Biomass Surrogate Research Articles

Host-diet-gut microbiome interactions influence human energy balance: a randomized clinical trial

The gut microbiome is emerging as a key modulator of human energy balance. Prior studies in humans lacked the environmental and dietary controls and precision required to quantitatively evaluate the contributions of the gut microbiome. Using a Microbiome Enhancer Diet (MBD) designed to deliver more dietary substrates to the colon and therefore modulate the gut microbiome, we quantified microbial and host contributions to human energy balance in a controlled feeding study with a randomized crossover design in young, healthy, weight stable males and females (NCT02939703). In a metabolic ward where the environment was strictly controlled, we measured energy intake, energy expenditure, and energy output (fecal and urinary). The primary endpoint was the within-participant difference in host metabolizable energy between experimental conditions [Control, Western Diet (WD) vs. MBD]. The secondary endpoints were enteroendocrine hormones, hunger/satiety, and food intake. Here we show that, compared to the WD, the MBD leads to an additional 116 ± 56 kcals (P < 0.0001) lost in feces daily and thus, lower metabolizable energy for the host (89.5 ± 0.73%; range 84.2-96.1% on the MBD vs. 95.4 ± 0.21%; range 94.1-97.0% on the WD; P < 0.0001) without changes in energy expenditure, hunger/satiety or food intake (P > 0.05). Microbial 16S rRNA gene copy number (a surrogate of biomass) increases (P < 0.0001), beta-diversity changes (whole genome shotgun sequencing; P = 0.02), and fermentation products increase (P < 0.01) on an MBD as compared to a WD along with significant changes in the host enteroendocrine system (P < 0.0001). The substantial interindividual variability in metabolizable energy on the MBD is explained in part by fecal SCFAs and biomass. Our results reveal the complex host-diet-microbiome interplay that modulates energy balance.

Kinetic Model of Catalytic Steam Gasification of 2-Methoxy-4-methylphenol Using 5% Ni–0.25% Ru/γAl2O3 in a CREC-Riser Simulator

Hydrogen is an energy vector with a great potential due its ample range of applications and clean combustion cycle. Hydrogen can be produced through biomass steam gasification, with novel catalysts being of significant value to implement this process. With this goal in mind, in the present study, 5 wt % Ni/γAl2O3 promoted with 0.25 wt % Ru was synthesized and characterized. It is assumed that ruthenium facilitates hydrogen transfer to nickel oxide sites, promoting a hydrogen spillover effect, with the H2 adsorbed on Ru being transported to Ni sites. To describe chemical changes, the present study considers a kinetic model involving Langmuir–Hinshelwood-based rate equations, as a sum of independent reactions, with this being applied to the steam gasification of 2-methoxy-4-methylphenol (2M4MP). This tar biomass surrogate was studied in a fluidized CREC (Chemical Reactor Engineering Centre) Riser Simulator reactor, at different reaction times (5, 20 and 30 s.) and temperatures (550 °C, 600 °C and 650 °C). The proposed kinetics model was fitted to the experimentally observed H2, CO2, CO, CH4 and H2O concentrations, with the estimated pre-exponential factors and activation energies being in accordance with the reported literature data. It is anticipated that the postulated model could be of significant value for the modeling of other biomass conversion processes for hydrogen production using other supported catalysts.

Calculations of complex chemical reaction equilibria using stoichiometric and non‐stoichiometric approaches in combination with arc‐length continuation

AbstractChemical equilibrium calculations—as they are required to evaluate the evolution limits of any reactive system—are fundamentally performed using either a reaction based stoichiometric (S) approach or a non‐stoichiometric (NS) method. One objective of the present paper is to check and discuss whether both methods lead to comparable solutions in the case of complex chemical equilibria encountered in high temperature and pressure combustion of hydrazine and propane and in steam gasification of glucose and cellulose. Within both calculation models various numerical methods can be used. We apply several techniques for each approach and discuss their easiness of implementation and usage, in particular when chemical equilibria are computed for reacting systems under a multitude of temperature and pressure conditions and feed compositions. In addition, we present a novel approach to perform sensitivity analyses based on a combination of S or NS methods and arc‐length continuation technique. For this purpose, three industrially relevant case studies are exposed: (1) synthesis of ammonia using the Haber process, (2) steam gasification of a typical biomass surrogate, glucose, and (3) steam gasification of cellulose. For all the above reacting systems, our results are benchmarked against their counterparts obtained either from the ubiquitous process simulator: ASPEN‐Plus® or from data available in the open literature.

