The impacts of climate change-related stressors are becoming more noticeable in the ocean, particularly in coastal marine ecosystems. Yet limited information still exists on the physiological state and ecological resilience of marine fish species, especially during their early life stages (i.e., larvae and juveniles). The present study investigated the effects of chronic exposure to seawater warming (OW; ΔT = +4 °C) and acidification (OA; ΔpH = −0.3 pH units, equivalent to pCO2~1000 µatm), acting alone or combined (OWA), on juvenile zebra seabream (Diplodus cervinus) physiological resilience, considering distinct levels of biological organization (i.e., biochemical, cell, organ and individual levels). After 60 days of exposure, both stressors, in isolation or combination, significantly decreased specific growth rate (−11% in OW, −42% in OA and −49% in OWA) and leukocyte counts (from −29% in OA and OWA up to −37% in OW) in relation to the control treatment. In addition, a decreased Fulton’s condition index (K) was observed under warming and acidification in combination (−35% in OWA). At the cell level, OW, OA and OWA triggered different biomarker responses in D. cervinus (i.e., up-regulation, down-regulation, or absence of significant effect). In general, the results are suggestive of an antagonistic effect when warming and acidification are combined. OWA yielded the highest integrated biomarker response (IBR) index value in the whole organism, muscle, brain and gills of D. cervinus juveniles, therefore suggesting that the effects of these stressors are more severe when they act together. The distinct patterns observed in each stress scenario highlight the importance of carrying out further studies adjusted to the specificities of different regions, i.e., accounting not only for the type and degree of severity of environmental stressors already felt and/or projected for that specific area, but also the physiological plasticity of species that inhabit a particular ecosystem. The gathered knowledge will allow one to determine the vulnerability of particular marine species and geographic areas and, most importantly, to draw up effective and tailor-made conservation strategies to overcome climate change impacts.
Continue reading ‘Integrated multi-biomarker responses of juvenile zebra seabream (Diplodus cervinus) to warming and acidification conditions’Posts Tagged 'growth'
Integrated multi-biomarker responses of juvenile zebra seabream (Diplodus cervinus) to warming and acidification conditions
Published 29 August 2024 Science ClosedTags: biological response, chemistry, fish, growth, laboratory, mortality, multiple factors, North Atlantic, performance, physiology, reproduction, temperature
Using high CO2 concentrations to culture microalgae for lipid and fatty acid production: synthesis based on a meta-analysis
Published 27 August 2024 Science ClosedTags: biological response, chemistry, growth, phytoplankton, review
Highlights
- Higher CO2 concentrations commonly promote microalgal growth and lipid accumulation.
- High CO2 levels increase lipid productivity of both freshwater and marine microalgae.
- High CO2 levels reduce saturated fatty acid content of microalgae.
- Unsaturated fatty acid content of microalgae is stimulated by high CO2.
- Content of EPA and DHA is promoted by high CO2, particularly for marine microalgae.
Abstract
To gain a comprehensive understanding of cultivating microalgae for lipid and fatty acid production with high CO2, this study conducted a meta-analysis based on 757 data sets from 51 papers for the first time. The findings show that high CO2 concentrations (0.1–30%) generally promote microalgal growth, whereas extreme high CO2 levels (30–50%) usually exhibit negative effects. High CO2 levels (0.1–30%) also commonly stimulate cellular lipid accumulation. Therefore, high CO2 levels (0.1–50%) increase lipid productivity of both freshwater and marine microalgae, particular for Chlorophytina. These elevated CO2 levels (0.1–30%) reduce saturated fatty acid content of microalgae but enhance the content of unsaturated and polyunsaturated fatty acids, including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Advanced molecular editing techniques, e.g., CRISPR-Cas9, can be utilized to improve microalgal tolerance to flue gases that contain hazardous compounds while condition optimalization for maximal use of CO2 in the production of microalgae with high lipid content should also be conducted in future. This research provides crucial insights for designing and optimizing microalgae cultivation with high CO2 to produce lipid and fatty acids.
