•Global change effects on HABs are often modified by local factors.•Interaction of environental factors complicataes multifactorial experiments.•HABs may become more severe as a result of acclimating ...to global change.•More studies are needed to determine genetic adaptation of HAB species to global change.
Rising concentrations of atmospheric CO2 results in higher equilibrium concentrations of dissolved CO2 in natural waters, with corresponding increases in hydrogen ion and bicarbonate concentrations and decreases in hydroxyl ion and carbonate concentrations. Superimposed on these climate change effects is the dynamic nature of carbon cycling in coastal zones, which can lead to seasonal and diel changes in pH and CO2 concentrations that can exceed changes expected for open ocean ecosystems by the end of the century. Among harmful algae, i.e. some species and/or strains of Cyanobacteria, Dinophyceae, Prymnesiophyceae, Bacillariophyceae, and Ulvophyceae, the occurrence of a CO2 concentrating mechanisms (CCMs) is the most frequent mechanism of inorganic carbon acquisition in natural waters in equilibrium with the present atmosphere (400 μmol CO2 mol−1 total gas), with varying phenotypic modification of the CCM. No data on CCMs are available for Raphidophyceae or the brown tide Pelagophyceae. Several HAB species and/or strains respond to increased CO2 concentrations with increases in growth rate and/or cellular toxin content, however, others are unaffected. Beyond the effects of altered C concentrations and speciation on HABs, changes in pH in natural waters are likely to have profound effects on algal physiology. This review outlines the implications of changes in inorganic cycling for HABs in coastal zones, and reviews the knowns and unknowns with regard to how HABs can be expected to ocean acidification. We further point to the large regions of uncertainty with regard to this evolving field.
The Neoproterozoic (1000–542 million years ago, Mya) was characterized by profound global environmental and evolutionary changes, not least of which included a major rise in atmospheric oxygen ...concentrations 1, 2, extreme climatic fluctuations and global-scale glaciation 3, and the emergence of metazoan life in the oceans 4, 5. We present here phylogenomic (135 proteins and two ribosomal RNAs, SSU and LSU) and relaxed molecular clock (SSU, LSU, and rpoC1) analyses that identify this interval as a key transition in the marine nitrogen cycle. Specifically, we identify the Cryogenian (850–635 Mya) as heralding the first appearance of both marine planktonic unicellular nitrogen-fixing cyanobacteria and non-nitrogen-fixing picocyanobacteria (Synechococcus and Prochlorococcus 6). Our findings are consistent with the existence of open-ocean environmental conditions earlier in the Proterozoic adverse to nitrogen-fixers and their evolution—specifically, insufficient availability of molybdenum and vanadium, elements essential to the production of high-yielding nitrogenases. As these elements became more abundant during the Cryogenian 7, 8, both nitrogen-fixing cyanobacteria and planktonic picocyanobacteria diversified. The subsequent emergence of a strong biological pump in the ocean implied by our evolutionary reconstruction may help in explaining increased oxygenation of the Earth’s surface at this time, as well as tendency for glaciation.
•Planktonic nitrogen-fixing cyanobacteria first evolved in the Neoproterozoic•Marine Synechococcus and Prochlorococcus evolved after planktonic nitrogen-fixers•The Cryogenian may have been the first time that the ocean was widely productive•Planktonic cyanobacteria likely had a major impact on ocean primary productivity
Using phylogenomic and molecular clock analyses, Sánchez-Baracaldo et al. pin down the common ancestor of modern planktonic nitrogen-fixing cyanobacteria to within a few hundred million years of the Cambrian explosion. Increasing ocean productivity may explain rising atmospheric oxygen and glaciation during the late Neoproterozoic.
The future of Blue Carbon science Macreadie, Peter I; Anton, Andrea; Raven, John A ...
Nature communications,
09/2019, Letnik:
10, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The term Blue Carbon (BC) was first coined a decade ago to describe the disproportionately large contribution of coastal vegetated ecosystems to global carbon sequestration. The role of BC in climate ...change mitigation and adaptation has now reached international prominence. To help prioritise future research, we assembled leading experts in the field to agree upon the top-ten pending questions in BC science. Understanding how climate change affects carbon accumulation in mature BC ecosystems and during their restoration was a high priority. Controversial questions included the role of carbonate and macroalgae in BC cycling, and the degree to which greenhouse gases are released following disturbance of BC ecosystems. Scientists seek improved precision of the extent of BC ecosystems; techniques to determine BC provenance; understanding of the factors that influence sequestration in BC ecosystems, with the corresponding value of BC; and the management actions that are effective in enhancing this value. Overall this overview provides a comprehensive road map for the coming decades on future research in BC science.
