Download or read book Investigating the Photophysiology of a Tropical Crustose Coralline Alga at Different Depths Under Ocean Acidification Conditions written by Ashtyn Lynné Isaak and published by . This book was released on 2021 with total page 98 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ocean acidification (OA) negatively affects marine calcifying organisms and can alter many chemical and physiological processes. Crustose coralline algae (CCA), such as Porolithon onkodes, are important structural calcifying components on coral reefs and they grow across a range of depths. This research investigated the interactive effects of light quantity, spectral quality and pCO2 on P. onkodes to determine if CCA are impacted differentially by OA as a function of depth. In the first experiment, I tested the effects of increased pCO2 on Porolithon onkodes collected from two different depths. Light filters were utilized to simulate light quality at shallow back reef environments at 2-m depth and deeper fore reef environments at 17-m depth in manipulative mesocosm experiments at both ambient and elevated pCO2 treatments (400 μatm pCO2 and 1000 μatm pCO2). Results of this experiment showed no effects of OA on photosynthesis, respiration, calcification, or most photosynthetic pigment concentrations (except for phycoerythrin). Photosynthesis also did not differ between depths suggesting that photosynthesis in this species is not stimulated by blue wavelengths of light and may saturate at low levels of photon flux density (PFD). However, samples from shallow water calcified 64.7% faster than samples from the deep environment over the experiment, which is likely due to increased PFD and also indicates that photosynthesis and calcification may not be as tightly coupled as previously thought. The second set of experiments investigated the differences in photochemical efficiency of P. onkodes under OA conditions in a mesocosm experiment, and also by changes in algal orientation in relation to sunlight at different depths in a field experiment. The effective quantum yield of photosynthetic energy conversion (fluorescence yield), and the relative rate of electron transport through PSII (rETR) were quantified using a PAM fluorometer. Fluorescence yield was greatest in low-PFD environments in both the mesocosm and field experiments by 29.8% - 46.4% compared to the high-light environments. rETR were between 11.0% - 49.4% less than samples from high-PFD compared to low-PFD environments. OA at 1000 μatm pCO2 compared to 400 μatm pCO2 resulted in a decrease of fluorescence yield by 6.7% in the deep treatment, and by 21.7% in the high-PFD environment, which may be attributed to decreases in phycoerythrin pigment concentration. Overall, this study suggests that increased PFD is more important than spectral quality for P. onkodes, and although this study found no effects of OA on photosynthesis, respiration, or calcification rates, it did impact the concentration of the photosynthetic pigment phycoerythrin in low-PFD environments. Decreases in phycoerythrin in elevated pCO2 in low-PFD environments suggests that P. onkodes may be more impacted by OA in a fore reef compared to a back reef environment. Future studies should conduct longer experimental periods to determine if this pattern will ultimately result in decreases in photosynthesis and calcification.

Download or read book The Effects of Light Temperature and Ocean Acidification on the Physiology and Ecology of Tropical Crustose Coralline Algae written by Amy A. Briggs and published by . This book was released on 2016 with total page 127 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Combined Effects of Ocean Acidification with Morphology Water Flow and Algal Acclimation on Metabolic Rates of Tropical Coralline Algae written by Sarah Merolla and published by . This book was released on 2017 with total page 135 pages. Available in PDF, EPUB and Kindle. Book excerpt: Coral reefs are currently facing multiple stressors that threaten their health and function, including ocean acidification (OA). OA has been shown to negatively affect many reef calcifiers, such as coralline algae that provide many critical contributions to reef systems. Past studies have focused on how OA independently influences coralline algae, but more research is necessary as it is expected that the effects of OA on coralline algae will vary depending on many other factors. To better understand how algal morphology, water flow, and algal acclimation interact with OA to affect coralline algae, three studies were conducted in Moorea, French Polynesia, from June 2015 to July 2016. In January 2016, I tested the hypothesis that algal individuals with higher morphological complexity would exhibit faster metabolic rates under ambient pCO2 conditions, but would also demonstrate higher sensitivity to OA conditions. For three species of crustose coralline algae, Lithophyllum kotschyanum, Neogoniolithon frutescens, and Hydrolithon reinboldii, algal individuals with more complex morphologies demonstrated faster rates of calcification, photosynthesis, and respiration in the ambient pCO2 treatment than individuals with simpler morphological forms. There also appeared to be a relationship between morphology and sensitivity to OA conditions, with calcification rates negatively correlated