Fish are critical ecologically and socioeconomically for subsistence economies in the Arctic, an ecosystem undergoing unprecedented environmental change. Our understanding of the responses of nearshore Arctic fishes to environmental change is inadequate because of limited research on the physicochemical drivers of abundance occurring at a fine scale. Here, high-frequency in situ measurements of pH, temperature, salinity, and dissolved oxygen were paired with daily fish catches in nearshore Alaskan waters of the Beaufort Sea. Due to the threat that climate change poses to high-latitude marine ecosystems, our main objective was to characterize the abiotic drivers of abundance and elucidate how nearshore fish communities may change in the future. We used generalized additive models (GAMs) to describe responses to the nearshore environment for 18 fish species. Relationships between abundance and the physicochemical environment were variable between species and reflected life history. Each abiotic covariate was significant in at least one GAM, exhibiting both nonlinear and linear associations with abundance. Temperature was the most important predictor of abundance and was significant in GAMs for 11 species. Notably, pH was a significant predictor of abundance for six species: Arctic cod (Boreogadus saida), broad whitefish (Coregonus nasus), Dolly Varden (Salvelinus malma), ninespine stickleback (Pungitius pungitius), saffron cod (Eleginus gracilis), and whitespotted greenling (Hexagrammos stelleri). Broad whitefish and whitespotted greenling abundance was positively associated with pH, while Arctic cod and saffron cod abundance was negatively associated with pH. These results may be a bellwether for future nearshore Arctic fish community change by providing a foundational characterization of the relationships between abundance and the abiotic environment, particularly in regard to pH, and demonstrate the importance of including a wider range of physicochemical habitat covariates in future research.
Seagrass ecosystem is one of the most productive ecosystems in coastal waters providing numerous ecological functions and supporting a large biodiversity. However, various anthropogenic stressors including climate change are impacting these vulnerable habitats. Here, we investigated the independent and combined effects of ocean warming and ocean acidification on plant–herbivore interactions in a tropical seagrass community. Direct and indirect effects of high temperature and high pCO2 on the physiology of the tropical seagrass Thalassia hemprichii and sea urchin Tripneustes gratilla were evaluated. Productivity of seagrass was found to increase under high pCO2, while sea urchin physiology including feeding rate decreased particularly under high temperature. The present study indicated that future climate change will affect the bottom-up and top-down balance, which potentially can modify the ecosystem functions and services of tropical seagrass ecosystems.
- Ocean acidification scenarios were assessed with mussel in presence of crack-cocaine.
- Lysosomal membrane stability, lipid peroxidation, and DNA strand breaks in Perna perna revealed toxicity increase.
- Adverse effects of acidification were detected for pH below 6.5.
- At pH 7.5–6.5 adverse effects are related to combined stressors (CO2 and cocaine).
The increasing CO2-concentrations in the atmosphere promote ocean acidification. Seawater chemistry changes interact with contaminants, such as illicit drugs in the coastal zones. This work evaluates impacts of pH decrease and crack-cocaine exposure on the commercial mussel Perna perna through biomarker responses (lysosomal membrane stability, lipid peroxidation, and DNA strand breaks). The organisms were exposed to different crack-cocaine concentrations (0.5, 5.0, and 50 μg L−1) combined with different pH values (8.3, 8.0, 7.5, 7.0, 6.5, and 6.0) for 96 h. Crack-cocaine in the different acidification scenarios triggered cyto-genotoxicity, which affected the overall health of mussels exposed to cocaine environmentally relevant concentration. This study produced the first data on biomarker responses associated with CO2-induced acidification and illicit drugs (crack-cocaine) in marine organisms.
Coralline algae play foundational roles in coastal ecosystems and are globally significant components of benthic habitats down to the limits of the photic zone. Despite their vulnerability to ocean acidification (OA) and importance in low light environments, there is a limited understanding of how the interplay between irradiance and OA influences coralline reproduction and recruitment. To better understand this interaction, a 212-day experiment was run exposing coralline communities to two pH(T) levels (present-day pH(T) 8.07/ OA pH(T) 7.65) and a gradient of daily light dose (0.35, 0.17 and 0.1 mol m-2 d-1), based on in situ measurements. In the highest light dose treatment, lowered seawater pH projected for 2100 (pH(T) 7.65) reduced recruitment by 56%. This OA-driven reduction in recruitment was amplified under reduced light, with recruitment near zero in the lowest light treatment. This study shows, for the first time, the increased vulnerability of coralline community recruitment to OA under low light. Coralline algae are known to be the deepest growing macroalgae and thus, in these low light zones, OA many have the potential to reduce coralline depth distribution.
