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Fernández PA, Amsler CD, Hurd CL, Díaz PA, Gaitán-Espitia JD, Macaya EC, Schmider-Martínez A, Garrido I, Murúa P, Buschmann AH. Diverse inorganic carbon uptake strategies in Antarctic seaweeds: Revealing species-specific responses and implications for Ocean Acidification. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 945:174006. [PMID: 38889822 DOI: 10.1016/j.scitotenv.2024.174006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2024] [Revised: 05/09/2024] [Accepted: 06/13/2024] [Indexed: 06/20/2024]
Abstract
Seaweeds are important components of coastal benthic ecosystems along the Western Antarctic Peninsula (WAP), providing refuge, food, and habitat for numerous associated species. Despite their crucial role, the WAP is among the regions most affected by global climate change, potentially impacting the ecology and physiology of seaweeds. Elevated atmospheric CO2 concentrations have led to increased dissolved inorganic carbon (Ci) with consequent declines in oceanic pH and alterations in seawater carbonate chemistry, known as Ocean Acidification (OA). Seaweeds possess diverse strategies for Ci uptake, including CO2 concentrating mechanisms (CCMs), which may distinctly respond to changes in Ci concentrations. Conversely, some seaweeds do not operate CCMs (non-CCM species) and rely solely on CO2. Nevertheless, our understanding of the status and functionality of Ci uptake strategies in Antarctic seaweeds remains limited. Here, we investigated the Ci uptake strategies of seaweeds along a depth gradient in the WAP. Carbon isotope signatures (δ13C) and pH drift assays were used as indicators of the presence or absence of CCMs. Our results reveal variability in CCM occurrence among algal phyla and depths ranging from 0 to 20 m. However, this response was species specific. Among red seaweeds, the majority relied solely on CO2 as an exogenous Ci source, with a high percentage of non-CCM species. Green seaweeds exhibited depth-dependent variations in CCM status, with the proportion of non-CCM species increasing at greater depths. Conversely, brown seaweeds exhibited a higher prevalence of CCM species, even in deep waters, indicating the use of CO2 and HCO3-. Our results are similar to those observed in temperate and tropical regions, indicating that the potential impacts of OA on Antarctic seaweeds will be species specific. Additionally, OA may potentially increase the abundance of non-CCM species relative to those with CCMs.
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Affiliation(s)
- Pamela A Fernández
- Centro i∼mar, CeBiB & MASH, Universidad de Los Lagos, Camino a Chinquihue km6, Puerto Montt 580000, Chile.
| | - Charles D Amsler
- University of Alabama at Birmingham, Department of Biology, Birmingham, AL 35233, USA
| | - Catriona L Hurd
- Institute for marine and Antarctic Studies (IMAS), University of Tasmania, TAS 7001, Australia
| | - Patricio A Díaz
- Centro i∼mar, Universidad de Los Lagos, Camino a Chinquihue km6, Puerto Montt 580000, Chile
| | - Juan Diego Gaitán-Espitia
- The Swire Institute of Marine Science, School of Biological Sciences, The University of Hong Kong, Pok Fu Lam Road, Hong Kong
| | - Erasmo C Macaya
- Departamento de Oceanografía, Universidad de Concepción, Concepción, Chile; Centro FONDAP de Investigación Dinámica de Ecosistemas Marinos de Altas Latitudes (IDEAL), Valdivia 5090000, Chile
| | | | - Ignacio Garrido
- Centro FONDAP de Investigación Dinámica de Ecosistemas Marinos de Altas Latitudes (IDEAL), Valdivia 5090000, Chile; Laboratorio Costero de Recursos Acuáticos de Calfuco (LCRAC), Instituto Ciencias Marinas y Limnológicas (ICML), Facultad de Ciencias, Universidad Austral de Chile, Valdivia 5110566, Chile; Department of Biology and Québec-Océan, Laval University, Québec, QC G1V 0A6, Canada
| | - Pedro Murúa
- Laboratorio de Macroalgas y Ficopatologia, Instituto de Acuicultura, Universidad Austral de Chile, Sede Puerto Montt, Puerto Montt, Chile
| | - Alejandro H Buschmann
- Centro i∼mar, CeBiB & MASH, Universidad de Los Lagos, Camino a Chinquihue km6, Puerto Montt 580000, Chile
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Capó-Bauçà S, Iñiguez C, Galmés J. The diversity and coevolution of Rubisco and CO 2 concentrating mechanisms in marine macrophytes. THE NEW PHYTOLOGIST 2024; 241:2353-2365. [PMID: 38197185 DOI: 10.1111/nph.19528] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2023] [Accepted: 12/15/2023] [Indexed: 01/11/2024]
