The present study investigated the effects of rising carbon dioxide levels in nature and the carbon sequestration potential of dominant mangrove species for reducing the toxic effects of ocean acidification. The study was conducted on the east coast of Odisha, in the western Bay of Bengal. To determine the effect of these ambient parameters on the absorption of carbon dioxide by the mangroves, water temperature, salinity, pH levels of seawater along with soil texture and pH, salinity expressed in electrical conductivity, compactness expressed in bulk density, and soil organic carbon were simultaneously monitored. The aboveground biomass and carbon of the selected species were studied for 2 consecutive years at 10 designated stations. The total carbon calculated for the study area varied from 242.50 ± 49.00 to 1321.29 ± 445.52 tons with a mean of 626.68 ± 174.81 tons for Bhitarkanika and Mahanadi mangrove chunks. This is equivalent to 2299.92 ± 641.55 tons of CO2 absorbed from the atmosphere. A total of 27 equations were selected as the best fit models for the study area. The equations between mangrove biomass and carbon along with aquatic and edaphic factors governing the pH of water and soil strongly support the positive influence of mangrove photosynthetic activity in shifting the equilibrium toward alkalinity. This calls for conservation of mangrove ecosystem to minimize the pace of acidification of estuarine water. The results indicate that Excoecariaagallocha and Avicennia marina as are the most capable species for combatting maximum carbon dioxide toxicity from the atmosphere; which will be helpful in REDD + programs and carbon-based payments for ecosystem services (PES).
Continue reading ‘Role of abiotic factors in enhancing the capacity of mangroves in reducing ocean acidification’Posts Tagged 'salinity'
Role of abiotic factors in enhancing the capacity of mangroves in reducing ocean acidification
Published 15 August 2022 Science ClosedTags: biological response, Indian, mitigation, multiple factors, salinity, temperature
Quality control of potentiometric pH measurements with a combination of NBS and Tris buffers at salinities from 20 to 40 and pH from 7.2 to 8.6
Published 13 July 2022 Science ClosedTags: chemistry, laboratory, methods, multiple factors, salinity
Seawater pH is a valuable parameter to describe ocean acidification. However, pH measurements are often subject to large uncertainty and the results of the pH comparison from different laboratories are not convincing. We assessed the potentiometric method for pH measurement on seawater samples with salinities from 20 to 40 and pH ranging from 7.2 to 8.6. pH glass electrodes were calibrated using both commercially available NBS buffers and the equimolal Tris (2‐amino‐2‐hydroxymethyl‐1,3‐propanediol) buffer (prepared in synthetic seawater at a salinity of 35). The results demonstrated that the uncertainty in pH measurements was within ± 0.01 in the entire salinity range and was better than ± 0.003, when the sample salinity was close to that of equimolal Tris buffer (salinity difference within ± 2.5), regardless of the sample pH. This study suggests that if the electrode calibration is performed properly, the potentiometric method can fulfill the “weather” goal (± 0.02) of the Global Ocean Acidification Observing Network in pH measurements; it might even meet the “climate” goal (± 0.003) if the difference between the salinity of the samples and the Tris buffer is small.
Continue reading ‘Quality control of potentiometric pH measurements with a combination of NBS and Tris buffers at salinities from 20 to 40 and pH from 7.2 to 8.6’Survival of Atlantic bluefin tuna (Thunnus thynnus) larvae hatched at different salinity and pH conditions
Published 17 June 2022 Science ClosedTags: biological response, fish, fisheries, laboratory, mortality, multiple factors, physiology, reproduction, salinity
Highlights
- Atlantic bluefin tuna larvae survival is related to environmental salinity.
- Higher larval survival rates are shown at 36–38 ppt.
- Larval survival does not change within environmental pH from 8.0 to 7.3.
- Larval survival is related to osmoregulatory processes.