Ocean warming is altering the biogeographical distribution of marine organisms. In the tropics, rising sea surface temperatures are restructuring coral reef communities with sensitive species being lost. At the biogeographical divide between temperate and tropical communities, warming is causing macroalgal forest loss and the spread of tropical corals, fishes and other species, termed “tropicalization”. A lack of field research into the combined effects of warming and ocean acidification means there is a gap in our ability to understand and plan for changes in coastal ecosystems. Here, we focus on the tropicalization trajectory of temperate marine ecosystems becoming coral-dominated systems. We conducted field surveys and in situ transplants at natural analogues for present and future conditions under (i) ocean warming and (ii) both ocean warming and acidification at a transition zone between kelp and coral-dominated ecosystems. We show that increased herbivory by warm-water fishes exacerbates kelp forest loss and that ocean acidification negates any benefits of warming for range extending tropical corals growth and physiology at temperate latitudes. Our data show that, as the combined effects of ocean acidification and warming ratchet up, marine coastal ecosystems lose kelp forests but do not gain scleractinian corals. Ocean acidification plus warming leads to overall habitat loss and a shift to simple turf-dominated ecosystems, rather than the complex coral-dominated tropicalized systems often seen with warming alone. Simplification of marine habitats by increased CO2 levels cascades through the ecosystem and could have severe consequences for the provision of goods and services.
In recent decades, the marine environment has been seriously affected by various anthropogenic activities (e.g., deforestation, fossil fuel combustion, and disordered discharges of pollutants). As a consequence, a range of changes in seawater environmental factors have taken place in oceans around the world, including increased temperature, reduced pH and dissolved oxygen, salinity fluctuation, and many other anomalous alterations in environmental factors, and these changes have aroused concerns from scientists. It has been widely reported that these changes in environmental factors would impact marine organisms severely. Meanwhile, it is worth noting that the environmental stressors mentioned above are rarely occurring independently in nature. Thus marine organisms are usually threatened by many different environmental stressors, and there would be complex and unpredicted interactions among the stressors. Generally, the interactive effects varied among additive (total effect equal to the sum of individual effects), synergistic (total effect greater than the sum of individual effects), or antagonistic (total effect less than the sum of individual effects), depending on the species and life stages of the studied organism, and the nature of the stressors themselves. It is necessary to figure out the interactive effects among various environmental stressors on specific marine organisms to accurately predict their physiological states and population dynamics under future climate scenarios. Therefore in this chapter, we summarize the related experiments in the last 20 years to discuss the interactive effects of ocean acidification (OA) combined with four other typical environmental stressors, namely ocean warming, hypoxia, salinity fluctuation, and heavy metal pollution, on marine organisms according to previously published studies. The authors hope that the contents of this chapter provide some basic information about the interactive effects of OA and the other four environmental factors for readers who are interested in this subject area.
Warming and acidification are expected impact of climate change that will affect marine areas in the future. These areas are, furthermore, vulnerable to strong anthropogenic stresses such as chemical pollutants. Nevertheless, the consequences of both stressors for marine ecosystems and organisms are still unidentified. The present study aims to examine, for the first time, the effect of temperature and CO2 pressure increase on bioaccumulation of phenanthrene as a PAHs model in four tissues, gills, digestive gland, muscle and mantle of a commercially important pearl oyster Pinctada radiata. Oysters were exposed to various combination of the ambient temperature and pH currently measured in Persian Gulf (T = 24 ºC and pH = 8.1) and the expected ocean warming and acidification (T = 28 ºC and pH = 7.6), as well as proper PhE concentration (0.8 ng.l− 1) during 28 days. In all exposures, higher PhE contents were observed under hypercapnia and warming condition in the digestive gland and gills, followed by the mantle and muscle. Generally, the results visibly reveal that longer exposure period led to promote PhE bioaccumulation in all tissues under ocean warming and acidification environment which was time-dependent pattern of PhE accumulation in P.radiata. Present-day PhE environmental concentrations, which combined with ocean warming and acidification, may lead to rigorous interruption of physiological functions can be extra threatened the ecological fitness of pearl oysters.
