Genotypic temperature adaptations of cellular functions and proteins in two Zostera species

Summary The thermostability of protoplasmic streaming, the capacity for plasmolysis and reduction of tetrazolium salt, and the thermostability of acid phosphatase and peroxidase were compared in two species of Zostera, Z. marina L. and Z. noltii Hornem. which were growing in Sevastopal Bay on the Black Sea. The thermostability of studied functions and enzymes in Z. noltii is approximately 4° or 5° C higher than that in Z. marina and this is consistent with the greater thermophily of Z. noltii, which has a more southerly habitat and which is a less deep-water form than Z. marina. The adaptive significance of the correlation between function and protein thermostability and the environmental temperature is regarded as the adjustment of the level of protein flexibility to a prevailing ambient temperature.     

Evaluation of Zostera detritus as a potential new source of zosteric acid

Detritus of the seagrasses Zostera noltii and Z. marina collected on the beaches of Arcachon Lagoon (France) over a 3-year period was screened as a new source of zosteric acid (ZA). This natural sulphated phenolic acid is a high value-added product capable of preventing settlement of marine organisms and protecting crops from fungal diseases. The seasonal variation of the ZA content was quantified in methanolic and aqueous crude extracts using high-performance liquid chromatography. The concentration found ranged from 65 to 456 μg g⁻¹ dry wt for Z. noltii and 51–692 μg g⁻¹ dry wt for Z. marina, respectively. This is the first report of ZA in Zostera noltii. Detrital leaves of Zostera have never before been screened for their bioactive substances. These results show that this low cost, very abundant and renewable, but heretofore unused, marine resource has potential as a source of a rare and naturally occurring bioactive product.     

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.     

Photosynthetic adaptation of Zostera noltii Hornem.

The study of Zostera noltii Hornem. under stressed conditions in an estuary in southern Spain gives evidence that this seagrass can tolerate high light intensities without damage to its pigment pool. Therefore, photosynthesis at high light intensities remains as intense as at saturation point and it is sustained principally by Photosystem I.The existence of a short-term pigmentary response (60 min) was evidenced and the relationship between assimilation rates and the pigment pool was established.Comparisons made with Z. marina L. and between the respective environmental characteristics of both plants suggests that the special adaptive photosynthetic performance of Z. noltii can be supported by a C₄-type metabolism.     

Seasonal variation in short-term survival of Zostera noltii transplants in a declining meadow in Portugal

In one decade (from 1986 to 1997), the area occupied by Zostera noltii in the Mondego estuary (western coast of Portugal) decreased from 150,000 to 200 m². Our purpose was to identify the most suitable season for transplantation of Z. noltii, as one of the methodologies included in a broader restoration plan of the local Z. noltii meadows. Each month a short-term transplantation experiment (20 days) was undertaken, where the net growth rate of transplants, the number of lost shoots and the number of surviving shoots was estimated. Transplant loss variation was markedly seasonal (ANOVA, F_1,12 = 13.11, p < 0.01). From spring to middle autumn (April–October), the amount of lost shoots was significantly higher (average = 63%) than during late autumn and winter (average = 26%). Multiple regression results suggest that the number of surviving shoots was negatively related with insolation and NH₄-N concentration. Additionally, the net growth rate of the transplants was negatively related with salinity.In conclusion, we recommend that at southern European latitudes, Z. noltii transplantation be undertaken during late autumn and winter. The success of transplantation at this time of the year seems to be related with the prevailing external conditions, namely, low temperatures and low photon flux densities. Furthermore, we hypothesise that the proportion of aboveground to belowground biomass in Z. noltii may also influence transplant survival. Transplantation success was higher whenever belowground biomass was higher than aboveground biomass. In the Mondego estuary, in autumn and winter, the belowground biomass of Z. noltii represents about 51% of the total plant biomass, while in spring and summer, this value decreases to 31% of the total biomass.     

