Intact Thalli Research Articles

GC-MS analysis of petroleum ether extract of Notothylas indica Kashyap for detecting compounds with antifeedant properties

Bryophytes are remarkable group of terrestrial plants that have several adaptations against biotic and abiotic stresses. They are a hoard of metabolites that provide protection against microbes and herbivores. Mostly bryophytes remain untouched by insect larvae as evident from the intact thallus. This can be attributed to the antifeedant compounds present in bryophytes. The current study aims at elucidating the various volatile compounds present in the petroleum ether extract of Notothylas indica and to determine the possible compounds that provide antifeedant properties. Altogether 154 compounds have been detected by GC MS analysis. 25 compounds showed a similarity of above 80 % with the NIST library and hence are evaluated for possible antifeedant activities. Insect/larval deterrent activity in N. indica may be due to compounds like 2-ethylnaphthalene, caryophyllene, phytol, beta-ionine, tridecane, undecane, tridecene. Since diverse chemicals are present in the extract with potential novelties, there are probabilities of more antifeedant compounds. Segregation and characterization of these chemicals can pave way for documentation of novel chemicals that can be used as antifeedants, thereby reducing the use of chemical pesticides in controlling pest.

Melanisation in Boreal Lichens Is Accompanied by Variable Changes in Non-Photochemical Quenching.

Lichens often grow in microhabitats where they absorb more light than they can use for fixing carbon, and this excess energy can cause the formation of harmful reactive oxygen species (ROS). Lichen mycobionts can reduce ROS formation by synthesizing light-screening pigments such as melanins in the upper cortex, while the photobionts can dissipate excess energy radiationlessly using non-photochemical quenching (NPQ). An inherent problem with using fluorimetry techniques to compare NPQ in pale and melanised thalli is that NPQ is normally measured through a variously pigmented upper cortex. Here we used a dissection technique to remove the lower cortices and medullas of Lobaria pulmonaria and Crocodia aurata and then measure NPQ from the underside of the thallus. Results confirmed that NPQ can be satisfactorily assessed with a standard fluorimeter by taking measurement from above using intact thalli. However, photobionts from the bottom of the photobiont layer tend to have slightly lower rates of PSII activity and lower NPQ than those at the top, i.e., display mild “shade” characteristics. Analysis of pale and melanised thalli of other species indicates that NPQ in melanised thalli can be higher, similar or lower than pale thalli, probably depending on the light history of the microhabitat and presence of other tolerance mechanisms.

Less Than the Sum of Its Parts: Blade Clustering Reduces Drag in the Bull Kelp, Nereocystis luetkeana (Phaeophyceae).

Nereocystis luetkeana is a large, canopy-forming kelp that is commonly found in nearshore waters between Alaska and California. Despite regularly reaching lengths in excess of 30 m, this alga demonstrates a remarkable ability to endure hydrodynamically stressful environments without being dislodged by waves or currents. While morphological aspects of this kelp, including its long flexible stipe, have been shown to reduce drag, blade clustering has never been directly tested. In this study, we examined how the distinctive multi-bladed morphology of Nereocystis thalli limits drag in flow. We measured drag on whole kelps in a large recirculating flume and quantified how drag was affected by serial removal of blades. We then compared measured drag with predictions of "additive drag", which we defined as the sum of the drag that each blade experiences in isolation. We found that, on average, intact thalli experience only 37% of the predicted additive drag when subjected to a flow rate of 0.40-0.50 m · s-1 . Our results indicate that the subdivision of the photosynthetic area into multiple blades has a drag-reducing effect on Nereocystis thalli. We found drag increases less than proportionally with the cumulative area, meaning the contribution of individual blades to overall drag decreases with increasing blade number. That is, as thalli develop, each additional blade incurs a reduced hydrodynamic cost, perhaps lending insight into how thalli can grow so large.

Effects of the lichen Peltigera canina on Cucurbita pepo spp. pepo grown in soil contaminated by DDTs.

