Archive for May, 2019

The oceans are changing: impact of ocean warming and acidification on biofouling communities

Climate change (CC) is driving modification in the chemical and physical properties of estuaries and oceans with profound consequences for species and ecosystems. Numerous studies investigate its effect from species to ecosystem levels, however little is known on impacts on biofilm communities and bioactive molecules, like cues, glues, and enzymes. CC is induced by anthropogenic activity increasing greenhouse emissions leading to rises in air and water temperatures, ocean acidification, sea level rise and changes in ocean gyres and rainfall patterns. These environmental changes are resulting in alterations in marine communities and spreading of species (pathogens, invasives). This review provides insights and synthesis of knowledge about the effect of elevated temperature and ocean acidification on microfouling communities and bioactive molecules. The existing studies suggest that CC will impact production of bioactive compounds, growth and composition of biofouling communities. Undoubtedly, with CC fouling management will became an even greater challenge.

Continue reading ‘The oceans are changing: impact of ocean warming and acidification on biofouling communities’

Ocean acidification threatens the survival of coral reefs: study

The world’s coral reefs are under threat from ocean acidification with many corals unable to adapt to the conditions, according to a study.

The study, published in the journal Nature Climate Change, determined the capacity of coral reefs to acclimatize to ocean acidification by investigating the chemistry in the corals’ calcifying fluid.

Continue reading ‘Ocean acidification threatens the survival of coral reefs: study’

Day length as a key factor moderating the response of coccolithophore growth to elevated pCO2

The fate of coccolithophores in the future oceans remains uncertain, in part due to key factors having not been standardized across experiments. A potentially moderating role for differences in day length (photoperiod) remains largely unexplored. We therefore cultured four different geographical isolates of the species Emiliania huxleyi, as well as two additional species, Gephyrocapsa oceanica (tropical) and Coccolithus braarudii(temperate), to test for interactive effects of pCO2 with the light : dark (L : D) cycle. We confirmed a general regulatory effect of photoperiod on the pCO2 response, whereby growth and particulate inorganic carbon and particulate organic carbon (PIC : POC) ratios were reduced with elevated pCO2 under 14 : 10 h L : D, but these reductions were dampened under continuous (24 h) light. The dynamics underpinning this pattern generally differed for the temperate vs. tropical isolates. Reductions in PIC : POC with elevated pCO2 for tropical taxa were largely through reduced calcification and enhanced photosynthesis under 14 : 10 h L : D, with differences dampened under continuous light. In contrast, reduced PIC : POC for temperate strains reflected increases of photosynthesis that outpaced increases in calcification rates under 14 : 10 h L : D, with both responses again dampened under continuous light. A multivariate analysis of 35 past studies of E. huxleyi further demonstrated that differences in photoperiod account for as much as 40% (strain B11/92) to 55% (strain NZEH) of the variance in reported pCO2‐induced reductions to growth but not PIC : POC. Our study thus highlights a critical role for day length in moderating the effect of ocean acidification on coccolithophore growth and consequently how this response may play out across latitudes and seasons in future oceans.

Continue reading ‘Day length as a key factor moderating the response of coccolithophore growth to elevated pCO2’

A new software of calculating the pH values of coastal seawater: considering the effects of low molecular weight organic acids

Highlights

• Low molecular weight organic acids concentrations were high in the coastal seawater.

• Low molecular weight organic acids can reduce the pH value of the seawater.

• Software of Org·TCO2TA can more accurately calculate the pH of the coastal seawater.

Abstract

Effects of low molecular weight organic acids (LMWOAs) on the pH value of seawater were investigated in the surface seawater of the Jiaozhou Bay, China. The new software of Org·TCO2TA was developed to calculate the pH values of seawater based on the alkalinity (Alk) equation where organic acid Alk (Org-Alk) was separated into LMWOA Alk (LMWOA-Alk) and humic acid Alk (HA-Alk). In the calculations, all dissociation constants of organic acids were from previous literature. In our study, the average concentration of total LMWOAs was 14.5 ± 11.2 μmol·kg−1 SW. pH values from the Org·TCO2TA software were closer to the pH values from spectrophotometric measurement than those from the CO2SYS program, indicating pH values can be influenced by high concentrations of LMWOAs in coastal seawater of the Jiaozhou Bay. Although the differences still existed between the pH values from the spectrophotometric method and the calculated pH values from the Org·TCO2TA software due to the influence of various factors, including the analytical errors of dissolved inorganic carbon and nutrients, the new software can calculate the pH values of coastal seawater more accurately by considering the effects of LMWOAs.