Abstract
In this study, we assessed the effect of environmental salinity and pH as independent factors on larval survival of Atlantic bluefin tuna (ABFT –Thunnus thynnus) together with their whole-body Na+/K+-ATPase and v-type H+-ATPase activities. Fertilized eggs of ABFT were obtained from a spontaneous spawning of broodstock in the farming facilities at El Gorguel (Cartagena, SE Spain) and were transferred to facilities of the Spanish Institute of Oceanography (IEO) in Mazarrón (SE Spain). In a first experiment, eggs (200 fertilized eggs L−1 per treatment, in 3 replicates) were exposed to different salinities treatments and constant pH 8.0 (control) until hatch was completed (50 h post-fertilization, hpf, at 23 °C): 27, 30, 33, 36, 37, 38 (control), 39, 40, 43, 46 and 49 ppt. In a second experiment eggs (200 fertilized eggs L−1, in 3 replicates) were exposed to seawater salinity (SW: 38 ppt) and four reduced pH treatments until hatch was completed (50 hpf at 23 °C): 8.0 (control), 7.7, 7.5 and 7.3. An inverse “U-shaped” relationship was observed between environmental salinity and number of hatched larvae. An opposite pattern was observed for both Na+/K+-ATPase and H+-ATPase activities in hatched larvae, increasing both activities in groups exposed to extreme salinities. Thus, larval survival was higher at intermediate salinities and lower at the extreme salinities tested. These results suggest higher survival rates with lower active pumps activities. No significant differences in larval survival were observed with pH treatment, but lower H+-ATPase activity was detected at control environmental pH (pH 8.0). Survival results are discussed in terms of osmoregulatory cost adapting to a salinity and pH predicted for the near future scenarios.
Continue reading ‘Survival of Atlantic bluefin tuna (Thunnus thynnus) larvae hatched at different salinity and pH conditions’The Mediterranean Rhodes gyre: modelled impacts of climate change, acidification and fishing
Published 10 June 2022 Science ClosedTags: fisheries, Mediterranean, modeling, multiple factors, nutrients, regionalmodeling, salinity, temperature
The Mediterranean Rhodes gyre is a cyclonic gyre with high primary production due to local upwelling of nutrients, and occasional deep overturning up to 1km depth. This nutrient-rich state is in sharp contrast to other parts of the Eastern Mediterranean which are oligotrophic. Here we study the upwelling system central to the Rhodes gyre and the impact of different stressors like meteorological changes, acidification and fishing pressure up to the year 2100. A water column model spanning the physical, chemical and biological system up to top predators (GOTM-ERSEM-BFM-EwE) was used to simulate the pelagic environment under single and combined stressors. Results show that due to increasing winter temperatures deep overturning events are becoming more rare in the future, until they stop occurring around 2060 under the business-as-usual climate scenario (RCP8.5). Stratification becomes stronger as temperature effects outweigh salinity effects in the surface mixed layer. Together with the lack of deep overturning this limits the nutrient supply to the euphotic zone, significantly reducing primary production. Phytoplankton species shift towards smaller species as nutrients become more scarce, mimicking the situation found currently on the edge of the gyre. Climatic changes and fishing pressure affected higher trophic levels in an additive way for some species (sardines, dolphins), while in a synergistic way for others (anchovy, mackerel). Acidification impacts were negligible. Fish stocks reduced significantly under the 2 climate scenarios considered: ~30% under RCP4.5 and ~40% under RCP8.5, with limited beneficial impact of MSY-level fishing, indicating a need for mitigating measures beyond fleet control.
