Ocean acidification (OA) can impact aquaculture because reduced pH may negatively affect the calcification in bivalve species. Photosynthetic activity can naturally generate an OA buffering effect, favouring the calcification process by increasing the surrounding seawater pH. Therefore, the incorporation of macroalgae into bivalve farms may be a strategy to mitigate the impacts of acidification on the industry. In this study, we evaluated the modification of seawater chemistry by the metabolic activity of the blue mussel Mytilus chilensis and three macroalgae (Ulva sp., Chondracanthus chamissoi and Macrocystis pyrifera), in monocultures and co-cultures under ambient and acidified initial conditions in three closed-environment experiments. In all three experiments, photosynthesis and respiration modulated seawater chemistry, resulting in higher values of pH, oxygen concentrations, and aragonite saturation state (ΩAra) in macroalgal monocultures compared to mussel monoculture. In co-cultures, pH, oxygen concentrations and ΩAra were higher than in mussel monoculture but lower than in macroalgal monoculture. In co-cultures, the OA buffering effect (pH > 7.7, ΩAra > 1) was observed during daytime, but unfavourable conditions for calcification were observed during nighttime. These results are species-specific, with a greater capacity for pH increase for Ulva sp. and Ch. chamissoi and limited capacity for M. pyrifera in both initial pH treatments. Results of the enclosed environment experiments indicate that the presence of macroalgae in co-cultures did not guarantee favourable conditions for mussel calcification in acidified conditions.
Continue reading ‘Evaluating the ability of macroalgae to create a chemical refuge for bivalves under ocean acidification conditions in closed-environment experiments’Posts Tagged 'South Pacific'
Evaluating the ability of macroalgae to create a chemical refuge for bivalves under ocean acidification conditions in closed-environment experiments
Published 26 January 2024 Science ClosedTags: chemistry, laboratory, mitigation, South Pacific
Local scale extreme low pH conditions and genetic differences shape phenotypic variation in a broad dispersal copepod species
Published 24 January 2024 Science ClosedTags: adaptation, biological response, chemistry, crustaceans, field, molecular biology, morphology, otherprocess, reproduction, South Pacific
Extreme low pH events in estuaries and upwelling areas can modulate the phenotypic and genetic diversity of natural populations. To test this hypothesis, we explored the linkage between local scale extreme low pH events, genetic diversity, and variation in fecundity-related traits (body size, egg size, and egg production rate) in the broad-dispersal copepod Acartia tonsa. We assessed genetic and phenotypic characteristics of populations by contrasting extreme low pH environments (upwelling and temperate estuary) in the coastal Southeast Pacific, under natural and experimental conditions. These populations showed significant genetic differentiation with higher diversity in mitochondrial and nuclear loci (encoding mtCOI and 18S rRNA) in the estuarine population. Copepods from this population are exposed to more frequent extreme low pH events (< 7.7), and the adult females exhibit consistent phenotypic variation in body size, egg size, and egg production rate across different cohorts. Experimental acclimation to extreme low pH conditions revealed no significant differences in fecundity-related traits between A. tonsa populations. Although these results partially support our hypothesis, the experimental findings suggest other drivers might also influence phenotypic differences in the local environments.
Continue reading ‘Local scale extreme low pH conditions and genetic differences shape phenotypic variation in a broad dispersal copepod species’Carbonate chemistry and carbon sequestration driven by inorganic carbon outwelling from mangroves and saltmarshes
Published 2 January 2024 Science ClosedTags: Arctic, chemistry, field, Indian, North Atlantic, North Pacific, South Atlantic, South Pacific
Mangroves and saltmarshes are biogeochemical hotspots storing carbon in sediments and in the ocean following lateral carbon export (outwelling). Coastal seawater pH is modified by both uptake of anthropogenic carbon dioxide and natural biogeochemical processes, e.g., wetland inputs. Here, we investigate how mangroves and saltmarshes influence coastal carbonate chemistry and quantify the contribution of alkalinity and dissolved inorganic carbon (DIC) outwelling to blue carbon budgets. Observations from 45 mangroves and 16 saltmarshes worldwide revealed that >70% of intertidal wetlands export more DIC than alkalinity, potentially decreasing the pH of coastal waters. Porewater-derived DIC outwelling (81 ± 47 mmol m−2 d−1 in mangroves and 57 ± 104 mmol m−2 d−1 in saltmarshes) was the major term in blue carbon budgets. However, substantial amounts of fixed carbon remain unaccounted for. Concurrently, alkalinity outwelling was similar or higher than sediment carbon burial and is therefore a significant but often overlooked carbon sequestration mechanism.
