Osmotic measurements on stomatal cells ofCommelina communis L.

Summary Observations of aperture changes as sucrose is added to the solution bathing epidermal strips ofCommelina communis L. allow calculation of the osmotic changes required to open or close the stomatal pore, for comparison with changes in potassium content. With isolated guard cells, in strips in which all cells other than guard cells have been killed, the internal osmotic changes required are 83 mosmol kg^–1 m^–1 below 10m aperture, 129 mosmol kg^–1 m^–1 in the range 10–15 m, and 180 mosmol kg^–1 m^–1 above 15 m. For opening against subsidiary cell turgor in addition to guard cell turgor, in intact strips with live subsidiary and epidermal cells, these figures should each be increased by about 33 mosmol kg^–1 m^–1. A change in subsidiary cell turgor is magnified in its effects on the water relations of the guard cell by a factor greater than 3.7 for equal changes in the water potential of the two cells, or greater than 4.7 at constant volume of the guard cell.     

The effect of avermectins on feeding,salivary fluid secretion,and fecundity in some ixodid ticks

We tested the effects of the potent acaricides, avermectin B₁a (AVM) and 22,23-dihydroavermectin B₁ (ivermectin; IVM) when injected directly into partially fed and fully engorged female ticks. When injected into small ticks (Amblyomma hebraeum Koch), neither drug (up to 100 g/kg b.w.) inhibited subsequent engorgement nor affected oviposition latency, weight of total egg mass laid nor viability of laid eggs. At higher concentrations (1000 and 5000 g/kg b.w.), AVM and IVM were markedly toxic. When injected into engorged ticks, both drugs increased oviposition latency, and reduced fecundity at about 75–100 g/kg b.w. Vitellogenesis, as assessed by a spectrophotometric assay of the ovaries, was not inhibited. Also at 50–100 g/kg b.w., AVM and IVM caused paralysis of the abdominal dorso-ventral muscles and the leg muscles. Both drugs, at 7 days post-injection, proved detrimental to salivary gland function in both small and large ticks, but had little effect on salivary gland weight. At concentrations which did not inhibit oviposition (20–50 g/kg b.w.) many of the eggs dried out even though they were kept at high RH. We then demonstrated inAmblyomma americanum, Dermacentor andersoni andD. albipictus that removal of egg wax (by extraction with hexane) induced a marked increase in water permeability. IVM neither increased water permeability ofD. andersoni eggs nor diminished the amount of egg wax deposited on the surface of the eggs, when injected posteriorly through the alloscutum. However, injection of IVM, dimethylsulphoxide (vehicle for IVM) or distilled water through the articulation between the capitulum and scutum (anterior injection), did markedly reduce the wax coating and increased egg permeability. We suggest that anterior injection damages Gené's organ and thus causes the latter effects.     

Rates of nitrification and carbon uptake in the Rhône River plume (northwestern Mediterranean Sea)

Nitrification rates were measured along a salinity gradient in the Rhône River estuary, using specific inhibitors (allylthiourea and chlorate) coupled with the measurement of change in nitrite concentration and inorganic carbon uptake by nitrifiers. Rates of ammonium and nitrite oxidation were similar up to 15 practical salinity units (from 1 to 2 mol N oxidized liter^-1 day^-1). For higher salinities, nitrite and ammonium oxidation rates were 0.14 and 0.23 mol N oxidized liter^-1 day^-1, respectively. Ammonium oxidizers assimilated 19–150 × 10–3 mol C liter^-1 day^-1, while nitrite oxidizers fixed 4.8–72.6 × 10–3 mol C liter^-1 day^-1. The amounts of nitrogen oxidized and C incorporated demonstrated a linear correlation (r ² > 0.99). The ratio of N oxidized to C incorporated ranged between 14.3 to 12.3 for ammonium oxidizers, and between 31.6 and 29 for nitrite oxidizers, the lower values being measured in seawater. Offprint requests to: M. Bianchi.     