Continue reading ‘The Mediterranean Rhodes gyre: modelled impacts of climate change, acidification and fishing’Temperature coefficient of seawater pH as a function of temperature, pH, DIC and salinity
Published 27 April 2022 Science ClosedTags: chemistry, laboratory, methods, multiple factors, salinity, temperature
pH is a measure of the hydrogen ion activity in solution, which is a function of temperature. Under normal seawater conditions, it is well constrained. Nowadays, with an increasing interest in complex environments (e.g., sea ice), a better understanding of the temperature change on pH under extreme conditions is needed. The objective of this paper was to investigate the temperature coefficient of the seawater pH (∆pH/∆T) over a wide range of temperature, pH, dissolved inorganic carbon (DIC) and salinity by a method of continuous pH measurement with the temperature change and to verify the application of CO2SYS for pH conversion under extreme conditions (on the NBS scale and the total proton scale). Both experimental results and CO2SYS calculations showed that ∆pH/∆T was slightly affected by temperature over the range of 0 to 40°C and by pH (at 25°C) from 7.8 to 8.5. However, when pH was out of this range, ∆pH/∆T varied greatly with pH value. According to the experimental results, changes in DIC from 1 mmol/kg to 5 mmol/kg and salinity from 20 to 105 had no significant effect on ∆pH/∆T. CO2SYS calculations showed a slight increase in ∆pH/∆T with DIC on both the NBS scale and the total proton scale; and underestimated ∆pH/∆T at high salinity (i.e., beyond the oceanographic range) on the NBS scale. Nevertheless, CO2SYS is still suitable for pH conversion even under extreme conditions by simply setting the input values of DIC and salinity in CO2SYS within the oceanographic range (e.g., DIC=2 mmol/kg and S=35).
Continue reading ‘Temperature coefficient of seawater pH as a function of temperature, pH, DIC and salinity’How do fungi survive in the sea and respond to climate change?
Published 14 April 2022 Science ClosedTags: biological response, fungi, morphology, mortality, multiple factors, physiology, review, salinity
With the over 2000 marine fungi and fungal-like organisms documented so far, some have adapted fully to life in the sea, while some have the ability to tolerate environmental conditions in the marine milieu. These organisms have evolved various mechanisms for growth in the marine environment, especially against salinity gradients. This review highlights the response of marine fungi, fungal-like organisms and terrestrial fungi (for comparison) towards salinity variations in terms of their growth, spore germination, sporulation, physiology, and genetic adaptability. Marine, freshwater and terrestrial fungi and fungal-like organisms vary greatly in their response to salinity. Generally, terrestrial and freshwater fungi grow, germinate and sporulate better at lower salinities, while marine fungi do so over a wide range of salinities. Zoosporic fungal-like organisms are more sensitive to salinity than true fungi, especially Ascomycota and Basidiomycota. Labyrinthulomycota and marine Oomycota are more salinity tolerant than saprolegniaceous organisms in terms of growth and reproduction. Wide adaptability to saline conditions in marine or marine-related habitats requires mechanisms for maintaining accumulation of ions in the vacuoles, the exclusion of high levels of sodium chloride, the maintenance of turgor in the mycelium, optimal growth at alkaline pH, a broad temperature growth range from polar to tropical waters, and growth at depths and often under anoxic conditions, and these properties may allow marine fungi to positively respond to the challenges that climate change will bring. Other related topics will also be discussed in this article, such as the effect of salinity on secondary metabolite production by marine fungi, their evolution in the sea, and marine endophytes.
Continue reading ‘How do fungi survive in the sea and respond to climate change?’Seasonal carbonate system vis-a-vis pH and salinity in selected tropical estuaries: implications on polychaete diversity and composition towards predicting ecological health
Published 16 February 2022 Science ClosedTags: annelids, biogeochemistry, biological response, Indian, laboratory, multiple factors, salinity, sediment
Highlights
- The role of salinity-pH gradient coupled with carbonate species on the polychaete community distribution was studied.
- Salinity-pH was positively correlated with carbonate and DOC.
- pCO2 was positively correlated with POC, DIC and CO2.
- High levels of carbonate species and low pH have a greater impact on polychaete diversity and richness.
