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For the Blue Foods economy—those sectors that gain value from the biological productivity of the oceans such as fisheries and aquaculture—climate shocks pose an existential threat. Species range shifts, harmful algal blooms, marine heatwaves, low oxygen events, coral bleaching, and hurricanes all present a serious economic risk to these industries, and yet there exist few financial tools for managing these risks. This contrasts with agriculture, where financial tools such as insurance are widely available for managing numerous weather-related shocks. Designing financial tools to aid risk management, such as insurance, for equitable resilience against marine climate shocks will give coastal communities access to the necessary means for reducing their sensitivity to climate shocks and improving their long-term adaptive capacity. We suggest that a convergence of the insurance industry and marine sectors, fostered through collaboration with governments, academics, and NGOs will help usher in new forms of insurance, such as ocean-index or parametric insurance. These new risk-management tools have the potential to help incentivize sustainable use of living marine resources, as well as strengthening the economic resilience of coastal communities to climate change. [ABSTRACT FROM AUTHOR]

Resource use and conservation objectives can conflict where protected species and commercially fished species occur together. We tested the potential for a previously overfished deep-sea shark (Centrophorus zeehaani) with very low biological productivity to recover in a network of three reserves. An individual-based simulation model was developed and applied using reproduction and movement data. Without any reserves or reductions in fishing mortality the population will never recover and will fail in 27.9 ± 6.1 years. With three reserves, recovery from 8% of initial numbers to a target of 20% would take 63.1 ± 3.1 years with the network in place. Length of the female cycle, natural mortality, and density dependent female dispersal are uncertain, but could delay recovery time by an additional 16.5, 98.3, or 61.9 years, respectively. Effectiveness of the reserve network was particularly sensitive to location and patchiness of the population. Doubling the size of a reserve where C. zeehaani are abundant would reduce recovery time by 12.5 years; halving it would increase recovery time by 12.0 years. Future re-opening of orange roughy fishing in waters deeper than 750 m would delay recovery of C. zeehaani by 45.9 years. The methods developed here can be used to explore co-management options for target species and protected species in fisheries. [ABSTRACT FROM AUTHOR]

We show that planets around M-dwarfs with M ⋆ ≲ 0.2 M⊙ may not receive enough photons in the photosynthetically active range of 400–750 nm to sustain Earth-like biospheres. As a result of the lower biological productivity, it is likely that biotic molecular oxygen would not build-up to detectable levels in the atmospheres of habitable planets orbiting low-mass stars, consistent with prior work by Lehmer et al. We also estimate the minimum flaring rate for sustaining biospheres with Earth-like productivity and permitting the build-up of atmospheric oxygen, and find that the overwhelming majority of M-dwarfs are unlikely to exceed this threshold. [ABSTRACT FROM AUTHOR]

Abstract: Variation in rates of molecular evolution (heterotachy) is a common phenomenon among plants. Although multiple theoretical models have been proposed, fundamental questions remain regarding the combined effects of ecological and morphological traits on rate heterogeneity. Here, we used tree ferns to explore the correlation between rates of molecular evolution in chloroplast DNA sequences and several morphological and environmental factors within a Bayesian framework. We revealed direct and indirect effects of body size, biological productivity, and temperature on substitution rates, where smaller tree ferns living in warmer and less productive environments tend to have faster rates of molecular evolution. In addition, we found that variation in the ratio of nonsynonymous to synonymous substitution rates (dN/dS) in the chloroplast rbcL gene was significantly correlated with ecological and morphological variables. Heterotachy in tree ferns may be influenced by effective population size associated with variation in body size and productivity. Macroevolutionary hypotheses should go beyond explaining heterotachy in terms of mutation rates and instead, should integrate population‐level factors to better understand the processes affecting the tempo of evolution at the molecular level. [ABSTRACT FROM AUTHOR]

Abstract: The consequences of mutations for population fitness depends on their individual selection coefficients and the effective population size. An earlier study of Caenorhabditis elegans spontaneous mutation accumulation lines evolved for 409 generations at three population sizes found that Ne  = 1 populations declined significantly in fitness whereas the fitness of larger populations (Ne  = 5, 50) was indistinguishable from the ancestral control under benign conditions. To test if larger MA populations harbor a load of cryptic deleterious mutations that are obscured under benign laboratory conditions, we measured fitness under osmotic stress via exposure to hypersaline conditions. The fitness of Ne  = 1 lines exhibited a further decline under osmotic stress compared to benign conditions. However, the fitness of larger populations remained indistinguishable from that of the ancestral control. The average effects of deleterious mutations in Ne  = 1 lines were estimated to be 22% for productivity and 14% for survivorship, exceeding values previously detected under benign conditions. Our results suggest that fitness decline is due to large effect mutations that are rapidly removed via selection even in small populations, with implications for conservation practices. Genetic stochasticity may not be as potent and immediate a threat to the persistence of small populations as other demographic and environmental stochastic factors. [ABSTRACT FROM AUTHOR]

In the current manuscript, we have investigated the temporal as well as spatio-temporal dynamics of a three species modified Leslie–Gower food chain model with Holling type IV and Crowley–Martin function responses. We have shown that explosion in the top predator population can be prevented if group defence is sufficiently strong at the lowest trophic levels. This demonstrates that group defence can act as a damping mechanism, and prevent population explosion of apex predators. We also show that the spatially explicit model can exhibit diffusion-driven instability, that depends strongly on the intensity of the group defence, in the prey population. Standard bifurcation analysis and the period doubling route to chaos are also investigated. [ABSTRACT FROM AUTHOR]

Direct consumption of allochthonous resources generally yields poor growth and reproduction in zooplankton, but it is still unclear how trophic upgrading of terrestrial dissolved organic matter (tDOM) via the microbial food web may support zooplankton. We compared survival, somatic growth and reproduction of Daphnia magna fed with the heterotrophic flagellate Paraphysomonas vestita and three algal diets. Paraphysomonas was fed lake bacteria that used tDOM as a substrate to simulate an allochthonous diet that zooplankton encounter in lakes. The highest survival, growth and reproduction was achieved with a diet of Cryptomonas, while Daphnia performance was the worst when fed Microcystis. Paraphysomonas and Scenedesmus diets lead to intermediate growth and reproduction. Cryptomonas contained high amounts of essential polyunsaturated fatty acids (PUFA) and phytosterols that supported high somatic growth and reproduction, whereas poor performance of Daphnia on the cyanobacterial diet was most likely due to lack of sterols. Paraphysomonas contained some phytosterols, but not in sufficient amounts and also essential PUFA (eicosapentaenoic and arachidonic acid) that enhance zooplankton growth and reproduction. Our results indicate that the tDOM-based microbial food web supports Daphnia performance even as a sole food source, and may be important in providing zooplankton with essential biochemical components when phytoplankton quantity or quality is low. [ABSTRACT FROM AUTHOR]