Hormone studies inMyxine glutinosa: effects of the eicosanoids arachidonic acid,prostaglandin E1, E2, A2, F2α, thromboxane B2 and of indomethacin on plasma cortisol,blood pressure,urine flow and electrolyte balance

Summary Hagfish,Myxine glutinosa, were used in an investigation of the possible effects of various eicosanoids and the prostaglandin synthetase inhibitor indomethacin, on cortisol production, blood pressure control, urine flow and electrolyte balance.Cortisol levels in plasma of untreated control animals and plasma from animals 1 h following injection of 50 g kg^–1 prostaglandin E₁, E₂, A₂, F₂ TXB₂ and indomethacin were not detectable. However, plasma cortisol levels rose to between 10 and 26 pg ml^–1 1 h following injection of either 50 g kg^–1 arachidonic acid or prostaglandin E₂. This rise was similar in magnitude to that produced 1 h following administration of 50 g kg^–1 porcine ACTH.The resting dorsal aortic blood pressure of between 3.50 and 3.75 mmHg was reduced on average by 50% for 12–15 min when animals received 10 g kg^–1 arachidonic acid, prostaglandin E₁, E₂, A₂, and TXB₂ and was effectively reduced to zero for 20 min or more following 50 g kg^–1 of these eicosanoids. Similar doses of prostaglandin F₂, however, evoked an increase in blood pressure (19–33%) whilst indomethacin was without effect.Control measurements of urine flow inMyxine were estimated to be between 540 and 660 l h^–1 kg^–1. There was a marked reduction in urine output following the arterial vasodepression induced by arachidonic acid, prostaglandin E₁, E₂, A₂ and TXB₂ in doses of 10 g kg^–1, an effect which became even more pronouced following injection of 50 g kg^–1 quantities, leading in some cases to complete anuria. There was no significant change in urine volume following either the vasopressor action of prostaglandin F₂ or following indomethacin.None of the compounds tested in this study significantly influenced the plasma or urine electrolyte status ofMyxine.     

Effects of Cd and Zn on the development of annual xylem rings of young Norway spruce (Picea abies) plants

Three-year-old spruce (Picea abies) saplings were planted and cultivated for 2 years in pots with 3 1 substrate, consisting of a homogenized mixture of sand, peat and forest soil with a high organic content (volume ratio 11.52). This substrate was amended with 10–180 mol Cd [kg soil dry weight (DW)]^–1, 50–7500 mol Zn (kg soil DW)^–1 (determined with 1 M ammonium acetate extracts) or combinations of both elements. Annual xylem growth rings in stems of plants treated with 50 mol Cd (kg soil DW)^–1 or 7500 mol Zn (kg soil DW)^–1 were significantly narrower than in control plants. Growth reductions were more pronounced in the second year of the experiment. The contents of Cd and Zn in stem wood and needles were positively correlated with the substrate concentrations. The Mg contents of the spruce needles were inversely correlated with soil concentrations of Cd and Zn. Root development was impeded at moderate concentrations of Cd (50 mol kg^–1) or Zn (1000 mol kg^–1) in the substrate. The adverse effects of potentially toxic trace elements, like Cd or Zn, on xylem growth of spruce plants are discussed with regard to possible growth reductions in forest trees under field conditions.     

Underestimation of primary production as indicated by measurements with size-fractionated phytoplankton in Lake Maarsseveen I (The Netherlands)

Primary productivity of four size classes of phytoplankton (<150m, <50m, <20m and <5m) was measured from March through October 1986 in Lake Maarsseveen I with an incubator technique. The mean column production was approximately 400 mg C.m^–2.day^–1, with a range of values between 150 and 750 mg C.m^–2.day^–1. The mean contribution of the size fractions <50m, <20m and <5m to the size fraction<150m was 80%, 60% and 35%, respectively. During their appearance the grazing impact of small herbivorous zooplankton,e.g. rotifers, can give an underestimation of the size fraction <150m. An indication of this phenomenon is given.     

Production of C2 toxin by Alexandrium tamarense CI01 using different culture methods

The dinoflagellate Alexandrium tamarense CI01 wasgrown in three types of cultures: batch culture, semi-continuous culture andtemporary culture, to investigate the effects of different culture methods oncell growth and the productivity of C2 toxin (C2, a paralytic shellfish toxin).In the batch cultures, cells grew in three phases: a short lag phase, anexponential phase with a specific growth rate () of 0.78day^–1 and a relatively long stationary phase. Themaximum toxin productivity was 1.2 mol L^–1 or77 fmol cell^–1 in 9 days. In the semi-continuouscultures, cells grewin response to the dilution cycles, with values being 0.64, 0.32 and 0.35day^–1 for one-day, two-day and three-day cycles,respectively. The toxin yield was about one half of that of the batch cultures.A "temporary" culture method was used to maintain the metabolically activecellsremoved from the semi-continuous cultures, in a nutrient-depleted condition, toachieve a high toxin productivity of 1.0 molL^–1 in 4 days. Thus,the semi-continuous culture method provided an efficient means to generateamounts of metabolically active algal cells. The temporary culture offered aneffective way to produce C2. The highest yields of C2 were obtained in3–4days when the temporary cultures were aerated.     