Abstract
Salinity and pH play a fundamental role in structuring spatial patterns of physical properties, biota, and biogeochemical processes in the estuarine ecosystem. In this study, the influence of salinity-pH gradient and carbonate system on polychaete diversity in Ennore, Uppanar, Vellar, and Kaduvaiyar estuaries was investigated. Water and sediment samples were collected from September 2017 to August 2018. Univariate and multivariate statistical analyses were employed to define ecological status. Temperature, Salinity, pH, and partial pressure of carbon-di-oxide varied between 21 and 30°C; 29 and 39 ppt; 7.4 and 8.3; and 89.216 and 1702.558 µatm, respectively. PCA and CCA results revealed that DO, chlorophyll, carbonate species, and sediment TOC have a higher influence on polychaete community structure. Forty-two species such as Ancistrosyllis parva, Cossura coasta, Eunice pennata, Euclymene annandalei, Lumbrineris albidentata, Capitella capitata, Prionospio cirrifera, P. pinnata, P. cirrobranchiata, and Notomastus sp. were found dominantly in all estuaries. Shannon index values ranged between 1.619 (UE-1) and 3.376 (VE-2). Based on these findings, high levels of carbonate species and low pH have a greater impact on polychaete diversity and richness values. The results of the AMBI Index revealed that stations UE-1, UE-2, UE-3 in Uppanar, EC-1, EC-2 in Ennore indicate “moderately disturbed”, while other stations are under the “slightly disturbed” category. This trend was quite evident in M-AMBI as well.
Continue reading ‘Seasonal carbonate system vis-a-vis pH and salinity in selected tropical estuaries: implications on polychaete diversity and composition towards predicting ecological health’Can heat shock protein 70 (HSP70) serve as biomarkers in Antarctica for future ocean acidification, warming and salinity stress?
Published 4 February 2022 Science ClosedTags: Antarctic, multiple factors, physiology, prokaryotes, review, salinity
The Antarctic Peninsula is one of the fastest-warming places on Earth. Elevated sea water temperatures cause glacier and sea ice melting. When icebergs melt into the ocean, it “freshens” the saltwater around them, reducing its salinity. The oceans absorb excess anthropogenic carbon dioxide (CO2) causing decline in ocean pH, a process known as ocean acidification. Many marine organisms are specifically affected by ocean warming, freshening and acidification. Due to the sensitivity of Antarctica to global warming, using biomarkers is the best way for scientists to predict more accurately future climate change and provide useful information or ecological risk assessments. The 70-kilodalton (kDa) heat shock protein (HSP70) chaperones have been used as biomarkers of stress in temperate and tropical environments. The induction of the HSP70 genes (Hsp70) that alter intracellular proteins in living organisms is a signal triggered by environmental temperature changes. Induction of Hsp70 has been observed both in eukaryotes and in prokaryotes as response to environmental stressors including increased and decreased temperature, salinity, pH and the combined effects of changes in temperature, acidification and salinity stress. Generally, HSP70s play critical roles in numerous complex processes of metabolism; their synthesis can usually be increased or decreased during stressful conditions. However, there is a question as to whether HSP70s may serve as excellent biomarkers in the Antarctic considering the long residence time of Antarctic organisms in a cold polar environment which appears to have greatly modified the response of heat responding transcriptional systems. This review provides insight into the vital roles of HSP70 that make them ideal candidates as biomarkers for identifying resistance and resilience in response to abiotic stressors associated with climate change, which are the effects of ocean warming, freshening and acidification in Antarctic organisms.
Continue reading ‘Can heat shock protein 70 (HSP70) serve as biomarkers in Antarctica for future ocean acidification, warming and salinity stress?’How does ocean acidification affect the early life history of Zostera marina? A series of experiments find parental carryover can benefit viability or germination
Published 25 January 2022 Science ClosedTags: biological response, laboratory, morphology, multiple factors, North Atlantic, phanerogams, reproduction, salinity, temperature
Elevated partial pressure of carbon dioxide (pCO2) as a concomitant of global climate change may facilitate the establishment of future seagrass meadows and subsequently its benefit could be incorporated into techniques to increase restoration success. In five manipulative experiments, we determined how increased CO2 affects the maturation of flowers, and the development of seeds and seedlings for the foundation species Zostera marina. Experiments tested the development from both seeds collected from non-treated flowering shoots (direct) and seeds harvested from flowering shoots after CO2 exposure (parental carryover). Flowering shoots were collected along the western coast of Sweden near the island of Skafto. The seeds produced were used in experiments conducted at Kristineberg, Sweden and Dauphin Island, AL, United States. Experiments varied in temperature (16, 18°C) and salinity (19, 33 ppt), as well as duration and magnitude of elevated CO2 exposure. Flowering maturation, spathe number, seed production, and indicators of seed quality did not appear to be affected by 39–69 days of exposure to CO2 conditions outside of natural variability (pCO2 = 1547.2 ± 267.60 μatm; pHT = 7.53 ± 0.07). Yet, seeds produced from these flowers showed twofold greater germination success. In another experiment, flowering shoots were exposed to an extreme CO2 condition (pCO2 = 5950.7 ± 1,849.82 μatm; pHT = 6.96 ± 0.15). In this case, flowers generated seeds that demonstrated a fivefold increase in an indicator for seed viability (sinking velocity). In the latter experiment, however, germination appeared unaffected. Direct CO2 effects on germination and seedling production were not observed. Our results provide evidence of a parental CO2 effect that can benefit germination or seed viability, but early benefits may not lead to bed establishment if other environmental conditions are not well suited for seedling development. Outcomes have implications for restoration; CO2 can be supplied to flowering shoot holding tanks to bolster success when the purpose is to redistribute seeds to locations where beds are extant and water quality is adequate.
