Interactions between red tide microalgae and herbivorous zooplankton: effects of two bloom-forming species on the rotifer <Emphasis Type="Italic">Brachionus plicatilis</Emphasis> (O.F. Muller)

Experiments were carried out to investigate interspecific interactions between the rotifer Brachionus plicatilis and two harmful algal bloom (HAB) species using single and mixed culture methods. B. plicatilis populations and the growth of two algae were compared at different algal cell densities. The results demonstrate that B. plicatilis obtained sufficient nutrition from Alexandrium tamarense to support net population increase. When exposed to a density of 8 × 10⁴ cells ml⁻¹ A. tamarense, the number of B. plicatilis increased faster than it did when exposed to other four algal densities (16 × 10⁴, 24 × 10⁴, 32 × 10⁴, and 40 × 10⁴ cells ml⁻¹). Cell densities of A. tamarense decreased due to the grazing of B. plicatilis. In contrast, Heterosigma akashiwo had an adverse effect on the B. plicatilis population and its growth was largely unaffected by rotifer grazing. In this case, the B. plicatilis population decreased and H. akashiwo grew at a rate similar to that of a control without addition of rotifers. Mixed culture experiments showed that A. tamarense could partly counteract the effect of H. akashiwo in limiting the rate of population increase of rotifer. In addition, the effect of different initial cell densities on interspecific competition between A. tamarense and H. akashiwo in mixed culture(s) was also investigated. The results show that A. tamarense competed very successfully when the inoculation proportions of A. tamarense and H. akashiwo were 40:5 and 40:30. Handling editor: D. Hamilton     

Enhanced species-specific chemical control of harmful and non-harmful algal bloom species by the thiazolidinedione derivative TD49

Culture experiments involving 23 algae strains were conducted to evaluate the algicidal effects of a newly developed algicidal thiazolidinedione (TD) derivative (TD49) on non-harmful and harmful algal bloom (HAB) species. We also assessed the effect of various concentrations of TD49 on various growth phases (lag, logarithmic, and stationary) of the harmful algae Heterocapsa circularisquama (Dinophyceae) and Heterosigma akashiwo (Raphidophyceae; hereafter, Heterosigma) and the non-harmful diatoms Skeletonema costatum and Chaetoceros didymus. The inhibitory ratios (%) for H. circularisquama and Heterosigma at 2.0 μM TD49 were significantly higher than those at other concentrations, and the inhibitory ratio varied depending on growth phase and species as follows: logarithmic?≥?stationary?>?lag phase for H. circularisquama and logarithmic?≥?lag?>?stationary phase for Heterosigma. Although the inhibitory ratios for C. didymus were similar to those for the two harmful algae (H. circularisquama and Heterosigma), inhibitory effects on S. costatum were not apparent at >2.0 μM in any growth phase. The algicidal activity of TD49 on the harmful and non-harmful algae was as follows: unarmored HAB species?>?armored HAB species?>?diatom species?>?cryptophyte species. TD49 was algicidal to most HABs but had a little inhibitory effect on some non-harmful algae, implying that TD49 has selective algicidal activity. Our results indicate that TD49 is potentially of use in the control of HAB species within semi-enclosed bays.     

Changes in photosynthesis and antioxidant defenses of Picea asperata seedlings to enhanced ultraviolet-B and to nitrogen supply

The paper mainly studied the effects of ultraviolet‐B (UV‐B) radiation, nitrogen, and their combination on photosynthesis and antioxidant defenses of Picea asperata seedlings. The experimental design included two levels of UV‐B treatments (ambient UV‐B, 11.02 KJ m⁻² day⁻¹; enhanced UV‐B, 14.33 KJ m⁻² day⁻¹) and two nitrogen levels (0; 20 g m⁻² a⁻¹ N) – to determine whether the adverse effects of UV‐B are eased by supplemental nitrogen. Enhanced UV‐B significantly inhibited plant growth, net photosynthetic rate (A), stomatal conductance to water vapor (Gs), transpiration rate and photosynthetic pigment, and increased intercellular CO₂ concentration, UV‐B absorbing compounds, proline content, malondialdehyde (MDA) content, and activity of antioxidant enzymes (peroxidase (POD), superoxide dimutase, and glutathione reductase). Enhanced UV‐B also reduced needle DW and increased hydrogen peroxide (H₂O₂) content and the rate of superoxide radical (O₂⁻) production only under supplemental nitrogen. On the other hand, supplemental nitrogen increased plant growth, A, Gs, chlorophyll content and activity of antioxidant enzymes (POD, ascorbate peroxidase, and catalase), and reduced MDA content, H₂O₂ content, and the rate of O₂⁻ production only under ambient UV‐B, whereas supplemental nitrogen reduced activity of antioxidant enzymes under enhanced UV‐B. Carotenoids content, proline content, and UV‐B absorbing compounds increased under supplemental nitrogen. Moreover, significant UV‐B × nitrogen interaction was found on plant height, basal diameter, A, chlorophyll a, activity of antioxidant enzymes, H₂O₂, MDA, and proline content. These results implied that supplemental nitrogen was favorable for photosynthesis and antioxidant defenses of P.asperata seedlings under ambient UV‐B. However, supplemental nitrogen made the plants more sensitive to enhanced UV‐B, although some antioxidant indexes increased.     