Continue reading ‘Using high CO2 concentrations to culture microalgae for lipid and fatty acid production: synthesis based on a meta-analysis’Impact of fluctuating temperature and elevated CO2 on the growth, survival, and oxygen consumption of juvenile pinto abalone Haliotis kamtschatkana kamtschatkana Jonas
Published 22 August 2024 Science ClosedTags: biological response, chemistry, growth, laboratory, mollusks, mortality, North Pacific, performance, physiology, respiration
Pinto abalone populations in the Salish Sea, WA have declined precipitously in the last several decades and have not recovered despite fishery closure in 1994. The Puget Sound Restoration Fund, in collaboration with state and federal agencies, has been outplanting juvenile pinto abalone at sites in the San Juan Archipelago, and some sites are much more successful than others despite similar physical characteristics. The sites, however, likely differ in oceanic parameters, such as temperature, salinity, and pH, which are in turn changing as the climate of the Earth is changing. The purpose of this study was to investigate the effects of temperature fluctuation and pCO2 levels on the survival, growth, and oxygen consumption of juvenile pinto abalone. In a fully crossed experiment, juvenile pinto abalone were held at either currently ambient (400 ppm) or elevated (1,200 ppm) pCO2 and at constant (10°C) or fluctuating (10 → 14 → 10°C) temperature. Survival was monitored weekly and growth was measured after 4 wk. In a second experiment, abalone were held in the same crossed pCO2 and temperature treatments, and oxygen consumption was measured. High pCO2 and fluctuating temperature both significantly decreased abalone survival. Abalone growth was not affected by pCO2 level (temperature could not be analyzed due to very poor survival in the fluctuating temperature treatments). In addition, there was an interaction between fluctuating temperature and pCO2 level on abalone oxygen consumption. Abalone in the constant temperature treatment had higher oxygen consumption when exposed to elevated pCO2; however, this pattern was not observed in the fluctuating temperature treatment. The results of this experiment indicate that outplant sites with minimal temperature fluctuation and lower pCO2 levels could lead to improvements in outplanting success of juvenile pinto abalone.
Continue reading ‘Impact of fluctuating temperature and elevated CO2 on the growth, survival, and oxygen consumption of juvenile pinto abalone Haliotis kamtschatkana kamtschatkana Jonas’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’Coupling effects of CO2-induced ocean acidification and nitrogen enrichment on growth, photosynthesis and nitrogen utilization of an invasive seaweed (Sargassum muticum)
Published 8 August 2024 Science ClosedTags: algae, biogeochemistry, biological response, chemistry, growth, laboratory, North Pacific, otherprocess, photosynthesis
Highlights
- Ocean acidification promotes growth of Sargassum muticum.
- Both ocean acidification and enrichment of NO3−−N increase photosynthesis of Sargassum muticum.
- Ocean acidification and NO3−−N enrichment non-synergistically enhance invasiveness of S. muticum.
Abstract
Sargassum muticum, an invasive seaweed, has colonized many parts of the world along the coast. Marine environment invaded by this species is aggravated the complexity by CO2-induced ocean acidification (OA) and coastal eutrophication. However, the coupling effects of seawater acidification and eutrophication on this invasive species remain unclear. In this study, we cultured Sargassum muticum at two concentrations of pCO2 (420 ppmv, LC and 1000 ppmv, HC) and nitrate (10 μM, LN and 200 μM, HN) for 16 days, to investigate the coupling effects of CO2-induced seawater acidification and nitrate enrichment on growth and photosynthesis of Sargassum muticum. The results showed that high CO2 increased the relative growth rate (RGR) of alga by 58.9% under LN condition, while such increment was not found under HN condition. Thus, the highest RGR was emerged in the HCLN treatment. The photosynthetic rate curve under different inorganic carbon concentrations (P
C curve) presented that high CO2 increased the maximum inorganic carbon utilization rate (Vmax) by 8.1% under HN condition; while inhibited it by 29.8% under LN condition. The affinity to inorganic carbon, reflected by the half-saturation constant (K0.5), was improved significantly by high CO2 and/or high nitrate, compared with LCLN treatment. The photosynthetic rate curves under different irradiances (PI curve) suggested that the maximum photosynthetic rate (Pmax) of alga was enhanced remarkably by high N, and kept unaffected by high CO2. The lowest value of dark respiration rate (Rd) was found in HCLN treatment, and there was no significant difference among the other three treatments. Additionally, an increase chlorophyll a content caused by high N was only found in HC treatment. After 16 d culture, nitrate reductase activity (NRA) of algae in HN treatments decreased significantly, compared with those in LN treatments. Furthermore, high CO2 enhanced NRA dramatically only in algae grown at LN level. Correspondingly, the lowest nitrate uptake rate (NUR) was found in LCHN treatment, and there was no significant difference among the other three treatments. In conclusion, our results showed that elevated CO2 enhanced the RGR, and the coupling of high CO2 and nitrate affected the photosynthesis and NUR, however did not synergistically promote growth of S. muticum. Therefore, we speculate that the future OA may exacerbate the invasiveness of S. muticum; nevertheless, the eutrophication of seawater would not amplify this effect.