Continue reading ‘Carbonate chemistry and carbon sequestration driven by inorganic carbon outwelling from mangroves and saltmarshes’Resilience against the impacts of climate change in an ecologically and economically significant native oyster
Published 22 December 2023 Science ClosedTags: biological response, laboratory, mollusks, multiple factors, performance, physiology, respiration, South Pacific, temperature
Highlights
- Climate change is acidifying and warming oceans.
- Building resilience of marine species will be essential to ensure their persistence.
- Resilience to climate change in oysters was identified in a large-scale experiment as the capacity to defend acid-base balance and have a positive Scope for Growth.
- Only 8 of 24 genetically distinct family lines of this economically and ecologically important oyster species had resilience.
Abstract
Climate change is acidifying and warming our oceans, at an unprecedented rate posing a challenge for marine invertebrates vital across the globe for ecological services and food security. Here we show it is possible for resilience to climate change in an ecologically and economically significant oyster without detrimental effects to the energy budget. We exposed 24 pair-mated genetically distinct families of the Sydney rock oyster, Saccostrea glomerata to ocean acidification and warming for 4w and measured their resilience. Resilience was identified as the capacity to defend their acid-base balance without a loss of energy available for Scope for Growth (SFG). Of the 24 families, 13 were better able to defend their acid-base balance while eight had no loss of energy availability with a positive SFG. This study has found oyster families with reslience against climate change without a loss of SFG, is an essential mitigation strategy, in a critical mollusc.
Continue reading ‘Resilience against the impacts of climate change in an ecologically and economically significant native oyster’Systems thinking approach to understand Indonesia’s ocean acidification
Published 20 December 2023 Science ClosedTags: education, Indian, South Pacific
Establishing a proper connection between content and context is essential to infusing Systems Thinking (ST) into sustainable chemistry learning. Several efforts have been made to realize ST in chemistry in the context of coping with climate change through chemistry education. One potential model is connecting the interpretation of chemical reactions at the molecular level to local phenomena such as Indonesia’s ocean acidification (IOA). As citizens of an archipelagic country, Indonesian students should understand the fundamental nature of particles that cause ocean acidification. In this work, we offer the perspective on scaffolding the ST competencies using the iterative cycle of Design-Based Research, particularly in the preparation and design stages. The developed ST sequences appear from identifying system components via history; relationship between component and natural world; identifying dynamic interaction and cyclic behavior; application and ownership in sustainability action. All stages above focused on carbonate and hydrogen carbonate ions as central particles in the ocean acidification context. To sum up, the current Indonesian curriculum need to apply the ST approach to equip students as climate-literate citizens of science with adequate knowledge and skills.
Continue reading ‘Systems thinking approach to understand Indonesia’s ocean acidification’Evaluating the effects of climate change and chemical, physical and biological stressors on nearshore coral reefs: a case study in the Great Barrier Reef, Australia
Published 15 December 2023 Science ClosedTags: biological response, communitymodeling, corals, modeling, South Pacific
An understanding of the combined effects of climate change and other anthropogenic stressors, such as chemical exposures, is essential for improving ecological risk assessments of vulnerable ecosystems. In the Great Barrier Reef, coral reefs are under increasingly severe duress from increasing ocean temperatures, acidification and cyclone intensities associated with climate change. In addition to these stressors, inshore reef systems, such as the Mackay Whitsunday coastal zone are being impacted by other anthropogenic stressors, including chemical, nutrient and sediment exposures related to more intense rainfall events that increase catchment runoff of contaminated waters. To illustrate an approach for incorporating climate change into ecological risk assessment frameworks, we developed an adverse outcome pathway network to conceptually delineate effects of climate variables and PSII herbicide (diuron) exposures on scleractinian corals. This informed the development of a Bayesian network to quantitatively compare the effects of historical (1975-2005) and future projected climate on inshore hard coral bleaching, mortality, and cover. This Bayesian network demonstrated how risk may be predicted for multiple physical and biological stressors including temperature, ocean acidification, cyclones, sediments, macroalgae competition, and crown of thorns starfish predation, as well as chemical stressors such as nitrogen and herbicides. Climate scenarios included an ensemble of 16 downscaled models encompassing current and future conditions based on multiple emission scenarios for two thirty-year periods. It was found that both climate-related and catchment-related stressors pose a risk to these inshore reef systems, with projected increases in coral bleaching and coral mortality under all future climate scenarios. This modelling exercise can support the identification of risk drivers for the prioritisation of management interventions to build future resilient reefs.