Density and distribution of seeds in bottom sediments in Zostera marina beds in Ago Bay,central Japan

The density of Zostera marina L. seeds in bottom sediments was examined to study the reproductive patterns of the Z. marina population in Ago Bay, Mie Prefecture, central Japan.Seeds and seed coats were numerous in Tategami, where the annual type of Z. marina grows. In contrast, seeds were scarce in Hamajima, where the perennial type of Z. marina grows. Bottom sediment was sampled with sediment cores at Tategami in November 2004 and March 2005 to examine density and depth distribution of the seeds. Seeds were found as deep as 8 cm, but no deeper. On the other hand, empty seed coats were found as deep as 16 cm in both months. In the upper layers of the sediment to a depth of 8 cm, the average number of seed coats was 7960 ± 2997 m⁻² in November and 16,318 ± 2922 m⁻² in March. Deeper than 8 cm, the number of seed coats gradually decreased owing to decomposition, and none was found below 16 cm. We used the density of reproductive shoots and number of seeds per spadix in Tategami to estimate the fate of seeds and seed coats of the annual type of Z. marina in bottom sediments: out of the 6000 seeds m⁻² produced annually, 72% disappears from the stand and 28% is buried locally. The density and distribution of Z. marina seeds are among the most important factors in maintenance and propagation of the annual population at Tategami.     

Flavonoids from phlomis lychnitys

The new naturally occurring acylated flavone glucoside chrysoeriol-7-β-D-(3″-E-p-coumaroyl)glucoside and other flavonoids have been isolated from the aerial parts of Phlomis lychnitys, and identified by spectral techniques. Relationships between flavonoid pattern, phylogeny and geography in Phlomis are discussed.     

Comparison of Zostera marina and maerl community metabolism

The photosynthetic and repiratory metabolism of Zostera marina and maerl communities was compared, in the same area of the Bay of Brest in March–April, using benthic chambers. P–E curves for both oxygen and carbon were established for bottom irradiances between 0 and 525 μmol m⁻² s⁻¹. An exponential function was fitted to calculate daily production. Community metabolic quotients did not differ for maerl and seagrass beds. Community photosynthetic quotients were significantly higher (1.19) whereas community respiratory quotients were lower (0.70) than 1. Maerl and seagrass bed P–E curves mainly differed by the minimum saturating irradiance (E_k). Net community production was estimated to 26.8 mmol C m⁻² d⁻¹ for Z. marina meadows and 8.6 mmol C m⁻² d⁻¹ for maerl beds. The two communities can, therefore, be considered as autotrophic during the March–April period. Community respiration did not differ between Z. marina meadows and maerl beds, with an average value of 53.8 mmol C m⁻² d⁻¹ during a day. In similar environmental conditions, the production of maerl beds corresponds to approximately one third that of seagrass meadows. The maerl communities, therefore, form productive ecosystems, relevant to temperate coastal ecosystems functioning.     

Factors controlling Zostera marina L. growth in the eastern and western Pacific Ocean: Comparisons between Korea and Oregon,USA

Zostera marina distribution is circum-global and tolerates a wide range of environmental conditions. Consequently, it is likely that populations have adapted to local environmental conditions of light, temperature and nutrient supply. We compared Z. marina growth dynamics over a 2-year period in relation to environmental characters at Jindong Bay, South Korea and Yaquina Bay, Oregon, USA. Water temperature in Jindong Bay showed stronger seasonal variation (summer–winter ΔT = 20 °C) than in Yaquina Bay (summer–winter ΔT < 5 °C). Underwater irradiance in Jindong Bay exhibited a winter maximum, while in Yaquina Bay underwater light exhibited a summer maximum. Integrated annual underwater irradiance during 2003 was 2200 and 1200 mol photons m⁻² year⁻¹ in Korea and Oregon, respectively. Z. marina shoot density, biomass and integrated production were not significantly different between the two study sites. Seasonal Z. marina growth in Jindong Bay appeared to be controlled by temperature and light, while the growth pattern in Yaquina Bay suggested light regulation. Several seagrass parameters were correlated to phosphate concentrations, even though nutrients did not appear limiting. Despite differences in environmental factors, relative growth rates and temporal growth dynamics between study sites, integrated annual leaf production was quite similar at 335 and 353 g DW m⁻² year⁻¹ in the Jindong and Yaquina Bay study sites. We suggest that Z. marina net productivity is acclimated to the local environmental conditions and may be a general characteristic of temperate seagrass populations.     