Abstract
The kinetic properties of Rubisco, the most important carbon-fixing enzyme, have been assessed in a small fraction of the estimated existing biodiversity of photosynthetic organisms. Until recently, one of the most significant gaps of knowledge in Rubisco kinetics was marine macrophytes, an ecologically relevant group including brown (Ochrophyta), red (Rhodophyta) and green (Chlorophyta) macroalgae and seagrasses (Streptophyta). These organisms express various Rubisco types and predominantly possess CO2 -concentrating mechanisms (CCMs), which facilitate the use of bicarbonate for photosynthesis. Since bicarbonate is the most abundant form of dissolved inorganic carbon in seawater, CCMs allow marine macrophytes to overcome the slow gas diffusion and low CO2 availability in this environment. The present review aims to compile and integrate recent findings on the biochemical diversity of Rubisco and CCMs in the main groups of marine macrophytes. The Rubisco kinetic data provided demonstrate a more relaxed relationship among catalytic parameters than previously reported, uncovering a variability in Rubisco catalysis that has been hidden by a bias in the literature towards terrestrial vascular plants. The compiled data indicate the existence of convergent evolution between Rubisco and biophysical CCMs across the polyphyletic groups of marine macrophytes and suggest a potential role for oxygen in shaping such relationship.
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Affiliation(s)
- Sebastià Capó-Bauçà
- Research Group on Plant Biology under Mediterranean Conditions, Universitat de les Illes Balears-INAGEA, 07122, Palma, Balearic Islands, Spain
| | - Concepción Iñiguez
- Research Group on Plant Biology under Mediterranean Conditions, Universitat de les Illes Balears-INAGEA, 07122, Palma, Balearic Islands, Spain
- Department of Ecology, Faculty of Sciences, University of Malaga, Boulevard Louis Pasteur s/n, 29010, Málaga, Spain
| | - Jeroni Galmés
- Research Group on Plant Biology under Mediterranean Conditions, Universitat de les Illes Balears-INAGEA, 07122, Palma, Balearic Islands, Spain
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3
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Page HN, McCoy S, Spencer RGM, Burnham KA, Hewett C, Johnson M. Effects of ocean acidification on growth and photophysiology of two tropical reef macroalgae. PLoS One 2023; 18:e0286661. [PMID: 37976304 PMCID: PMC10655979 DOI: 10.1371/journal.pone.0286661] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2022] [Accepted: 05/21/2023] [Indexed: 11/19/2023] Open
Abstract
Macroalgae can modify coral reef community structure and ecosystem function through a variety of mechanisms, including mediation of biogeochemistry through photosynthesis and the associated production of dissolved organic carbon (DOC). Ocean acidification has the potential to fuel macroalgal growth and photosynthesis and alter DOC production, but responses across taxa and regions are widely varied and difficult to predict. Focusing on algal taxa from two different functional groups on Caribbean coral reefs, we exposed fleshy (Dictyota spp.) and calcifying (Halimeda tuna) macroalgae to ambient and low seawater pH for 25 days in an outdoor experimental system in the Florida Keys. We quantified algal growth, calcification, photophysiology, and DOC production across pH treatments. We observed no significant differences in the growth or photophysiology of either species between treatments, except for lower chlorophyll b concentrations in Dictyota spp. in response to low pH. We were unable to quantify changes in DOC production. The tolerance of Dictyota and Halimeda to near-future seawater carbonate chemistry and stability of photophysiology, suggests that acidification alone is unlikely to change biogeochemical processes associated with algal photosynthesis in these species. Additional research is needed to fully understand how taxa from these functional groups sourced from a wide range of environmental conditions regulate photosynthesis (via carbon uptake strategies) and how this impacts their DOC production. Understanding these species-specific responses to future acidification will allow us to more accurately model and predict the indirect impacts of macroalgae on coral health and reef ecosystem processes.
