Producer Nutritional Quality Controls Ecosystem Trophic Structure

Trophic structure, or the distribution of biomass among producers and consumers, determines key ecosystem values, such as the abundance of infectious, harvestable or conservation target species, and the storage and cycling of carbon and nutrients. There has been much debate on what controls ecosystem trophic structure, yet the answer is still elusive. Here we show that the nutritional quality of primary producers controls the trophic structure of ecosystems. By increasing the efficiency of trophic transfer, higher producer nutritional quality results in steeper ecosystem trophic structure, and those changes are more pronounced in terrestrial than in aquatic ecosystems probably due to the more stringent nutritional limitation of terrestrial herbivores. These results explain why ecosystems composed of highly nutritional primary producers feature high consumer productivity, fast energy recycling, and reduced carbon accumulation. Anthropogenic changes in producer nutritional quality, via changes in trophic structure, may alter the values and functions of ecosystems, and those alterations may be more important in terrestrial ecosystems

Nutrient colimitation of primary producer communities

Abstract Synergistic interactions between multiple limiting resources are common, highlighting the importance of co-limitation as a constraint on primary production. Our concept of resource limitation has shifted over the past two decades from an earlier paradigm of single-resource limitation towards concepts of co-limitation by multiple resources, which are predicted by various theories. Herein, we summarise multiple-resource limitation responses in plant communities using a dataset of 641 studies that applied factorial addition of nitrogen (N) and phosphorus (P) in freshwater, marine and terrestrial systems. We found that more than half of the studies displayed some type of synergistic response to N and P addition. We found support for strict definitions of co-limitation in 28% of the studies: i.e. community biomass responded to only combined N and P addition, or to both N and P when added separately. Our results highlight the importance of interactions between N and P in regulating primary producer community biomass and point to the need for future studies that address the multiple mechanisms that could lead to different types of co-limitation

