Maximum Net Growth Research Articles

Synthesis of Lactic Acid from Molasses by Lactobacillus acidophilus Using a Batch Fermentation Process

Lactic acid is a chemical with widespread applications, mainly in pharmaceutical, cosmetic, chemical as well as food industries. One of the major uses of lactic acid is the polylactic acid (PLA) feedstock which is biodegradable and biocompatible as an alternative to plastic derived from fossil fuels. Efforts continue to be made to reduce the cost of producing PLA in order to compete with the conventional petrochemical-based plastics. This include the use of molasses as a raw material because it is cheap and contains high glucose. The purpose of this study was to obtain cell concentrations through the addition of starter volume that produces high concentrations of lactic acid and to obtain the growth kinetics of Lactobacillus acidophilus during the fermentation process. This study was conducted in several stages; the design of bioreactors, inoculation of Lactobacillus acidophilus, and fermentation of molasses. In a batch system, molasses substrate was directly inserted as much as 500 ml in the fermentor and the addition of starter volume of Lactobacillus acidophilus was 1; 3; 5 dan 10% v/v. The fermentation of molasses for 72 hours and the product was analysed every 8 hours. The highest concentration of lactic acid produced in batch fermented molasses was added to 5% (v/v) starter volume with 72 hours of fermentation time, which was 23.1 mg/L, with value the carrying-capacity coefficient (k) and the maximum net specific growth rate (µnet) were 0.2379 h-1 and 0.0160 h-1 respectively.

Chemical Characteristics and Sources of Volatile Organic Compounds in Shanghai During an Ozone and Particulate Pollution Episode in May 2019

In the urban area of Shanghai during the complex pollution episode, ozone and PM2.5 were continuously measured from May 1 to May 28, 2019. The characterization of volatile organic compounds (VOCs) and their relationship with secondary formation were studied. The results show that in May 2019, there were four different ozone and PM2.5 pollution processes in Shanghai. The combined pollution of PM2.5 and ozone that occurred under the meteorological conditions of average temperature of approximately 26℃ and relative humidity of approximately 40% was analyzed. The photochemical consumption of VOCs was significantly positively correlated with the maximum net growth of O3 and there was a significant positive correlation between SOAP and PM2.5. The key reactive species of VOCs that significantly contribute to ozone generation were m,p-xylene, ethylene, toluene, propylene, and o-xylene. The key reactive species that significantly contribute to secondary organic aerosols (SOA) were toluene, m,p-xylene, ethylbenzene, o-xylene, and 1,2,3-trimethylbenzene.

Growth rates of Gracilariopsis longissima, Gracilaria bursa-pastoris and Chondracanthus teedei (Rhodophyta) cultured in ropes: implication for N biomitigation in Cadiz Bay (Southern Spain)

Cultures of three native macroalgal species (Gracilariopsis longissima, Gracilaria bursa-pastoris and Chondracanthus teedei) were developed in open coastal waters of a shallow, potentially eutrophic bay in Southern Spain. Experimental trials to assess the technical feasibility of seaweed cultivation and nitrogen biofiltration potential were conducted between October 2014 and December 2015. Seaweeds were cultivated using submersible rafts in five periods of 9 weeks to identify the most suitable seasons and culture duration (3, 6 or 9 weeks). Using generalized linear models (GLMs), the most relevant environmental factors controlling the growth of the three seaweeds were identified. Maximum net growth rates varied between 1.39% day−1 in C. teedei (winter, 6 weeks) and 4.71% day−1 in G. longissima (autumn, 3 weeks). Overall, the best period to cultivate seaweeds in Cadiz Bay was from mid-winter to early summer. No clear effects of duration of the culture were observed for C. teedei and G. bursa-pastoris. Short culture periods of 3 weeks were more suitable for G. longissima. Tissue N contents generally were lower than the critical quota, and GLMs suggested a critical role of N limiting seaweed growth in this bay. Dissolved inorganic nitrogen was biofiltered from winter to early summer and revealed G. bursa-pastoris as the main biomitigator of nitrogen (up to 80 mg N m−1 month−1 in spring). This species also showed positive growth rates virtually during the entire study period and was the most suitable species for cultivation in this area.

Constant Flux of Spatial Niche Partitioning through High-Resolution Sampling of Magnetotactic Bacteria.