Comparative studies on the allelopathic effects of two different strains of Ulva pertusa on Heterosigma akashiwo and Alexandrium tamarense

Allelopathic effects of fresh tissue and dry powder of a nonsexual and a sexual strain of the macroalga Ulva pertusa on the growth of the microalgae Heterosigma akashiwo and Alexandium tamarense were evaluated using long-term coexistence culture systems in which several concentrations of macroalga fresh tissue and dry powder were used. The effects of macroalga culture medium filtrate on the two HAB algae were also investigated. Moreover, isolation co-culture systems were built to confirm the existence of allelochemicals and preclude the growth inhibition by direct contact. Short-term algicidal effect assays of macroalgae on H. akashiwo were carried out to measure the rate of algal cell lysis. The results of the coexistence assays showed that the growth of H. akashiwo and A. tamarense was strongly inhibited by fresh tissue and by dry powder of both strains of U. pertusa. The allelochemicals were lethal to H. akashiwo at relatively higher concentrations. The macroalga culture medium filtrate exhibited no apparent growth inhibitory effect on the two HAB algae under initial or semicontinuous filtrate addition, which suggested that continuous release of small quantities of rapidly degradable allelochemicals from the fresh tissue of both strains of U. pertusa was essential to effectively inhibit the growth of H. akashiwo and A. tamarense.     

Broad Salinity Tolerance as a Refuge from Predation in the Harmful Raphidophyte Alga Heterosigma akashiwo (Raphidophyceae)

The ability of harmful algal species to form dense, nearly monospecific blooms remains an ecological and evolutionary puzzle. We hypothesized that predation interacts with estuarine salinity gradients to promote blooms of Heterosigma akashiwo (Y. Hada) Y. Hada ex Y. Hara et M. Chihara, a cosmopolitan toxic raphidophyte. Specifically, H. akashiwo's broad salinity tolerance appears to provide a refuge from predation that enhances the net growth of H. akashiwo populations through several mechanisms. (1) Contrasting salinity tolerance of predators and prey. Estuarine H. akashiwo isolates from the west coast of North America grew rapidly at salinities as low as six, and distributed throughout experimental salinity gradients to salinities as low as three. In contrast, survival of most protistan predator species was restricted to salinities >15. (2) H. akashiwo physiological and behavioral plasticity. Acclimation to low salinity enhanced H. akashiwo's ability to accumulate and grow in low salinity waters. In addition, the presence of a ciliate predator altered H. akashiwo swimming behavior, promoting accumulation in low‐salinity surface layers inhospitable to the ciliate. (3) Negative effects of low salinity on predation processes. Ciliate predation rates decreased sharply at salinities <25 and, for one species, H. akashiwo toxicity increased at low salinities. Taken together, these behaviors and responses imply that blooms can readily initiate in low salinity waters where H. akashiwo would experience decreased predation pressure while maintaining near‐maximal growth rates. The salinity structure of a typical estuary would provide this HAB species a unique refuge from predation. Broad salinity tolerance in raphidophytes may have evolved in part as a response to selective pressures associated with predation.     

