The effect of zinc on the increase in length of five species of intertidal fucales

The growth rate of Pelvetia canaliculata (L.) Dec. et Thur., Fucus spiralis L., F. vesiculosus L., F. serratus L., and Ascophyllum nodosum (L.) Le Jolis was measured in six different concentrations of zinc (0.025–14 mg/l) during a period of ten days. No significant growth response was observed at 0.1 mg/l of zinc. A significant reduction of growth during the first two to three days of exposure to 1.4 mg/l or more was followed by no or small further decline. Apices of A. nodosum from localities with different background load of zinc (0.1–0.5 mg/l and <0.01 mg/l) showed no difference in response to 2.6 mg/l of zinc.     

Factors controlling the upper limits of fucoid algae on the shore

Year-round observations on the condition of intertidal seaweeds growing in situ on the shore, show that the upper limits of the zones characterized by Pelvetia canaliculata (L.) Done et Thur., Fucus spiralis L. and Ascophyllum nodosum (L.) Le Jol. were periodically pruned back by environmental conditions. The uppermost plants of each species showed clear signs of tissue damage 21 to 28 days after a time when drying conditions coincided with neap tides which exposed the plant to aerial conditions for long periods. High air temperatures aggravated the damage, but neither frost nor prolonged rain had any obvious adverse effects. On spring tides the plants were wetted every day and no damage resulted regardless of the weather.These species clearly all reach up to their physiological limits on the shore investigated, but presumably Fucus vesiculosus L. and F. serratus L. do not, for they were never observed to show signs of tissue damage attributable to exposure to air. Transplant experiments did, however, prove that F. serratus cannot survive in the F. spiralis zone and nor can F. spiralis persist in the Pelvetia canaliculata zone.Laboratory experiments also demonstrated that the ability to tolerate desiccation and then to resume photosynthesis and growth when re-submerged was greatest in P. canaliculata, the species found highest on the shore, and was progressively less in species inhabiting successively lower levels.     

Short-term effects of temperature upon the growth of intertidal fucales

The growth rate of five species of intertidal Fucales (Pelvetia canaliculata (L.) Dec. et Thur., Fucus spiralis L., Fucus vesiculosus L., Fucus serratus L., Ascophyllum nodosum (L.) Le Jolis) was measured at temperatures from 2.5 to 35 °C. An increase in temperature immediately causes a high growth rate, and during the first hour it increases linearly with temperature; at 35 °C it is 20 times the control at 7 °C. This acceleration of growth is based mainly on stored photosynthate. After the first few hours the growth rate decreases rapidly, particularly at the highest temperatures. After 2–3 weeks a temperature optimum below 17.5 °C is indicated. High temperatures, 30–35 °C, were lethal to all species, with a survival time corresponding to their vertical zonation in the natural habitat.     

The effect of copper on length increase in Ascophyllum nodosum (L.) Le Jolis

The increase in length of Ascophyllum nodosum (L.) Le Jolis was measured in copper concentrations varying from 14–5000 μg/1 sea water. The growth was unaffected by concentrations of 33 μg/1 or less added for a period of 11 days, but at higher concentrations growth was gradually reduced. When the number of days (x) of exposure to a concentration (y) (y > 33 μg/1) is compared with z (the corresponding percentage reduction of growth rate), the data fit the equation z = 0.084 xy up to at least z = 60%.     