Magnetotactic bacteria (MTB) swim along magnetic field lines in water. They are found in aquatic habitats throughout the world, yet knowledge of their spatial and temporal distribution remains limited. To help remedy this, we took MTB-bearing sediment from a natural pond, mixed the thoroughly homogenized sediment into two replicate aquaria, and then counted three dominant MTB morphotypes (coccus, spirillum, and rod-shaped MTB cells) at a high spatiotemporal sampling resolution: 36 discrete points in replicate aquaria were sampled every ∼30 days over 198 days. Population centers of the MTB coccus and MTB spirillum morphotypes moved in continual flux, yet they consistently inhabited separate locations, displaying significant anticorrelation. Rod-shaped MTB were initially concentrated toward the northern end of the aquaria, but at the end of the experiment, they were most densely populated toward the south. The finding that the total number of MTB cells increased over time during the experiment argues that population reorganization arose from relative changes in cell division and death and not from migration. The maximum net growth rates were 10, 3, and 1 doublings day-1 and average net growth rates were 0.24, 0.11, and 0.02 doublings day-1 for MTB cocci, MTB spirilla, and rod-shaped MTB, respectively; minimum growth rates for all three morphotypes were -0.03 doublings day-1 Our results suggest that MTB cocci and MTB spirilla occupy distinctly different niches: their horizontal positioning in sediment is anticorrelated and under constant flux.IMPORTANCE Little is known about the horizontal distribution of magnetotactic bacteria in sediment or how the distribution changes over time. We therefore measured three dominant magnetotactic bacterium morphotypes at 36 places in two replicate aquaria each month for 7 months. We found that the spatial positioning of population centers changed over time and that the two most abundant morphotypes (MTB cocci and MTB spirilla) occupied distinctly different niches in the aquaria. Maximum and average growth and death rates were quantified for each of the three morphotypes based on 72 sites that were measured six times. The findings provided novel insight into the differential behavior of noncultured magnetotactic bacteria.

Phytoplankton traits from long-term oceanographic time-series

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 576:11-25 (2017) - DOI: https://doi.org/10.3354/meps12220 Phytoplankton traits from long-term oceanographic time-series Crispin M. Mutshinda1, Zoe V. Finkel2, Claire E. Widdicombe3, Andrew J. Irwin1,* 1Mathematics & Computer Science, Mount Allison University, Sackville, NB E4L 1E6, Canada 2Environmental Science, Mount Allison University, Sackville, NB E4L 1A7, Canada 3Plymouth Marine Laboratory, Prospect Place, Plymouth PL1 3DH, UK *Corresponding author: airwin@mta.ca ABSTRACT: Trait values are usually extracted from laboratory studies of single phytoplankton species, which presents challenges for understanding the immense diversity of phytoplankton species and the wide range of dynamic ocean environments. Here we use a Bayesian approach and a trait-based model to extract trait values for 4 functional types and 10 diatom species from field data collected at Station L4 in the Western Channel Observatory, English Channel. We find differences in maximum net growth rate, temperature optimum and sensitivity, half-saturation constants for light and nitrogen, and density-dependent loss terms across the functional types. We find evidence of very high linear loss rates, suggesting that grazing may be even more important than commonly assumed and differences in density-dependent loss rates across functional types, indicating the presence of strong niche differentiation among functional types. Low half-saturation constants for nitrogen at the functional type level may indicate widespread mixotrophy. At the species level, we find a wide range of density-dependent effects, which may be a signal of diversity in grazing susceptibility or biotic interactions. This approach may be a way to obtain more realistic and better-constrained trait values for functional types to be used in ecosystem modeling. KEY WORDS: Phytoplankton · Time series · Traits · Growth rate · Grazing rate · English Channel Full text in pdf format Supplementary material PreviousNextCite this article as: Mutshinda CM, Finkel ZV, Widdicombe CE, Irwin AJ (2017) Phytoplankton traits from long-term oceanographic time-series. Mar Ecol Prog Ser 576:11-25. https://doi.org/10.3354/meps12220 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 576. Online publication date: August 03, 2017 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2017 Inter-Research.