Fluidizable Ni/Ce-meso-Al2O3 for gasification of glucose: Effect of catalyst reduction on hydrogen selectivity

A new template-free technique is applied to develop fluidizable Ce-Al2O3 support and impregnated with nickel. The Ni(x)/Ce-Al2O3 catalysts are evaluated in a fluidized CREC Riser Simulator using glucose as biomass surrogate. XRD shows that nickel is well-dispersed on Ce-Al2O3. The acidity of the catalysts decreased from 0.317 to 0.202mmol NH3/g-sample as the nickel loading was increased. In catalyst evaluation, it is found that the reduced catalysts favor bond cleavage, promotes water gas shift and steam reforming reactions to give hydrogen/syngas as more selective products. Ni(20)/Ce-Al2O3 exhibited lowest extent of coking and produced hydrogen rich syngas with H2/CO≈1.75:1.

Promotional effects of Ce on Ni[sbnd]Ce/γAl2O3 for enhancement of H2 in hydrothermal gasification of biomass

This communication presents promotional effects of Ce on a NiCe/γ-Al2O3 catalyst for biomass gasification in hydrothermal reaction conditions. The catalyst samples were prepared by an incipient wetness technique using a successive metal loading approach. The TPR/TPO results showed that the presence of Ce minimized metal support interaction and improved the reducibility and thermal stability of the catalyst. The XRD analysis of fresh and reduced (after 10 repeated TPR/TPO cycles) catalyst samples showed unchanged crystal structures of the nickel particles indicating stable properties of the NiCe/γAl2O3 catalyst. The hydrothermal biomass gasification experiments were conducted using glucose as a biomass surrogate at various reaction temperature (425–525 °C) and time (5–35 min), while the pressure was maintained at 25.5 MPa. It was observed that the addition of Ce influenced the catalyst surface creating more active nickel sites for steam reforming methane reaction. Ce also increased the activity of Ni/γAl2O3 catalysts in terms of hydrogen production by promoting the water gas shift reaction and suppressing the methanation reaction of carbon dioxide.

Kinetics of Steam Gasification of Glucose as a Biomass Surrogate over Ni/Ce–Mesoporous Al2O3 in a Fluidized Bed Reactor

This study reports the kinetics of steam gasification of glucose as a biomass surrogate over a new Ni(x)/Ce-doped Al2O3 (x = 5, 10, 15, and 20 wt %) catalyst in a fluidized bed reactor. The presence of ceria plus successive nickel impregnation helped in conserving the catalyst’s high surface area (i.e., 102 m2/g at 20 wt % nickel loading). Incorporation of ceria dopant suppressed coke formation during steam gasification of 15 wt % glucose in the fluidized bed reactor at 650 °C and 1 atm in the order Ni(20) < Ni(15) < Ni(10) < Ni(5)/Ce-doped Al2O3. The detailed kinetic model comprises reactant adsorption, surface reaction, and product desorption steps, involving the water gas shift reaction (WGS), steam reforming of methane (SRM), and reverse dry reforming of methane (RDRM). Ni(20)/Ce-doped Al2O3 with the best performance in terms of syngas production, and the least tendency for coking, was used for the kinetic studies (for T = 550–700 °C and t = 5–25 s). The results of the model simulation indicate that t...