Continue reading ‘A new software of calculating the pH values of coastal seawater: considering the effects of low molecular weight organic acids’

Coral reefs can’t return from acid trip

coral-reefs

Crustose coralline algae amongst brown algae, Rottnest Island. Credit: Chris Cornwall

A new study published this week in Nature Climate Change finds coral reefs are under threat from ocean acidification.

The study was led by researchers from the ARC Centre of Excellence for Coral Reef Studies (Coral CoE). Their results suggest some corals and coralline algae—the ‘glue’ that holds reefs together—cannot survive the expected more acidic oceans caused by climate change.

“The results validate previous research on ocean acidification threats to coral reefs,” said lead author Dr. Steeve Comeau, who is now based at the Sorbonne Université CNRS Laboratoire d’Océanographie de Villefranche sur Mer in France.

Continue reading ‘Coral reefs can’t return from acid trip’

An experimental evaluation of the sensitivity of coastal marine fishes to acidification, hypoxia, and warming

Ocean acidification (OA) during the coming century will impact marine ecosystems in profound ways. Laboratory studies have played a pioneering role in identifying biological vulnerabilities and have documented deleterious effects in taxonomically diverse fauna. The early life-stages of marine fish may be particularly sensitive to OA, thereby constituting a global threat to some of the world’s most important marine resources. Despite the rapid accumulation of experimental evidence, considerable uncertainty remains in estimating the scope of OA impacts. To date, most studies have relied on relatively short-term exposures to estimate effects of elevated pCO, while few have considered longer term OA effect across multiple life-stages. Additionally, while single-factor CO2 experiments are a necessary first step in identifying OA sensitivities, there is a growing understanding that OA will proceed concurrently with warming and deoxygenation, yet multi-stressor factorial experiments remain rare. Furthermore, meta-analyses of existing research have highlighted the large, and thus far unexplained variability in OA responses among taxa and populations. One promising mechanism which could explain this variability involves the role of local adaptation to existing pCO2fluctuations that characterizes marine habitats to different degrees. This framework remains untested in fish. The primary goal of this dissertation was to apply state-of-the-art experimental techniques to address the aforementioned knowledge gaps. By using two ecological important forage species, the Atlantic silverside (Menidia menidia) and Northern sand lance (Ammodytes dubius) with contrasting life-history characteristics, this dissertation provides novel insights into potential near-future climate impacts on fish. Chapter 1 summarizes a long-term OA experiment on M. menidia finding that elevated pCO2 exposure resulted in small but significant reductions in offspring size and condition factor. Chapter 2 tested CO2 × temperature effects in M. menidia offspring and found complex growth and survival responses. Chapter 3 reports on CO2 × temperature trials on offspring of A. dubius and documented precipitous reductions to survival and growth. Chapter 4 describes two CO2 × dissolved oxygen trials on M. menidia offspring that demonstrated a negative synergistic effect on embryonic survival. Together, this dissertation provides much needed baseline data and novel insights into climate effects in forage fish.

Continue reading ‘An experimental evaluation of the sensitivity of coastal marine fishes to acidification, hypoxia, and warming’

Resistance to ocean acidification in coral reef taxa is not gained by acclimatization

Ocean acidification (OA) is a major threat to coral reefs, which are built by calcareous species. However, long-term assessments of the impacts of OA are scarce, limiting the understanding of the capacity of corals and coralline algae to acclimatize to high partial pressure of carbon dioxide (pCO2) levels. Species-specific sensitivities to OA are influenced by its impacts on chemistry within the calcifying fluid (CF). Here, we investigate the capacity of multiple coral and calcifying macroalgal species to acclimatize to elevated pCO2 by determining their chemistry in the CF during a year-long experiment. We found no evidence of acclimatization to elevated pCO2 across any of the tested taxa. The effects of increasing seawater pCO2 on the CF chemistry were rapid and persisted until the end of the experiment. Our results show that acclimatization of the CF chemistry does not occur within one year, which confirms the threat of OA for future reef accretion and ecological function.