Physiological traits are frequently used as indicators of tree productivity. Aquilaria species growing in a research planting were studied to investigate relationships between leaf-productivity traits and tree growth. Twenty-eight trees were selected to measure isotopic composition of carbon (δ13C) and nitrogen (δ15N) and monitor six leaf attributes. Trees were sampled randomly within each of four diametric classes (at 150 mm above ground level) ensuring the variability in growth of the whole population was represented. A model averaging technique based on the Akaike's information criterion was computed to identify whether leaf traits could assist in diameter prediction. Regression analysis was performed to test for relationships between carbon isotope values and diameter and leaf traits. Approximately one new leaf per week was produced by a shoot. The rate of leaf expansion was estimated as 1.45 mm day-1. The range of δ13C values in leaves of Aquilaria species was from -25.5‰ to -31‰, with an average of -28.4 ‰ (±1.5‰ SD). A moderate negative correlation (R2 = 0.357) between diameter and δ13C in leaf dry matter indicated that individuals with high intercellular CO2 concentrations (low δ13C) and associated low water-use efficiency sustained rapid growth. Analysis of the 95% confidence of best-ranked regression models indicated that the predictors that could best explain growth in Aquilaria species were δ13C, δ15N, petiole length, number of new leaves produced per week and specific leaf area. The model constructed with these variables explained 55% (R2 = 0.55) of the variability in stem diameter. This demonstrates that leaf traits can assist in the early selection of high-productivity trees in Aquilaria species. [ABSTRACT FROM AUTHOR]

The approach to fisheries termed "balanced harvesting" (BH) calls for fishing across the widest possible range of species, stocks, and sizes in an ecosystem, in proportion to their natural productivity, so that the relative size and species composition is maintained. Such fishing is proposed to result in higher catches with less negative impact on exploited populations and ecosystems. This study examines the models and the empirical evidence put forward in support of BH. It finds that the models used unrealistic settings with regard to life history (peak of cohort biomass at small sizes), response to fishing (strong compensation of fishing mortality by reduced natural mortality), and economics (uniform high cost of fishing and same ex-vessel price for all species and sizes), and that empirical evidence of BH is scarce and questionable. It concludes that evolutionary theory, population dynamics theory, ecosystem models with realistic assumptions and settings, and widespread empirical evidence do not support the BH proposal. Rather, this body of evidence suggests that BH will not help but will hinder the policy changes needed for the rebuilding of ecosystems, healthy fish populations, and sustainable fisheries. [ABSTRACT FROM AUTHOR]

Recycling of the 2-phosphoglycolate generated by the oxygenase reaction of Rubisco requires a complex and energy-consuming set of reactions collectively known as the photorespiratory cycle. Several approaches aimed at reducing the rates of photorespiratory energy or carbon loss have been proposed, based either on screening for natural variation or by means of genetic engineering. Recent work indicates that plant yield can be substantially improved by the alteration of photorespiratory fluxes or by engineering artificial bypasses to photorespiration. However, there is also evidence indicating that, under certain environmental and/or nutritional conditions, reduced photorespiratory capacity may be detrimental to plant performance. Here we summarize recent advances obtained in photorespiratory engineering and discuss prospects for these advances to be transferred to major crops to help address the globally increasing demand for food and biomass production. [ABSTRACT FROM AUTHOR]

Aims Biodiversity-ecosystem function experiments can test for causal relationships between planting diversity and community productivity. Planting diversity is routinely introduced as a design element in created wetlands, yet substantive support for the finding that early diversity positively affects ecosystem functioning is lacking for wetlands. We conducted a 2-year diversity-productivity experiment using freshwater wetland mesocosms to investigate community biomass production as affected by planted macrophyte functional richness. Methods A richness gradient of macrophytes in four emergent wetland plant functional groups was established in freshwater mesocosms for two consecutive years. Species-specific aboveground morphological traits of plant size were measured at peak growth in both years; rooting depth was measured for each species in the second year. Aboveground biomass (AGB) and belowground biomass (BGB) were harvested after peak growth in the second year; first year AGB was estimated from morphological traits in constructed regression equations. Net richness effects (i.e. both complementarity effects and selection effects) were calculated using an additive partitioning method. Important Findings Species richness had a positive effect on community AGB relative to monocultures in the first year. In the second year, mean AGB was significantly reduced by competition in the most species-rich mixtures and all mixtures underyielded relative to the average monoculture. Competition for soil resources was weaker belowground, whereby root distribution at depths >20 cm was reduced at the highest richness levels but overall BGB production was not affected. Changes in species biomass were strongly reflected by variation in species morphological traits, and species above and belowground performances were highly correlated. The obligate annual (Eleocharis obtusa), a dominant competitor, significantly contributed to the depression of perennial species' growth in the second growing season. To foster primary productivity with macrophyte richness in early successional communities of created wetlands where ruderal strategies are favored and competition may be stronger than species complementarity, unsystematic planting designs such as clustering the same or similar species could provide protection for some individuals. Additionally, engineering design elements fostering spatial or temporal environmental variability (e.g. microtopography) in newly created wetlands helps diversify the responses of wetland macrophyte species to their environment and could allow for greater complementarity in biomass production. [ABSTRACT FROM AUTHOR]

Biological production of fatty acid (FA)-derived products has gained increasing attention to replace petroleum-based fuels and chemicals. FA biosynthesis is highly regulated, and usually it is challenging to design rational engineering strategies. In addition, the conventional 'one sample at a time' method for lipid determination is time consuming and laborious, and it is difficult to screen large numbers of samples. Here, a method for detecting free FAs in viable cells using Nile red staining was developed for use in large-scale screening. Following optimization of the method, it was used for screening a cDNA library from the oleaginous yeast Yarrowia lipolytica for identification of genes/enzymes that were able to enhance free FA accumulation in Saccharomyces cerevisiae. Several novel enzymes resulting in increasing FA accumulation were discovered. These targets include a GPI anchor protein, malate dehydrogenase, glyceraldehyde 3-phosphate dehydrogenase, FA hydroxylase, farnesyltransferase, anoctamin, dihydrolipoamide dehydrogenase and phosphatidylethanolamine-binding protein. The best enzyme resulted in a 2.5-fold improvement in production of free FAs. Our findings not only provide a novel method for high-throughput evaluation of the content of free FAs, but also give new insight into how enzymes from Y. lipolytica may increase the production of fatty acids in S. cerevisiae. [ABSTRACT FROM AUTHOR]

We show in the present study that variations in the rates of survival and recruitment of the agile gracile opossum ( Gracilinanus agilis) are predominantly influenced by its life history instead of the variation in primary productivity that is common in the Brazilian Cerrado. For 5 years we monitored a population of G. agilis in a riparian forest running through the Cerrado and assessed the relationship between survival and breeding season, as well as the relationship between recruitment and seasons (dry and rainy). We also tested for a relationship between these rates and variations in primary productivity. The survival of males was better predicted by reproductive season than primary productivity and survival decreased after the reproductive season. Females showed a similar pattern. Our data show the reproduction of G. agilis is seasonal, with recruitment in the rainy season. The demographic analysis made in the present study suggests the adoption of a semelparous strategy in this species. [ABSTRACT FROM AUTHOR]

