•Clear variation in coccolithophore growth and mortality rates throughout April.•An Emiliania huxleyi bloom had exceptionally high rates of calcite production in April.•Microzooplankton grazing ...exerted strong top-down control on coccolithophores.•The fate of grazed calcite (dissolution or export) is an unknown but key consideration.
Coccolithophores are key components of phytoplankton communities, exerting a critical impact on the global carbon cycle and the Earth’s climate through the production of coccoliths made of calcium carbonate (calcite) and bioactive gases. Microzooplankton grazing is an important mortality factor in coccolithophore blooms, however little is currently known regarding the mortality (or growth) rates within non-bloom populations. Measurements of coccolithophore calcite production (CP) and dilution experiments to determine microzooplankton (≤63 µm) grazing rates were made during a spring cruise (April 2015) at the Central Celtic Sea (CCS), shelf edge (CS2), and within an adjacent April bloom of the coccolithophore Emiliania huxleyi at station J2.
CP at CCS ranged from 10.4 to 40.4 µmol C m−3 d−1 and peaked at the height of the spring phytoplankton bloom (peak chlorophyll-a concentrations ∼6 mg m−3). Cell normalised calcification rates declined from ∼1.7 to ∼0.2 pmol C cell−1 d−1, accompanied by a shift from a mixed coccolithophore species community to one dominated by the more lightly calcified species E. huxleyi and Calciopappus caudatus. At the CCS, coccolithophore abundance increased from 6 to 94 cells mL−1, with net growth rates ranging from 0.06 to 0.21 d−1 from the 4th to the 28th April. Estimates of intrinsic growth and grazing rates from dilution experiments, at the CCS ranged from 0.01 to 0.86 d−1 and from 0.01 to 1.32 d−1, respectively, which resulted in variable net growth rates during April. Microzooplankton grazers consumed 59 to >100% of daily calcite production at the CCS. Within the E. huxleyi bloom a maximum density of 1986 cells mL−1 was recorded, along with CP rates of 6000 µmol C m−3 d−1 and an intrinsic growth rate of 0.29 d−1, with ∼80% of daily calcite production being consumed.
Our results show that microzooplankton can exert strong top-down control on both bloom and non-bloom coccolithophore populations, grazing over 60% of daily growth (and calcite production). The fate of consumed calcite is unclear, but may be lost either through dissolution in acidic food vacuoles, and subsequent release as CO2, or export to the seabed after incorporation into small faecal pellets. With such high microzooplankton-mediated mortality losses, the fate of grazed calcite is clearly a high priority research direction.
Clay mineral growth can directly affect the chemistry and permeability of many natural systems, including soils, marine sediments, Earth surface waters, geothermal powerplants and carbon dioxide ...storage sites. Notably, the sluggish precipitation of clay minerals has been hypothesised to hinder Earth surface weathering rates. To date, there are limited data on the rate of clay mineral growth and on the effect of the aqueous solution saturation states on these rates. In this study we quantify the growth and dissolution rates of sepiolite, a 2:1 layered Mg-phyllosilicate (Mg4Si6O15(OH)2 * 6H2O) as a function of aqueous solution saturation state in a series of mixed flow experiments. Results of the both the dissolution and growth experiments are consistent with r=-10-14.801-expΔGrσRT, where r refers to the surface area normalized growth rate of sepiolite in units of mol/cm2/s, ΔGr denotes Gibbs Free energy of the sepiolite dissolution reaction, which is <0 for undersaturated solutions, 0 at equilibrium and >0 for supersaturated solutions, σ refers to Temkin’s stoichiometric number, R stands for the gas constant and T symbolizes absolute temperature. This rate equation suggests that sepiolite dissolution and growth are consistent with transition state theory and the concept of micro-reversibility. The relative decrease in aqueous Mg2+ and Si concentrations in the outlet aqueous solutions of the experiments, and the X-Ray diffraction patterns of the precipitates collected from the experiments, confirm the growth of crystalline sepiolite. The results of longer-term experiments suggest that sepiolite growth rates decrease over time. Such a decrease in the growth rate has been associated with poisoning or destruction of the sepiolite reactive surface sites. Calculations of sepiolite growth coupled to either forsterite or enstatite dissolution, based on laboratory measured rates suggest that the dissolution of the primary mineral is the rate-limiting step during the weathering of most natural systems. These results, however, contradict the saturation states of natural fluids such as observed in Icelandic waters, where clays are strongly supersaturated, whilst primary phases are relatively close to equilibrium. This discrepancy may be due to the consumption of reactive sites over time such that clay mineral precipitation rates in most natural systems are controlled by the relative slow nucleation rates of new reactive sites on the clay mineral surface.
