Functional Group Level Research Articles

Rhodium(III)-Catalyzed Oxidative Cross-Coupling of Unreactive C(sp3)-H Bonds with C(sp2)-H Bonds.

The development of the oxidative cross-coupling of unreactive C(sp3)-H bonds with (hetero)arene C(sp2)-H bonds is considerably appealing, yet conceptually and practically challenging. Here, we disclose the rhodium-catalyzed oxidative heteroarylation of unactivated C(sp3)-H bonds with heteroarene C(sp2)-H bonds. This method provides a step-economic route to β-heteroarylated 2-ethylpyridine derivatives, which exhibits relatively broad substrate scope, high tolerance level of sensitive functional groups, and high selectivity. The protocol can also be extended to the coupling reaction between 8-methylquinoline derivatives and heteroarenes.

Unfavorable regions in the ramachandran plot: Is it really steric hindrance? The interacting quantum atoms perspective.

Accurate description of the intrinsic preferences of amino acids is important to consider when developing a biomolecular force field. In this study, we use a modern energy partitioning approach called Interacting Quantum Atoms to inspect the cause of the φ and ψ torsional preferences of three dipeptides (Gly, Val, and Ile). Repeating energy trends at each of the molecular, functional group, and atomic levels are observed across both (1) the three amino acids and (2) the φ/ψ scans in Ramachandran plots. At the molecular level, it is surprisingly electrostatic destabilization that causes the high‐energy regions in the Ramachandran plot, not molecular steric hindrance (related to the intra‐atomic energy). At the functional group and atomic levels, the importance of key peptide atoms (Oi –1, Ci, Ni, Ni +1) and some sidechain hydrogen atoms (Hγ) are identified as responsible for the destabilization seen in the energetically disfavored Ramachandran regions. Consistently, the Oi –1 atoms are particularly important for the explanation of dipeptide intrinsic behavior, where electrostatic and steric destabilization unusually complement one another. The findings suggest that, at least for these dipeptides, it is the peptide group atoms that dominate the intrinsic behavior, more so than the sidechain atoms. © 2017 The Authors. Journal of Computational Chemistry Published by Wiley Periodicals, Inc.

Microbial community structure and activity in trace element-contaminated soils phytomanaged by Gentle Remediation Options (GRO)

Gentle remediation options (GRO) are based on the combined use of plants, associated microorganisms and soil amendments, which can potentially restore soil functions and quality. We studied the effects of three GRO (aided-phytostabilisation, in situ stabilisation and phytoexclusion, and aided-phytoextraction) on the soil microbial biomass and respiration, the activities of hydrolase enzymes involved in the biogeochemical cycles of C, N, P, and S, and bacterial community structure of trace element contaminated soils (TECS) from six field trials across Europe. Community structure was studied using denaturing gradient gel electrophoresis (DGGE) fingerprinting of Bacteria, α- and β-Proteobacteria, Actinobacteria and Streptomycetaceae, and sequencing of DGGE bands characteristic of specific treatments. The number of copies of genes involved in ammonia oxidation and denitrification were determined by qPCR.Phytomanagement increased soil microbial biomass at three sites and respiration at the Biogeco site (France). Enzyme activities were consistently higher in treated soils compared to untreated soils at the Biogeco site. At this site, microbial biomass increased from 696 to 2352 mg ATP kg−1 soil, respiration increased from 7.4 to 40.1 mg C-CO2 kg−1 soil d−1, and enzyme activities were 2–11-fold higher in treated soils compared to untreated soil. Phytomanagement induced shifts in the bacterial community structure at both, the total community and functional group levels, and generally increased the number of copies of genes involved in the N cycle (nirK, nirS, nosZ, and amoA). The influence of the main soil physico-chemical properties and trace element availability were assessed and eventual site-specific effects elucidated. Overall, our results demonstrate that phytomanagement of TECS influences soil biological activity in the long term.