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Affiliation(s)
- Heather N. Page
- Elizabeth Moore International Center for Coral Reef Research and Restoration, Mote Marine Laboratory, Summerland Key, FL, United States of America
- Sea Education Association, Woods Hole, MA, United States of America
| | - Sophie McCoy
- University of North Carolina at Chapel Hill, Chapel Hill, NC, United States of America
| | | | - Katherine A. Burnham
- Elizabeth Moore International Center for Coral Reef Research and Restoration, Mote Marine Laboratory, Summerland Key, FL, United States of America
| | - Clay Hewett
- Elizabeth Moore International Center for Coral Reef Research and Restoration, Mote Marine Laboratory, Summerland Key, FL, United States of America
- Jacksonville University, Jacksonville, Fl, United States of America
| | - Maggie Johnson
- Smithsonian Marine Station, Fort Pierce, FL, United States of America
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James RK, Hepburn CD, Pritchard D, Richards DK, Hurd CL. Water motion and pH jointly impact the availability of dissolved inorganic carbon to macroalgae. Sci Rep 2022; 12:21947. [PMID: 36536020 PMCID: PMC9763248 DOI: 10.1038/s41598-022-26517-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Accepted: 12/15/2022] [Indexed: 12/23/2022] Open
Abstract
The supply of dissolved inorganic carbon to seaweeds is a key factor regulating photosynthesis. Thinner diffusive boundary layers at the seaweed surface or greater seawater carbon dioxide (CO2) concentrations increase CO2 supply to the seaweed surface. This may benefit seaweeds by alleviating carbon limitation either via an increased supply of CO2 that is taken up by passive diffusion, or via the down-regulation of active carbon concentrating mechanisms (CCMs) that enable the utilization of the abundant ion bicarbonate (HCO3-). Laboratory experiments showed that a 5 times increase in water motion increases DIC uptake efficiency in both a non-CCM (Hymenena palmata, Rhodophyta) and CCM (Xiphophora gladiata, Phaeophyceae) seaweed. In a field survey, brown and green seaweeds with active-CCMs maintained their CCM activity under diverse conditions of water motion. Whereas red seaweeds exhibited flexible photosynthetic rates depending on CO2 availability, and species switched from a non-CCM strategy in wave-exposed sites to an active-CCM strategy in sheltered sites where mass transfer of CO2 would be reduced. 97-99% of the seaweed assemblages at both wave-sheltered and exposed sites consisted of active-CCM species. Variable sensitivities to external CO2 would drive different responses to increasing CO2 availability, although dominance of the CCM-strategy suggests this will have minimal impact within shallow seaweed assemblages.
