- A major challenge in biodiversity research is the incorporation of species interactions into frameworks describing population and community response to global edfnmental change (GEC). Mutualisms are a type of species interaction especially sensitive to changing environmental conditions, and the breakdown of facilitative species interactions could amplify the negative impacts of novel climate regimes on focal species.
- Here, we investigate how reciprocal interactions between two coastal foundation species, the eastern oyster (Crassostrea virginica) and eelgrass (Zostera marina) shift in sign and magnitude in response to ocean warming (+1.5°C) and acidification (−0.4 pH) via a manipulative co-culture experiment in mesocosms.
- Under ambient environmental conditions, oysters facilitated eelgrass leaf growth and clonal reproduction by 35% and 38%, respectively. Simultaneously, eelgrass decreased the oyster condition index (the ratio of tissue to shell biomass) by 35%, indicating greater allocation of energy to shell growth instead of soft tissues at ambient conditions. Varying sensitivities of each species to ocean warming and/or acidification treatments led to complex shifts in species interactions that were trait dependent. As such, community outcomes under future conditions were influenced by species interactions that amplified and mitigated species response to environmental change.
- Synthesis: Given that species interaction effect sizes were similar in magnitude to effect sizes of warming or pH treatments, our results underscore the need to identify key species and interaction types that strongly influence community response to GEC. Specifically, for macrophyte-bivalve interactions, understanding how physiological limitations on growth are impacted by environmental heterogeneity and co-culture will support the successful restoration of natural populations and the rapid expansion of aquaculture.
Posts Tagged 'morphology'
Shifting seagrass-oyster interactions alter species response to ocean warming and acidification
Published 30 September 2024 Science ClosedTags: algae, biological response, BRcommunity, mesocosms, mollusks, morphology, physiology
Impact of low pH/high pCO2 on the physiological response and exopolysaccharide content in cyanobacteria Trichodesmium erythraeum
Published 26 September 2024 Science ClosedTags: biological response, BRcommunity, growth, laboratory, morphology, performance, prokaryotes
The acidification of the ocean caused by the diffusion of anthropogenic carbon dioxide (CO2) into seawater has been believed to threaten the stability of the marine ecosystem. As one of the major contributors to the primary production in oligotrophic oceans, the response of Trichodesmium to the acidification of the ocean has attracted a lot of attention. Therefore, in this study, we applied physiological and biochemical methods to identify the influences of high pCO2 and low pH conditions on the growth of T. erythraeum. Our results showed that the low pH during the acidification of the ocean was the main factor inhibiting the growth of T. erythraeum. In addition, low pH caused oxidative stress to T. erythraeum, as evidenced by the increase of the reactive oxygen species and antioxidant enzyme’s activities. The activity of carbonic anhydrase (CA) enzyme is dually regulated by pCO2 and pH, and T. erythraeum can adapt to different levels of pCO2 and pH in seawater by flexibly adjusting CA enzyme activity. We also discovered that the stimulatory effect of high pCO2 on the exopolysaccharide (EPS) content of T. erythraeum outweighed the inhibitory effect of low pH during the process of ocean acidification. In conclusion, this study systematically revealed the effects of high pCO2 and low pH caused by the acidification of the ocean on the growth and EPS of T. erythraeum. These results provide new insights into the response mechanisms of T. erythraeum in the acidified ocean under future climate conditions.
Continue reading ‘Impact of low pH/high pCO2 on the physiological response and exopolysaccharide content in cyanobacteria Trichodesmium erythraeum’Lactiplantibacillus plantarum I induces gonad growth in the queen scallop Aequipecten opercularis (Linnaeus, 1758) under conditions of climate change
Published 19 September 2024 Science ClosedTags: biological response, laboratory, Mediterranean, mollusks, morphology, multiple factors, nutrients, physiology, prokaryotes
Climate change has presented a serious problem in recent times, which is why a new approach is being sought in terms of aquacultural food quality. In this study, the influence of temperature increase (by 2 °C) and pH decrease (by 0.2) was investigated on the queen scallop, Aequipecten opercularis (Linnaeus, 1758). Furthermore, the effect of a food-enriched diet with the probiotic culture Lactiplantibacillus plantarum I was assessed in climate-changed conditions. Scallops’ morphometric parameters were measured before the experimental setup and after one month of being kept in controlled conditions. Morphometric parameters included the elongation index, compactness index, convexity index, density index, condition index, meat yield, gonadosomatic index, adductor muscle index, and hepatosomatic index. Climate-changed conditions had no effect on the scallop condition index, meat yield, or hepatosomatic index. Nevertheless, the addition of probiotics to their diet had a positive effect on the queen scallops cultivated under conditions of climate change, influencing positive allometry and the increase of the gonadosomatic indices. On the other hand, the same conditions negatively affected the adductor muscle index of the scallops. To conclude, in the context of climate change conditions, queen scallops could be a good organism of choice that can be very well adapted to the changed environmental conditions, especially with the addition of the lactic acid bacteria culture Lpb. plantarum I.