Nonlinear Relationship of Near-Bed Velocity and Growth of Riverbed Periphyton

Artificial streams were set up to test the relationship between near-bed water velocity and periphyton growth. Periphyton community samples collected from a Japanese stream were incubated for 44 days under a light intensity of 252 ± 72 μmol·photons/m2·s, a temperature of 20–25 °C, and three near-bed water velocity classes: low (<17.9 cm/s), moderate (17.9–32.8 cm/s), and high (>32.8 cm/s). A logistic model was applied to estimate the maximum net growth rate (μmax) and carrying capacity (Bmax). A response surface method was also applied to estimate chlorophyll a (Chl-a) and ash-free dry mass (AFDM) with respect to the independent variables (i.e., time and water velocity). We detected both the highest μmax (1.99 d−1) and highest Bmax (7.01 mg/m2) for Chl-a at the moderate water velocity. For AFDM, we observed the highest μmax (0.57 d−1) and Bmax (1.47 g/m2) at the low and moderate velocity classes, respectively. The total algae density in the region of moderate velocity at the end of the experiment was 6.47 × 103 cells/cm2, corresponding to levels 1.7 and 1.3 times higher than those at lower and higher velocities, respectively. Our findings indicated that the moderate near-bed water velocity provided favorable conditions for algal growth and corresponding biomass accumulation.

Diazotroph community succession during the VAHINE mesocosm experiment (New Caledonia lagoon)

Abstract. The VAHINE mesocosm experiment, conducted in the low-nutrient low-chlorophyll waters of the Noumea lagoon (coastal New Caledonia) was designed to trace the incorporation of nitrogen (N) fixed by diazotrophs into the food web, using large volume (50 m3) mesocosms. This experiment provided a unique opportunity to study the succession of different N2-fixing microorganisms (diazotrophs) and calculate in situ net growth and mortality rates in response to fertilization with dissolved inorganic phosphate (DIP) over a 23-day period, using quantitative polymerase chain reaction (qPCR) assays targeting widely distributed marine diazotroph lineages. Inside the mesocosms, the most abundant diazotroph was the heterocyst-forming Richelia associated with Rhizosolenia (Het-1) in the first half of the experiment, while unicellular cyanobacterial Group C (UCYN-C) became abundant during the second half of the experiment. Decreasing DIP concentrations following the fertilization event and increasing temperatures were significantly correlated with increasing abundances of UCYN-C. Maximum net growth rates for UCYN-C were calculated to range between 1.23 ± 0.07 and 2.16 ± 0.07 d−1 in the mesocosms, which are among the highest growth rates reported for diazotrophs. Outside the mesocosms in the New Caledonia lagoon, UCYN-C abundances remained low, despite increasing temperatures, suggesting that the microbial community response to the DIP fertilization created conditions favorable for UCYN-C growth inside the mesocosms. Diazotroph community composition analysis using PCR targeting a component of the nitrogenase gene (nifH) verified that diazotrophs targeted in qPCR assays were collectively among the major lineages in the lagoon and mesocosm samples, with the exception of Crocosphaera-like phylotypes, where sequence types not typically seen in the oligotrophic ocean grew in the mesocosms. Maximum net growth and mortality rates for nine diazotroph phylotypes throughout the 23-day experiment were variable between mesocosms, and repeated fluctuations between periods of net growth and mortality were commonly observed. The field population of diazotrophs in the New Caledonian lagoon waters appeared to be dominated by Het-1 over the course of the study period. However, results from both qPCR and PCR analysis indicated a diverse field population of diazotrophs was present in the lagoon at the time of sampling. Two ecotypes of the Braarudosphaera bigelowii symbiont unicellular group A (UCYN-A) were present simultaneously in the lagoon, with the recently described B. bigelowii/UCYN-A2 association present at higher abundances than the B. bigelowii/UCYN-A1 association.

Pharmacodynamic modelling of in vitro activity of tetracycline against a representative, naturally occurring population of porcine Escherichia coli.