Arsenic concentrations in water and fish from Chautauqua Lake,New York

Synopsis Arsenic persists in Chautauqua Lake, New York waters 13 years after cessation of herbicide (sodium arsenite) application and continues to cycle within the lake. Arsenic concentrations in lake water ranged from 22.4–114.81 g l^–1, = 49.0 ag l^–1. Well water samples generally contained less than 10 g l^–1 arsenic. Arsenic concentrations in lake water exceeded U.S. Public Health Service recommended maximum concentrations (10 g l^–1) and many samples exceeded the maximum permissible limit (50 g l^–1). Fish accumulated arsenic from water but did not magnify it. Fish to water arsenic ratios ranged from 0.4–41.6. Black crappie (Pomoxis nigromaculatus) contained the highest arsenic concentrations (0.14–2.04 g g^–1 ), X = 0.7 g g^–1) while perch (Perca flavescens), muskellunge (Esox masquinongy) and largemouth bass (Micropterus salmoides) contained the lowest concentrations (0.02–0.13 g g^–1). Arsenic concentrations in fish do not appear to pose a health hazard for human consumers.     

Accelerated degradation of <Emphasis Type="Italic">N,N′</Emphasis> (DBU) upon repeated application

In a recent study on the degradation of N,N-dibutylurea (DBU), a breakdown product of benomyl [methyl 1-(butylcarbamoyl)-2-benzimidazole carbamate], the active ingredient in Benlate^® fungicides, degradation half-lives of 1.4–46.5days were observed across several soils incubated at various combinations of soil moisture potential (–0.03 and –0.1MPa) and temperature (23, 33, and 44°C) for a single DBU application of 0.08 and 0.8 g g^–1 (Lee et al. 2004). However, Benlate^® can be applied as often as every 7days resulting in the repeated application of DBU likely to be present in the Benlate^® over a growing season. In this study, the effect of seven repeated DBU applications on mineralization rate was investigated in two soils, which encompass the range in rates previously observed. For the slower degrading soil, repeated DBU application increased mineralization from 0.029 to 0.99day^–1 at the 0.08 g g^–1 rate, and 0.037 to 0.89day^–1 at the 0.8 g g^–1 rate. For the faster degrading soil, effects on mineralization of repeated DBU applications were small to negligible. For the latter soil, the effect on mineralization of applied DBU concentrations from 0.0008 to 80 g g^–1 was also investigated. Mineralization rates decreased from 0.43 to 0.019day^–1 with increasing DBU concentrations. However, the amount of DBU mineralized by day 70 was similar across concentrations and averaged 83% of applied. Microbial respiration was not affected by increasing DBU concentrations. These findings support the supposition that DBU is readily degraded by soil microorganisms, thus unlikely to accumulate in agricultural soils.     

The contribution of size-fractionated plankton to biomass and primary production of phytoplankton in saline–alkaline ponds

Primary productivity, biomass and chlorophyll-a of size fractionated phytoplankton (<0.22 m, <3 m, <8 m, <10 m, <40 m, <64 m, <112 m and <200 m) were estimated in 6 ponds and 5 experimental enclosures. The results showed that the planktonic algae less than 10 m are important in the biomass and production of phytoplankton in saline–alkaline ponds. The production of size fractionated phytoplankton corresponding to <112 m, <10 m and <3 m in saline–alkaline ponds were 10.5 ± 6.6 , 8.6 ± 5.4 and 0.33 ± 0.1 mgC l^–1 d^–1, respectively. Mean community respiration rate was 1.80 ± 0.73, 1.69 ± 0.90 and 1.38 ± 1.12 mgC l^–1 d^–1, respectively. The average production of phytoplankton corresponding to micro- (10–112 m), nano- (3–10 m) and pico- (<3 m) were 1.61, 8.30 and 0.33 mgC l^–1 d^–1, respectively. The ratio of those to the total phytoplankton production was 15%, 79% and 3%, respectively. The mean respiration rate of the different size groups was 0.11, 0.31 and 1.38 mgC l^–1 d^–1; the ratio of those to total respiration of phytoplankton was 6%, 17% and 77%, respectively. The production of size-fractionated phytoplankton corresponding to <200 m, <10 m and <3 m in enclosures was 2.19 ± 1.63, 2.08 ± 1.75 and 0.22 ± 0.08 mgC l^–1 d^-1, respectively. Mean community respiration rates were 1.25 ± 1.55, 1.17 ± 1.42 and 0.47 ± 0.32 mgC l^–1 d^–1, respectively. The average production of phytoplankton corresponding to micro- (10–200 m), nano- (3–10 m) and pico- (<3 m) plankton was 0.11, 1.86 and 0.22 mgC l^–1 d^–1, respectively. The ratio of those to the total production of phytoplankton was 5%, 85% and 10%, respectively. The mean respiration rate of different size groups were 0.08, 0.72 and 0.46 mgC l^–1 d^–1, the ratio of those to total respiration of phytoplankton was 6%, 57% and 37%, respectively. The concentrations of chlorophyll-a of the phytoplankton in the corresponding size of micro- (10–112 m), nano- (3–10 m) and pico- (<3 m) plankton in the experimental ponds were 19.3, 98.2 and 11. 9 g l^–1, respectively. The ratio of those to the total chlorophyll-a was 15%, 76% and 9%, respectively. The concentrations of chlorophyll-a of phytoplankton micro- (10–200 m), nano- (3–10 m) and pico- (<3 m) plankton in enclosures were 1.7, 34.3 and 3.0 g l^–1, respectively. The ratio of those to the total chlorophyll-a was 4%, 88% and 8%, respectively.     