High light intensity and CO2 enrichment synergistically mitigated the stress caused by low salinity in Pyropia yezoensis
Published 7 August 2024 Science ClosedTags: algae, biological response, chemistry, growth, laboratory, light, multiple factors, North Pacific, photosynthesis, physiology, salinity
Macroalgae, playing a crucial role in coastal marine ecosystems, are subject to multiple environmental challenges due to tidal and seasonal alterations. In this work, we investigated the physiological responses of Pyropia yezoensis to ocean acidification (ambient CO2 (AC: 400 μatm) and elevated CO2 (HC: 1000 μatm)) under changing salinity (20, 30 psu) and light intensities (50, 100 μmol photons m−2 s−1) by measuring the growth, pigment content, chlorophyll fluorescence, and soluble sugar content. The key results are the following: (1) P. yezoensis exhibited better growth under normal salinity (30 psu) compared to hyposaline conditions (20 psu). (2) Intermediate light intensity increased phycoerythrin content, ultimately enhancing thalli growth without significant changes to the contents of chlorophyll a and carotenoids. (3) Ocean acidification alleviated hyposaline stress by enhancing pigment production in P. yezoensis only at a salinity of 20 psu, highlighting the complex interplay of these environmental factors. These findings indicate that higher light intensities and elevated pCO2 levels could mitigate the stress caused by low salinity.
Continue reading ‘High light intensity and CO2 enrichment synergistically mitigated the stress caused by low salinity in Pyropia yezoensis’Modelling the multiple action pathways of projected climate change on the Pacific cod (Gadus macrocephalus) early life stages
Published 23 July 2024 Science ClosedTags: biological response, chemistry, fish, growth, individualmodeling, modeling, mortality, North Pacific
Highlights
- We used projections of oceanographic conditions and an individual-based model (IBM) to study the impacts of climate on the early life stages of Pacific cod in the eastern Bering Sea from 2021 to 2100.
- Besides temperature and prey density, we also examined the impacts of ocean acidification on some biological aspects of cod larvae.
- We found that a high CO2 emission scenario (RCP8.5) may increase starvation events and decrease cod survival, while the moderate CO2 emission scenario (RCP4.5) may not produce significant impacts.
- We identified a retention area in the southeastern Bering Sea that may provide a refuge for larval cod under future environmental conditions.
- Our IBM can be used for other gadids in the same region to study the impacts of projected climate conditions on early life stages.
Abstract
Understanding how future ocean conditions will impact early life stages and population recruitment of fishes is critical for adapting fisheries communities to climate change. In this study, we incorporated projected changes in physical and biological ecosystem dynamics from an oceanographic model into a mechanistic individual-based model for larval and juvenile stages of the Pacific cod (Gadus macrocephalus) in the eastern Bering Sea. We particularly investigated the impacts of ocean currents, temperature, prey density, and pCO2 on the hatching success, growth, survival, and spatial distribution of this species during 2021–2100. We evaluated two CO2 emission scenarios: RCP8.5 (high CO2 emissions, low mitigation efforts) and RCP4.5 (medium CO2 emissions and mitigation efforts). We found that the increase in temperature and decrease in prey density were the main drivers of faster growth rates and lower survival through increased starvation by the end of the century. Conversely, pCO2 had negligible impacts, which suggests that this species might be resilient to ocean acidification. The largest effects were observed under the high CO2 emission scenario, while the RCP4.5 projections displayed minimal impacts. We also identified an area with favourable conditions in the southeastern Bering Sea that will likely persist in future decades. This study provides relevant information on the future impacts of climate change on Pacific cod, and our results can be used to implement and inform climate-ready management for this important stock in Alaska.
Continue reading ‘Modelling the multiple action pathways of projected climate change on the Pacific cod (Gadus macrocephalus) early life stages’Uptake of dissolved inorganic nitrogen and N2 fixation by Crocosphaera watsonii under climate change scenarios
Published 22 July 2024 Science ClosedTags: abundance, biological response, chemistry, growth, laboratory, multiple factors, nitrogen fixation, otherprocess, physiology, prokaryotes, temperature
The response of N2 fixation to projected future conditions in the ocean cannot be reliably predicted to date. We conducted a minicosm experiment with pre-acclimated cultures of the globally significant diazotroph Crocosphaera watsonii strain WH8501 (“Crocosphaera”). PH and temperature were altered simultaneously to match the RCP scenarios 4.5 and 6 and investigate a more realistic future scenario compared to studies that focus on changes of a single stressor only. The cell abundance and nitrogen metabolism of Crocosphaera was monitored over 5 days. Our results imply that Crocosphaera is able to simultaneously perform N2 fixation and assimilate dissolved inorganic nitrogen (DIN, i.e., nitrate and ammonium) under all the conditions tested and implies a competition with non-diazotrophic phytoplankton for DIN, which should be further investigated. Using NanoSIMS analysis of single cells, our results point towards a preference for DIN assimilation over N2 fixation under more acidic and warmer conditions. Overall, our results show that while the combined alteration of pH and temperature had a negative effect on the diazotroph’s growth and N2 fixation, Crocosphaera is likely to cope well with conditions in the future ocean. The high intra-population variability in nitrogen assimilation pathways may give this species the flexibility to quickly react to environmental changes.