BackgroundThe complex relationship between drug concentrations and bacterial growth rates require not only the minimum inhibitory concentration but also other parameters to capture the dynamic nature of the relationship. To analyse this relationship between tetracycline concentration and growth of Escherichia coli representative of those found in the Danish pig population, we compared the growth of 50 randomly selected strains. The observed net growth rates were used to describe the in vitro pharmacodynamic relationship between drug concentration and net growth rate based on Emax model with three parameters: maximum net growth rate (αmax); concentration for a half-maximal response (Emax); and the Hill coefficient (γ).ResultsThe net growth rate in the absence of antibiotic did not differ between susceptible and resistant isolates (P = 0.97). The net growth rate decreased with increasing tetracycline concentrations, and this decline was greater in susceptible strains than resistant strains. The lag phase, defined as the time needed for the strain to reach an OD600 value of 0.01, increased exponentially with increasing tetracycline concentration. The pharmacodynamic parameters confirmed that the alpha_{max} between susceptible and resistant strains in the absence of a drug was not different. EC50 increased linearly with MIC on a log–log scale, and γ was different between susceptible and resistant strains.ConclusionsThe in vitro model parameters described the inhibition effect of tetracycline on E. coli when strains were exposed to a wide range of tetracycline concentrations. These parameters, along with in vivo pharmacokinetic data, may be useful in mathematical models to predict in vivo competitive growth of many different strains and for development of optimal dosing regimens for preventing selection of resistance.

Optimal defense strategies in an idealized microbial food web under trade-off between competition and defense.

Trophic mechanisms that can generate biodiversity in food webs include bottom-up (growth rate regulating) and top-down (biomass regulating) factors. The top-down control has traditionally been analyzed using the concepts of “Keystone Predation” (KP) and “Killing-the-Winner” (KtW), predominately occuring in discussions of macro- and micro-biological ecology, respectively. Here we combine the classical diamond-shaped food web structure frequently discussed in KP analyses and the KtW concept by introducing a defense strategist capable of partial defense. A formalized description of a trade-off between the defense-strategist's competitive and defensive ability is included. The analysis reveals a complex topology of the steady state solution with strong relationships between food web structure and the combination of trade-off, defense strategy and the system's nutrient content. Among the results is a difference in defense strategies corresponding to maximum biomass, production, or net growth rate of invading individuals. The analysis thus summons awareness that biomass or production, parameters typically measured in field studies to infer success of particular biota, are not directly acted upon by natural selection. Under coexistence with a competition specialist, a balance of competitive and defensive ability of the defense strategist was found to be evolutionarily stable, whereas stronger defense was optimal under increased nutrient levels in the absence of the pure competition specialist. The findings of success of different defense strategies are discussed with respect to SAR11, a highly successful bacterial clade in the pelagic ocean.

Effect of organic carbon, C:N ratio and light on the growth and lipid productivity of microalgae/cyanobacteria coculture

Current culture methods based on monocultures under phototrophic regimes are prone to contamination, predation, and collapse. Native cultures of multiple species are adapted to the local conditions and are more robust against contamination and predation. Growth, lipid and biomass productivity of a Louisiana native coculture of microalgae (Chlorella vulgaris) and cyanobacteria (Leptolyngbya sp.) in heterotrophic and mixotrophic regimes were investigated. Dextrose and sodium acetate at C:N ratios of 15:1 and 30:1 under heterotrophic (dark) and mixotrophic (400 μmol m−2 s−1) regimes were compared with autotrophic controls. The carbon source and C:N ratio impacted growth and biomass productivity. Mixotrophic cultures with sodium acetate (C:N 15:1) resulted in the highest mean biomass productivity (156 g m−3 d−1) and neutral lipid productivity (24.07 g m−3 d−1). The maximum net specific growth rate (U) was higher (0.97 d−1) in mixotrophic cultures with dextrose (C:N 15:1) but could not be sustained resulting in lower total biomass than in mixotrophic cultures with acetate (C:N 15:1), with a U of 0.67 d−1. The ability of the Louisiana coculture to use organic carbon for biomass and lipid production makes it a viable feedstock for biofuels and bioproducts.

Modeling the effects of abiotic and biotic factors on the depth distribution of Fucus vesiculosus in the Baltic Sea

The conspicuous retreat of the key species Fucus vesiculosus from the deeper parts of its former distribution area in the Baltic Sea has triggered extensive research on the factors that control its growth. Based on recently obtained knowledge on a large number of potential drivers, we developed a numerical model incorporating effects of abiotic factors on the physiological functions of photosynthesis, respiration, and reproduction and the ecological processes of competition, grazing, and epibiosis. For all input combinations, the model delivers the monthly net growth rate near the bladder wrack’s depth limit and the maximum depth of its vertical distribution. The use of data corresponding to conditions presently observed in the western Baltic Sea sets the year’s maximum algal net growth rate in late spring and 2 minima in early spring and autumn. The depth limit of the wrack’s distribution is set at ~9 m. Light and its absorption by phytoplankton represent by far the most important factors controlling the modeled net growth rate and depth penetration, with the role of epibiosis requiring further investigation. Lacking findings on population dynamics and biotic interactions restrict the generated model to an exploratory rather than a predictive tool.