Photosynthesis and Water Use Efficiency in Twenty Tropical Tree Species of Differing Succession Status in a Brazilian Reforestation

Leaf gas exchange characteristics were measured in twenty woody species that differ in succession status ranging from pioneer species (PS) to late succession species (LS) in a Brazilian rain-reforestation ecosystem. Photon-saturated photosynthetic rate, calculated per either a leaf area (P _NA) or a dry mass (P _NM) basis, differed among species. P _NA and P _NM were highest in PS and lowest in LS. Variation among species was 3-fold (from 7 to 23 mol m^–2 s^–1) for P _NA, and 5-fold (from 50 to 275 mol kg^–2 s^–1) for P _NM. The highest P _NA (23 mol m^–2 s^–1) and P _NM (275 mol kg^–2 s^–1) values were recorded in PS Croton urucurana, while the lowest P _NA (7 mol m^–2 s^–1) and P _NM (50 mol kg^–2 s^–1) values were recorded in LS Aspidosperma cylindrocarpon. A considerable overlap was recorded between PS and LS in values of stomatal conductance (g _s), transpiration rate (E), and leaf mass to area ratio (ALM). However, C. urucurana also showed highest g _s and E. P _NM was highly correlated with ALM in both PS and LS (r=–0.75 and –0.90, respectively). The high values of instantaneous transpiration efficiency (ITE) and intrinsic water use efficiency (WUE_i) were also observed in the PS when compared with the LS.     

Occurrence of <Emphasis Type="Italic">Anonyx sarsi</Emphasis> (Amphipoda: Lysianassoidea) below Arctic pack ice: an example for cryo-benthic coupling?

During a winter expedition to the western Barents Sea in March 2003, benthic amphipods of the species Anonyx sarsi were observed directly below pack ice. Only males and juveniles [16.0–37.0 mm long, 16.2–120.8 mg dry mass (DM)] were collected. Guts contained macroalgal fibres, fish eggs and flesh from large carrion. Amphipods had very low levels of total lipids (2.7–17.2% DM). Analysis of lipid biomarkers showed that some of the specimens had preyed on pelagic copepods. Individual respiration rates ranged over 0.4–1.7 ml O₂ day^–1 (mean: 1.2 ml, SD: 0.5 ml). Individual ammonia excretion rates varied between 7.8 g and 49.3 g N day^–1 (mean: 30.7 g, SD: 15.2 g). The atomic O:N ratio ranged over 35 to 71 (mean: 55, SD: 14), indicating lipid-dominated metabolism. Mass-specific respiration ranged over 9.8–16.6 ml O₂ day^–1 g DM^–1 (mean: 13.1 ml, SD: 2.2 ml). The metabolic rates of A. sarsi were twice as high as those of the truly sympagic amphipod Gammarus wilkitzkii, which is better adapted to the under-ice habitat by its energy-saving attached lifestyle. It is concluded that males and juveniles of A. sarsi were actively searching for food in the water column and at the ice underside, but that the nutritional status of the amphipods in late Arctic winter was generally very poor.     