Background
Most terrestrial vascular plants can assimilate soil obtained NO
3
-
in their root and shoot.
Scope
Data from the literature are collated and analysed with respect to genotype and ...environmental effects on the partitioning of NO
3
-
assimilation between root and shoot of terrestrial vascular plants.
Conclusions
Temperate evergreen woody species in the Ericaceae and Pinaceae carry out most of their NO
3
-
assimilation in the root when growing in low (0.5 mM) up to at least 5 mM soil NO
3
-
. The root is the main site of NO
3
-
assimilation for temperate deciduous woody species and perennial and annual herbaceous legume species at 0.5–1 mM NO
3
-
but for many, shoot assimilation increases in importance with increased NO
3
-
supply. Temperate perennial grasses and annual non-legume species and tropical/ sub-tropical species regardless of life-form, carry out a substantial, usually major proportion of their NO
3
-
assimilation in shoots at NO
3
-
concentrations above 0.5 mM. Furthermore, high NH
4
+
supply, mycorrhizal infection and infection by parasitic plants can increase the proportion of total plant NO
3
-
assimilation carried out in the shoot while abiotic stress and elevated atmospheric CO
2
can cause this to decrease. Shoot NO
3
-
assimilation is an advantage under non-stress conditions due to its positive effect on leaf expansion but can be a disadvantage under freezing and chilling stress conditions. Increased reliance on root NO
3
-
assimilation at elevated CO
2
was associated with increased and conversely decreased plant growth and NO
3
-
assimilation depending on study. Resolution of these different findings across studies is an important area for further research.
Nitrogen (N) tends to limit plant productivity on young soils; phosphorus (P) becomes increasingly limiting in ancient soils because it gradually disappears through leaching and erosion. Plant traits ...that are regarded as adaptations to N- and P-limited conditions include mycorrhizas and cluster roots. Mycorrhizas ‘scavenge’ P from solution or ‘mine’ insoluble organic N. Cluster roots function in severely P-impoverished landscapes, ‘mining’ P fixed as insoluble inorganic phosphates. The ‘scavenging’ and ‘mining’ strategies of mycorrhizal species without and non-mycorrhizal species with cluster roots, respectively, allow functioning on soils that differ markedly in P availability. Based on recent advances in our understanding of these contrasting strategies of nutrient acquisition, we provide an explanation for the distribution of mycorrhizal species on less P-impoverished soils, and for why, globally, cluster-bearing species dominate on severely P-impoverished, ancient soils, where P sensitivity is relatively common.
Photolithotrophic growth on land using atmospheric CO2 inevitably involves H2O vapour loss. Embryophytes greater than or equal to 100 mm tall are homoiohydric and endohydric with mass flow of aqueous ...solution through the xylem in tracheophytes. Structural details in Rhynie sporophytes enable modelling of the hydraulics of H2O supply to the transpiring surface, and the potential for gas exchange with the Devonian atmosphere. Xylem carrying H2O under tension involves programmed cell death, rigid cell walls and embolism repair; fossils provide little evidence on these functions other than the presence of lignin. The phenylalanine ammonia lyase essential for lignin synthesis came from horizontal gene transfer. Rhynie plants lack endodermes, limiting regulation of the supply of soil nutrients to shoots. The transfer of organic solutes from photosynthetic sites to growing and storage tissues involves mass flow through phloem in extant tracheophytes. Rhynie plants show little evidence of phloem; possible alternatives for transport of organic solutes are discussed. Extant examples of the arbuscular mycorrhizas found in Rhynie plants exchange soil-derived nutrients (especially P) for plant-derived organic matter, involving bidirectional mass flow along the hyphae. The aquatic cyanobacteria and the charalean Palaeonitella at Rhynie also have long-distance (relative to the size of the organism) transport.
This article is part of a discussion meeting issue ‘The Rhynie cherts: our earliest terrestrial ecosystem revisited’.
