Freshwater Phytoplankton Species Research Articles

Broad allelopathic activity in Peridinium aciculiferum (Dinophyceae)

The dinoflagellate Peridinium aciculiferum forms blooms underneath the ice in temperate lakes and has previously been shown to have an allelopathic effect on a natural competitor as well as being haemolytic. Hence, we investigated whether P. aciculiferum is allelopathic towards a wide range of different freshwater phytoplankton species. We also tested the hypothesis that nutrient (N and P) deficiency enhances its allelopathic effect. In addition, we explored how target cell density affected the extent of the allelopathic effect. Our findings showed that P. aciculiferum had a negative effect (mortality through lyses) on Synura petersenii (Chrysophyceae), Peridinium inconspicuum (Dinophyceae), Cyclotella sp. (Bacillariophyceae), Cryptomonas sp. and Rhodomonas lacustris (Cryptophyceae). Only Chlamydomonas reinhardtii (Chlorophyceae) cells were not negatively affected. In semi-continuously grown nutrient deficient cultures, we detected no allelopathic activity, in contrast to the findings for batch cultures. Finally, we found that, at donor–target cell ratios above 6:1, the algicidal effect of P. aciculiferum did not increase. We concluded that the allelopathic activity of P. aciculiferum has a wide span of action due to either a single chemical or a cocktail of allelochemicals, but that allelopathic activity is highly variable depending on growth conditions.

Unveiling fungal zooflagellates as members of freshwater picoeukaryotes: evidence from a molecular diversity study in a deep meromictic lake

This study presents an original 18S rRNA PCR survey of the freshwater picoeukaryote community, and was designed to detect unidentified heterotrophic picoflagellates (size range 0.6-5 microm) which are prevalent throughout the year within the heterotrophic flagellate assemblage in Lake Pavin. Four clone libraries were constructed from samples collected in two contrasting zones in the lake. Computerized statistic tools have suggested that sequence retrieval was representative of the in situ picoplankton diversity. The two sampling zones exhibited similar diversity patterns but shared only about 5% of the operational taxonomic units (OTUs). Phylogenetic analysis clustered our sequences into three taxonomic groups: Alveolates (30% of OTUs), Fungi (23%) and Cercozoa (19%). Fungi thus substantially contributed to the detected diversity, as was additionally supported by direct microscopic observations of fungal zoospores and sporangia. A large fraction of the sequences belonged to parasites, including Alveolate sequences affiliated to the genus Perkinsus known as zooparasites, and chytrids that include host-specific parasitic fungi of various freshwater phytoplankton species, primarily diatoms. Phylogenetic analysis revealed five novel clades that probably include typical freshwater environmental sequences. Overall, from the unsuspected fungal diversity unveiled, we think that fungal zooflagellates have been misidentified as phagotrophic nanoflagellates in previous studies. This is in agreement with a recent experimental demonstration that zoospore-producing fungi and parasitic activity may play an important role in aquatic food webs.

COMPETITION FOR NUTRIENTS AND LIGHT: STABLE COEXISTENCE, ALTERNATIVE STABLE STATES, OR COMPETITIVE EXCLUSION?

Competition theory has put forward three contrasting hypotheses: Compe- tition for nutrients and light may lead to (i) stable coexistence of species, (ii) alternative stable states, or (iii) competitive exclusion. This paper presents a detailed investigation of competition among phytoplankton species to test these three different hypotheses. First, we developed a competition model combining competition for nutrients and light. Next, we ran monoculture experiments in phosphorus-limited and light-limited chemostats to estimate the model parameters for five freshwater phytoplankton species. Finally, we tested the model predictions in competition experiments, using phosphorus levels ranging from oligotrophic to eutrophic conditions. The population dynamics in the competition experi- ments were all in agreement with the model predictions. This demonstrates that competition for nutrients and light can be accurately predicted over a wide range of productivities. The experiments revealed that the intensity of competition remained constant or even decreased with increasing nutrient supply. Contrary to expectation, there were no trade-offs between competitive abilities for phosphorus and light. Species that were strong competitors for phosphorus were strong competitors for light as well. Hence, we found neither stable coexistence nor alternative stable states. All competition experiments led to competitive exclusion. Furthermore, the physiological traits of the species indicated that, if one would find trade-offs in competitive abilities, competition for phosphorus and light would lead to alternative stable states rather than to stable coexistence. These results suggest that stable coexistence mediated by competition for phosphorus and light is rare, and hence an unlikely explanation for the high biodiversity commonly found in phytoplankton communities.