Lichens consisting of a symbiotic association of green algae or cyanobacteria and fungi are found in a variety of environmental conditions worldwide. Terricolous lichens, located in soils, affect the living and lifeless environment of the soil due to their effective secondary metabolite and enzymatic content. Terricolous lichens can increase the biological, chemical, and physical usefulness of soil. However, their effects in ensuring the bioavailability of contaminated soil are not known, especially on soil pollution caused by DDTs (p,p'-DDE, p,p'-DDD, p,p'-DDT). This research focuses on the effect of terricolous lichens on zucchini (Cucurbita pepo spp. pepo) grown in soil contaminated by DDTs, utilizing their secondary metabolite and enzymatic contents. Firstly, Peltigera canina, a terricolous lichen species, was added to soil contaminated by DDTs as powdered and intact thallus. After lichen addition to soil, zucchini was planted in. The oxidative stress and antioxidative enzyme activities of zucchini were measured. According to the results, P. canina treatments have a positive effect on the growth and development of zucchini, although oxidative stress was observed. Also, it was determined that powdered application had more effective results than intact thallus application.

Influence of environmental factors and exogenous nitrogen on nitrogen fixation by intact thallus and excised cephalodia of Peltigera aphthosa

The present study investigates the effects of various abiotic environmental factors: air humidity, moisture content, oxygen and exogenously supplied nitrogen on acetylene reduction by intact thallus and excised cephalodia of Peltgera aphthosa. Intact thallus and excised cephalodia of Peltigera aphthosa were incubated at various conditions of air humidity, moisture contents, oxygen tensions, and addition of exogenous nitrogen, and comparative nitrogen fixation by the intact thallus and excised cephalodia was used as a method for assessment. Acetylene reduction (nitrogen fixation) was enhanced at conditions of lowered oxygen tension and at initial addition of nitrogen to the medium. However, prolonged incubation of Peltigera aphthosa in the medium with combined nitrogen addition resulted in fluctuation of nitrogenase synthesis. Acetylene reduction rates were stimulated in an atmosphere of 100% relative humidity (RH) and moisture content range of 570-620% of dry weight of Peltigera aphthosa. The decrease of nitrogenase activity measurable by acetylene reduction of thallus after prolonged incubation in the medium with combined nitrogen addition shows susceptibility of the symbiosis (lichen) since the thallus showed signs of disintegration at this time. Furthermore, air humidity and moisture content of the thallus influenced nitrogenase synthesis of Peltigera aphthosa considerably on separation of cephalodia such approach decreased nitrogenase activity and also elicited differences in their response to the various treatments. Applicability of this technology would enhance plant sustainability and yield in agricultural farms.

Influence of environmental factors and exogenous nitrogen on nitrogen fixation by intact thallus and excised cephalodia of Peltigera aphthosa

Influence of environmental factors and exogenous nitrogen on nitrogen fixation by intact thallus and excised cephalodia of Peltigera aphthosa

Influence of environmental factors and exogenous nitrogen on nitrogen fixation by intact thallus and excised cephalodia of Peltigera aphthosa

Influence of environmental factors and exogenous nitrogen on nitrogen fixation by intact thallus and excised cephalodia of Peltigera aphthosa

A facile in vivo procedure to analyze metabolic pathways in intact lichens.

Lichen secondary metabolites show important biological activities as well as pharmaceutical and chemotaxonomic potential. In order to utilize such substances of interest, detailed knowledge of their biosynthetic pathways is essential. 13 CO2 -pulse/chase experiments using intact thalli of the lichen Usnea dasopoga resulted in multiple 13 C-labeled isotopologs in amino acids, but not in the dibenzofuran derivative usnic acid - one of the best-studied lichen metabolites, with considerable and renewed interest for pharmaceutical and lifestyle applications. Spraying an aqueous solution of [U-13 C6 ]glucose onto the thalli of U.dasopoga afforded a specific mixture of multiple 13 C-labeled isotopologs in usnic acid. One- and two-dimensional NMR analysis of the crude lichen extract corroborated the polyketide biosynthetic pathway via methylphloroacetophenone but not via phloroacetophenone. With usnic acid as an exemplar, we provide proof-of-principle experiments that can be used in general to study metabolic pathways and fluxes in intact lichens.