Aims The rate of climate change may exceed many plant species’ migration rates, particularly for long-lived perennial species that dominate most ecosystems. If bioclimatic envelopes shift more rapidly than dominant species can migrate, individuals located peripheral to biomes or in adjacent biomes may become a significant source of traits for future dominant populations (DPs). Thus, traits of individuals from peripheral populations (PPs) may affect future ecosystem functioning more than those of today’s DPs. Methods We assessed key traits of individuals collected from populations that currently dominate two central US grasslands, the shortgrass steppe (Bouteloua gracilis) and the tallgrass prairie (Andropogon gerardii). We compared these to individuals from PPs in a reciprocal-transplant common garden experiment with gardens at the Shortgrass Steppe Long Term Ecological Research site in Colorado and the Konza Prairie Biological Station Long Term Ecological Research site in Kansas. DPs and PPs were subjected to high and reduced water availability in common gardens located in each biome. Traits measured included the following: individual plant biomass, reproductive allocation, specific leaf area (SLA) and plant–water relations. We focused on the climate-change relevant comparisons of traits from PPs versus DPs expressed under the climate of DPs. Important Findings PPs of B. gracilis differed from DPs primarily in phenological traits. Under a semiarid shortgrass steppe climate, PPs initiated flowering later in the season, produced fewer reproductive tillers and were more sensitive to water stress. Biomass differences between populations were minimal. For A. gerardii, biomass in PPs was 50% lower than in DPs under the mesic tallgrass prairie climate and reproductive tillers were considerably smaller, despite higher SLA in PPs. Biomass of PPs was less sensitive to water stress, however. From these results, we conclude that key traits of PPs differed from DPs in both grassland types, but potential effects on reproductive phenology were greater for the bioclimatic shift in which a mesic biome becomes arid, whereas aboveground productivity may be affected more when a semiarid biome becomes more mesic. [ABSTRACT FROM AUTHOR]

The evolution of autotrophy is considered in relation to the availability of phosphorus (P), the ultimate elemental resource limiting biological productivity through Earth’s history. Work on microbes and plants is emphasized, dealing in turn with the main uses for P in cells, namely nucleic acids, phospholipids, and water-soluble low molecular mass phosphate esters plus metabolically active inorganic orthophosphate. There is a greater minimum gene number and minimum DNA content in autotrophic than in osmochemoorganotrophic archaea and bacteria, as well as a lower rate of biomass increase per unit P (P-use efficiency) in autotrophs than in osmochemoorganotrophs, in eukaryotes as well as bacteria. This may be due to the diversion of rRNA from producing proteins common to all organisms to producing highly expressed proteins specific to autotrophs. The P requirement for phospholipids is decreased in oxygenic photolithotrophs, and some anoxygenic photolithotrophs, by substituting galactolipids and sulpholipids for phospholipids in the photosynthetic, and some other, membranes. The six different autotrophic inorganic carbon assimilation pathways have varying requirements for low molecular mass water-soluble phosphate esters. In oxygenic photolithotrophs, there is no clear evidence of a different P requirement for growth in the absence (diffusive CO2 entry) relative to the presence of CO2-concentrating mechanisms (CCMs). P limitation increases the expression of crassulacean acid metabolism (CAM) in facultative CAM plants, decreases the extent of inorganic carbon accumulation in algae with CCMs, and (usually) their inorganic carbon affinity and the water-use efficiency of growth of terrestrial plants, and the light-use efficiency of photolithotrophs. [ABSTRACT FROM PUBLISHER]

Community assembly is driven by multiple factors, including resource availability and habitat requirements. Litter nesting ants respond to food and nest site availability, and adding food and nests may increase ant species richness and abundance. However, litter decomposers share food resources with ants, and increasing food availability may speed decomposition processes, eliminating twigs and seeds in which litter ants nest. We manipulated ant food and nest resources in three habitat types (forest, high-shade coffee, and low-shade coffee) to determine ant community responses after 1 and 2 mo. We examined changes in numbers of ant species, colonies, workers, brood, colony growth rate, and ant species composition. Habitat type strongly affected ant communities, influencing ant species richness, numbers of colonies and workers, and ant species composition. However, food addition and nest addition did not affect these community characteristics. Colony growth rate did not differ with food addition but was greater in forest and low-shade coffee compared with high-shade coffee. Habitat differences in colony growth may be because of presence of an aggressive species (Wasmannia auropunctata Roger) in high-shade coffee plots or naturally low arthropod densities during a time when ant colonization was low. Thus, in coffee landscapes, habitat type impacts litter nesting ant community structure, composition, and colony growth rate; however, food and nest addition had small impacts. [ABSTRACT FROM AUTHOR]

This article gives an overview of high-cell-density cultures for polyhydroxyalkanoate (PHA) production and their modes of operation for increasing productivity. High cell densities are very important in PHA production mainly because this polymer is an intracellular product accumulated in various microorganisms, so a high cellular content is needed for the polymer production. This review describes relevant results from fed-batch, repeated batch, and continuous modes of operation without and with cell recycle for the production of these polymers by microorganisms. Finally, recombinant microorganisms for PHA production, as well future directions for PHA production, are discussed. [ABSTRACT FROM AUTHOR]

The food webs of terrestrial soils and of freshwater and marine sediments depend on adjacent aboveground or pelagic ecosystems for organic matter input that provides nutrients and energy. There are important similarities in the flow of organic matter through these food webs and how this flow feeds back to primary production. In both soils and sediments, trophic interactions occur in a cycle in which consumers stimulate nutrient cycling such that mineralized resources are made available to the primary producers. However, aquatic sediments and terrestrial soils differ greatly in the connectivity between the production and the consumption of organic matter. Terrestrial soils and shallow aquatic sediments can receive organic matter within hours of photosynthesis when roots leak carbon, whereas deep oceanic sediments receive organic matter possibly months after carbon assimilation by phytoplankton. This comparison has implications for the capacity of soils and sediments to affect the global carbon balance. [ABSTRACT FROM AUTHOR]

Lost biomass of anadromous forage species resulting from the seventeenth to nineteenth century damming of waterways and from overharvest in the northeastern United States contributed to significant changes in coastal marine-terrestrial ecosystems. Historic alewife populations in Maine for the years 1600-1900 were assessed using analyses of nineteenth and twentieth century harvest records and waterway obstruction records dating to the 1600s. Obstructed spawning access in nine watersheds reduced the annual alewife productivity per watershed to 0%-16% of virgin estimates, equaling a cumulative lost fisheries production of 11 billion fish from 1750 to 1900. Including preharvest production, our estimates suggest a lost flux of anadromous forage fish increasing from 10 million fish per year in 1700 to 1.4 billion annually by 1850. Our results suggest a realignment of current restoration goals is needed to recognize oceanic and freshwater ecosystem interdependence and the gap between current targets and potential productivity. [ABSTRACT FROM AUTHOR]