Biogeochemistry of the Kem' River estuary, White Sea (Russia)

Abstract. The biogeochemistry of the river-sea interface was studied in the Kem' River (the largest river flowing to the White Sea from Karelian coast) estuary and adjacent area of the White Sea onboard the RV "Ekolog" in summer 2001, 2002 and 2003. The study area can be divided into 3 zones: I - the estuary itself, with water depth from 1 to 5m and low salinity in the surface layer (salinity is lower than 0.2psu in the Kem' River and varies from 15 to 20psu in outer part of this zone); II - the intermediate zone with depths from 5 to 10m and salinity at the surface from 16 to 22psu; III - the marine zone with depths from 10 to 29 m and salinity 21-24.5psu. Highest concentrations of the suspended particulate matter (SPM) were registered in the Kem' mouth (5-7mg/l). They sharply decreased to values <1mg/l towards the sea. At beginning of July 2001, particulate organic carbon (POC) concentration in the river mouth was 404µg/l and POC content in total SPM was 5.64%. In the marine part of the studied area the POC concentration varied from 132 to 274µg/l and the POC contents in suspended matter increased to 19-52.6%. These studies show, that the majority of riverborne suspended matter in the Kem' estuary deposits near the river mouth within the 20psu isohaline, where sedimentation of the suspended matter takes place. The role of fresh-water phytoplankton species decreases and the role of marine species increases from the river to sea and the percentage of green algae decreases and the role of diatoms increases. The organic carbon (Corg) to nitrogen (N) ratio (Corg/N) in both suspended matter and bottom sediments decreases from the river to the marine part of the mixing zone (from 8.5 to 6.1 in the suspended matter and from 14.6 to 7.5 in the bottom sediments), demonstrating that content of terrestrial-derived organic matter decreases and content of marine organic matter increases from the river mouth to the sea. The Kem' estuary exhibits a similar character of biogeochemial processes as in the large Arctic estuaries, but the scale of these processes (amount of river input of SPM, POC, area of estuaries) is different.

Competition among freshwater phytoplankton species for ammonium in flow-through cultures

Competition among freshwater phytoplankton species for ammonium in flow-through cultures

Photosynthetic and growth responses of three freshwater algae to phosphorus limitation and daylength

Summary1. Three common species of freshwater phytoplankton, the diatom Nitzschia sp., green alga Sphaerocystis schroeteri and cyanobacterium Phormidium luridum, were grown under contrasting daylengths [18 : 6 h light : dark cycles (LD) versus 6 : 18 h LD] and phosphorus (P) regimes (P‐sufficient versus 1 μm P). The rates of growth and photosynthesis, as well as growth efficiencies and pigment concentrations, were compared among treatments.2. The growth and photosynthetic parameters of the three species depended on both P status and daylength in a species‐specific way. The responses to P limitation depended on daylength and, conversely, the responses to daylength depended on P status.3. Growth rates and the maximum rates of photosynthesis (Pmax) of all species decreased under P limitation under both light regimes. However, the decrease of Pmax because of P limitation was greater under long daylength. The Pmax of the green alga S. schroeteri decreased the most (ca. sixfold) under P limitation compared with the other two species. The photosynthesis saturation parameter Ik also decreased under P limitation; the decline was significant in Nitzschia and Sphaerocystis. P‐limitation significantly increased photoinhibition (β) in Nitzschia and Sphaerocystis, but not in Phormidium. The excess photochemical capacity (the ratio of the maximum photosynthesis rate to the photosynthesis rate at the growth irradiance), characterising the ability to utilise fluctuating light, was significantly lower under P limitation.4. The growth efficiency (growth rate normalised to daylength) declined with increasing daylength in all species. Under short daylength the cyanobacterium Phormidium had the lowest growth efficiency of the three species.5. The cellular chlorophyll a concentration in both Nitzschia and Sphaerocystis was significantly higher under short daylength, but only under P‐sufficient conditions. In Nitzschia, under short daylength, P‐limitation significantly decreased cellular chlorophyll concentration. In contrast, P‐limitation increased cellular chlorophyll concentration in Sphaerocystis, but under long daylength only. The ratio of chlorophyll a to b in the green alga also declined under short daylength and under P‐limited conditions.