Steam gasification of a cellulosic biomass surrogate using a Ni/La2O3-γAl2O3 catalyst in a CREC fluidized riser simulator. Kinetics and model validation

This study describes a Langmuir-Hinshelwood based mechanistic kinetic model for the catalytic steam gasification of glucose, a biomass surrogate. This model accounts for the algebraic addition of dominant reactions: water gas-shift, the steam reforming of methane and the reverse dry reforming of methane. Reaction runs are developed in a mini-fluidized CREC Riser Simulator reactor using a highly performing Ni/La2O3-γ-Al2O3 catalyst. H2, CO, CO2, CH4 and H2O are the major product species observed with negligible coke and tar being formed. For adequate parameter estimation and model validation, two experimental data sets are considered. The first data set includes runs at different temperatures and reaction times. This data set is used to establish intrinsic kinetic parameters with narrow 95% confidence spans and low cross-correlation. The proposed model is validated using a second data set obtained by varying S/B ratio and reaction time. Thus, the proposed model includes phenomenologically based parameters that can successfully account for various observable chemical species in a wide range of operating conditions.

Disproportionately large ecological role of a recently mass-culled flying fox in native forests of an oceanic island

Human-wildlife conflicts pose a growing threat to many species worldwide and require increasingly innovative and multi-disciplinary resolutions. Because of their apparent simplicity and political appeal, lethal approaches like culling are often favoured, decisions to cull are typically poorly supported by scientific evidence and the limitations and drawbacks of culls minimised. As natural habitats decline and fruit crop production expands, fruit-eating bats in the Old World (family Pteropodidae) are increasingly in conflict with fruit farmers. This conflict is exemplified on Mauritius where the government has implemented two mass culls of a threatened flying fox (Pteropus niger) since 2015 in response to fruit-grower concerns. The culls and illegal hunting reduced the bat population by >50%. In this context, we sought to investigate the ecological role and service provided by the targeted flying fox through seed dissemination to gauge what may be lost as the species becomes rarer or extinct. We randomly sampled the woody native community in six of the best-preserved moist-to-wet native forests of Mauritius using 90 plots of 100m2 each and identified and measured the stem size of all woody plants ≥1cm in diameter. Species were classified by whether their fruits occur in the diet of the flying fox in an exclusive, confirmed or likely manner and we assumed that fruit consumption is equivalent to potential seed dissemination. The relative importance of these three categories to the total woody plant community was then quantified as the proportion of species richness, stem density and basal area (as a surrogate of biomass) that they represent. We also investigated whether the main traits of species (seed size, fruit size, and maximum stem diameter) vary among bat-dispersal categories and differ from those of species whose fruits are not currently known to be eaten by the flying fox. On average, although about a quarter of the native woody species (24.6%) have fruits confirmed as eaten and seeds dispersed by the flying fox, these species comprise about half (53.1%) of the stems sampled and the majority (63.1%) of the basal area of native woody plant in the island’s native forests. About half of that latter biomass figure comprises species for which the flying fox is the exclusive native vertebrate frugivore and seed disperser. Plants disseminated by the flying fox are typically large trees with large fruit and seeds. These trees are often key components of the canopy, therefore fulfilling structural engineer roles that provide resources and conditions for the survival of many forest species. The flying fox plays a disproportionally large ecological role in maintaining forest structure and biodiversity in the long-term. Consequently, lethal approaches to the conflict with fruit-farmers threaten not only an endangered species, but ecological processes central to the viability of native forests. Our findings highlight the importance of including the ecological costs of culling in decision-making processes intended to resolve human-wildlife conflicts.

Enhancement of glucose gasification by Ni/La2O3-Al2O3 towards the thermodynamic extremum at supercritical water conditions

This communication presents the promotional effects of La on Ni/La-Al2O3 catalyst for biomass gasification in supercritical water using glucose as a biomass surrogate. The experimental findings were also compared with the product compositions predicted by the thermodynamic model. In modeling, the equations of state (EoS) by Peng–Robinson, as well as by Duan, were separately used to derive the residual Gibbs' free energy and compressibility factor, Z. Results, obtained by both EoS showed close agreement. The accuracy of our calculation was checked by comparing the compressibility factor, Z of the gaseous products, with those obtained from Aspen-HYSYS. In all cases considered, the percentage error in Z was less than 10%. Moreover, we have found that water to glucose (W/G) ratio affects the syngas composition. For example, at 600 °C and 25 MPa, an increase in W/G ratio from 6 to 9 led to an increase in H2/CO ratio from ∼3.2 to ∼4.7. On the other hand, operating pressure has little effect on syngas composition. This finding could be useful in the design and optimization of supercritical water gasification (SCWG) plants. Finally, we also observed that lanthanum helped to drive the hydrogen yield towards the thermodynamic extremum, while at the same time scavenging CO2 and coke, and retarding the methanation reaction.