Continue reading ‘Lactiplantibacillus plantarum I induces gonad growth in the queen scallop Aequipecten opercularis (Linnaeus, 1758) under conditions of climate change’Effects of ocean acidification and nitrogen limitation on the growth and photophysiological performances of marine macroalgae Gracilariopsis lemaneiformis
Published 11 September 2024 Science ClosedTags: algae, biological response, growth, laboratory, morphology, North Pacific, photosynthesis, physiology, respiration
To investigate the effects of ocean acidification (OA) and nitrogen limitation on macroalgae growth and photophysiological responses, Gracilariopsis lemaneiformis was cultured under two main conditions: ambient (Low CO2, LC, 390 μatm) and CO2 enriched (High CO2, HC, 1000 μatm), with low (LN, 7 μmol L-1) and high (HN, 56 μmol L-1) nitrate. High CO2 levels decreased growth under both LN and HN treatments. HC reduced Chl a, carotenoids, phycoerythrin (PE), and phycocyanin (PC) under HN conditions, while only Chl a decreased under LN conditions. NO3– uptake rate was restricted under LN compared to HN, while HC enhanced it under HN. Net photosynthetic O2 evolution rates did not differ between CO2 and nitrate treatments. Dark respiration rates were higher under HN, further boosted by HC. The stimulated effective quantum yield (Y(II)) corresponded to decreased non-photochemical quenching (NPQ) under HN conditions. Nitrate, not CO2, showed significant effects on the relative electron transport rate (rETRmax), light use efficiency (α) and saturation light intensity (Ik) that with lowered rETRmax and α under LN culture. Our results indicate that OA may negatively affect Gracilariopsis lemaneiformis growth and alter its photophysiological performance under different nutrient conditions.
Continue reading ‘Effects of ocean acidification and nitrogen limitation on the growth and photophysiological performances of marine macroalgae Gracilariopsis lemaneiformis’Effect of pH on development of the zebrafish inner ear and lateral line: comparisons between high school and university settings
Published 21 August 2024 Science ClosedTags: biological response, chemistry, education, fish, laboratory, morphology, physiology
Increasing carbon dioxide levels associated with climate change will likely have a devastating effect on aquatic ecosystems. Aquatic environments sequester carbon dioxide, resulting in acidic conditions that can negatively affect fish development. Increasing climate change impacts in the coming decades will have an outsized effect on younger generations. Therefore, our research had two interconnected goals: 1) understand how aquatic acidification affects the development of zebrafish, and 2) support a high school scientist’s ability to address environmental questions of increasing importance to her generation. Working with teachers and other mentors, the first author designed and conducted the research, first in her high school, then in a university research laboratory. Zebrafish embryos were reared in varying pH conditions (6.7–8.2) for up to 7 days. We assessed fish length and development of the inner ear, including the otoliths; structures that depend on calcium carbonate for proper development. Although pH did not affect fish length, fish reared in pH 7.75 had smaller anterior otoliths, showing that pH can impact zebrafish ear development. Furthermore, we demonstrate how zebrafish may be used for high school students to pursue open-ended questions using different levels of available resources.
