Archive for February, 2021

Effect of ocean acidification on bacterial metabolic activity and community composition in oligotrophic oceans, inferred from short-term bioassays

Increasing anthropogenic CO2 emissions in recent decades cause ocean acidification (OA), affecting carbon cycling in oceans by regulating eco-physiological processes of plankton. Heterotrophic bacteria play an important role in carbon cycling in oceans. However, the effect of OA on bacteria in oceans, especially in oligotrophic regions, was not well understood. In our study, the response of bacterial metabolic activity and community composition to OA was assessed by determining bacterial production, respiration, and community composition at the low-pCO2 (400 ppm) and high-pCO2 (800 ppm) treatments over the short term at two oligotrophic stations in the northern South China Sea. Bacterial production decreased significantly by 17.1–37.1 % in response to OA, since bacteria with high nucleic acid content preferentially were repressed by OA, which was less abundant under high-pCO2 treatment. Correspondingly, shifts in bacterial community composition occurred in response to OA, with a high fraction of the small-sized bacteria and high bacterial species diversity in a high-pCO2 scenario at K11. Bacterial respiration responded to OA differently at both stations, most likely attributed to different physiological responses of the bacterial community to OA. OA mitigated bacterial growth efficiency, and consequently, a larger fraction of DOC entering microbial loops was transferred to CO2.

Continue reading ‘Effect of ocean acidification on bacterial metabolic activity and community composition in oligotrophic oceans, inferred from short-term bioassays’

Impact of ocean acidification on ecosystem functioning and services in habitat-forming species and marine ecosystems

Ocean acidification (OA) is expected to impact habitat-forming species (HFS), with cascading effects on the whole marine ecosystem and related services that are seldom quantified. Here, the changes in HFSs biomass due to OA are modeled using a food web ecosystem model, and the trophic and non-trophic cascading effects on the marine community are investigated. The food web model represents a well-studied coastal marine protected area in the NW Mediterranean Sea where coralligenous reefs and Posidonia oceanica meadows constitute important HFS. The model is used to implement 5 scenarios of habitat degradation, that is, reduction of HFS biomass, induced by increasing OA and to quantify the potential changes in ecosystem properties and indicators of ecosystem services over the next 100 years. The changes in ecosystem indicators highlight a decrease in the size of the system and a reorganization of energy flows suggesting a high degree of ecosystem development. All the proxies for ecosystem services show significant decreases in their values. Although representing only a portion of the possible impacts of OA, the findings are consistent with the idea that ecological systems can react to OA effects to maintain the level of ecosystem development, but the new organization might not be optimal from an anthropocentric viewpoint.

Continue reading ‘Impact of ocean acidification on ecosystem functioning and services in habitat-forming species and marine ecosystems’

Turning up the lights: ocean acidification may increase light intensity of secretory bioluminescent signaling (text & video)

Video created by Tom Iwanicki, PhD Candidate at the University of Hawai’i at Manoa, presented at the annual meeting of the Society for Integrative and Comparative Biology in January 2021 through February 2021. These data are unpublished.

Synopsis: Approximately 75% of pelagic organisms are capable of bioluminescence. Under the IPCC worst-case scenario (RCP8.5), the average ocean pH will decrease from its pre-industrial average of 8.2 to 7.7 by the end of the 21st century. Under these conditions, bioluminescent systems may be affected by this change in the reaction medium (ocean water). This meta-analysis surveyed previously published research and found 49 records including bioluminescent intensity and pH for a wide range of taxa. These data suggest the direction and magnitude of an ocean acidification effect is taxa-specific.

