A Comparative Evaluation of the Metal-Binding Activity of Low-Esterified Pectin from the Seagrass Zostera marina and Other Sorbents

A comparative study of the sorption capacity of low-esterified pectin from the seagrass Zostera marina and drugs used for hemosorption and enterosorption was made. Low-esterified pectin was less efficient in binding in vitro lead, cadmium, and copper compared to chelating and thiol-containing compounds; but it was much more efficient than activated carbon, polyphepan, microcrystalline cellulose, and enterodez.     

Growth dynamics of Zostera in Sevastopol Bay (Crimea,Black Sea)

Density, biomass and primary productivity of eelgrass (Zostera marina L.) and density and biomass of Zostera noltii Hornem. were studied at three locations in Sevastopol Bay, Crimean Peninsula, Ukraine, in April 2002, late September 2002, and late January 2003 at 3 m and 5 m depths. All three growth parameters varied by station, depth, and month. The aboveground biomass (AGB) was greater in September than in April or January at 3 m. It was greater at 5 m than at 3 m in April at one station. For Z. noltii, results were more variable as to month. For belowground biomass (BGB), month and station relationships were not clear cut. It was generally true that total biomass was greatest in September. Significant differences in density, AGB and total biomass were observed for station and month in eelgrass, while in BGB, these differences were significant for depth and for month. Primary production in eelgrass was greatest at both depths in April as compared to September or January. Reproductive shoots were found only during April. Overall, seedlings were found in all collection periods and depths, but were most abundant at the three stations in April.     

Impact of differential predation potential on eelgrass (<Emphasis Type="Italic">Zostera marina</Emphasis>) faunal community structure

The trophic structure of fauna within eelgrass beds (Zostera marina) was assessed at two sites in Little Egg Harbor, New Jersey, USA during the summer of 1999. Although the sites were similar with respect to both Z. marina shoot density and plant biomass, they differed significantly in the relative distribution of large predatory fish (e.g., Cynoscion regalis, Paralichthys dentatus, Morone saxatilis). Site One, Marsh Elder, was characterized by a significantly greater catch per unit effort for large predators than Site Two, Shelter Island. Gut content analysis provided direct evidence of trophic linking and significant declines between these fish and four of the five most abundant organisms collected in throw traps used to analyze the density of large benthic prey/small predators. The densities of grass shrimp (Palaemonetes spp. Hippolyte zostericola), blue crab (Callinectes sapidus), and small predatory fish (e.g., Syngnathus fuscus, Opsanus spp., Tautoga onitus) were significantly reduced at Marsh Elder, potentially as a direct impact of large predatory fish. In turn, the differences in the density of small predators observed between sites produced either a significant positive or negative effect on the distribution of small benthic prey (e.g., polychaetes, amphipods), resulting in a two-step trophic cascade within the system. Additionally, an analysis of similarities defined each site independently for both large prey/small predators and small benthic prey community structure. Although the mechanism which produced the differences in the distribution of large predatory fish remains unknown, their impact on faunal community structure mediated not only the distribution of their potential prey, but also subsequent lower trophic levels.     

Short-term phosphate uptake kinetics in Zostera noltii Hornem: a comparison between excised leaves and sediment-rooted plants

Short-term phosphate uptake by excised leaves of Zostera noltii Hornem. as well as by leaves of sediment-rooted plants were characterized and compared in a kinetic framework. Time courses of phosphate disappearance were measured over a wide range of initial substrate concentrations. Phosphate uptake determined by this perturbation method did not follow Michaelis-Menten kinetics. Both excised leaves and sediment-rooted plants exhibited a biphasic uptake pattern as a function of phosphate concentration. However, rooted plants showed higher uptake rates and accumulated higher amounts of phosphate than excised leaves. The results point out the importance of the structural and functional coupling between shoots and underground parts during the nutrient foliar uptake processes. Our study also indicates that Zostera noltii leaves function as a phosphate sink in the water column.A second objective of this work is to compare the perturbation and the multiple flask methods in determining the uptake kinetic parameters. The obtained results support that both methods provide valuable and complementary information in determining the uptake rates.     