Analogous nutrient limitations in unicellular diazotrophs and Prochlorococcus in the South Pacific Ocean

Growth limitation of phytoplankton and unicellular nitrogen (N(2)) fixers (diazotrophs) were investigated in the oligotrophic Western South Pacific Ocean. Based on change in abundances of nifH or 23S rRNA gene copies during nutrient-enrichment experiments, the factors limiting net growth of the unicellular diazotrophs UCYN-A (Group A), Crocosphaera watsonii, γ-Proteobacterium 24774A11, and the non-diazotrophic picocyanobacterium Prochlorococcus, varied within the region. At the westernmost stations, numbers were enhanced by organic carbon added as simple sugars, a combination of iron and an organic chelator, or iron added with phosphate. At stations nearest the equator, the nutrient-limiting growth was not apparent. Maximum net growth rates for UCYN-A, C. watsonii and γ-24774A11 were 0.19, 0.61 and 0.52 d(-1), respectively, which are the first known empirical growth rates reported for the uncultivated UCYN-A and the γ-24774A11. The addition of N enhanced total phytoplankton biomass up to 5-fold, and the non-N(2)-fixing Synechococcus was among the groups that responded favorably to N addition. Nitrogen was the major nutrient-limiting phytoplankton biomass in the Western South Pacific Ocean, while availability of organic carbon or iron and organic chelator appear to limit abundances of unicellular diazotrophs. Lack of phytoplankton response to nutrient additions in the Pacific warm pool waters suggests diazotroph growth in this area is controlled by different factors than in the higher latitudes, which may partially explain previously observed variability in community composition in the region.

An Individual-based Population Model for Rotifer (Brachionus plicatilis) Cultures

An individual-based dynamic energy budget model is used in a Lagrangian simulation to compute population dynamics for the rotifer strain Brachionus plicatilis. This model structure allows description of transient as well as stationary conditions, making the model useful for a variety of applications. It also has the advantage of allowing the use of dynamic energy budged (DEB) theory in describing rotifer energetics. The model is developed with aquaculture-related applications in mind, including planning, monitoring and control of rotifer production systems and first feeding of marine fish larvae. Simulations show acceptable agreement with measured data on the population level, with regard to steady-state egg ratio, yields of daily diluted cultures, and maximum net growth rate. Further refinement of the model can enable its application for processes such as essential nutrient enrichment of rotifers for first feeding of larval fish.

GETTING TO THE CANOPY: TREE HEIGHT GROWTH IN A NEOTROPICAL RAIN FOREST

There is still limited understanding of the processes underlying forest dy- namics in the world's tropical rain forests, ecosystems of disproportionate importance in terms of global biogeochemistry and biodiversity. Particularly poorly documented are the nature and time scale of upward height growth during regeneration by the tree species in these communities. In this study, we assessed long-term height growth through ontogeny for a diverse group of canopy and emergent tree species in a lowland neotropical rain forest (the La Selva Biological Station, northeastern Costa Rica). Species were evaluated based on annual height measurements of large samples of individuals in all postseedling size classes, over a 16-yr period ( .11 000 increments). The study species were seven nonpi- oneers (Minquartia guianensis, Lecythis ampla, Hymenolobium mesoamericanum, Sima- rouba amara, Dipteryx panamensis, Balizia elegans,and Hyeronima alchorneoides ) and two pioneers (Cecropia obtusifoliaand Cecropia insignis). For each species, inherent height growth capacity was estimated as the mean of the five largest annual height increments (from different individuals) in each juvenile size class (from 50 cm tall to 20 cm in diameter). All species showed marked ontogenetic increases in this measure of height growth potential. At all sizes, there were highly significant differences among species in height growth potential. The two Cecropia species consistently showed the highest observed maximum height increments as smaller juveniles (#4 cm in diameter). Among the nonpioneers, Sim- arouba had the highest growth potential across all juvenile sizes. For all species, mean annual height increments in all juvenile size classes were very much lower than the species' potential growth rates and reflected the impacts of frequent periods of zero growth and major height losses from physical damage. Because of the same factors, maximum net height increments declined over increasing measurement intervals (1-15-yr periods). With only one exception (Simarouba amara saplings #1 cm in diameter that survived 10 yr), the annual height growth increments of these species showed no significant temporal au- tocorrelation. For the seven nonpioneer species, we estimated the minimum time required to grow from 50 cm tall saplings to 10 cm diameter trees, based on their greatest net height increments over increasing intervals. Estimated passage times increased from 7-33 yr, when based on maximum 5-yr height increments, to 37-83 yr, when based on maximum net height growth over 15 yr for the six longest studied (nonpioneer) species. Given the erratic height growth trajectories found for these juvenile trees in this 16-yr study, it is clear that much longer term observation is required. Still unknown are the actual growth trajectories that characterize successful regeneration in each of our focal species, how much time successful trees spend as suppressed juveniles, and the number of times they experience and recover from major physical damage.