Symbiosis establishment is a milestone in the life cycles of most broadcast-spawning corals; however, it remains largely unknown how initial symbiont infection is affected by ocean warming and acidification, particularly for massive corals. This study investigated the combined effects of elevated temperature (29 vs. 31 °C) and pCO2 (~ 450 vs. ~ 1000 μatm) on the recruits of a widespread massive coral, Platygyra daedalea. Results showed that geometric diameter and symbiosis establishment were unaffected by high pCO2, while elevated temperature significantly reduced successful symbiont infection by 50% and retarded the geometric diameter by 6%. Although neither increased temperature, pCO2, nor their interaction affected survival or algal pigmentation of recruits, there was an inverse relationship between symbiont infection rates and survivorship, especially at high temperatures, possibly as a result of oxidative stress caused by algal symbionts under increased temperature. Intriguingly, the proportion of Durusdinium did not increase in recruits at 31 °C, while recruits reared under high pCO2 hosted less Breviolum and more Durusdinium, indicating a high degree of plasticity of early symbiosis and contrasting to the previous finding that heat stress usually leads to the prevalence of thermally tolerant Durusdinium in coral recruits. These results suggest that ocean warming is likely to be more deleterious for the early success of P. daedalea than ocean acidification and provide insights into our understanding of coral-algal symbiotic partnerships under future climatic conditions.
The sponge-associated microbial community contributes to the overall health and adaptive capacity of the sponge holobiont. This community is regulated by the environment and the immune system of the host. However, little is known about the effect of environmental stress on the regulation of host immune functions and how this may, in turn, affect sponge–microbe interactions. In this study, we compared the bacterial diversity and immune repertoire of the demosponge, Neopetrosia compacta, and the calcareous sponge, Leucetta chagosensis, under varying levels of acidification and warming stress based on climate scenarios predicted for 2100. Neopetrosia compacta harbors a diverse microbial community and possesses a rich repertoire of scavenger receptors while L. chagosensis has a less diverse microbiome and an expanded range of pattern recognition receptors and immune response-related genes. Upon exposure to RCP 8.5 conditions, the microbiome composition and host transcriptome of N. compacta remained stable, which correlated with high survival (75%). In contrast, tissue necrosis and low survival (25%) of L. chagosensis was accompanied by microbial community shifts and downregulation of host immune-related pathways. Meta-analysis of microbiome diversity and immunological repertoire across poriferan classes further highlights the importance of host–microbe interactions in predicting the fate of sponges under future ocean conditions.
Negative interactions among species are a major force shaping natural communities and are predicted to strengthen as climate change intensifies. Similarly, positive interactions are anticipated to intensify and could buffer the consequences of climate-driven disturbances. We used in situ experiments at volcanic CO2 vents within a temperate rocky reef to show that ocean acidification can drive community reorganization through indirect and direct positive pathways. A keystone species, the algal-farming damselfish Parma alboscapularis, enhanced primary productivity through its weeding of algae whose productivity was also boosted by elevated CO2. The accelerated primary productivity was associated with increased densities of primary consumers (herbivorous invertebrates), which indirectly supported increased secondary consumers densities (predatory fish) (i.e. strengthening of bottom-up fuelling). However, this keystone species also reduced predatory fish densities through behavioural interference, releasing invertebrate prey from predation pressure and enabling a further boost in prey densities (i.e. weakening of top-down control). We uncover a novel mechanism where a keystone herbivore mediates bottom-up and top-down processes simultaneously to boost populations of a coexisting herbivore, resulting in altered food web interactions and predator populations under future ocean acidification.