Reprint of Efficient fungal UV-screening provides a remarkably high UV-B tolerance of photosystem II in lichen photobionts

Lichen photobionts in situ have an extremely UV-B tolerant photosystem II efficiency (Fv/Fm). We have quantified the UV-B-screening offered by the mycobiont and the photobiont separately. The foliose lichens Nephroma arcticum and Umbilicaria spodochroa with 1: intact or 2: removed cortices were exposed to 0.7 Wm-2 UV-BBE for 4 h. Intact thalli experienced no reduction in Fv/Fm, whereas cortex removal lowered Fv/Fm in exposed photobiont layers by 22% for U. spodochroa and by 14% for N. arcticum. We also gave this UV-B dose to algal cultures of Coccomyxa and Trebouxia, the photobiont genera of N. arcticum and U. spodochroa, respectively. UV-B caused a 56% reduction in Fv/Fm for Coccomyxa, and as much as 98% in Trebouxia. The fluorescence excitation ratio (FER) technique comparing the fluorescence from UV-B or UV-A-excitation light with blue green excitation light using a Xe-PAM fluorometer showed that these photobiont genera did not screen any UV-B or UV-A The FER technique with a Multiplex fluorometer estimated the UV-A screening of isolated algae to be 13–16%, whereas intact lichens screened 92–95% of the UV-A. In conclusion, the cortex of N. arcticum and U. spodochroa transmitted no UV-B and little UV-A to the photobiont layer beneath. Thereby, the upper lichen cortex forms an efficient fungal solar radiation screen providing a high UV-B tolerance for studied photobionts in situ. By contrast, isolated photobionts have no UV-B screening and thus depend on their fungal partners in nature.

Efficient fungal UV-screening provides a remarkably high UV-B tolerance of photosystem II in lichen photobionts

Lichen photobionts in situ have an extremely UV-B tolerant photosystem II efficiency (Fv/Fm). We have quantified the UV-B-screening offered by the mycobiont and the photobiont separately. The foliose lichens Nephroma arcticum and Umbilicaria spodochroa with 1: intact or 2: removed cortices were exposed to 0.7 Wm-2 UV-BBE for 4 h. Intact thalli experienced no reduction in Fv/Fm, whereas cortex removal lowered Fv/Fm in exposed photobiont layers by 22% for U. spodochroa and by 14% for N. arcticum. We also gave this UV-B dose to algal cultures of Coccomyxa and Trebouxia, the photobiont genera of N. arcticum and U. spodochroa, respectively. UV-B caused a 56% reduction in Fv/Fm for Coccomyxa, and as much as 98% in Trebouxia. The fluorescence excitation ratio (FER) technique comparing the fluorescence from UV-B or UV-A-excitation light with blue green excitation light using a Xe-PAM fluorometer showed that these photobiont genera did not screen any UV-B or UV-A The FER technique with a Multiplex fluorometer estimated the UV-A screening of isolated algae to be 13–16%, whereas intact lichens screened 92–95% of the UV-A. In conclusion, the cortex of N. arcticum and U. spodochroa transmitted no UV-B and little UV-A to the photobiont layer beneath. Thereby, the upper lichen cortex forms an efficient fungal solar radiation screen providing a high UV-B tolerance for studied photobionts in situ. By contrast, isolated photobionts have no UV-B screening and thus depend on their fungal partners in nature.

Can Parietin Transfer Energy Radiatively to Photosynthetic Pigments?

The main role of lichen anthraquinones is in protection against biotic and abiotic stresses, such as UV radiation. These compounds are frequently deposited as crystals outside the fungal hyphae and most of them emit visible fluorescence when excited by UV. We wondered whether the conversion of UV into visible fluorescence might be photosynthetically used by the photobiont, thereby converting UV into useful energy. To address this question, thalli of Xanthoria parietina were used as a model system. In this species the anthraquinone parietin accumulates in the outer upper cortex, conferring the species its characteristic yellow-orange colouration. In ethanol, parietin absorbed strongly in the blue and UV-B and emitted fluorescence in the range 480–540 nm, which partially matches with the absorption spectra of photosynthetic pigments. In intact thalli, it was determined by confocal microscopy that fluorescence emission spectra shifted 90 nm towards longer wavelengths. Then, to study energy transfer from parietin, we compared the response to UV of untreated and parietin-free thalli (removed with acetone). A chlorophyll fluorescence kinetic assessment provided evidence of UV-induced electron transport, though independently of the presence of parietin. Thus, a role for anthraquinones in energy harvesting is not supported for X. parietina under presented experimental conditions.

The first insect-induced galls in bryophytes

Insect induced galls are not known from bryophytes. Here we report the first occurrence of such galls from thalli of a neotropical liverwort, Monoclea gottschei subsp. elongata (Marchantiophyta: Monocleaceae) from Peru. This is also the first report of animal-induced galls formed in modern thalloid liverworts. The gall-inducer is a species of the family Agromyzidae (Diptera). The galls are swellings, but are otherwise indistinguishable from intact thalli as their surface is neither ornamented nor sclerotized. The histology of the galls, however, suggested that abnormal cell growth and some differentiation occurred in the parenchymatous cells of the thalli during gall formation.