Enhanced ignition of biomass in presence of NOx

Accumulation of combustible biomass residues on hot surfaces of processing machineries can pose fire hazards. In addition, the presence of nitrogen oxides (NOx) from plant equipment alters the local conditions, aggravating the propensity for low temperature ignition risks. This study presents an experimental study on a relative effect of NOx on ignition temperature of morpholine, an important surrogate of biomass, to reveal the sensitising role of NOx in ignition of biomass fuels and to gain mechanistic insights into the chemical aspect of this behaviour in fire. The experiments employed a flow-through tubular reactor, operated at constant pressure and residence time of 1.01bar and 1.0s, respectively, and coupled with a Fourier-transform infrared spectroscope. For a representative fuel-rich condition (Φ=1.25), the concentration of NOx as small as 0.06% lowers the ignition temperature of morpholine by 150°C, i.e., from approximately 500°C to 350°C. The density functional theory (DFT) calculations performed with the CBS-QB3 composite method, that comprises a complete basis set, characterised the dynamics and energies of the elementary nitration reactions. We related the observed reduction in ignition temperature to the formation of unstable nitrite and nitrate adducts, as the result of addition of NOx species to morphyl and peroxyl radicals. Furthermore, the reaction of NOx with low-temperature hydroperoxyl radical leads to the formation of active OH species that also propagate the ignition process. The present findings quantify the ignition behaviour of biomass under NOx–doped atmospheres. The result is of great importance in practical applications, indicating that safe operation of wood-working plants requires avoiding trace concentration of NOx within the vicinity of biomass residues. This can be facilitated by proper (and separate) venting of engine exhausts.

Catalytic steam gasification of biomass surrogates: Thermodynamics and effect of operating conditions

Thermodynamic chemical equilibrium of biomass steam gasification is considered using both stoichiometric and non-stoichiometric analyses. These thermodynamic analyses include gaseous products, tars and coke, as well as consider a wide range of operating conditions. It is shown that both stoichiometric and non-stoichiometric approaches provide close results. Catalytic steam gasification of biomass surrogate species (glucose and 2-methoxy-4-methylphenol) is developed in a CREC Riser Simulator under the expected conditions of a circulating fluidized bed gasifier. A highly active and stable fluidizable Ni/La2O3-γ-Al2O3 catalyst is employed in this study, to investigate the effects of gasifier operating conditions. This catalyst yields 98% carbon conversion of glucose to permanent gases with no tar formation and negligible coke deposition at 700°C. Catalytic gasification results with the variation of temperature and steam/biomass ratio show limited deviation from equilibrium predictions. The deviation between experimental results and equilibrium predictions can be attributed to the relatively shorter reaction time (20s). As the reaction time is increased, experimental results approach chemical equilibrium. For 2-methoxy-4-methylphenol gasification, 90% carbon conversion is obtained with only 5.7wt% tar formation and 3.3wt% coke deposition. Again chemical equilibrium predictions are close. The only exceptions are: (a) coke and methane being overestimated and (b) tars being underestimated. Regarding synthesis gas from glucose and 2-methoxy-4-methylphenol gasification, the Ni/La2O3-γ-Al2O3 catalyst yields a H2/CO ratio greater than 2.0.

Role of Potassium and Phosphorus in Catalytic Partial Oxidation in Short Contact Time Reactors