Complementary online aerosol mass spectrometry and offline FT-IR spectroscopy measurements: Prospects and challenges for the analysis of anthropogenic aerosol particle emissions

The aerosol mass spectrometer (AMS) is well established in investigating highly time-resolved dynamics of submicron aerosol chemical composition including organic aerosol (OA). However, interpretation of mass spectra on molecular level is limited due to strong fragmentation of organic substances and potential reactions inside the AMS ion chamber. Results from complementary filter-based FT-IR absorption measurements were used to explain features in high-resolution AMS mass spectra of different types of OA (e.g. cooking OA, cigarette smoking OA, wood burning OA). Using this approach some AMS fragment ions were validated in this study as appropriate and rather specific markers for a certain class of organic compounds for all particle types under investigation. These markers can therefore be used to get deeper insights in the chemical composition of OA based on AMS mass spectra in upcoming studies. However, the specificity of other fragment ions such as C2H4O2+ (m/z 60.02114) remains ambiguous. In such cases, complementary FT-IR measurements allow the interpretation of highly time-resolved AMS mass spectra at the level of molecular functional groups. Furthermore, this study discusses the challenges in reducing inorganic interferences (e.g. from water and ammonium salts) in FT-IR spectra of atmospheric aerosols to decrease spectral uncertainties for better comparisons and, thus, to get more robust results.

Efectos de la fertilización del suelo sobre el crecimiento arbóreo en bosques pluviales tropicales del Chocó, Colombia

The tree diameter growth (CDA) is a fundamental component of net primary productivity (NPP) and carbon storage in forest ecosystems; therefore, it plays a key role in mitigating global climate change. It has been hypothesized that CDA in lowland tropical rain forests is limited by the availability of soil nutrients, yet little experimental evidence is available, especially in forest of high precipitation (>5 000 mm per year). This study evaluated the effects of soil fertilization on CDA in tropical rainforests of the Colombian Pacific, one of the wettest areas of the world. Such effects were assessed at the level of localities, diametric categories, wood density, and functional groups. To do this, two arboreal inventories (2014 and 2015) were performed, five fertilization treatments (Nitrogen-N, Phosphorus-P, Potassium-K, NPK and Control) were applied, and the CDA was determined in five permanent plots of one hectare. We found that the application of N and NPK had little effect on CDA as compared to the control; while the addition of P and K produced significant reduction of the trees relative growth rate, with respect to the control at the level of localities, in small and medium sized trees, in all wood densities (low, medium and high), and in the group of dicotyledonous species. Although these results did not corroborate the hypothesis of nutrient limitation on CDA in the studied forests, it was found that during the early years of fertilization (mainly with P and K), different patterns of aboveground and belowground NPP occurred to maximize photosynthesis and soil nutrient acquisition.

Effects of soil fertilization on tree growth in tropical rainforests of Choco, Colombia.

The tree diameter growth (CDA) is a fundamental component of net primary productivity (NPP) and carbon storage in forest ecosystems; therefore, it plays a key role in mitigating global climate change. It has been hypothesized that CDA in lowland tropical rain forests is limited by the availability of soil nutrients, yet little experimental evidence is available, especially in forest of high precipitation (>5 000 mm per year). This study evaluated the effects of soil fertilization on CDA in tropical rainforests of the Colombian Pacific, one of the wettest areas of the world. Such effects were assessed at the level of localities, diametric categories, wood density, and functional groups. To do this, two arboreal inventories (2014 and 2015) were performed, five fertilization treatments (Nitrogen-N, Phosphorus-P, Potassium-K, NPK and Control) were applied, and the CDA was determined in five permanent plots of one hectare. We found that the application of N and NPK had little effect on CDA as compared to the control; while the addition of P and K produced significant reduction of the trees relative growth rate, with respect to the control at the level of localities, in small and medium sized trees, in all wood densities (low, medium and high), and in the group of dicotyledonous species. Although these results did not corroborate the hypothesis of nutrient limitation on CDA in the studied forests, it was found that during the early years of fertilization (mainly with P and K), different patterns of aboveground and belowground NPP occurred to maximize photosynthesis and soil nutrient acquisition.