The influence of structural organization of epilithic and endolithic lichens on limestone weathering

AbstractHyphal penetration, mineral dissolution and neoformation at the lichen–rock interface have been widely characterized by microscopic and spectroscopic studies, and considered as proxies of lichen deterioration of stone substrates. However, these phenomena have not been clearly related to experimental data on physical properties related to stone durability, and the physical consequences of lichen removal from stone surfaces have also been overlooked. In this study, we combine microscopic and spectroscopic characterization of the structural organization of epi‐ and endolithic lichens (Caloplaca marina (Wedd.) Du Rietz, Caloplaca ochracea (Schaer.) Flagey, Bagliettoa baldensis (A.Massal.) Vězda, Porina linearis (Leight.) Zahlbr., Verrucaria nigrescens Pers.) at the interface with limestones of interest for Cultural Heritage (Portland Limestone, Botticino Limestone), with analysis of rock properties (water absorption, surface hardness) relevant for durability, before and after the removal or scraping of lichen thalli. Observations using reflected‐light and electron microscopy, and Raman analyses, showed lichen–limestone stratified interfaces, differing in the presence/absence and depth of lichen anatomical layers (lithocortex, photobiont layer, pervasive and sparse hyphal penetration component) depending on species and lithology. Specific structural organizations of lichen–rock interface were found to be associated with differential patterns of water absorption increase, evaluated by Karsten tube, in comparison with surfaces with microbial biofilms only, even more pronounced after the removal or scraping of the upper structural layers. Equotip measurements on surfaces bearing intact thalli showed lower hardness in comparison with control surfaces. By contrast, after the removal or scraping procedures, Equotip values were similar to or higher than those of controls, suggesting that the increasing open porosity may be related to a biogenic hardening process. Such counterposed patterns of porosity increase and hardening need to be considered when models relating lichen occurrence on limestones and biogeomorphological surface evolution are proposed, and to evaluate the consequences of lichen removal from stone‐built cultural heritage. Copyright © 2017 John Wiley & Sons, Ltd.

15N – nitrate uptake and nitrogen exchange in the bionts of the lichen Parmelia sulcata

Nitrate uptake and nitrogen inclusion into amino acids were studied in the intact thallus and isolated bionts of the lichen Parmelia sulcata with the aid of mass spectroscopic tracing of heavy isotope 15N. The isolated photobiont, the green algae Trebouxia sp. did not take up nitrate, whereas the mycobiont and intact thalli were enriched in 15N when incubated with Na15NO3. Pulse feeding experiments with intact thalli followed by separation of photobiont showed that the labelled nitrate was originally assimilated by the mycobiont and only after that was detected in the photobiont. The isolated mycobiont after pulse labeling excreted labeled compounds into the incubation medium. Amino acids were detected in the exudate. The quantities of two amino acids considerably exceeded those of the others. One was identified as alanine, the other could not yet be identified with certainty. Both of these high-quantity compounds were also much more enriched in 15N than the others. These two compounds are proposed to be the transport forms of nitrogen within the Parmelia sulcata thallus.

Leaf color is fine-tuned on the solar spectra to avoid strand direct solar radiation.

The spectral distributions of light absorption rates by intact leaves are notably different from the incident solar radiation spectra, for reasons that remain elusive. Incident global radiation comprises two main components; direct radiation from the direction of the sun, and diffuse radiation, which is sunlight scattered by molecules, aerosols and clouds. Both irradiance and photon flux density spectra differ between direct and diffuse radiation in their magnitude and profile. However, most research has assumed that the spectra of photosynthetically active radiation (PAR) can be averaged, without considering the radiation classes. We used paired spectroradiometers to sample direct and diffuse solar radiation, and obtained relationships between the PAR spectra and the absorption spectra of photosynthetic pigments and organs. As monomers in solvent, the spectral absorbance of Chl a decreased with the increased spectral irradiance (Wm(-2)nm(-1)) of global PAR at noon (R(2)=0.76), and was suitable to avoid strong spectral irradiance (λmax=480nm) rather than absorb photon flux density (μmolm(-2)s(-1)nm(-1)) efficiently. The spectral absorption of photosystems and the intact thallus and leaves decreased linearly with the increased spectral irradiance of direct PAR at noon (I dir-max), where the wavelength was within the 450-650nm range (R(2)=0.81). The higher-order structure of photosystems systematically avoided the strong spectral irradiance of I dir-max. However, when whole leaves were considered, leaf anatomical structure and light scattering in leaf tissues made the leaves grey bodies for PAR and enabled high PAR use efficiency. Terrestrial green plants are fine-tuned to spectral dynamics of incident solar radiation and PAR absorption is increased in various structural hierarchies.