Potassium and phosphorus represent inorganics commonly found in biomass and can significantly affect catalytic gasification of biomass. The alkaline and acidic nature of potassium and phosphorus, respectively, can introduce different reaction chemistries. In this paper, the effects of potassium and phosphorus on Rh catalysts for catalytic gasification have been studied at different fuel/oxygen ratios and temperatures. Catalytic partial oxidation (CPO) of ethanol, a biomass surrogate, was carried out over potassium, phosphorus, and monobasic potassium-phosphate-doped catalysts at loadings of 0.1, 1, 10, and 100% of Rh atoms over a range of fuel/oxygen ratios. In addition, time-on-stream studies were also carried out with methane by predosing inorganics on the catalyst (10% loading) and ethanol by introducing inorganics in the feed (0.05 mol %) to understand their effects on the stability of autothermal operation. With ethanol CPO, synthesis gas selectivities did not change significantly with potassium-doped catalysts, whereas they decreased with phosphorus-doped catalysts. Monobasic potassium phosphate showed synergistic effects of potassium and phosphorus; however, at higher temperatures, the effect of phosphorus was predominantly observed as a result of volatilization of potassium. Similarly, with time-on-stream studies with methane CPO, potassium volatilized at higher temperatures, while phosphorus retained its catalytic activity at higher temperatures. With the introduction of potassium and phosphorus in ethanol feed, steady-state autothermal operation was possible without any deactivation of the catalyst. In all experiments, phosphorus exhibited a stronger poisoning effect on rhodium for catalytic partial oxidation than potassium at similar concentrations.

Fluidizable Ni/La2O3-γAl2O3 catalyst for steam gasification of a cellulosic biomass surrogate

This study reports a new fluidizable Ni catalyst supported on La2O3 modified γ-Al2O3. The 20% Ni/5% La2O3-γAl2O3 catalyst is prepared using a specially designed multistep incipient wetness technique and direct reduction of metal nitrate precursors. Steam gasification of glucose (a biomass surrogate), is developed in a CREC Riser Simulator using the new fluidizable catalyst. Experiments are performed at different steam/biomass ratios, temperatures and reaction times. Catalytic gasification runs confirm the high performance of the Ni/La2O3-γAl2O3 in terms of reforming activity, and reduced coke formation. Furthermore, observed gasification products (H2, CO, CO2, and CH4) are in agreement with thermodynamics, with product yields approaching chemical equilibrium as the reaction time is increased. Furthermore, the value of the Ni/La2O3-γAl2O3 catalyst is demonstrated while comparing its improved performance with respect to the one of other prepared catalysts: (i) an unpromoted Ni/γAl2O3 and (ii) a Ni/La2O3-γAl2O3 prepared via metal precursor calcination. Prepared catalysts are also characterized using BET surface area analysis, TPR, TPO, H2-pulse chemisorption, pyridine FTIR, CO2 and NH3 TPD. It is shown that the addition of lanthanum oxides reduces surface area losses, increasing the thermal stability of γ-Al2O3. La2O3 also improves reducibility and dispersion of the active phase by decreasing nickel-aluminate formation. Pyridine FTIR confirms the absence of Brønsted acid sites in γ-Al2O3, with La2O3 reducing Lewis acidity. Multiple TPO and TPR experiments also show that the prepared catalyst remains stable under repeated oxidation and reduction cycles. As a result, it is proven that the enhanced gasification activity of the Ni/La2O3-γAl2O3 fluidizable catalyst of the present study is in line with their various and favorable structural properties (available Ni surface area and basicity/acidity ratio) modifications.

Positive relationship between wood size and basidiocarp production of polypore fungi in Alnus acuminata forest

Polypores play a major role in wood decomposition. Based on presence/absence of basidiocarps, it has been shown that richness of polypores in forests is strongly affected by the size of logs. However, no study has addressed the relationship between the log size and basidiocarp production. Here, we examined the relationship between log diameter and number of basidiocarps and volume of the fructification (as surrogate of biomass) of the polypore community in Andean Alder forests from Northwest Argentina. We found a positive relationship between log diameter and basidiocarp production in the whole community analysis (fructifications of all species). This pattern was also followed by dominant species ( Bjerkandera adusta , Trametes cubensis and T. versicolor ) analyzed individually. The relationship was generally higher for volume of fructification than for number of basidiocarps. Through these effects on basidiocarp production, higher log diameter could promote higher sexual spore production and dispersal hence a higher genetic variability and viable populations of wood-decay species.

