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Genetic variation gives mussels a chance to adapt to climate change

Published 23 December 2019 Press releases Closed

Existing genetic variation in natural populations of Mediterranean mussels allows them to adapt to declining pH levels in seawater caused by carbon emissions

Existing genetic variation in natural populations of Mediterranean mussels allows them to adapt to declining pH levels in seawater caused by carbon emissions. A new study by biologists from the University of Chicago shows that mussels raised in a low pH experimental environment grew smaller shells than those grown at normal pH levels, but the overall survival rate of mussels grown under both conditions was the same.

The surviving population in the low pH environment differed genetically from the others, suggesting that genetic variants that already exist in a subset of the natural population of mussels allowed them to adapt to the harsher new environment. This could be good news for conservationists and seafood lovers alike, as the culinary delicacy finds ways to adjust to the changing seas.

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Standing genetic variation fuels rapid adaptation to ocean acidification

Published 23 December 2019 Science Closed
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Global climate change has intensified the need to assess the capacity for natural populations to adapt to abrupt shifts in the environment. Reductions in seawater pH constitute a conspicuous global change stressor that is affecting marine ecosystems globally. Here, we quantify the phenotypic and genetic modifications associated with rapid adaptation to reduced seawater pH in the Mediterranean mussel, Mytilus galloprovincialis. We reared a genetically diverse larval population in two pH treatments (pHT 8.1 and 7.4) and tracked changes in the shell-size distribution and genetic variation through settlement. Additionally, we identified differences in the signatures of selection on shell growth in each pH environment. Both phenotypic and genetic data show that standing variation can facilitate adaptation to declines in seawater pH. This work provides insight into the processes underpinning rapid evolution, and demonstrates the importance of maintaining variation within natural populations to bolster species’ adaptive capacity as global change progresses.

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Ocean acidification could eat away at sharks’ teeth and scales

Published 23 December 2019 Media coverage Closed

The fishes’ ability to swim and feed could be compromised

Sharks are some of the world’s most formidable predators, but their place at the top of the marine food chain may be threatened by ocean warming and acidification. As carbon dioxide levels in the oceans increase, upping the acidity of the water, shark teeth and scales may begin to corrode, compromising their ability to swim, hunt and feed, according to research published today in Scientific Reports.

Ultimately, sharks could be displaced as apex predators, disrupting entire ocean food webs, says the study’s senior author Lutz Auerswald, a fisheries biologist at Stellenbosch University in South Africa and the nation’s Department of Agriculture, Forestry and Fisheries. “Some of the bigger species, like great white sharks, are also already highly endangered, so this might wipe them out.”

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Acid-base adjustments and first evidence of denticle corrosion caused by ocean acidification conditions in a demersal shark species

Published 23 December 2019 Science Closed
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Global ocean acidification is expected to chronically lower the pH to 7.3 (>2200 µatm seawater pCO2) by the year 2300. Acute hypercapnia already occurs along the South African west and south coasts due to upwelling- and low-oxygen events, with increasing frequency. In the present project we investigated the impact of hypercapnia on the endemic demersal shark species Haploblepharus edwardsii. Specifically, we experimentally analysed acid-base regulation during acute and chronic hypercapnia, the effects of chronic hypercapnia on growth rates and on denticle structure- and composition. While H. edwardsii are physiologically well adapted to acute and chronic hypercapnia, we observed, for the first time, denticle corrosion as a result of chronic exposure. We conclude that denticle corrosion could increase denticle turnover and compromise hydrodynamics and skin protection.

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Ocean acidification could mean smaller scallops, threatened industry (text and audio)

Published 23 December 2019 Media coverage Closed

In a new experiment, scientists working at the Mass Maritime Academy in Bourne are finding that ocean acidification may have a profound effect on juvenile sea scallops.

Scientists at the Academy, in partnership with the National Oceanic and Atmospheric Administration (NOAA), are exposing sea scallops to three different levels of acidity, to see how they adapt to changing ocean chemistry.

Over the last 25 years, oceans have become increasingly acidic and that trend is expected to continue, as the water absorbs greenhouse gases produced by human activity.