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Affiliation(s)
- Rebecca K. James
- grid.29980.3a0000 0004 1936 7830Department of Botany, University of Otago, Dunedin, New Zealand ,grid.4989.c0000 0001 2348 0746Department of Geosciences, Environment & Society Department, Université Libre de Bruxelles, Brussels, Belgium
| | - Christopher D. Hepburn
- grid.29980.3a0000 0004 1936 7830Department of Marine Science, University of Otago, Dunedin, New Zealand ,Coastal People Southern Skies Centre of Research Excellence, Dunedin, New Zealand
| | - Daniel Pritchard
- Coastal People Southern Skies Centre of Research Excellence, Dunedin, New Zealand
| | - Derek K. Richards
- grid.29980.3a0000 0004 1936 7830Department of Marine Science, University of Otago, Dunedin, New Zealand
| | - Catriona L. Hurd
- grid.29980.3a0000 0004 1936 7830Department of Botany, University of Otago, Dunedin, New Zealand ,Coastal People Southern Skies Centre of Research Excellence, Dunedin, New Zealand ,grid.1009.80000 0004 1936 826XInstitute for Marine and Antarctic Studies (IMAS), University of Tasmania, Hobart, TAS Australia
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5
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Schlenger AJ, Beas-Luna R, Ambrose RF. Forecasting ocean acidification impacts on kelp forest ecosystems. PLoS One 2021; 16:e0236218. [PMID: 33886569 PMCID: PMC8061940 DOI: 10.1371/journal.pone.0236218] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Accepted: 03/28/2021] [Indexed: 11/19/2022] Open
Abstract
Ocean acidification is one the biggest threats to marine ecosystems worldwide, but its ecosystem wide responses are still poorly understood. This study integrates field and experimental data into a mass balance food web model of a temperate coastal ecosystem to determine the impacts of specific OA forcing mechanisms as well as how they interact with one another. Specifically, we forced a food web model of a kelp forest ecosystem near its southern distribution limit in the California large marine ecosystem to a 0.5 pH drop over the course of 50 years. This study utilizes a modeling approach to determine the impacts of specific OA forcing mechanisms as well as how they interact. Isolating OA impacts on growth (Production), mortality (Other Mortality), and predation interactions (Vulnerability) or combining all three mechanisms together leads to a variety of ecosystem responses, with some taxa increasing in abundance and other decreasing. Results suggest that carbonate mineralizing groups such as coralline algae, abalone, snails, and lobsters display the largest decreases in biomass while macroalgae, urchins, and some larger fish species display the largest increases. Low trophic level groups such as giant kelp and brown algae increase in biomass by 16% and 71%, respectively. Due to the diverse way in which OA stress manifests at both individual and population levels, ecosystem-level effects can vary and display nonlinear patterns. Combined OA forcing leads to initial increases in ecosystem and commercial biomasses followed by a decrease in commercial biomass below initial values over time, while ecosystem biomass remains high. Both biodiversity and average trophic level decrease over time. These projections indicate that the kelp forest community would maintain high productivity with a 0.5 drop in pH, but with a substantially different community structure characterized by lower biodiversity and relatively greater dominance by lower trophic level organisms.
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Affiliation(s)
- Adam J. Schlenger
- Institute of the Environment and Sustainability, University of California Los Angeles, Los Angeles, California, United States of America
| | - Rodrigo Beas-Luna
- Facultad de Ciencias Marinas, Universidad Autónoma de Baja California, Ensenada B.C. Mexico
| | - Richard F. Ambrose
- Institute of the Environment and Sustainability, University of California Los Angeles, Los Angeles, California, United States of America
- Department of Environmental Health Sciences, University of California, Los Angeles, Los Angeles, California, United States of America
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6
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Ji Y, Gao K. Effects of climate change factors on marine macroalgae: A review. ADVANCES IN MARINE BIOLOGY 2020; 88:91-136. [PMID: 34119047 DOI: 10.1016/bs.amb.2020.11.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Marine macroalgae, the main primary producers in coastal waters, play important roles in the fishery industry and global carbon cycles. With progressive ocean global changes, however, they are increasingly exposed to enhanced levels of multiple environmental drivers, such as ocean acidification, warming, heatwaves, UV radiation and deoxygenation. While most macroalgae have developed physiological strategies against variations of these drivers, their eco-physiological responses to each or combinations of the drivers differ spatiotemporally and species-specifically. Many freshwater macroalgae are tolerant of pH drop and its diel fluctuations and capable of acclimating to changes in carbonate chemistry. However, calcifying species, such as coralline algae, are very sensitive to acidification of seawater, which reduces their calcification, and additionally, temperature rise and UV further decrease their physiological performance. Except for these calcifying species, both economically important and harmful macroalgae can benefit from elevated CO2 concentrations and moderate temperature rise, which might be responsible for increasing events of harmful macroalgal blooms including green macroalgal blooms caused by Ulva spp. and golden tides caused by Sargassum spp. Upper intertidal macroalgae, especially those tolerant of dehydration during low tide, increase their photosynthesis under elevated CO2 concentrations during the initial dehydration period, however, these species might be endangered by heatwaves, which can expose them to high temperature levels above their thermal windows' upper limit. On the other hand, since macroalgae are distributed in shallow waters, they are inevitably exposed to solar UV radiation. The effects of UV radiation, depending on weather conditions and species, can be harmful as well as beneficial to many species. Moderate levels of UV-A (315-400nm) can enhance photosynthesis of green, brown and red algae, while UV-B (280-315nm) mainly show inhibitory impacts. Although little has been documented on the combined effects of elevated CO2, temperature or heatwaves with UV radiation, exposures to heatwaves during midday under high levels of UV radiation can be detrimental to most species, especially to their microscopic stages which are less tolerant of climate change induced stress. In parallel, reduced availability of dissolved O2 in coastal water along with eutrophication might favour the macroalgae's carboxylation process by suppressing their oxygenation or photorespiration. In this review, we analyse effects of climate change-relevant drivers individually and/or jointly on different macroalgal groups and different life cycle stages based on the literatures surveyed, and provide perspectives for future studies.
