Ulva Thalli Research Articles

X-ray Fluorescence Techniques in Determining the Habitat Preferences of Species-Ulva pilifera (Ulvales, Chlorophyta) from Montenegro Case Study.

The paper presents four new sites where bright green Ulva thalli were found inhabiting freshwater (a river, a ditch, the Milet Canal) and marine (on the rocky shore of the Adriatic Sea) habitats in Montenegro. The aims of this study were to determine, for the first time, whether specimens of Ulva pilifera collected in Montenegro are phylogenetically and morphologically the same species as the one occurring in Europe. Using total reflection X-ray fluorescence (TXRF) and wavelength dispersive X-ray fluorescence (WDXRF) techniques it assessed the elemental composition of their thalli and its influence to colonise new habitats. Elements: Al, As, Ba, Br, Ca, Cl, Cr, Cu, Fe, Hf, I, K, Mg, Mn, Na, Ni, P, Pb, Rb, S, Si, Sr, Ti, V, and Zn were determined. The highest elemental concentrations were found for Ca = 16.3% (using WDXRF) and for Sr = 292 ppm (using TXRF) in the Ulva thalli. Ulva pilifera analysed from Montenegro, based on classical morphological methods and molecular techniques, are closely related to the same species from inland and coastal waters throughout Europe. The analysis of trace elements showed that the metal content in Ulva thalli is correlated with the trace elements in water and sediments. Ulva pilifera fits numerous features that make it one of the bioindicators of marine pollution, thanks to its worldwide distribution and capacity to accumulate trace elements.

Macroalgal blooms caused by marine nutrient changes resulting from human activities

Abstract Macroalgal blooms (green tides) are occurring more frequently in many regions of the world, leading to significant impacts on marine ecology and economies. Although many studies and hypotheses have been proposed, the exact mechanism of green tide formation remains unclear. The world's largest green tides recur in the Yellow Sea and this area is representative for studying the origin and mechanism of green tide formation. We conducted a meta‐analysis of studies related to green tides and associated hypotheses for their formation. Rapid industrialization/urbanization and environmental protection actions in coastal zones have led to an increase in nitrate (nitrite) and decline in ammonium (ammonia), and this has resulted in increasing levels of dissolved inorganic nitrogen in seawater. We found that presence of appropriate attachment substrates for Ulva including laver culture rafts and certain hydrological conditions are supplementary factors to green tide formation in the Yellow Sea. Changes in marine nutrient levels promote the production of nitric oxide, which is essential for Ulva sporulation. Consequently, numerous spores are created and attach to substrates including laver culture rafts and parent Ulva thalli. These spores then develop into new thalli that are capable of producing further spores. As a result, Ulva thalli rapidly occupy vast areas of the sea and develop into green tides. Synthesis and applications. Our synthesis identifies that escalating marine nitric oxide generation caused by various factors and its essential role in Ulva sporulation are underlying and significant components in the mechanism of green tide formation. We provide solutions such as the improvement of comprehensive management of aquaculture and strict restriction of marine nitrate pollution, to prevent green tides. Furthermore, we propose an innovative wastewater treatment programme combined with Ulva application to fulfil the standard of sustainable development and circular economy.

Assessment of Trace Metal Accumulation in Green Algae Ulva from the South Eastern Coast of Tunisia

Assessment of Trace Metal Accumulation in Green Algae Ulva from the South Eastern Coast of Tunisia In the present study we aimed to assess the heavy metal accumulation (Fe, Zn, Cu, Pb, Cd and Mn) in Ulva lactuca thalli, as well as in sediments and seawater. Samples were collected from three sites along the southeastern coastline of Tunisia (S1: Dkhila coast, S2: Zarrat, and S3: Gulf of Gabes). The data obtained showed different patterns of metal accumulation. In fact, samples collected from Dkhila (S1) accumulated the highest Cd levels compared to the other sites. Regarding Zn, the S3 and S2 sites displayed the highest accumulation amounts in the following decreasing order: sediment>seawater>algae. For Cu, S1 showed the most significant concentrations according to this order: sediment>seawater>algae followed by S3 seawater. Likewise, data showed that Ulva thalli accumulated high levels of Fe for all sites. Taken together, these data demonstrate that the Gulf of Gabes accumulates the largest amount of Zn in sediments, whereas the highest levels of Cd were found in Dkhila coast, particularly in algae and sediments.