Coordinated responses of soil communities to elevation in three subarctic vegetation types

Global warming has begun to have a major impact on the species composition and functioning of plant and soil communities. However, long‐term community and ecosystem responses to increased temperature are still poorly understood. In this study, we used a well‐established elevational gradient in northern Sweden to elucidate how plant, microbial and nematode communities shift with elevation and associated changes in temperature in three highly contrasting vegetation types (i.e. heath, meadow and Salix vegetation). We found that responses of both the abundance and composition of microbial and nematode communities to elevation differed greatly among the vegetation types. Within vegetation types, changes with elevation of plant, microbial and nematode communities were mostly linked at fine levels of taxonomic resolution, but this pattern disappeared when coarser functional group levels were considered. Further, nematode communities shifted towards more conservative nutrient cycling strategies with increasing elevation in heath and meadow vegetation. Conversely, in Salix vegetation microbial communities with conservative strategies were most pronounced at the mid‐elevation. These results provide limited support for increasing conservative nutrient cycling strategies at higher elevation (i.e. with a harsher climate). Our findings indicate that climate‐induced changes in plant community composition may greatly modify or counteract the impact of climate change on soil communities. Therefore, to better understand and predict ecosystem responses to climate change, it will be crucial to consider vegetation type and its specific interactions with soil communities.

Evolution mechanism of oxygen functional groups during pyrolysis of Datong coal

The chemical structure and evolution mechanism of organic oxygen functional groups in Datong coal during pyrolysis were investigated in this paper. Firstly, qualitative and quantitative analyses to groups in Datong coal were achieved by Fourier transform infrared spectrometer. The results indicate that oxygen functional groups in this coal include hydroxyl, carboxyl, carbonyl group, and ether. Higher levels of oxygen functional groups and aromatic structures as well as low content of fat structure were found in Datong coal by peak fitting. Secondly, the main chemical reactions and effects during the pyrolysis of coal are described. Then, the evolution of the chemical structure and transformation mechanism of oxygen functional groups in Datong coal were represented and analyzed by wet chemical analysis. The analysis reveals that aromatic structures were heated and decomposed, oxygen was adsorbed, and then the phenolic hydroxyl groups were formed. When the temperature reaches 300 °C or higher, aromatic rings in phenolic hydroxyl were cracked and the carboxyl group was generated. The main purpose of this paper is to study the influence of temperature on the group types and their content in coal, and further to explain the evolution mechanism of the oxygen functional groups in the process of coal pyrolysis.

Polar Dynamics at a Functional Group Level: Infrared‐Visible Sum‐Frequency Generation Study on Polar Columnar Liquid Crystals

Organic ferroelectrics (OFEs) are an attractive topic in material science because of their usefulness in modern technologies. There are a variety of OFEs that have been developed through various approaches using various materials. To further design and understand OFEs, it is essentially important to evaluate the dynamical behaviors of individual molecules during polarization switching. Although recent developments in theoretical calculations offer powerful tools to predict how molecules assemble into complex structures at the molecular level, it is still too difficult to determine the dynamics in response to external stimuli at the functional group level. Here, this study adopts infrared‐visible sum‐frequency generation (IV‐SFG) to probe the electric‐field‐induced dynamics at the functional group level and reports on the switching mechanism of the bulk ferroelectricity and paraelectricity in an organic system for the first time. This paper demonstrates an IV‐SFG study on a recently‐discovered polar columnar liquid crystal system of tapered‐paraffinic‐wedge molecules, whose favorable wet‐processability may provide a suitable design for “paintable” organic ferroelectrics. Dynamic motions of dipoles, such as of phthalonitriles and amides, are successfully probed. In ferroelectric compounds, the phthalonitriles are responsible both for the ferroelectric and paraelectric switching, whereas the amides only for the ferroelectric switching.