“Research has shown that other bivalves [like oysters, clams, and quahogs] are affected by ocean acidification,” said Shannon Meseck, a research scientist at the NOAA Fisheries Millford Laboratory. “But to date, there’s no published research on the sea scallop, which is surprising because it is the second most important fishery in the Northeast. Second, to lobster.”

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Ocean acidification affects biological activities of seaweeds: a case study of Sargassum vulgare from Ischia volcanic CO2 vents

Published 23 December 2019 Science Closed
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Highlights

  • Bioactivities of S. vulgare from Ischia CO2 vents and nearby control site were analysed.
  • Elevated DIC increases polysaccharide content in the algae at CO2 vents.
  • Algal extract from acidified population showed higher antimicrobial, and antiprotozoal activity.
  • Acidified population showed pronounced antimutagenic potential and anticancer activities.

Abstract

We utilized volcanic CO2 vents at Castello Aragonese off Ischia Island as a natural laboratory to investigate the effect of lowered pH/elevated CO2 on the bioactivities of extracts from fleshy brown algae Sargassum vulgare C. Agardh. We analysed the carbohydrate levels, antioxidant capacity, antibacterial, antifungal, antiprotozoal, anticancer properties and antimutagenic potential of the algae growing at the acidified site (pH ∼ 6.7) and those of algae growing at the nearby control site Lacco Ameno (pH∼8.1). The results of the present study show that the levels of polysaccharides fucoidan and alginate were higher in the algal population at acidified site. In general, extracts for the algal population from the acidified site showed a higher antioxidant capacity, antilipidperoxidation, antibacterial, antifungal, antiprotozoal, anticancer activities and antimutagenic potential compared to the control population. The increased bioactivity in acidified population could be due to elevated levels of bioactive compounds of algae and/or associated microbial communities. In this snapshot study, we performed bioactivity assays but did not characterize the chemistry and source of presumptive bioactive compounds. Nevertheless, the observed improvement in the medicinal properties of S. vulgare in the acidified oceans provides a promising basis for future marine drug discovery.

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The application of the seaweeds in neutralizing the “ocean acidification” as a long-term multifaceted challenge

Published 23 December 2019 Science Closed
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The global effects of ocean acidification (OA) on coral reefs are of growing concern. Carbon dioxide released into the atmosphere as a result of burning fossil fuels, not only has an effect on “global warming”, but also on OA which is called the “other CO2 problem”. OA combined with high ocean temperatures has resulted in a massive bleaching of coral reefs in the Indian Ocean and throughout Southeast Asia over the past decade, which is ultimately lethal. Here we discuss the option if innovative seaweed bio-technology—the Ulva lactuca bioreactor option, with its H+ ion-absorbing capacity and its huge green biomass production of around 50 MT/ha/year—which can stabilize our “World Ocean” and our global coral reefs. From our calculations, we came to the conclusion that an area covered with “Ulva lactuca bioreactors” with a production capacity of 250 × 1016 ha of seaweed per year is needed to remove all H+ ions that cause OA in our “World Ocean” since the beginning of the “Industrial Revolution” ≈ 250 years ago. This is a daunting task and therefore we have opted for a multi-faceted approach including variability in seaweed species, avoidance of eutrophication & heavy-metal accumulation, prevention of global warming by more green-biomass production and a better estimation of the huge Kelp seaweed populations in temperate zones in order to protect our coral reefs for the short term.

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California coastal waters rising in acidity at alarming rate, study finds

Published 23 December 2019 Media coverage Closed

Waters off the California coast are acidifying twice as fast as the global average, scientists found, threatening major fisheries and sounding the alarm that the ocean can absorb only so much more of the world’s carbon emissions.

A new study led by the National Oceanic and Atmospheric Administration also made an unexpected connection between acidification and a climate cycle known as the Pacific Decadal Oscillation — the same shifting forces that other scientists say have a played a big role in the higher and faster rates of sea level rise hitting California in recent years.

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Influence of hydro-hydrochemical factors on the biodiversity of phytoplankton in the coastal aquatoria Black Sea with enhanced anthropogenous pollution (in Russian)

Published 20 December 2019 Science Closed
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The distribution of most phytoplankton representatives is significantly influenced by various hydrological and hydrochemical environmental factors. Degree of development of phytoplankton communities and their species composition can determine the level of pollution of sea water by various nutrients.