Factors controlling the lower limits of fucoid algae on the shore

Field and culture studies on fucoid alga of the upper shore showed that their lower limits of distribution were determined largely by interspecific competition. Pelvetia canaliculata (L.) Dcne. et Thur., which is strictly confined to the highest algal zone, grew much more slowly, both in culture and on the shore, than did Fucus spiralis L., which occupies the zone immediately below Pelvetia. When transplanted to the Fucus spiralis zone, macroscopic Pelvetia thalli grew normally, but Pelvetia zygotes which germinated within this zone reached macroscopic size only when competing Fucus spiralis was repeatedly removed.Both species required high light levels to grow in culture, yet their embryos remained viable for long periods in total darkness. Thus, Pelvetia cannot grow in the shade of Fucus spiralis, but actual removal of the Pelvetia germlings from the Fucus spiralis zone must be affected by some other factor.F. spiralis grew vigorously when transplanted to M.T.L., a level at which it is normally rare. In culture, its embryos grew more slowly than those of the species found lower on the shore such as F. vesiculosus L. and F. serratus L.; hence interspecific competition may again be involvedYoung Ascophyltum nodosum (L.) Le Jol. plants grew almost as slowly as those of Pelvetia, yet Ascophyllum dominates the middle shore. In culture it showed only slightly greater tolerance of low light intensity than other fucoids but, unlike Pelvetia, persisted and grew beneath a Fucus canopy in the field. The possibility that differences in life history and palatibility to grazing molluscs contribute to the disparate competitive abilities of Pelvetia and Ascophyllum is discussed.     

Influence of day-night and tidal cycles on phenol content and antioxidant capacity in three temperate intertidal brown seaweeds

The daily variations of phenol contents and antioxidant capacities were surveyed in a 32-h field experiment in three temperate brown seaweeds belonging to Fucales - Pelvetia canaliculata, Ascophyllum nodosum and Bifurcaria bifurcata - living at different intertidal levels — high-, mid- and low-tide level, respectively. Phenolic compounds of brown seaweeds are secondary metabolites involved in many different protection mechanisms, as for example against grazer and pathogen attack as well as UV damage. This study was thus aimed at understanding the influence of both day/night and tidal cycles on the brown seaweed phenol pool with respect to their bathymetric level on the shore. These cycles affect the quantity and quality of light received by intertidal seaweeds (protection via the water layer during immersion), and the photoprotective role of phlorotannins was thus evaluated. Phenol levels and antioxidant capacities were monitored every hour during a tidal cycle and a half at the equinox spring tide, in March 2003. The three species contained rather high phenol levels, i.e. about 3, 6 and 4% DW in P. canaliculata, A. nodosum and B. bifurcata, respectively. Antioxidant capacities globally paralleled phenol contents in the three species under study. Moreover, the measured antioxidant capacities and the phenol contents of the extracts were significantly and positively correlated in the three species. Significant effect of neither cycles nor their interaction was observed in any species despite a trend to follow day/night alternation for P. canaliculata, and emersion/immersion cycle for A. nodosum. No trend was observed for the third species. However, significant correlations between phenol levels of P. canaliculata and A. nodosum and measured air-temperature were found. Our results suggested an effect of aerial, aquatic and both conditions on the phenolic pool of P. canaliculata, B. bifurcata and A. nodosum, respectively, and a fast evolution of the phenolic pool on a day time scale.     

UPLC-MS profiling of low molecular weight phlorotannin polymers in Ascophyllum nodosum,Pelvetia canaliculata and Fucus spiralis

Phlorotannins are a group of complex polymers, found in particular brown macroalgae, composed solely of the monomer phloroglucinol (1,3,5-trihydroxybenzene). Their structural complexity arises from the number of possible linkage positions between each monomer unit. This study aimed to profile the phlorotannin metabolite composition and the complexity of isomerisation present in brown macroalgae Ascophyllum nodosum, Pelvetia canaliculata and Fucus spiralis using UPLC-MS utilising a tandem quadrupole mass spectrometer. Phlorotannin-enriched fractions from water and aqueous ethanol extracts were analysed by UPLC-MS performed in multiple reaction monitoring mode to detect molecular ions consistent with the molecular weights of phlorotannins. Ascophyllum nodosum and P. canaliculata appeared to contain predominantly larger phlorotannins (degree of polymerisation (DP) of 6–13 monomers) compared to F. spiralis (DP of 4–6 monomers). This is the first report observing the complex chromatographic separation and metabolomic profiling of low molecular weight phlorotannins consisting of more than ten monomers. Extracted ion chromatograms, for each of the MRM transitions, for each species were analysed to profile the level of isomerisation for specific molecular weights of phlorotannins between 3 and 16 monomers. The level of phlorotannin isomerisation within the extracts of the individual macroalgal species differed to some degree, resulting in substantially different numbers of phlorotannin isomers for particular molecular weights. A similar UPLC-MS/MS separation procedure, as outlined in this study, may be used in the future as a means of screening the metabolite profile of macroalgal extracts, therefore, allowing extract consistency to be monitored for standardisation purposes.     