Continue reading ‘Evaluating the effects of climate change and chemical, physical and biological stressors on nearshore coral reefs: a case study in the Great Barrier Reef, Australia’Porcelaneous larger foraminiferal responses to Oligocene–Miocene global changes
Published 1 December 2023 Science ClosedTags: biological response, BRcommunity, community composition, Indian, Mediterranean, North Pacific, otherprocess, paleo, protists, review, sediment, South Pacific
Highlights
- Porcelaneous large foraminifera diversified during the Oligocene–Miocene.
- The Aquitanian and Langhian–Serravallian peaks in richness occurred when SST ∼ 29 °C.
- Detrimental effects of high pCO2 (> 600 ppm) in the Rupelian–early Chattian.
- Detrimental effects of high tropical SST (> 31 °C) during the beginning of MCO
- Detrimental effects of low tropical SST (< 26 °C) in the Tortonian
- Sea-level highstands affected diversification of Oligocene–Miocene pLBF
Abstract
Sea surface temperatures (SST) have been identified as a main controlling factor on larger benthic foraminifera (LBF) living in tropical to sub-tropical shallow-water carbonate and mixed siliciclastic‑carbonate platforms. Changes in SST, along with those in ocean acidification and nutrient content recorded in the global oceans throughout their history will not only continue but also be amplified in the future at an unprecedented rate of change possibly reaching levels recorded in the geological record. This study focuses on the Oligocene (mean SST 8 °C higher than present) and the Miocene (SST 5–8 °C higher than present) epochs which were characterized by a higher richness in porcelaneous LBF (pLBF) than today. A systematic re-assessment and comprehensive literature survey of stratigraphic ranges and palaeogeographic distribution in the Western Tethyan (Mediterranean) and Indo-Pacific regions are used to evaluate the impact of changes in SST, seawater pCO2 and pH on the biodiversity of the Oligocene–Miocene pLBF Alveolinella, Austrotrillina, Borelis, Bullalveolina, Flosculinella and Praebullalveolina. Two peaks in species richness were identified during the Aquitanian and Langhian–Serravallian. These peaks occurred when SST was ∼29 °C, with pCO2 of ∼400 ppm and pH > 7.8. These values are comparable to those of today. The minima in species richness recorded in the Rupelian–early Chattian, in the Burdigalian and from the Tortonian onward can be correlated to the detrimental effects of both minima (< 26 °C) and maxima (> 31 °C) SST thresholds. High pCO2 (> 600 ppm) values, which are limited to the Rupelian–early Chattian, are also detrimental to species richness. Seawater pH higher than 7.7 did not negatively affect species richness. These historical trends have serious implications for the future diversity of pLBFs with the increasing likely scenario of rising SST and pCO2 and lowering of pH values in the near future. These developments can potentially lead to diversity decrease and even extinction of pLBFs. However, the resilience of present-day pLBF species to rising SST and pCO2 levels is underpinned by the evolutionary histories of their fossil counterparts during climate variations, albeit at much different rates of change.
Continue reading ‘Porcelaneous larger foraminiferal responses to Oligocene–Miocene global changes’Porites’ coral calcifying fluid chemistry regulation under normal- and low-pH seawater conditions in Palau Archipelago: impacts on growth properties
Published 28 November 2023 Science ClosedTags: biological response, calcification, corals, field, morphology, physiology, South Pacific
Highlights
- •Palau’s reef has a long-term naturally acidified inshore seawater (pH ~ 7.85).
- •Porites corals up-regulate calcifying fluid pH (~8.41) at normal- and low-pH sites.
- •Porites corals adapt calcifying fluid chemistry to long-term low-pH conditions.
- •Porites shows 15 % lower skeletal density under low-pH (~7.85) vs. open-ocean (~8.03).
Abstract
Ongoing ocean acidification is known to be a major threat to tropical coral reefs. To date, only few studies have evaluated the impacts of natural long-term exposure to low-pH seawater on the chemical regulation and growth of reef-building corals. This work investigated the different responses of the massive Porites coral living at normal (pHsw ~ 8.03) and naturally low-pH (pHsw ~ 7.85) seawater conditions at Palau over the last decades. Our results show that both Porites colonies maintained similar carbonate properties (pHcf, [CO32−]cf, DICcf, and Ωcf) within their calcifying fluid since 1972. However, the Porites skeleton of the more acidified conditions revealed a significantly lower density (~ 1.21 ± 0.09 g·cm−3) than the skeleton from the open-ocean site (~ 1.41 ± 0.07 g·cm−3). Overall, both Porites colonies exerted a strong biological control to maintain stable calcifying fluid carbonate chemistry that favored the calcification process, especially under low-pH conditions. However, the decline in skeletal density observed at low pH provides critical insights into Porites vulnerability to future global change.