Continue reading ‘Effect of pH on development of the zebrafish inner ear and lateral line: comparisons between high school and university settings’Effects of food supply on northern bay scallops Argopecten irradians reared under two pCO2 conditions
Published 15 August 2024 Science ClosedTags: biological response, chemistry, growth, laboratory, mollusks, morphology, mortality, North Atlantic, physiology, respiration
For calcifying organisms such as bivalves, short-term exposure to increased ocean acidification (OA; elevated pCO2) may reduce growth rate, increase mortality, and disrupt shell formation. A growing body of research suggests that clearance rates and what particles bivalves select may change under high pCO2 exposure; however, these experiments are acute, ranging from days to weeks. The effects of food supply on bivalves under long-term OA exposure remain incompletely understood. In this study, juvenile northern bay scallops Argopecten irradians (Lamarck) that had been reared since 4 h post-fertilization under one of 2 OA conditions (∼500-600 or ∼750-850 µatm pCO2; ∼1.37-1.5 or ∼1.0-1.2 Ωaragonite), were subjected to 2 food levels for 42 d (low food: ∼400, high food: ∼1400 chlorophyll cells ml-1). Standard metabolic rate (SMR) and clearance rate (CR) were measured on Day 0, and SMR, CR, growth, and survivorship were measured at 14 and 42 days of exposure to 2 food levels for each of the OA treatments. Juveniles under food scarcity had reduced survivorship and growth independent of OA treatment. We found no effect of OA treatment or an OA × food interaction for these metrics. There was only a food-level effect for SMR and no OA treatment effect; however, there was an interaction between food and OA for CR. Under elevated pCO2 concentrations, scallops cleared Chaetoceros neogracile (strain Chaet-B) over Tetraselmis chui (strain PLY429) and natural seston. Altogether, these data suggest that tolerance to OA mediated by food may depend on food quality or other characteristics that influence particle selection under short-term experimental challenges.
Continue reading ‘Effects of food supply on northern bay scallops Argopecten irradians reared under two pCO2 conditions’Projected impacts of climate change and watershed management on carbonate chemistry and oyster growth in a coastal plain estuary
Published 15 August 2024 Science ClosedTags: biological response, chemistry, individualmodeling, modeling, mollusks, morphology, North Atlantic
Coastal acidification, warming, and nutrient management actions all alter water quality conditions that marine species experience, with potential impacts to their physiological processes. Decreases in calcite saturation state (ΩCa) and food availability, combined with warming water temperatures, pose a threat to calcifying organisms; however, the magnitude of future changes in estuarine systems is challenging to predict and not well known. This study aims to determine how and where oysters will be affected by future acidification, warming, and nutrient reductions, and the relative effects of these stressors. To address these goals, an oyster bioenergetics model for Eastern oysters (Crassostrea virginica) was embedded in a 3-D coupled hydrodynamic-biogeochemistry model implemented for tributaries in the lower Chesapeake Bay. Model simulations were forced with projected future conditions (mid-21st century atmospheric CO2, atmospheric temperature, and managed nutrient reductions) and compared with a realistic present-day reference run. Together, all three stressors are projected to reduce ΩCa and growth of oyster shell and tissue. Increased atmospheric CO2 and temperature are both projected to cause widespread reductions in ΩCa. The resulting reductions in oyster shell and tissue growth will be most severe along the tributary shoals. Future warming during peak oyster growing seasons is projected to have the strongest negative influence on tissue and shell growth, due to summer water temperatures reducing filtration rates, enhancing respiration and shell dissolution rates, and increasing organic matter remineralization rates, thus reducing food availability. Nutrient reductions will exacerbate deficits in oyster food availability, contributing to further reductions in growth. Quantifying the effects of these stressors provides insight on the areas in the lower bay where oysters will be most vulnerable to mid 21stcentury conditions.
Continue reading ‘Projected impacts of climate change and watershed management on carbonate chemistry and oyster growth in a coastal plain estuary’Morphological and physiological responses of the cosmopolitan marine diatom Thalassiosira rotula to acidification
Published 13 August 2024 Science ClosedTags: biogeochemistry, biological response, chemistry, laboratory, morphology, North Atlantic, performance, physiology, phytoplankton
We investigated the effect of decreased pH on the morphology and nutrient physiology of the cosmopolitan marine diatom Thalassiosira rotula (CCMP3362) by acclimating unialgal cultures to two different CO2 gas concentrations under optimal light, temperature and nutrient conditions. At lower pH (higher CO2), T. rotula exhibited a reduction in cell diameter (7%), surface area (13%), and volume (20%), and an increase in surface area-to-volume ratio (7%). All measures of silicification in T. rotula, i.e., silica (SiO2) quota, rate of silicic acid (Si(OH)4) utilization, and elemental ratios of SiO2:C and SiO2:N, remained unchanged. Similarly, carbon (C) and nitrogen (N) quotas, ratios and utilization rates were mostly unaffected by pH. In contrast, the utilization rate of nitrate (ρNO3) was significantly lower at decreased pH when the rate was normalized by cell number instead of by cell volume. The changes in cell morphology found in this study under low pH were likely not large enough to significantly impact physiological processes and the role of this species in marine food webs and biogeochemical cycles. It is possible that the interactive effects of pH, temperature, light, and nutrient availability characteristic of different regions of the world ocean could result in stronger physiological and morphological responses in this widespread diatom. However, under constant optimal growth conditions, T. rotula was only mildly affected by changes in pH, and in particular the physiology and elemental stoichiometry of C, N and Si were not sensitive to acidification.
