Biomass Transfer Research Articles

Plankton based energy transfer rates in four Cuban coastal lagoons

Biomass transfer rates between successive trophic levels in plankton based food chains frequently produce inverted pyramids but when productivity data are used instead, such a methodologically caused thermodynamic impossibility is eliminated. A study of plankton based energy transfer rates in 4 Cuban coastal lagoons, including each ecosystem major component biomass, age, productivity, and energy contents values, is presented to illustrate how inverted pyramids are produced, and eliminated.Duplication times and mean ages, variable between lagoons, were 25–77 h for suspended detritus; 48–74 h for phytoplankton, and 60–90 days for zooplankters, 78% of which were copepods. For intertidal sessile filter feeders attached to the red mangrove aerial roots average ages were 0.8–2.5 months for barnacles; 1.1–2.3 months for scorched mussel; 2.9–3.5 months for flat tree-oyster; 4.5–4.8 months for mangrove oyster, and 6.1 months average for soft bodied epibionts such as tunicates and sponges.The average biomass transfer rate for the 4 lagoons from phytoplankton to zooplankton was 141%, and from detritus plus phytoplankton to sessile filter feeders was 423% both reduced to 5% and 8%, respectively, when productivity values were used, demonstrating that biomass transfer rates are intrinsically incorrect, and misleading, and that only productivity values, preferably in energy units, should be considered in trophic ecology studies.

Unexpected changes in community size structure in a natural warming experiment

A warmer climate is generally expected to favour smaller organisms and steeper body-mass–abundance scaling through food webs. Results from across a stream temperature gradient now show that this effect can be offset by increasing nutrient supply. Natural ecosystems typically consist of many small and few large organisms1,2,3,4. The scaling of this negative relationship between body mass and abundance has important implications for resource partitioning and energy usage5,6,7. Global warming over the next century is predicted to favour smaller organisms8,9,10,11,12, producing steeper mass–abundance scaling13 and a less efficient transfer of biomass through the food web5. Here, we show that the opposite effect occurs in a natural warming experiment involving 13 whole-stream ecosystems within the same catchment, which span a temperature gradient of 5–25 °C. We introduce a mechanistic model that shows how the temperature dependence of basal resource carrying capacity can account for these previously unexpected results. If nutrient supply increases with temperature to offset the rising metabolic demand of primary producers, there will be sufficient resources to sustain larger consumers at higher trophic levels. These new data and the model that explains them highlight important exceptions to some commonly assumed ‘rules’ about responses to warming in natural ecosystems.

Global change in the trophic functioning of marine food webs.

The development of fisheries in the oceans, and other human drivers such as climate warming, have led to changes in species abundance, assemblages, trophic interactions, and ultimately in the functioning of marine food webs. Here, using a trophodynamic approach and global databases of catches and life history traits of marine species, we tested the hypothesis that anthropogenic ecological impacts may have led to changes in the global parameters defining the transfers of biomass within the food web. First, we developed two indicators to assess such changes: the Time Cumulated Indicator (TCI) measuring the residence time of biomass within the food web, and the Efficiency Cumulated Indicator (ECI) quantifying the fraction of secondary production reaching the top of the trophic chain. Then, we assessed, at the large marine ecosystem scale, the worldwide change of these two indicators over the 1950–2010 time-periods. Global trends were identified and cluster analyses were used to characterize the variability of trends between ecosystems. Results showed that the most common pattern over the study period is a global decrease in TCI, while the ECI indicator tends to increase. Thus, changes in species assemblages would induce faster and apparently more efficient biomass transfers in marine food webs. Results also suggested that the main driver of change over that period had been the large increase in fishing pressure. The largest changes occurred in ecosystems where ‘fishing down the marine food web’ are most intensive.