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Affiliation(s)
- Yan Ji
- State Key Laboratory of Marine Environmental Science, Xiamen University/College of Ocean and Earth Sciences, Xiamen, China; School of Biological & Chemical Engineering, Qingdao Technical College, Qingdao, China
| | - Kunshan Gao
- State Key Laboratory of Marine Environmental Science, Xiamen University/College of Ocean and Earth Sciences, Xiamen, China; Co-Innovation Center of Jiangsu Marine Bio-industry Technology, Jiangsu Ocean University, Lianyungang, China.
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7
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Petraitis PS, Dudgeon SR. Declines over the last two decades of five intertidal invertebrate species in the western North Atlantic. Commun Biol 2020; 3:591. [PMID: 33082487 PMCID: PMC7576203 DOI: 10.1038/s42003-020-01326-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Accepted: 09/29/2020] [Indexed: 11/09/2022] Open
Abstract
Climate change has already altered the environmental conditions of the world's oceans. Here we report declines in gastropod abundances and recruitment of mussels (Mytilus edulis) and barnacles (Semibalanus balanoides) over the last two decades that are correlated with changes in temperature and ocean conditions. Mussel recruitment is declining by 15.7% per year, barnacle recruitment by 5.0% per year, and abundances of three common gastropods are declining by an average of 3.1% per year (Testudinalia testudinalis, Littorina littorea, and Nucella lapillus). The declines in mussels and the common periwinkle (L. littorea) are correlated with warming sea temperatures and the declines in T. testudinalis and N. lapillus are correlated with aragonite saturation state, which affects rates of shell calcification. These species are common on shores throughout the North Atlantic and their loss is likely to lead to simplification of an important food web on rocky shores.
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Affiliation(s)
- Peter S Petraitis
- Department of Biology, University of Pennsylvania, Philadelphia, PA, 19104-6018, USA.
| | - S R Dudgeon
- Department of Biology, California State University, Northridge, CA, 91330-8303, USA.
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Britton D, Schmid M, Noisette F, Havenhand JN, Paine ER, McGraw CM, Revill AT, Virtue P, Nichols PD, Mundy CN, Hurd CL. Adjustments in fatty acid composition is a mechanism that can explain resilience to marine heatwaves and future ocean conditions in the habitat-forming seaweed Phyllospora comosa (Labillardière) C.Agardh. GLOBAL CHANGE BIOLOGY 2020; 26:3512-3524. [PMID: 32105368 DOI: 10.1111/gcb.15052] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Accepted: 02/10/2020] [Indexed: 06/10/2023]
Abstract
Marine heatwaves are extreme events that can have profound and lasting impacts on marine species. Field observations have shown seaweeds to be highly susceptible to marine heatwaves, but the physiological drivers of this susceptibility are poorly understood. Furthermore, the effects of marine heatwaves in conjunction with ocean warming and acidification are yet to be investigated. To address this knowledge gap, we conducted a laboratory culture experiment in which we tested the growth and physiological responses of Phyllospora comosa juveniles from the southern extent of its range (43-31°S) to marine heatwaves, ocean warming and acidification. We used a 'collapsed factorial design' in which marine heatwaves were superimposed on current (today's pH and temperature) and future (pH and temperature projected by 2100) ocean conditions. Responses were tested both during the heatwaves, and after a 7-day recovery period. Heatwaves reduced net photosynthetic rates in both current and future conditions, while respiration rates were elevated under heatwaves in the current conditions only. Following the recovery period, there was little evidence of heatwaves having lasting negative effects on growth, photosynthesis or respiration. Exposure to heatwaves, future ocean conditions or both caused an increase in the degree of saturation of fatty acids. This adjustment may have counteracted negative effects of elevated temperatures by decreasing membrane fluidity, which increases at higher temperatures. Furthermore, P. comosa appeared to down-regulate the energetically expensive carbon dioxide concentrating mechanism in the future conditions with a reduction in δ13 C values detected in these treatments. Any saved energy arising from this down-regulation was not invested in growth and was likely invested in the adjustment of fatty acid composition. This adjustment is a mechanism by which P. comosa and other seaweeds may tolerate the negative effects of ocean warming and marine heatwaves through benefits arising from ocean acidification.