Calli and suspension cultures for biomass production ofEuphorbia characias L. subsp.characias

Summary Friable calli and cell suspension cultures were obtained from leaf segments ofEuphorbia characias L. subsp.characias, in Murashige and Skoog (MS) basal medium supplemented with 1g.l^–1 casein hydrolyzate (CH), 5mg.l^–1 ascorbic acid, 1.0mg.l^–1 2,4-dichlorophenoxyacetic acid (2,4-D) and 0.75mg.l^–1 benzyl adenine (BA). The highest callus specific growth rate (=0.085.day^–1), calculated for 1 year old calli cultures, was obtained with 0.25 mg.l^–1 2,4-D and 0.50mg.l^–1 BA. Suspension cultures started with an inoculum of 8.0×10⁴ cells.ml^–1 in supplemented liquid MS medium, gave a specific growth rate =0.256.day^–1.     

Procedures for the axenic isolation of conchocelis and monospores from the red seaweed Porphyra yezoensis

In order to maintain axenic seedstock cultures axenically of thecommercially important red seaweed, Porphyra yezoensis, aprocedure was developed for axenic isolation and culture of conchocelis andmonospores. For axenic isolation of the conchocelis, contaminated microalgaewere most effectively removed by filtering contaminated samples through a100-m mesh after sonication. Removal of bacteria and otheralgaewas accomplished using a mixture of 5 agents (0.02% chitosan, 100 gml^–1 GeO₂, 10 gml^–1 ampicillin, 40 gml^–1 kanamycin and 200 gml^–1 streptomycin). Axenic single colonies wereisolatedfrom a semi-solid medium prepared from 1% transfer gel. After collectingmonospores from the 40–50% density layer on a percoll-gradient, removalofbacteria and fungi from the monospores was accomplished using a mixture of 5antibiotics (3.5 g ml^–1 nystatin, 2 mgml^–1 ampicillin, 400 gml^–1 kanamycin, 50 gml^–1 neomycin and 800 gml^–1 streptomycin). Axenic single juvenile blades wereisolated from a semi-solid medium prepared from 0.5% transfer gel.     

Increased taxane accumulation in callus cultures of Taxus cuspidata and Taxus × media by some elicitors and precursors

In Taxus cuspidata callus, vanadyl sulfate (10 mg l^–1) induced a high (146 g g^–1 dry wt) production of 10-deacetylbaccatin III in comparison to 7 g g^–1 dry wt of the control. The content of paclitaxel in this species increased from 16 g g^–1 to 74 g g^–1 dry wt when 20 mg phenylalanine l^–1 was used. In T. media, p-aminobenzoic acid induced the highest content of 10-deacetylbaccatin III (481 g g^–1 dry wt) versus 181 g g^–1 in the control. Paclitaxel increased from 89 to 139 g g^–1 dry wt after adding chitosan (20 mg l^–1) to the cultures.     

Contributions of three subsystems of a freshwater marsh to total bacterial secondary productivity

Rates of bacterial production were measured in the water column, on the surface of plant detritus, and in the surface sediments of a freshwater marsh in the Okefenokee Swamp, Georgia, USA. Bacterioplankton production rates were not correlated with several measures of quantity and quality of dissolved organic matter, including an index of the relative importance of vascular plant derivatives. Bacterioplankton productivity was high (mean: 63 g C liter^–1 day^–1) compared with rates reported for other aquatic ecosystems. Somewhat paradoxically, bacterial productivity on plant detritus (mean: 13 g C g^–1 day^–1) and sediments (mean: 15 g C g^–1 day^–1) was low relative to other locations. On an a real basis, total bacterial productivity in this marsh ecosystem averaged 22 mg C m^–2 day^–1, based on sample dates in May 1990 and February 1991. Marsh sediments supported the bulk of the production, accounting for 46% (May) and 88% (February) of the total. The remainder was contributed approximately equally by bacteria in the water column and on accumulated stores of plant detritus. Send offprint requests to: M. A. Moran.     

Filtering impacts of larval and sessile zebra mussels (Dreissena polymorpha) in western Lake Erie

Summary We assessed the feeding biology of veliger larvae of the introduced zebra mussel (Dreissena polymorpha Pallas) in laboratory experiments using inert microspheres as food analogues. Mean clearance rate on 2.87-m beads ranged between 247 and 420 L veliger^–1 day^–1. Clearance rate was unrelated to bead concentration up to 100 beads L^–1, but was positively correlated with veliger shell length. Clearance rates of Dreissena veligers are within the range of those reported for marine bivalve veligers of similar size and for herbivorous Great Lakes microzooplankton, but are orders of magnitude lower than those of settled, conspecific adults. The impact of settled zebra mussel grazing activities on phytoplankton stocks may be up to 1162 times greater than that exerted by veliger populations in western Lake Erie. Based on 1990 size-frequency distributions and associated literature-derived clearance rates, reef-associated Dreissena populations in western Lake Erie (mean depth 7 m) possess a tremendous potential to filter the water column (up to 132 m³ m^–2 day^–1) and redirect energy from pelagic to benthic foodwebs. Preliminary analyses indicate that chlorophyll a concentration is strongly depleted (<1 g L^–1) above Dreissena beds in western Lake Erie.     