with higher morphological complexity. In the summers of 2015 and 2016, I conducted three experiments examining the effects of water flow and OA on different morphologies of coralline algae to test the hypotheses that increased flow would enhance metabolic rates and mitigate the effects of OA, and that algae with more complex morphologies would be more responsive to increased water flow and more sensitive to OA conditions. A field experiment investigating the effects of water flow on Amphiroa fragilissima, L. kotschyanum, N. frutescens, and H. reinboldii detected enhanced rates of calcification, photosynthesis, and respiration with increased flow, and this relationship appeared to be the strongest for the crustose algal species with the highest structural complexity. A flume manipulation examining the combined effects of water flow and OA on A. fragilissima, L. kotschyanum, N. frutescens, H. reinboldii, and Porolithon onkodes suggested that coralline algal species with high structural complexity were the most sensitive to OA conditions. Finally, A. fragilissima and L. kotschyanum were maintained in different pCO2 and water flow conditions in a long-term mesocosm experiment, which indicated that flow was unable to mitigate the effects of OA on coralline algae. In the summer of 2016, I investigated the acclimation potential of A. fragilissima and L. kotschyanum to OA, and predicted that the original treatment conditions would induce phenotypic modifications that would influence algal responses to the end treatment. There were negative effects of long-term exposure of coralline algae to elevated pCO2 conditions on calcification and photosynthesis, though partial acclimation in calcification to OA was observed. The instantaneous exposure of elevated pCO2 had negative impacts on algal calcification, but had a nominal effect on photosynthesis. No effects of long-term or instantaneous exposure to elevated pCO2 were observed for respiration. The results of these studies indicate that the coralline algal response to OA conditions will likely be complex and depend on numerous factors including water flow, morphology, and acclimation potential. Therefore, it is critical that future studies further investigate the effects of these factors; specifically examining the mechanisms that underlie these responses in order to better predict the future of coralline algae and thus coral reef ecosystems in a more acidic ocean.

Download or read book Coralline Algae Globally Distributed Ecosystem Engineers written by Laurie Carol Hofmann and published by Frontiers Media SA. This book was released on 2020-07-08 with total page 159 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Effects of Nutrient Addition and Ocean Acidification on Tropical Crustose Coralline Algae written by Bridget Francine Shayka and published by . This book was released on 2018 with total page 97 pages. Available in PDF, EPUB and Kindle. Book excerpt: As the global population increases, the occurrence of multiple anthropogenic impacts on valuable coastal ecosystems, such as coral reefs, also increases. These stressors can be global and long-term, like ocean acidification (OA), or local and short-term, like nutrient runoff in some areas. The combination of these stressors can potentially have additive or interactive effects on the organisms in coral reef communities. Among the most important groups of organisms on coral reefs are crustose coralline algae (CCA), calcifying algae that cement the reef together and contribute to the global carbon cycle. This thesis studied the effects of nutrient addition and OA on Lithophyllum kotschyanum, a common species of CCA on the fringing reefs of Mo'orea, French Polynesia. Two mesocosm experiments tested the individual and interactive effects of OA and short-term nitrate and phosphate addition on L. kotschyanum. These experiments showed that nitrate and phosphate addition together increased photosynthesis, OA had interactive effects with nutrient addition, and after nutrient addition ended, calcification and photosynthetic rates changed in unpredictable ways in different OA and nutrient treatments. Because the results of the first two experiments showed impacts of nutrients even after addition stopped, two more mesocosm experiments were conducted to study the changes in photosynthesis and calcification over hourly time scales more relevant to a single nutrient pulse event. These two experiments revealed the existence of diurnal variation in light-saturated photosynthetic rate, but not calcification rate, under ambient and elevated pCO2. This pattern of increased maximum photosynthesis in the middle of the day can have important implications for how the time of nutrient runoff events during the day impacts CCA physiology. Finally, a field experiment was conducted to determine the effects of short- and long-term nutrient addition on L. kotschyanum. The results showed that a series of short-term nutrient additions did not increase photosynthesis or calcification rates above those in ambient nutrient conditions, but continual nutrient enrichment for 6 weeks increased photosynthetic rates. This increase in photosynthesis under only long-term enrichment shows the need for consideration of specific nutrient addition scenarios on coral reefs when predicting how the community will be affected.