Continue reading ‘Porites’ coral calcifying fluid chemistry regulation under normal- and low-pH seawater conditions in Palau Archipelago: impacts on growth properties’Impact of ocean acidification on coral reefs and the marine ecosystems in Phillipines
Published 17 November 2023 Science ClosedTags: biological response, corals, policy, review, South Pacific
Purpose: The aim of the study was to investigate the impact of ocean acidification on coral reefs and the marine ecosystems in phillipines
Methodology: The study adopted a desktop methodology. Desk research refers to secondary data or that which can be collected without fieldwork. Desk research is basically involved in collecting data from existing resources hence it is often considered a low cost technique as compared to field research, as the main cost is involved in executive’s time, telephone charges and directories. Thus, the study relied on already published studies, reports and statistics. This secondary data was easily accessed through the online journals and library
Findings: Ocean acidification reduces the density and growth of coral skeletons, making them more vulnerable to erosion. This threatens coral reefs and the marine life that depends on them. It also affects human benefits from coral reefs, such as fisheries, tourism and storm protection.
Unique Contribution to Theory, Practice and Policy: Theory of Ocean Acidification and Coral Calcification, Theory of Ocean Acidification and Biodiversity Loss and Theory of Adaptation and Resilience of Coral Reefs may be used to anchor future studies on impact of ocean acidification on coral reefs and the marine ecosystems in Philippines. Philippine government should actively participate in global climate agreements and implement policies to reduce carbon emissions at the domestic level. The Philippine government should integrate ocean acidification considerations into national environmental policies and action plans, such as the Philippine Coral Reef Protection Program.
Continue reading ‘Impact of ocean acidification on coral reefs and the marine ecosystems in Phillipines’Dive industry perspectives on threats to coral reefs: a comparative study across four Asia-Pacific countries
Published 15 November 2023 Science ClosedTags: corals, mitigation, North Pacific, policy, socio-economy, South Pacific
The combined effects of climate change, marine tourism and other stressors threaten the ecological and economic sustainability of coral reefs. This study investigates dive industry stakeholder awareness of the threats to coral reefs through structured interviews with Dive Masters, company managers and marine management agencies in Vietnam, Australia, Malaysia and Indonesia. Stakeholders from all locations have observed degradation of local reefs. Destructive fishing was identified as the principal threat in all regions except Australia. Most participants identified threats from climate change and marine tourism. There was a lack of awareness about ocean acidification by all participants from Maluku, Indonesia. However, ocean acidification could make coral more fragile and, therefore, vulnerable to diver-induced damage. The majority of Dive Masters across all regions provide pre-dive briefings to reduce diver impacts and participate in environmental activities to protect local reefs. Stakeholders in three regions thought there was capacity to expand the local dive industry. However, in Nha Trang Vietnam, most industry stakeholders thought they were at, or exceeded, carrying capacity, whereas marine management employees thought there was room to expand. This study highlights an opportunity to improve diver education on the vulnerability of coral to damage in acidifying oceans. This study also identifies various non-regulatory and regulatory strategies used to reduce diver impacts, emphasising the value of multi-national knowledge sharing between the dive industry and regulatory agencies for adaptive management.
HIGHLIGHTS
- Dive industry stakeholders are concerned about threats to coral reefs.
- Impacts from diving activities were recognised in three of four regions.
- There was great discrepancy between regions in the awareness of ocean acidification.
- Most dive industry stakeholders are engaged in marine conservation activities.
- Some marine managers and industry stakeholders had discrepant views on diver carrying capacity
The response of tuna to ocean acidification in Indonesian waters (case study: Gulf of Bone)
Published 7 November 2023 Science ClosedTags: abundance, biological response, chemistry, fish, morphology, otherprocess, review, South Pacific
There is growing concern about ocean acidification (decrease in pH of the ocean as a result of increased atmospheric carbon dioxide absorption by ocean) as one threat of climate change that may have significant impacts on marine organisms, such as fish. Recent studies suggest that adult fish are not directly impaired by OA, however, for the earliest fish stages, a number of direct effects have been observed. Hence, we observed the response of OA on monthly larvae density of yellowfin tuna in the Indonesian water, especially in the Gulf of Bone. The pH on the total scale (pH) and surface aqueous partial pressure of CO2 (pCO2) data were derived from Copernicus Marine Environment Monitoring Service (CMEMS) model product; meanwhile, fish data from 2014-2016 were derived from daily Infrastructure Development for Space Oceanography (INDESO) tuna population model outputs. This study indicates that the variability of pCO2 tends to increase while the pH tends to decline. During the northwest monsoon periods, pH in the Gulf of Bone tends to be lower. The larvae and juvenile of yellowfin tuna in the Gulf of Bone waters have various spatial correlations with pH and pCO2. Both have the potential to decrease with the declined pH and elevated pCO2.