Spatial and temporal variation in algal epiphyte distribution on Ulva sp. (Ulvales, Chlorophyta) from northern Patagonia in Argentina

:In this study of northern Patagonia in Argentina, we examined the annual cycle of the epiphyte composition and abundance on Ulva sp. with respect to intertidal elevation, season and position on host. We found spatial segregation in most environmental gradients. Local environmental conditions, intertidal levels, seasons and portion of host thalli had specific patterns of algal epiphytic community. The host population exhibited seasonality and differential morphological attributes according to the intertidal elevation. Thalli of Ulva sp. had the highest maximum diameters and were heavier in spring and summer at the upper elevation. Epiphytes were more abundant growing on host thalli at middle elevations. Epiphytic Dinophyceae, Chlorophyceae and Cyanophyceae presented clear seasonality. Epiphyte abundances were related to periods with high seawater temperature, long days and high radiation. Lyngbya sp., Cocconeis sp., Navicula spp., Rhabdonema arcuatum, Stylonema alsidii and Myrionema strangulans had the highest frequency. The highest epiphyte abundance was observed in holdfasts, with M. strangulans having the highest frequency and cover. These results are relevant to commercial aquaculture ventures for food and feed sources and application in bioremediation.

Ecological preferences of freshwater Ulva flexuosa (Ulvales; Ulvophyceae): development of macroalgal mats in a Tulce fishpond (Wielkopolska Region, Poland)

Abstract Research on the diversity of thalli and mats built by freshwater Ulva flexuosa, as well as the impact of abiotic factors on the development and distribution of Ulva mats, was conducted from May to August 2013. The study describes the dynamics of “green tides” formation by U. flexuosa. The study assessed abiotic factors that may influence the colonization and the growth of Ulva populations in freshwater systems. The results are of major importance to the trade and industry sectors. In total, eleven environmental parameters were included in the analysis. The most important environmental parameters characterizing the Ulva sites are sodium chloride levels and conductivity. High values of pH inhibited the development of Ulva, leading to a lower percentage of mature thalli in the mats. The water depth was positively correlated with an increase in the density of thalli in the mats and the average thallus length. Significant differences were identified between the concentrations of nitrates under and outside the Ulva mats. Concentrations of nitrate under the Ulva thalli were always lower.

Ulva flexuosa subsp. pilifera (Chlorophyta, Ulvophyceae) from the Wielkopolska region (West Poland): a new observation on the ultrastructure of vegetative cells

Abstract Ulva flexuosa subsp. pilifera previously known from northern Poland, from the channel near Szczecin and ponds near Łódź, has recently been found in the Malta Reservoir in the Wielkopolska (West Poland) region. Specimens collected in the Wielkopolska region were examined in detail, also under a transmission electron microscope (TEM). The morphometric analysis of Ulva thalli (both young and mature specimens) was performed in order to study the differences in the ultrastructure of vegetative cells. Rectangular cells in young thalli measured from 32.21–55.81 μm to 20.24–35.12 μm, and they formed clear longitudinal rows, while cells in the mature specimens ranged from 25.09–47.66 μm to 18.90–31.56 μm. This study indicates that vegetative cells of the mature thalli show tendency towards distortions of both the longitudinal and transverse cells arrangement. This distortion is determined by the development of possible carbonate calcium crystals on the thalli surface. The ultrastructural analysis (TEM) confirmed that the structure and placement of thylakoids is genus/species specific.