The Level and Fate of Metals in the Danube River Plume

Trace metal concentrations were measured in the Danube River at different locations along the three main branches of the delta. Results from a systematic delta survey in 1997 and those from the 1995 cruise indicate that the ranges of the total dissolved concentrations in the river end-member are: A1=211–445 nM, Cd=224–302 pM, Co=266–390 pM, Cu=61–120 nM, Fe=21–156 nM, Mn=26–55 nM, Pb=145–220 pM and Zn=11–41 nM. The particulate concentrations were found to be: A1=5·5–6·7%, Cd=1·1–2·4 ppm, Co=16–19 ppm, Cu=201–1092 ppm, Fe=3·7–4·0%, Mn=1286–2290 ppm, Ni=66–77 ppm, Pb=58–65 ppm and Zn=212–224 ppm. The concentrations measured in 1997 confirm that the total dissolved concentrations in the Danube River are low and do not give any evidence of contamination, except for Cu. The particulate concentrations of A1, Ni, Cd, Co and Mn are very similar in the Danube and in uncontaminated world rivers. Pb is found to be enriched by a factor of 3 and Cu by a factor of 14. This enrichment may be due to some mining activity occurring upstream and within the Danube delta area. The evolution of the total dissolved metal concentration (Cd, Cu, Fe, Mn and Zn) along the salinity gradient established in 1997 for the Chilia and Sulina branches confirmed the low reactivity of dissolved trace metals. The only exception being an addition of manganese in front of the Chilia branch. This excess may be attributed to the occurrence of highly labile particulate manganese originating from a local source within the Chilia branch, probably from mining waste. The comparison between field data for winter and spring conditions do not show any significant difference for Cd, Mn and Zn. The comparison with results from the in vitro mixing of river and seawater seems to indicate that the processes involved in the addition of Cd and Zn are inorganic. In winter, the total dissolved iron concentrations were found to be pH-dependent, whereas in spring, due to the beginning of photosynthetic activity, the pH increased within the estuary, and the lower concentrations of Fe observed (down to around 10nM) can be considered as an indirect consequence of the biological activity. The Cu distribution was found to be conservative in winter; in spring, the river concentrations are reduced by a factor of 1·4, which could have resulted from biological uptake by freshwater phytoplankton species. The distribution also seemed to show a slight removal of Cu, similar to the one observed for silica, suggesting that some uptake took place in the low salinity area.

Effects of bensulfuron-methyl and cinosulfuron on growth of four freshwater species of phytoplankton

The acute toxicity of sulfonylurea herbicides bensulfuron-methyl and cinosulfuron was tested on the five species of freshwater phytoplankton: Scenedesmus acutus, Scenedesmus subspicatus, Chlorella vulgaris and Chlorella saccharophila. Herbicide concentrations eliciting a 50% growth reduction over 96 h (EC 50) ranged from 8 to 104 mg/l for cinosulfuron and from 0.015 to 6.2 mg/l for bensulfuron-methyl. The pesticides bensulfuron-methyl, atrazine and benthiocarb were more toxic than cinosulfuron, chlorsulfuron, molinate, fenitrothion and pyridaphenthion in a toxicity study with the same algal species. The transformation of effective concentrations of bensulfuron-methyl and cinosulfuron and other pesticides, obtained from toxicity measurements, into percent of the saturation level in water is used as a first evaluation of potential hazard to aquatic systems. The herbicides cinosulfuron, methyl-bensulfuron, atrazine and chlorsulfuron were more dangerous than the herbicides benthiocarb and molinate and than the insecticides fenitrothion and pyridaphenthion, in a study of hazard evaluation. The two species of Chlorella were more tolerant to both herbicides than the two species of Scenedesmus. A potential environmental hazard of sulfonylurea herbicides to aquatic systems has to be expected even at low environmental concentrations.

Effects of pyridaphenthion on growth of five freshwater species of phytoplankton. A laboratory study

The acute toxicity of the insecticide and acaricide pyridaphenthion to five species of freshwater phytoplankton, Scenedesmus acutus, Scenedesmus subspicatus, Chlorella vulgaris, Chlorella saccharophila and Pseudanabaena galeata was determined. Insecticide concentrations eliciting a 50% growth reduction over 96 h (EC 50) ranged from 2.2 to 30.9 mg/l. The two species of Chlorella and the cyanobacteria P. galeata were more tolerant than the two species of Scenedesmus. Concentrations of pyridaphenthion detected in some natural waters were less than the toxic threshold for these species.