Continue reading ‘Uptake of dissolved inorganic nitrogen and N2 fixation by Crocosphaera watsonii under climate change scenarios’Effects of elevated pCO2 on bioenergetics and disease susceptibility in Pacific herring Clupea pallasii
Published 17 July 2024 Science ClosedTags: biological response, chemistry, fish, growth, laboratory, mortality, North Pacific, performance, physiology, reproduction
Ocean acidification can affect the immune responses of fish, but effects on pathogen susceptibility remain uncertain. Pacific herring Clupea pallasii were reared from hatch under 3 CO2 partial pressure ( pCO2) treatments (ambient, ∼650 µatm; intermediate, ∼1500 µatm; high, ∼3000 µatm) through metamorphosis (98 d) to evaluate the effects of ocean acidification on bioenergetics and susceptibility to an endemic viral disease. Mortality from viral hemorrhagic septicemia (VHS) was comparable between herring reared under ambient and intermediate pCO2 (all vulnerability testing at ambient pCO2). By contrast, fish reared under high pCO2 experienced significantly higher rates of VHS mortality, and the condition factor of survivors was significantly lower than in the other pCO2 treatments. However, the prevalence of infection among survivors was not influenced by pCO2 treatment. Pre-flexion larval development was not affected by elevated pCO2, as growth rate, energy use, and feeding activity were comparable across treatments. Similarly, long-term growth (14 wk) was not affected by chronic exposure to elevated pCO2. Herring reared under both elevated pCO2 treatments showed an average reduction in swimming speed; however, wide intra-treatment variability rendered the effect nonsignificant. This study demonstrates that the VHS susceptibility and bioenergetics of larval and post-metamorphic Pacific herring are not affected by near-future ocean acidification predicted for coastal systems of the North Pacific. However, increased susceptibility to VHS in fish reared under 3000 µatm pCO2 indicates potential health and fitness consequences from extreme acidification.
Continue reading ‘Effects of elevated pCO2 on bioenergetics and disease susceptibility in Pacific herring Clupea pallasii’CO2-induced seawater acidification impairs the stinging cells of a jellyfish
Published 12 July 2024 Science ClosedTags: biological response, chemistry, cnidaria, growth, laboratory, molecular biology, performance, physiology
CO2-induced seawater acidification has been shown to modify predator–prey interactions in many marine taxa. Scyphozoans play an important role in the trophic dynamics of marine ecosystems during their blooms in coastal waters; however, the impacts of seawater acidification on the predation behavior of these animals are poorly understood. Here, we aimed to examine the impact of a decrease in seawater pH on the feeding behavior and growth of ephyrae (juvenile medusae) of the scyphozoan Aurelia coerulea. Combining bulk and single-cell RNA sequencing approaches, we assessed transcriptomic changes of ephyrae under a laboratory-based pH 7.6 condition. We found that the feeding rates and growth of ephyrae were significantly inhibited by a decrease in seawater pH. Furthermore, transcriptome analysis showed that a decline in pH significantly reduced the expression of genes related to toxins and nematocyst structure in ephyrae. These findings were further confirmed by single-cell transcriptomic analyses and revealed that low pH impaired the toxin activity and energy metabolism of stinging cells. The pH recovery experiment indicated that moving ephyrae from seawater with pH 7.6 into seawater with pH 8.1 greatly restored their feeding, growth, and toxin-related and nematocyst structure–related gene expression. However, exposure to pH 7.6 for 23 d could not recover the decrease in the feeding and growth of ephyrae. Together, these findings indicate that CO2-induced acidification compromised the stinging cells of A. coerulea ephyrae, with concomitant negative consequences on predation and growth that are likely to alter predator–prey interactions, with consequent effects on community structure and ecosystem.
Continue reading ‘CO2-induced seawater acidification impairs the stinging cells of a jellyfish’Acidification alleviates the inhibition of hyposaline stress on physiological performance of tropical seagrass Thalassia hemprichii
Published 4 July 2024 Science ClosedTags: biological response, chemistry, growth, laboratory, North Pacific, phanerogams, photosynthesis, physiology
Highlights
- Thalassia hemprichii highly adapts to acidification and hyposalinity environments.
- Acidification and hyposalinity had interaction effects on physiology of the seagrass.