Download or read book The Effect of Ocean Acidification on the Ecology of Two Tropical Crustose Coralline Algae phylum Rhodophyta written by Joshua Caraher-Fergusson Manning and published by . This book was released on 2017 with total page 92 pages. Available in PDF, EPUB and Kindle. Book excerpt: Crustose coralline algae (CCA) are important members of coral reef communities. They accrete and consolidate the calcium carbonate framework of coral reefs, and some species are an important settlement substratum for coral larvae. CCA community composition is shaped, at least in part, by herbivory and competition. However, ocean acidification (OA) is negatively affecting CCA, with potential to affect CCA responses to herbivory (wounding) and their ability to compete for space. Changes in seawater chemistry because of OA cause reductions in the recruitment, abundance, and net calcification of CCA. In this thesis, the effects of OA on net calcification, regeneration of wounds, and competition was quantified for two species of CCA common in the back reefs of Mo'orea, French Polynesia; Porolithon onkodes and Lithophyllum insipidum. Three separate experiments were conducted in four flowing seawater tanks (flumes), each set to a different target pCO2 level representative of ambient (~ 400 μatm) or predicted end of the 21 century pCO2 (~ 700, 1000, and 1300 μatm). P. onkodes, was found to be the most abundant species of CCA in the back reefs of Mo'orea, followed by L. flavescens and L. insipidum. The abundance of P. onkodes is likely a direct result of its competitive ability. P. onkodes is thicker on average than the other common CCA in the back reefs of Mo'orea, and thicker species generally become dominant in areas of intense herbivory, such as coral reefs. In a flume experiment conducted from January to March 2016, net calcification declined 85% in P. onkodes at elevated pCO2 compared to a decline of 42% in L. insipidum, indicating that P. onkodes may be more negatively affected by OA. The differential responses to OA found here could alter the outcome of competitive interactions between P. onkodes and L. insipidum, leading to changes in the abundances of these species in CCA communities. Few studies have quantified the potential for OA to interact with natural disturbances, such as wounding of the thallus by herbivores. A flume experiment conducted from May to July 2016 found that there was a 58% reduction in the rate of vertical regeneration of artificial wounds within P. onkodes at elevated pCO2. This result could have important implications for the response of P. onkodes to grazing by excavating herbivores like parrotfish and sea urchins. Inability for CCA to recover from wounding, could increase the susceptibility of CCA to further wounding. In addition, the reductions in vertical regeneration of the wounds could also be indicative of reduced vertical growth rates. CCA with thicker thalli generally outcompete thinner CCA. Reduced vertical growth rates could reduce thallus thickness, and affect the outcome of competitive interactions among CCA. A flume experiment conducted from June to July 2016 found that there was no effect of elevated pCO2 on the outcome of competitive interactions between P. onkodes and L. insipidum. It is likely that this result may have been due to the relatively short duration of this experiment (one month). There was, however, an effect of the identity of the competitor on the proportion of live tissue remaining in focal individuals of P. onkodes. The proportion of live tissue remaining in focal individuals of P. onkodes was significantly lower in intraspecific pairings than in interspecific pairings or when paired with non-living substrate (controls). This result highlights the importance of including both intraspecific and interspecific interactions in future studies of the effects of OA on competition. Experiments of longer durations may elucidate the potential for elevated pCO2 to affect competition among CCA. CCA are ecologically important members of coral reefs. Changes in the community composition of CCA on coral reefs, because of altered competitive abilities under elevated pCO2, could affect the roles that CCA play in building and maintain coral reef ecosystems.