Effectiveness of pectin extracted from the eelgrass Zostera marina for alleviating lead-induced liver injury

The effects of pectin from the eelgrass Zostera marina on toxic liver injury induced by enteral administration of lead acetate are examined in experiments on rats. The results show that pectin helps to rapidly reduce lead concentration in liver, to decrease lipid peroxidation, and to normalize the levels of total cholesterol and triglycerides in blood serum and liver.     

The mercury binding activity of pectin isolated from the seagrass Zostera marina

The kinetics of mercury binding by pectin isolated from the seagrass Zostera marina was described, and its maximum mercury binding activity at pH from 2.0 up to 6.0 was determined. It was shown that mercury binding by pectin in in vitro conditions did not depend on concentration of hydrogen ions in the environment. The maximum mercury binding activity estimated from the Langmuir equation was 2.64 mmol/g of dry mass of the pectin.     

Allozymic implications of the propagation of eelgrass Zostera japonica within a river system

We examined the allozymic variation of Zostera japonica, a seagrass in brackish-water zones, for plant samples collected from the Ohashi River (four localities including nine sampling sites within 7.5km) and Lake Nakaumi (one location), to which it is connected, in Japan to study plant propagation. Among five enzymes detected, phosphoglucoisomerase (PGI) showed three alleles (b, c, d) and five genotypes (bb, cc, dd, bd, cd), but the other four enzymes were monomorphic in 185 plant samples. PGI genotype variation was found not only in large meadows but also in small (<1 m) vegetation patches, indicating genet coexistence within a small spatial scale. The observed genotype frequencies in large meadows did not differ significantly from Hardy—Weinberg equilibrium. However, no plant sample included genotype bc. These results suggest that new genet recruitment by mating among genets has occurred but that recruitment may not be very frequent. The allele frequencies differed significantly, not only between distant (1.4 km) meadows but also within short distances (20–40 m) within a meadow. Plants carrying allele c were collected from the upper but not from the lower part of the Ohashi River. These results suggest successful dispersal by water currents is restricted.     

Peculiarities of adhesion of epiphytic bacteria on leaves of the seagrass <Emphasis Type="Italic">Zostera marina</Emphasis> and on abiotic surfaces

A comparative study of the adhesion of epiphytic bacteria and marine free-living, saprophytic, and pathogenic bacteria on seagrass leaves and abiotic surfaces was performed to prove the occurrence of true epiphytes of Zostera marina and to elucidate the bacterium-plant symbiotrophic relationships. It was shown that in the course of adhesion to the seagrass leaves of two taxonomically different bacteria, Cytophaga sp. KMM 3552 and Pseudoalteromonas citrea KMM 461, isolated from the seagrass surface, the number of viable cells increased 3–7-fold after 60 h of incubation, reaching 1.0–2.0 × 10⁵ cells/cm²; however, in the case of adhesion of these bacteria to abiotic surfaces, such as glass or metal, virtually no viable cells were observed after 60 h of incubation. Such selectivity of cell adhesion was not observed in the case of three other bacterial species studied, viz., Vibrio alginolyticus KMM 3551, Bacillus subtilis KMM 430, and Pseudomonas aeruginosa KMM 433. The amount of viable cells of V. alginolyticus KMM 3551 absorbed on glass and metal surfaces increased twofold after 40 h of incubation. The cells of saprophytic B. subtilis KMM 430 and pathogenic P. aeruginosa KMM 433 adsorbed on three studied substrata remained viable for 36 h and died by the 60th hour of incubation.     