Anthropogenic inputs are increasing the CO
2
content of the atmosphere, and the CO
2
and total inorganic C in the surface ocean and, to a lesser degree, the deep ocean. The greenhouse effect of the ...increased CO
2
(and, to a lesser extent, other greenhouse gases) is very probably the major cause of present global warming. The warming increases temperature of the atmosphere and the surface ocean to a greater extent than the deep ocean, with shoaling of the thermocline, decreasing nutrient flux to the surface ocean where there is greater mean photosynthetic photon flux density. These global changes influence algae in nature. However, it is clear that algae are important, via the biological pump, in decreasing the steady state atmospheric and ocean surface CO
2
, and thus decreasing radiative forcing, a reduction enhanced by algal increases in albedo. As well as these natural processes there are possibilities that algae can, with human intervention, partly offset the increase in atmospheric CO
2
. One possibility is to grow algae as sources of fuel for transport, in principle providing an energy source that is close to CO
2
-neutral. The other possibility is to increase the role of algae in sequestering CO
2
as organic C over periods of hundreds or more years in the deep ocean and marine sediments and/or increasing albedo and decreasing radiative forcing of temperature. There are problems, currently unresolved, in the economically viable production of algal biofuels without carbon trading subsidies. Enhanced algal CO
2
sequestration also has costs, both in resource input (phosphorus (P) from high P content rocks, a limited resource with a competing use as an agricultural fertilizer) and adverse environmental effects. For example, ocean anoxic zones producing N
2
O and increased algal production of short-lived halocarbons by algae that both, through breakdown, destroy O
3
and increase UV flux to the Earth's surface.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Carbon dioxide concentrating mechanisms (also known as inorganic carbon concentrating mechanisms; both abbreviated as CCMs) presumably evolved under conditions of low CO
2
availability. However, the ...timing of their origin is unclear since there are no sound estimates from molecular clocks, and even if there were, there are no proxies for the functioning of CCMs. Accordingly, we cannot use previous episodes of high CO
2
(e.g. the Palaeocene–Eocene Thermal Maximum) to indicate how organisms with CCMs responded. Present and predicted environmental change in terms of increased CO
2
and temperature are leading to increased CO
2
and HCO
3
−
and decreased CO
3
2−
and pH in surface seawater, as well as decreasing the depth of the upper mixed layer and increasing the degree of isolation of this layer with respect to nutrient flux from deeper waters. The outcome of these forcing factors is to increase the availability of inorganic carbon, photosynthetic active radiation (PAR) and ultraviolet B radiation (UVB) to aquatic photolithotrophs and to decrease the supply of the nutrients (combined) nitrogen and phosphorus and of any non-aeolian iron. The influence of these variations on CCM expression has been examined to varying degrees as acclimation by extant organisms. Increased PAR increases CCM expression in terms of CO
2
affinity, whilst increased UVB has a range of effects in the organisms examined; little relevant information is available on increased temperature. Decreased combined nitrogen supply generally increases CO
2
affinity, decreased iron availability increases CO
2
affinity, and decreased phosphorus supply has varying effects on the organisms examined. There are few data sets showing interactions amongst the observed changes, and even less information on genetic (adaptation) changes in response to the forcing factors. In freshwaters, changes in phytoplankton species composition may alter with environmental change with consequences for frequency of species with or without CCMs. The information available permits less predictive power as to the effect of the forcing factors on CCM expression than for their overall effects on growth. CCMs are currently not part of models as to how global environmental change has altered, and is likely to further alter, algal and aquatic plant primary productivity.
The effect of ocean acidification conditions has been investigated in cultures of the diatom Thalassiosira pseudonana CCMP1335. Expected end-of-the-century pCO(2) (aq) concentrations of 760 µatm ...(equivalent to pH 7.8) were compared with present-day condition (380 µatm CO(2), pH 8.1). Batch culture pH changed rapidly because of CO(2) (aq) assimilation and pH targets of 7.8 and 8.1 could not be sustained. Long-term (∼100 generation) pH-auxostat, continuous cultures could be maintained at target pH when cell density was kept low (<2×10(5) cells mL(-1)). After 3 months continuous culture, the C:N ratio was slightly decreased under high CO(2) conditions and red fluorescence per cell was slightly increased. However, no change was detected in photosynthetic efficiency (F(v)/F(m)) or functional cross section of PS II (σ(PSII)). Elevated pCO(2) has been predicted to be beneficial to diatoms due to reduced cost of carbon concentration mechanisms. There was reduced transcription of one putative δ-carbonic anhydrase (CA-4) after 3 months growth at increased CO(2) but 3 other δ-CAs and the small subunit of RUBISCO showed no change. There was no evidence of adaptation or clade selection of T. pseudonana after ∼100 generations at elevated CO(2). On the basis of this long-term culture, pH change of this magnitude in the future ocean may have little effect on T. pseudonana in the absence of genetic adaption.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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