Continue reading ‘The response of tuna to ocean acidification in Indonesian waters (case study: Gulf of Bone)’Effects of ocean acidification and warming on physiological and behavioural responses of an herbivore snail to waterborne predator cues
Published 30 October 2023 Science ClosedTags: biological response, communityMF, laboratory, mollusks, morphology, multiple factors, performance, respiration, South Pacific, temperature
Ocean Acidification (OA) and Ocean Warming (OW) represent major climate stressors that may disrupt species interactions. However, despite the knowledge about the impacts of OA and OW on the performance of individual species, it is still unclear how biological interactions can be modified by the combined effects of these stressors. Consequently, in this study, we assess the effects of changes in temperature (12 °C and 20 °C) and pCO2 (500 and 1600 μatm) levels in seawater, along with the presence/absence of waterborne cues from the predator crab Homalaspis plana on the physiological and behavioural performance of the snail Tegula atra. Snail consumption rate was positively affected by OW and negatively by predator cues whereas absorption efficiency (AE) was positively affected by OW without interactions among these stressors. Oxygen uptake of snails reared in OW conditions was greater than those in control conditions, but only at control pCO2 levels. When pCO2 level was also raised, the positive effect of warmer temperature on oxygen uptake was reduced. While biomass was negatively affected by OW, OA and predator cues, without interactions. In the presence of predator cues the self-righting times of snails were significantly slower in individuals reared at OW conditions. Additionally, OA and OW conditions do not affect the prey hunting, efficiency (consumption) and preference, and claw strength of the predatory crab. These results indicate that OA and OW affect physiological and behavioral traits of snails but no the predatory behavior of crab. This environmentally-induced decoupling of co-evolutionary predator-prey dynamics may have important consequences on the structure and stability of coastal communities and ecosystems under the influence of climate change.
Continue reading ‘Effects of ocean acidification and warming on physiological and behavioural responses of an herbivore snail to waterborne predator cues’Assessing the role of natural kelp forests in modifying seawater chemistry
Published 26 October 2023 Science ClosedTags: algae, chemistry, field, mitigation, South Pacific
Climate change is causing widespread impacts on seawater pH through ocean acidification (OA). Kelp forests, in some locations can buffer the effects of OA through photosynthesis. However, the factors influencing this variation remain poorly understood. To address this gap, we conducted a literature review and field deployments of pH and dissolved oxygen (DO) loggers within four habitats: intact kelp forest, moderate kelp cover, sparse kelp cover and barrens at one site in Port Phillip Bay, a wind-wave dominated coastal embayment in Victoria, Australia. Additionally, a wave logger was placed directly in front of the intact kelp forest and barrens habitats. Most studies reported that kelp increased seawater pH and DO during the day, compared to controls without kelp. This effect was more pronounced in densely populated forests, particularly in shallow, sheltered conditions. Our field study was broadly consistent with these observations, with intact kelp habitat having higher seawater pH than habitats with less kelp or barrens and higher seawater DO compared to barrens, particularly in the afternoon and during calmer wave conditions. Although kelp forests can provide local refuges to biota from OA, the benefits are variable through time and may be reduced by declines in kelp density and increased wave exposure.