Comparison of the scope for growth with the growth performance of Ostrea edulis seed reared at different food concentrations in an open-flow system

Oyster (Ostrea edulis L.) seed was reared on five rations of Isochrysis galbana Parke: 10, 30, 100, 200 and 300 cells μl-1, in an open-flow system. Physiological parameters such as clearance, ingestion, absorption and respiration rates were measured, and the scope for growth (SFG) calculated from these parameters was compared with actual growth over 20 d. Actual growth was negligible at 10 cells μl-1 (daily maintenance ration=2.5% organic wt) and maximum (growth rate=13.64 d-1) at 200 cells μl-1 (daily ration=43% organic wt), which also supported the maximum gross and net growth efficiencies (K1=50%, K2=85%). Ingestion rate was directly correlated to cell concentration up to maximum of ∼100 cells μl-1, but further increases failed to support higher ingestions. Absorption efficiency decreased with increasing algal concentration from 95% down to 60%. Due to the costs of growth, respiration rate significantly increased when food was added above maintenance levels; however, metabolic costs associated with feeding activity were undetectable. The scope for growth calculated from these physiological parameters agreed with the long-term growth performance, validating the physiological energetics method as a valuable tool for predicting long-term growth performance under constant environmental conditions.

Listeria monocytogenes Inhibition in Refrigerated Vacuum Packaged Turkey Bologna by Chemical Additives

ABSTRACTSliced cooked turkey bologna with various additive formulations was surface‐inoculated with Listeria monocytogenes (2.06–2.75 log CFU/g), vacuum packaged, and stored at 4°C. Sodium acetate was most inhibitory against growth of L. monocytogenes, followed by sodium lactate and potassium sorbate, while sodium bicarbonate allowed a maximum net growth of 6.78 log CFU/g, not significantly different (p>0.05) from the control (6.43 log CFU/g). Addition of 0.5% sodium acetate, 2.0% sodium lactate, or 0.26% potassium sorbate may significantly (p<0.05) decrease growth of L. monocytogenes in refrigerated turkey bologna surface‐inoculated after thermal processing and slicing.

The effect of gravitational compaction on estimation of vertical salt structure growth

The growth history of salt structures is reflected in the variation of the present thickness of the overlying and surrounding sediments in relation to the regional normal. A method for estimating the growth history of salt structures in the pillow and post-diapiric phase, including the effect of differential syn- and post-depositional compaction, is described. The assumption that stratigraphic thinning and established structural relief is a result of vertical salt movement alone is inadequate. A quantification of the true vertical movement of the salt crest necessitates a correction for compaction and differential basement subsidence. The on-structure thickness is compared to the regional normal for the time-stratigraphic interval under consideration. On the basis of the dominant porosity-reducing process, the minimum and maximum net growth can be calculated. The true net growth is assumed to be contained within these limits, probably closest to the minimum net growth. Two shallow salt diapirs in the Danish Basin exemplify the relationship between the observed stratigraphic thinning and structural relief and the differential compaction, differential basement subsidence, and vertical growth of the salt surface. The average minimum and maximum net growth of the salt surface at the Batum and Mors salt diapirs in the post-diapiric phase are calculated. The minimum and maximum net growth values for the Batum salt diapir are 731 m and 1303 m respectively, and for the Mors salt diapir 276 m and 996 m respectively, thus emphasizing the importance of including the effect of compaction in the calculations of salt structure net growth. The implications for storage of hydrocarbons, radioactive and chemical wastes, as well as for petroleum exploration, are emphasized.