东海原甲藻与中肋骨条藻的种间竞争数值模拟

研究探讨了两个零维箱式模型在东海典型赤潮藻东海原甲藻和中肋骨条藻竞争与演替研究中的应用。模型在采用不同接种密度下的单种培养实验数据进行参数校正后,被用来模拟不同N/P条件下单种培养实验以及两藻种共培养竞争实验,并以实验数据对其结果进行了验证。模拟结果表明,在单种培养条件下,模型能够较好地重现两种藻在不同N/P环境中的生长及对营养盐的利用;共培养实验的模拟结果显示,在所有初始细胞密度比例条件下,中肋骨条藻的最终密度均会超过东海原甲藻,且PO4的消耗主要源于中肋骨条藻的利用,与实验结果一致,表明模型能够很好地体现两种藻的竞争结果及对营养盐的竞争关系;由于模型不足以模拟除营养盐竞争以外的藻间相互作用,模拟结果未体现东海原甲藻细胞数迅速衰减这一现象,有待进一步研究。     

The effects of UV-B radiation on epidermal anatomy in loblolly pine (Pinus taeda L.) and Scots pine (Pinus sylvestris L.)

The effects of enhanced UV‐B radiation on the needle anatomy of loblolly pine (Pinus taeda L.) and Scots pine (Pinus sylvestris L.) were studied in the field under supplemental UV‐B radiation supplied by a modulated irradiation system. The supplemental UV‐B levels were designed to simulate either a 16 or 25% loss of stratospheric ozone over College Park, Maryland. Enhanced UV‐B radiation caused different responses in these two species. The needles of loblolly pine had larger amounts of tannin in the lumen of epidermal cells and more wall‐bound phenolics in the outer epidermal walls of UV‐B‐treated needles, whereas the most pronounced effect on Scots pine needles was increased cutinization. In both species, the outer epidermal cell walls thickened and the needle cross‐sectional and mesophyll areas decreased (statistically significantly only in Scots pine). This suggests that more carbon may have been allocated to the protection mechanisms at the expense of photosynthetic area. The difference in response between these species suggests that the response to UV‐B radiation is not mediated by a single mechanism and that no generalization with regard to the effects of UV‐B on conifers can be made.     

Development of an immunofluorescence technique for detecting <Emphasis Type="Italic">Prorocentrum donghaiense</Emphasis> Lu

Prorocentrum donghaiense Lu is a key harmful algal bloom (HAB) species which is widespread along the China Sea coast. In this study, P. donghaiense-specific antiserum was developed, and the detection method, based on immunofluorescence (IF), was optimized. The antiserum was raised using 0.5% paraformaldehyde-fixed whole cells (WC) as antigen. The titer and the specificity were examined using whole-cell IF. Results showed that ethanol was an effective decolorization reagent, and 80% ethanol was able to minimize autofluorescence of cells. Samples preserved by freezing at −20°C or −80°C remained above 85% detection efficiency after 1-month storage. The antiserum against WC had a high titer (1:10000), and exhibited high specificity at species level. The antiserum showed a weak cross reaction with the closely related species P. dentatum HK, P. dentatum CCMP1517 and P. minimum HK only at very low dilution (1:5). However, it did not cross-react with the species from the same genus or other phytoplankton species when the dilution reached or exceeded 1:100. Results from different P. donghaiense samples collected at different growth phases or grown under different nutrient conditions showed no significant difference in IF intensity. In addition, the antiserum exhibited high specific binding to P. donghaiense in both mixed phytoplankton samples and field samples. The results indicate that the technique is a potentially useful tool for the rapid identification of P. donghaiense and can facilitate the analysis of various natural samples.     

INTERSTRAIN VARIABILITY IN PHYSIOLOGY AND GENETICS OF HETEROSIGMA AKASHIWO (RAPHIDOPHYCEAE) FROM THE WEST COAST OF NORTH AMERICA1

High levels of intraspecific variability are often associated with HAB species, and this variability is likely an important factor in their competitive success. Heterosigma akashiwo (Hada) Hada ex Y. Hara et M. Chihara is an ichthyotoxic raphidophyte capable of forming dense surface‐water blooms in temperate coastal regions throughout the world. We isolated four strains of H. akashiwo from fish‐killing northern Puget Sound blooms in 2006 and 2007. By assessing numerous aspects of biochemistry, physiology, and toxicity, we were able to describe distinct ecotypes that may be related to isolation location, source population, or bloom timing. Contrasting elements among strains were cell size, maximum growth and photosynthesis rates, tolerance of low salinities, amino acid use, and toxicity to the ciliate grazer Strombidinopsis acuminatum (Fauré‐Fremiet). In addition, the rDNA sequences and chloroplast genome of each isolate were examined, and while all rDNA sequences were identical, the chloroplast genome identified differences among the strains that tracked differences in ecotype. H. akashiwo strain 07A, which was isolated from an unusual spring bloom, had a significantly higher maximum potential photosynthesis rate (28.7 pg C · cell^?1 · h^?1) and consistently exhibited the highest growth rates. Strains 06A and 06B were not genetically distinct from one another and were able to grow on the amino acids glutamine and alanine, while the other two strains could not. Strain 07B, which is genetically distinct from the other three strains, exhibited the only nontoxic effect. Thus, molecular tools may support identification, tracking, and prediction of strains and/or ecotypes using distinctive chloroplast gene signatures.     