Continue reading ‘Assessing the role of natural kelp forests in modifying seawater chemistry’Life-stage specificity and cross-generational climate effects on the microbiome of a tropical sea urchin (Echinodermata: Echinoidea)
Published 9 October 2023 Science ClosedTags: biological response, echinoderms, laboratory, molecular biology, morphology, mortality, multiple factors, physiology, reproduction, South Pacific, temperature
Microbes play a critical role in the development and health of marine invertebrates, though microbial dynamics across life stages and host generations remain poorly understood in most reef species, especially in the context of climate change. Here, we use a 4-year multigenerational experiment to explore microbe–host interactions under the Intergovernmental Panel on Climate Change (IPCC)-forecast climate scenarios in the rock-boring tropical urchin Echinometra sp. A. Adult urchins (F0) were exposed for 18 months to increased temperature and pCO2 levels predicted for years 2050 and 2100 under RCP 8.5, a period which encompassed spawning. After rearing F1 offspring for a further 2 years, spawning was induced, and F2 larvae were raised under current day and 2100 conditions. Cross-generational climate effects were also explored in the microbiome of F1 offspring through a transplant experiment. Using 16S rRNA gene sequence analysis, we determined that each life stage and generation was associated with a distinct microbiome, with higher microbial diversity observed in juveniles compared to larval stages. Although life-stage specificity was conserved under climate conditions projected for 2050 and 2100, we observed changes in the urchin microbial community structure within life stages. Furthermore, we detected a climate-mediated parental effect when juveniles were transplanted among climate treatments, with the parental climate treatment influencing the offspring microbiome. Our findings reveal a potential for cross-generational impacts of climate change on the microbiome of a tropical invertebrate species.
Continue reading ‘Life-stage specificity and cross-generational climate effects on the microbiome of a tropical sea urchin (Echinodermata: Echinoidea)’Role of culture solution pH in balancing CO2 input and light intensity for maximising microalgae growth rate
Published 4 October 2023 Science ClosedTags: algae, biological response, growth, laboratory, light, multiple factors, primary production, South Pacific
Highlights
- Microalgae growth is governed by CO2 input and light intensity.
- CO2 input & light intensity have an opposing impact on the culture pH.
- Microalgae growth can be inhibited by excessive lighting or CO2 input.
- Balancing CO2 input and light intensity is essential for CO2 fixation by microalgae.
- CO2 fixation rate of 4.2 g/L by Scenedesmus sp. at optimised condition.
Abstract
The interplay between CO2 input and light intensity is investigated to provide new insight to optimise microalgae growth rate in photobioreactors for environmental remediation, carbon capture, and biomass production. Little is known about the combined effect of carbon metabolism and light intensity on microalgae growth. In this study, carbonated water was transferred to the microalgae culture at different rates and under different light intensities for observing the carbon composition and growth rate. Results from this study reveal opposing effects from CO2 input and light intensity on the culture solution pH and ultimately microalgae growth rate. Excessive CO2 concentration can inhibit microalgae growth due to acidification caused by CO2 dissolution. While increasing light intensity can increase pH because the carboxylation process consumes photons and transfers hydrogen ions into the cell. This reaction is catalysed by the enzyme RuBisCO, which functions optimally within a specific pH range. By balancing CO2 input and light intensity, high microalgae growth rate and carbon capture could be achieved. Under the intermittent CO2 transfer mode, at the optimal condition of 850 mg/L CO2 input and 1089 μmol/m2/s light intensity, leading to the highest microalgae growth rate and carbon fixation of 4.2 g/L as observed in this study.
Continue reading ‘Role of culture solution pH in balancing CO2 input and light intensity for maximising microalgae growth rate’The estuarine environment and pH variation: natural limits and experimental observation of the acidification effect on phosphorus bioavailability (in Portuguese)
Published 14 September 2023 Science ClosedTags: biogeochemistry, biological response, chemistry, field, sediment, South Pacific
This study shows the variation of pH in the Cananéia-Iguape Estuarine-Lagoon Complex (CIELC). Data from 3 years (2019, 2021, 2022) were obtained in 17 points presenting the following ranges: temperature (14.88-27.05 ºC), pH (7.16-8.40) and DIP (0.20-11.28 µmol L-1) along a saline gradient (0.05-32.09) under different hydrodynamics, biogeochemical processes and anthropogenic influence. The pH buffering capacity due to the presence of weak acid salts in saline water (S ≥ 30) was associated to the lowest DIP, decreasing with low salinity values, confirming the direct correlation among salinity and pH. The highest temperatures in the winter of 2021, corroborated with the abnormal climate event in that year. An in vitro experiment showed results of the interaction of PID and sediments with different textures, with and without the presence of the benthic microbiota under a considerable decreasing of the pH (acidification) in relation to the natural condition of this environment. The P sediment flux characterized Iguape sector as a P sink with or without biota, Ararapira sector as a P source with biota and Cananéia, as P source without biota. The salt water buffered the pH and sediment buffered DIP both associated to the biogeochemical and hydrodynamic processes contribute to the homeostasis in the system.