Changes to calcium carbonate (CaCO3) biomineralization in aquatic organisms is among the many predicted effects of climate change. Because otolith (hearing/orientation structures in fish) CaCO3 precipitation and polymorph composition are controlled by genetic and environmental factors, climate change may be predicted to affect the phenotypic plasticity of otoliths. We examined precipitation of otolith polymorphs (aragonite, vaterite, calcite) during early life history in two species of sturgeon, Lake Sturgeon, (Acipenser fulvescens) and White Sturgeon (A. transmontanus), using quantitative X-ray microdiffraction. Both species showed similar fluctuations in otolith polymorphs with a significant shift in the proportions of vaterite and aragonite in sagittal otoliths coinciding with the transition to fully exogenous feeding. We also examined the effect of the environment on otolith morphology and polymorph composition during early life history in Lake Sturgeon larvae reared in varying temperature (16/22 °C) and pCO2 (1000/2500 µatm) environments for 5 months. Fish raised in elevated temperature had significantly increased otolith size and precipitation of large single calcite crystals. Interestingly, pCO2 had no statistically significant effect on size or polymorph composition of otoliths despite blood pH exhibiting a mild alkalosis, which is contrary to what has been observed in several studies on marine fishes. These results suggest climate change may influence otolith polymorph composition during early life history in Lake Sturgeon.
Global change, including rising temperatures and acidification, threatens corals globally. Although bleaching events reveal fine-scale patterns of resilience, traits enabling persistence under global change remain elusive. We conducted a 95-d controlled-laboratory experiment investigating how duration of exposure to warming (~28, 31°C), acidification (pCO2 ~ 343 [present day], ~663 [end of century], ~3109 [extreme] μatm), and their combination influences physiology of reef-building corals (Siderastrea siderea, Pseudodiploria strigosa) from two reef zones on the Belize Mesoamerican Barrier Reef System. Every 30 d, net calcification rate, host protein and carbohydrate, chlorophyll a, and symbiont density were quantified for the same coral individual to characterize acclimation potential under global change. Coral physiologies of the two species were differentially affected by stressors and exposure duration was found to modulate these responses. Siderastrea siderea exhibited resistance to end of century pCO2 and temperature stress, but calcification was negatively affected by extreme pCO2. However, S. siderea calcification rates remained positive after 95 d of extreme pCO2 conditions, suggesting acclimation. In contrast, P. strigosa was more negatively influenced by elevated temperatures, which reduced most physiological parameters. An exception was nearshore P. strigosa, which maintained calcification rates under elevated temperature, suggesting local adaptation to the warmer environment of their natal reef zone. This work highlights how tracking coral physiology across various exposure durations can capture acclimatory responses to global change stressors.
Estuarine sediments make an important contribution to the global carbon cycle, but we do not know how this will change under a future climate, which is expected to have lower pH oceans and frequent high-temperature days. Six combinations of warming and partial pressures of CO2 (pCO2) were chosen to investigate the combined and individual effects of short-term pressures on the diel metabolic response of shallow unvegetated sediments ex-situ. Whereas warming significantly increased respiration, making sediments more heterotrophic, high-pCO2 increased net primary productivity, resulting in less heterotrophic sediments. As a result, warming decreased the carbon burial potential of estuarine sediments and high-pCO2 had the opposite effect. High-pCO2 mitigates the negative effects of warming on benthic metabolism under the combined scenario, with carbon burial similar to that expected under high-pCO2 conditions alone. Climate scenarios also changed the diurnal pCO2 variation, with ranges increasing by 33% with warming, and almost doubling under high-pCO2 conditions. An additive response in pCO2 variability was observed under the combined scenario, increasing to 2.3× the current diel-pCO2 range, highlighting the reduced buffering capacity of the water associated with a high CO2 climate. Future carbon burial and export under increased frequencies of unseasonably warm days projected for mid and end of century (30% and 50% of days-per-year, respectively) were estimated with and without ocean acidification. By 2100, warming alone could decrease annual estuarine sediment burial potential by 25%. However, ocean acidification could mitigate the negative effects of more frequent high-temperature days and increase carbon burial potential over current conditions by ~18%.