Continue reading ‘Resistance to ocean acidification in coral reef taxa is not gained by acclimatization’

Harmful algal blooms: a climate change co-stressor in marine and freshwater ecosystems

Highlights

• Harmful algal blooms (HABs) are intensifying in parallel with climate change.
• Few studies have followed interactive effects between climate change stressors and HAB species.
• Future studies with HAB species should consider incorporating multiple climate change stressors.

Abstract

Marine and freshwater ecosystems are warming, acidifying, and deoxygenating as a consequence of climate change. In parallel, the impacts of harmful algal blooms (HABs) on these ecosystems are intensifying. Many eutrophic habitats that host recurring HABs already experience thermal extremes, low dissolved oxygen, and low pH, making these locations potential sentinel sites for conditions that will become more common in larger-scale systems as climate change accelerates. While studies of the effects of HABs or individual climate change stressors on aquatic organisms have been relatively common, studies assessing their combined impacts have been rare. Those doing so have reported strong species- and strain-specific interactions between HAB species and climate change co-stressors yielding outcomes for aquatic organisms that could not have been predicted based on investigations of these factors individually. This review provides an ecological and physiological framework for considering HABs as a climate change co-stressor and considers the consequences of their combined occurrence for coastal ecosystems. This review also highlights critical gaps in our understanding of HABs as a climate change co-stressor that must be addressed in order to develop management plans that adequately protect fisheries, aquaculture, aquatic ecosystems, and human health. Ultimately, incorporating HAB species into experiments and monitoring programs where the effects of multiple climate change stressors are considered will provide a more ecologically relevant perspective of the structure and function of marine ecosystems in future, climate-altered systems.

Continue reading ‘Harmful algal blooms: a climate change co-stressor in marine and freshwater ecosystems’

Surface ocean carbon dioxide variability in South Pacific boundary currents and Subantarctic waters

To improve estimates of the long-term response of the marine carbon system to climate change a better understanding of the seasonal and interannual variability is needed. We use high-frequency multi-year data at three locations identified as climate change hotspots: two sites located close to South Pacific boundary currents and one in the Subantarctic Zone (SAZ). We investigate and identify the main drivers involved in the seasonal an interannual (2012–2016) variability of the carbon system. The seasonal variability at boundary current sites is temporally different and highly controlled by sea surface temperature. Advection processes also play a significant role on the monthly changes of the carbon system at the western boundary current site. The interannual variability at these sites most likely responds to long-term variability in oceanic circulation ultimately related to climatic indices such as the El Niño Southern Oscillation, the Pacific Decadal Oscillation and the Southern Annular Mode (SAM). In the SAZ, advection and entrainment processes drive most of the seasonality, augmented by the action of biological processes in spring. Given the relevance of advection and entrainment processes at SAZ, the interannual variability is most probably modulated by changes in the regional winds linked to the variability of the SAM.

Continue reading ‘Surface ocean carbon dioxide variability in South Pacific boundary currents and Subantarctic waters’

Seawater acidification and temperature modulate anti-predator defenses in two co-existing Mytilus species

Highlights

• Predator, pH and temperature affected the mussels’ anti-predator behaviour.

• Species specific effects were observed between Mytilus coruscus and Mytilus edulis.

• Low pH and high temperature reduced the anti-predation performance of mussels.

• Predator induced mussel clustering while low pH and warming had negative effects.

Abstract

The effects of short-term (7 days) experimental ocean acidification (−0.4 pH units) and warming (+5 °C) on anti-predator defenses of two sympatric Mytilus species from China, M. coruscus and M. edulis, in the presence and absence of predator cues were investigated. Results suggested species-specific independent negative effects of acidification and warming on the number and weight of byssal threads, the force of thread attachment, and total thread plaque area. Similar negative effects were observed for clustering behaviour, with acidification and warming independently increasing the number of solitary individuals and decreasing the percentage of mussels in clusters. Acidification effects on byssus were strongly exacerbated when predators were present. Ultimately, this study suggests that short-term exposure to experimental warming and acidification can negatively impact anti-predator defense strategies in mussels with potential ramifications for predator-prey interactions and ecological functioning in systems where mussel beds play a key ecological role.

Continue reading ‘Seawater acidification and temperature modulate anti-predator defenses in two co-existing Mytilus species’


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Ocean acidification in the IPCC AR5 WG II

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