Decomposition and Nitrogen Release Patterns of Parkiabiglobosa and Albizialebbeck Leaves with Nitrogen Fertilizer for Maize Production in Sudan Savanna Alfisolof Nigeria

Biomass transfer or cultivation of leguminous trees has higher eco-friendly profiles for soil nutrients restoration especially nitrogen. The research is conducted on decomposition and nitrogen release patterns of Parkia biglobosa and Albizia lebbeck leaves with nitrogen fertilizer for maize production in sudan savannah alfisol of Nigeria. Data were analysed using (ANOVA). 56 % of N in the litter bag was released the first two weeks of biomass incubation and progressively increases weeks after planting. Decomposition rate constant (KD) ranged from 9.18 to 15.07 week-1 and the rates of plant residues was higher in Albizia lebbeck than Parkia biglobosa in both seasons. Nitrogen release rate constant (KN), ranging from 7.82 to 10.81 week-1 followed a similar pattern as the rate of decomposition with Albizia lebbeck releasing the highest amount of N followed by Parkia lebbeck . The rate of decomposition increased as week increased. Incorporation of Albizia lebbeck had significantly higher effect (p < 0.05) on growth parameter and yield component compared to Parkia biglobosa . The study concluded that Albizia lebbeck decomposed and mineralized faster for crop uptake under sudan savanna conditions. The study suggests that incorporation of Albizia lebbeck and up to 40 kg N ha-1 is a better combination for soil quality improvement and maize productivity in Makera, a semi-arid environment of Nigeria.

Description of the Steady-State Operation of a Biochemical Reactor Using a Diffusion Model

Consideration has been given to nonlinear boundary-value problems of steady-state operation of a biochemical reactor. Nontrivial solutions of these problems have been found using equations of a diffusion model with homogeneous boundary conditions. A study has been made of the operating regimes of the reactor under different conditions of biomass transfer in it.

Integrated trophic position decreases in more diverse communities of stream food webs

The relationship between biodiversity and ecosystem functioning is an important theme in environmental sciences. We propose a new index for configuration of the biomass pyramid in an ecosystem, named integrated trophic position (iTP). The iTP is defined as a sum of trophic positions (i.e. the average number of steps involved in biomass transfer) of all the animals in a food web integrated by their individual biomass. The observed iTP for stream macroinvertebrates ranged from 2.39 to 2.79 and was negatively correlated with the species density and the Shannon–Wiener diversity index of the local community. The results indicate a lower efficiency of biomass transfer in more diverse communities, which may be explained by the variance in edibility hypothesis and/or the trophic omnivory hypothesis. We found a negative effect of biodiversity on ecosystem functioning.

CFD-DEM Numerical Simulation and Experimental Validation of Heat Transfer and Two-Component Flow in Fluidized Bed

Abstract Based on the improved computational fluid dynamics and discrete element method (CFD-DEM), heat transfer and two-component flow of biomass and quartz sand have been studied from experiments and numerical simulation in this paper. During experiments, the particle temperature and moving images are respectively recorded by infrared thermal imager and high speed camera. With the increase of the velocity, the mixing index (MI) and the cooling rate of the particles are rising. Due to larger heat capacity and mass, the temperature of biomass drops slower than that of quartz sand. Fictitious element method is employed to solve the incompatibility of the traditional CFD-DEM where the cylindrical biomass are considered as an aggregation of numerous fictitious sphere particles arranged in certain sequence. By the comparison of data collected by infrared thermal imager and the simulated results, it can be concluded that experimental data is basically agreement with numerical simulation results. Directly affected by inflow air (25℃), the average temperature of particles in the bed height area (h &gt;30 mm) is about 3 degrees lower than that of the other heights. When the superficial gas velocity is larger, the fluidization is good, and the gas temperature distribution is more uniform in the whole area. On the contrary, bubbles are not easy to produce and the fluidization is restricted at lower superficial gas velocity. Gas-solid heat transfer mainly exists under the bed height of 10 mm, and decreases rapidly on fluidized bed height. The mixing index (MI) is employed to quantitatively discuss the mixing effectiveness, which first rises accelerate, then rising speed decreases, finally tends to a upper limit.

Ocean acidification effects on mesozooplankton community development: Results from a long-term mesocosm experiment.