Rutas tróficas en macrozooplancton del Lago de Tota - Boyacá, Colombia

1 recurso en línea (56 páginas) : ilustraciones, figuras, tablas.In aquatic ecosystems inputs of matter and energy present in greater or lesser extent depending on the basin, given the origin and quality of these resources, you can alter the balance in metabolism or interactions in the food web. Using stable isotopes of carbon and nitrogen, the link between potential sources of funds and use established by macrozooplankton species in Lake Big and Lake Fellow the Lake Tota sectors. Trophic possible ways the role of each species in the proposed network, as well. In general, most of this study, most species have a bond with the autotrophic pathway, being the phytoplankton the food resource base for the food web, commonly found impoverished carbon signals. Particularly, the analysis showed a variation in the source or resource for two species (Daphnia laevis and Bosmina (Bosmina) cf. longirostris), with an enrichment in its signal to 19.92 ‰ -20.34 ‰ δ13C, which can be given by plasticity in their food supply, and even if Boeckella gracilis having a signal indicating a specialization in its appeal with carbon impoverished -30 to -26 ‰ values δ13C while nitrogen values are enriched with an average value 20.21 ‰ in δ15N. To set the trophic fractionation means establishing three groups, the first (herbivores) consisting of (D. laevis, B. (Bosmina) and Ceriodaphnia pulchella cf. longirostris), the second (omnivore) which is (Daphnia pulex, Macrocyclops sp. and Cyclopoida), and a third group (secondary consumer) where is the only calanoido B. gracilis. In comparing the temporal variation is observed that there is a significant change in signals δ13C and δ15N of some species in relation to the influence of sources and allochthonous or autochthonous origin, spatial variation was not significant. It is concluded that the macrozooplanton Lake Tota, has a strong link with the autotrophic pathway and pelagic trophic levels have 3 sections, plus the primary producers and the food web in general tends to have an amplitude of trophic niche.En los ecosistemas acuáticos se presentan aportes de materia y energía, en mayor o menor proporción dependiendo de su cuenca, dado el origen y calidad de estos recursos, se puede alterar el balance en el metabolismo o las interacciones en la red trófica. Utilizando los isotopos estables de Carbono y Nitrógeno, se estableció el vínculo entre fuentes potenciales de recursos y el uso por las especies del macrozooplancton en los sectores Lago grande y Lago chico del lago de Tota (Boyacá). Así, se propusieron las posibles vías tróficas y el rol de cada especie en la red. En general, en la mayor parte de este estudio, las especies tuvieron un vínculo marcado con la vía autotrófica, siendo el fitoplancton el recurso alimenticio base para la red trófica, encontrando comúnmente señales empobrecidas de carbono. Particularmente, el análisis mostró una variación en la fuente o recurso para dos especies (Daphnia laevis y Bosmina (Bosmina) cf. longirostris), con un enriquecimiento en su señal de 19.92‰ δ13C a -20.34‰ δ13C, lo que se puede dar por una plasticidad en su fuente alimenticia, e incluso el caso de Boeckella gracilis que tiene una señal que indica una especialización en su recurso con valores empobrecidos de carbono -30 a -26‰ δ13C mientras que los valores de nitrógeno son enriquecidos con un valor promedio de 20.21‰ en δ15N. Para establecer el fraccionamiento trófico medio se formaron tres grupos, el primero (herbívoros) conformado por (D. laevis, B. (Bosmina) cf. longirostris y Ceriodaphnia pulchella), el segundo (omnívoro) en el que se encuentra (Daphnia pulex, Macrocyclops sp. y Cyclopoida), y un tercer grupo (Consumidor secundario) donde esta B. gracilis el único calanoido. En la comparación de la variación temporal, se observa que hay un cambio significativo en las señales de δ13C y δ15N de algunas especies en relación a la influencia de las fuentes y su origen alóctono o autóctono, la variación espacial no fue significativa. Se concluye que el macrozooplanton del lago de Tota, tiene un fuerte vínculo con la vía autotrófica y que los niveles tróficos pelágicos tienen 3 eslabones, más los productores primarios, y la red trófica en general tiende a tener una amplitud del nicho trófico. En los ecosistemas acuáticos se presentan aportes de materia y energía, en mayor o menor proporción dependiendo de su cuenca, dado el origen y calidad de estos recursos, se puede alterar el balance en el metabolismo o las interacciones en la red trófica. Utilizando los isotopos estables de Carbono y Nitrógeno, se estableció el vínculo entre fuentes potenciales de recursos y el uso por las especies del macrozooplancton en los sectores Lago grande y Lago chico del lago de Tota (Boyacá). Así, se propusieron las posibles vías tróficas y el rol de cada especie en la red. En general, en la mayor parte de este estudio, las especies tuvieron un vínculo marcado con la vía autotrófica, siendo el fitoplancton el recurso alimenticio base para la red trófica, encontrando comúnmente señales empobrecidas de carbono. Particularmente, el análisis mostró una variación en la fuente o recurso para dos especies (Daphnia laevis y Bosmina (Bosmina) cf. longirostris), con un enriquecimiento en su señal de 19.92‰ δ13C a -20.34‰ δ13C, lo que se puede dar por una plasticidad en su fuente alimenticia, e incluso el caso de Boeckella gracilis que tiene una señal que indica una especialización en su recurso con valores empobrecidos de carbono -30 a -26‰ δ13C mientras que los valores de nitrógeno son enriquecidos con un valor promedio de 20.21‰ en δ15N. Para establecer el fraccionamiento trófico medio se formaron tres grupos, el primero (herbívoros) conformado por (D. laevis, B. (Bosmina) cf. longirostris y Ceriodaphnia pulchella), el segundo (omnívoro) en el que se encuentra (Daphnia pulex, Macrocyclops sp. y Cyclopoida), y un tercer grupo (Consumidor secundario) donde esta B. gracilis el único calanoido. En la comparación de la variación temporal, se observa que hay un cambio significativo en las señales de δ13C y δ15N de algunas especies en relación a la influencia de las fuentes y su origen alóctono o autóctono, la variación espacial no fue significativa. Se concluye que el macrozooplanton del lago de Tota, tiene un fuerte vínculo con la vía autotrófica y que los niveles tróficos pelágicos tienen 3 eslabones, más los productores primarios, y la red trófica en general tiende a tener una amplitud del nicho trófico.Bibliografía: páginas 46-56.MaestríaMagíster en Ciencias Biológica