Continue reading ‘How does ocean acidification affect the early life history of Zostera marina? A series of experiments find parental carryover can benefit viability or germination’Climate change increases susceptibility to grazers in a foundation seaweed
Published 5 July 2021 Science ClosedTags: algae, biological response, laboratory, mollusks, morphology, multiple factors, North Atlantic, performance, physiology, salinity, temperature
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.
Continue reading ‘Climate change increases susceptibility to grazers in a foundation seaweed’Primary, secondary, and tertiary stress responses of juvenile seahorse Hippocampus reidi exposed to acute acid stress in brackish and seawater
Published 18 March 2021 Science ClosedTags: biological response, fish, laboratory, mortality, multiple factors, physiology, salinity, South Atlantic
Highlights
• Activity of antioxidant enzymes was harmed in seahorse juveniles exposed to acidic environment in brackish water.
• Lower tolerance for acidification in brackish water triggered lipid peroxidation in seahorse juveniles.
• Seahorse juvenile survival was not influenced by pH neither in brackish nor in sea water.
Abstract
Seahorse Hippocampus reidi is a vulnerable species, inhabiting estuarine and coastal waters. The safety of acidic environments for fish has been considered in terms of ocean acidification in nature and decreasing pH in intensive aquaculture systems. This study aimed to investigate the effects of acute exposition (96 h) of juvenile seahorses to different pH (5, 6, 7, and 8) in brackish (BW – salinity 11) or seawater (SW – salinity 33). For that, we studied the responses of cortisol, oxidative stress, and survival, thus covering primary, secondary, and tertiary stress responses. In SW, cortisol levels were not altered for fish maintained at pH 5 and 8. However, in BW, cortisol was higher for fish kept at pH 5. Regarding secondary stress responses, only GST activity increased with acidification in SW. However, acidification in BW caused biochemical alterations at enzymatic level (SOD, GST, GPx) and glutathione metabolism, accompanied by reduction of antioxidant capacity (TEAC) and increased lipid peroxidation (TBARS). Survival was always above 90% and it did not differ significantly among pH levels. Our results suggest that H. reidi juveniles are more vulnerable to acidic exposure in BW than in SW.