Download or read book The Effects of Ocean Acidification Elevated Temperature and Herbivory on Tropical Crustose Coralline Algae written by Maggie Dorothy Johnson and published by . This book was released on 2011 with total page 240 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Assessing Ocean Acidification Impacts on the Reef Building Properties of Crustose Coralline Algae written by Merinda Catherine Nash and published by . This book was released on 2016 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Crustose coralline algae (CCA), and in particular Porolithon onkodes, play an important reef-building role in modern tropical coral reefs. CCA form thick crusts of Mg-calcite and grow over corals and loose substrate to bind these together. This binding and cementing process is fundamental to the development of structural reefs that are capable of withstanding the high-energy waves in the shallow to inter-tidal areas of the reef. As anthropogenic CO2 emissions continue to increase, the oceans absorb part of this extra CO2 and become more acidic, a process known as Ocean Acidification (OA). There are concerns that OA will have a negative affect on the reef-building capacity of coral reef organisms, in particular on CCA. This is because Mg-calcite is meta-stable and more susceptible to dissolution than aragonite, the mineral used by corals to build skeletons. The goal of this thesis work was to firstly understand the physical and mechanical properties that enable the CCA to cement the reef and withstand damage from high-energy waves, bioerosion and chemical dissolution. Secondly, to anticipate how OA may interfere with these reef-building properties. These goals were pursued by setting clear aims with associated specific objectives designed to elucidate information relevant to these questions. Methods were developed for X-ray diffraction to identify the mineral composition of CCA. Nanoindentation was investigated as a tool for determining the mechanical properties of CCA and the measurement of fracture toughness was found to return physically meaningful information relevant to structural reef development. Study of CCA calcification showed that cell wall Mg-calcite exhibited radial crystal morphology in agreement with published studies on temperate species. However, high-resolution imaging showed the radial crystals were made of banded stacked sub-micron grains within an organic framework. Dolomite was found not only as cell lining by submicron rhombs, but also as the primary calcification of hypothallial cell walls. Dolomite is shown to be resistant to bacterial erosion. A model is developed whereby it is proposed that dolomite formation is dependent on polysaccharide accumulation. Using nanoindentation, P. onkodes are found to be extraordinarily tough, on par with the measured fracture toughness for metamorphic minerals quartz and corundum. The fracture toughness is enabled by the presence of dolomite cell lining. Contrary to the literature, bacterial erosion is found to be a constructive, not destructive, process. A survey of P. onkodes from Heron Island fore reef and reef flat showed that dolomite was present in all the fore reef crusts but none of the reef flat crusts. The reef flat crusts did not have fracture resistance except where remineralised. The presence of dolomite cell lining was shown to decrease skeletal dissolution rates by an order of magnitude. OA experiments showed that skeletal dissolution rates increased with elevated pCO2, but dolomite continued to confer resistance to dissolution. pCO2 levels did not affect the skeletal Mg content or dolomite formation in living CCA. Of concern, and in agreement with the literature, bacterial erosion is accelerated under a combination of elevated pCO2 and temperatures, suggesting this may be the main threat to CCA reef-building in the future. The experimental findings were corroborated by results of a field survey along a natural pCO2 gradient. In summary, dolomite was found to be an essential component of modern reef development via its contribution to enabling CCA P. onkodes thick crust development and persistence. Reef building by CCA P. onkodes is likely to continue as pCO2 rises up until a tipping point is reached whereby bacterial erosion switches from constructive to destructive.