Understanding the conditions that promote the evolution of migration is important in ecology and evolution. When environments are fixed and there is one most favorable site, migration to other sites ...lowers overall growth rate and is not favored. Here we ask, can environmental variability favor migration when there is one best site on average? Previous work suggests that the answer is yes, but a general and precise answer remained elusive. Here we establish new, rigorous inequalities to show (and use simulations to illustrate) how stochastic growth rate can increase with migration when fitness (dis)advantages fluctuate over time across sites. The effect of migration between sites on the overall stochastic growth rate depends on the difference in expected growth rates and the variance of the fluctuating difference in growth rates. When fluctuations (variance) are large, a population can benefit from bursts of higher growth in sites that are worse on average. Such bursts become more probable as the between-site variance increases. Our results apply to many (≥ 2) sites, and reveal an interplay between the length of paths between sites, the average differences in site-specific growth rates, and the size of fluctuations. Our findings have implications for evolutionary biology as they provide conditions for departure from the reduction principle, and for ecological dynamics: even when there are superior sites in a sea of poor habitats, variability and habitat quality across space determine the importance of migration.
The demand for large-scale and long-term information on tree growth is increasing rapidly as environmental change research strives to quantify and forecast the impacts of continued warming on forest ...ecosystems. This demand, combined with the now quasi-global availability of tree-ring observations, has inspired researchers to compile large tree-ring networks to address continental or even global-scale research questions. However, these emergent spatial objectives contrast with paleo-oriented research ideas that have guided the development of many existing records. A series of challenges related to how, where, and when samples have been collected is complicating the transition of tree rings from a local to a global resource on the question of tree growth. Herein, we review possibilities to scale tree-ring data (A) from the sample to the whole tree, (B) from the tree to the site, and (C) from the site to larger spatial domains. Representative tree-ring sampling supported by creative statistical approaches is thereby key to robustly capture the heterogeneity of climate-growth responses across forested landscapes. We highlight the benefits of combining the temporal information embedded in tree rings with the spatial information offered by forest inventories and earth observations to quantify tree growth and its drivers. In addition, we show how the continued development of mechanistic tree-ring models can help address some of the non-linearities and feedbacks that complicate making inference from tree-ring data. By embracing scaling issues, the discipline of dendrochronology will greatly increase its contributions to assessing climate impacts on forests and support the development of adaptation strategies.
•Scaling issues complicate the growing use of tree rings in large-spatial analyses.•New tree-ring networks should represent and quantify forest growth across scales.•Forest plot and remote sensing data help account for non-climatic drivers of growth.•Hind- and forecasting tree growth requires broadly applicable mechanistic models.•Dendrochronology needs new quality criteria for the collection and scaling of data.
Growth rates from 1480 Arctica islandica from New Jersey, collected in 2019 from north and south of the Hudson Canyon, were analyzed and compared to animals obtained from Long Island and Georges ...Bank. New Jersey represents the southern portion of the A. islandica stock in the Mid-Atlantic Bight, and animals here may experience warmer temperatures compared to their northern counterparts. Arctica islandica from New Jersey have slower maximum growth rates compared to northern A. islandica, particularly from Georges Bank; however, A. islandica from south of the Hudson Canyon have higher growth rates at older ages compared to the other three sites. Growth rates have been increasing over the past three centuries, potentially due to increasing bottom water temperatures, with time to maturity and time to commercial size drastically decreasing, leading to fewer years for reproduction prior to recruiting into the fishery. Three growth models, von Bertalanffy, Tanaka, and modified Tanaka were examined for goodness of fit to growth data. The von Bertalanffy, commonly used in fisheries management, had the worst fit for all populations, males and females, and at all 20-year cohort groups, and should not be used in the management of this species. The Tanaka and modified Tanaka models are recommended in its place, as these models best fit A. islandica growth at young (Tanaka) and older (>160 years, modified Tanaka) ages.