Continue reading ‘Primary, secondary, and tertiary stress responses of juvenile seahorse Hippocampus reidi exposed to acute acid stress in brackish and seawater’Effects of salinity, pH and alkalinity on hatching rate of fertilized eggs of Penaeus monodon
Published 1 March 2021 Science ClosedTags: biological response, crustaceans, laboratory, multiple factors, reproduction, salinity
The fertilized eggs of “Nanhai 2” Penaeus monodon bred by our research group were incubated at the same temperature (30°C), different salinity (20, 25, 30, 35, 40), different pH (7.0, 7.5, 8.0, 8.5, 9.0) and different alkalinity (2.0 mmol/L, 2.5 mmol/L, 3.0 mmol/L, 3.5 mmol/L, 4.0 mmol/L) to explore the effects of salinity, pH and alkalinity on hatching rate of fertilized eggs of P. monodon. The results showed that the hatching rate of fertilization rate of P. monodon was closely related to salinity, and the best hatching rate was obtained when the seawater salinity was 30 with the average hatching rate was 82.60%. The hatching rate was very low when the salinity was as low as 20 or as high as 40, which was significantly lower than that of other treatments (P<0.05). The hatching effect of the fertilized eggs of P. monodon was closely related to the pH value of seawater, and the slightly alkaline seawater was conducive to the normal development of the fertilized eggs. Among them, the hatching effect of the seawater pH value of 8.0 was the best, and the average hatching rate of the fertilized eggs was 80.62%. Too low or too high pH value of the seawater was not conducive to the development of the embryo, and the hatching rate of the fertilized eggs decreased in varying degrees. There was no significant correlation between the hatching effect of fertilized eggs and the change of seawater alkalinity. The average hatching rate of fertilized eggs ranged from 78.65% to 83.12% in the alkalinity range of 2.0-4.0 mmol/L
Continue reading ‘Effects of salinity, pH and alkalinity on hatching rate of fertilized eggs of Penaeus monodon’Long-term environmental tolerance of the non-indigenous Pacific oyster to expected contemporary climate change conditions
Published 7 December 2020 Science ClosedTags: biological response, laboratory, mollusks, morphology, multiple factors, North Atlantic, physiology, respiration, salinity, temperature
Highlights
- Long-term effects of climate change on non-indigenous species are rarely studied
- Pacific oysters were exposed to warming, ocean acidification and reduced salinity
- Warming and ocean acidification predicted for the year 2100 did not affect fitness
- Low salinity reduced clearance rates and increased oxygen consumption rates
- Long-term observations highlighted potential seasonal trends in physiological rates
Abstract
The current global redistribution of biota is often attributed to two main drivers: contemporary climate change (CCC) and non-indigenous species (NIS). Despite evidence of synergetic effects, however, studies assessing long-term effects of CCC conditions on NIS fitness remain rare. We examined the interactive effects of warming, ocean acidification and reduced salinity on the globally distributed marine NIS Magallana gigas(Pacific oyster) over a ten-month period. Growth, clearance and oxygen consumption rates were measured monthly to assess individual fitness. Lower salinity had a significant, permanent effect on M. gigas, reducing and increasing clearance and oxygen consumption rates, respectively. Neither predicted increases in seawater temperature nor reduced pH had a long-term physiological effect, indicating conditions predicted for 2100 will not affect adult physiology and survival. These results suggest that M. gigas will remain a globally successful NIS and predicted CCC will continue to facilitate their competitive dominance in the near future.
Continue reading ‘Long-term environmental tolerance of the non-indigenous Pacific oyster to expected contemporary climate change conditions’Decoupling salinity and carbonate chemistry: low calcium ion concentration rather than salinity limits calcification in Baltic Sea mussels
Published 17 November 2020 Science ClosedTags: Baltic, calcification, chemistry, field, laboratory, mollusks, morphology, multiple factors, salinity
The Baltic Sea has a salinity gradient decreasing from fully marine (> 25) in the West to below 7 in the Central Baltic Proper. Reef forming mytilid mussels exhibit decreasing growth when salinity < 11, however the mechanisms underlying reduced calcification rates in dilute seawater are not fully understood. In fact, both [HCO3−] and [Ca2+] also decrease with salinity, challenging calcifying organisms through CaCO3 undersaturation (Ω ≤ 1) and unfavourable ratios of calcification substrate (Ca2+ and HCO3−) to inhibitor (H+). In this study we assessed the impact of isolated individual factors (salinity, [Ca2+], [HCO3−] and pH) on calcification and growth of mytilid mussel populations along the Baltic salinity gradient. Laboratory experiments rearing juvenile Baltic Mytilus at a range of salinities (6, 11 and 16), HCO3− concentrations (300–2100 µmol kg−1) and Ca2+ concentrations (0.5–4 mmol kg−1) were coupled with field monitoring in three Baltic mussel reefs. Results reveal that as individual factors, low [HCO3−], pH and salinity cannot explain low calcification rates in the Baltic Sea. Calcification rates are impeded when Ωaragonite ≤ 1 or the substrate inhibitor ratio ≤ 0.7, primarily due to [Ca2+] limitation which corresponds to a salinity of ca. 11. Increased food availability may be able to mask these negative impacts, but not when seawater conditions are permanently adverse, as observed in two Baltic reefs at salinities < 11. Future climatic models predict rapid desalination of the southwest and Central Baltic and potentially a reduction in [Ca2+] which may lead to a westward distribution shift of marine calcifiers. It is therefore vital to understand the mechanisms by which the ionic composition of seawater impacts bivalve calcification for better predicting the future of benthic Baltic ecosystems.