Interaction of top down and bottom up factors in intertidal rockpools: Effects on early successional macroalgal community composition, abundance and productivity

Increasing levels of eutrophication in coastal waters and recognition of natural variation in supply of nutrients, through for example variations in upwelling intensity, have led to an increasing demand to understand the role of bottom up forcing in coastal communities. Rocky intertidal habitats are highly disturbed and are composed of a patchy mosaic of assemblages in different successional stages. The role of consumer control of algae in such habitats is well recognised but the way consumer control interacts with variation in resource supply is still debated. We examined, using a factorial manipulative experiment, the way top down control by molluscan grazers interacts with nutrient supply to determine the community composition and productivity of early successional communities in intertidal rockpools. The experiment was run over a six-month period, through the summer months, when nutrients were potentially limiting. Rockpools were cleared of biota and nutrient supply enhanced using slow release fertiliser, while the level of molluscan grazing was reduced through regular removals. Macroalgal colonisation was rapid. Positive effects of nutrient enrichment on macroalgal cover were generally lower than the negative effects of grazer control, although at the peak of algal cover, nutrient effects were apparent irrespective of grazer treatment. There were distinct differences in the identity of dominant species among nutrient treatments with green Ulva spp. dominating under enhanced nutrient conditions and red Ceramium spp. dominating under ambient conditions. These differences contributed to a mismatch between effect estimates based on cover and those based on direct measures of productivity. The use of percentage cover as a surrogate of biomass in intertidal studies is discussed. The results indicate that in a disturbed environment enhanced nutrient supply can stimulate macroalgal blooms despite strong top down control by intertidal grazers.

Production of Hydrogen from Glucose as a Biomass Simulant: Integrated Biological and Thermochemical Approach

Hydrogen production from biomass was investigated using an integrated biological and thermochemical process. Glucose was used as a biomass surrogate and was first converted to ethanol in a fermentation process. The fermentation experiments were carried out using Saccharomyces cerevisiae. The fermentation broth was then used in aqueous phase reforming (APR) over a platinum-based catalyst. An economic analysis of the proposed process demonstrates the economic viability of producing hydrogen from biomass using fermentation combined with APR. The average production yield of hydrogen was ∼25%. The hydrogen obtained from APR of the fermentation broth was compared against the yield from a feed containing 5% ethanol in water. While the catalyst was stable for an extended time on stream during APR of ethanol, very rapid deactivation was observed during APR of fermentation broth. Different catalyst characterization techniques, including XRD, BET surface area, and ICP-AES, were employed to investigate the causes of catalyst deactivation. Although the analysis suggested similar catalyst changes in both cases, and the exact deactivation mechanism could not be concluded, these techniques helped to eliminate some mechanisms while suggesting other possible deactivation routes. Nanofiltration of the fermentation broth was shown to remove the impurities leading to deactivation.

Tree density, basal area and species diversity in a disturbed dry tropical forest of northern India: implications for conservation

Dry tropical forest communities are among the world's most threatened systems and urgent measures are required to protect and restore them in degraded landscapes. For planning conservation strategies, there is a need to determine the few essential measurable properties, such as number of species and basal area, that best describe the dry forest vegetation and its environment, and to document quantitative relationships among them. This paper examines the relationships between forest basal area and diversity components (number of species and evenness) for a disturbed dry tropical forest of northern India. Data were collected from five sites located in the Vindhyan dry tropical forest of India, selected on the basis of satellite images and field observations to represent the entire range of conditions in terms of canopy cover and disturbance regimes. These sites represented different communities in terms of species composition. The forest was poorer in species richness, and lower in stem density and basal area than wet forests of the tropics. Across sites (communities), the diversity components and tree density were positively related with total tree basal area. Considering basal area as a surrogate of biomass and net production, diversity is found to be positively associated with productivity. A positive relationship between basal area, tree density and species diversity may be an important characteristic of the dry forest, where recurring disturbance does not permit concentration of biomass or stems in only a few strong competitors. However, the relationships of basal area with density, alpha diversity and evenness remain statistically significant only when data from all sites, including the extremely disturbed one, are used in the analysis. In some sites there was a greater coefficient of variation (CV) of basal area than in others, attributed to patchy distribution of stems and resultant blanks. Therefore, to enhance the tree diversity of these forests, the variability in tree basal area must be reduced by regulating local disturbances. Conservation activities, particularly fuelwood plantations near human settlements, deferred grazing and canopy enrichment through multi-species plantations of nursery-raised or wild-collected seedlings of desirable species within the forest patches of low basal area, will be needed to attain restoration goals, but reforestation programmes will have to be made attractive to the forest-dwelling communities.