•Arctica islandica are thought to grow faster at the southern portion of their range.•Growth rates of A. islandica from four sites were compared and analyzed.•Growth rates at all four sites have increased over the past three centuries.•Three growth models were applied to determine best fit for management purposes.•The most commonly used growth model in management, von Bertalanffy, fit the worst.
The aim of this study was to evaluate morphophysiological indices, phenology and cutting time of forage cactus (Opuntia and Nopalea spp.) clones intercropped with sorghum cultivars (Sorghum bicolor). ...The experiment was carried out from 2017 to 2018, in two cropping systems (monocropping and intercropping), comprising 12 treatments, consisted of three cactus clones: 'IPA Sertânia'-IPA, 'Miúda'-Miu and 'Orelha de Elefante Mexicana'- OEM, in a monocropping system and nine combinations the cacti and sorghum (cultivars 467, SF11 and 2502) to comprise each of the intercropping systems. Cladodes morphophysiological indices were obtained: absolute growth rate, relative growth rate, net assimilation rate (NAR), specific cladode area rate (SCAR) and the cladode area index rate. OEM showed higher absolute growth rates at the beginning of the cycle, compared with IPA and Miu. NAR was higher in the monocropped OEM and in the OEM-2502 intercrop than under all the IPA and Miu systems (monocropping and intercropping), but the SCAR rate was higher for IPA (monocrop and intercropped). Miu showed a shorter duration of phenophase 2, but OEM had a higher rate of cladode emission during this phase. Cactus-sorghum intercropping systems cause a significant reduction in growth rates of the forage cactus. Intercropping has an earlier cutting time than the monocropping.
•Growth rates of D. acuminata and D. ovum strains were unaffected by varying light intensity.•High light intensity inhibited the growth of D. fortii and D. caudata.•High light intensity increased the ...production rates of PTX for all isolates.•The impact of light on DST production rates was species and strain-specific.
This study aimed to explore the effects of different light intensities on the ecophysiology of eight new Dinophysis isolates comprising four species (D. acuminata, D. ovum, D. fortii, and D. caudata) collected from different geographical regions in the US. After six months of acclimation, the growth rates, photosynthetic efficiency (Fv/Fm ratio), toxin content, and net toxin production rates of the Dinophysis strains were examined. The growth rates of D. acuminata and D. ovum isolates were comparable across light intensities, with the exception of one D. acuminata strain (DANY1) that was unable to grow at the lowest light intensity. However, D. fortii and D. caudata strains were photoinhibited and grew at a slower rate at the highest light intensity, indicating a lower degree of adaptability and tolerance to such conditions. Photosynthetic efficiency was similar for all Dinophysis isolates and negatively correlated with exposure to high light intensities. Multiple toxin metrics, including cellular toxin content and net production rates of DSTs and PTXs, were variable among species and even among isolates of the same species in response to light intensity. A pattern was detected, however, whereby the net production rates of PTXs were significantly lower across all Dinophysis isolates when exposed to the lowest light intensity. These findings provide a basis for understanding the effects of light intensity on the eco-physiological characteristics of Dinophysis species in the US and could be employed to develop integrated physical-biological models for species and strains of interest to predict their population dynamics and mitigate their negative effects.
Alpine soils are warming strongly, leading to profound alterations in carbon cycling and greenhouse gas budgets, mediated via the soil microbiome. To explore microbial responses to global warming, we ...incubated eight alpine soils between 4 and 35 °C and linked the temperature dependency of bacterial growth with alterations in community structures and the identification of temperature sensitive taxa. The temperature optimum for bacterial growth was between 27 and 30 °C and was higher in soils from warmer environments. This temperature framing the upper limit of naturally occurring temperatures was a tipping point above which the temperature range for growth shifted towards higher temperatures together with pronounced changes in community structures and diversity based on both 16S rRNA gene and transcript sequencing. For instance, at the highest temperature, we observed a strong increase in OTUs affiliated with Burkholderia-Paraburkholderia, Phenylobacterium, Pseudolabrys, Edaphobacter and Sphingomonas. Dominance at high temperature was explained by a priori adaptation to high temperature, high growth potential as well as stress resistance. At the highest temperature, we moreover observed an overall increase in copiotrophic properties in the community along with high growth rates. Further, temperature effects on community structures depended on the long-term climatic legacy of the soils. These findings contribute to extrapolating from single to multiple sites across a large range of conditions.