Small mammal assemblages in the aridlands of the Southern Hemisphere often have wildly fluctuating dynamics. Previous studies have attributed these fluctuations to climate-driven pulses in food resources resulting in the switching of trophic control from bottom-up (food-limited) to top-down (predation-limited) population regulation, and vice versa. In this study we use a meta-analytic approach to evaluate the evidence for the phenomenon of switching trophic control. If shifting trophic control is a unifying phenomenon that shapes small mammal assemblages in arid Australia, we would expect the abundance and species richness of small mammals to increase with increasing primary productivity and the abundance of small mammals to decrease with increasing predator abundances, which lag behind those of small mammals. We tested these predictions using data compiled from 6 unpublished and 2 published data sets containing time series (3--11 years) of small mammal and predator community dynamics. Our analyses provide moderate support for the notion that switching trophic control is a unifying phenomenon shaping small mammal assemblages. Also, our results provide evidence that top-down and bottom-up control are not mutually exclusive phenomena driving desert small mammal assemblages but rather alternative ecosystem states that exist along a rainfall-driven continuum of ecosystem energy flux through time. [ABSTRACT FROM AUTHOR]

Solari, A. P., Santamaría, M. T. G., Borges, M. F., Santos, A. M. P., Mendes, H., Balguerías, E., Díaz Cordero, J. A., Castro, J. J., and Bas, C. 2010. On the dynamics of Sardina pilchardus: orbits of stability and environmental forcing. – ICES Journal of Marine Science, 67: 1565–1573.The dynamics of Sardina pilchardus in Iberian upwelling are examined. Spawning-stock biomass (SSB), recruitment (R), and production (R/SSB) data for the years 1978–2006 are analysed in relation to the upwelling index (UPW) and sea surface temperature (SST). The population oscillates in two relatively stable orbits (identified by multiresolution decomposition of the recruitment series) because the external forcing (UPW and SST) are the inverse of each other and the synchrony is lost between the two external variables, R and R/SSB as they shift towards steep, negative (depensatory) trends. Such mechanics may have induced recruitment failures and significant decreases in abundance of Iberian sardine. The relationships are assumed to validate a complex and dynamic continuum (multiple orbits of stability) and an alternative variable-carrying-capacity population model. Radial systems with two orbits of stability are proposed for the R/SSB and S/SSB (where S is the stock size) relationships. Results are discussed in relation to classical and alternative SR models to address stock rehabilitation and fishing mortality issues as the population shifts towards low recruitment and abundance, and critical factors to consider in developing exploitation strategies for systems with multiple orbits of stability are discussed. [ABSTRACT FROM PUBLISHER]

Biogeographical patterns of animal body size and the environmental and evolutionary mechanisms that may be driving them have been broadly investigated in macroecology, although just barely in ectotherms. We separately studied two snake clades, Viperidae and Elapidae, and used phylogenetic eigenvector regression and ordinary least squares multiple regression methods to perform a global grid-based analysis of the extent at which the patterns of body size (measured for each species as its log10-transformed maximum body length) of these groups are phylogenetically structured or driven by current environment trends. Phylogenetic relatedness explained 20% of the across-species size variation in Viperidae, and 59% of that of Elapidae, which is a more recent clade. Conversely, when we analysed spatial trends in mean body size values (calculated for each grid-cell as the average size of its extant species), an environmental model including temperature, precipitation, primary productivity (as indicated by the global vegetation index) and topography (range in elevation) explained 37.6% of the variation of Viperidae, but only 4.5% of that of Elapidae. These contrasted responses of body size patterns to current environment gradients are discussed, taking into consideration the dissimilar evolutionary histories of these closely-related groups. Additionally, the results obtained emphasize the importance of the need to start adopting deconstructive approaches in macroecology. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 98, 94–109. [ABSTRACT FROM AUTHOR]

Using laboratory microcosms, we studied direct and indirect interactions among different components of bi- and tritrophic communities. Filamentous cyanobacteria ( Phormidium sp.) and autotrophic flagellates ( Chlorogonium elongatum) were primary producers. The second trophic level was represented by ciliates Furgasonia blochmanni and Pseudomicrothorax dubius grazing on the filamentous cyanobacteria and two filter feeders, Euplotes octocarinatus and Stylonychia pustulata, feeding on the autotrophic flagellates. An oligochaete, Chaetogaster sp., was used as the top predator. An experiment was carried out for all combinations of two factors: (1) the identity of the cyanobacteria consumer ( Furgasonia or Pseudomicrothorax) and (2) the presence or absence of the top predator. Significant effects of the treatments on both the abundance of cyanobacteria and filter feeding ciliates and predator-induced defense in Phormidium and Euplotes were observed in a 36-day experiment. The experiment showed that the substitution of one species ( Furgasonia) for another ( Pseudomicrothorax) seemingly playing the same ecological role may lead to significant changes in the whole community. [ABSTRACT FROM AUTHOR]

One of the most promising ways to improve the effectiveness of fish farming is the use of phytobiotics in the diet of fish. On this basis, we set the aim to evaluate the effectiveness of the Quercus cortex extract in the concentration of 1 mg/kg on biological features and the productivity of carp. The object of the research was yearling carp grown in the conditions of Orenburgskiy Osetr LLC. Two groups (n = 20) were formed by the method of analogs to conduct the research. After the adaption period (7 days), the groups came to the experimental period (35 days). The feed KRK-110-1 produced by PJSC Orenburg Combined-Feed Plant was used as the basal diet. The live fish were monitored weekly by individual weighing during the accounting period. The elemental composition was determined by the method of atomic emission and mass spectrometry (ICP-AES and ICP-MS). The microflora analysis was carried out by the method of metagenomic sequencing. The use of the Quercus cortex extract in the diet in the studied concentration increased body weight by 15.1% (P = 0.05) compared to the control group. There was experimentally revealed a stimulating effect on the population growth of individual representatives of the microbiome (Luteolibacter, Lactococcus) (P = 0.05) without significantly changing the overall picture of the microbial profile, which, in our view, affects the metabolic processes, in particular, by stimulating the formation of biologically available forms of essential elements and their subsequent accumulation in the tissues of the studied fish. Thus, the experimental group found: (against the background of an increase in the total mineralization (ash residue) by 17.95 % (P = 0.05)) the calcium content increased by 133.9% (P = 0.05), phosphorus by 83% (P = 0.05), iron by 337.7% (P = 0.05), respectively, in comparison with the control group. [ABSTRACT FROM AUTHOR]