Download or read book Impacts of Ocean Acidification on Coralline Algae written by Chenchen Shen and published by . This book was released on 2017 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt: Oceanic uptake of rising anthropogenic CO2 emissions has caused the emergence of ocean acidification as a major threat to marine ecosystems worldwide. Along eastern boundary current systems, seawater is naturally acidified due to coastal upwelling of low pH seawater from depth. Compounded by ocean acidification, upwelling regions are expected to become increasingly corrosive to calcifying organisms, potentially forcing them beyond their physiological tolerance windows. In my dissertation, I focused on the impacts of ocean acidification on calcareous coralline algae in the California Current System. Using coralline algae in rocky intertidal habitats as model organisms, I extend the implications of ocean acidification from the organismal level to the broader community level. Global environmental change implies not only gradual changes in the mean values of environmental variables but also an increase in variability and the likelihood of rare, extreme events. In Chapter 2, I conducted a laboratory experiment to explore potential interactions between two different types of environmental stressors. Specifically, I tested the effects of elevated pCO2, including variable pCO2 treatments, and a severe desiccation event on the coralline species, Corallina vancouveriensis. I found that C. vancouveriensis growth was negatively impacted by both elevated pCO2 and desiccation stress, although their combined effects were approximately additive rather than synergistic. Furthermore, while high pCO2 at constant levels only caused small reductions in algal growth over a two-week period, these effects were exacerbated by pCO2 variability. One criticism of laboratory experiments testing species responses to environmental change is that they isolate organisms under simplified conditions. The potential of overlooking important biotic or abiotic factors present in the natural environment limits the inferences that can be made from laboratory studies. In Chapter 3, I conducted a reciprocal removal experiment at two field sites and two wave exposures to investigate potential changes in the interactions between coralline and fleshy turf-forming algae since the 1980s. I used as a baseline the results from a similar study conducted nearly 30 years ago that failed to detect spatial competition between coralline and fleshy algae. Despite the progression of ocean acidification over the last three decades, my results indicated that the lack of competition between coralline and fleshy algae persists to this day, with results consistent across both sites and wave exposures. The findings in Chapter 3 refer to present-day interactions, but in the future, ocean acidification is expected to be detrimental to coralline algae while potentially benefitting fleshy algae. Both coralline and fleshy algae form turf habitats that shelter diverse epifaunal communities. Thus, changes in the algal composition of turf habitats may lead to broader changes encompassing epifaunal communities, depending on the degree of specialization displayed in epifaunal habitat associations. In Chapter 4, I compared the abundance, richness, and community composition of epifauna between coralline and fleshy turf habitats at four sites along the Oregon-California coast. I found that epifauna were more abundant in coralline turfs due to higher turf density. However, epifaunal richness and community composition were similar between turf types, indicating high levels of redundancy in habitat provision between coralline and fleshy algae. Since most species of epifauna tended to be turf generalists, they may be resistant to the potential indirect effects of ocean acidification involving declines in coralline turf habitat. My dissertation combined a variety of standard ecological methodologies to help translate ocean acidification impacts from the organismal level to the community level. Overall, while I found that elevated pCO2 decreased coralline growth in the laboratory, evidence from the field suggested a capacity for communities to resist the effects of ocean acidification and remain resilient. In the natural environment, ocean acidification impacts may be moderated by multiple environmental variables working in different directions, the temporal dynamics of stressors allowing for periods of recovery, and species interactions having dampening effects. One way forward to unite theories of change with those of resistance is to identify ecosystem indicators and critical thresholds that may help provide a more comprehensive view of ecosystem functioning and stability in the face of global change.