Continue reading ‘Morphological and physiological responses of the cosmopolitan marine diatom Thalassiosira rotula to acidification’Cellular and physiological impacts of nanoplastics on the green-lipped mussel Perna viridis under ocean acidification
Published 9 August 2024 Science ClosedTags: biological response, chemistry, laboratory, mollusks, morphology, North Pacific, physiology
Plastics serve as an essential component of modern daily life worldwide, but a notable portion of these plastics eventually turn into waste and find their way into the ocean. Plastic waste breaks down into microplastics (1–5,000 µm) and nanoplastics (NPs; 1–1,000 nm) through processes like ultraviolet degradation. NPs, in comparison to larger-sized plastics, pose a greater biological threat as they can more easily enter cells, leading to immunological stress and oxidative damage that can hinder growth. Among marine organisms, bivalves are particularly susceptible to the impact of NPs due to their filter-feeding nature, which makes ingestion and bioaccumulation of NPs seemingly inevitable. Given the indispensable role of plastics in human society, it is expected that the environmental abundance of NPs will increase in the future. This escalation coincides with the occurrence of ocean acidification (OA), often referred to as the “evil twin” of climate change, which arises from anthropogenic carbon dioxide (CO2) emissions. OA is associated with reduced seawater pH and decreased calcium carbonate saturation, posing a significant risk to marine life, especially calcifying organisms that rely on calcium carbonate for their growth. When OA intersects with NPs, it presents an unresolved understanding of the nature of their interaction and the subsequent biological and ecological consequences. In light of this, the aim of this thesis is to investigate the combined effects of OA and NPs, using the green-lipped mussel Perna viridis as the model species, a calcifying filter-feeder which is vulnerable to both OA and NPs. A factorial-design experiment of OA and NPs was performed for P. viridis over 30 days. Mussels were exposed to four OA scenarios at pH 8.1, 8.0, 7.8 and 7.7, with the partial pressure of CO2 validated to be approximately 470 µatm, 590 µatm, 830 µatm and 1140 µatm, respectively. There were two treatments for each scenario, one without and one dosed with NPs. This experimental design led to eight treatments (4 levels of pH × 2 levels of NPs). The exposure level of NPs was environmentally realistic at 4 × 106 particles mL-1, for 2 h daily. At the end of the experiment, a total of 12 biological endpoints were examined in P. viridis to evaluate the individual and combined effects of OA and NPs.
Continue reading ‘Cellular and physiological impacts of nanoplastics on the green-lipped mussel Perna viridis under ocean acidification’Changes in gill neuroepithelial cells and morphology of threespine stickleback (Gasterosteus aculeatus) to hypoxia and simulated ocean acidification
Published 7 August 2024 Science ClosedTags: abundance, biological response, chemistry, fish, laboratory, morphology, North Pacific, otherprocess, physiology, respiration
Coastal marine environments are characterized by daily, seasonal and long-term changes in both O2 and CO2, driven by local biotic and abiotic factors. The neuroepithelial cells (NECs) of fish are thought to be the putative chemoreceptors for sensing oxygen and CO2, and, thus, NECs play a key role in detecting these environmental changes. However, the role of NECs as chemosensors in marine fish remains largely understudied. In this study, the NECs of marine threespine sticklebacks (Gasterosteus aculeatus) were characterized using immunohistochemistry. We then determined if there were changes in NEC size and density, and in gill morphology in response to either mild (10 kPa) or moderate (6.8 kPa) hypoxia and two levels of elevated CO2 (1,500 and 3,000 µatm). We found that the NECs of stickleback contained synaptic vesicles and were innervated, and were 50–300% larger and 2 to 4 times more abundant than in other similar sized freshwater fishes. NEC size and density were largely unaffected by exposure to hypoxia, but there was a 50% decrease in interlamellar cell mass (ILCM) in response to mild and moderate hypoxia. NECs increased in size, but not abundance in response to elevated CO2. Moreover, fish exposed to moderate or elevated CO2 had 53–78% larger ILCMs compared to control fish. Our results demonstrated that adult marine sticklebacks have NECs that can respond to environmentally relevant pCO2 and likely hypoxia, which highlights the importance of NECs in marine fishes under the heterogeneity of environmental conditions in coastal areas.