Background: Modelling plant growth allows us to test hypotheses and carry out virtual experiments concerning plant growth processes that could otherwise take years in field conditions. The visualization of growth simulations allows us to see directly and vividly the outcome of a given model and provides us with an instructive tool useful for agronomists and foresters, as well as for teaching. Functional–structural (FS) plant growth models are nowadays particularly important for integrating biological processes with environmental conditions in 3-D virtual plants, and provide the basis for more advanced research in plant sciences. [ABSTRACT FROM PUBLISHER]

Aims: Many experiments have shown a positive effect of species richness on productivity in grassland plant communities. However, it is poorly understood how environmental conditions affect this relationship. We aimed to test whether deep soil and limiting nutrient conditions increase the complementarity effect (CE) of species richness due to enhanced potential for resource partitioning. [ABSTRACT FROM PUBLISHER]

We used published data to calculate small-mammal species richness at 43 sites in North America to examine the response of species richness to increasing primary productivity. We estimated species richness for the entire community and for each of 4 functional groups (insectivore, granivore, herbivore, and omnivore). Total richness exhibited a significant unimodal relationship to increasing amounts of annual precipitation and was driven by granivores; this functional group exhibited the most pronounced decline in richness with high precipitation. We suggest that the decline in granivore richness is due to increased litter associated with increased productivity. [ABSTRACT FROM AUTHOR]

The relationship between chlorophyll a (Chl a) and primary productivity (PP) in the uppermost water layer and the water column-based (0–15 m) integral values of those variables were examined using measurements taken in Lake Kinneret (Israel) from 1990 to 2003. In 81% of all Chl a profiles examined, the distribution was fairly uniform within the entire 0–15 m water column, and 12.3% of instances showed a prominent subsurface maximum, when the lake phytoplankton was dominated by the dinoflagellate Peridinium gatunense. Chl a can be reliably estimated by remote sensing techniques in the productive and turbid water of Lake Kinneret, since Chl a concentration at surface layers can be extrapolated to the entire water column. Light vertical attenuation coefficient average for wavelengths from 400 to 700 nm, Kd, ranged from 0.203 to 1.954 m−1 and showed high degree of temporal variation. The maximal rate of photosynthetic efficiency, PBopt [average 3.16 (±1.50)], ranged from 0.25 to 8.85 mg C m−3 h−1 mg Chl a−1. Using measured data of Chl a, PBopt, and light as an input, a simple depth-integrated PP model allowed plausible simulation of PP. However, a lack of correlation between photosynthetic activity and temperature (or other variable with remotely sensed potential) renders the use of models that require input of photosynthetic efficiency to calculate integrated PP of little value in the case of productive and turbid Lake Kinneret. [ABSTRACT FROM AUTHOR]

A seasonal study of dominant protozoa, heterotrophic flagellates and ciliates, was performed along a primary production gradient in the northern Baltic Sea. The abundances of protozoa increased with increasing primary production from north to south. Small cells dominated in the low productive north, while larger cells became more dominant in the south. The highest biovolume concentration of protozoa was observed in summer in the north and during spring in the south. The seasonal succession of protozoa followed a general pattern: choanoflagellates, large flagellates and ciliates showed peaks during spring and autumn, while small bacterivorous nanoflagellates peaked during the summer. An in situ experiment indicated that the inverse relationship between loricated choanoflagellates and other small flagellates may be explained by a seasonal change in the predator community and a seasonal change in the access to surface-attachment sites. Principal component regression analyses including all data showed that 46% of the variation of small flagellates and 20% of the variation of large flagellates could be explained by temperature and bacterial biomass. Ciliates showed a significant relationship to latitude and salinity, explaining 12–24% of the variation. In conclusion, the field data indicated that the protozoan community in general was resource controlled. [ABSTRACT FROM AUTHOR]

The amount of Atlantic water (AW) present on the shelf north of Iceland is highly variable and influences the local biological productivity. Estimates of the volume and heat transports of AW to the North Icelandic Shelf between 1994 and 2000 are presented here. On average, 66% of the eastward flow on the Hornbanki section consists of AW with a transport of AW of approximately 0.75Sv. The associated heat transport is 19TW. There are large interannual variations in the transports, from over 1Sv in the summers of 1997, 1999, and 2000 to almost no AW transport in February/March 1995. The seasonal variation in the transport has an amplitude of 0.2Sv with a minimum in February/March and maximum during late spring and summer. Larval cod are carried by this flow from the main spawning grounds south of Iceland to the nursery grounds on the North Icelandic Shelf. The increasing abundance and the better condition of cod larvae after 1997 are related to the increase of the AW inflow then. [Copyright &y& Elsevier]

Ambiguous legislation, insufficient science, jurisdictional disputes, and conflicting values of stakeholders have contributed to the increasing frequency of natural resource conflicts. The allocation of horseshoe crabs in Delaware Bay and Cape Cod Bay can serve as a model system for understanding resource conflicts, because relationships among biophysical and human systems in this example typify many environmental controversies. Herein, we use an interaction web to build a conceptual framework for identifying potential conflicts. Specifically, we identify four subconflicts involving horseshoe crabs, human shellfishers, commercial fishers, the biomedical industry, birdwatchers, and environmental interest groups. Stakeholders bold different attitudes concerning the horseshoe crab and thus advocate competing policy preferences in the political process. An important step in understanding environmental conflicts is to clarify differences in social meanings, attitudes, and values. The integrated approach described here, by depicting and graphically displaying biosocial relationships, can provide a generalized approach for understanding a broad range of environmental conflicts. [ABSTRACT FROM AUTHOR]

Deep chlorophyll maxima (CM) are commonly observed in the summer stratified North Sea. This feature was studied north of Dogger Bank in August and showed high chlorophyll a (Chl a) concentration (~6 mg m-3) relative to surface waters. Photosynthesis versus irradiance (PvE) relationships were determined and showed the deep chlorophyll maximum accounted for 58% of water column primary productivity with average water column-integrated primary productivity of 424 mg C m-2 day-1. Quantum yield () also showed more favourable phytoplankton growth conditions at the thermocline (mean f = 0.058). Phytoplankton nitrate and ammonium uptake rates were also higher in the deep CM (mean = 0.18 mmol and 0.44 mmol m-3 h-1, respectively) relative to the surface mixed layer (SML) (mean = 0.03 and 0.22 mmol m-3 h-1, respectively). Primary production associated with the maximum was supported in part by nutrient flux from the nutrient rich bottom mixed pool resulting in continuous new production throughout the summer. Using these measurements annual new production associated with the deep chlorophyll maximum was estimated at 37% (5.7 106 t C) of annual new production for the summer stratified North Sea. These subsurface maxima are not detectable using remote sensing and therefore these highly significant regions of production are potentially neglected. [ABSTRACT FROM AUTHOR]