Continue reading ‘Decoupling salinity and carbonate chemistry: low calcium ion concentration rather than salinity limits calcification in Baltic Sea mussels’Ocean freshening and acidification differentially influence mortality and behavior of the Antarctic amphipod Gondogeneia antarctica
Published 27 October 2020 Science ClosedTags: Antarctic, biological response, crustaceans, laboratory, mortality, multiple factors, performance, salinity
Highlights
- Glacial retreat induced by global warming can decrease salinity and pH of the Antarctic ocean.
- The Antarctic amphipod Gondogeneia antarctica was exposed to low salinity (27 psu) and low pH (7.6) conditions.
- Low salinity increased cannibalism and induced adjusted swimming.
- Low pH increased mortality, impaired food detection and reduced daytime shelter use.
- Ocean freshening and acidification act as independent stressors influencing behavior and physiology of Antarctic amphipods.
Abstract
The Western Antarctic Peninsula (WAP) has experienced rapid atmospheric and ocean warming over the past few decades and many marine-terminating glaciers have considerably retreated. Glacial retreat is accompanied by fresh meltwater intrusion, which may result in the freshening and acidification of coastal waters. Marian Cove (MC), on King George Island in the WAP, undergoes one of the highest rates of glacial retreat. Intertidal and shallow subtidal waters are likely more susceptible to these processes, and sensitive biological responses are expected from the organisms inhabiting this area. The gammarid amphipod Gondogeneia antarctica is one of the most abundant species in the shallow, nearshore Antarctic waters, and it occupies an essential ecological niche in the coastal marine WAP ecosystem. In this study, we tested the sensitivity of G. antarctica to lowered salinity and pH by meltwater intrusion following glacial retreat. We exposed G. antarctica to four different treatments combining two salinities (34 and 27 psu) and pH (8.0 and 7.6) levels for 26 days. Mortality, excluding cannibalized individuals, increased under low pH but decreased under low salinity conditions. Meanwhile, low salinity increased cannibalism, whereas low pH reduced food detection. Shelter use during the daytime decreased under each low salinity and pH condition, indicating that the two stressors act as disruptors of amphipod behavior. Under low salinity conditions, swimming increased during the daytime but decreased at night. Although interactions between low salinity and low pH were not observed during the experiment, the results suggest that each stressor, likely induced by glacial melting, causes altered behaviors in amphipods. These environmental factors may threaten population persistence in Marian Cove and possibly other similar glacial embayments.
Continue reading ‘Ocean freshening and acidification differentially influence mortality and behavior of the Antarctic amphipod Gondogeneia antarctica’Effects of low pH and low salinity induced by meltwater inflow on the behavior and physical condition of the Antarctic limpet, Nacella concinna
Published 27 October 2020 Science ClosedTags: Antarctic, biological response, dissolution, laboratory, mollusks, mortality, multiple factors, performance, physiology, salinity
Seawater acidification and freshening in the intertidal zone of Marian Cove, Antarctica, which occurs by the freshwater inflow from snow fields and glaciers, could affect the physiology and behavior of intertidal marine organisms. In this study, we exposed Antarctic limpets, Nacella concinna, to two different pH (8.00 and 7.55) and salinity (34.0 and 27.0 psu) levels and measured their righting ability after being flipped over, mortality, condition factor, and shell dissolution. During the 35-day exposure, there was no significant difference in behavior and mortality between different treatments. However, the condition factor was negatively affected by low salinity. Both low pH and low salinity negatively influenced shell formation by decreasing the aragonite saturation state (Ωarg) and enhancing shell dissolution. Our results suggest that, though limpets can tolerate short-term low pH and salinity conditions, intrusions of meltwater accompanied by the glacial retreat may act as a serious threat to the population of N. concinna.
