA indicates that organisms in habitats with diel variability could respond more severely to rapid changes in ocean pH associated with OA than predicted by experiments conducted under static conditions. |
| first_indexed | 2024-12-11T22:15:01Z |
| format | Article |
| id | doaj.art-f355646f5cb540bd945dc2c8c54cee5e |
| institution | Directory Open Access Journal |
| issn | 2296-7745 |
| language | English |
| last_indexed | 2024-12-11T22:15:01Z |
| publishDate | 2019-03-01 |
| publisher | Frontiers Media S.A. |
| record_format | Article |
| series | Frontiers in Marine Science |
| spelling | doaj.art-f355646f5cb540bd945dc2c8c54cee5e2022-12-22T00:48:38ZengFrontiers Media S.A.Frontiers in Marine Science2296-77452019-03-01610.3389/fmars.2019.00150437313pH Variability Exacerbates Effects of Ocean Acidification on a Caribbean Crustose Coralline AlgaMaggie D. Johnson0Maggie D. Johnson1Maggie D. Johnson2Lucia M. Rodriguez Bravo3Shevonne E. O’Connor4Nicholas F. Varley5Andrew H. Altieri6Andrew H. Altieri7Smithsonian Tropical Research Institute, Panama City, PanamaSmithsonian Marine Station, Fort Pierce, FL, United StatesTennenbaum Marine Observatories Network, Smithsonian Institution, Edgewater, MD, United StatesSmithsonian Tropical Research Institute, Panama City, PanamaMount Holyoke College, South Hadley, MA, United StatesDepartment of the Geophysical Sciences, University of Chicago, Chicago, IL, United StatesSmithsonian Tropical Research Institute, Panama City, PanamaDepartment of Environmental Engineering Sciences, University of Florida, Gainesville, FL, United StatesCrustose coralline algae (CCA) are among the most sensitive marine taxa to the pH changes predicted with ocean acidification (OA). However, many CCA exist in habitats where diel cycles in pH can surpass near-future OA projections. The prevailing theory that natural variability increases the tolerance of calcifiers to OA has not been widely tested with tropical CCA. Here, we assess the response of the reef-building species Lithophyllum congestum to stable and variable pH treatments, including an ambient control (amb/stable). The amb/variable treatment simulated an ambient diel cycle in pH (7.65–7.95), OA/stable simulated constant low pH reflecting worst-case year 2100 predictions (7.7), and OA/variable combined diel cycling with lower mean pH (7.45–7.75). We monitored the effects of pH on total calcification rate and photophysiology (maximum quantum yield) over 16 weeks. To assess the potential for acclimatization, we also quantified calcification rates during the first (0–8 weeks), and second (8–16 weeks) halves of the experiment. Calcification rates were lower in all pH treatments relative to ambient controls and photophysiology was unaffected. At the end of the 16-week experiment, total calcification rates were similarly low in the amb/variable and OA/stable treatment (27–29%), whereas rates declined by double in the OA/variable treatment (60%). When comparing the first and second halves of the experiment, there was no acclimatization in stable treatments as calcification rates remained unchanged in both the amb/stable and OA/stable treatments. In contrast, calcification rates deteriorated between periods in the variable treatments: from a 16–47% reduction in the amb/variable treatment to a 49–79% reduction in the OA/variable treatment, relative to controls. Our findings provide compelling evidence that pH variability can heighten CCA sensitivity to reductions in pH. Moreover, the decline in calcification rate over time directly contrasts prevailing theory that variability inherently increases organismal tolerances to low pH, and suggests that mechanisms of tolerance may become limited with increasing time of exposure. The significant role of diel pH cycling in CCA responses to OA indicates that organisms in habitats with diel variability could respond more severely to rapid changes in ocean pH associated with OA than predicted by experiments conducted under static conditions.https://www.frontiersin.org/article/10.3389/fmars.2019.00150/fullcalcificationdiel variabilityglobal changeLithophyllum congestumpHphotophysiology |
| spellingShingle | Maggie D. Johnson Maggie D. Johnson Maggie D. Johnson Lucia M. Rodriguez Bravo Shevonne E. O’Connor Nicholas F. Varley Andrew H. Altieri Andrew H. Altieri pH Variability Exacerbates Effects of Ocean Acidification on a Caribbean Crustose Coralline Alga Frontiers in Marine Science calcification diel variability global change Lithophyllum congestum pH photophysiology |
| title | pH Variability Exacerbates Effects of Ocean Acidification on a Caribbean Crustose Coralline Alga |
| title_full | pH Variability Exacerbates Effects of Ocean Acidification on a Caribbean Crustose Coralline Alga |
| title_fullStr | pH Variability Exacerbates Effects of Ocean Acidification on a Caribbean Crustose Coralline Alga |
| title_full_unstemmed | pH Variability Exacerbates Effects of Ocean Acidification on a Caribbean Crustose Coralline Alga |
| title_short | pH Variability Exacerbates Effects of Ocean Acidification on a Caribbean Crustose Coralline Alga |
| title_sort | ph variability exacerbates effects of ocean acidification on a caribbean crustose coralline alga |
| topic | calcification diel variability global change Lithophyllum congestum pH photophysiology |
| url | https://www.frontiersin.org/article/10.3389/fmars.2019.00150/full |
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