- Acidification and hyposalinity had no interaction effects on growth of the seagrass.
- Acidification mitigates the inhibitory effects of hyposaline stress for the seagrass.
Abstract
Since the Industrial Revolution, increasing atmospheric CO2 concentrations have had a substantial negative impact influence on coastal ecosystems because of direct effects including ocean acidification and indirect effects such as extreme rainfall events. Using a two-factor crossover indoor simulation experiment, this study examined the combined effects of acidification and hyposaline stress on Thalassia hemprichii. Seawater acidification increased the photosynthetic pigment content of T. hemprichii leaves and promoted seagrass growth rate. Hyposaline stress slowed down seagrass growth and had an impact on the osmotic potential and osmoregulatory substance content of seagrass leaves. Acidification and salinity reduction had significant interaction effects on the photosynthesis rate, photosynthetic pigment content, chlorophyll fluorescence parameters, and osmotic potential of T. hemprichii, but not on the growth rate. Overall, these findings have shown that the hyposaline stress inhibitory effect on the T. hemprichii physiological performance and growth may be reduced by acidification.
Continue reading ‘Acidification alleviates the inhibition of hyposaline stress on physiological performance of tropical seagrass Thalassia hemprichii’Interactive effects of ocean acidification and nitrate on Ulva lactuca
Published 2 July 2024 Science ClosedTags: algae, biological response, chemistry, growth, laboratory, multiple factors, nutrients, photosynthesis, respiration
The global ocean is undergoing gradual acidification and eutrophication which may have significant impacts on macroalgal communities. However, little is known regarding the interactive effects of ocean acidification (OA) and nitrate on Ulva lactuca, a primary producer widely distributed in coastal waters. This study focuses on the possible interactive effects of OA and elevated nitrate levels on physiological parameters of U. lactuca. Higher nitrate levels may increase growth, photosynthesis, respiration, pigment synthesis, Fv/Fm and Effective Quantum Yield, whereas CO2 enrichment may result in a reduction in photosynthesis, pigment content, Fv/Fm and Effective Quantum Yield. Higher nitrate levels increase NO3– uptake rate and nitrate reductase activity, which are further amplified by elevated CO2 levels. However, the stimulation of high nitrate towards pigment synthesis and photosynthesis is negatively affected by elevated CO2 levels. Our results suggest that U. lactuca could potentially increase its biomass in coastal eutrophic waters, and OA in the future is not expected to promote the growth of U. lactuca, but it can enhance its potential biofiltration to remove nitrate from coastal ecosystems.
Continue reading ‘Interactive effects of ocean acidification and nitrate on Ulva lactuca’Predictable patterns within the kelp forest can indirectly create temporary refugia from ocean acidification
Published 20 June 2024 Science ClosedTags: algae, biological response, BRcommunity, chemistry, dissolution, growth, mesocosms, mollusks, morphology, North Pacific
Highlights
- Potential of kelp as ocean acidification refugia has been addressed through an integration of observations, modelling and mesocosm work.
- Kelp did not have a direct mitigating effect against OA in the low retentive habitats.
- Improved biological responses were observed in investigated calcifiers.
- Positive responses were related to increased predictability in pH autocorrelation signal and improved habitat provisioning through resource utilization.
- Kelp can improve ecosystem services
Abstract
Kelps are recognized for providing many ecosystem services in coastal areas and considered in ocean acidification (OA) mitigation. However, assessing OA modification requires an understanding of the multiple parameters involved in carbonate chemistry, especially in highly dynamic systems. We studied the effects of sugar kelp (Saccharina latissima) on an experimental farm at the north end of Hood Canal, Washington—a low retentive coastal system. In this field mesocosm study, two oyster species (Magallana gigas, Ostrea lurida) were exposed at locations in the mid, edge, and outside the kelp array. The Hood Head Sugar Kelp Farm Model outputs were used to identify dominating factors in spatial and temporal kelp dynamics, while wavelet spectrum analyses helped in understanding predictability patterns. This was linked to the measured biological responses (dissolution, growth, isotopes) of the exposed organisms. Positioned in an area of high (sub)-diel tidal fluxes with low retention potential, there were no measurable alterations of the seawater pH at the study site, demonstrating that the kelp array could not induce a direct mitigating effect against OA. However, beneficial responses in calcifiers were still observed, which are linked to two causes: increased pH predictability and improved provisioning through kelp-derived particulate organic resource utilization and as such, kelp improved habitat suitability and indirectly created refugia against OA. This study can serve as an analogue for many coastal bay habitats where prevailing physical forcing drives chemical changes. Future macrophyte studies that investigate OA mitigating effects should focus also on the importance of predictability patterns, which can additionally improve the conditions for marine calcifiers and ecosystem services vulnerable to or compromised by OA, including aquaculture sustainability.