Relative effects of nutrient enrichment and grazing on epiphyte-macrophyte (Zostera marina L.) dynamics

The independent and interactive effects of nutrient concentration and epiphyte grazers on epiphyte biomass and macrophyte growth and production were examined in Zostera marina L. (eelgrass) microcosms. Experiments were conducted during early summer, late summer, fall, and spring in a greenhouse on the York River estuary of Chesapeake Bay. Nutrient treatments consisted of ambient or enriched (3× ambient) concentrations of inorganic nitrogen (ammonium nitrate) and phosphate. Grazer treatments consisted of the presence or absence of field densities of isopods, amphipods, and gastropods. epiphyte biomass increased with both grazer removal and nutrient enrichment during summer and spring experiments. The effect of grazers was stronger than that of nutrients. There was little epiphyte response to treatment during the fall, a result possibly of high ambient nutrient concentrations and low grazing pressure. Under low grazer densities of early summer, macrophyte production (g m^–2 d^–1) was reduced by grazer removal and nutrient enrichment independently. Under high grazer densities of late summer, macrophyte production was reduced by enrichment only with grazers absent. During spring and fall there were no macrophyte responses to treatment. The relative influence of epiphytes on macrophyte production may have been related to seasonally changing water temperature and macrophyte requirements for light and inorganic carbon.     

Leaf dynamics and standing stocks of intertidal Zostera noltii Hornem. and Cymodocea nodosa (Ucria) Ascherson on the Banc d'Arguin (Mauritania)

Leaf dynamics and standing stocks of intertidal seagrasses were studied in the Baie d'Aouatif (Parc National du Banc d'Arguin, Mauritania) in April and September 1988. Standing stocks of Zostera noltii Hornem. suggest a unimodal seasonal curve similar to what is found for populations at higher latitudes. Also, leaf growth rates (0.03 cm² cm^–2 day^–1 on average) were similar to those found at higher latitudes in these months. Variation in leaf loss over tidal depth, time and different locations in the Baie d'Aouatif was larger and more often significant than variation in leaf growth. In general, Z. noltii beds in the Baie d'Aouatif had comparable leaf growth rates and standing stocks. In both months losses were almost always higher than or equal to growth.Variation in leaf loss over time was much higher in the plots that were situated high in the intertidal than in lower plots. This is explained by differences in susceptibility to sloughing, which is presumably higher in periods with low tide around noon for shallow depths.In an experiment using artificial shading nets, in situ leaf growth was affected negatively from 94% shading onwards. This shading was observed to reduce the light intensity reaching the seagrass bed to a level below the reported range of light compensation points for Z. noltii. Cymodocea nodosa (Ucria) Ascherson on average had higher leaf area and relative growth rates than Z. noltii and much lower loss rates, resulting in a positive net increase in September. Standing stocks were also higher than for Z. noltii. A mixed seagrass bed containing the above two species and Halodule wrightii Ascherson had the highest observed total biomass: 335 g m^–2 ash-free dry weight.     

Temperature and emergence effects on the net photosynthesis of two Zostera noltii Hornem. morphotypes

Apparent photosynthetic rates (APS) of two Zostera noltii Hornem. morphotypes were measured in air and in water at different temperatures with a closed infra-red gas analysis system (IRGA).Hyperbolic functions accurately described the photosynthesis-CO₂ relationships when the leaves were exposed to air. The photosynthetic behaviour in water, on the contrary, could not be described by Michaelis type kinetics, due to the existence of a rapid transition from the initial slope to the saturation phase. Both morphotypes (narrow-leaved, NLM and large-leaved, LLM) showed higher APS rates in water than in air, although the highest APS rates, in air as well in water, were recorded for the NLM.Temperature had a significant influence on the photosynthetic parameters: APS_max (maximum photosynthetic rate) decreased (in air and in water) with increased temperature in both morphytypes; compensation points (CP) in air increased at high temperature, especially in the LLM. NLM specimens showed enhanced affinity (lower Km) with increasing temperature in air. On the contrary, Km values in water were not significantly affected by temperature.The results suggest that NLM specimens are better adapted than the LLM to occur exposed to air. The distributional pattern of the two morphotypes in the Palmones Estuary is discussed on the basis of their photosynthetic behaviour.     