Dietary Exposure to Lead and Cadmium in Sweden

Abstract

A duplicate diet study on male and female pensioners in 1970–71 showed mean daily dietary lead intakes of 30 μg and 19 μg respectively. The corresponding cadmium intakes were 10.5μg and 12.9 μg. Analysis of duplicate diets collected during seven consecutive 24-hour periods from 15 women in Stockholm in 1988 showed a mean daily lead intake of 26 μg (range 13–40 μg). The corresponding cadmium intake was 8.5μg (range 5.7–14 μg). Analysis of faeces samples corresponding to the duplicate diets showed similar lead and cadmium contents (mean lead content 24 μg day^?1, range 10–41 μg day^?1; mean cadmium content 8.9 μg day^?1 range 5.5–12 μg day^?1). The median lead and cadmium concentrations in human milk collected in Uppsala were 2 μg kg^?1 and 0.1 mg kg^?1 respectively. The median weekly intakes of lead and cadmium by the breast-fed infants were calculated to be 2 μg kg^?1 body weight and 0.1 μg kg^?1 body weight. Analysis of seven daily diets, together representing the weekly diet of an adult Swedish male, showed a mean lead content of 26 μg (range 15–45 μg), and a mean cadmium content of 10 μg (range 7–15 μg). The mean daily intakes of lead and cadmium found by analysing market baskets prepared in 1987 were 17μg and 12μg respectively. Calculations based on food balance sheet data and levels of lead and cadmium in individual foods showed mean daily intakes of 30 μg lead and 14 μg cadmium per person.     

Natural chelators in sea water: Detoxification of Zn2+ by brown algal polyphenols

We have examined growth responses of several species of marine phytoplankton, cultured with and without heavy metal stress, to supplements of polymeric polyphenols from the brown algae Ascophyllum nodosum (L.) Le Jol. and Fucus vesiculosus L. In the absence of additional heavy metals. supplements of up to 4000 μg. 1 of polyphenols had a small effect on initial growth rates for three of these microalgae and had no effect on maximum cell densities for four species. One very common, heavy metal-sensitive diatom, Skeletonema costatum (Grev.) Cl., showed significantly increasing maximum cell density in the cultures, with increasing addition of polyphenols to the medium. The toxicity of Zn²⁺ (0.5–2.0 mg·1 ¹) to cultures of the diatom Phaeodactylum tricornutum Bohlin was relieved by supplements (100–200 μg·1 ¹) of the brown algal polyphenols. Exudation of these polyphenols from brown seaweeds may contribute to the natural chelating capacity of inshore sea water.     

Effects of small-scale disturbances of canopy and grazing on intertidal assemblages on the Swedish west coast