Continue reading ‘The estuarine environment and pH variation: natural limits and experimental observation of the acidification effect on phosphorus bioavailability (in Portuguese)’Predicting the impacts of climate change on New Zealand’s seaweed-based ecosystems
Published 11 September 2023 Science ClosedTags: algae, biological response, BRcommunity, review, South Pacific
The impacts of global climate change are threatening the health and integrity of New Zealand’s seaweed ecosystems that provide crucial ecological, economic, and cultural benefits. Important species that comprise these ecosystems include canopy forming large brown algae (fucoids and kelp), and understorey species. Here we review current knowledge of the measured impacts of climate change stressors on New Zealand seaweeds. Ocean warming has driven increasing frequencies, durations, and intensities of marine heatwaves globally and in New Zealand. Significant negative impacts resulting from heatwaves have already been observed on New Zealand’s canopy forming brown algae (giant kelp Macrocystis pyrifera and bull kelp Durvillaea spp.). We predict that ongoing ocean warming and associated marine heatwaves will alter the distributional range and basic physiology of many seaweed species, with poleward range shifts for many species. Increased extreme weather events causes accelerated erosion of sediments into the marine environment and re-suspension of these sediments, termed coastal darkening, which has reduced the growth rates and available vertical space on rocky reefs in New Zealand and is predicted to worsen in the future. Furthermore, ocean acidification will reduce the growth and recruitment of coralline algae, this may reduce the settlement success of many marine invertebrate larvae. Mechanistic underpinnings of the effects of multiple drivers occurring in combination is poorly described. Finally, local stressors, such as overfishing, will likely interact with global change in these ecosystems. Thus, we predict very different futures for New Zealand seaweed ecosystems depending on whether they are managed appropriately or not. Given recent increases in sea surface temperatures and the increasing frequency of extreme weather events in some regions of New Zealand, predicting the impacts of climate change on seaweeds and the important communities they support is becoming increasingly important for conserving resilient seaweed ecosystems in the future.
Continue reading ‘Predicting the impacts of climate change on New Zealand’s seaweed-based ecosystems’Long-term preconditioning of the coral Pocillopora acuta does not restore performance in future ocean conditions
Published 28 August 2023 Science ClosedTags: abundance, algae, biological response, corals, laboratory, multiple factors, otherprocess, photosynthesis, physiology, South Pacific, temperature
There is overwhelming evidence that tropical coral reefs are severely impacted by human induced climate change. Assessing the capability of reef-building corals to expand their tolerance limits to survive projected climate trajectories is critical for their protection and management. Acclimation mechanisms such as developmental plasticity may provide one means by which corals could cope with projected ocean warming and acidification. To assess the potential of preconditioning to enhance thermal tolerance in the coral Pocillopora acuta, colonies were kept under three different scenarios from settlement to 17 months old: present day (0.9 °C-weeks (Degree Heating Weeks), + 0.75 °C annual, 400 ppm pCO2) mid-century (2.5 °C-weeks, + 1.5 °C annual, 685 ppm pCO2) and end of century (5 °C-weeks, + 2 °C annual, 900 ppm pCO2) conditions. Colonies from the present-day scenario were subsequently introduced to the mid-century and end of century conditions for six weeks during summer thermal maxima to examine if preconditioned colonies (reared under these elevated conditions) had a higher physiological performance compared to naive individuals. Symbiodiniaceae density and chlorophyll a concentrations were significantly lower in mid-century and end of century preconditioned groups, and declines in symbiont density were observed over the six-week accumulated heat stress in all treatments. Maximum photosynthetic rate was significantly suppressed in mid-century and end of century preconditioned groups, while minimum saturating irradiances were highest for 2050 pre-exposed individuals with parents originating from specific populations. The results of this study indicate preconditioning to elevated temperature and pCO2 for 17 months did not enhance the physiological performance in P. acuta. However, variations in trait responses and effects on tolerance found among treatment groups provides evidence for differential capacity for phenotypic plasticity among populations which could have valuable applications for future restoration efforts.