The accumulation of metal (Co, Cr, Cu, Mn and Zn) in freshwater Ulva (Chlorophyta) and its habitat

The possibility of using freshwater Ulva (Chlorophyta) as a bioaccumulator of metals (Co, Cr, Cu, Mn and Zn) in lake and river water was examined weekly in the summer of 2010 in three types of samples: the water, the sediment and the thalli of Ulva. Samples of freshwater Ulva were collected from two aqueous ecosystems lie 250 km away from the basin of the Baltic Sea and 53 km from each other. A flow lake located in the centre of the big city was the first water reservoir (ten sites) and second, the suburban river (six sites). The mean metal concentrations in the Ulva tissue from the river and the lake decreased in the following order: Mn > Zn > Cr > Cu > Co and Mn > Cr > Zn > Cu > Co, respectively. Moreover, a negative and statistically significant correlation between Mn concentrations in the Ulva thalli and the river water was observed. Additionally, numerous correlations were noted between the different concentrations of metals within the Ulva thalli, in the water and in the sediment. The great concentrations of Mn and Zn and the smallest of Co were found in thalli of Ulva, irrespective of the type of the ecosystem from which samples of algal thalli originated. Freshwater Ulva populations examined in this study were clearly characterized a dozen or so times by the higher Mn and Cr accumulation than taxa from that genera coming from sea ecosystems. The calculated bioconcentration factor confirm the high potential for freshwater Ulva to be a bioaccumulator of trace metals in freshwater ecosystems.

大阪湾阪南2区干潟創造実験場における流れとミナミアオサの分布

Field surveys were carried out to clarify the effect of geographical features and currents on the distribution of green-tide forming seaweed, Ulva ohnoi at the artificial tidal flat of Hannan Second District in 2011-2012. Thalli of Ulva accumulated on the northern part of the flat due to the tidal current on the flood tide. In contrast, they did not move from the north to the south of the flat because of the slow current on the ebb tide. Wind-driven currents also acted as a factor for the accumulation of Ulva on the flat. The water route was thought to play an important role on the accumulation or dispersion of Ulva at the artificial tidal flat of Hannan Second District.

Concentrations of phytochelatins and glutathione found in natural assemblages of seaweeds depend on species and metal concentrations of the habitat

The occurrence of the metal-complexing thiol peptides, phytochelatins (PC) in natural populations of brown, red and green seaweeds (marine macroalgae) was studied. Concentrations of PCs and their precursor glutathione (GSH) were measured in seaweeds collected from locations in south-west England with different levels of contamination by trace metals, to evaluate their role under natural environmental conditions. The non-protein thiols were identified and quantified in seaweed extracts by HPLC and the molecular structures of PCs were confirmed by LC–ESIMS. The capacity for production of PCs of representative seaweeds under Cd and Zn exposure was also assessed, experimentally. The concentrations of metals/metalloids (As, Cu, Cd, Pb and Zn) accumulated by the seaweeds were determined by ICP-MS. For the first time, PCs are reported in native Phaeophyceae ( Fucus spp.), Rhodophyceae ( Solieria chordalis) and Chlorophyceae ( Rhizoclonium tortuosum) but not in thalli of Ulva spp. and Codium fragile (Chlorophyceae). The concentrations of PCs in brown and red seaweeds correlated with the contamination history of sampling sites and total metal burden of thalli. The highest concentrations of metals (5.6–7.1 μmol g −1 DW), PCs (200–240 nmol SH g −1 DW) and GSH (1550–3960 nmol SH g −1 DW), and the longest PC chain lengths (PC 2–4) were found in Fucus spp. collected from the most contaminated site. A combination of PC-production and maintenance of high concentrations of GSH allows Fucus spp. and R. tortuosum (2000 nmol GSH g −1 DW) to thrive in highly contaminated environments whereas in Ulva spp. high concentrations of GSH (1000–1500 nmol SH g −1DW) together with thick cells walls and a high polysaccharide content appear to be responsible for metal-resistance. The lack of production of PCs in these green macroalgae suggests lower intracellular metal accumulation rather than an inability for synthesizing PCs. The higher concentrations of Cu (approximately 3.4 μmol g −1 DW) found in thallus of S. chordalis, compared with the Fucus spp. (1.5–2.4 μmol g −1 DW) from the same site, may induce stronger oxidative stress and result in lower concentrations of reduced glutathione (648 nmol SH g −1 DW) and PCs (70 nmol SH g −1 DW). As a consequence S. chordalis at this site may have a lower resistance to metals and a more restricted distribution than the fucoids. Both fucoid species and the red seaweed Gracilaria gracilis, but not Ulva spp. or C. fragile, from low contaminated sites synthesized PCs under laboratory conditions when exposed to very high concentration of Cd. Our results clearly show that natural assemblages of seaweeds, belonging to disparate phylogenetic groups produce PCs when exposed to a mixture of metals in their environment. However, the involvement of thiol peptides in metal homeostasis, detoxification and resistance varies between seaweed species that are growing under the same environmental conditions.