Testing the niche apportionment hypothesis with parasite communities: is random assortment always the rule?

Niche apportionment models have only been applied once to parasite communities. Only the random assortment model (RA), which indicates that species abundances are independent from each other and that interspecific competition is unimportant, provided a good fit to 3 out of 6 parasite communities investigated. The generality of this result needs to be validated, however. In this study we apply 5 niche apportionment models to the parasite communities of 14 fish species from the Great Barrier Reef. We determined which model fitted the data when using either numerical abundance or biomass as an estimate of parasite abundance, and whether the fit of niche apportionment models depends on how the parasite community is defined (e.g. ecto, endoparasites or all parasites considered together). The RA model provided a good fit for the whole community of parasites in 7 fish species when using biovolume (as a surrogate of biomass) as a measure of species abundance. The RA model also fitted observed data when ecto- and endoparasites were considered separately, using abundance or biovolume, but less frequently. Variation in fish sizes among species was not associated with the probability of a model fitting the data. Total numerical abundance and biovolume of parasites were not related across host species, suggesting that they capture different aspects of abundance. Biovolume is not only a better measurement to use with niche-orientated models, it should also be the preferred descriptor to analyse parasite community structure in other contexts. Most of the biological assumptions behind the RA model, i.e. randomness in apportioning niche space, lack of interspecific competition, independence of abundance among different species, and species with variable niches in changeable environments, are in accordance with some previous findings on parasite communities. Thus, parasite communities may generally be unsaturated with species, with empty niches, and interspecific interactions may generally be unimportant in determining parasite community structure.

Macroalgal Volume: a Surrogate for Biomass in Some Green Algae

Filamentous (e.g., Chaetomorpha spp.) and flattened or tubular (e.g., Ulva spp. and Enteromorpha spp.) green algal morphotypes were collected from the intertidal mudflat within the Yaquina Bay Estuary (Newport, OR, USA) and used to compare an in situ volumetric biomass estimator to the traditional dry weight methodology. Immediately following collection, wet volumes of each sample by morphotype were determined in situ using a modified graduated cylinder and a plunger. Samples were returned to the laboratory, dried to a constant weight, and then weighed. Both biomass estimators were compared using a linear regression technique. We found that dry weight was linearly related to volume (r2 = 0.78 to 0.88) for both morphotypes indicating that volume was an accurate predictor of biomass. We suggest the use of this technique, when appropriate, will enable researchers to quickly estimate macroalgal biomass in situ with savings in both time and expense.

Trends in Fish Community Structure, Biomass, and Production in Three Algoma, Ontario, Lakes

Long-term (i.e. >10 years) whole community fish dataincluding catch-per-unit-effort, abundance, biomass, andproduction from three lakes were used: 1) to examine variabilityin fish population and community measures among years using wholelake assessments of fish populations derived from mark recaptureexperiments, 2) to assess implications arising from monitoringindividual species vs. the whole fish community, and 3) toascertain whether, in fisheries assessments (science) a commonlyused surrogate measure, [catch-per-unit-effort (CPUE)] reflectedannual changes in the fish assemblage, and thus may be a goodestimator of abundance. High, long-term variability was evident in the abundance andbiomass of a fish species in our lakes, yet the communityremained relatively stable in terms of its biomass andproduction. Changes in total fish community biomass appear drivenby large species, which, relative to small fish species, remainstable among years. Among years, species richness remainedstable; however, fish species changed in the community. AnnualCPUE was found to be a suitable surrogate for abundance (N) ofsmall fishes; CPUE x mean weight of the catch (bCPUE) was asuitable surrogate for biomass (B) of large fishes. Prior toconcluding that a change in a fish population has occurred as aresult of a stressor, care must be taken to critically examinethe level of population assessment in order to avoid acceptingpotentially invalid conclusions.