The effects of small-scale disturbances (80×30-cm plots) of canopy and grazers on intertidal assemblages were investigated in this 4-year experiment on sheltered rocky shores on the Swedish west coast. Canopy disturbances due to ice scouring were mimicked by removal of adult plants of the seaweed Ascophyllum nodosum (L.) Le Joli. Density of the main epilithic grazing gastropods, Littorina spp., was lowered by exclosure and handpicking. Based on earlier experiments in other areas, the general hypothesis was that canopy removal and grazer exclosure, alone or in combination, should increase the recruitment of A. nodosum or other fucoid juveniles, and change the structure of the understorey assemblage.There was an effect of canopy removal on the development of this assemblage, lasting for more than 31 months. Both increased and decreased abundances of species were found as short-term effects, but there was also a longer-term effect with increased abundance. Grazer exclosure was only effective in combination with canopy removal, causing a short-term increase in ephemeral green algae. Short-term effects of canopy removal were also the increase in recruitment of Semibalanus balanoides (Linnaeus) and the decrease of the red alga Hildenbrandia rubra (Sommerfelt) Meneghini. Fast recruitment and growth of fucoid species (Fucus serratus L. and F. vesiculosus L.) restored the canopy and conditions of the understorey within 18 months. Thus, the canopy removal changed the physical conditions for the understorey, making it possible for other species to coexist in this community. Surprisingly, no effect of canopy removal or grazer exclusion was found on the recruitment of juvenile A. nodosum, neither by canopy removal nor grazer exclosure. The lack of such effects might be due to the early mortality caused by other grazers (small, mobile crustaceans), or to the low density of periwinkles on these shores. However, despite the patchy and generally low recruitment of A. nodosum juveniles, observations suggested that the cover of A. nodosum in manipulated patches would return to initial levels, either by recruitment or regrowth of small holdfasts and from growth of edge plants.     

Action toxique de quatre métaux lourds (cadmium,cuivre, mercure,plomb) sur la croissance d'Asparagopsis armata Harvey (Rhodophycée: Bonnemaisoniale) en culture

The increase in length of Asparagopsis armata Harvey (Rhodophyceae: Bonnemaisoniale) was measured in various concentrations of lead, mercury, cadmium, and copper. Significant reductions of growth rate compared with controls were observed at 3.70 mg · 1^?1 of lead, 0.31 mg · 1^?1 of cadmium, and 0.092 mg · 1^?1 of copper. The minimal lethal concentration is 0.0296 mg · 1^?1 for mercury, 18.3 mg · 1^?1 for cadmium, and 1.85 mg · 1^?1 of copper.     

Trace metal uptake by garden herbs and vegetables

In many regions of Iran, crops are irrigated with municipal and industrial wastewater that contain a variety of metals. The purpose of this study was to simulate the level of metals that may be presented to plants over a growing season in a controlled laboratory setting. Cadmium, lead, arsenic, chromium, mercury, nickel, copper, zinc, and selenium were applied to plants at the high rate of 200 g metal/ha/wk. The following plants were examined for metal accumulation and effects on yield: garden cress (Lipidium sativum), leek (Allium porrum L.), basil (Ocimum basilicum L.), mint (Mentha arvensis L.), onion (Allium capa L.), radish (Raphanus sativus L.), and tarragon (Artemisia draculus L.). All plants showed significant uptake of all metals when compared to control (p=0.05), and growth was significantly reduced (p=0.05). Cadmium and chromium levels of 85±7.4 and 47.6±8.9 μg/g); selenium levels were highest in tarragon (16.5±5.8 μg/g). Zinc levels were similar (p=0.05) in all species tested, as were mercury and lead. The remaining metals (nickel and copper) showed significant differences in uptake, depending on plant species.     

Optimization of growth and production of toxins by three dinoflagellates in photobioreactor cultures