Recycle of buried macroalgal detritus in sediments: use of dual-labelling experiments in the field

In intertidal sediments, burial and decomposition of macroalgal detritus can fuel the sediment of carbon (C) and nitrogen (N), which can be either promptly mineralised or assimilated to enter the food web. This study investigates the transfer of algal-derived C and N to the sediment and to the infauna feeding primarily on benthic diatoms. Thalli of Ulva spp. were 13C- and 15N-labelled in the mesocosm and frozen to create detritus. Thawed macroalgae were, then, buried in the sediment of an intertidal sand-flat forming a mosaic of small patches (50 × 50 cm2) enriched with the macroalgae interspersed with bare sediment. The area was dominated by Corophium volutator and Hydrobia ulvae. The uptake of 13C and 15N was measured in the residual macroalgae, in the sediment and in those animals. Decomposition of detritus was rapid and after 4 weeks the residual biomass was 3% the amount added. Algal-derived 13C and 15N were moved to the sediment. The total amount of 13C and 15N retained in the sediment after completing the decomposition was 3.4 ± 0.5% 13C and 2.7 ± 0.6% 15N the amount decomposed. During the first 2 weeks more N than C was assimilated (1.7% 13C and 13.5% 15N). During the remaining two weeks, N was released from the sediment, while there was little accumulation of C (+6.4 ± 2.0 % 13C and −7.7 ± 3.8% 15N). At the end of the decomposition, animals were 15N- and 13C-labelled. Considering the total accumulation of label in the sediment, they accounted for 3.5 ± 1.8% 13C and 25.8 ± 12.9 % 15N. Similarly, considering the mass of the heavy isotopes gained (13C) or lost (15N) during the remaining 2 weeks, the animals accounted for 4.7 ± 2.1% of the 13C in excess and for 18.6 ± 9.1% of the 15N loss. The transfer of C and N to the sediment and to the surface deposit-feeders can be a relevant mechanism to remove the excess of detritus from the sediment.

Reduction of land based fish-farming impact by phytotreatment pond system in a marginal lagoon area