Differential anaerobic decomposition of seagrass (Zostera noltii) and macroalgal (Monostroma obscurum) biomass from Arcachon Bay (France)

Arcachon Bay is characterized by extensive meadows of the seagrass Zostera noltii. Moreover, as a consequence of eutrophication, massive proliferations of the macroalga (Monostroma obscurum) have occurred since the beginning of 1990s.This paper describes the anaerobic decomposition of biomass of both species under experimental conditions by two methods. Firstly, the dynamics of decomposition were studied in situ using litter bags. The remaining biomass and the elemental composition of the decomposing macrophytes were monitored. Secondly, degradation was studied in experimental containers under anoxic conditions in which the release of inorganic nutrients and the development of fermentative and sulfate-reducing bacterial populations were followed.The decomposition rate of total biomass was faster for macroalgae than for the vascular plants, thus corroborating previous observations. However, both in situ and laboratory experiments showed that the anaerobic decomposition of the seagrass Z. noltii resulted in rapid release of inorganic N and P, and increasing C/N and C/P ratios of the residual biomass. As a result, the recycling of inorganic nitrogen and phosphorus compounds was slightly more efficient for Z. noltii than for M. obscurum. Recycling of inorganic nutrients appears to be of a great importance to the whole ecosystem, because of the extensive spreading of Z. noltii in the bay.     

Seasonal dynamics of <Emphasis Type="Italic">Zostera noltii</Emphasis> Hornem. in two Mediterranean lagoons

The density, biomass and shoot morphology of two populations of Zostera noltii were monitored from January 1998 to July 1999 at two shallow Mediterranean lagoons of Biguglia and Urbino, which differ in hydro-morphological conditions and nutrient loading. Monitoring included the principal biological and foliar parameters (shoot density, aboveground and belowground biomass, length, width and number of leaves, LAI and coefficient A: percentage of leaves having lost their apex), the organic matter contents of the sediment and the environmental conditions (salinity, turbidity, temperature, nutrient concentrations and dissolved oxygen levels). The two populations of Z. noltii displayed seasonal changes in density (1600–19600 m²), aboveground biomass (11–153 g. DW. m⁻²), leaf length (33–255 mm), and leaf width (0.9–1.8 mm). Temperature and turbidity were significant environmental factors influencing the temporal changes observed in the Z. noltii meadows studied. Conversely, the belowground biomass, the number of leaves per shoot and the LAI did not undergo any seasonal changes. In the Biguglia lagoon, the functioning dynamics of the Z. noltii seagrass beds are determined by the catchment area and the inputs of nutrients derived from it, whereas in the Urbino lagoon the dynamics of the Z. noltiibeds depend on low levels of water turbidity.     

Effects of Epiphytic Load on the Photosynthetic Performance of a Seagrass, <Emphasis Type="Italic">Zostera marina</Emphasis>, Monitored In Vivo by Chlorophyll Fluorescence Imaging

We investigated the effects of epiphytes on photosynthetic activity in a seagrass, Zostera marina. Parameters in our chlorophyll (Chl) fluorescence imaging technique, including Fo, Fm, and Fv/Fm, were monitored from leaf surfaces before and after those epiphytes were removed. Because of the uneven distribution of light intensities, Fm values at the margin of an image were underestimated while those in the central region were overestimated. Chl fluorescence emissions from all leaves except the youngest one were altered by the presence of epiphytes, which predominantly inhabited the surfaces of older leaves. Only a few were found lower on the plant where leaves were very close to each other. Regions where the epiphytes had been loosely bound before their gentle removal showed full restoration of photosynthetic performance to control levels afterward. However, only minor recovery of photosynthesis was found in areas that had been riddled with tightly bound epiphytes and were permanently damaged. In years 2002 and 2003, leaf productivity peaked in May and plummeted in November. More epiphytic diatoms were distributed when the seagrass biomass was larger, with pinnate diatoms dominating.     