Studying mesoalgal structures: a non-destructive approach based on confocal laser scanning microscopy

AbstractMesoalgae play a key role in shallow coastal ecosystems. Composed of small macroalgae, intermixed with filamentous cyanobacteria and colonial diatoms, these multi-specific, but minute (μm–cm) assemblages form complex three-dimensional structures, providing shelter for different unicellular (e.g. bacteria, diatoms, dinoflagellates) and multicellular (e.g. fishes, invertebrates) organisms. Characterized by a high colonization potential, these primary producers are observed to bloom and overgrow disturbed areas (e.g. damaged coral reefs, urchin barrens), and play a crucial role in terms of invasion and colonizing new habitats. Driven by anthropogenic environmental changes, mesoalgae are receiving considerable attention in current marine research. So far, most studies approach mesoalgae at the functional group level (e.g. turf algae, microphytobenthos), whereas only few studies tackle the importance of species-specific interactions, which play an important role in benthic ecology (e.g. coral-algal competition and disease spreading). To facilitate the study of not only the presence but also the composition and the structure of these habitat formers, we provide a new approach combining inexpensive fixation methodology with modern confocal laser scanning microscopy (CLSM), to study minute macroalgal structures (e.g. germlings, reproductive structures), and investigate their relation to microphytobenthic components (e.g. diatom colonies). Detailed procedures for mounting, staining and imaging phytobenthic communities are provided.

Ecology under lake ice.

Winter conditions are rapidly changing in temperate ecosystems, particularly for those that experience periods of snow and ice cover. Relatively little is known of winter ecology in these systems, due to a historical research focus on summer 'growing seasons'. We executed the first global quantitative synthesis on under-ice lake ecology, including 36 abiotic and biotic variables from 42 research groups and 101 lakes, examining seasonal differences and connections as well as how seasonal differences vary with geophysical factors. Plankton were more abundant under ice than expected; mean winter values were 43.2% of summer values for chlorophyll a, 15.8% of summer phytoplankton biovolume and 25.3% of summer zooplankton density. Dissolved nitrogen concentrations were typically higher during winter, and these differences were exaggerated in smaller lakes. Lake size also influenced winter-summer patterns for dissolved organic carbon (DOC), with higher winter DOC in smaller lakes. At coarse levels of taxonomic aggregation, phytoplankton and zooplankton community composition showed few systematic differences between seasons, although literature suggests that seasonal differences are frequently lake-specific, species-specific, or occur at the level of functional group. Within the subset of lakes that had longer time series, winter influenced the subsequent summer for some nutrient variables and zooplankton biomass.

Effect of exhaust gas recirculation (EGR) and multiple injections on diesel soot nano-structure and reactivity

The physio-chemical characteristics of soot particles are of importance with regard to performance of diesel after-treatment systems. In this study, the soot particles generated in a single-cylinder heavy-duty diesel engine are examined in terms of nanostructure, oxidative reactivity and volatile organic fraction (VOF), using thermogravimetric analysis (TGA), X-ray diffraction (XRD), Raman micro-spectroscopy, and high resolution transmission electron microscopy (HRTEM). Five different injection strategies including single injection and multiple injections with various pilot injection amounts and dwell times were tested with and without exhaust gas recirculation (EGR), while combustion phasing, engine speed, and fuel injection quantity was matched for all cases. Results indicate that for the soot produced under EGR condition, nano-structural order (indicated by crystallite size obtained from XRD and AD1/AG resulted from the Raman Analysis) can explain the soot reactivity. However, in the absence of EGR, the reactivity trend cannot be explained by the structural order. It is discussed that a possible reason can be a higher level of in-cylinder oxidation in non-EGR cases (indicated by higher level of surface functional groups) which roughens the soot surface, and enhances the oxidation by increasing the specific soot surface area. It is also found that in the absence of EGR, different injection strategies impact the soot reactivity and VOF content, which can be explained mainly through the level of charge premixed-ness and the in-cylinder soot oxidation, and the consequent effect on the soot surface roughness. Results also show that the influence of injection strategy on the soot reactivity and VOF content tends to vanish as EGR is added.