A survey was made of the coastal waters of the Black Sea, with in-creased anthropogenic pollution at 15 stations in winter period. At these stations, temperature, pH, and DOM concentration were registered and the composition of microalgae and phytoplankton cyanobacteria was studied.

The results obtained in the analysis of hydrological, hydrochemical and algological data make it possible to speak about the pronounced discreteness of abiotic environmental factors and the distribution of various phytoplankton representatives at 15 stations studied. The thermohaline structure in the water area was characterized by a pronounced temperature inversion in the cutaway part. The pH on the sea surface everywhere corresponded to its natural rate. A high degree of pollution of the waters of the entire investigated area by dissolved organic matter was noted. Using the methods of laboratory cultivation of samples, it was possible to identify the cyanobacteria component in the phytoplankton. The active development of cyanobacteria was revealed precisely at that point in the water area (station No. 8), where the local maximum of DOM content was observed. The presence in two samples (No. 13 and No. 16) of alkaliphilic cyanobacteria of the genus Rhabdodermain probably indicates a tendency for alkalization of water due to eutrophication. At stations No. 7 and No. 9, favorable conditions were established for the development of diatom algae, and at station No. 18, for unicellular green forms. In the remaining areas, the poor composition of phytoplankton largely corresponded to the data we obtained in the water area for the previous two years.

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Siderophore production by bacteria isolated from mangrove sediments: a microcosm study

Published 20 December 2019 Science Closed
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Highlights

  • Siderophores are organic ligands produced by bacteria primarily for iron sequestration.
  • In this study, siderophore production was independent of warmer temperatures that helped growth of the bacterial isolates.
  • Ocean acidification (pH 6.5 to 7.5) did not suppress siderophore production in these strains.
  • In this study, bacterial isolates used diverse carbon sources to produce siderophores.
  • Such responses of pathogenic strains may help in their survival in changing global environment, hence is of concern.

Abstract

Mangroves are one of the most productive ecosystems worldwide covering up to 75% of the coastline in the tropics and subtropics. They support a highly diverse community (marine and terrestrial) and serves as reservoirs of nutrients for coastal and shelf waters. Bacterial diversity in mangroves includes heterotrophs, autotrophs (nitrogen fixation) and pathogens (phytopathogens, marine, and human). All these bacterial groups require sequestration of bioavailable iron, which is largely done by the production of siderophores. In this study, microcosm experiments were conducted to test the effect of incubation conditions (temperature, iron concentration, pH, and carbon source) on growth and siderophore production in four mangrove sediment bacterial isolates- Escherichia vulneris, Enterobacter cancerogenus, Pantoea agglomerans, and Enterobacter bugandensis. Our study showed that all isolates produce more siderophores (30 to 60%) at low iron concentrations (10 nM to 1 μM) during lag-phase and early log-phase of growth. Low temperature suppressed bacterial growth without significantly altering the siderophore production, whereas low pH suppressed both growth and siderophore production in these isolates. Although all isolates could produce siderophores when using different carbon sources, glucose served as an ideal carbon source. The observed changes in growth and siderophore production may be attributed to species-specific physiological traits, changes in bioavailability of iron and/or combination of both. Our results suggest that in a changing global environment, warming of the surrounding waters may not reduce the siderophore production and hence, they will be essential in sustaining bacterial activity in sediments.

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Diatoms dominate and alter marine food-webs when CO2 rises

Published 20 December 2019 Science Closed
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Diatoms are so important in ocean food-webs that any human induced changes in their abundance could have major effects on the ecology of our seas. The large chain-forming diatom Biddulphia biddulphiana greatly increases in abundance as pCO2 increases along natural seawater CO2 gradients in the north Pacific Ocean. In areas with reference levels of pCO2, it was hard to find, but as seawater carbon dioxide levels rose, it replaced seaweeds and became the main habitat-forming species on the seabed. This diatom algal turf supported a marine invertebrate community that was much less diverse and completely differed from the benthic communities found at present-day levels of pCO2. Seawater CO2 enrichment stimulated the growth and photosynthetic efficiency of benthic diatoms, but reduced the abundance of calcified grazers such as gastropods and sea urchins. These observations suggest that ocean acidification will shift photic zone community composition so that coastal food-web structure and ecosystem function are homogenised, simplified, and more strongly affected by seasonal algal blooms.