Continue reading ‘Predictable patterns within the kelp forest can indirectly create temporary refugia from ocean acidification’Impact of climate change on carbon and nitrogen balance in Zostera Marina L. (Eelgrass)
Published 14 June 2024 Science ClosedTags: biogeochemistry, biological response, chemistry, growth, laboratory, North Atlantic, phanerogams, physiology
Seagrasses face vulnerability to both global stressors like Ocean Acidification (OA) and climate warming compounded by local stressors such as eutrophication that reduces light availability, leading to a complex dynamic of positive and negative effect on their growth and survival. Increased dissolved aqueous CO2 (CO2(aq)) benefits seagrasses by enhancing photosynthetic and growth rates, but it may increase nutrient demand, potentially depleting nutrient supply, especially in oligotrophic environments. In this study, the long-term impact of CO2 on Zostera marina L. (eelgrass) were investigated across a gradient of CO2(aq) concentrations (55 – 2200 µM CO2(aq)) and leaf area indices (LAI). The focus was on quantify changes in carbon (C) and nitrogen (N) content, composition, and metabolism in response to CO2-stimulated photosynthesis and growth. Absolute growth rates, shoot sizes, leaf density, sucrose concentrations, and carbon and nitrogen growth demands increased with increasing CO2(aq) availability. However, there was no notable decline in biomass-specific N content of leaf at higher CO2(aq) concentrations primarily due to dilution effects caused by carbon accumulation in thicker leaves, rather than N-limitation. Rather than increasing plant survival in the context of CO2(aq) enrichment, this study found that nutrient enrichment of the sediment reduced plant survival as a result of NH4 +toxicity. In contrast, the high H2S concentrations reaching millimolar levels in sediment, which was stimulated by organic carbon addition, was not particularly toxic to eelgrass. CO2 effects on N uptake were complicated by changes in canopy architecture due to increasing leaf area index (LAI), affecting N uptake patterns of leaves and roots. Combining a nutrient uptake model with the radiative transfer GrassLight (v2.14) model, this study explored how CO2-driven photosynthesis affected N uptake patterns and requirements for growth. Model predictions across varying LAIs and CO2(aq) concentrations indicated low N demand for eelgrass under all CO2(aq) conditions, with roots playing a key role in N acquisition as CO2(aq) concentrations increased. Overall, my results highlight the importance of photosynthesis in regulating N metabolism and acquisition between the above- and belowground components, and suggest that most eelgrass meadows are unlikely to experience N limitation, even in high CO2(aq) environments.
Continue reading ‘Impact of climate change on carbon and nitrogen balance in Zostera Marina L. (Eelgrass)’Macroalgal presence decreases coral calcification rates more than ocean acidification
Published 12 June 2024 Science ClosedTags: algae, biological response, BRcommunity, calcification, chemistry, corals, growth, laboratory, mesocosms, morphology, Red Sea
Global coral reef degradation has precipitated phase shifts toward macroalgal-dominated communities. Despite the negative repercussions for reefscapes, higher abundances of primary producers have the potential to positively impact the physicochemical environment and mitigate negative impacts of ocean acidification (OA). In this study, we investigated the influence of macroalgal (cf. Sargassum vulgare) density on coral (Acropora millepora and A. hemprichii) calcification rates under current and future OA conditions. Corals were resistant to OA up to ~ 1100 µatm, with no changes in calcification rates. However, the presence of (low and high density) algae reduced calcification rates by ~ 41.8%, suggesting either a chemical defense response due to algal metabolites or potential physical impacts from shading or abrasion. Documented beneficial buffering effects of macroalgae in OA may also elicit negative impacts on coral calcification, suggesting further work is needed to elucidate how species interactions influence responses to projected climate change.