Alga-lytic activity of Pseudomonas fluorescens against the red tide causing marine alga Heterosigma akashiwo (Raphidophyceae)

A bacterial strain, HAK-13, exhibited strongest activity against Heterosigma akashiwo and was capable of controlling this bloom forming phytoplankton. Based on 16S rDNA sequences and biochemical and morphological characteristics, the strain HAK-13 was determined to be Pseudomonas fluorescens on the basis of 99.9% similarity with reference strains in the DNA databases. The growth of H. akashiwo was strongly suppressed by HAK-13 in all growth phases, with the strongest alga-lytic activity noted against harmful bloom-forming species in the exponential stage (6–22 days). Host range tests showed that HAK-13 also significantly inhibited the growth of Alexandrium tamarense and Cochlodinium polykrikoides but could not destroy Gymnodinium catenatum. P. fluorescens HAK-13 indirectly attacked H. akashiwo by alga-lytic substances that might be located at the compartment of cytoplasmic membrane of the bacterium at a level of 45.86 units/mg of specific activity. The results indicated that P. fluorescens HAK-13 caused cell lysis and death of H. akashiwo, A. tamarense, and C. polykrikoides dramatically and Prorocentrum dentatum slightly. Therefore, P. fluorescens HAK-13 has potential for use as a selective biocontrol of harmful algal blooms.     

Species-specific effect of UV-B radiation on the temporal pattern of leaf growth

Recent molecular and physiological studies have demonstrated that ultraviolet‐B radiation (UV‐B) can affect some of the processes involved in leaf growth, but the phases of leaf growth affected have not been clearly delimited. We used functional growth analysis to assess the effects of UV‐B radiation on the time course of leaf growth in seedlings of two birch species (Betula pendula and Betula pubescens). Our aim was to identify the phase(s) of leaf development affected by UV‐B radiation. In a greenhouse study, 1‐year‐old birch seedlings were subjected to three daily doses of supplemental UV‐B radiation treatments (UV‐B⁺) and no UV‐B radiation controls (UV‐B^?). Leaf growth measurements every 2 days were complemented by assessment of other functional traits over a 4‐week period at the start of the growing season. Using fitted curves, we were able to determine that the rate of leaf expansion was slowed by the UV‐B⁺ treatment in leaves of B. pendula because of a slower maximum leaf growth rate compared with plants under the UV‐B^? controls, but that compensation toward the end of the period of expansion negated this difference when leaves reached their final size. UV‐B⁺ had little effect on the rate of B. pubescens leaf growth despite a larger reduction in leaf final size due to UV‐B⁺ than occurred in B. pendula leaves. In conclusion, effective regulation ameliorated the effects of UV‐B radiation on leaf and seedling growth in B. pendula, whereas in B. pubescens, reductions in leaf final size under UV‐B⁺ were consistent with a slightly reduced rate of height growth.     

Interactions between metazoans,autotrophs, mixotrophs and bacterioplankton in nutrient‐depleted high DOC environments: a long‐term experiment

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Spatial, seasonal and species variations of harmful algal blooms in the South Yellow Sea and East China Sea

The occurrences of harmful algal blooms (HABs), in terms of frequency and area in the Chinese coastal waters, have been increasing since 1980s and caused considerable economic losses. In the present study, we have analyzed spatial and seasonal characteristics of HAB events in the southern Yellow Sea and East China Sea along Chinese coast from 1933 to 2004. With a total 435 HAB records, the most frequent HAB occurrence area (FHA) is off the Yangtze River mouth and another two FHA areas are located south of the Yangtze River estuary along about isobaths of 30–60 m coastal water in the East China Sea. The time of HAB occurrence shifted during our study period: from autumn (August–October) before 1980s to July–August in 1980s, during May–July in 1990s, and May–June for the period of 2000–2004. Causative species were found to be different: Noctiluca scintillans and Skeletonema costatum were dominant causative species prior to 2000; and Prorocentrum donghaiense Lu was dominant from 2000 to 2004 and also caused large blooms in May. Trichodesmium sp. caused many HABs in autumn (August–October) prior to 1980s with only one HAB between 1980 and 2004. The changes of the dominant HAB species may have affected the timings of HAB occurrence, as well as the increasing HAB-affected areas in recent years.     