Continue reading ‘Effects of low pH and low salinity induced by meltwater inflow on the behavior and physical condition of the Antarctic limpet, Nacella concinna’Contrasting responses to salinity and future ocean acidification in arctic populations of the amphipod Gammarus setosus
Published 14 October 2020 Science ClosedTags: Arctic, biological response, crustaceans, field, laboratory, multiple factors, physiology, salinity
Highlights
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Climate change is leading to changes in salinity and pCO2 in arctic/sub-arctic coastal ecosystems.
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We examined Gammarus setosus at 3 sites along a salinity gradient in the field and laboratory.
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Reduced salinity had more of an effect than elevated pCO2 by reducing energy budgets.
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Lower salinities increased ion transporting capacities in the laboratory but not in the field.
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G. setosus at lower salinity sites have lower energy budgets suggesting impacts on performance.
Abstract
Climate change is leading to alterations in salinity and carbonate chemistry in arctic/sub-arctic marine ecosystems. We examined three nominal populations of the circumpolar arctic/subarctic amphipod, Gammarus setosus, along a salinity gradient in the Kongsfjorden-/Krossfjorden area of Svalbard. Field and laboratory experiments assessed physiological (haemolymph osmolality and gill Na+/K+-ATPase activity, NKA) and energetic responses (metabolic rates, MO2, and Cellular Energy Allocation, CEA). In the field, all populations had similar osmregulatory capacities and MO2, but lower-salinity populations had lower CEA. Reduced salinity (S = 23) and elevated pCO2 (∼1000 μatm) in the laboratory for one month increased gill NKA activities and reduced CEA in all populations, but increased MO2 in the higher-salinity population. Elevated pCO2 did not interact with salinity and had no effect on NKA activities or CEA, but reduced MO2 in all populations. Reduced CEA in lower-rather than higher-salinity populations may have longer term effects on other energy demanding processes (growth and reproduction).
Lower salinity leads to improved physiological performance in the coccolithophorid Emiliania huxleyi, which partly ameliorates the effects of ocean acidification
Published 9 October 2020 Science ClosedTags: biological response, calcification, growth, laboratory, morphology, multiple factors, photosynthesis, phytoplankton, primary production, salinity
While seawater acidification induced by elevated CO2 is known to impact coccolithophores, the effects in combination with decreased salinity caused by sea ice melting and/or hydrological events have not been documented. Here we show the combined effects of seawater acidification and reduced salinity on growth, photosynthesis and calcification of Emiliania huxleyi grown at 2 CO2 concentrations (low CO2 LC:400 μatm; high CO2 HC:1000 μatm) and 3 levels of salinity (25, 30, and 35‰). A decrease of salinity from 35 to 25‰ increased growth rate, cell size and photosynthetic performance under both LC and HC. Calcification rates were relatively insensitive to salinity though they were higher in the LC-grown compared to the HC-grown cells at 25‰ salinity, with insignificant differences under 30 and 35‰. Since salinity and OA treatments did not show interactive effects on calcification, changes in calcification: photosynthesis ratios are attributed to the elevated photosynthetic rates at lower salinities, with higher ratios of calcification to photosynthesis in the cells grown under 35‰ compared with those grown at 25‰. In contrast, photosynthetic carbon fixation increased almost linearly with decreasing salinity, regardless of the pCO2 treatments. When subjected to short-term exposure to high light, the low-salinity-grown cells showed the highest photochemical effective quantum yield with the highest repair rate, though the HC treatment enhanced the PSII damage rate. Our results suggest that, irrespective of pCO2, at low salinity Emiliania huxleyi up-regulates its photosynthetic performance which, despite a relatively insensitive calcification response, may help it better adapt to future ocean global environmental changes, including ocean acidification, especially in the coastal areas of high latitudes.