A bioreactor system for biotoxin production was appraised against traditional methods of growing dinoflagellate cultures. In an optimised bioreactor culture (5.4?L) operated in batch mode, growth of Karenia selliformis was more efficient than in 15-L bulk carboy culture in terms of growth rate (μ?=?0.07?day^?1 versus 0.05?day^?1) and growth maximum (G _max, 169.10⁶ versus 41.10⁶ cells L^?1). Maximal gymnodimine concentration (1200?μg L^?1) in bioreactor culture was 8-fold higher than in bulk carboy culture, and the yield per cell (pg cell^?1) was 2-fold higher. Similarly the bioreactor batch culture of Alexandrium ostenfeldii performed more efficiently than carboy cultures in terms of growth rate (1.6-fold higher), growth maximum (15-fold higher) and desmethyl C spirolide (SPX-desMe-C) yield (5-fold higher [μg L^?1], though the yield [pg cell^?1basis] was lower). When bioreactor cultures of K. selliformis were operated in continuous mode, the yield of gymnodimine was substantially higher than a carboy or the bioreactor run in batch mode to growth max (793?μg day^?1 over 58?days in continuous culture was achieved versus an average of 60?μg day^?1 [carboy over 40?days] or 249?μg day^?1 [batch mode] over 26?days). Likewise in continuous bioreactor cultures of A. ostenfeldii run over 25?days, the yield of SPX-desMe-C (29?μg day^?1) was substantially higher than in same cultures run in batch mode or carboys (10.2 day^?1 and 7.7?μg day^?1 respectively). Similarly 5.4?L bioreactor batch cultures of K. brevisulcata reached 3.8-fold higher cell densities than carboy cultures, and when operated in continuous mode, the brevisulcatic acids were more efficiently produced than in batch culture (12?μg day^?1 versus 7?μg day^?1). When the bioreactor system was upscaled to 52?L, the maximum cell densities and toxin yields of K. brevisulcata cultures were somewhat less than those achieved in the smaller reactor, which was attributed to reduced light penetration.     

Blood lead and cadmium levels in a six hospital employee population. PESA study, 2009

IntroductionExposure to lead and cadmium is a public health problem due to the broad exposure to these toxic substances among the general population. The objective of this study is to determine blood lead and cadmium concentrations in a working population drawn from six university hospitals in Madrid, Getafe, Cartagena, Santiago de Compostela, Santander and Palma de Mallorca (Spain) and to identify associated factors.Materials and methods951 individuals participated in the study and were administered the standardized PESA^® questionnaire regarding exposure to lead and cadmium. The blood lead and cadmium concentrations were measured by electrothermal atomization atomic absorption spectrometry with Zeeman background correction in Perkin-Elmer spectrometers, guaranteeing the transferability of the results.ResultsThe median overall blood lead concentration was: 1.6 μg/dL (IQR: 0.9–2.7) and that of cadmium was: 0.21 μg/L (IQR: 0.10–0.50). There were significant differences in lead levels between men (2 μg/dL) and women (1.5 μg/dL), postmenopausal (2.6 μg/dL) and premenopausal women (1.1 μg/dL), and between participants who cooked in earthenware (2.1 μg/dL) and those who did not (1.5 μg/dL). The median of cadmium in women (0.24 μg/L) was higher than in men (0.11 μg/L) and was also higher in subjects who smoked (0.70 μg/L) than in non-smokers (0.13 μg/L).ConclusionsA reduction in blood lead and cadmium levels was observed with respect to previous studies carried out in Spain. Nevertheless, the results suggest there are certain factors which increase risk such as age, gender, menopause, age of housing, cooking in lead-glazed earthenware and exposure to cigarette smoke.     

Effects of density on growth rates of four benthic diatoms and variations in biochemical composition associated with growth phase

Diatom cell quantity and their biochemical composition vary among species and are greatly affected by harvest stage or culture conditions. This study compares growth pattern, cell attachment, and biochemical composition of four diatoms suitable for abalone post-larvae: Navicula incerta, Proschkinia sp., Nitzschia sp., and Amphora sp. The four diatoms were grown in F/2 medium at 28.5?±?1.4°C, under 62?±?8?μmol?photons?m^?2?s^?1, at different original inoculating densities (0.05?×?10⁶, 0.10?×?10⁶, and 0.25?×?10⁶?cells?mL^?1) and were harvested in log and stationary phase of growth for biochemical analysis. Total protein, carbohydrate, lipid, and ash composition, as well as fatty acid composition, were determined. All diatoms grew better when inoculated at 0.10?×?10⁶?cell?mL^?1 with Proschkinia sp. reaching the highest cell density of 6.56?×?10⁶?cells?mL^?1 in log phase. Amphora sp. had the highest cell attachment capacity when inoculated at 0.10?×?10⁶?cell?mL^?1 (11,580?cells?mm^?2), whereas N. incerta had the lowest (7,750?cells?mm^?2). Protein and lipid (percent dry weight) contents were generally highest in cells during log phase of growth; Amphora sp. in log phase of growth had the highest lipid content of 9.74% DW, whereas significant differences in carbohydrate between the two growth phases were only observed for Proschkinia sp. Besides, all diatoms had higher energy contents in log phase of growth. There were no significant differences in ash content among the four diatoms. Polyunsaturated fatty acid (PUFA) content ranged from 23.25% to 38.62% of the total fatty acids, and the four diatoms tested were richer in n-3 PUFA than in n-6 PUFA. All the diatoms had significant quantities of 20:5n-3 (EPA) (between 12.69% and 17.68% of TFA), and Proschkinia sp., in log phase of growth, had the highest quantity of arachidonic acid (20:4n-6; ARA). The results highlight the influence of culture conditions and harvest protocols on diatom nutritive value and enabled a preliminary approach towards the selection of novel diatom species.     