Download or read book Crustose coralline red algae frameworks and rhodoliths Past and present written by Ana Cristina Rebelo and published by Frontiers Media SA. This book was released on 2023-01-03 with total page 148 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Photosynthesis in Algae Biochemical and Physiological Mechanisms written by Anthony W.D. Larkum and published by Springer Nature. This book was released on 2020-06-03 with total page 534 pages. Available in PDF, EPUB and Kindle. Book excerpt: Algae, including cyanobacteria, are in the spotlight today for a number of reasons; firstly it has become abundantly clear over recent years that algae have been neglected in terms of basic research and that knowledge gap is being rapidly closed with the establishment of some surprising discoveries, such as the presence of Near-Infra-Red-Absorbing cyanobacteria and a wealth of natural products; secondly molecular approaches have provided a wealth of approaches to genetically modify algae and produce value-added products; thirdly it has become clear just how important, marine phytoplankton is to global carbon capture and the production of food globally; and fourthly, it has also become clear that algae present unparalleled opportunities to generate biofuels in a sustainable and non-polluting way. This volume presents 15 chapters by world experts on their subjects, ranging from reviews of algal diversity and genetics to in-depth reviews of special algal groups such as diatoms (which account for over 30% of marine carbon capture). Other chapters chart the ways in which this carbon capture occurs or how there are a multiplicity of ways in which algae intercept sun light and deploy this energy for carbon capture. A fascinating aspect here is the way in which sun light is harvested. A special chapter is devoted to the very recent and exciting possibility that algae use coherent light energy transformation to enhance the efficiency of light capture, an aspect of quantum physics that has implications for future developments at several levels and a variety of industries. Just how and why algae use Chlorophyll a as the major light capture pigment is discussed in several chapters. However, attention is also given to those cyanobacteria, which have been found to use the special Near-Infra Red absorbing chlorophylls mentioned above. And attention is also given to those algae that employ phycobiliproteins to fill in the “green window”, i.e., the spectral region from 400 – 650 nm, which is not efficiently covered by chlorophyll and carotenoid pigments. Photoinhibition and photoprotection is the subject area of several chapters and one which it is essential to understand a we work towards greater efficiency of algal photosynthesis. A final chapter is devoted to understanding the molecular basis for coral bleaching, a much-neglected area that is essential in trying to come up with solutions to this very worrying phenomenon, caused by global warming and ocean acidification. This is a book for research scientists, environmentalists, planners in a range of areas including those of marine resources, nutrient control and pollution of water bodies and that growing body of concerned citizens interested in controlling carbon emissions and global warming. Special attention has been given to generating a set of articles that will be read by university students, informed laymen and all those whose wish to understand the rapid changes that have come about in our knowledge of algae over the past decade.

Download or read book The Combined Effects of Ocean Acidification with Fleshy Macroalgae and Filamentous Turfs on Tropical Crustose Coralline Algae written by Lansing Yun Perng and published by . This book was released on 2019 with total page 111 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Ocean Acidification Effects on Photosynthesis in Tropical Marine Macroalgae written by Regina C. Zweng and published by . This book was released on 2017 with total page 82 pages. Available in PDF, EPUB and Kindle. Book excerpt: Field data from CO2 vents, a current model of future ocean acidification conditions, show a positive correlation between elevated seawater pCO2 and fleshy macroalgal abundance, as well as a negative correlation between elevated seawater pCO2 and calcareous macroalgal abundance on coral reefs. One underlying physiological mechanism for increases of fleshy macroalgae species in response to greater pCO2 could be an increase in their photosynthesis. Furthermore, inorganic carbon use mechanisms, irradiance and depth may influence species-specific responses to ocean acidification. Therefore, this thesis aimed to discern carbon use strategies and photosynthetic responses to elevated pCO2 of dominant tropical fleshy and calcareous macroalgae. All species studied were able to utilize HCO3 - for photosynthesis. 33% of calcifying macroalgae and 80% of fleshy macroalgae had increased photosynthetic rates in response to lower pH. Thus, future conditions of OA may perpetuate or exacerbate the abundance of fleshy seaweeds at the expense of calcareous species.