Proteomic analysis provides new insights into the adaptive response of a dinoflagellate Prorocentrum donghaiense to changing ambient nitrogen

Nitrogen (N) is the major nutrient limiting phytoplankton growth and productivity over large ocean areas. Dinoflagellates are important primary producers and major causative agents of harmful algal blooms in the ocean. However, very little is known about their adaptive response to changing ambient N. Here, we compared the protein profiles of a marine dinoflagellate Prorocentrum donghaiense grown in inorganic N‐replete, N‐deplete and N‐resupplied conditions using 2‐D fluorescence differential gel electrophoresis. The results showed that cell density, chlorophyll a and particulate organic N contents presented low levels in N‐deplete cells, while particulate organic carbon content and glutamine synthetase (GS) activity maintained high levels. Comparison of the protein profiles of N‐replete, N‐deplete and N‐resupplied cells indicated that proteins involved in photosynthesis, carbon fixation, protein and lipid synthesis were down‐regulated, while proteins participating in N reallocation and transport activity were up‐regulated in N‐deplete cells. High expressions of GS and 60 kDa chaperonin as well as high GS activity in N‐deplete cells indicated their central role in N stress adaptation. Overall, in contrast with other photosynthetic eukaryotic algae, P. donghaiense possessed a specific ability to regulate intracellular carbon and N metabolism in response to extreme ambient N deficiency.     

Red : far-red light ratio and UV-B radiation: their effects on leaf phenolics and growth of silver birch seedlings

The natural variation in quantity and quality of light modifies plant morphology, growth rate and concentration of biochemicals. The aim of two growth‐room experiments was to study the combined effects of red (R) and far‐red (FR) light and ultraviolet‐B (UV‐B) radiation on the concentrations of leaf phenolics and growth and morphology of silver birch (Betula pendula Roth) seedlings. Analysis by high‐performance liquid chromatography showed that the leaves exposed to supplemental FR relative to R contained higher concentrations of total chlorogenic acids and a cinnamic acid derivative than the leaves treated with supplemental R relative to FR. In contrast, concentration of a flavonoid, quercetin 3‐galactoside, was higher in the R + UV‐B leaves than in the FR + UV‐B leaves. The UV‐B induced production of kaempferols, chlorogenic acids and most quercetins were not modified by the R : FR ratio. Growth measurements showed that the leaf petioles and stems of FR seedlings were clearly longer than those of R seedlings, but leaf area was reduced by UV‐B radiation. Results of these experiments show that exposure of silver birch seedlings to supplemental FR compared to R leads to fast elongation growth and accumulation of phenolic acids in the leaves.     

Meta‐analysis reveals enhanced growth of marine harmful algae from temperate regions with warming and elevated CO2 levels

Elevated pCO₂ and warming may promote algal growth and toxin production, and thereby possibly support the proliferation and toxicity of harmful algal blooms (HABs). Here, we tested whether empirical data support this hypothesis using a meta‐analytic approach and investigated the responses of growth rate and toxin content or toxicity of numerous marine and estuarine HAB species to elevated pCO₂ and warming. Most of the available data on HAB responses towards the two tested climate change variables concern dinoflagellates, as many members of this phytoplankton group are known to cause HAB outbreaks. Toxin content and toxicity did not reveal a consistent response towards both tested climate change variables, while growth rate increased consistently with elevated pCO₂. Warming also led to higher growth rates, but only for species isolated at higher latitudes. The observed gradient in temperature growth responses shows the potential for enhanced development of HABs at higher latitudes. Increases in growth rates with more CO₂ may present an additional competitive advantage for HAB species, particularly as CO₂ was not shown to enhance growth rate of other non‐HAB phytoplankton species. However, this may also be related to the difference in representation of dinoflagellate and diatom species in the respective HAB and non‐HAB phytoplankton groups. Since the proliferation of HAB species may strongly depend on their growth rates, our results warn for a greater potential of dinoflagellate HAB development in future coastal waters, particularly in temperate regions.     