Temporal and spatial variability in the heavy-metal content of Dreissena polymorpha (Pallas) (Mollusca: Bivalvia) from the Kleines Haff (northeastern Germany)

The present investigation was performed on zebra mussels, Dreissena polymorpha (Pallas), which were sampled from the Kleines Haff. As a part of the Oder estuary, the Kleines Haff acts as a sink for the load of the river Oder. Mussel shells and mussel tissue were analyzed for their content of selected heavy metals, based on the composition of the suspended matter. Mussels were sampled in May, July, August and September 1996 at different locations and divided into three groups regarding their body size. The data show that concentrations of lead, cadmium and mercury vary during the year. Mussel shells and mussel tissue showed seasonal and local differences in heavy-metal concentration. Between the size classes, however, there was no significant difference, with one exception: the lead content in tissues was significantly higher in large mussels (>2.5 cm shell length) than in small ones (<1.9 cm). The concentrations of lead and cadmium clearly decreased in mussel shells from May to September, while they increased in mussel tissues. The lead concentration in the tissue corresponded to that of mercury. The highest values measured for mercury were 218 μg/kg dry weight (DW), for cadmium 1030 μg/kg DW and for lead 6182 μg/kg DW. The average concentration of heavy metals in mussel tissue was 9 to nearly 170 times lower than in the surrounding sediment and seston. It can be assumed that a balance exists between the concentration of heavy metals in the mussels' food and the mussels themselves.     

Growth interactions between littoral diatoms and juvenile marine algae

Interactions have been studied between juvenile plants of green, brown, and red marine algae and 31 diatom clones isolated from a variety of marine eulittoral habitats. The interactions seemed to be of an individual nature for both juvenile plants and diatoms. Germlings of Ulva lactuca L. mostly showed enhanced growth, often with significant increases in population sizes of the accompanying diatoms. Fucus spiralis L. germlings were mainly unaffected by growth in the presence of the diatom clones, but growth of the diatoms was often stimulated. Ascophyllum nodosum (L.) Le Jol. germlings were little affected, whilst the accompanying diatoms were less noticeably affected than with Fucus spiralis. Germlings of F. vesiculosus L. often showed growth inhibitions in the presence of diatoms, with many diatom populations showing enhanced growth. Similarly, the discoid encrusting sporelings of Chondrus crispus Stackh. showed growth inhibitions where there were measurable interactions, although the accompanying diatoms usually failed to show growth stimulations. The discoid sporelings of Gigartina stellata (Stackh. in With.) Batt. showed high mortalities, usually with marked increases in population sizes of accompanying diatoms.     