Seasonal variation in rates of heterotrophic nitrogen fixation (acetylene reduction) in Zostera noltii meadows and uncolonised sediments of the Bassin d'Arcachon, south-west France

Nitrogen fixation (acetylene reduction) rates were measured over an annual cycle in meadows of the seagrass Z. noltii and uncolonised sediments of the Bassin d'Arcachon, south-west France, using both slurry and whole core techniques. Measured rates using the slurry technique in Z. noltii colonised sediments were consistently higher than those determined in isolated cores. This was probably due to the release of labile organic carbon sources during preparation of the slurries. Thus, in colonised sediments the whole core technique may provide a more accurate estimate of in situ activity. Acetylene reduction rates measured by the whole core technique in colonised sediments were 1.8 to 4-fold greater, dependent upon the season, in the light compared with those measured in the dark, indicating that organic carbon released by the plant roots during photosynthesis was an important factor regulating nitrogen fixation. In contrast acetylene reduction rates in uncolonised sediments were independent of light.Addition of sodium molybdate, a specific inhibitor of sulphate reduction inhibited acetylene reduction activity in Z. noltii colonised sediments by > 80% as measured by both slurry and whole core techniques irrespective of the light regime, throughout the year inferring that sulphate reducing bacteria (SRB) were the dominant component of the nitrogen fixing microflora. A mutualistic relationship between Z. noltii and nitrogen fixing SRB in the rhizosphere, based on the exchange of organic carbon and fixed nitrogen is proposed. In uncolonised sediments sodium molybdate initially severely inhibited acetylene reduction rates, but the level of this inhibition declined over the course of the year. These data indicate that the nitrogen fixing SRB associated with the Zostera roots and rhizomes were progressively replaced by an aerobic population of nitrogen fixers associated with the decomposition of this recalcitrant high C:N ratio organic matter.Acetylene and sulphate reduction rates in the seagrass beds showed distinct summer maxima which correlated with a reduced availability of NH ₄ ⁺ in the sediment and the growth cycle of Z. noltii in the Bassin. Overall, these data indicate that acetylene reduction (nitrogen fixation) activity in the rhizosphere of Z. noltii was regulated both by release of organic carbon from the plant roots and maintenance of low ammonium concentrations in the root zone due to efficient ammonium assimilation.Nitrogen fixation rates determined from acetylene reduction rates measured by the whole core technique ranged from 0.1 to 7.3 mg N m^–2 d^–1 in the Z. noltii beds and between 0.02 and 3.7 mg N m^–2 d^–1 in uncolonised sediments, dependent upon the season. Nitrogen fixation in the rhizosphere of Z. noltii was calculated to contribute between 0.4 and 1.1 g N m^–2 y^–1 or between 6.3 and 12% of the annual fixed nitrogen requirement of the plants. Heterotrophic nitrogen fixation therefore represents a substantial local input of fixed nitrogen to the sediments of this shallow coastal lagoon and contributes to the overall productivity of Z. noltii in this ecosystem.     

Interactions of light and organic matter under contrasting resource simulated environments: the importance of clonal traits in the seagrass <Emphasis Type="Italic">Zostera noltii</Emphasis>

Light reduction in the water column and enhanced organic matter (OM) load into the sediments are two main consequences of eutrophication in marine coastal areas. This study addresses the combined effects of light, OM, and clonal traits in the seagrass Zostera noltii. Large Z. noltii plants were grown in sand with or without the addition of OM and under two light levels (high light and low light). Whereas some complete plant replicates were grown under homogeneous light and/or OM conditions, other replicates were grown under contrasting light and/or OM levels between the apical and the distal parts of the same plant. The three-way factorial design (light, OM load, and apex position) allowed us to determine the harmful effect of light reduction and OM enrichment on the growth, photosynthetic performance, and biochemical composition of Z. noltii. The addition of OM to the sediment promoted a decrease, or even an inhibition, in net plant growth regardless of the light level when the whole plants were grown under homogeneous light conditions. However, the results differed when plants were grown under contrasting light and/or OM conditions between apical and distal parts. In this case, the harmful effect of OM load was alleviated when apical parts were grown under high light conditions. OM loads also negatively affected the photosynthetic performance, evaluated as leaf fluorescence. The results indicate the importance of clonal traits in the response of Z. noltii growth to light conditions and OM enrichment. Guest editors: J. H. Andersen & D. J. Conley Eutrophication in Coastal Ecosystems: Selected papers from the Second International Symposium on Research and Management of Eutrophication in Coastal Ecosystems, 20–23 June 2006, Nyborg, Denmark     

