Posts Tagged 'BRcommunity'

Influence of acidification and warming of seawater on biofouling by bacteria grown over API 5L steel

The acidification and warming of seawater have several impacts on marine organisms, including over microorganisms. The influence of acidification and warming of seawater on biofilms grown on API 5L steel surfaces was evaluated by sequencing the 16S ribosomal gene. For this, three microcosms were designed, the first simulating the natural marine environment (MCC), the second with a decrease in pH from 8.1 to 7.9, and an increase in temperature by 2 °C (MMS), and the third with pH in around 7.7 and an increase in temperature of 4 °C (MES). The results showed that MCC was dominated by the Gammaproteobacteria class, mainly members of the Alteromonadales Order. The second most abundant group was Alphaproteobacteria, with a predominance of Rhodobacterales and Oceanospirillales. In the MMS system there was a balance between representatives of the Gammaproteobacteria and Alphaproteobacteria classes. In MES there was an inversion in the representations of the most prevalent classes previously described in MCC. In this condition, there was a predominance of members of the Alphaproteobacteria Class, in contrast to the decrease in the abundance of Gammaproteobacteria members. These results suggest that possible future climate changes may influence the dynamics of the biofouling process in surface metals.

Continue reading ‘Influence of acidification and warming of seawater on biofouling by bacteria grown over API 5L steel’

Feedback mechanisms stabilise degraded turf algal systems at a CO2 seep site

Human activities are rapidly changing the structure and function of coastal marine ecosystems. Large-scale replacement of kelp forests and coral reefs with turf algal mats is resulting in homogenous habitats that have less ecological and human value. Ocean acidification has strong potential to substantially favour turf algae growth, which led us to examine the mechanisms that stabilise turf algal states. Here we show that ocean acidification promotes turf algae over corals and macroalgae, mediating new habitat conditions that create stabilising feedback loops (altered physicochemical environment and microbial community, and an inhibition of recruitment) capable of locking turf systems in place. Such feedbacks help explain why degraded coastal habitats persist after being initially pushed past the tipping point by global and local anthropogenic stressors. An understanding of the mechanisms that stabilise degraded coastal habitats can be incorporated into adaptive management to better protect the contribution of coastal systems to human wellbeing.

Continue reading ‘Feedback mechanisms stabilise degraded turf algal systems at a CO2 seep site’

Transgenerational effects on the coral Pocillopora damicornis microbiome under ocean acidification

Reef-building corals are inhabited by functionally diverse microorganisms which play important roles in coral health and persistence in the Anthropocene. However, our understanding of the complex associations within coral holobionts is largely limited, particularly transgenerational exposure to environmental stress, like ocean acidification. Here we investigated the microbiome development of an ecologically important coral Pocillopora damicornis following transgenerational exposure to moderate and high pCO2 (partial pressure of CO2) levels, using amplicon sequencing and analysis. Our results showed that the Symbiodiniaceae community structures in adult and juvenile had similar patterns, all of which were dominated by Durusdinium spp., previously known as clade D. Conversely, prokaryotic communities varied between adults and juveniles, possibly driven by the effect of host development. Surprisingly, there were no significant changes in both Symbiodiniaceae and prokaryotic communities with different pCO2 treatments, which was independent of the life history stage. This study shows that ocean acidification has no significant effect on P. damicornis microbiome, and warrants further research to test whether transgenerational acclimation exists in coral holobiont to projected future climate change.

Continue reading ‘Transgenerational effects on the coral Pocillopora damicornis microbiome under ocean acidification’

Ocean acidification may slow the pace of tropicalization of temperate fish communities

Poleward range extensions by warm-adapted sea urchins are switching temperate marine ecosystems from kelp-dominated to barren-dominated systems that favour the establishment of range-extending tropical fishes. Yet, such tropicalization may be buffered by ocean acidification, which reduces urchin grazing performance and the urchin barrens that tropical range-extending fishes prefer. Using ecosystems experiencing natural warming and acidification, we show that ocean acidification could buffer warming-facilitated tropicalization by reducing urchin populations (by 87%) and inhibiting the formation of barrens. This buffering effect of CO2 enrichment was observed at natural CO2 vents that are associated with a shift from a barren-dominated to a turf-dominated state, which we found is less favourable to tropical fishes. Together, these observations suggest that ocean acidification may buffer the tropicalization effect of ocean warming against urchin barren formation via multiple processes (fewer urchins and barrens) and consequently slow the increasing rate of tropicalization of temperate fish communities.