Community Assembly in Marine Phytoplankton: Application of Recent Models to Harmful Dinoflagellate Blooms

AMBLESIDE, CUMBRIA LA  LP, UK The habitat preferences of dinoflagellate bloom species along an onshore‐offshore, mixing-nutrient gradient, their associated life-form (morphotype) characteristics and adaptive strategies were evaluated from the perspective of Margalef ’s Mandala and Reynolds Intaglio. Nine different mixingnutrient habitats and associated dinoflagellate life-form types having distinctive morphotype features and habitat preferences are distinguishable. Reynolds Intaglio provided greater fidelity to actual in situ dinoflagellate community assembly than the Mandala. We suggest that the correlation between degree of mixing and nutrient levels presumed in the Mandala is not the essential interaction in the selection of life forms and their succession. A more significant aspect of the turbulence axis is the degree of vertical, micro-habitat structural differentiation that it permits. Three primary adaptive strategies consistent with C-S-R strategies recognized among freshwater phytoplankton species characterize the component dinoflagellate species: invasive, small- to intermediate-sized colonist species (C) which often predominate in chemically-disturbed water bodies; acquisitive, larger-celled, nutrient stresstolerant species (S); and disturbance-tolerant ruderal species (R) tolerant of shear/stress forces in physically-disturbed water masses (fronts, upwelling relaxations, current entrainment). It is suggested that harmful algal bloom community assembly and dynamics reflect two basic selection features— life-form and species-specific selection, that commonly held life-form properties override phylogenetic properties in bloom-species selection, and that the latter is often stochastic, rather than singular. The high degree of unpredictability of individual species blooms is consistent with stochastic selection, e.g. bloom species are often selected as a result of being in the right place at the right time at suitable inoculum levels. A focus on the life-form properties, habitat preference and stochastic selection of bloom species would appear to be more viable and realistic than current ecological investigative approaches.

Effects of the organophosphorus insecticide fenitrothion on growth in five freshwater species of phytoplankton.

The acute toxicity of the insecticide fenitrothion was measured using four freshwater algae (Chlorella saccharophila, Chlorella vulgaris, Scenedesmus acutus, and Scenedesmus subspicatus) and one cyanobacteria (Pseudanabaena galeata). Insecticide concentrations eliciting 50% growth reduction over 96 hr (EC50) ranged from 0.84 to 11.9 mg/L. Fenitrothion was more toxic than other pesticides studied with the same algal species such as chlorsulfuron, molinate, and pyridaphenthion. The transformation of effective concentrations of fenitrothion and other pesticides obtained from toxicity measurements into percent of the saturation level in water is used as a first evaluation of potential hazard to aquatic systems. The insecticides fenitrothion and pyridaphenthion were less hazardous than the herbicides atrazine, benthiocarb, cinosulfuron, chlorsulfuron, methyl-bensulfuron, and molinate. The two species of Chlorella and the cyanobacterium Pseudanabaena were more tolerant to fenitrothion than the two species of Scenedesmus.

Growth rates of phytoplankton under fluctuating light

Summary 1 The effect of light fluctuations on the growth rates of four species of freshwater phytoplankton was investigated. Experimental light regimes included constant irradiance and fluctuations of a step function form, with equal proportion of high (maximum of 240 µmol photons m-2 s-1) and low light (minimum of 5 µmol photons m-2 s-1) (or dark) in a period. Fluctuations of 1, 8 and 24-h periods were imposed over several average irradiances (25, 50, 100 and 120 µmol photons m-2 s-1). 2 Growth rate responses to fluctuations were species-specific and depended on both the average irradiance and the period of fluctuations. Fluctuations at low average irradiances slightly increased growth rate of the diatom Nitzschia sp. and depressed growth of the cyanobacterium Phormidium luridum and the green alga Sphaerocystis schroeteri compared to a constant irradiance. 3 Fluctuations at higher average irradiance did not have a significant effect on the growth rates of Nitzschia sp. and Sphaerocystis schroeteri (fluctuations around saturating irradiances) and slightly increased the growth rates of the cyanobacteria Anabaena flos-aquae and Phormidium luridum (when irradiance fluctuated between limiting and inhibiting levels). 4 In general, the effect of fluctuations tended to be greater when irradiance fluctuated between limiting and saturating or inhibiting levels of a species growth-irradiance curve compared to fluctuations within a single region of the curve. 5 The growth rates of species under fluctuating light could not always be predicted from their growth-irradiance curves obtained under constant irradiance. When fluctuations occur between limiting and saturating or inhibiting irradiances for the alga and when the period of fluctuations is long (greater than 8 h), steady-state growth-irradiance curves may be insufficient to predict growth rates adequately. Consequently, additional data on physiological acclimation, such as changes in photosynthetic parameters, may be required for predictions under non-constant light supply in comparison to constant conditions.