Climate change leads to multiple effects caused by simultaneous shifts in several physical factors which will interact with species and ecosystems in complex ways. In marine systems the effects of climate change include altered salinity, increased temperature, and elevated pCO2 which are currently affecting and will continue to affect marine species and ecosystems. Seaweeds are primary producers and foundation species in coastal ecosystems, which are particularly vulnerable to climate change. The brown seaweed Fucus vesiculosus (bladderwrack) is an important foundation species in nearshore ecosystems throughout its natural range in the North Atlantic Ocean and the Baltic Sea. This study investigates how individual and interactive effects of temperature, salinity, and pCO2 affect F. vesiculosus, using a fully crossed experimental design. We assessed the effects on F. vesiculosus in terms of growth, biochemical composition (phlorotannin content, C:N ratio, and ∂13C), and susceptibility to the specialized grazer Littorina obtusata. We observed that elevated pCO2 had a positive effect on seaweed growth in ambient temperature, but not in elevated temperature, while growth increased in low salinity at ambient but not high temperature, regardless of pCO2-level. In parallel to the statistically significant, but relatively small, positive effects on F. vesiculosus growth, we found that the seaweeds became much more susceptible to grazing in elevated pCO2 and reduced salinity, regardless of temperature. Furthermore, the ability of the seaweeds to induce chemical defenses (phlorotannins) was strongly reduced by all the climate stressors. Seaweeds exposed to ambient conditions more than doubled their phlorotannin content in the presence of grazers, while seaweeds exposed to any single or combined stress conditions showed only minor increases in phlorotannin content, or none at all. Despite the minor positive effects on seaweed growth, the results of this study imply that climate change can strongly affect the ability of fucoid seaweeds to induce chemical defenses and increase their susceptibility to grazers. This will likely lead to widespread consequences under future climate conditions, considering the important role of F. vesiculosus and other fucoids in many coastal ecosystems.
Oyster microbiomes are integral to healthy function and can be altered by climate change conditions. Genetic variation among oysters is known to influence the response of oysters to climate change and may ameliorate any adverse effects on oyster microbiome, however, this remains unstudied. Nine full-sibling selected breeding lines of the Sydney rock oyster (Saccostrea glomerata) were exposed to predicted warming (ambient = 24°C, elevated = 28°C) and ocean acidification (ambient pCO2 = 400, elevated pCO2 = 1000 µatm) for four weeks. The haemolymph bacterial microbiome was characterised using 16S rRNA (V3-V4) gene sequencing and varied among oyster lines in the control (ambient pCO2, 24°C) treatment. Microbiomes were also altered by climate change dependent on oyster lines. Bacterial α-diversity increased in response to elevated pCO2 in two selected lines, while bacterial β-diversity was significantly altered by combinations of elevated pCO2 and temperature in four selected lines. Climate change treatments caused shifts in the abundance of multiple Amplicon Sequence Variants (ASVs) driving change in the microbiome of some selected lines. We show that oyster genetic background may influence the Sydney rock oyster haemolymph microbiome under climate change and that future assisted evolution breeding programs to enhance resilience should consider the oyster microbiome.
There is a need to understand the responses of marine molluscs in this era of rapid climate change. Transgenerational plasticity that results in resilient offspring provides a mechanism for rapid acclimation of marine organisms to climate change. This study tested the hypothesis that adult parental exposure to elevated pCO2 and warming will have transgenerational benefits for offspring in the oysters Saccostrea glomerata and Crassostrea gigas. Adult S. glomerata and C. gigas were exposed to orthogonal treatments of ambient and elevated pCO2, and ambient and elevated temperature for 8 weeks. Gametes were collected and fertilized, larvae were then reared for 9 days under ambient and elevated pCO2. Egg lipidome and larval morphology and lipidome were measured. Parental exposure to warming and elevated pCO2 led to limited beneficial transgenerational responses for eggs and larvae of S. glomerata and C. gigas. Overall, larvae of S. glomerata were more sensitive than C. gigas, and both species had some capacity for transgenerational plasticity. This study supports the idea that transgenerational plasticity acts as an acclimatory mechanism for marine organisms to cope with the stress of climate change, but there are limitations, and it may not be a panacea or act equally in different species.