EFFECTS OF UV RADIATION ON GROWTH AND PHLOROTANNINS IN FUCUS GARDNERI (PHAEOPHYCEAE) JUVENILES AND EMBRYOS1

Diminishing levels of atmospheric ozone are increasing UV stress on intertidal algae. Early developmental stages tend to be more susceptible to environmental stresses; however, little research has examined how these stages are protected from UV radiation (UVR). Many brown algae contain high levels of phlorotannins, which are thought to function in screening UVR. In this study, we tested the effects of ambient levels of UV‐B and UV‐A on growth and phlorotannin production in 1‐ to 2‐cm juvenile and microscopic postsettlement embryos of the intertidal alga Fucus gardneri Silva. Algae were grown in four light treatments: 1) ambient light; 2) under cellulose acetate, which lowered light quantity but did not affect light quality; 3) under Mylar^TM, which filtered UV‐B; and 4) under Plexiglas^TM, which blocked UV‐A and UV‐B. Over a 3‐week period, UV‐B inhibited and UV‐A enhanced the growth of F. gardneri embryos, whereas the growth of juveniles was not affected. Phlorotannin concentrations of both embryos and juveniles did not differ in any of the light treatments. Our results suggest that embryos of F. gardneri are susceptible to UV light but develop a tolerance to it as they mature. This tolerance may result from increases in phlorotannin concentrations that occur during maturation; however, phlorotannin production in embryonic or juvenile stages is either not induced by UV light or takes more than 3 weeks to occur.     

pEffects of UV radiation on the ultrastructure of several red algae

The effect of ultraviolet (UV) radiation on the ultrastructure of four red algae, the endemic Antarctic Palmaria decipiens (Reinsch) Ricker and Phycodrys austrogeorgica Skottsberg, the Arctic‐cold temperate Palmaria palmata (Linnaeus) O. Kuntze and the cosmopolitan Bangia atropurpurea (Roth) C. Agardh was studied. All four species showed a formation of ‘inside‐out’ vesicles from the chloroplast thylakoids upon exposure to artificial UV‐radiation. In P. decipiens, most vesicles were developed after 8 h and in P. palmata, after 48 h of UV exposure. In B. atropurpurea, vesi‐culation of thylakoids was observed after 72 h of UV irradiation. In Ph. austrogeorgica, the chloroplast envelope and thylakoid membranes were damaged and the phycobilisomes became detached from the thylakoids after 12 h of UV exposure. Ultraviolet‐induced changes in the membrane structure of mitochondria were observed in P. decipiens and P. palmata. However, in P. decipiens they were reversible as was the damage in chloroplast fine structure after 12 h of UV treatment. Protein crystals in Ph. austrogeorgica showed degradation after exposure to UV radiation. Different methods of fixation and embedding macroalgal material are discussed. These findings give insight into the fine structural changes which occur during and after UV exposure and indicate a relationship between the species dependent sensitivity to UV‐exposure and the depth distribution of the different species.     

Aphid orientation and performance in glasshouses under different UV‐A/UV‐B radiation regimes

Visual cues leading to host selection and landing are of major importance for aphids and evidence suggests that flight activity is very dependent on ultraviolet (UV)‐A radiation in the environment. At the same time research on insect plant hosts suggest that the UV‐B component can deter some pests via changes in secondary metabolite chemistry. Here, we examine the potential of UV (UV‐A/UV‐B) radiation to control insect pests in the glasshouse environment. We first examined artificial exposure to UV‐B and the potential to trigger morphological and biochemical modifications in pepper (Capsicum annuum L., Solanaceae) with implications for the fitness of green peach aphid, Myzus persicae Sulzer (Hemiptera: Aphididae). UV‐B caused accumulation of leaf secondary metabolites and soluble carbohydrates, and stimulated photosynthetic pigments. However, UV‐B did not impact on foliar protein content and aphid performance was unaffected. Next, we studied how altering the UV‐A/UV‐B ratio environment affected aphid orientation and spatial distribution over time, either directly or by exposing plants to supplemental UV before insect introduction. Aphids directly settled and dispersed on their host pepper plants more readily in the presence of supplemental UV‐A and UV‐B. In the control treatment with ambient glasshouse UV‐A and UV‐B, insects remained more aggregated. Furthermore, insects were less attracted to peppers pre‐exposed to supplemental UV‐A and UV‐B radiation. Our results suggest that suppression of UV‐A and UV‐B inside the protected environment reduces aphid colonization and dispersal. Furthermore, application of moderate exposure of young pepper plants to supplemental UV‐B radiation could aid in protection from the colonization by phytophagous insects.