Identification of phytoplankton from flow cytometry data by using radial basis function neural networks.

We describe here the application of a type of artificial neural network, the Gaussian radial basis function (RBF) network, in the identification of a large number of phytoplankton strains from their 11-dimensional flow cytometric characteristics measured by the European Optical Plankton Analyser instrument. The effect of network parameters on optimization is examined. Optimized RBF networks recognized 34 species of marine and freshwater phytoplankton with 91. 5% success overall. The relative importance of each measured parameter in discriminating these data and the behavior of RBF networks in response to data from "novel" species (species not present in the training data) were analyzed.

Transport of silica in a stratified estuary

The enrichment of dissolved silica found in the marine layer near the head of the highly stratified Krka estuary is attributed to sinking of freshwater diatoms through the halocline and subsequent decomposition of biogenic silica. In the marine layer, freshwater diatoms sink and order of magnitude slower than in the brackish layer. As a consequence their dissolution path is shorter. Freshwater phytoplankton species contributing to the majority of silica enrichment are Cyclotella sp. and Synedra acus. Their sedimentation rate in the brackish and in marine layers is estimated.

Predicting algal sensitivity to a pesticide stress

AbstractTwelve freshwater phytoplankton species were used to investigate the factors affecting the toxicity of the organo‐phosphorus insecticide fenitrothion (O,O‐dimethyl‐O‐nitro‐m‐tolyl phosphorothioate) to algae. The unicellular chlorophytesAnkistrodesmus falcatus, Chlamydomonas segnis, Chlamydomonas reinhardtii, Chlorella pyrenoidosa, Chlorella vulgaris, Cosmariumsp.,Pediastrumsp.,Scenedesmus obliquus, Selenastrum capricornutum, and Staurastrumsp.; the bacillariophyteNaviculasp.; and the cyanophyteAnabaenasp. were exposed to three concentrations (0.1, 1.0, and 10.0 mg/L) of fenitrothion. Differential growth effects were observed among the species exposed to fenitrothion over short (96 h) and long‐term (14 d) durations. Fenitrothion concentrations eliciting a 50% growth reduction over 96 h (EC50) ranged from 0.8 to 24.4 mg/L. Selected properties of the test algae (cell size, lipid content, and bioconcentration capacity) were measured and examined for their relationship to fenitrothion sensitivity. Strong correlations were obtained between fenitrothion sensitivity and cell surface area/volume (S/V) ratios, cell lipid content, and fenitrothion bioconcentration capacity of the cells, suggesting that these attributes may be useful predictors of differential sensitivity to lipophilic xenobiotics in unicellular phytoplankton. A positive relationship observed between cell S/V ratio and the bioconcentration of fenitrothion further implicates algal cell size as a significant factor in alga/pesticide interaction and subsequent vulnerability to lipophilic xenobiotics.

Optimization of the Electron Transport System (ETS) method for natural phytoplankton assemblages tested with some species of freshwater phytoplankton

The applicability of the ETS method for natural phytoplankton assemblages was tested with a number of freshwater phytoplankton species: Scenedesmus quadricauda, Chlamydomonas reinhardtii, Oscillatoria agardhii and Stephanodiscus hantzschii. The reproducibility and recovery of the method is very good when membrane filters are used and the concentrated sample is removed from the filter by brush. Three to five minutes appear to be sufficient to release the ETS activity. The following aspects conditions should be taken into account: (1) The processed sample stored for not longer than 30 min on ice; (2) the extinction must not be higher than 0.6, (3) reaction time not longer than 30 min, and (4) no “hard” species must dominate the water sample. The recovery of the size-fractionated water sample, based on the activity of the whole sample, was not significantly different from 100% at the level of P = 0.01.