Chemical constituents from Gentianella turkestanorum (Gentianaceae)

Phytochemical investigation of Gentianella turkestanorum (Gentianaceae) afforded nineteen compounds, including six xanthones (1–6), two triterpenoids (7–8), eight flavones (9–16) and three iridoids (17–19). Here, we firstly reported that 1-hydroxy-3,5-dimethoxyxanthone (4), 1, 8-dihydroxy-3-methoxyxanthone (5), apigenin (9), quercetin (10), luteolin-7-O-glucoside (12) and three other compounds (1, 8-dihydroxy-3-methoxyxanthone (5), apigenin-7-O-gluco (1″ → 3‴) glucoside (15) and luteolin-7-O-gluco (1″ → 3‴) glucoside (16)) could be isolated from G. turkestanorum. The occurrence of chemical data and the sequence data might be employed as common constituents of the genera Gentianella, Lomatogonium and Swertia.     

Characterization of microsatellite loci in the dwarf eelgrass Zostera noltii (Zosteraceae) and cross‐reactivity with Z. japonica

Zostera noltii is an important species of eelgrass occurring along European, north African, Mediterranean, Black Sea and Azov Sea coasts. Nine microsatellite loci were developed and no linkage disequilibrium was observed. Cross‐amplification was observed for all loci (polymorphic) in Z. japonica; only four loci amplified (monomorphic) in Z. marina.     

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.     

Congener comparison of native (Zostera marina) and introduced (Z. japonica) eelgrass at multiple scales within a Pacific Northwest estuary

A congener comparison of native (Zostera marina) and introduced (Zostera japonica) eelgrasses was conducted in Willapa Bay, Washington, USA. Along intertidal transects, Z. japonica (0.1–1.5 m above mean lower low water [MLLW]) occurred above Z. marina (<0.6 m MLLW). Both species declined in shoot length at higher elevation, but Z. japonica was always shorter (20 vs. 100 cm) and occurred at higher shoot density (>3,800 vs. <360 m^?2 in Z. marina). Z. japonica exhibited greater seasonal variation in biomass, with increases supported by both sustained asexual reproduction (rhizome branching) and recruitment from seeds (30 vs. <5% in Z. marina). Z. japonica’s successful invasion appears related to small size and high reproductive output, allowing it to spread quickly in a variable and stressful intertidal environment where competitive effects are low. Based on interannual changes in abundance, the native eelgrass has also recently increased in Willapa Bay, and one hypothesis involves “engineering” of suitable habitat at higher tidal elevations by Z. japonica.     

Photosynthetic temperature acclimation in two coexisting seagrasses,Zostera marina L. and Ruppia maritima L.

The physiological responses to temperature were investigated in two coexisting seagrasses, Zostera marina L. and Ruppia maritima L. sensu lato from the lower Chesapeake Bay, Virginia. Seven plant collections were made from March to July, 1983 at ambient temperatures of 8–30°C. Both species maintained relatively constant fresh: dry weight ratios and chlorophyll a:b ratios over the five-month period. Total chlorophyll content remained constant in Z. marina while that of R. maritima doubled from March to July. P_max values for both species increased with increasing temperature and declined at temperatures above 19 and 23°C (Z. marina and R. maritima, respectively). P_max values were significantly higher for R. maritima compared to Z. marina at temperatures above 19°C. Both short-term (laboratory) and long-term (in situ) responses to temperature regimes affected estimates of the photosynthetic capacity of both species. Thus, temperature histories of experimental material should be carefully considered when interpreting temperature effects on photosynthesis. This study provides support of the hypothesis that seasonal community dynamics of Z. marina and R. maritima in Chesapeake Bay are regulated in part by different responses to light and temperature.     