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Long-term trends in pH in Japanese coastal seawater

Published 20 December 2019 Science Closed
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In recent decades, acidification of the open ocean has shown a consistent increase. However, analysis of long-term data in coastal seawater shows that the pH is highly variable because of coastal processes and anthropogenic carbon inputs. It is therefore important to understand how anthropogenic carbon inputs and other natural or anthropogenic factors influence the temporal trends in pH in coastal seawater. Using water quality data collected at 289 monitoring sites as part of the Water Pollution Control Program, we evaluated the long-term trends of the pHinsitu in Japanese coastal seawater at ambient temperature from 1978 to 2009. We found that the annual maximum pHinsitu, which generally represents the pH of surface waters in winter, had decreased at 75 % of the sites but had increased at the remaining sites. The temporal trend in the annual minimum pHinsitu, which generally represents the pH of subsurface water in summer, also showed a similar distribution, although it was relatively difficult to interpret the trends of annual minimum pHinsitu because the sampling depths differed between the stations. The annual maximum pHinsitu decreased at an average rate of −0.0024 yr−1, with relatively large deviations (0.0042 yr−1) from the average value. Detailed analysis suggested that the decrease in pH was caused partly by warming of winter surface waters in Japanese coastal seawater. The pH, when normalized to 25 ∘C, however, showed decreasing trends, suggesting that dissolved inorganic carbon from anthropogenic sources is increasing in Japanese coastal seawater.

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Responses of symbiotic cnidarians to environmental change

Published 20 December 2019 Science Closed
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As climate change intensifies, the capacity of organisms to adapt to changing environments becomes increasingly relevant. Heat-induced coral bleaching –the breakdown of the symbiotic association between coral hosts and photosynthetic algae of the family Symbiodiniaceae– is rapidly degrading reefs worldwide. Hence, there is a growing interest to study symbioses that can persist in extreme conditions. The Red Sea is such a place, known as one of the hottest seas where healthy coral reef systems thrive. Here (Chapter 1), we tested the potential of symbiont manipulation as means to improve the thermal resilience of the cnidarian holobiont, particularly using heat tolerant symbiont species from the Red Sea. We used clonal lineages of the model system Aiptasia (host and symbiont), originating from different thermal environments to assess how interchanging either partner affected their short- and long-term performance under heat stress. Our findings revealed that symbioses are not only intra-specific but have also adapted to native, local environments, thus potentially limiting the acclimation capacity of symbiotic cnidarians to climate change. As such, infection with more heat resistant species, even if native, might not necessarily improve thermotolerance of the holobiont. We further investigated (Chapter 2) how environment-dependent specificity, in this case elevated temperature, affects the establishment of novel symbioses. That is, if Aiptasia hosts are, despite exhibiting a high degree of partner fidelity, capable of acquiring more thermotolerant symbionts under stress conditions. Thus, we examined the infection dynamics of multi-species symbioses under different thermal environments and assessed their performance to subsequent heat stress. We showed that temperature, more than host identity, plays a critical role in symbiont uptake and overall performance when heatchallenged. Additionally, we found that pre-exposure to high temperature plays a fundamental role in improving the response to thermal stress, yet, this can be heavily influenced by other factors like feeding. Like climate change, ocean acidification is a serious threat to corals. Yet, most research has focused on the host and little is known for the algal partner. Thus, here we studied (Chapter 3) the global transcriptomic response of an endosymbiotic dinoflagellate to long-term seawater acidification stress. Our results revealed that despite observing an enrichment of processes related to photosynthesis and carbon fixation, which might seem beneficial to the symbiont, low pH has a detrimental effect on its photo-physiology. Taken together, this dissertation provides valuable insights into the responses of symbiotic cnidarians to future climate and ocean changes.