Download or read book Ocean Acidification written by Michael J. W. Doherty and published by . This book was released on 2009 with total page 336 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Combined Effects of Ocean Acidification with Water Flow and Temperature on Tropical Non calcareous Macroalgae written by Maureen Ho and published by . This book was released on 2016 with total page 120 pages. Available in PDF, EPUB and Kindle. Book excerpt: The vulnerability of coral reefs has substantially increased in the past few decades due to accelerating human-driven global change. The effects of ocean acidification (OA) and global warming individually and interactively have resulted in varying degrees of responses in benthic reef organisms. For non-calcareous macroalgae, the physiological and ecological responses to physical environmental changes can alter their relative abundances, which are often used as an indicator of the overall coral reef status. To better understand how fleshy macroalgae will respond to various physical parameters, three separate experiments were conducted from June 2014 to July 2015 in Moorea, French Polynesia. An important physical driver in transferring nutrients and dissolved gases to benthic reef organisms is water motion. In 2014, I tested the hypothesis that increased water motion and elevated pCO2 would benefit Amansia rhodantha (a CO2 user) more than Dictyota bartayresiana and Lobophora variegata (HCO3- users). The highest and lowest growth rates were at the intermediate and highest flow speed, respectively, for all three species. A. rhodantha exhibited the greatest reduction in biomass at reduced flow under ambient pCO2, indicating high sensitivity to mass transfer and carbon limitation. In 2015, the interactive effects of temperature and OA were tested in a two-part study on the metabolic (i.e. photosynthesis and respiration) and growth responses of D. bartayresiana and A. rhodantha. The first study in January 2015 showed that net photosynthesis in both species was affected by high pCO2 but not temperature, and the combination of temperature and OA affected respiration rates. In the second study in July 2015, metabolic rates were affected by temperature but not pCO2. Net photosynthesis and respiration of A. rhodantha were highest under OA conditions at 27.5 oC, but were reduced at 30 oC. There was no effect on metabolic rates of D. bartayresiana across all temperature treatments. The relative growth rates for D. bartayresiana were higher than A. rhodantha in the first study, while both species exhibited varying responses to treatments in the second study. Lastly, from May to June 2015, massive Porites spp. was paired with D. bartayresiana in competitive interactions at low and high flow speeds under ambient and elevated pCO2 levels. I tested the hypothesis that increased water flow would increase algal growth rates, enhancing the competitive ability of the alga against the coral. For corals, I predicted that OA and reduced water flow would negatively affect the corals, thus increasing susceptibility to algal overgrowth. Net calcification and the photosynthetic efficiency of corals were used as a proxy for fitness and health status, respectively, however neither was affected by water flow or OA. On the contrary, growth rates of D. bartayresiana were significantly reduced under low flow. The negative effects of reduced water motion on macroalgae may potentially compromise the ability of the alga to compete. The variation in water motion can affect resource acquisition and when combined with OA, can have significant implications on species interactions. These results indicate the importance of water motion in influencing macroalgal growth and provide insights to the varying responses in fleshy macroalgae to global change. Furthermore, their physiological responses may be attributed to their different carbon uptake strategies, as A. rhodantha was more sensitive to reduced flow and temperature than D. bartayresiana.

Download or read book Coralline Algae Past Present and Future Perspectives written by Laurie Carol Hofmann and published by Frontiers Media SA. This book was released on 2022-12-28 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Characterizing the Response of Coralline Algae to Ocean Acidification and Nutrient Changes in the California Current System written by Sandy Letzing and published by . This book was released on 2013 with total page 42 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ocean acidification (OA) has emerged as an important focus of research and policy in this decade. Ocean acidification specifically refers to changes in the inorganic carbon system in the ocean resulting from its absorption of human-released CO2 from the atmosphere. Anthropogenic atmospheric CO2 levels are rapidly increasing; much of this is dissolved and absorbed in the ocean (~30%) where it reacts with seawater altering fundamental properties including pH, pCO2 and saturation state of carbonate minerals. This change is of concern because of the potential of OA to disrupt biological processes, particularly those processes associated with calcification (Byrne, 2011; Diaz-Pilido, Anthony, Kline, Dove, & Hoegh-Guldberg, 2012). For this study, I chose to investigate red coralline algae as a model organism because OA is predicted to have effects on calcification and photosynthesis, and because of the importance of coralline algae as an ecological engineer, which can be found in shallow water habitats globally. While the response of coralline algae to OA is a serious concern, there remains very limited data on the interactions of OA with other ocean conditions (e.g., temperature, nutrients, and light) that may alter or modify the effects of low pH on coralline algae communities. One nutrient in particular, phosphorus is known to have inhibiting effects on calcification in long-term studies. My objective was to describe the short-term effects of a range of elevated pCO2 and phosphorus levels both alone, and together, on calcification and photosynthetic rates of Corallina vancouveriensis. I exposed these algae to a range of pCO2 and phosphate concentrations and measured changes in total alkalinity, pH, and DO in acute exposure trials (