Identifying drivers of root community compositional changes in semiarid grassland on the Loess plateau after long-term grazing exclusion

Grazing exclusion has been widely studied to have impacts on grassland aboveground community characteristics, however little is known about responses of grassland root community to long-term grazing exclusion. We selected five grasslands with different grazing exclusion time (0, 5 years, 9 years, 22 years, and 30 years) to determine root traits (biomass, length, surface area) in plant functional group and plant community level, soil properties of 0–30cm depth and relationship between root traits and soil properties. Our results showed that grazing exclusion increased grassland root biomass, root length density and root surface area, accompanying declined plant species richness. After grazing exclusion, with perennial bunchgrasses (PB) being predominant in root community all the time, proportion of perennial rhizome grasses (PR) increased and proportion of perennial forbs (PF) declined. Grasses had higher specific root length and specific root surface area than that of forbs. Grazing exclusion significantly increased soil water content, soil organic carbon, total soil nitrogen and available soil phosphorus. Grasses were mainly correlated with soil organic carbon and nitrogen, while forbs were mainly influenced by soil phosphorus. Our results highlight the grasses’ enhancing effect on grassland root productivity, and the critical role of soil nitrogen and phosphorus in regulating root community compositional changes in semiarid grassland after long-term grazing exclusion.

Distribution of mesopredatory fish determined by habitat variables in a predator-depleted coastal system.

Shallow nearshore habitats are highly valued for supporting marine ecosystems, but are subject to intense human-induced pressures. Mesopredatory fish are key components in coastal food webs, and alterations in their abundance may have evident effects also on other parts of the ecosystem. The aim of this study was to clarify the relationship between the abundance of coastal mesopredatory fish, defined as mid-trophic level demersal and benthic species with a diet consisting predominantly of invertebrates, and ambient environmental variables in a fjord system influenced by both eutrophication and overfishing. A field survey was conducted over a coastal gradient comprising 300 data points sampled consistently for fish community and environmental data. Results from multivariate and univariate analyses supported each other, demonstrating that mesopredatory fish abundance at species and functional group level was positively related to the cover of structurally complex vegetation and negatively related to eutrophication, as measured by water transparency. Contrary to other studies showing an inverse relationship to piscivore abundance over time, the spatial distribution of mesopredatory fish was not locally regulated by the abundance of piscivorous fish, probably attributed to piscivores being at historically low levels due to previous overfishing. Mesopredatory fish abundance was highest in areas with high habitat quality and positively related to the abundance of piscivores, suggesting a predominance of bottom-up processes. We conclude that, in parallel with ongoing regulations of fishing pressure, measures to restore habitat function and food web productivity are important for the recovery of coastal fish communities in the area.Electronic supplementary materialThe online version of this article (doi:10.1007/s00227-016-2977-9) contains supplementary material, which is available to authorized users.

Identifying the Sources and Sinks of CDOM/FDOM across the Mauritanian Shelf and Their Potential Role in the Decomposition of Superoxide (O2-)