Intensive land-based fish farming facilities discharged wastewaters into an inlet of the Orbetello lagoon (Southern Tuscany, Italian West Coast), producing large blooms of the green macroalga Ulva rigida C. Ag., accompanied by dystrophic crises. Enclosing a part of this critical inlet resulted in a new pond for phytotreatment of the fish-farming effluents. Between June 1998 and May 1999 a trial study was carried out, during the daylight, in order to: a) define the changes in the wastewater physico-chemical parameters after discharge through the phytotreatment, b) quantify the removal of nitrogen and phosphorus, c) estimate the efficiency of U. rigida biomass produced within the pond in reducing wastewater nutrient loads. During the test period the water physico-chemical parameters were recorded; water dissolved nitrogen (N) and phosphorus (P), Ulva thalli total N and P (UTN, UTP) and macroalga biomass were determined. The results indicated that: 1) the phytotreatment system affected greatly pH and DO values and it reduced thermal impact on the lagoon; 2) the wastewater inorganic nutrient loads were reduced significantly while dissolved organic components (DON and DOP) were not meaningfully lowered; 3) the diurnal nutrients removal was not directly due to U. rigida uptake because the biomass produced annually stored only 1.63% and 0.91% of the dissolved inorganic N (DIN) and P (SRP) inflow values, respectively. Inefficiency of phytotreatment action was probably due to the drop of U. rigida nutrient uptake owing to high macroalgae density inside the pond. Therefore, other processes must be taken into account to explain N and P abatements, such as ammonia volatilization and nitrification/denitrification for N, and the precipitation of insoluble compounds for P.

Nutrient and iron limitation to Ulva blooms in a eutrophic coastal lagoon (Sacca di Goro, Italy)

Growth patterns and bloom formation of the green seaweed Ulva rigida were analysed in the eutrophic Sacca di Goro lagoon (Po River Delta, Italy). Variations of standing biomasses and elemental composition of Ulva were analysed through an annual cycle with respect to nitrogen, phosphorus and iron. Growth rates, nutrient and iron uptake and nitrate storage by macroalgal thalli were also assessed with field experiments during the formation of a spring bloom. The control of Ulva growth and the bloom formation depended on multiple factors, especially on nitrogen availability and iron deficiency. In the nitrate rich waters of the Sacca di Goro lagoon, nitrate accumulation in Ulva thalli was inversely related with Fe uptake, indicating an influence of Fe limitation on N acquisition. Since length and magnitude of nitrate luxury uptake are inversely related to the size of the intracellular nitrate pools, in nitrate rich waters the fast growing Ulva may face risk of N-limitation not only when exposed to low N concentrations or at high biomass levels, but also when exposed to pulsed dissolved nitrate concentrations at low iron availability. The potential Fe limitation could be affected by processes controlled by geochemical reactions and by macroalgal growth and decomposition. Both Fe oxidation during the active macroalgal growth and the formation of insoluble FeS and FeS2 during bloom collapse can result in a drastic decrease of soluble iron. Thus, a potential limitation of Fe to macroalgae can occur, determining positive feedbacks and potentially controlling the extent of bloom development and persistence.

Crossing test among floating Ulva thalli forming `green tide' in Japan

Crossing test among floating Ulva thalli forming `green tide' in Japan

SEASONAL VARIATION OF PHOTOSYNTHETIC PERFORMANCE AND LIGHT ATTENUATION IN ULVA CANOPIES FROM PALMONES RIVER ESTUARY1

The primary production of Ulva populations relies on their photosynthetic performance, which is dependent on the light availability under natural conditions. This study concerns the light attenuation characteristics in Ulva canopies and the seasonal photosynthetic performance of two different species (Ulva rotundata Blid., Ulva curvata (Kutz.) De Toni) blooming in the Palmones river estuary. Light within canopies differed from that reaching the surface. Light availability was reduced through the water column (at high tide) and Ulva canopies. In addition, light was spectrally filtered. As a result, the photosynthetically usable radiation (PUR) was further attenuated through Ulva canopies, increasing the photosynthetically active radiation/PUR ratio. The muddy sediment deposited on and between the Ulva thalli also drastically restricted the light availability. Thick Ulva mats are frequently found covering the intertidal mudflats, and therefore, thalli within these mats may be subjected to steep light gradients. As a consequence, individual Ulva growth rates cannot be extrapolated to estimate the primary production of Ulva canopies. Interspecific differences were observed for light-saturated photosynthetic rates (Pmax) and light compensation points (LCP), with Ulva curvata generally displaying higher values than did U. rotundata. For both species, maxima were recorded in winter for Pmax, quantum yield, chlorophyll content, and absorptance, whereas minima were found in summer. Dark respiration (Rd) was not seasonally affected, and a maximum LCP was found in summer. To extrapolate these data to field situations, the temperature dependence of photosynthesis should be considered. The Q10 values were 2.44 for Rd and 1.79 for Pmax, whereas the photosynthesis rate at subsaturating light levels was unaffected. The Q10 values showed an enhanced respiratory rate in summer and a minimum in winter, whereas the seasonal differences on Pmax were damped.