Continue reading ‘Turning up the lights: ocean acidification may increase light intensity of secretory bioluminescent signaling (text & video)’

Invariant gametogenic response of dominant infaunal bivalves from the Arctic under ambient and near-future climate change conditions

Arctic marine ecosystems are undergoing a series of major rapid adjustments to the regional amplification of climate change, but there is a paucity of knowledge about how changing environmental conditions might affect reproductive cycles of seafloor organisms. Shifts in species reproductive ecology may influence their entire life-cycle, and, ultimately, determine the persistence and distribution of taxa. Here, we investigate whether the combined effects of warming and ocean acidification based on near-future climate change projections affects the reproductive processes in benthic bivalves (Astarte crenata and Bathyarca glacialis) from the Barents Sea. Both species present large oocytes indicative of lecithotrophic or direct larval development after ∼4 months exposure to ambient [<2°C, ∼400 ppm (CO2)] and near-future [3–5°C, ∼550 ppm (CO2)] conditions, but we find no evidence that the combined effects of acidification and warming affect the size frequency distribution of oocytes. Whilst our observations are indicative of resilience of this reproductive stage to global changes, we also highlight that the successful progression of gametogenesis under standard laboratory conditions does not necessarily mean that successful development and recruitment will occur in the natural environment. This is because the metabolic costs of changing environmental conditions are likely to be offset by, as is common practice in laboratory experiments, feeding ad libitum. We discuss our findings in the context of changing food availability in the Arctic and conclude that, if we are to establish the vulnerability of species and ecosystems, there is a need for holistic approaches that incorporate multiple system responses to change.

Continue reading ‘Invariant gametogenic response of dominant infaunal bivalves from the Arctic under ambient and near-future climate change conditions’

Technical note: interpreting pH changes

The number and quality of ocean pH measurements have increased substantially over the past few decades such that trends, variability, and spatial patterns of change are now being evaluated. However, comparing pH changes across domains with different initial pH values can be misleading because a pH change reflects a relative change in the hydrogen ion concentration ([H+], expressed in mol kg−1) rather than an absolute change in [H+]. We recommend that [H+] be used in addition to pH when describing such changes and provide three examples illustrating why.

Continue reading ‘Technical note: interpreting pH changes’

Warm and bubbly: increasing ocean CO2 and temperature affect fish distribution

Based on the paper: Ocean acidification may slow the pace of tropicalization of temperate fish communities by Ericka O. C. Coni, Ivan Nagelkerken, Camilo M. Ferreira, Sean D. Connell & David J. Booth. Nature Climate Change (2021) https://www.nature.com/articles/s41558-020-00980-

Ocean warming is causing range-extensions of warm-adapted species into temperate waters, but the effects of ocean acidification on this process are largely unknown. Laboratory test are informative but cannot incorporate the ecological complexity of nature. We therefore used ecosystems experiencing natural warming and acidification as analogues of future climate to predict the future rate of tropicalization of temperate ecosystems.

Imagine if you find yourself in a place that you are not familiar with. A place where you are not adapted to the local climate and culture. What should you do to blend in? You must think of new ways to succeed under these new circumstances. This situation is similar to that of hundreds of tropical fish species (tropical vagrant fishes) that are extending their ranges to cooler, temperate regions as the ocean warms. For at least two decades, Australian temperate reefs have been receiving new guests from the tropics, but their successful colonisation depends on how they respond to and cope with unfamiliar conditions. Temperate ecosystems represent a potential hostile environment for tropical species. Familiar prey and habitats are absent there, novel predators and competitors are present, and survival and physiological performance is reduced by exposure to cold winter temperatures. Thus, tropical fishes have to adapt to these novel conditions to thrive.

Continue reading ‘Warm and bubbly: increasing ocean CO2 and temperature affect fish distribution’

Could seaweed be a salve to debate over salmon farming?

Seaweed is great at dealing with the waste from salmon farms and providing producers with another cash crop, says researcher Thierry Chopin. Photo by Steve Backman.

For well over a decade, scientists on Canada’s coasts have demonstrated how growing seaweed or shellfish alongside salmon farms can provide a host of benefits — economic and ecological.

Researcher Thierry Chopin has been pitching the idea of co-cultivating multiple species together, or Integrated Multi-Trophic Aquaculture (IMTA), since the late 1990s.

The notion behind co-cultivation, or IMTA, is that extractive species like seaweed, mussels, or sea cucumbers can filter or flourish from the uneaten feed, waste, and byproducts from fish farms.

Continue reading ‘Could seaweed be a salve to debate over salmon farming?’