Superoxide (O2-) is a short lived reactive oxygen species (ROS) formed in seawater by photochemical or biological sources, it is important in the redox cycling of trace elements and organic matter in the ocean. The photoproduction of O2- is now thought to involve reactions between O2 and reactive reducing (radical) intermediates formed from dissolved organic matter (DOM) via intramolecular reactions between excited singlet state donors and ground-state acceptors (Zhang et al., 2012). In seawater the main pathways identified for the decomposition of O2- into H2O2 and O2, involve reactions with Cu, Mn and DOM. In productive regions of the ocean, the reaction between DOM and O2- can be a significant sink for O2-. Thus DOM is a key component of both the formation and decomposition of O2- and formation of H2O2. In the present work we examined the relationships between O2- decay rates and parameters associated with chromophoric dissolved organic matter (CDOM) and fluorescent dissolved organic matter (FDOM) by using the thermal O2- source SOTS-1. Filtered samples (0.2 µm) were run both in the presence, and absence, of the metal chelator diethylenetriaminepentaacetic acid (DTPA) to determine the contribution from DOM. Samples were collected along a transect across the continental shelf of the Mauritanian continental shelf during a period of upwelling. In this region we found that reactions with DOM, are a significant sink for O2- in the Mauritanian Upwelling, constituting on average 58 ± 13 % of the O2- loss rates. Superoxide reactivity with organic matter showed no clear correlation with bulk CDOM or FDOM properties (as assessed by PARAFAC analysis) suggesting that future work should concentrate at the functional group level to clearly elucidate which molecular species are involved as bulk properties represent a wide spread of chemical moieties with different O2- reactivities. Analysis of FDOM parameters indicates that many of the markers used previously for terrestrial sources of DOM and FDOM are called into question as marine sources exist. In particular recent work (Rico et al., 2013) indicates that algal species may also produce syringic, vanillic and cinnamic acids, which had previously been ascribed solely to terrestrial vegetation.

Comparing microscopic counts and pigment analyses in 46 phytoplankton communities from lakes of different trophic state

Summary Comparison between algal pigment analyses using HPLC and subsequent CHEMTAX analysis with microscopic counts from different lakes ranging from ultra‐oligotrophic to eutrophic allowed testing of pigment:chlorophyll a ratios for lakes of different trophic conditions. Microscopic counts and pigment analyses were positively correlated for all groups except for the chrysophytes. When examining the oligotrophic lakes only, microscopic analyses and pigment analyses of chrysophytes were positively correlated, which showed that the oligotrophic pigment ratios were well suited for determining the abundance of the chrysophytes in oligotrophic lakes. In the eutrophic lakes, where chrysophytes constituted less than 10% of the biomass, the weak correlation was most likely related to counting inaccuracies. Chrysophytes, generally indicative of oligotrophic conditions, were three times more abundant in the oligotrophic lakes. They constituted 28% of the total phytoplankton biomass as chlorophyll a measured by the pigment method and 26% of the total phytoplankton biomass measured as biovolume by microscopy. In mesotrophic/eutrophic lakes, chrysophytes constituted only 9% (pigment method) and 8% (microscopy). Similarity analyses comparing the results of these two methods on functional group level documented the high accuracy of the pigment method in detecting all the functional groups present. The results of the pigment analyses showed a more even composition of phytoplankton groups than found by microscopy, where often one or two of the less abundant groups were absent or only sporadically present. The Shannon's diversity index, H’, for functional groups determined from results of the pigment method were higher than the H’ values based on microscopic counts, confirming a more continuous composition of the phytoplankton groups when detected by the pigment method. The pigment method was found to be a useful alternative, which supplemented microscopic counts.

Plant-pollinator interactions in a biodiverse meadow are rather stable and tight for 3 consecutive years.

Plant-pollinator interactions can be highly variable across years in natural communities. Although variation in the species composition and its basic structure has been investigated to understand the dynamic nature of pollination networks, little is known about the temporal dynamic of interaction strength between the same plant and pollinator species in any natural community. Pollinator-mediated selection on the evolution of floral traits could be diminished if plant-pollinator interactions vary temporally. To quantify the temporal variation in plant-pollinator interactions and the interaction strength (observed visits), we compared weighted networks between plants and pollinators in a biodiverse alpine meadow in Shangri-La, southwest China for 3 consecutive years. Although plant-pollinator interactions were highly dynamic such that identical interactions only accounted for 10.7% of the total between pair years, the diversity of interactions was stable. These identical interactions contributed 41.2% of total visits and were similar in strength and weighted nestedness. For plant species, 72.6% of species were visited by identical pollinator species between pair years, accounting for over half of the total visits and three-quarters at the functional group level. More generalized pollinators contributed more connectiveness and were more central in networks across years. However, there was no similar or even opposite trend for plant species, which suggested that specialized plant species may also be central in pollinator networks. The variation in pollinator composition decreased as pollinator species numbers increased, suggesting that generalized plants experienced stable pollinator partition. The stable, tight interactions between generalized pollinators and specialized plants represent cornerstones of the studied community.