Ocean acidification may affect zooplankton directly by decreasing in pH, as well as indirectly via trophic pathways, where changes in carbon availability or pH effects on primary producers may cascade up the food web thereby altering ecosystem functioning and community composition. Here, we present results from a mesocosm experiment carried out during 113 days in the Gullmar Fjord, Skagerrak coast of Sweden, studying plankton responses to predicted end-of-century pCO2 levels. We did not observe any pCO2 effect on the diversity of the mesozooplankton community, but a positive pCO2 effect on the total mesozooplankton abundance. Furthermore, we observed species-specific sensitivities to pCO2 in the two major groups in this experiment, copepods and hydromedusae. Also stage-specific pCO2 sensitivities were detected in copepods, with copepodites being the most responsive stage. Focusing on the most abundant species, Pseudocalanus acuspes, we observed that copepodites were significantly more abundant in the high-pCO2 treatment during most of the experiment, probably fuelled by phytoplankton community responses to high-pCO2 conditions. Physiological and reproductive output was analysed on P. acuspes females through two additional laboratory experiments, showing no pCO2 effect on females’ condition nor on egg hatching. Overall, our results suggest that the Gullmar Fjord mesozooplankton community structure is not expected to change much under realistic end-of-century OA scenarios as used here. However, the positive pCO2 effect detected on mesozooplankton abundance could potentially affect biomass transfer to higher trophic levels in the future.

Simulation of rapid ecological change in Lake Ontario

Lower trophic level processes are integral to proper functioning of large aquatic ecosystems and have been disturbed in Lake Ontario by various stressors including exotic species. The invasion of benthic habitats by dreissenid mussels has led to systemic changes and native faunal declines. Size-dependent physiological rates, spatial differences and connectivity, competition, and differential population dynamics among invertebrate groups contributed to the change and system complexity. We developed a spatially explicit, individual-based mechanistic model of the benthic ecosystem in Lake Ontario, with coupling to the pelagic system, to examine ecosystem dynamics and effects of dreissenid mussel invasion and native fauna losses. Benthic organisms were represented by functional groups; filter-feeders (i.e., dreissenid mussels), surface deposit-feeders (e.g., native amphipod Diporeia spp.), and deposit-feeders (e.g., oligochaetes and other burrowers). The model was stable, represented ecological structure and function effectively, and reproduced observed effects of the mussel invasion. Two hypotheses for causes of Diporeia loss, competition or disease-like mortality, were tested. Simple competition for food did not explain observed declines in native surface deposit-feeders during the filter-feeder invasion. However, the elevated mortality scenario supports a disease-like cause for loss of the native amphipod, with population changes in various lake areas and altered benthic biomass transfers. Stabilization of mussel populations and possible recovery of the native, surface-deposit feeding amphipod were predicted. Although further research is required on forcing functions, model parameters, and natural conditions, the model provides a valuable tool to help managers understand the benthic system and plan for response to future disruptions.

Influence of Ocean Acidification and Deep Water Upwelling on Oligotrophic Plankton Communities in the Subtropical North Atlantic: Insights from an In situ Mesocosm Study

Oceanic uptake of anthropogenic carbon dioxide (CO2) causes pronounced shifts in marine carbonate chemistry and a decrease in seawater pH. Increasing evidence indicates that these changes—summarized by the term ocean acidification (OA)—can significantly affect marine food webs and biogeochemical cycles. However, current scientific knowledge is largely based on laboratory experiments with single species and artificial boundary conditions, whereas studies of natural plankton communities are still relatively rare. Moreover, the few existing community-level studies were mostly conducted in rather eutrophic environments, while less attention has been paid to oligotrophic systems such as the subtropical ocean gyres. Here we report from a recent in situ mesocosm experiment off the coast of Gran Canaria in the eastern subtropical North Atlantic, where we investigated the influence of OA on the ecology and biogeochemistry of plankton communities in oligotrophic waters under close-to-natural conditions. This paper is the first in this Research Topic of Frontiers in Marine Biogeochemistry and provides (1) a detailed overview of the experimental design and important events during our mesocosm campaign, and (2) first insights into the ecological responses of plankton communities to simulated OA over the course of the 62-day experiment. One particular scientific objective of our mesocosm experiment was to investigate how OA impacts might differ between oligotrophic conditions and phases of high biological productivity, which regularly occur in response to upwelling of nutrient-rich deep water in the study region. Therefore, we specifically developed a deep water collection system that allowed us to obtain ~85 m3 of seawater from ~650 m depth. Thereby, we replaced ~20% of each mesocosm's volume with deep water and successfully simulated a deep water upwelling event that induced a pronounced plankton bloom. Our study revealed significant effects of OA on the entire food web, leading to a restructuring of plankton communities that emerged during the oligotrophic phase, and was further amplified during the bloom that developed in response to deep water addition. Such CO2-related shifts in plankton community composition could have consequences for ecosystem productivity, biomass transfer to higher trophic levels, and biogeochemical element cycling of oligotrophic ocean regions.