Continue reading ‘Changes in gill neuroepithelial cells and morphology of threespine stickleback (Gasterosteus aculeatus) to hypoxia and simulated ocean acidification’Organic matter decay and bacterial community succession in mangroves under simulated climate change scenarios
Published 24 July 2024 Science ClosedTags: abundance, biological response, BRcommunity, chemistry, community composition, laboratory, molecular biology, morphology, otherprocess, physiology, prokaryotes, sediment, South Atlantic
Mangroves are coastal environments that provide resources for adjacent ecosystems due to their high productivity, organic matter decomposition, and carbon cycling by microbial communities in sediments. Since the industrial revolution, the increase of Greenhouse Gases (GHG) released due to fossil fuel burning led to many environmental abnormalities such as an increase in average temperature and ocean acidification. Based on the hypothesis that climate change modifies the microbial diversity associated with decaying organic matter in mangrove sediments, this study aimed to evaluate the microbial diversity under simulated climate change conditions during the litter decomposition process and the emission of GHG. Thus, microcosms containing organic matter from the three main plant species found in mangroves throughout the State of São Paulo, Brazil (Rhizophora mangle, Laguncularia racemosa, and Avicennia schaueriana) were incubated simulating climate changes (increase in temperature and pH). The decay rate was higher in the first seven days of incubation, but the differences between the simulated treatments were minor. GHG fluxes were higher in the first ten days and higher in samples under increased temperature. The variation in time resulted in substantial impacts on α-diversity and community composition, initially with a greater abundance of Gammaproteobacteria for all plant species despite the climate conditions variations. The PCoA analysis reveals the chronological sequence in β-diversity, indicating the increase of Deltaproteobacteria at the end of the process. The GHG emission varied in function of the organic matter source with an increase due to the elevated temperature, concurrent with the rise in the Deltaproteobacteria population. Thus, these results indicate that under the expected climate change scenario for the end of the century, the decomposition rate and GHG emissions will be potentially higher, leading to a harmful feedback loop of GHG production. This process can happen independently of an impact on the bacterial community structure due to these changes.
Continue reading ‘Organic matter decay and bacterial community succession in mangroves under simulated climate change scenarios’Impact of ocean acidification on the intestinal microflora of Sinonovacula constricta
Published 23 July 2024 Science ClosedTags: abundance, biological response, BRcommunity, chemistry, community composition, laboratory, molecular biology, mollusks, morphology, North Pacific, otherprocess, physiology, prokaryotes
The intestinal microflora of host, vital for nutrient absorption and immune regulation, can experience dysbiosis under environmental stress, thereby potentially enhancing host susceptibility to pathogenic invasion. The impact of ocean acidification on bivalves is substantial, yet its effects on the intestinal microflora remain poorly understood. This study employed high-throughput 16S rRNA sequencing technology to investigate the variations in the intestinal microflora of Sinonovacula constricta between the control group (CON) and the seawater acidification group (OA) at different time points.After exposure to OA, changes in the composition of the intestinal microflora of S. constricta were observed, with no significant difference in α-diversity between the acidified and control groups. At the phylum level, there was an increase in the abundance of Proteobacteria, while Cyanobacteria decreased in the OA14d and OA35d groups. Additionally, the relative abundance of Firmicutes increased in the OA7d and OA35d groups. At the genus level, the relative content of Pseudomonas was lower than that in the control group, while the relative content of Flavobacterium, Acinetobacter, and Enterobacter showed a gradual increasing trendin the OA14d and OA35d groups.. LEfSe analysis identified Serpens as discriminative biomarkers in the OA7d group, while Enterobacteriales, Rhodobacteraceae and Martvita were biomarker in the OA14d group, and Serpens, Acidibacteria and Aeromonadaceae were biomarker in the OA35d group. Functional prediction results indicated significant enrichment in metabolic pathways at different time points following ocean acidification stress… The pathways involved in biosynthesis in the OA14d group and in sucrose degradation in the OA35d group were significantly disrupted. These results suggest that OA stress can have adverse effects on the intestinal microflora of S. constricta, but it does not cause obvious damage to the digestive system. This study provides new insights into the intestinal microflora of marine bivalves under acidification stress.