Growth of the seaweed Ulva rigida C. Agardh in relation to biomass densities, internal nutrient pools and external nutrient supply in the Sacca di Goro lagoon (Northern Italy)

Growth of the seaweed Ulva rigida C. Agardh was investigated in relation to biomass densities, internal nutrient pools and external nutrient supply. Research was carried out from 23 March to 5 July 1994 in the Sacca di Goro (Po Delta, Northern Italy), whose south-eastern part was covered by extensive mats of Ulva rigida. Two types of field experiments were conducted by incubating Ulva thalli inside large cages. In the first experiment, beginning on 23 March, 100 g of wet thalli were placed into the cages, allowed to grow for two weeks, then collected and replaced. This procedure was repeated 8 times over the study period. In the second experiment, Ulva thalli were left inside the cages and collected at selected time intervals (14, 27, 41, 64 and 76 days) in order to simulate the effects of increased density on growth and nutrient storage.

PHOTOSYNTHETIC PROPERTIES OF PROTOPLASTS, AS COMPARED WITH THALLI, OF ULVA FASCIATA (CHLOROPHYTA)1

ABSTRACTProtoplasts were prepared from Ulva fasciata Delile, and their photosynthetic performance was measured and compared with that of thalli discs. These protoplasts maintained maximal rates of photosynthesis as high as those of thalli (up to 300 μmol O2·mg chlorophyll−1·h−1) for several hours after preparation and were therefore considered suitable for kinetic studies of inorganic carbon utilization. The photosynthetic K1/2(inorganic carbon) at pH 6.1 was 3.8 μM and increased to 67, 158, and 1410 μM at the pH values 7.0, 7.9, and 8.9, respectively. Compared with these protoplasts, thalli had a much lower affinity for CO2 but approximately the same affinity for HCO3−. Comparisons between rates of photosynthesis and the spontaneous dehydration of HCO3− (at 50 μM inorganic carbon) revealed that photosynthesis of both protoplasts (which lacked apparent activity of extracellular/surface‐bound carbonic anhydrase) and thalli (which were only 25% inhibited by the external carbonic anhydrase inhibitor acetazolamide) could not be supported by CO2 formation in the medium at the higher pH values, indicating HCO3− uptake. Since both protoplasts and thalli were sensitive to 4,4′‐diisothiocyanostilbene‐2,2′‐disulfonate, we suggest that HCO3− transport was facilitated by the membrane‐located anion exchange protein recently reported to function in certain Ulva thalli. These findings suggest that the presence of a cell wall may constitute a diffusion barrier for CO2, but not for HCO3−, utilization under natural seawater conditions.

Method for evaluating algal production and degradation based on nitrogen levels in particulate organic matter

A population of Ulva rotundata (Bliding, C., A critical survey of European taxa in Ulvales. Part I. Opt. Bot. Lund, A8 (3), 1–160) was studied for 7 months in a shallow brackish eutrophic lagoon (Prévost Lagoon, Languedoc, France). Biomass was measured in square-meter quadrates, and algal growth in on-site cages. Carbon and nitrogen levels were spatiotemporally monitored in Ulva thalli and in particulate organic matter. Thalli rapidly degraded into particulate matter from the surface to the bottom, increasing nitrogen concentrations and decreasing carbon concentrations. We propose a method for estimating algal production and possible carbon loss in this type of lagoon, based on nitrogen levels in particulate organic matter. Algal production over the whole period can be evaluated by adding instantaneous biomass levels corresponding to the main particulate nitrogen peaks.