Continue reading ‘Ocean acidification may slow the pace of tropicalization of temperate fish communities’

Impacts of climate change on methylmercury formation and bioaccumulation in the 21st century ocean

Highlights

  • Seawater MeHg may increase in the polar oceans and decrease in the North Atlantic in 2100
  • Plankton MeHg may increase at high latitudes and decrease at mid to low latitudes
  • Ocean acidification leads to different spatial patterns compared with physical factors

Summary

Climate change-driven alterations to marine biogeochemistry will impact the formation and trophic transfer of the bioaccumulative neurotoxin methylmercury (MeHg) in the global ocean. We use a 3D model to examine how MeHg might respond to changes in primary production and plankton community driven by ocean acidification and alterations in physical factors (e.g., ocean temperature, circulation). Productivity changes lead to significant increases in seawater MeHg in the polar oceans and a decrease in the North Atlantic Ocean. Phytoplankton MeHg may increase at high latitudes and decrease in lower latitudes due to shifts in community structure. Ocean acidification might enhance phytoplankton MeHg uptake by promoting the growth of a small species that efficiently accumulate MeHg. Non-linearities in the food web structure lead to differing magnitudes of zooplankton MeHg changes relative to those for phytoplankton. Climate-driven shifts in marine biogeochemistry thus need to be considered when evaluating future trajectories in biological MeHg concentrations.

Continue reading ‘Impacts of climate change on methylmercury formation and bioaccumulation in the 21st century ocean’

Community responses of intertidal foraminifera to pH variations: a culture experiment with propagules

Calcifying organisms such as benthic foraminifera are susceptible to changes in ocean pH and alkalinity. Responses to these changes include variations in mortality, calcification rates or assemblage composition, which have been observed in field and experimental studies. Here we applied a growth experiment with benthic foraminiferal propagules under different pH conditions to gather insights into the effect of pH on the composition of grown assemblages. A homogeneous propagule assemblage from a local mudflat in Corfu Island (Greece) was exposed to a range of pH conditions (6.5, 7.2, 7.8 and 8.5) for 5 weeks. In a second experiment, the assemblages were first exposed to low and subsequently to high conditions for a total of 8 weeks. After termination of the experiments, we recorded high survivability and growth throughout the treatments. Analysis of the assemblage composition of the first experiments revealed a shift from porcelaneous dominated taxa in the higher pH treatments to an assemblage with higher numbers of agglutinated taxa in the lower pH treatments. Soft-shelled monothalamous species were common throughout. The second experiment revealed assemblages that were significantly dominated by porcelaneous taxa with monothalamous taxa being almost absent. The results of this study are congruent with other observations on changing assemblage compositions with changing pH from both laboratory and field studies. The fast response of the assemblages through activation of potentially dormant propagules adds insights into the mechanisms behind seasonal composition changes in naturally variable environments such as river estuaries. They also shed new light on possible effects of continuous decreases in ocean pH on shallow-water foraminiferal assemblages in future.

Continue reading ‘Community responses of intertidal foraminifera to pH variations: a culture experiment with propagules’

Phosphorus enrichment masked the negative effects of ocean acidification on picophytoplankton and photosynthetic performance in the oligotrophic Indian Ocean

Highlights

  • High pCO2 and P interactively increased the abundances of Syn, Pro and PEuks.
  • Rising pCO2 alone decreased the abundances of Syn, Pro and PEuks.
  • Elevated pCO2 alone facilitated the NPQNSV process significantly.
  • There was a strong coupling of picophytoplankton and the charge separation rates.
  • P enrichment masked the negative effects of OA on picophytoplankton and photosynthesis.

Abstract

Dynamics of picophytoplankton and photosynthesis will be inevitably impacted by changing marine environment, such as ocean acidification and nutrient supply, but related studies are very scarce. Here we cultured the picophytoplankton-dominated surface water of the oligotrophic Eastern Indian Ocean (EIO; R/V Shiyan-3, 20 March to 18 May 2019) at two levels of pCO2 (400 and 1000 ppm) and phosphate (0.05 and 1.50 µM) to investigate the interactive effects of elevated pCO2 and phosphate (P) on the dynamics of picophytoplankton and photosynthetic properties. High pCO2 and P levels interactively increased the abundances of SynechococcusProchlorococcus and picoeukaryotes by 33%, 18%, and 21%, respectively, of which high P level had a major promoting effect. Conversely, rising pCO2 alone decreased their abundances by 9%, 32%, and 46%, respectively. For the photophysiological responses in relation to the combination of high pCO2 and P levels, there was an increase in the maximum (Fv/Fm) and effective (Fq‘/Fm‘) photochemical efficiency, the electron transfer rates (ETRRCII) and the charge separation rates (JVPSII, an indicator of primary production), but a decrease in the non-photochemical quenching (NPQNSV). Elevated pCO2 alone facilitated the NPQNSV process significantly, ultimately leading to reduced light use efficiency (e.g., Fv/Fm, Fq‘/Fm‘ and ETRRCII) and primary production (JVPSII). There was a strong coupling of picophytoplankton and JVPSII, suggesting the EIO primary productivity was potentially controlled by picophytoplankton. Overall, our results indicate that the negative effects caused by ocean acidification may be masked or outweighted by the role that P availability plays in regulating growth and metabolism in this oligotrophic ecosystem.