In a mesocosm experiment providing a gradient of semi-continuous addition of mineral nutrient, production rates and mortality of phytoplankton were estimated. Heterotrophic bacterial biomass and production rates and their responses to the mineral nutrients additions were also estimated. The purpose of the experiment was to establish responses of the major biological factors as a function of nutrient amendments. Initial primary production was ∼0.47 µg C L−1 day−1. In the most fertilized mesocosm, phytoplankton biomass increased at a specific rate of 0.4 day−1 during the first week of the experiment, and on day 9 primary production reached a peak at 1027 µg C L−1 day−1. The responses in the other fertilized mesocosms were intermediate, and in an unfertilized control the variables measured stayed almost constant throughout the experiment. The termination of the blooms in the fertilized mesocosms was a consequence of nitrogen limitation, and nitrogen limitation subsequently induced storage of intracellular organic material in the phytoplankton. In the mesocosm receiving the highest daily dose of nutrients, strong post-bloom nutrient limitation resulted in high phytoplankton mortality, and release of organic material from the algae supported the gradient’s highest heterotrophic bacterial production. [ABSTRACT FROM AUTHOR]

Ecologists increasingly recognize the need to understand how landscapes and food webs interact. Reservoir ecosystems are heavily subsidized by nutrients and detritus from surrounding watersheds, and often contain abundant populations of gizzard shad, an omnivorous fish that consumes plankton and detritus. Gizzard shad link terrestrial landscapes and pelagic reservoir food webs by consuming detritus, translocating nutrients from sediment detritus to the water column, and consuming zooplankton. The abundance of gizzard shad increases with watershed agriculturalization, most likely through a variety of mechanisms operating on larval and adult life stages. Gizzard shad have myriad effects on reservoirs, including impacts on nutrients, phytoplankton, zooplankton, and fish, and many of their effects vary with ecosystem productivity (i.e., watershed land use). Interactive feedbacks among watersheds, gizzard shad populations, and reservoir food webs operate to maintain dominance of gizzard shad in highly productive systems. Thus, effective stewardship of reservoir ecosystems must incorporate both watershed and food-web perspectives. [ABSTRACT FROM AUTHOR]

The structure of the zooplankton foodweb and their dominant carbon fluxes were studied in the upwelling system off northern Chile (Mejillones Bay; 23°S) between October 2000 and December 2002. High primary production (PP) rates (1–8 gC m-2 d-1) were mostly due to the net-phytoplankton size fraction (>23 μm). High PP has been traditionally associated with the wind-driven upwelling fertilizing effect of equatorial subsurface waters, which favour development of a short food chain dominated by a few small clupeiform fish species. The objective of the present work was to study the trophic carbon flow through the first step of this “classical chain” (from phytoplankton to primary consumers such as copepods and euphausiids) and the carbon flow towards the gelatinous web composed of both filter-feeding and carnivorous zooplankton. To accomplish this objective, feeding experiments with copepods, appendicularians, ctenophores, and chaetognaths were conducted using naturally occurring plankton prey assemblages. Throughout the study, the total carbon ingestion rates showed that the dominant appendicularian species and small copepods consumed an average of 7 and 5 μgC ind-1 d-1, respectively. In addition, copepods ingested particles mainly in the size range of nano- and microplankton, whereas appendicularians ingested in the range of pico- and nanoplankton. Small copepods and appendicularians removed a small fraction of total daily PP (range 6–11%). However, when the pico- + nanoplankton fractions were the major contributors to total PP (oligotrophic conditions), grazing by small copepods increased markedly to 86% of total PP. Under these more oligotrophic conditions, the euphausiids grazing increased as well, but only reached values lower than 5% of total PP. During this study, chaetognaths and ctenophores ingested an average of 1 and 14 copepods ind-1 d-1, respectively. In terms of biomass consumed, the potential impact of carnivorous gelatinous zooplankton on the small-size copepod community (preferred prey) was important (2–12% of biomass removed daily). However, their impact produced more significant results on copepod abundance (up to 33%), which suggests that carnivorous gelatinous zooplankton may even modulate (control) the abundance of some species as well as the size structure of the copepod community. [Copyright &y& Elsevier]

In this study, we compare rDNA substitution rates for a group of closely related plant species in the western Pacific that exist in different biomes. The results of this comparison indicate higher rates of substitution for species living in habitats with greater biologically available energy. We interpret that finding as potentially important in understanding evolution because of its implication that substitution rate may be a function of biologically available energy and its correlate, productivity. The relevance of this research is twofold. First, contrasting closely related species across different biomes allows for a comparison between rates of molecular evolution across different energetic/ productivity regimes while controlling for phylogenetically influenced variation. Second, the research indicates some of the design parameters for future studies that are required to explore the importance of this relationship among different groups of related organisms. If higher rates of molecular evolution where there is greater available energy are found to be widespread this might bring an additional dimension to the understanding of macroevolutionary pattern and process. [ABSTRACT FROM AUTHOR]

The development of the Daphnia longispina (O. F. Müller) population in a highly humic boreal lake was followed throughout one growing season, and the amount of secondary production was estimated in relation to primary production and available food resources. The growth rate method was applied in the secondary production measurements. Daphnia longispina did not appear in the water column until 16 May, after which the animals were present throughout the growing season. The population showed three density peaks; the first appeared in early June, and the second and third in mid-July and at the beginning of September, respectively. Somatic production followed a seasonal pattern, with highest production rates in midsummer. The maximum value of 127 mg C m–2day–1 was recorded at the beginning of July. The total annual net production of D. longispina was 7.9 g C m–2. During most of the growing season, the primary productivity in the lake was well below 100 mg C m–2 day–1 and the total annual productivity of photosynthetic algae was 5.0 g C m–2. We conclude that in this lake the zooplankton population did not rely on phytoplankton primary production as a sole carbon source, but that most of the carbon must have originated from bacterial production either directly or through a microbial loop. [ABSTRACT FROM PUBLISHER]

An artificial neural network (ANN) model was applied for predicting primary productivity (PP) from a 12 year time series (1985–1996) of monthly observations on a set of environmental and climatic variables from the Gullmar Fjord (south-western Sweden). Results indicate a good fit between observed and predicted PP values. ANN can be regarded as a novel tool for primary production modelling and more generally when the numbers of environmental and climatic co-variates are large. ANN models fitted the data with a lower root mean square error of prediction (RMSEP) than more conventional and classic methods, such as multiple regression. Predictions of future changes in primary production from the same set of input variables using network set-ups with PP leading the input variables by 1, 2 and 3 month lags indicated that RMSEP was about the same as for the case with no lag. These results show the possibility of generating patterns of future fluctuations in primary productivity using ANN. [ABSTRACT FROM PUBLISHER]