Influence of ocean acidification on plankton community structure during a winter-to-summer succession: An imaging approach indicates that copepods can benefit from elevated CO2 via indirect food web effects.

Plankton communities play a key role in the marine food web and are expected to be highly sensitive to ongoing environmental change. Oceanic uptake of anthropogenic carbon dioxide (CO2) causes pronounced shifts in marine carbonate chemistry and a decrease in seawater pH. These changes–summarized by the term ocean acidification (OA)–can significantly affect the physiology of planktonic organisms. However, studies on the response of entire plankton communities to OA, which also include indirect effects via food-web interactions, are still relatively rare. Thus, it is presently unclear how OA could affect the functioning of entire ecosystems and biogeochemical element cycles. In this study, we report from a long-term in situ mesocosm experiment, where we investigated the response of natural plankton communities in temperate waters (Gullmarfjord, Sweden) to elevated CO2 concentrations and OA as expected for the end of the century (~760 μatm pCO2). Based on a plankton-imaging approach, we examined size structure, community composition and food web characteristics of the whole plankton assemblage, ranging from picoplankton to mesozooplankton, during an entire winter-to-summer succession. The plankton imaging system revealed pronounced temporal changes in the size structure of the copepod community over the course of the plankton bloom. The observed shift towards smaller individuals resulted in an overall decrease of copepod biomass by 25%, despite increasing numerical abundances. Furthermore, we observed distinct effects of elevated CO2 on biomass and size structure of the entire plankton community. Notably, the biomass of copepods, dominated by Pseudocalanus acuspes, displayed a tendency towards elevated biomass by up to 30–40% under simulated ocean acidification. This effect was significant for certain copepod size classes and was most likely driven by CO2-stimulated responses of primary producers and a complex interplay of trophic interactions that allowed this CO2 effect to propagate up the food web. Such OA-induced shifts in plankton community structure could have far-reaching consequences for food-web interactions, biomass transfer to higher trophic levels and biogeochemical cycling of marine ecosystems.

Three-phase fluidized bed bioreactor modelling and simulation

A mathematical model of a three-phase fluidized bed biofilm reactor for aerobic processeses is presented. The growth of attached biomass, its decay and interphase transfer were taken into consideration in the proposed quantitative description of the bioreactor. The presented model of the fluidized-bed bioreactor is the unique one which takes into account partial thickening of biomass and its recirculation. The stationary characteristics was determined with the use of a novel simplified numerical method for the assessment of stability of steady states. The effect of microbial growth kinetics on steady state multiplicity was characterized. The relationship between biofilm growth and boundaries of fluidized bed existence was shown. Conditions of the biofilm’s existence on carrier particles were formulated. Some novel dynamic characteristics concerning fluidized bed bioreactors were presented.

Biomass Reallocation between Juveniles and Adults Mediates Food Web Stability by Distributing Energy Away from Strong Interactions.

Ecological theory has uncovered dynamical differences between food web modules (i.e. low species food web configurations) with only species-level links and food web modules that include within-species links (e.g. non-feeding links between mature and immature individuals) and has argued that these differences ought to cause food web theory that includes within-species links to contrast with classical food web theory. It is unclear, however, if life-history will affect the observed connection between interaction strength and stability in species-level theory. We show that when the predator in a species-level food chain is split into juvenile and adult stages using a simple nested approach, stage-structure can mute potentially strong interactions through the transfer of biomass within a species. Within-species biomass transfer distributes energy away from strong interactions promoting increased system stability consistent with classical food web theory.