Temperature tolerance and survival of intertidal populations of the seagrass <Emphasis Type="Italic">Zostera noltii</Emphasis> (Hornemann) in Southern Europe (Ria Formosa,Portugal)

The dwarf seagrass Zostera noltii is an important primary producer in Atlantic coastal ecosystems from Mauritania to southern Norway and the Mediterranean Sea. Sessile intertidal organisms existing at the interface between marine and terrestrial environments may be particularly vulnerable to environmental change. In this study, we asked how near to thermal tolerance limits natural populations of Z. noltii are in the Ria Formosa coastal lagoon system in southern Portugal. We recorded the maximum temperatures in the Ria Formosa during the 2007 summer, and conducted experiments to determine the sub-lethal temperature of Z. noltii shoots sampled at two sites located at different tidal heights. Mortality rates and photosynthetic performance were recorded within a range of heat shock temperatures between 35 and 41°C. Survival was recorded ≤37°C, while higher temperatures led to a sudden drop in photosynthetic capacity followed by mortality (shoot loss) that occurred more rapidly with increasing temperatures. At 39°C and above, the rate of shoot mortality in both sites was close to 100%, occurring between 5 and 13 days after the heat shock. Survival was ca. 95 and 90% at 35 and 37°C, respectively. From these results for Z. noltii populations in the Ria Formosa we estimated sub-lethal temperature to be approximately 38°C for Z. noltii, close to the maximum of 36°C recorded in the summer 2007. Considering predicted trajectories in the coming decades, these results raise concern as to the future viability of intertidal Z. noltii populations near the southernmost edge of their distribution. Handling editor: S. M. Thomaz     

Production and ecology of eelgrass (Zostera marinal L.) in the Grevelingen estuary,the Netherlands,before and after the closure

The Grevelingen estuary was cut off from the North Sea and from the influences of the river Rhine by a dam in 1971, and became a stagnant salt-water lake. Production and ecology ofZostera marina L. were studied in 1968 and in 1973–1975, both through standing stock estimations, biomass increases in permanent quadrats, and correlation of distribution patterns with ecological factors. After the closure of the estuary the intertidal eelgrass population extended downwards to 5 m below lake level, probably owing to the increased transparency of the water; the area occupied, and the density of the eelgrass beds increased strongly. Eelgrass annual overground production, based on doubled maximum standing crop values in July–August, was estimated at 50 g C/m² in 1968, 121 g C/m² in 1973 and 91 g C/m² in 1975 inZostera beds, and 4 g C/m² in 1968, 18 g C/m² in 1973 and 23 g C/m² in 1975 for the entire Grevelingen area. A minimum estimate of net production inZostera beds at a depth of 0.50–0.75 m, based on short term changes in biomass in 2 permanent quadrats in 1974 and 1975, was 40.5 g C/m²/yr for overground parts and 12.7 g C/m²/yr for underground parts. Horizontal distribution of celgrass is not primarily limited by grainsize distribution, but more by exposure to wave action and currents. On account of irradiance reduction light is a limiting factor in the vertical distribution of the eelgrass population in Lake Grevelingen. Communication no. 146 of the Delta Institute for Hydrobiological Research, Yerseke, The Netherlands.     

Comparative <Emphasis Type="Italic">in vitro</Emphasis> Assessment of Antioxidant Activities of Low-Etherified Pectin from the Eelgrass <Emphasis Type="Italic">Zostera marina</Emphasis> and Antioxidative Medicines

A comparative study of antioxidant activities of low-etherified pectin extracted from the eelgrass Zostera marina and of two antioxidative medicines, mildronat and emoxipin, was carried out using two in vitro methods allowing us to estimate the reducing activities of the compounds (FRAP assay), and their ability to impede iron- and ascorbate-induced oxidation of Tween 80 to malondialdehyde. It was found that zosterin pectin manifested higher reducing activity compared to the medicines. The inhibitory capacity of zosterin was lower than that of mildronat.