Continue reading ‘Impact of ocean acidification on the intestinal microflora of Sinonovacula constricta’Shellfish CO2 excretion is modulated by seawater carbonate chemistry but largely independent of pCO2
Published 19 July 2024 Science ClosedTags: biological response, BRcommunity, chemistry, laboratory, mollusks, morphology, North Pacific, respiration
Four species of shellfish, blue mussel (Mytilus galloprovincialis), Pacific abalone (Haliotis discus hannai), zhikong scallops (Chlamys farreri), and Pacific oyster (Crassostrea gigas), were exposed to decoupled carbonate system variables to investigate the impacts of different seawater carbonate parameters on the CO2 excretion process of mariculture shellfish. Six experimental groups with two levels of seawater pH (pH 8.1 and pH 7.7) and three levels of total alkalinity (TA = 1000, 2300, and 3600 μmol/kg, respectively) were established, while pH 8.1 and TA = 2300 μmol/kg was taken as control. Results showed that the CO2 excretion rates of these tested shellfish were significantly affected by the change in carbonate chemistry (P < 0.05). At the same TA level, animals incubated in the acidified group (pH 7.7) had a lower CO2 excretion rate than those in the control group (pH 8.1). In comparison, at the same pH level, the CO2 excretion rate increased when seawater TA level was elevated. No significant correlation between the CO2 excretion rate and seawater pCO2 levels (P > 0.05) was found; however, a significant correlation (P < 0.05) between CO2 excretion rate and TA-DIC (the difference between total alkalinity and dissolved inorganic carbon) was observed. Blue mussel has a significantly higher CO2 excretion rate than the other three species in the CO2 excretions per unit mass of soft parts, with no significant difference observed among these three species. However, in terms of CO2 excretion rate per unit mass of gills, abalone has the highest CO2 excretion rate, while significant differences were found between each species. Our studies indicate that the CO2 buffering capacity impacts the CO2 excretion rate of four shellfish species largely independent of pCO2. Since CO2 excretion is related to acid–base balancing, the results imply that the effects of other carbonate parameters, particularly the CO2 buffering capacity, should be studied to fully understand the mechanism of how acidification affects shellfish. Besides, the species difference in gill to soft parts proportion may contribute to the species difference in responding to ocean acidification.
Continue reading ‘Shellfish CO2 excretion is modulated by seawater carbonate chemistry but largely independent of pCO2’Symbiosis under stress: unraveling the interplay of ocean acidification and rising temperatures on Acropora Samoensis (staghorn coral)
Published 18 July 2024 Science ClosedTags: biological response, BRcommunity, chemistry, corals, laboratory, morphology, multiple factors, physiology, protists, temperature
This experiment explores the response of marine organisms to the combined effects of ocean acidification and rising temperatures, with a focus on coral reef ecosystems. As global climate change threatens profound declines in coral reefs, understanding the multifaceted impacts of these stressors becomes crucial. The study observes cellular changes in A. samoensis tissues in four different groups, including control, Temp, pH, and Temp and pH. Results indicate significant breakdown of membrane compartmentalization and cell junctions, with notable degradation and calcium carbonate crystallization in pH-stressed samples. Additionally, chlorophyll extraction data support coral bleaching due to the expulsion of zooxanthellae. These findings underscore the severe impact of pH and temperature variations on coral health, with pH conditions exhibiting a stronger effect. The study concludes by proposing a follow-up experiment involving the addition of carbon-fixing plants to mitigate environmental stressors and enhance coral resilience, aiming to contribute to the conservation of coral reef ecosystems in the face of climate change challenges.