Continue reading ‘Phosphorus enrichment masked the negative effects of ocean acidification on picophytoplankton and photosynthetic performance in the oligotrophic Indian Ocean’

Unexpected high abundance of aragonite-forming Nanipora (Octocorallia: Helioporacea) at an acidified volcanic reef in southern Japan

Nanipora Miyazaki & Reimer, 2015 is a recently discovered genus of aragonite-skeleton producing octocorals closely related to the blue coral genus Heliopora de Blainville, 1830. Since its discovery, Nanipora has been reported from coral reefs in Okinawa, Japan, and Thailand, and from seagrass beds in the northern South China Sea. However, it remains little known and studied. Here, we report on the unexpected discovery of an abundance of Nanipora colonies in shallow waters less than 2-m deep around a CO2 vent from the uninhabited volcanic island of Iwotorishima, Okinawa, in southern Japan. Nanipora colonies were found covering both coral rubble and hard substrates, alongside a few soft coral and zoantharian species. Polyps were pale white in color with none brown or darker in coloration as in some recent reports. As the original description of Nkamurai from Zamami Island in Okinawa describes the species as azooxanthellate, as the current Iwotorishima specimens also appear to be, and recently reported specimens from Thailand, Dongsha Atoll, and Yaeyama are zooxanthellate, it may be that there are more than one Nanipora species; the type species Nkamurai that is also likely at Iwotorishima, and a zooxanthellate species that constitutes the other records. Although Nanipora is not well studied, its presence at this volcanic CO2 seep suggests it has the ability to survive under unique and extreme environmental conditions, rendering it as a potentially important subject of study in the face of increasing ocean acidification.

Continue reading ‘Unexpected high abundance of aragonite-forming Nanipora (Octocorallia: Helioporacea) at an acidified volcanic reef in southern Japan’

Phytoplankton community structure changes during autumn and spring in response to environmental variables in Methana, Saronikos Gulf, Greece

Phytoplankton community was investigated during two contrasting periods using offshore plankton samples in the volcanic area of Methana peninsula (Saronikos Gulf): the first at early autumn (warm period, September 2016) and the second one at early spring (cold period, March 2017). In order to investigate the phytoplankton community structure in the complex geo-biochemical conditions of the area, samples were collected from stations near the CO2 hydrothermal vents, at the hydrothermal sulfur and radioactive springs and at a fishery nearby Methana town. Three major phytoplankton groups, Bacillariophyceae, Dinophyceae, and Prymnesiophyceae, were studied, using inverted microscopy. In early autumn, Dinophyceae were dominant in the majority of the stations with cell concentrations of Prorocentrum spp. up to ~ 35.5 × 103 cells l−1. In early spring, the dominant class was Bacillariophyceae with dominant genus Nitzschia/Pseudo-nitzschia presenting cell concentrations up to ~ 33.9 × 103 cells l−1. Furthermore, Prymnesiophyceae appeared in both spring and autumn samples with small fluctuations. Total phytoplankton cell concentrations followed a seasonal trend, presenting slightly lower values in the hydrothermal-effected area in comparison with the broader Saronikos Gulf, confirming the prevalence of oligotrophic conditions. Seasonal variation was very strong, revealing an association with water temperature and nutrient content. Those environmental variables proved to have a strong effect that was reflected in the phytoplankton community structure.

Continue reading ‘Phytoplankton community structure changes during autumn and spring in response to environmental variables in Methana, Saronikos Gulf, Greece’

Ocean acidification decreases grazing pressure but alters morphological structure in a dominant coastal seaweed

Ocean acidification driven by anthropogenic climate change is causing a global decrease in pH, which is projected to be 0.4 units lower in coastal shallow waters by the year 2100. Previous studies have shown that seaweeds grown under such conditions may alter their growth and photosynthetic capacity. It is not clear how such alterations might impact interactions between seaweed and herbivores, e.g. through changes in feeding rates, nutritional value, or defense levels. Changes in seaweeds are particularly important for coastal food webs, as they are key primary producers and often habitat-forming species. We cultured the habitat-forming brown seaweed Fucus vesiculosus for 30 days in projected future pCO2 (1100 μatm) with genetically identical controls in ambient pCO2 (400 μatm). Thereafter the macroalgae were exposed to grazing by Littorina littorea, acclimated to the relevant pCO2-treatment. We found increased growth (measured as surface area increase), decreased tissue strength in a tensile strength test, and decreased chemical defense (phlorotannins) levels in seaweeds exposed to high pCO2-levels. The herbivores exposed to elevated pCO2-levels showed improved condition index, decreased consumption, but no significant change in feeding preference. Fucoid seaweeds such as Fvesiculosus play important ecological roles in coastal habitats and are often foundation species, with a key role for ecosystem structure and function. The change in surface area and associated decrease in breaking force, as demonstrated by our results, indicate that Fvesiculosus grown under elevated levels of pCO2 may acquire an altered morphology and reduced tissue strength. This, together with increased wave energy in coastal ecosystems due to climate change, could have detrimental effects by reducing both habitat and food availability for herbivores.

Continue reading ‘Ocean acidification decreases grazing pressure but alters morphological structure in a dominant coastal seaweed’

Subscribe to the RSS feed

Powered by FeedBurner

Follow AnneMarin on Twitter

Blog Stats

  • 1,426,001 hits

OA-ICC HIGHLIGHTS

Ocean acidification in the IPCC AR5 WG II

OUP book

Archives