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Affiliation(s)
- Damon Britton
- Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tas., Australia
| | - Matthias Schmid
- Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tas., Australia
| | - Fanny Noisette
- Institut des Sciences de la Mer, Université du Québec à Rimouski, Rimouski, QC, Canada
| | - Jonathan N Havenhand
- Department of Marine Sciences, Tjärnö Marine Laboratory, University of Gothenburg, Strömstad, Sweden
| | - Ellie R Paine
- Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tas., Australia
| | - Christina M McGraw
- Department of Chemistry, NIWA/University of Otago Research Centre for Oceanography, University of Otago, Dunedin, New Zealand
| | | | - Patti Virtue
- Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tas., Australia
- CSIRO Oceans and Atmosphere, Hobart, Tas., Australia
- Antarctic Climate and Ecosystems, Cooperative Research Centre, Hobart, Tas., Australia
| | - Peter D Nichols
- Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tas., Australia
- CSIRO Oceans and Atmosphere, Hobart, Tas., Australia
| | - Craig N Mundy
- Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tas., Australia
| | - Catriona L Hurd
- Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tas., Australia
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9
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Raven JA, Gobler CJ, Hansen PJ. Dynamic CO 2 and pH levels in coastal, estuarine, and inland waters: Theoretical and observed effects on harmful algal blooms. HARMFUL ALGAE 2020; 91:101594. [PMID: 32057340 DOI: 10.1016/j.hal.2019.03.012] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2019] [Accepted: 03/08/2019] [Indexed: 06/10/2023]
Abstract
Rising concentrations of atmospheric CO2 results in higher equilibrium concentrations of dissolved CO2 in natural waters, with corresponding increases in hydrogen ion and bicarbonate concentrations and decreases in hydroxyl ion and carbonate concentrations. Superimposed on these climate change effects is the dynamic nature of carbon cycling in coastal zones, which can lead to seasonal and diel changes in pH and CO2 concentrations that can exceed changes expected for open ocean ecosystems by the end of the century. Among harmful algae, i.e. some species and/or strains of Cyanobacteria, Dinophyceae, Prymnesiophyceae, Bacillariophyceae, and Ulvophyceae, the occurrence of a CO2 concentrating mechanisms (CCMs) is the most frequent mechanism of inorganic carbon acquisition in natural waters in equilibrium with the present atmosphere (400 μmol CO2 mol-1 total gas), with varying phenotypic modification of the CCM. No data on CCMs are available for Raphidophyceae or the brown tide Pelagophyceae. Several HAB species and/or strains respond to increased CO2 concentrations with increases in growth rate and/or cellular toxin content, however, others are unaffected. Beyond the effects of altered C concentrations and speciation on HABs, changes in pH in natural waters are likely to have profound effects on algal physiology. This review outlines the implications of changes in inorganic cycling for HABs in coastal zones, and reviews the knowns and unknowns with regard to how HABs can be expected to ocean acidification. We further point to the large regions of uncertainty with regard to this evolving field.