The effect of ration and temperature on the growth of the three‐spined stickleback, Gasterosteus aculeatus L.

The effect of ration on the growth of the three‐spined stickleback, Gasterosteus aculeatus, was studied over the temperature range 3·19°C, which corresponded to the range in their natural habitat. With an ad lib ration, the specific growth rate increased with temperature. The relationship between specific growth rate and ration at a given temperature was curvilinear. Regression models were used to predict the maximum, optimum and maintenance rations at each temperature. Whereas maximum ration increased rapidly with temperature, the optimum and maintenance rations were relatively insensitive to temperature. A regression model was used to describe the overall relationship between specific growth rate and ration, temperature and body weight. This model predicted that at low rations, growth rate decreased with temperature, whereas at high rations, growth rate increased slightly with temperature. The gross growth efficiency increased rapidly with rations above maintenance ration up to a maximum at the optimum ration and declined at higher rations. The maximum gross growth efficiencies were at high temperatures and rations about half of the maximum ration. The maximum net growth efficiencies occurred at relatively low temperature and at rations just above maintenance.

Soil testing of horticultural substrates (v) Evaluation of 1: 1.5 water extract and ammonium acetate extract for potassium and desirable potassium values

Abstract The 1: 1.5 water extraction of horticultural substrate for K was evaluated using K uptake as the criterion. Two crops, chrysanthemum (2 trials) and verbena (2 trials) were grown in peat, peat + pumice (PP), pine bark and peat + sawdust + sand (PSS). The ammonium acetate (NH4OAc) extraction for K was evaluated in one trial. The number of K application rates varied from 9 to 23. The relationship between both soil tests and plant uptake was very good for all substrates, although it was generally poorer in bark, particularly in the verbena trials. This was probably due to the relatively high level of native K in bark and the lower K requirement of verbena. The relationship between water extractable K and NH4OAc extractable K was linear and very good. Percentage maximum dry weight and net growth rate were regressed against soil test values using a quadratic function and desirable values (DV) were estimated from the response curve. The initial DV for water extractable K For maximum dry weight in the chrysanthemum trials varied from about 45 ‐ 139 ppm and for NH4OAc extractable K in one chrysanthemum trial varied from 284 ‐ 469 ppm. The DV obtained from growth rate measurements were similar to those obtained using percent maximum dry weight. It was not possible to determine DV for plants growing in bark and in PSS in one trial. The DV for verbena, which could be determined in peat in only one trial due to lack of response in the others was 10–11 ppm in the water extract.

Energy Dynamics of the Eutrophic Chironomid Chironomus plumosus f. semireductus from the Bay of Quinte, Lake Ontario

Relationships between feeding rate, temperature, body size, and time of day were investigated and collated with seasonal assimilation efficiencies of in situ chironomids to construct a picture of chironomid energetics over the year. Temperature controlled feeding rate, and larval size and time of day exerted no effect. The temperature optimum plateaued between 22.0 and 24.5 °C, decreasing logarithmically outside this range. Both assimilation efficiency (AE) and organic content of the food varied seasonally, but were not correlated. Periods of high AE corresponded with the latter part of Melosira or Melosira–Stephanodiscus blooms, while periods of low AE occurred between diatom blooms and during the late summer blue-green bloom. Consequently, growth fluctuated throughout the year, being a result of the interaction of temperature and AE. Anabolic processes dominated at AE greater than 3.5%. Maximum net growth efficiency (NGE) was attained when AE ≥ 6% and temperature ≥ 15 °C. NGE was more sensitive to changes in AE than temperature. Instantaneous growth rate, however, was more sensitive to changes in temperature. Daily ingestion (mg) exceeded body weight by as much as 460–480%, which equals the sediment-processing capacity of freshwater detritivores.Key words: chironomid, feeding rate, assimilation efficiency, instantaneous growth rate, net growth efficiency, algal community, Bay of Quinte