Grazer diversity effects in an eelgrass–epiphyte–microphytobenthos system

The dramatic loss of biodiversity and its consequences for ecosystem processes have been of considerable interest in recent ecological studies. However, the complex and interacting processes influencing diversity effects in multitrophic systems are still poorly understood. We used an experimental eelgrass system to study the effects of changing richness of three consumer species on the biomass, diversity and taxonomic composition of both epiphytic and benthic microalgal assemblages. After 1 week, consumer richness enhanced the grazing impact on epiphyte biomass relative to single consumer treatments and a positive effect of consumer richness on prey diversity was found. Moreover, strong effects of consumer species identity on taxonomic composition were found in both microalgal assemblages. However, the effects of consumer richness were not consistent over time. The consequences of high nutrient availability seemed to have masked consumer richness effects

Invasions and Extinctions Reshape Coastal Marine Food Webs

The biodiversity of ecosystems worldwide is changing because of species loss due to human-caused extinctions and species gain through intentional and accidental introductions. Here we show that the combined effect of these two processes is altering the trophic structure of food webs in coastal marine systems. This is because most extinctions (∼70%) occur at high trophic levels (top predators and other carnivores), while most invasions are by species from lower trophic levels (70% macroplanktivores, deposit feeders, and detritivores). These opposing changes thus alter the shape of marine food webs from a trophic pyramid capped by a diverse array of predators and consumers to a shorter, squatter configuration dominated by filter feeders and scavengers. The consequences of the simultaneous loss of diversity at top trophic levels and gain at lower trophic levels is largely unknown. However, current research suggests that a better understanding of how such simultaneous changes in diversity can impact ecosystem function will be required to manage coastal ecosystems and forecast future changes

Combined Tumor Cell-Based Vaccination and Interleukin-12 Gene Therapy Polarizes the Tumor Microenvironment in Mice

Tumor progression depends on tumor milieu, which influences neovasculature formation and immunosuppression. Combining immunotherapy with antiangiogenic/antivascular therapy might be an effective therapeutic approach. The aim of our study was to elaborate an anticancer therapeutic strategy based on the induction of immune response which leads to polarization of tumor milieu. To achieve this, we developed a tumor cell-based vaccine. CAMEL peptide was used as a B16-F10 cell death-inducing agent. The lysates were used as a vaccine to immunize mice bearing B16-F10 melanoma tumors. To further improve the therapeutic effect of the vaccine, we combined it with interleukin (IL)-12 gene therapy. IL-12, a cytokine with antiangiogenic properties, activates nonspecific and specific immune responses. We observed that combined therapy is significantly more effective (as compared with monotherapies) in inhibiting tumor growth. Furthermore, the tested combination polarizes the tumor microenvironment, which results in a switch from a proangiogenic/immunosuppressive to an antiangiogenic/immunostimulatory one. The switch manifests itself as a decreased number of tumor blood vessels, increased levels of tumor-infiltrating CD4+, CD8+ and NK cells, as well as lower level of suppressor lymphocytes (Treg). Our results suggest that polarizing tumor milieu by such combined therapy does inhibit tumor growth and seems to be a promising therapeutic strategy

RhoE Is Regulated by Cyclic AMP and Promotes Fusion of Human BeWo Choriocarcinoma Cells