Current European Labyrinthula zosterae Are Not Virulent and Modulate Seagrass (Zostera marina) Defense Gene Expression

Pro- and eukaryotic microbes associated with multi-cellular organisms are receiving increasing attention as a driving factor in ecosystems. Endophytes in plants can change host performance by altering nutrient uptake, secondary metabolite production or defense mechanisms. Recent studies detected widespread prevalence of Labyrinthula zosterae in European Zostera marina meadows, a protist that allegedly caused a massive amphi-Atlantic seagrass die-off event in the 1930''s, while showing only limited virulence today. As a limiting factor for pathogenicity, we investigated genotype×genotype interactions of host and pathogen from different regions (10–100 km-scale) through reciprocal infection. Although the endophyte rapidly infected Z. marina, we found little evidence that Z. marina was negatively impacted by L. zosterae. Instead Z. marina showed enhanced leaf growth and kept endophyte abundance low. Moreover, we found almost no interaction of protist×eelgrass-origin on different parameters of L. zosterae virulence/Z. marina performance, and also no increase in mortality after experimental infection. In a target gene approach, we identified a significant down-regulation in the expression of 6/11 genes from the defense cascade of Z. marina after real-time quantitative PCR, revealing strong immune modulation of the host''s defense by a potential parasite for the first time in a marine plant. Nevertheless, one gene involved in phenol synthesis was strongly up-regulated, indicating that Z. marina plants were probably able to control the level of infection. There was no change in expression in a general stress indicator gene (HSP70). Mean L. zosterae abundances decreased below 10% after 16 days of experimental runtime. We conclude that under non-stress conditions L. zosterae infection in the study region is not associated with substantial virulence.     

The distribution of seagrass (Zostera noltii) in the Ria Formosa lagoon system and the implications of clam farming on its conservation

Ria Formosa lagoon in southern Portugal has an important population of seagrasses that includes Zostera noltii in the intertidal area. The area is classified as a Natural Park and supports a major economic activity – clam farming. This activity has a direct influence on Z. noltii populations by removal of seagrass beds and altering habitat. Geographic Information Systems and spatial analysis were used to produce the first distribution map of Z. noltii in the Ria Formosa and to analyse interactions between clam farming and the level of seagrass protection according to the Natural Park of Ria Formosa. Stakeholder analyses, using interviews, questionnaires and participant observation, were conducted to gain a better understanding of clam farming's influence on seagrass populations. Seagrass covers 45% of the intertidal area while clam farming covers 14%. An additional 75% of the total area of Z. noltii can be potentially converted into clam cultures. The current management of clam farming is largely ineffective, representing a significant obstacle to seagrass conservation.     

Seagrass feeding choices and digestive strategies of the herbivorous fish Sarpa salpa

This is the first study investigating the plant–herbivore interaction between Sarpa salpa, which has overgrazed seagrass transplants in Portugal, and the seagrasses Cymodocea nodosa, Zostera marina and Zostera noltii, which have been considered for restoration. When offered the choice between the three seagrasses in outdoor tanks, adult S. salpa clearly preferred Z. noltii. Testing the seagrasses separately, mean ± s.d. feeding rates ranged from 21 ± 11 g seagrass fresh mass kg^?1 fish mass day^?1 for Z. marina to 32 ± 9 g seagrass fresh mass kg^?1 fish mass day^?1 for C. nodosa and 40 ± 11 g seagrass fresh mass kg^?1 fish mass day^?1 for Z. noltii (temperature = 16° C). Food‐processing rate in S. salpa did not differ between seagrasses, and there was no evidence of a regulation of processing rate according to food intake. Seagrasses differed substantially in nitrogen content and C:N, with C. nodosa containing the highest nitrogen content and lowest C:N (2·5 ± 0·1% and 14·0 ± 1·0), followed by Z. noltii (2·1 ± 0·1% and 17·0 ± 1·0) and Z. marina (1·4 ± 0·1% and 26·0 ± 2·0). Food‐processing rate in S. salpa and the nutritional value of the seagrasses were not correlated with the observed feeding preference and rate. The study suggests that C. nodosa and Z. marina are less at risk of overgrazing by S. salpa and might thus be preferable to Z. noltii for seagrass restoration in areas with noticeable abundances of this fish.     