Continue reading ‘Macroalgal presence decreases coral calcification rates more than ocean acidification’Stochastic modeling of eastern oyster (Crassostrea virginica) production in a Mexican tropical coastal lagoon using alternative stocking density management schemes
Published 5 June 2024 Science ClosedTags: biological response, chemistry, growth, laboratory, methods, mollusks, morphology, North Atlantic
A stochastic model was developed to analyze Crassostrea virginica production when cultivated at three stocking densities, defined as the area occupation (50, 75, and 100%) in Nestier-type trays, using juvenile oysters with an initial size (height) of 29.40 ± 0.18 mm. A 25-week grow-out was first conducted in the Rio Lagartos lagoon, showing that final oyster size was inversely related to density (P < 0.05), ranging from 61.87 mm (100% density) to 68.00 mm (50% density). At the same time, mortality was negligible (lower than 1.0%). The environmental conditions in the lagoon were stable, and the oyster growth rate positively correlated with water temperature and pH. Low pH was associated with slow oyster growth, possibly as an adverse effect of acidic conditions on the oyster shell formation. The model indicated that, for an initial 100,000 oyster population, the maximum production (oyster dozens) is obtained after 20 weeks (8310 at 50% density) and 25 weeks (8250 at 75%, and 6670 at 100% density). There was a 100% probability of oysters reaching a minimum commercial size (MCS) of 60.00 mm when using the 50 and 75% densities and 80.6% when using 100%. The model estimated that, for the maximum density, extending the grow-out up to 32 weeks would allow reaching MCS with 100% probability, although this should be experimentally confirmed. The random variability of oyster production in 50 and 75% densities was minimal, while at 100% density, it was extremely high. A sensitivity analysis indicated that for 50 and 75% densities, the main stochastic elements influencing production, are related to oyster mortality, while at 100% density, they are related to oyster growth.
Continue reading ‘Stochastic modeling of eastern oyster (Crassostrea virginica) production in a Mexican tropical coastal lagoon using alternative stocking density management schemes’Cross-generational plasticity in Atlantic silversides (Menidia menidia) under the combined effects of hypoxia and acidification
Published 28 May 2024 Science ClosedTags: biological response, chemistry, fish, growth, laboratory, molecular biology, morphology, multiple factors, North Atlantic, oxygen, physiology, reproduction
We investigated the potential for cross-generational plasticity to influence how offspring respond to hypoxia and ocean acidification (hereafter HypOA) in the coastal forage fish Atlantic silverside (Menidia menidia). Mature wild silversides were treated with a control [dissolved oxygen (DO):100% air saturation (a.s.) / pCO2: 650 μatm] or HypOA conditions [DO: 40% a.s. / pCO2: 2300 μatm] for 10 days prior to spawning. Their offspring were reared under both treatments in factorial experimental design. Parental acclimation to HypOA altered several offspring traits, including increased embryo survival under HypOA and an overall reduction in post-hatch growth rate. Offspring from HypOA-treated parents that were reared under control conditions had larger eyes across the developmental period. When compared against the overall control group, larvae directly exposed to HypOA exhibited 2,416 differentially expressed transcripts (DETs). Although most of these DETs were specific to individual parental treatments, the most enriched Gene Ontology terms were conserved across parental treatments, including terms related to neurotransmitter secretion, nervous system development, axon pathfinding, calcium channel activity, proteolysis, and extracellular matrix organization. Larvae from HypOA-treated parents that were reared under control conditions exhibited a shift in constitutive gene expression similar to that seen in larvae directly exposed to HypOA. This highly consistent finding indicates that parental acclimation before fertilization promotes the transcriptional frontloading of genes in offspring that are responsive to direct HypOA exposure. This highly consistent finding indicates that parental acclimation before fertilization promotes the transcriptional frontloading of genes in offspring. This effect may have primed regulatory functions in offspring that sense and respond to low DO and elevated pCO2 conditions. Though, our results suggest that this altered developmental phenotype may have some negative fitness consequences for offspring.
Continue reading ‘Cross-generational plasticity in Atlantic silversides (Menidia menidia) under the combined effects of hypoxia and acidification’Drivers of biological response to fluctuating seawater ph conditions in sea urchin echinus esculentus larvae
Published 22 May 2024 Science ClosedTags: adaptation, biological response, chemistry, echinoderms, growth, laboratory, morphology, mortality, North Atlantic, otherprocess, physiology, reproduction
Highlights
- Low pH has a negative effect on sea urchin larval fitness.
- Under fluctuating pH conditions, the minimum pH is not driving the biological response.
- Larvae are pre-adapted to fluctuating conditions and inverting the pH diurnal cycle leads to negative effects on fitness.
- Adaptation to variability in a coastal species is associated with a cost of plasticity but not cost of canalization.
Abstract
A large body of evidence is documenting the impact of reduced pH on marine species and ecosystems. This information is used to infer the present and future impacts of ocean acidification. However, a vast majority of the studies were performed using constant pH and the high level of pH variability experienced by marine organisms on the coastal zone was often overlooked. Recent studies highlight the key role of this variability in driving biological response to pH as well as species sensitivity to ocean acidification. For example, it was hypothesized that because of local adaptation, the extreme of the present range of pH variability is a good predictor for local biological thresholds. Using a complex experimental design, we investigated what part of the pH variability is driving the biological response of the sea urchin Echinus esculentus larvae. Comparing stable (pH 8.13, 7.82, 7.53) and fluctuating treatments (12 h at pH 8.13 and 12 h at pH 7.53) following natural or inverted diurnal cycles, we were able to show that (i) under constant conditions, low pH deviating from the present range of natural variability had a negative effect on larval growth rate and calcification; (ii) under fluctuating conditions, a desynchronization of the pH variation with the photoperiod led to decreased larval growth rate and calcification; (iii) overall, larval fitness (survival, growth and calcification) was higher under fluctuating conditions as compared to constant. While these data do not support the hypothesis that the minimum pH is the main driver of the biological response, they provide evidence of adaptation to variability in a coastal species with associated a cost of plasticity but not a cost of canalization.