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Human impacts on planetary boundaries amplified by Earth system interactions

Published 20 December 2019 Science Closed
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The planetary boundary framework presents a ‘planetary dashboard’ of humanity’s globally aggregated performance on a set of environmental issues that endanger the Earth system’s capacity to support humanity. While this framework has been highly influential, a critical shortcoming for its application in sustainability governance is that it currently fails to represent how impacts related to one of the planetary boundaries affect the status of other planetary boundaries. Here, we surveyed and provisionally quantified interactions between the Earth system processes represented by the planetary boundaries and investigated their consequences for sustainability governance. We identified a dense network of interactions between the planetary boundaries. The resulting cascades and feedbacks predominantly amplify human impacts on the Earth system and thereby shrink the safe operating space for future human impacts on the Earth system. Our results show that an integrated understanding of Earth system dynamics is critical to navigating towards a sustainable future.

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Reconstructing 800 years of carbonate ion concentration in the Cariaco basin using the area density of planktonic foraminifera shells

Published 20 December 2019 Science Closed
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Anthropogenically mediated ocean acidification (OA) has negative impacts on many marine organisms, especially calcifiers. However, systematic measurements of OA have only been made over the past four decades. In order to improve future predictions and understand how ongoing OA compares to natural variability on longer timescales, it is critical to extend records beyond observational time series. In the Cariaco Basin, located in the tropical Atlantic, near‐surface dissolved inorganic carbon reflects atmospheric carbon dioxide concentrations (CO2) since the Industrial Revolution, making it an ideal site for examining longer‐term variability. We extend the record of Cariaco Basin near‐surface [CO32−] back to 1240 CE, using the area density (shell weight (μg)/shell area (μm2)) of the planktonic foraminifer Globigerinoides ruber (pink). Multidecadal variability is observed throughout the record. Since the Industrial Revolution (1760–2007 CE), [CO32−] has declined by 0.22 μmol kg−1 year−1, in agreement with the magnitude and direction of change captured in the shorter instrumental time series. During the Little Ice Age (1500–1760 CE), a period marked by regional drought, substantial variability but no long‐term trend is observed, while a decrease in [CO32−] of 0.11 μmol kg−1 y−1 occurs at the end of the Medieval Climate Anomaly (MCA) (1240 – 1500 CE). Both the MCA and Little Ice Age contain substantial natural variability in near surface [CO32−] that we attribute to changes in regional upwelling and atmospheric CO2. However, the decline in [CO32−] occurring in the Post‐Industrial Period is anomalous against a backdrop of 800 years of natural variability, reflecting OA associated with anthropogenic increases in atmospheric CO2.

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Jean-Pierre Gattuso – 2020 Ruth Patrick Award Recipient

Published 19 December 2019 Science , Web sites and blogs Closed

The Association for the Sciences of Limnology and Oceanography presents the Ruth Patrick Award each year to a scientist whose research leads to the identification, analysis and/or solution of important environmental problems. ASLO is pleased to award the 2020 Ruth Patrick Award to Jean-Pierre Gattuso for his leadership in, and commitment to, addressing ocean acidification. This acidification is due to increasing carbon dioxide in marine waters driven by fossil fuel emissions and represents a major threat to marine biodiversity. Dr. Gattuso’s research is providing the scientific basis and best practices to advance  experimental research and solutions to solve this important challenge. Gattuso is CNRS Senior Research Scientist at Sorbonne University and the Institute of Sustainable Development and International Relations. The award will be presented at the ASLO- SFS Meeting in Madison, Wisconsin in June 2020.

Gattuso is a leading researcher of ocean acidification (OA), with more than 100 publications spanning habitats and organisms including coral reefs, viruses, bacteria, phytoplankton, corals, mollusks and fish, from the Arctic to the Mediterranean and the tropics, as well as developing techniques and standardizing protocols for OA research. He has led numerous international working groups, including serving as the Scientific Coordinator of Europe’s first multi-investigator project on ocean acidification:  EPOCA (European Project on Ocean Acidification).

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The future of ocean acidification

Published 19 December 2019 Press releases Closed

New research by NOAA, the University of Maryland, and international partners published in Nature Scientific Reports shows that the changing chemistry of seawater has implications for continued greenhouse gas absorption.