Job opportunity: post-doc at NOAA-NMFS Alaska Fisheries Science Center

Ocean acidification is occurring throughout the world’s oceans due to the release of terrestrially sequestered CO2 into the atmosphere and the subsequent diffusion of that anthropogenically released CO2 into the ocean.

There is a significant concern that ocean acidification could disrupt the productivity of fishery species. This pattern of ocean acidification (OA) is co-occurring with long-term increases in the temperatures of the world’s oceans that have already been shown to impact distribution and abundance of marine organisms. High latitude seas are predicted to be most affected by the combination of rising temperatures and OA. Previous work on OA interactions with other environmental factors in Alaska groundfish has focused on the potential for OA-induced changes to prey production to exacerbate the direct physiological effects of OA on early life stages. There has yet been little research examining the interaction between OA and elevated temperatures on fish productivity. To address this understanding gap, we will examine the interactive effects of OA and elevated temperatures on three fish species that are critical to Alaska and Arctic fisheries and foodwebs: Pacific cod which supports a major regional fishery and has previously been shown to be sensitive to OA; yellowfin sole which supports the world’s largest flatfish fishery; and Arctic cod which is a keystone species throughout Arctic ecosystems.

The incumbent will work as part of a research team examining the interactive effects of temperature and CO2 on the early life stages of Alaska fishery species and will be responsible for conducting laboratory experiments, biological measurements, statistical analyses, and production of peer-reviewed manuscripts. Experiments will examine the growth and survival responses, with the incumbent expanding the scope of research with additional response metrics and experimentation based on individual interest, experience, and expertise. Candidates with experience in the experimental culture of marine organisms will be strongly encouraged to apply. Anticipated start date December 2021.

Continue reading ‘Job opportunity: post-doc at NOAA-NMFS Alaska Fisheries Science Center’

Physiological responses of Skeletonema costatum to the interactions of seawater acidification and the combination of photoperiod and temperature (update)

Ocean acidification (OA), which is a major environmental change caused by increasing atmospheric CO2, has considerable influences on marine phytoplankton. But few studies have investigated interactions of OA and seasonal changes in temperature and photoperiod on marine diatoms. In the present study, a marine diatom Skeletonema costatum was cultured under two different CO2 levels (LC, 400 µatm; HC, 1000 µatm) and three different combinations of temperature and photoperiod length (8:16 L:D with 5 C, 12:12 L:D with 15 C, 16:8 L:D with 25 C), simulating different seasons in typical temperate oceans, to investigate the combined effects of these factors. The results showed that specific growth rate of S. costatum increased with increasing temperature and day length. However, OA showed contrasting effects on growth and photosynthesis under different combinations of temperature and day length: while positive effects of OA were observed under spring and autumn conditions, it significantly decreased growth (11 %) and photosynthesis (21 %) in winter. In addition, OA alleviated the negative effect of low temperature and short day length on the abundance of RbcL and key photosystem II (PSII) proteins (D1 and D2). These data indicated that future ocean acidification may show differential effects on diatoms in different clusters of other factors.

Continue reading ‘Physiological responses of Skeletonema costatum to the interactions of seawater acidification and the combination of photoperiod and temperature (update)’

Guest post: The threat of high-probability ocean ‘tipping points’

Climate change is profoundly altering our oceans and marine ecosystems. Some of these changes are happening quickly and are potentially irreversible. Many are taking place silently and unnoticed.

In recent years, tipping points – thresholds where a small change could push a system into a completely new state – have increasingly become a focus for the climate research community.

However, these are typically thought of in terms of unlikely changes with huge global ramifications – often referred to as “low probability, high impact” events. Examples include the slowdown of the Atlantic Meridional Overturning Circulation and the rapid disintegration of the West Antarctic ice sheet

In a new paper, published in the Proceedings of the National Academy of Sciences, my co-authors and I instead focus on the potential for what we call “high probability, high impact” tipping points caused by the cumulative impact of warming, acidification and deoxygenation.

We present the challenge of dealing with these imminent and long-lasting changes in the Earth system, and discuss options for mitigation and management measures to avoid crossing these tipping points.

Continue reading ‘Guest post: The threat of high-probability ocean ‘tipping points’’

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