Under predicted future ocean conditions, reefs exposed to elevated nutrients will simultaneously experience ocean acidification and elevated temperature. We evaluated if moderate nutrients mitigate, minimize, or exacerbate negative effects of predicted future ocean conditions on coral physiology. For 30 days, Acropora millepora and Turbinaria reniformis were exposed to a fully factorial experiment of eight treatments including two seawater temperatures (26.4 °C and 29.8 °C), pCO2 levels (401 μatm pCO2 and 760 μatm pCO2), and nutrient concentrations (ambient: 0.40 μmol L−1 NO3− and 0.22 μmol L−1 PO43−, and moderate: 3.56 μmol L−1 NO3− and 0.31 μmol L−1 PO43−). Added nitrate was taken up by the algal endosymbionts and transferred to the coral hosts in both species, though to a much higher degree in A. millepora. When exposed to elevated temperature, elevated pCO2, or both, effects observed for chlorophyll a, calcification, biomass, and energy reserves were not compounded by the moderate nutrient concentrations in either species. Moderate nutrients enabled A. millepora to continue to meet daily metabolic demand via photosynthesis under predicted future ocean conditions and T. reniformis to greatly exceed daily metabolic demand via photosynthesis and heterotrophy. Our results suggest that balanced moderate nutrients are not detrimental to corals under predicted future ocean conditions and may even provide some benefits.
The sponge-associated microbial community contributes to the overall health and adaptive capacity of the sponge holobiont. This community is regulated by the environment, as well as the immune system of the host. However, little is known about the effect of environmental stress on the regulation of host immune functions and how this may, in turn, affect sponge-microbe interactions. In this study, we compared the microbiomes and immune repertoire of two sponge species, the demosponge, Neopetrosia compacta and the calcareous sponge, Leucetta chagosensis, under varying levels of acidification and warming stress. Neopetrosia compacta harbors a diverse bacterial assemblage and possesses a rich repertoire of scavenger receptors while L. chagosensis has a less diverse microbiome and an expanded range of pattern recognition receptors and proteins with immunological domains. Upon exposure to warming and acidification, the microbiome and host transcriptome of N. compacta remained stable, which correlated with high survival. In contrast, the bacterial community of L. chagosensis exhibited drastic restructuring and widespread downregulation of host immune-related pathways, which accompanied tissue necrosis and mortality. Differences in microbiome diversity and immunological repertoire of diverse sponge groups highlight the central role of host-microbe interactions in predicting the fate of sponges under future ocean conditions.
Increasing temperature and CO2 concentration are among the most important factors affecting marine ecosystems under climate change. We investigated the morphological, biochemical, and physiological trait responses of seedlings of the tropical seagrass Enhalus acoroides under experimental conditions. Trait responses were greater under temperature effects than increasing CO2 concentration. Seedlings under rising temperatures showed enhanced leaf growth, lower leaf nutrient content, and stimulated down-regulating mechanisms in terms of photo-physiology. Increasing CO2 concentrations did not show any significant effects independently. There was a significant interaction for some of the trait responses considered, such as leaf number and carbon content in the roots, and trends of higher starch concentrations in the leaves and lower rETRmax under combined enriched CO2 and high temperature, even though none of these interactions were synergistic. Understanding the single and interactive trait responses of seagrass seedlings to increasing temperature and CO2 concentration is of importance to determine the relative responses of early life stages of seagrasses, which may differ from adult plants, in order to form a more holistic view of seagrass ecosystem health under climate change.
- Skeletonema costatum was tolerant to low and moderate benzo(a)pyrene concentrations.
- The high benzo(a)pyrene concentration remarkably inhibited growth and photosynthesis.
- Negative effects of ocean acidification were detected at the high benzo(a)pyrene level.
The combined effects of polycyclic aromatic hydrocarbons and seawater acidification are poorly understood. Hence, we exposed the bloom-forming diatom Skeletonema costatum to four concentrations (0, 0.1, 1 and 10 μg L-1) of benzo(a)pyrene and two pCO2 levels (400 and 1000 μatm) to investigate its physiological performance. The growth and photosynthesis of S. costatum were tolerant to low and moderate benzo(a)pyrene concentrations regardless of the pCO2 level. However, the highest benzo(a)pyrene concentration had remarkably adverse effects on most parameters, decreasing the growth rate by 69%. Seawater acidification increased the sensitivity to high light stress, as shown by the lower relative maximum electron transport rate and light saturation point at the highest benzo(a)pyrene concentration. Our results suggested that benzo(a)pyrene could be detrimental to diatoms at a habitat-relevant level, and seawater acidification might further decrease its light tolerance, which would have important ramifications for the community structure and primary production in coastal waters.