By combining weekly data of irradiance, attenuation and chlorophyll a concentrations with photosynthesis (P) versus light intensity (E) curve characteristics, the annual cycle of planktonic primary production in the estuarine part of the Northfrisian Wadden Sea was computed for a 2 year period. Daily water column particulate gross production ranged from 5 to 2200 mg C m–2 day–1 and showed a seasonal pattern similar to chlorophyll a. Budget calculation yielded annual gross particulate primary productions of 124 and 176 g C m–2 year–1 in 1995 and 1996, respectively. Annual amounts of phytoplankton respiration, calculated according to a two-compartment model of Langdon [in Li,W.K.W. and Maestrini,S.Y. (eds), Measurement of Primary Production from the Molecular to the Global Scale. International Council for the Exploration of the Sea, Copenhagen, 1993, pp. 20–36], and dissolved production in 1996, were both in the range of 24–39 g C m–2 year–1. Annual total net production was thus very similar to particulate gross production (127 and 177 g C m–2 year–1 in 1995 and 1996, respectively). Phytoplankton growth was low or even negative in winter. In spring and summer, production/biomass (Pr/B) ratios varied from 0.2 up to 1.7. Phytoplankton growth during the growth season always surpassed average flushing time in the area, thus underlining the potential of local phytoplankton bloom development in this part of the Wadden Sea. The chlorophyll-specific maximum photosynthetic rate (PBmax) ranged from 0.8 to 9.9 mg C mg–1 Chl h–1 and was strongly correlated with water temperature (r2 = 0.67). By contrast, there was no clear seasonal cycle in αB, which ranged from 0.007 to 0.039 mg C mg–1 Chl h–1 (μmol photons m–2 s–1)–1. Its variability was much less than PBmax and independent of temperature. The magnitude and part of the variability of PBmax and αB are presumably caused by changes in species composition, as evidenced from the range of these parameters found among 10 predominant diatom species isolated from the Wadden Sea. The ratio of average light conditions in the water column (Eav) to the light saturation parameter Ek indicates that primary production in the Wadden Sea region under study is predominantly controlled by light limitation and that nutrient limitation was likely to occur for a few hours per day only during 5 (dissolved inorganic nitrogen) to 10 (PO4, Si) weeks in the 2 year period investigated. [ABSTRACT FROM PUBLISHER]

Combined methods of size fractionation and single-cell isolation were used to investigate the seasonal variation of phytoplankton dynamics in Tokyo Bay with an emphasis on primary productivity. Red tides occurred in Tokyo Bay from spring to autumn; a diatom, Skeletonema costatum, and a raphidophycean, Heterosigma akashiwo, were the most important primary producers. Small diatoms and flagellates, including these species, were dominant and showed rapid changes of phytoplankton community structure within several days in summer. The nanoplankton (3–20 μm) fraction contributed most to chlorophyll a concentration and primary productivity during spring to autumn, whereas the microplankton (>20 μm) contribution was remarkable in winter. Picoplankton (<3 μm phytoplankton) remained relatively constant throughout the year. A significant reverse relationship was obtained between assimilation rate and chlorophyll a content for the total and nanoplankton population; the assimilation rate was high at the initial phase of the bloom, then decreased to a minimum level at the peak of the bloom. Factors controlling the reduction of assimilation rates at the peak, and changes in phytoplankton community structure, are discussed. [ABSTRACT FROM PUBLISHER]

Presents information on a study which evaluated the polymorphic evolutionary stable strategy on density dependence and unpredictable selection in a heterogeneous environment. Population genetic models; Predictions on the role of productivity; Two-patch model numerical simulation; Polymorphism of different phenotypes.

The production and metabolism of the amphipod Themisto japonica in Toyama Bay, southern Japan Sea, were estimated based on their biomass and population structure data collected from every 2-week samplings from 1 February 1990 through 30 January 1991 (363 days). Over the sampling period, the mean biomass (B) was 370 mg C m-2. Production (P) was calculated as the sum of somatic (Pg) and molt (Pe) production (P = Pg + Pc), and metabolism (M) as the sum of routine metabolism (Mrtn) and diel vertical migration (Mdvm). Integrating over the entire sampling period, Pg and Pe were 1934 and 176 mg C m-2, respectively, and Mrtn and Mdvm were 4100 and 1778 mg C m-2, respectively. Mean daily P/B and Pg/B ratios were 0.016 and 0.014, respectively, and mean Pg/M and P/M ratios were 0.33 and 0.36 respectively. Assuming assimilation efficiency of 0.904, ingestion was computed as 8837 mg C m-2 per 363 days. For the daily maintenance of growth and metabolism, the T.japonica population needs to ingest an amount of prey which equates to 6.6% of their biomass, or 30% of possible total production of their prey animals (copepods and small euphausiids) in Toyama Bay. [ABSTRACT FROM PUBLISHER]

Primary production, microbial production and the density of planktonic microheterotrophs were estimated at 40 stations in the Okhotsk Sea in July-August 1992 during the seasonal phytoplankton minimum. The primary production by phytoplankton remained rather high even during this minimum. At most stations it was >0.6-0.8 g m-2 day-1, and in leftover patches of spring diatom 'bloom' it reached >5 g C m-2 day-1. The deep maxima of phytoplankton at the upper boundary of the seasonal thermocline were an ordinary phenomenon. The depth of the euphotic zone was normally 30-50 m in the open sea and 12-25 m at the shelf station. Any correlations between the phosphate contents in the upper mixed layer and primary production were absent at the stations. There was no adaptation of the phytoplankton to the light deficiency in deep maxima layers. The total numbers of bacterioplankton were 1-1.5 x 106 ml-1 and its biomass was close to 100 mg m-3 in the open sea. All these numbers were 2-3 times greater at the shelf stations. In deep waters, the bacterioplankton biomass decreased to 10-40 mg m-3. The microbial production in the upper layer was high, at 50-100 mg m-3, decreasing 50-100 times in the deep waters. The numbers of ciliates in the upper water layer varied from 3 to 6 x 103 l-1 and were 1.5-2 times greater than in the shelf areas. Ciliate biomass was 60-100 mg m-3 in the upper mixed layer, and per square metre varied to 1.5-2.5 g. The dominant ciliate taxa belonged to the naked oligotrichid genera Strombidium and Tontonia. Tentative calculations were made of the basin's annual primary production and for the analysis of energy balance in the ecosystem. [ABSTRACT FROM PUBLISHER]

Explains how large mammals affect primary productivity and regulate ecosystem processes in Africa. Explorations of habitat regulation; Regulation of energy flow; Physiochemical processes in savannas; Discussion on the different cycle types; Simulation of grazer effects on nutrient cycling.