Sequential kinetic parameter estimation of anaerobic fluidized bed bioreactor using an optimization technique

Mathematical model parameters for the methanogenic degradation of propylene glycol were estimated in a sequential manner by means of an optimization technique. Model parameters determined from an initial experimental data set using one bioreactor were then verified with the results from a second bioreactor. The proposed methodology is a useful tool to obtain model parameters for continuous flow reactors with completely mixed regime. Abbrevations: S – substrate concentration (mg COD l^–1); S _in – influent substrate concentration (mg COD l^–1); D _L – dilution rate (day^–1); – stoichiometric coefficients (ND); nx – number of microbial species (ND); X _S – fixed biomass concentration (mg biomass l^–1); X _L – suspended biomass concentration of (mg biomass l^–1); k _d – decay rate of biomass (day^–1); b _S – specific detachment rate of biofilm (day^–1); – specific growth rate of biomass (day^–1); _m – maximum specific growth rate of biomass (day^–1); K _S – half saturation constant (mg COD l^–1); K _I – inhibition constant (mg COD l^–1).     

Oscillations of algal biomass,nutrients and dissolved oxygen as a measure of ecosystem stability

Graphic presentation of weekly rates of change of algal biomass (expressed as chlorophyll a) and nutrient and dissolved oxygen concentrations can be regarded as harmonic oscillation motion. Maximum amplitudes of these oscillations provide a useful tool to assess the degree of stability of aquatic ecosystems in relation to their trophic state. Data sets from seven different lakes ranging from hypereutrophic to oligo-mesotrophic were processed using a computerized method. The high values of oscillation amplitudes of approximately 150 g l^–1 wk^–1 chlorophyll a, 500 g l^–1 wk^–1 ammonia nitrogen, 50 g l^–1 wk^–1 soluble reactive phosphorus and 10 mg l^–1 wk^–1 dissolved oxygen, indicated strong ecosystem instability, while low values of less than 10 g l^–1 wk^–1 of chlorophyll a, 20 g l^–1 wk^–1 ammonia nitrogen, 2 g l^–1 wk^–1 soluble reactive phosphorus, and 3 mg l^–1 wk^–1 dissolved oxygen represented a stable system. Oscillation amplitudes of the chlorophyll a values were found to be the most representative indicator of ecosystem stability.     

First survey on the natural occurrence of Fusarium mycotoxins in Bulgarian wheat

Wheat for human consumption (140 samples) was collected after harvest from all regions of Bulgaria. The 1995 crop year was characterized by heavy rainfall in the spring and summer months. The internal mycoflora of wheat samples was dominated by Fusarium spp. and Alternaria spp., and storage fungi were rarely present. The samples were analysed for contamination with Fusarium mycotoxins deoxynivalenol (DON), 3-acetyldeoxynivalenol (3-AcDON), 15-acetyldeoxynivalenol (15-AcDON), T-2 Toxin (T-2), diacetoxyscirpenol (DAS), and zearalenone (ZEA), using enzyme immunoassay methods. DON and ZEA were the predominant toxins, with a contamination frequency of 67% and 69%, respectively. The average levels of these toxins in positive samples were 180 g/kg (DON) and 17 g/kg (ZEA), maximum concentrations were 1800 g kg^–1 and 120 g kg^–1, respectively. Acetyl derivatives of DON, namely 3-AcDON and 15-AcDON, were found in 2.1 % and 0.7% of the samples, at at maximum level of about 100 g kg^–1. Only one sample was positive for T-2 (55 g/kg), DAS was not detected. This is the first report about the natural occurrence of a range of Fusarium mycotoxins in wheat for human consumption in Bulgaria.Abbreviations 3-AcDON 3-acetyldeoxynivalenol - 15-AcDON 15-acetyldeoxynivalenol - DAS diacetoxyscirpenol - DON deoxynivalenol - EIA enzyme immunoassay - T-2 T-2 toxin - ZEA zearalenone