The growth inhibition of planktonic algae due to surfactants used in washing agents

A survey of inhibitory effects of nonionic and anionic surfactants, including a soap, used in washing agents, on the growth on three species of freshwater phytoplankton, Selenastrum capricornutum, Nitzschia fonticola and Microcystis aeruginosa was conducted. Based on the specific growth rate, μu estimated from a short period (2 or 3 days) cultivation of test algae, the growth inhibition was determined using EC 50 values where μu in the culture medium with surfactant decreased 50% of that without surfactant. The EC 50 values of nonionic and anionic surfactants tested here for S. capricornutum ranged from 2 to 50 mg l −1 and from 10 to 100 mg l −1, respectively. The tolerances of three species of algae tested with three surfactants, LAS, AE (EO:9) and soap, were different and the inhibitory effects were species specific. EC 50 values of LAS, AE (EO:9) and soap for S. capricornutum were 50–100, 4–8 and 10–50 mg l −1, respectively. Those for N. fonticola were 20–50, 5–10 and 20–50 mg l −1, and those for M. aeruginosa were 10–20, 10–50 and 10–20 mg l −1, respectively.

Freshwater components in the diet of the marine neustonic fish, Urophycis tenuis (Mitchill)

Stomach content analysis of a neustonic marine juvenile white hake (Urophycis tenuis (Mitchill)), revealed the presence of a unusual 0.70 mm bolus, consisting of a freshwater rotifer, Keratella cochlearis, and several species of freshwater phytoplankton: Asterionella formosa, Melosira granulata, Dinobryon bavaricum and Dinobryon cylindricum. Other gut items were typical for the predator during the August period, consisting of various stages of marine calanoid copepods and cladocerans; average prey length was 0.74 mm. The possibility of bolus introduction as a secondary diet component was eliminated; evidence indicated that the particle was ingested in toto. Consideration of a number of alternative mechanisms for bolus acquisition led to the conclusion that the bolus was disseminated via the ballast tank or contaminated freshwater holding tank of a ship. Urophycis tenuis appears to feed selectively on the basis of particle size. Consequently, this type of neustonic predator may be particularly vulnerable to man-made pollution and oil spills.

The Depletion of Carbon Dioxide from Lake Water by Phytoplankton

It has long been known that dense populations of phytoplankton tend to deplete the carbon dioxide present in natural waters, with an associated raising of pH. The ecological significance of these reactions, as possible growth-limiting or retarding factors, is far from clear. This situation is remarkable in view of the intensive study given to the relationship between rates of photosynthesis and carbon dioxide supply in some unicellular algae, the numerous measurements of carbon assimilation by phytoplankton in nature, and the attention bestowed on pH as an ecological factor. Recently a controversy has developed around the relative importance of carbon and phosphorus supply in the enrichment ('eutrophication') of inland waters (e.g. Kuentzel 1969, 1971; King 1970; Kerr, Paris & Brockway 1970; Kerr et al. 1972; Schindler 1971; Schindler et al. 1973; Goldmann et al. 1972; Goldman, Oswald & Jenkins 1974), partly sustained by a shortage of detailed information on the dynamics and availability of inorganic carbon in freshwaters. In particular, the exchange of carbon dioxide between atmosphere and water is rarely estimated, the interrelations of various forms of carbon dioxide are rarely assessed, analytical methods are usually unspecific, and the relevant physiological responses of characteristic common species of freshwater phytoplankton are largely unknown. The present work developed from observations on depletions of carbon dioxide and upward pH shifts, occasionally very pronounced, in two English lake waters. Examples are described in relation to the algal crops involved and the stratification of environmental factors. The general limnological background of these environmental events, including details of diurnal changes, will be described more fully elsewhere. Further analysis is based upon systematic laboratory measurements of photosynthetic activity in relation to episodes of algal production in nature, extended to experimental manipulations of media, population density, and time-sequences of carbon dioxide consumption. As the physiological work is based upon natural populations of known history, it is hoped that ecological inferences can be drawn without undue extrapolation between the properties of different species and different media.

On Growth and Development: Parts I and II

<h3>ABSTRACT</h3> Understanding how changes in temperature affect interspecific competition is critical for predicting changes in ecological communities as the climate warms. Here we develop a simple theoretical model that links interspecific differences in metabolic traits, which capture the temperature-dependence of resource acquisition, to the outcome of pairwise competition in phytoplankton. We parameterised our model with metabolic traits derived from six species of freshwater phytoplankton and tested its ability to predict the outcome of competition in all pairwise combinations of the species in a factorial experiment, manipulating temperature and nutrient availability. The model correctly predicted the outcome of competition in 71% of the pairwise experiments. These results demonstrate that metabolic traits play a key role in determining how changes in temperature influence interspecific competition and lay the foundation for developing theory to predict the effects of warming in complex, multi-species communities.