Trace elements in bipolar disorder

IntroductionTrace elements may play an important role in bipolar disorders. The objective of this study is to determine serum copper and zinc, blood lead and cadmium and urine lead, cadmium and thallium concentrations in patients diagnosed with bipolar disorders and to compare these levels with those of a healthy control group.Materials and methodsA total of 25 patients diagnosed with bipolar disorder and 29 healthy subjects participated in this study. Serum copper and zinc concentrations were measured using flame atomic absorption spectrometry; the blood lead and cadmium concentrations were measured by electrothermal atomization atomic absorption spectrometry with Zeeman background correction; urine lead, cadmium and thallium concentrations were measured by inductively coupled plasma mass spectrometry.ResultsMedian blood and urine lead and cadmium levels were significantly higher among the bipolar patients than among the control group: Blood lead (μg/dL): patient median: 3.00 (IQR: 1.40–4.20); control median (μg/dL): 2.20 (IQR: 0.90–3.00) p = 0.040. Blood cadmium (μg/L): patient median: 0.39 (IQR: 0.10–1.15); control median: 0.10 (IQR: 0.10–0.17) p < 0.001. The median of cadmium (μg/L) in patients who smoked (1.20 IQR: 0.44–2.30) was higher than that in non-smokers (0.12 IQR: 0.10–0.34) p < 0.001. There was a statistically significant increase (p = 0.001) in zinc levels among patients in the manic phase (mean 111.28, SD: 33.36 μg/dL) with respect to the control group (mean 86.07, SD: 12.39 μg/dL).ConclusionsThe results suggest that there could be higher levels of some toxic trace elements in the group of patients with bipolar disorder than in the healthy control group.     

Bioaccumulation and distribution of mercury in the hard clam,Meretrix lusoria (Bivalvia:Veneidae)

1. Total mercury concentration in whole soft parts of the hard clam, Meretrix lusoria, increased significantly with increasing exposure concentrations. It reached 4.247–7.084 and 9.956–13.643 μg T-Hg/g dry weight in 5 and 50 μg/l Hg mercury solution, respectively, against a background level of 1.824–0.577μg T-Hg/g dry weight.2. Bioconcentration factor was 4–6 times higher in 5 μg/l Hg than that of 50 μg/l Hg. An estimated biological half-life of 20.2 and 18.4 days in 5 and 50 μg/l Hg, respectively, were also obtained after 14 days uptake.3. Accumulation of mercury in tissues of the clams was greater in the gills and viscera than in the mantle, adductor, foot, or hemolymph.4. The amount of mercury present in the gills is related to be a linear relationship with the mercury content of viscera.     

Biostimulant activity of brown seaweed species from Strangford Lough: compositional analyses of polysaccharides and bioassay of extracts using mung bean (Vigno mungo L.) and pak choi (Brassica rapa chinensis L.)

The aims of this study were to characterise the composition of seaweed species and to evaluate the efficacy of aqueous extracts as plant biostimulants. Five species (Ascophyllum nodosum, Fucus serratus, Fucus vesiculosus, Laminaria hyperborea and Sargassum muticum) of seaweed were harvested from Strangford Lough, Northern Ireland for the evaluation of polysaccharides, indole-3-acetic acid (IAA), carbon, nitrogen, lipid, ash and mineral contents. The compositional analyses of the five species and their freeze-dried extracts were also carried out using thermogravimetric analysis, scanning electron microscopy and X-ray microanalysis. The concentration of IAA in the acid extracts of the five species ranged between 2.74 and 46.8?ng?g^?1. The carbon, nitrogen, lipid and ash contents ranged between 25.0 and 38.6, 1.37%, and 3.16, 0.83%, and 3.98 and 18.10 and 47.68%, respectively. L. hyperborea and S. muticum contained the highest amounts of minerals. The biostimulant activities of acidic (pH?3.0), neutral (pH?6.5) and alkaline (pH?9.0) extracts were determined by mung bean bioassay. The alkaline extracts from F. vesiculosus and A. nodosum stimulated significantly (P?<?0.001) higher dry matter (DM, %) yield of the mung bean plants. The majority of the acidic extracts significantly (P?<?0.001) enhanced root formation on the mung bean stem cuttings compared to alkaline or neutral extracts. The acidic extracts of the five species, water control and a commercial product were evaluated as foliar feeds for pak choi plants using a hydroponic production system. The interaction of species, e.g. A. nodosum and F. vesiculosus and the two treatment dilutions on DM yield increases of pak choi were significant (P?<?0.05).