Analysis of the cyanolichen Lichina pygmaea metabolites using in situ DART-MS: from detection to thermochemistry of mycosporine serinol.

Direct Analysis in Real Time DART-HRMS is here first applied to the detection of molecules from a lichen, Lichina pygmaea. The aim was to propose an innovative method of in situ detection of lichen secondary metabolites using the possibilities of elemental composition determination available when a DART source is interfaced with a TOF analyzer. Three kinds of samples have been submitted to DART ionization, i.e. an intact thallus, a powder obtained from the crushed lichen and an aqueous extract. In situ analysis of crushed lichen, yields an extensive chemical profile, comparable to what is obtained from the aqueous extract, comprising both major polar metabolites described in literature along with some other signals that could correspond to potentially unknown metabolites. One of the detected secondary metabolites, mycosporine serinol, underwent a dehydration reaction prior to its transfer in the gas-phase by DART ionization. The consideration of the thermal transfers involved in the DART ionization process and the possibility to record time-dependent mass spectra through the use of the TOF analyzer allowed establishing Arrhenius plots of this water molecule loss to obtain associated thermodynamic quantities. The low values of corresponding activation enthalpy (Δr‡Hm° of the order of 25 kJ mol(-1)) enabled formulating some assumption regarding a possible role of such metabolites in the lichen.

Arachidonic acid-dependent carbon-eight volatile synthesis from wounded liverwort (Marchantia polymorpha)

Eight-carbon (C8) volatiles, such as 1-octen-3-ol, octan-3-one, and octan-3-ol, are ubiquitously found among fungi and bryophytes. In this study, it was found that the thalli of the common liverwort Marchantia polymorpha, a model plant species, emitted high amounts of C8 volatiles mainly consisting of (R)-1-octen-3-ol and octan-3-one upon mechanical wounding. The induction of emission took place within 40min. In intact thalli, 1-octen-3-yl acetate was the predominant C8 volatile while tissue disruption resulted in conversion of the acetate to 1-octen-3-ol. This conversion was carried out by an esterase showing stereospecificity to (R)-1-octen-3-yl acetate. From the transgenic line of M. polymorpha (des6KO) lacking arachidonic acid and eicosapentaenoic acid, formation of C8 volatiles was only minimally observed, which indicated that arachidonic and/or eicosapentaenoic acids were essential to form C8 volatiles in M. polymorpha. When des6KO thalli were exposed to the vapor of 1-octen-3-ol, they absorbed the alcohol and converted it into 1-octen-3-yl acetate and octan-3-one. Therefore, this implied that 1-octen-3-ol was the primary C8 product formed from arachidonic acid, and further metabolism involving acetylation and oxidoreduction occurred to diversify the C8 products. Octan-3-one was only minimally formed from completely disrupted thalli, while it was formed as the most abundant product in partially disrupted thalli. Therefore, it is assumed that the remaining intact tissues were involved in the conversion of 1-octen-3-ol to octan-3-one in the partially disrupted thalli. The conversion was partly promoted by addition of NAD(P)H into the completely disrupted tissues, suggesting an NAD(P)H-dependent oxidoreductase was involved in the conversion.

Water-soluble phenolic compounds in lichens

The quantity and the qualitative composition (for some species) of phenolic compounds (PC) washed out of the intact thalli of lichens of the orders Peltigerales (the genera Peltigera, Solorina, and Nephroma) and Lecanorales (the genera Cladonia, Alectoria, and Cetraria) were studied. It was shown that the quantity of leachable PCs in Peltigerales was on average 2–3 times higher than in Lecanorales. At the same time, the extractability of PC from intact thalli by water was higher in Lecanorales than in Peltigerales: 48–88% and 34–70%, respectively, of the PC content in ethanol extracts from crushed thalli (i.e., of the total content of soluble PC). Water-soluble PC in the lichens Peltigera aphthosa, Solorina crocea, Cetraria islandica, Flavocetraria nivalis, Cladonia uncialis, and Cladonia arbuscula were represented by 7–12 phenolic compounds with similar qualitative composition in the species of the same order. The most part of water soluble PC were phenylpropanoids. All of the studied species showed the presence of p-hydroxybenzoic acid derivatives; vanillic and protocatechuic acid derivatives were found in Cetraria and Cladonia species, respectively.