The ocean has been playing an important role in helping slow down global climate change by removing the greenhouse gas carbon dioxide (CO2) from the atmosphere. However, decades of ocean observations show that the CO2 absorbed by the ocean is changing the chemistry of seawater, a process known as ocean acidification. The study discusses the reduced buffering capacity of the ocean as pH levels drop and its implications for reducing the ocean’s role as a CO2 sink in the future.

The researchers from NCEI, the NOAA Pacific Marine Environmental Laboratory (PMEL), and research institutions in Norway stress the importance of leveraging in situ observation-based global pH data products to help improve model projections. A climatology developed from this research may lead to more preventive and adaptive solutions to reduce carbon dioxide emissions and, at the same time, allow for ocean acidification adaptation strategies in regional areas.

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An annual update on the state of ocean acidification science in Alaska – 2019 update

Published 19 December 2019 Newsletters and reports Closed

What is Ocean Acidification?

Scientists estimate that the ocean is 30% more acidic today than it was 300 years ago, traceable to increasing levels of atmospheric carbon dioxide (CO2) from fossil fuel burning and land-use change, such as deforestation. As human-generated CO2 is released into the atmosphere, about a third is absorbed by the ocean. The additional CO2 lowers the pH of the seawater, driving the process known as ocean acidification (OA). The current pace of OA is faster than any time on record — 10 times faster than the last major acidification event 55 million years ago.

Why is Alaska at Risk?

Ocean acidification is expected to progress faster and more severely in Alaska than lower latitudes. Waters in Alaska are both ‘cold and old’: cooler water temperatures and global circulation patterns mean that Alaska waters naturally hold more CO2 year round. On top of this high baseline concentration of CO2, other processes also make Alaska’s waters more naturally acidic on a seasonal scale.

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Ocean acidification gets a watchful eye in New England aquaculture ‘hot spot’

Published 19 December 2019 Press releases Closed

Shellfish aquaculture is thriving in New England—some estimates suggest the market value tops $50 million. But the future of the industry’s growth is only as good as the ability of shellfish to build strong shells.

And that could prove challenging in decades to come as coastal waters in the region become more acidic, according to Jennie Rheuban, a research associate at Woods Hole Oceanographic Institution (WHOI).

“Coastal acidification here in Massachusetts is a real concern, as it can prevent mollusks from growing shells and affect how long it takes for them to reach a harvestable size,” says Rheuban. “Aquaculture businesses haven’t seen the effects yet, but the industry is vulnerable and could be at risk in the future.”

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Quantifying the effects of nutrient enrichment and freshwater mixing on coastal ocean acidification

Published 19 December 2019 Science Closed
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The U.S. Northeast is vulnerable to ocean and coastal acidification because of low alkalinity freshwater discharge that naturally acidifies the region, and high anthropogenic nutrient loads that lead to eutrophication in many estuaries. This study describes a combined nutrient and carbonate chemistry monitoring program in five embayments of Buzzards Bay, Massachusetts to quantify the effects of nutrient loading and freshwater discharge on aragonite saturation state (Ω). Monitoring occurred monthly from June 2015 to September 2017 with higher frequency at two embayments (Quissett and West Falmouth Harbors) and across nitrogen loading and freshwater discharge gradients. The more eutrophic stations experienced seasonal aragonite undersaturation, and at one site, nearly every measurement collected was undersaturated. We present an analytical framework to decompose variability in aragonite Ω into components driven by temperature, salinity, freshwater endmember mixing, and biogeochemical processes. We observed strong correlations between apparent oxygen utilization and the portion of aragonite Ω variation that we attribute to biogeochemistry. The regression slopes were consistent with Redfield ratios of dissolved inorganic carbon and total alkalinity to dissolved oxygen. Total nitrogen and the contribution of biogeochemical processes to aragonite Ω were highly correlated, and this relationship was used to estimate the likely effects of nitrogen loading improvements on aragonite Ω. Under nitrogen loading reduction scenarios, aragonite Ω in the most eutrophic estuaries could be raised by nearly 0.6 units, potentially increasing several stations above the critical threshold of 1. This analysis provides a quantitative framework for incorporating ocean and coastal acidification impacts into regulatory and management discussions.

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