Selective Oxidation of Glycerol to Glyceric Acid in Base‐Free Aqueous Solution at Room Temperature Catalyzed by Platinum Supported on Carbon Activated with Potassium Hydroxide

AbstractPt supported on KOH‐activated mesoporous carbon (K‐AMC) was used to catalyze glycerol oxidation under base‐free conditions at room temperature. To study the relationship between the carbon surface chemistry and the catalytic performance of the K‐AMC‐based Pt catalysts, different levels of surface oxygen functional groups (SOFGs) on the AMC supports were induced by thermal treatment at different temperatures under inert or H2 gas. A strong effect of the surface chemistry was observed on AMC‐supported Pt catalysts for glycerol oxidation. The presence of carboxylic acid groups impedes the adsorption of glycerol, which leads to the reduction of catalytic activity, whereas the presence of high‐desorption‐temperature SOFGs, such as phenol, ether, and carbonyl/quinone groups, provide hydrophilicity to the carbon surface that improves the adsorption of glycerol molecules on Pt metal surface, which is beneficial for the catalytic activity.

Progression of a Gulf of Mexico food web supporting Atlantis ecosystem model development

This article develops a marine food web matrix for the Gulf of Mexico (GOM) based on local stomach sampling and online diet information. Working at the level of functional groups, we fit diet information to a statistical model based on the Dirichlet distribution. This allows us to quantify likely contributions of prey to predators’ diets. Error ranges on these values reflect diet variability and data quality, and help in identifying functional groups that would benefit from additional sampling. We perform hierarchical cluster analysis to determine functional groups that have similar prey requirements, then produce a food web diagram representing the interactions between predators and prey. A meta-analysis using principle coordinate analysis allows us to compare this study’s diet matrix with ten other published GOM food webs and determine where variation in food web structure exists. We also compare our new food web to the diet matrix used by the Ainsworth et al. (2015) Atlantis ecosystem model, a strategic tool developed to assess ecosystem dynamics in the GOM. A hindcast from 1980 to 2010 using Atlantis shows an improved fit to observational data and reduced error in biomass projections using the revised diet information.

Ecological equivalence of species within phytoplankton functional groups

Summary There are tens of thousands of species of phytoplankton found throughout the tree of life. Despite this diversity, phytoplankton are often aggregated into a few functional groups according to metabolic traits or biogeochemical role. We investigate the extent to which phytoplankton species dynamics are neutral within functional groups. Seasonal dynamics in many regions of the ocean are known to affect phytoplankton at the functional group level leading to largely predictable patterns of seasonal succession. It is much more difficult to make general statements about the dynamics of individual species. We use a 7‐year time series at station L4 in the Western English Channel with 57 diatom and 17 dinoflagellate species enumerated weekly to test whether the abundance of diatom and dinoflagellate species varies randomly within their functional group envelope or whether each species is driven uniquely by external factors. We show that the total biomass of the diatom and dinoflagellate functional groups is well predicted by irradiance and temperature and quantify trait values governing the growth rate of both functional groups. The biomass dynamics of the functional groups are not neutral and each has their own distinct responses to environmental forcing. Compared to dinoflagellates, diatoms have faster growth rates and grow faster under lower irradiance, cooler temperatures, and higher nutrient conditions. The biomass of most species varies randomly within their functional group biomass envelope, most of the time. As a consequence, modellers will find it difficult to predict the biomass of most individual species. Our analysis supports the approach of using a single set of traits for a functional group and suggests that it should be possible to determine these traits from natural communities.