•Temperature impacts on alpine soil microbiome depend on climatic legacy of the soil.•Strong temperature effects above community optimum for growth, minor effects below.•High bacterial growth rates and copiotrophic features at high temperature.•High temperature promotes heat-adapted, stress resistant and fast growing bacteria.•Burkholderia, Phenylobacterium, Pseudolabrys and Edaphobacter favored by heat.
Do corals form their skeletons by precipitation from solution or by attachment of amorphous precursor particles as observed in other minerals and biominerals? The classical model assumes ...precipitation in contrast with observed “vital effects,” that is, deviations from elemental and isotopic compositions at thermodynamic equilibrium. Here, we show direct spectromicroscopy evidence in Stylophora pistillata corals that two amorphous precursors exist, one hydrated and one anhydrous amorphous calcium carbonate (ACC); that these are formed in the tissue as 400-nm particles; and that they attach to the surface of coral skeletons, remain amorphous for hours, and finally, crystallize into aragonite (CaCO₃). We show in both coral and synthetic aragonite spherulites that crystal growth by attachment of ACC particles is more than 100 times faster than ion-by-ion growth from solution. Fast growth provides a distinct physiological advantage to corals in the rigors of the reef, a crowded and fiercely competitive ecosystem. Corals are affected by warming-induced bleaching and postmortem dissolution, but the finding here that ACC particles are formed inside tissue may make coral skeleton formation less susceptible to ocean acidification than previously assumed. If this is how other corals form their skeletons, perhaps this is how a few corals survived past CO₂ increases, such as the Paleocene–Eocene Thermal Maximum that occurred 56 Mya.
Phosphorus and nitrogen are essential components of microalgal growth media. Critical to a wide range of biochemical processes, they commonly limit primary productivity. Recycling elemental ...phosphorus and fixed nitrogen after fuel conversion via hydrothermal liquefaction (HTL) of algae biomass reduces the need for mined phosphorus and synthetic nitrogen resources. Scenedesmus obliquus DOE 0152.Z and Chlorella sorokiniana DOE1412 were used as test organisms in assessing nutrient recycle of phosphorus from filtered solids collected downstream of the HTL reactor and nitrogen collected from the aqueous phase after gravimetric biocrude separation. Maximum specific growth rates were measured in growth media using HTL waste as the sole source of either phosphorus or nitrogen and were compared to an algal growth medium control (BG-11). The maximum specific growth rate of both organisms in the recycled phosphorus medium were nearly identical to rates observed in the control medium. Both organisms showed significantly reduced growth rates in the recycled nitrogen medium. C. sorokiniana DOE1412 adapted after several days of exposure whereas S. obliquus DOE0152.Z exhibited poor adaptability to the recycled nitrogen medium. After adaptation, growth rates observed with C. sorokiniana DOE1412 in the recycled nitrogen medium were 3.02 (±0.13) day−1, 89% of the control medium (3.40±0.21). We further tested maximum specific growth rates of C. sorokiniana DOE1412 in a medium derived entirely from HTL byproducts, completely replacing all components including nitrogen and phosphorus. In this medium we observed rates of 2.70±0.05day−1, 79% of the control. Adding trace metals to this recycled medium improved growth rates significantly to 3.10±0.10, 91% of the control, indicating a critical element is lost in the conversion process. Recycling elemental resources such as phosphorus and nitrogen from the HTL biofuel conversion process can provide a significant reduction in media cost and improves the prospects for industrial scale, algae-based biofuels.
•Nutrient recycle is critical for the sustainable mass production of biofuels from algae•Nitrogen and phosphorus recycled from hydrothermal liquefaction waste products were used to replace chemical salts in a standard medium used for cultivating microalgae•Recycled phosphorus showed no reductions in maximum specific growth rates for both organisms tested.•Recycled nitrogen was inhibitory to one of the two organisms tested•A completely recycled medium was found to support maximum specific growth rates of 2.7 day-1 and final biomass yields of 2.9 g/L ash-free dry weight.
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