Continue reading ‘Symbiosis under stress: unraveling the interplay of ocean acidification and rising temperatures on Acropora Samoensis (staghorn coral)’From individual calcifiers to ecosystem dynamics: ocean acidification effects on urchins and abalone
Published 16 July 2024 Science ClosedTags: biological response, BRcommunity, chemistry, echinoderms, laboratory, mollusks, morphology, physiology
A central question in ecology is: to what extent do trophic interactions govern the structure and function of communities? This question is becoming more pressing as trophic interactions shift with rapid climate change. Sea urchins and abalone are key invertebrates in the habitats in which they reside. Sea urchins are critical members of exemplar trophic cascades in kelp forests due to their impact on kelp establishment and maintenance; yet their populations are controlled by predators, such as sea otters and sunflower sea stars. Abalone compete with urchins for macroalgal food resources and therefore can help regulate urchin populations in kelp forests. Given that both urchin tests and abalone shells used for predator defense are comprised of calcium carbonate, much research has been conducted on the impacts of ocean acidification (OA) on these calcified structures. A growing body of literature has shown that urchin tests are less calcified and break with less force under OA conditions. Less is known about abalone, but their shells also appear to respond negatively to OA. Using kelp forest communities as exemplar ecosystems, we discuss the morphological, biomechanical, and physiological responses to OA in urchins and abalone and consider how these individual level responses scale to trophic interactions and ultimately whole ecosystem processes. Although the impacts of OA on the calcified structures used for defense have been well studied, calcified mechanisms for food consumption, such as the Aristotle’s lantern of urchins, are much less understood. Thus, examining both the feeding and defense sides of trophic interactions would greatly improve our understanding of OA responses across individual to ecosystem level scales. More generally, measurements of morphological, biomechanical, and physiological responses to OA can be made in individuals to help predict higher level ecological responses, which would greatly contribute to broader predictions of whole ecosystem responses to OA.
Continue reading ‘From individual calcifiers to ecosystem dynamics: ocean acidification effects on urchins and abalone’Antioxidant and metabolic response to acute acidification stress of juvenile yellowfin tuna (Thunnus albacares)
Published 12 July 2024 Science ClosedTags: biological response, chemistry, fish, laboratory, morphology, North Pacific, physiology
This study aimed to explore the impact of acute acidification on the antioxidant, metabolic performance, and liver histology of juvenile yellowfin tuna. The experiment subjected juvenile yellowfin tuna to a pH gradient environment of 8.1, 7.6, 7.1, and 6.6 for 48 h. The findings indicate that a seawater pH of 7.1 significantly impacts the antioxidant and metabolic systems of the juvenile yellowfin tuna in comparison to the control group. At pH 7.1, there were observed increases in glutathione reductase (GR), total antioxidant capacity (T-AOC), lactate dehydrogenase (LDH), hexokinase (HK), pyruvate kinase (PK), sodium-potassium ATPase (Na+K+-ATP), and calcium-magnesium ATPase (Ca2+Mg2+-ATP). Conversely, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and triglycerides (TGs) were not significantly different across the treatment groups. However, an increase in transaminases at pH 7.1 suggested potential liver damage, which was further supported by observed structural liver tissue degeneration and hepatocyte vacuolation. In conclusion, under conditions of acute acidification stress, there is a decrease in antioxidant capacity and a suppression of metabolic levels in juvenile yellowfin tuna, leading to oxidative damage. This study lays the foundation for an in-depth understanding of the response mechanisms of juvenile yellowfin tuna in response to seawater acidification as well as healthy tuna farming in the broader context of seawater acidification.
Continue reading ‘Antioxidant and metabolic response to acute acidification stress of juvenile yellowfin tuna (Thunnus albacares)’Long-term effects of ocean acidification and its interaction with warming on calcifying organisms and their associated microbiome: bryozoans as emerging sentinels of global change?
Published 4 July 2024 Science ClosedTags: biological response, BRcommunity, bryozoa, chemistry, laboratory, Mediterranean, molecular biology, morphology, physiology
Global ocean warming and acidification are two of the major threats to many marine calcifying habitat-forming species, potentially affecting entire ecosystems. Consequently, the need for a better understanding and predicting the response of marine calcifiers has never been more pressing. Paradoxically, the individual and combined long-term effects of these stressors on bryozoans have remained largely unexplored, despite their great abundance and diversity globally. Here, we first evaluate the changes in skeletal structure and mineralogy, and the associated microbiome composition on the populations of Pentapora ottomuelleriana (encrusting) and Myriapora truncata (erect) bryozoan species living inside and outside a volcanic CO2 vent in Ischia Island. We then examine the effects of a long-term exposure to elevated pCO2 and its combined effects of ocean warming on the proportion of cover of populations of the encrusting species through time after summer. Both bryozoan species show indicators of acclimatization by adjusting skeletal properties and having stable microbial communities under acidification conditions. However, we document novel patterns about microbiome shifts in response to future ocean acidification in bryozoans for the first time. Microbial genera known to have essential functions to the host such as biosynthesis of defense compounds or thermal protection were depleted at the acidified site, which suggest early warnings of potential deterioration of bryozoan health under near future ocean conditions. The proportion of cover of the encrusting species also decreased from 2016 to 2020 in both studied sites, with faster declines at the acidified ones. Our model suggests that the increasing seawater temperature drove a decline in the bryozoan cover although the combined effects with acidification accelerated its mortality rates in the CO2 vent. More multidisciplinary research combining both environmental stressors on a wider range of calcifying species is needed to better understand the adaptive capacity of the holobiont to a changing environment.