Weathering and particle entrapment at the rock–lichen interface in Italian volcanic environments

The present work investigated the biogeophysical and biogeochemical weathering associated to the growth of epilithic lichens on recent lava flows from Mt. Etna (Sicily) and Mt. Vesuvius (Campania). The chosen lichen species were the crustose Lecidea fuscoatra, the foliose Xanthoparmelia conspersa and the fruticose Stereocaulon vesuvianum. An integrated approach based on the study of both disturbed and undisturbed samples of lichenized rock was applied in order to allow for the complexity of the rock–lichen interface environment in terms of micromorphological, mineralogical and chemical properties. To this aim, a number of rock blocks colonised by intact thalli of different lichen species were collected in order to have at least 10 thalli for each species in each environment. XRD and XRF analyses coupled to microscopic (OM), submicroscopic (SEM) and microanalytical (EDS) observations were the used techniques. In both study environments, the chemical, mineralogical and micromorphological properties of the incoherent materials found at the rock–lichen interface suggested that they mostly consist of rock fragments eroded from the surroundings and accumulated in cavities and fissures of the rough lava flows. According to the thallus morphology, the lichens colonising the lava preserve the interface materials from further wind and water erosion, provide such materials with organic matter and moisture, and entrap allochthonous quartz, sea salts, iron oxides and clay minerals. Calcium oxalate production by L. fuscoatra and X. conspersa, Al enrichment around S. vesuvianum hyphae and iron accumulation at the interface constitute evidence of lichen interaction with the underlying sediments. Larger differences between rock and interface materials occur at Vesuvius vs Etna site. In line with the young age of the lavas, recent lichen colonisation only results in a physical reorganisation and slight chemical modification of the materials accumulated at the rock–lichen interface, whose abundance should not be considered an indicator of bioweathering. In volcanic environments, the ability of lichens to retain a considerable amount of unconsolidated material.

Dispersal potential of the invasive green alga Codium fragile ssp. fragile

Since its introduction in 1989, the invasive green alga Codium fragile ssp. fragile (formerly Codium fragile ssp. tomentosoides) has spread rapidly in Atlantic Canada. Although its spread has likely been facilitated by human transport, C. fragile possesses diverse modes of natural dispersal. In addition to parthenogenetically developing swarmer cells, it can propagate through the release of vegetative buds, thallus fragments, and entire, dislodged thalli. We examined the natural dispersal potential of these propagules using a combination of field and laboratory experiments. Vegetative buds were most abundant on thalli in late August, coinciding with increasing late summer wave activity. At two locations within two field sites, we examined the effects of tidal state, wave action and topography on the dispersal of fragments and intact thalli. Over a 4-hour period, retention rate was generally lower and dispersal distance of retained propagules higher: during flood than ebb tide; at the more wave-exposed locations; and for fragments than thalli. Dispersal direction corresponded with topography or flood tide currents at certain locations, but was often bi-directional or random, suggesting an added role of wave action. Over periods of weeks, the retention rate of marked detrital thalli was negatively related to the magnitude of wave activity. In the laboratory, settling rate was negatively related to propagule length, and large buds had higher critical shear erosional velocities than either small buds or fragments. Our results indicate that large propagules of C. fragile, such as intact adult thalli, have a generally low dispersal potential (meters), but may be transported longer distances (kilometers) during storms or when positively buoyant. Fragments and buds are regularly transported 10's of meters at a time at average flow velocities. However, they also become resuspended in average flows, and probably disperse longer distances over multiple resuspension events, or when positively buoyant. Once settled, the smallest propagules may be less easily resuspended or transported along the bottom as they become entrapped by small-scale topographic features or turf algae. The wide variety of propagules produced by C. fragile and the variable distances over which different propagule types may be transported give C. fragile the advantage of both short- and long-distance dispersal, and have likely played a role in the invasive success of this alga.