Continue reading ‘Drivers of biological response to fluctuating seawater ph conditions in sea urchin echinus esculentus larvae’Impacts of microplastic and seawater acidification on unicellular red algae: growth response, photosynthesis, antioxidant enzymes, and extracellular polymer substances
Published 17 May 2024 Science ClosedTags: abundance, algae, biological response, growth, laboratory, multiple factors, otherprocess, physiology, toxicants
Highlights
- Single and combined effects of MPs and OA on P. purpureum were investigated.
- μm MPs significantly promoted algal growth at concentrations of 5-100 mg L−1.
- 1μm MPs caused negative effect on microalgae at medium and high concentrations.
- Seawater acidification mitigated the impacts of MPs on microalgae.
Abstracts
Microplastics (MPs) pollution and seawater acidification have increasingly become huge threats to the ocean ecosystem. Their impacts on microalgae are of great importance, since microalgae are the main primary producers and play a critical role in marine ecosystems. However, the impact of microplastics and acidification on unicellular red algae, which have a unique phycobiliprotein antenna system, remains unclear. Therefore, the impacts of polystyrene-MPs alone and the combined effects of MPs and seawater acidification on the typical unicellular marine red algae Porphyridium purpureum were investigated in the current study. The result showed that, under normal seawater condition, microalgae densities were increased by 17.75-41.67% compared to the control when microalgae were exposed to small-sized MPs (0.1 μm) at concentrations of 5-100 mg L−1. In addition, the photosystem II and antioxidant enzyme system were not subjected to negative effects. The large-sized MPs (1 μm) boosted microalgae growth at a low concentration of MPs (5 mg L−1). However, it was observed that microalgae growth was significantly inhibited when MPs concentration increased up to 50 and 100 mg L−1, accompanied by the remarkably reduced Fv/Fm value and the elevated levels of SOD, CAT enzymes, phycoerythrin (PE), and extracellular polysaccharide (EPS). Compared to the normal seawater condition, microalgae densities were enhanced by 52.11-332.56%, depending on MPs sizes and concentrations, due to the formed CO2-enrichment condition and appropriate pH range. PE content in microalgal cells was significantly enhanced, but SOD and CAT activities as well as EPS content markedly decreased under acidification conditions. Overall, the impacts of seawater acidification were more pronounced than MPs impacts on microalgae growth and physiological responses. These findings will contribute to a substantial understanding of the effects of MPs on marine unicellular red microalgae, especially in future seawater acidification scenarios.
Continue reading ‘Impacts of microplastic and seawater acidification on unicellular red algae: growth response, photosynthesis, antioxidant enzymes, and extracellular polymer substances’Shark critical life stage vulnerability to monthly temperature variations under climate change
Published 8 May 2024 Science ClosedTags: biological response, fish, growth, laboratory, morphology, multiple factors, North Atlantic, performance, physiology, reproduction, respiration, temperature
Highlights
- Summer temperatures revealed embryo vulnerability to seasonal fluctuations.
- Hatching success ranged from 82% in control and SSP2-4.5 to 11% in SSP5-8.5.
- The death of embryos was preceded by distinct individual growth trajectories.
Abstract
In a 10-month experimental study, we assessed the combined impact of warming and acidification on critical life stages of small-spotted catshark (Scyliorhinus canicula). Using recently developed frameworks, we disentangled individual and group responses to two climate scenarios projected for 2100 (SSP2-4.5: Middle of the road and SSP5-8.5: Fossil-fueled Development). Seasonal temperature fluctuations revealed the acute vulnerability of embryos to summer temperatures, with hatching success ranging from 82% for the control and SSP2-4.5 treatments to only 11% for the SSP5-8.5 treatment. The death of embryos was preceded by distinct individual growth trajectories between the treatments, and also revealed inter-individual variations within treatments. Embryos with the lowest hatching success had lower yolk consumption rates, and growth rates associated with a lower energy assimilation, and almost all of them failed to transition to internal gills. Within 6 months after hatching, no additional mortality was observed due to cooler temperatures.
Continue reading ‘Shark critical life stage vulnerability to monthly temperature variations under climate change’