Continue reading ‘Long-term effects of ocean acidification and its interaction with warming on calcifying organisms and their associated microbiome: bryozoans as emerging sentinels of global change?’Intraspecific variation in response to elevated pCO2 and temperature in the branching reef coral Acropora digitifera from different habitats
Published 27 June 2024 Science ClosedTags: biological response, BRcommunity, calcification, chemistry, corals, laboratory, morphology, mortality, multiple factors, North Pacific, photosynthesis, protists, temperature
Ocean acidification (OA) and ocean warming (OW) affect the calcification of corals, and intraspecific variations in response to these stressors in the population level need to be clarified for better future predictions. Using Acropora digitifera as our subject, we examined the intraspecific variability in calcification and maximum quantum yield (Fv/Fm) of photosystem II of symbiotic zooxanthella in responses to OA, OW, and OA + OW. Samples were taken from two different sites: Sesoko Station (warmer) and Sesoko South (cooler) in Okinawa, Japan. Calcification rates varied between the two sites, and noticeable differences were observed only among coral colonies from the Sesoko South site, specifically under control and OA treatments. Furthermore, Fv/Fm showed no variation between the sites due to those stresses. Hence, the calcification rates among A. digitifera colonies varied by habitat, and we found within-site variation only in the lower temperature location, Sesoko South. We observed diminished variation in response among colonies in the warmer site. The adapting to diverse environmental conditions and responding to changes such as seawater pCO2 and temperature, may lead to differences in sensitivity between the two populations to OA, OW, and OA + OW. These intraspecific variation could arise from factors like acclimatizations, the influence of specific genotypes, or phenotypic plasticity of the colonies.
Continue reading ‘Intraspecific variation in response to elevated pCO2 and temperature in the branching reef coral Acropora digitifera from different habitats’Taphonomy and aleoecology of lycoptera: a case study from the lower jehol group in Western Liaoning, Northeastern China
Published 27 June 2024 Science ClosedTags: biogeochemistry, biological response, fish, laboratory, morphology, North Pacific, paleo
Taphonomy and paleoecology (biological behavior) of the Early Cretaceous fish fossils are poorly described. This study reports for the first time a detailed taphonomical and paleoecological study on Lycoptera in the Mesozoic strata of western Liaoning Province, NE China. The XRD analysis shows that gismondine is the dominant clay minerals that could have contributed to the preservation of Lycoptera fossils and microbial mat fragments in the fossil-bearing horizon. Gismondine may have formed under volcanism-related hydrothermal regime that was transformed from crystal and lithic fragments. The μ-XRF imaging analysis shows a dominant chemical composition of Al, Si, P, S, Rh, K, Ca, Ti, C, Cr, Mn, Fe, Ni, among which P, Ca, C and S are enriched in the fish skeleton in comparison to the matrix. This suggests a dominant apatite composition for the fish skeleton. Hydrothermal influence did not smear off these organic signals probably because of protection of gismondine. The coexistance of C and S with Ni is assumed to represent recovered primary productivity following volcanic explosions and toxic gas emissions. The head of juvenile fish stays close to the body of adult fish. Pending further discoveries, such phenomenon is interpreted to suggest that adult fish actively protected juvenile fish in the presence of environmental pressures such as anoxia and deterioration of water quality induced by volcanism. Ocean acidification and hypoxia in association with volcanism created a harmful environment causing mass extinction of fish. The adult Lycoptera protected their juveniles by its body at the moment before death. Such biological behavior will be increasingly reported given the wide occurrence of Lycoptera in Mesozoic strata.
Continue reading ‘Taphonomy and aleoecology of lycoptera: a case study from the lower jehol group in Western Liaoning, Northeastern China’