Seasonal variations of community production,respiration and biomass of different primary producers in an intertidal <Emphasis Type="Italic">Zostera noltii</Emphasis> bed (Western English Channel,France)

Gross primary production (GPP) and respiration (R) in an intertidal Zostera noltii (Hornemann, 1832) community were estimated each month from in situ CO₂ flux measurements during the emersion period in the Bay of Morlaix (France). Simultaneously, the Chlorophyll a biomass of Z. noltii leaves, associated epiphytes and sediment within the benthic chambers were also monitored. The significant positive exponential relationship established between R and the maximum daily temperature emphasized that temperature was a good predictor of seasonal variation in the community R in Z. noltii bed. In contrast, the amplitude of the fitted curve on GPP was low and represented <25% of the annual mean value (90.9 ± 15.2 mgC m⁻² h⁻¹). The Chlorophyll a biomass of sediment was high (133.70 ± 22.96 mg m⁻²) but it was likely constituted by detritus which did not contribute much to the community GPP. The Chlorophyll a biomass of associated epiphytes was higher in winter and varied over the year inversely with Z. noltii. Therefore, the asynchronous dynamic of primary producers could support a constant rate of production at community scale over the year.     

Desiccation,Moisture Content and Germination of Zostera marina L. Seed

Zostera marina is the only seagrass species whose seeds have been successfully used in large‐scale restoration. Although progress has been made in refining Z. marina restoration protocols, additional information on Z. marina seed physiology is necessary as the science of seagrass restoration evolves. We tested the germination rates of Z. marina seeds under different relative humidities and temperatures for different periods of time. Z. marina seed moisture content (MC) and germination rates were also tested when seeds were exposed to a temperature of 25°C and relative humidity of 50%. Z. marina seeds suffered higher mortality when exposed to lower relative humidity and higher temperature for longer period of exposure time. A significant negative correlation was detected between seed germination rate and MC. Z. marina seeds are sensitive to desiccation exposure and long periods of exposure to air should be prevented to minimize seed mortality when seeds are used in restoration projects.     

The effect of different primary producers on Hydrobia ulvae population dynamics: a case study in a temperate intertidal estuary

The effect of macroalgal blooms and the consequent disappearance of Zostera noltii meadows on Hydrobia ulvae population dynamics and production was studied in the Mondego estuary based on data obtained from January 1993 to September 1995. Sampling was carried out at a non-eutrophicated area, covered with Z. noltii, and also at an eutrophicated area, where seasonal Enteromorpha spp. blooms occur.Stable populations represented by individuals of all age classes were found only at the Z. noltii meadows throughout the study period. On the contrary, at the eutrophicated area, during most of the time, solely juveniles were present, with adults appearing only during the macroalgal bloom (>1.5 mm width).During the algal bloom (e.g. 1993), H. ulvae population density was clearly higher in the eutrophicated area due to the combined effect of stronger benthic recruitments (99% of veliger larvae newly recruited) and dispersion of juveniles proceeding from the Z. noltii meadows to this area. On the other hand, in the absence of macroalgae (spring of 1994), 98.9% of veliger larvae was recruited in the Z. noltii meadows. Therefore, H. ulvae seems to respond rapidly to macroalgal dynamics and its presence at the eutrophicated area depends on the existence of green macroalgae.H. ulvae presented the same benthic recruitment pattern at the two sampling areas, with new cohorts being produced in March, June, July and September. Depending on the time of the year in which the recruitment took place, cohorts showed different growth rhythms. However, after 12 months they reached a similar size.A three-generation life cycle involving a short-lived (16 months), fast growing spring generation, a medium growing (17-19 months) summer generation and a longer-lived (20 months) slower growing generation that overwinters is identified.As a general trend, productivity and mean population standing biomass were higher at the Z. noltii meadows, during the entire study, except for a short period, during the macroalgal bloom, when production was higher at the eutrophicated area. On the contrary, P/B? ratios were higher at the eutrophicated area. According to our results, H. ulvae population structure and yearly productivity are clearly affected by eutrophication, namely by the dynamics of macroalgal blooms.In the long run, we may infer that, following the disappearance of the Z. noltii meadows, due to eutrophication, H. ulvae would also tend to disappear, since reproductive adults were almost exclusively found in this area.