Impact of the 3 °C temperature rise on bacterial growth and carbon transfer towards higher trophic levels: Empirical models for the Adriatic Sea

Abstract The Mediterranean Sea (including the Adriatic Sea) has been identified as a ‘hotspot’ for climate change, with the prediction of the increase in water temperature of 2–4 °C over the next few decades. Being mainly oligotrophic, and strongly phosphorus limited, the Adriatic Sea is characterized by the important role of the microbial food web in production and transfer of biomass and energy towards higher trophic levels. We hypothesized that predicted 3 °C temperature rise in the near future might cause an increase of bacterial production and bacterial losses to grazers, which could significantly enlarge the trophic base for metazoans. This empirical study is based on a combined ‘space-for-time substitution’ analysis (which is performed on 3583 data sets) and on an experimental approach (36 in situ grazing experiments performed at different temperatures). It showed that the predicted 3 °C temperature increase (which is a result of global warming) in the near future could cause a significant increase in bacterial growth at temperatures lower than 16 °C (during the colder winter-spring period, as well as in the deeper layers). The effect of temperature on bacterial growth could be additionally doubled in conditions without phosphorus limitation. Furthermore, a 3 °C increase in temperature could double the grazing on bacteria by heterotrophic nanoflagellate (HNF) and ciliate predators and it could increase the proportion of bacterial production transferred to the metazoan food web by 42%. Therefore, it is expected that global warming may further strengthen the role of the microbial food web in a carbon cycle in the Adriatic Sea.

Simulation study on combustion of biomass

Biomass combustion is the most common energy conversion technology, offering the advantages of low cost, low risk and high efficiency. In this paper, the transformation and transfer of biomass in the process of combustion are discussed in detail. The process of furnace combustion and gas phase formation was analyzed by numerical simulation. The experimental results not only help to optimize boiler operation and realize the efficient combustion of biomass, but also provide theoretical basis for the improvement of burner technology.

Mass seasonal bioflows of high-flying insect migrants.

Migrating animals have an impact on ecosystems directly via influxes of predators, prey, and competitors and indirectly by vectoring nutrients, energy, and pathogens. Although linkages between vertebrate movements and ecosystem processes have been established, the effects of mass insect "bioflows" have not been described. We quantified biomass flux over the southern United Kingdom for high-flying (>150 meters) insects and show that ~3.5 trillion insects (3200 tons of biomass) migrate above the region annually. These flows are not randomly directed in insects larger than 10 milligrams, which exploit seasonally beneficial tailwinds. Large seasonal differences in the southward versus northward transfer of biomass occur in some years, although flows were balanced over the 10-year period. Our long-term study reveals a major transport process with implications for ecosystem services, processes, and biogeochemistry.

Regional synchrony in full-scale activated sludge bioreactors due to deterministic microbial community assembly.

Seasonal community structure and regionally synchronous population dynamics have been observed in natural microbial ecosystems, but have not been well documented in wastewater treatment bioreactors. Few studies of community dynamics in full-scale activated sludge systems facing similar meteorological conditions have been done to compare the importance of deterministic and neutral community assembly mechanisms. We subjected weekly activated sludge samples from six regional full-scale bioreactors at four wastewater treatment plants obtained over 1 year to Illumina sequencing of 16S ribosomal RNA genes, resulting in a library of over 17 million sequences. All samples derived from reactors treating primarily municipal wastewater. Despite variation in operational characteristics and location, communities displayed temporal synchrony at the individual operational taxonomic unit (OTU), broad phylogenetic affiliation and community-wide scale. Bioreactor communities were dominated by 134 abundant and highly regionally synchronized OTU populations that accounted for over 50% of the total reads. Non-core OTUs displayed abundance-dependent population synchrony. Alpha diversity varied by reactor, but showed a highly reproducible and synchronous seasonal fluctuation. Community similarity was dominated by seasonal changes, but individual reactors maintained minor stable differences after 1 year. Finally, the impacts of mass migration driven by direct biomass transfers between reactors was investigated, but had no significant effect on community similarity or diversity in the sink community. Our results show that population dynamics in activated sludge bioreactors are consistent with niche-driven assembly guided by seasonal temperature fluctuations.