Continue reading ‘Long-term preconditioning of the coral Pocillopora acuta does not restore performance in future ocean conditions’A synthesis of SNAPO-CO2 ocean total alkalinity and total dissolved inorganic carbon measurements from 1993 to 2022
Published 23 August 2023 Science ClosedTags: Antarctic, chemistry, field, Indian, Mediterranean, North Atlantic, North Pacific, South Atlantic, South Pacific
Total alkalinity (AT) and total dissolved inorganic carbon (CT) in the oceans are important properties to understand the ocean carbon cycle and its link with climate change (ocean carbon sinks and sources) or global change (ocean acidification). We present a data-base of more than 44 400 AT and CT observations in various ocean regions obtained since 1993 mainly in the frame of French projects. This includes both surface and water columns data acquired in open oceans, coastal zones and in the Mediterranean Sea and either from time-series or punctual cruises. Most AT and CT data in this synthesis were measured from discrete samples using the same closed-cell potentiometric titration calibrated with Certified Reference Material, with an overall accuracy of ± 4 µmol kg-1 for both AT and CT. Given the lack of observations in the Indian and Southern Oceans, we added sea surface underway AT and CT data obtained in 1998–2018 in the frame of OISO cruises and in 2019 during the CLIM-EPARSES cruise measured onboard using the same technique. Separate datasets for the global ocean, and for the Mediterranean Sea are provided in a single format (https://doi.org/10.17882/95414, Metzl et al., 2023) that offers a direct use for regional or global purposes, e.g. AT/Salinity relationships, long-term CT estimates, constraint and validation of diagnostics CT–AT reconstructed fields or ocean carbon and coupled climate/carbon models simulations, as well as data derived from BG-ARGO floats. When associated with other properties, these data can also be used to calculate pH, fugacity of CO2 (fCO2) and other carbon systems properties to derive ocean acidification rates or air-sea CO2 fluxes.
Continue reading ‘A synthesis of SNAPO-CO2 ocean total alkalinity and total dissolved inorganic carbon measurements from 1993 to 2022’Rising snow line: Ocean acidification and the submergence of seafloor geomorphic features beneath a rising carbonate compensation depth
Published 22 August 2023 Science ClosedTags: Antarctic, Arctic, chemistry, Indian, modeling, North Atlantic, North Pacific, regionalmodeling, review, South Atlantic, South Pacific
Highlights
- Ocean acidification has caused the carbonate compensation depth (CCD) to rise by ~98 m.
- Seafloor area below the CCD has increased by 3.6% in the last 200 years.
- Risk of impact of rising CCD is greatest in the western equatorial Atlantic Ocean.
- Different geomorphic features impacted by rising CCD in different ocean areas.
Abstract
Due to burning of fossil fuels, carbon dioxide is being absorbed by the ocean where its chemical conversion to carbonic acid has already caused the surface ocean to become more acidic than it has been for at least the last 2 million years. Global ocean modeling suggests that the carbonate compensation depth (CCD) has already risen by nearly 100 m on average since pre-industrial times and will likely rise further by several hundred meters more this century. Potentially millions of square kilometres of ocean floor will undergo a rapid transition in terms of the overlying water chemistry whereby calcareous sediment will become unstable causing the carbonate “snow line” to rise.We carried out a spatial analysis of seafloor geomorphology to assess the area newly submerged below the rising CCD. We found that shoaling of the CCD since the industrial revolution has submerged 12,432,096 km2 of ocean floor (3.60% of total ocean area) below the CCD. Further hypothetical shoaling of the CCD by 100 m increments illustrated that the surface area of seafloor submerged below the CCD has risen by 14% with 300 m of shoaling, such that 51% of the ocean area will be below the CCD. All categories of geomorphic feature mapped in one global database intersect the lysocline and will be (or already are) submerged below the CCD with much regional variation since the rise in CCD depth during the last 150 years varies significantly between different ocean regions. For seamounts, the highest percentages of increase in area submerged below the CCD occurred in the Southern Indian Ocean and the South West Atlantic regions (6.3% and 5.9%, respectively). For submarine canyons we found the South West Atlantic increased from 3.9% in pre-industrial times to 8.0% at the present time, the highest percentage of canyons found below the CCD in any ocean region.We also carried out a relative risk assessment for future submergence of ocean floor below the CCD in 17 ocean regions. In our assessment we assumed that the change in CCD from pre-industrial times to the present is an indicator of the likelihood and the change in percentage of seafloor submerged below the CCD due to a hypothetical 300 m rise in the CCD is an indicator of the consequences. We found that the western equatorial Atlantic is at high risk and 9 other Ocean Regions are at moderate risk. Overall, geomorphic features in the Atlantic Ocean and southern Indian Ocean are at greater risk of impact from a rising CCD than Pacific and other Indian Ocean regions.A separate analysis of the Arctic Ocean points to the possible submergence of glacial troughs incised on the continental shelf within a mid-depth (400–800 m) acidified water mass. We also found that the area of national Exclusive Economic Zones submerged below the rising CCD exhibits extreme variability; with 300 m of CCD shoaling we found a > 12% increase in area submerged below the CCD for 23 national EEZs, whereas there was virtually no change for other countries.
Continue reading ‘Rising snow line: Ocean acidification and the submergence of seafloor geomorphic features beneath a rising carbonate compensation depth’