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Affiliation(s)
- John A Raven
- Division of Plant Sciences, University of Dundee at the James Hutton Institute, Invergowrie, Dundee, DD2 5DA, UK; Climate Change Cluster, University of Technology Sydney, Ultimo, NSW, 2007, Australia; School of Biological Science, University of Western Australia, Crawley, WA, 6009, Australia.
| | - Christopher J Gobler
- School of Marine and Atmospheric Sciences, Stony Brook University, Southampton NY, 11968, USA.
| | - Per Juel Hansen
- University of Copenhagen, Marine Biological Section, Strandpromenaden 5, DK 3000 Helsingør, Denmark
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van der Loos LM, Schmid M, Leal PP, McGraw CM, Britton D, Revill AT, Virtue P, Nichols PD, Hurd CL. Responses of macroalgae to CO 2 enrichment cannot be inferred solely from their inorganic carbon uptake strategy. Ecol Evol 2019; 9:125-140. [PMID: 30680101 PMCID: PMC6342131 DOI: 10.1002/ece3.4679] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2018] [Revised: 10/02/2018] [Accepted: 10/10/2018] [Indexed: 02/03/2023] Open
Abstract
Increased plant biomass is observed in terrestrial systems due to rising levels of atmospheric CO2, but responses of marine macroalgae to CO2 enrichment are unclear. The 200% increase in CO2 by 2100 is predicted to enhance the productivity of fleshy macroalgae that acquire inorganic carbon solely as CO2 (non-carbon dioxide-concentrating mechanism [CCM] species-i.e., species without a carbon dioxide-concentrating mechanism), whereas those that additionally uptake bicarbonate (CCM species) are predicted to respond neutrally or positively depending on their affinity for bicarbonate. Previous studies, however, show that fleshy macroalgae exhibit a broad variety of responses to CO2 enrichment and the underlying mechanisms are largely unknown. This physiological study compared the responses of a CCM species (Lomentaria australis) with a non-CCM species (Craspedocarpus ramentaceus) to CO2 enrichment with regards to growth, net photosynthesis, and biochemistry. Contrary to expectations, there was no enrichment effect for the non-CCM species, whereas the CCM species had a twofold greater growth rate, likely driven by a downregulation of the energetically costly CCM(s). This saved energy was invested into new growth rather than storage lipids and fatty acids. In addition, we conducted a comprehensive literature synthesis to examine the extent to which the growth and photosynthetic responses of fleshy macroalgae to elevated CO2 are related to their carbon acquisition strategies. Findings highlight that the responses of macroalgae to CO2 enrichment cannot be inferred solely from their carbon uptake strategy, and targeted physiological experiments on a wider range of species are needed to better predict responses of macroalgae to future oceanic change.
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Affiliation(s)
- Luna M. van der Loos
- Institute for Marine and Antarctic StudiesUniversity of TasmaniaHobartTasmaniaAustralia
- Marine EcologyUniversity of GroningenGroningenThe Netherlands
| | - Matthias Schmid
- Institute for Marine and Antarctic StudiesUniversity of TasmaniaHobartTasmaniaAustralia
| | - Pablo P. Leal
- Institute for Marine and Antarctic StudiesUniversity of TasmaniaHobartTasmaniaAustralia
- Instituto de Fomento Pesquero (IFOP)Puerto MonttChile
| | - Christina M. McGraw
- Department of Chemistry, NIWA/University of Otago Research Centre for OceanographyUniversity of OtagoDunedinNew Zealand
| | - Damon Britton
- Institute for Marine and Antarctic StudiesUniversity of TasmaniaHobartTasmaniaAustralia
| | | | - Patti Virtue
- Institute for Marine and Antarctic StudiesUniversity of TasmaniaHobartTasmaniaAustralia
- CSIRO Oceans and AtmosphereHobartTasmaniaAustralia
- Antarctic Climate and EcosystemsCooperative Research CentreHobartTasmaniaAustralia
| | - Peter D. Nichols
- Institute for Marine and Antarctic StudiesUniversity of TasmaniaHobartTasmaniaAustralia
- CSIRO Oceans and AtmosphereHobartTasmaniaAustralia
| | - Catriona L. Hurd
- Institute for Marine and Antarctic StudiesUniversity of TasmaniaHobartTasmaniaAustralia
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