Dynamic properties of a continuous stirred tank biofilm bioreactor for aerobic processes

A dynamic analysis of a continuous stirred tank bioreactor with biofilm was performed. The existence of gas, liquid, and biofilm were taken into account. The proposed heterogeneous model of such bioreactor takes into account dynamic biofilm growth and interphase transfer of substrates and biomass for a double‐substrate aerobic process. Simulations were performed to investigate the influence of important process parameters, i.e., toxic substrate concentration in the feed stream, detachment rate coefficient, mean residence time of the liquid and aeration intensity, on dynamic properties of the bioreactor. Dynamic behavior at conditions of anoxia of microorganisms were shown. A method was proposed to reduce bioreactor start‐up time significantly. The paper presents a mathematical model of the bioreactor that uses a discrete model of biofilm growth based on the theory of cellular automata. Dynamics of the bioreactor based on the continuous and discrete biofilm model was compared. © 2016 American Institute of Chemical Engineers AIChE J, 63: 1818–1829, 2017

English

Small-scale farmers in Zambia are faced with problems of low crop productivity, scarcity of fuel wood and fodder, and subsequently are generally food insecure. Agroforestry can contribute to food and income security, amelioration of the environment and subsequently, to mitigation of climate change effects. However, despite all the potential of agroforestry technologies and the effort to promote them among smallholder farmers, their adoption and diffusion have remained low and so has their impact. Unless farmers adopt some of these technologies as part of their farming system, the potential benefits of agroforestry to food security, livelihoods and the environment will not be realized. This study investigated trialing and adoption levels of agroforestry in eastern Zambia where agroforestry has been researched and promoted for over two decades. A survey was completed of 388 small scale farmers. Data analysis shows that testing of improved fallows and biomass transfer, though low at 44.9 and 21.4% respectively, was higher than that of domestication of indigenous fruits (4.4%), Fodder banks (3.9%) and Woodlots (3.1%). The study however found that adoption rate of agroforestry among farmers that initially tested is high. Factors that affect adoption include lack of seed, limited land size, method of ploughing, lack of interest and access to extension services. Therefore we advocate for intensified promotion and encouragement support so that more farmers can trial these technologies. With high trialing rates, adoption of agroforestry is likely to increase. The key policy implication of this study is the necessity to embark on educating farmers so that they can trial and subsequently experience the impact of agroforestry technologies. Agroforestry will only make meaningful contribution to improving land productivity and farmer livelihoods if it is adopted. Key words: Adoption, agroforestry, biomass transfer, improved tree fallows, logistic regression, smallholder farmers, Zambia.

Balanced harvesting is the bioeconomic equilibrium of a size-structured Beverton-Holt model

Balanced harvesting (BH) was introduced as an alternative strategy to size-at-entry fishing with the aim of maintaining ecosystem structure and functioning. BH has been criticized on a number of grounds, including that it would require an infeasible level of micromanagement and enforcement. Recent results from a size-spectrum model show that the distribution of fishing mortality across body sizes that emerges from the behaviour of a large number of fishing agents corresponds to BH in a single species. Size-spectrum models differ from classical size-structured models used in fisheries as they are based on a bookkeeping of biomass transfer from prey to predator rather than a von Bertalanffy growth model. Here we investigate a classical Beverton-Holt model coupled with the Gordon-Schaefer harvesting model extended to allow for differential fishing pressure at different body sizes. This models an open-access fishery in which individual fishing agents act to maximize their own economic return. We show that the equilibrium of the harvesting model produces an aggregate fishing mortality that is closely matched to the production at different body sizes, in other words BH of a single species. These results have significant implications because they show that the robustness of BH does not depend on arguments about the relative production levels of small versus large fish.