Reduced nitrogen species are key nutrients for biological productivity in the oceans. Ammonium is often present in low and growth-limiting concentrations, albeit peaks occur during collapse of algal blooms or via input from deep sea upwelling and riverine inflow. Autotrophic phytoplankton exploit ammonium peaks by storing nitrogen intracellularly. In contrast, the strategy of heterotrophic bacterioplankton to acquire ammonium is less well understood. This study revealed the marine bacterium Phaeobacter inhibens DSM 17395, a Roseobacter group member, to have already depleted the external ammonium when only ∼⅓ of the ultimately attained biomass is formed. This was paralleled by a three-fold increase in cellular nitrogen levels and rapid buildup of various nitrogen-containing intracellular metabolites (and enzymes for their biosynthesis) and biopolymers (DNA, RNA and proteins). Moreover, nitrogen-rich cells secreted potential RTX proteins and the antibiotic tropodithietic acid, perhaps to competitively secure pulses of external ammonium and to protect themselves from predation. This complex response may ensure growing cells and their descendants exclusive provision with internal nitrogen stocks. This nutritional strategy appears prevalent also in other roseobacters from distant geographical provenances and could provide a new perspective on the distribution of reduced nitrogen in marine environments, i.e. temporary accumulation in bacterioplankton cells. [ABSTRACT FROM AUTHOR]

The article reports on the advantages and disadvantages of dichloro-diphenyl-trichloroethane (DDT) when used in any means. According to the author, DDT saves and extends more human lives compared to other man-made chemical substances. In addition to its purpose, DDT is one of the major insecticides used for protecting food crops, although there are cases about the use of DDT by mistake for pancake that led to accidents but no cases of death or serious injury reported. It states that the use of DDT to marshlands may disturb the balance of nature, keeping a species of bird off of the diseases such as malaria, Newcastle and fowlpox. Merely the most important of all, DDT is needed by millions of people living in the "Third World" because it is cheap, safe and residual pesticide.

The objective of this study was to evaluate the environmental, temporal and genetic stability of the relationships between growth and a selection of tree architectural, leaf and phenological traits (selection based on the conclusions of previous studies carried out on the same experimental trial). Therefore, the growth of two hybrid families, Populus deltoides ‘S9-2’ x Populus nigra ‘Ghoy’ (D x N family, 180 F1) and P. deltoides ‘S9-2’ x Populus trichocarpa ‘V24’ (D x T family, 182 F1), was investigated during a 3-year period at two sites, i.e., in northern Italy and central France. At the end of the second growing season, all trees were coppiced and the resprouts were thinned to a single stem. At the end of each growing season, stem circumference and height were measured for all F1 hybrids. The number of sylleptic branches, individual leaf area (LA) and petiole length of the largest leaf along the main stem, production of new leaves, bud flush and bud set were estimated for a selection of genotypes (31 F1) per family at each site during the course of the 3-year experiment. The D x T family was clearly the most productive family and displayed the highest heterosis values. However, there appeared to be a compromise between good growth at a given site and stability between the two different sites, both at family and at genotype levels. Particularly, the less performing trees were stable between Italy and France. Among the studied growth components, the number of sylleptic branches and individual LA of the largest leaf along the main stem were the best growth predictors, irrespective of site and family. Growth strategies in terms of leaf development differed between the two families. Hence, leaf production rate was strongly associated with growth of the D x N family only. These results have important consequences for the use of the studied traits as selection criteria in breeding programmes. [ABSTRACT FROM AUTHOR]

Although interspecific competition has been demonstrated between some pairs of terrestrial gastropod species, little work addresses its importance in tropical assemblages, which are often characterized by high species richness or population densities. A 9-year data set was used to assess growth rates and median shell size of a common Puerto Rican snail, Caracolus caracolla, as a function of density of conspecifics and potential interspecific competitors. Neither the rate nor the magnitude of growth of C. caracolla were inhibited at high densities. No association existed over time between density and size or growth rate. In contrast, C. caracolla generally was largest at sites with high densities of conspecifics. Several factors may be responsible for the apparent unimportance of competition, including the broad, flexible diet of C. caracolla, high productivity of the study site or periodic changes in microclimate or resource availability associated with hurricane-induced disturbance and recovery. [ABSTRACT FROM AUTHOR]

Phytoplankton photosynthetic characteristics in the Kenyan Rift Valley lakes Bogoria, Nakuru and Elmentaita were studied between November 2003 and February 2005. In these world-famous saline–alkaline lake systems, long-term continuous monitoring and photoautotrophic primary productivity modelling have been done for the first time. High light attenuation coefficients were observed with lakes means around 13 m−1 reflecting the huge phytoplankton biomass. No photoinhibition was observed in the primary productivity field measurements. High values of the photosynthesis–irradiance curve initial slope (α) up to 0.85 (mg O2 mg Chl a−1 h−1)(μmol photons m−2 s−1)−1 and a low onset of productivity saturation (Ek) down to 11.4 μmol photons m−2 s−1 as an acclimation to poor light supply were found. For the trophogenic zone, high mean net primary production (NPP) rates of 6.8, 10.7 and 8.5 g O2 m−2 day−1 were recorded for Bogoria, Nakuru and Elmentaita. For the whole water column, NPP decreased to −1.4, 1.6 and 7.2 g O2 m−2 day−1 because of high community respiration. Modelling of the gross primary production (GPP, Chlorophyll a, light supply, initial slope α, maximum production rates considered) gave annual values of 4.9, 6.8 and 4.2 kg O2 m−2 year−1, respectively, for Bogoria, Nakuru and Elmentaita, annual NPP values down to the compensation depth were 70, 65 and 55% of the GPP. [ABSTRACT FROM AUTHOR]

Background and Aims Mat-forming lichens in the genera Stereocaulon and Cladonia have ecosystem-level effects in northern boreal forests. Yet the factors affecting the productivity of mat-forming lichens are not known. The aim of the presented work was to investigate whether mat-forming lichens adapted to low N availability employ N-conserving mechanisms similar to those of vascular plants in nutrient-poor ecosystems. Specifically, the following questions were asked: (a) Do lichens translocate N from basal areas to apical growth areas? (b) Are the quantities of N translocated of ecological significance. (c) Is lichen growth dependent on tissue N concentration [N]. Methods Two different, but complementary, field experiments were conducted using the mat-forming N2-fixing Stereocaulon paschale and non-fixing Cladonia stellaris as model species. First, N translocation was investigated by feeding lichens with Na15NO3 either directly to the apex (theoretical sink) or to the basal part (theoretical source) and observing the redistribution of 15N after a growth period. Secondly, growth and variation in [N] in thalli of different lengths was measured after a growth period. Key Results 15N fed to lower parts of lichen was translocated towards the growing top, but not vice versa, indicating physiologically dependent translocation that follows a sink–source relationship. In the growth experiment where thalli were cut to different lengths, the significant decrease in [N] in apices of short vs. longer thalli after a growth period is consistent with internal relocation as an ecologically important source of N. Conclusions The presented results demonstrate that internal recycling of N occurs in both species investigated and may be ecologically important in these mat-forming lichens under field conditions. The higher nitrogen use efficiency and relative growth rate in C. stellaris in comparison with S. paschale probably enable C. stellaris to dominate the ground cover vegetation in dry boreal coniferous forests under undisturbed conditions. [ABSTRACT FROM AUTHOR]