Fusion of placental villous cytotrophoblasts with the overlying syncytiotrophoblast is essential for the maintenance of successful pregnancy, and disturbances in this process have been implicated in pathological conditions such as pre-eclampsia and intra-uterine growth retardation. In this study we examined the role of the Rho GTPase family member RhoE in trophoblast differentiation and fusion using the BeWo choriocarcinoma cell line, a model of villous cytotrophoblast fusion. Treatment of BeWo cells with the cell permeable cyclic AMP analogue dibutyryl cyclic AMP (dbcAMP) resulted in a strong upregulation of RhoE at 24h, coinciding with the onset of fusion. Using the protein kinase A (PKA)-specific cAMP analogue N6-phenyl-cAMP, and a specific inhibitor of PKA (14–22 amide, PKI), we found that upregulation of RhoE by cAMP was mediated through activation of PKA signalling. Silencing of RhoE expression by RNA interference resulted in a significant decrease in dbcAMP-induced fusion. However, expression of differentiation markers human chorionic gonadotrophin and placental alkaline phosphatase was unaffected by RhoE silencing. Finally, we found that RhoE upregulation by dbcAMP was significantly reduced under hypoxic conditions in which cell fusion is impaired. These results show that induction of RhoE by cAMP is mediated through PKA and promotes BeWo cell fusion but has no effect on functional differentiation, supporting evidence that these two processes may be controlled by separate or diverging pathways

Adoptive T-cell therapy improves treatment of canine non–Hodgkin lymphoma post chemotherapy

Clinical observations reveal that an augmented pace of T-cell recovery after chemotherapy correlates with improved tumor-free survival, suggesting the add-back of T cells after chemotherapy may improve outcomes. To evaluate adoptive immunotherapy treatment for B-lineage non-Hodgkin lymphoma (NHL), we expanded T cells from client-owned canines diagnosed with NHL on artificial antigen presenting cells (aAPC) in the presence of human interleukin (IL)-2 and IL-21. Graded doses of autologous T cells were infused after CHOP chemotherapy and persisted for 49 days, homed to tumor, and significantly improved survival. Serum thymidine kinase changes predicted T-cell engraftment, while anti-tumor effects correlated with neutrophil-to-lymphocyte ratios and granzyme B expression in manufactured T cells. Therefore, chemotherapy can be used to modulate infused T-cell responses to enhance anti-tumor effects. The companion canine model has translational implications for human immunotherapy which can be readily exploited since clinical-grade canine and human T cells are propagated using identical approaches

Characteristics of the Alternative Phenotype of Microglia/Macrophages and its Modulation in Experimental Gliomas

Microglia (brain resident macrophages) accumulate in malignant gliomas and instead of initiating the anti-tumor response, they switch to a pro-invasive phenotype, support tumor growth, invasion, angiogenesis and immunosuppression by release of cytokines/chemokines and extracellular matrix proteases. Using immunofluorescence and flow cytometry, we demonstrate an early accumulation of activated microglia followed by accumulation of macrophages in experimental murine EGFP-GL261 gliomas. Those cells acquire the alternative phenotype, as evidenced by evaluation of the production of ten pro/anti-inflammatory cytokines and expression profiling of 28 genes in magnetically-sorted CD11b+ cells from tumor tissues. Furthermore, we show that infiltration of implanted gliomas by amoeboid, Iba1-positive cells can be reduced by a systematically injected cyclosporine A (CsA) two or eight days after cell inoculation. The up-regulated levels of IL-10 and GM-CSF, increased expression of genes characteristic for the alternative and pro-invasive phenotype (arg-1, mt1-mmp, cxcl14) in glioma-derived CD11b+ cells as well as enhanced angiogenesis and tumor growth were reduced in CsA-treated mice. Our findings define for the first time kinetics and biochemical characteristics of glioma-infiltrating microglia/macrophages. Inhibition of the alternative activation of tumor-infiltrating macrophages significantly reduced tumor growth. Thus, blockade of microglia/macrophage infiltration and their pro-invasive functions could be a novel therapeutic strategy in malignant gliomas