STUDIES ON THE GIANT KELP,MACROCYSTIS. II. REPRODUCTION

Neushul , M. (U. Washington, Seattle.) Studies on the giant kelp, Macrocystis. II. Reproduction. Amer. Jour. Bot. 50(4): 354–359. Illus. 1963.—The reproduction of Macrocystis pyrifera was studied in the sea and in the laboratory. The estimated minimum time needed for the completion of the sexual life history of Macrocystis pyrifera in La Jolla, California, is from 12 to 14 months. Young sporophytes begin fruiting when they have from 4 to 8 stipes and a somatic frond weight of from 8 to 10 kg. The behavior of abscised sporophylls in laboratory tanks, as well as their morphology and coloration, strongly suggests an interrelationship between the translocation of photosynthetic products and fructification.     

Gametogenesis and chromosome number in Postelsia palmaeformis (Laminariales, Phaeophyceae)

Gametophytes of the ‘sea palm’, the kelp Postelsia palmaeformis Ruprecht, produced gametes whether or not chelated iron was supplied in the culture medium, in contrast to the inhibition of gametogenesis seen with the absence of iron in many other kelps. As gametogenesis proceeded, every cell of the gametophytes was converted into a gamete so that the gametophytes did not continue to grow vegetatively. The portion of the life history from spore release through germination, gametophyte growth, gametogenesis, fertilization and growth of the young sporophyte was completed in 9–10 days under laboratory conditions. Chromosome counts showed that sporophytes had a diploid number of 26–34 chromosomes while sporangia and gametophytes had a haploid number of 14–17 chromosomes, indicating a typical haplodiplophasic life history as seen in other Laminariales.     

EFFECTS OF SHADING BY ADULTS ON THE GROWTH OF BLADE-STAGE MACROCYSTIS PYRZFERA (PHAEOPHYTA) DURING AND AFTER THE 1982–1984 EL NIÑO1

The effect of shading by an adult canopy on blade-stage Macrocystis pyrifera (L.) C. A. Agardh was estimated by comparing the average growth rate of individuals under a canopy to that of individuals in a canopy gap. This comparison was made in 1983 during a strong El Niño and again in 1986 after the El Niño. Estimated nutrient concentrations in 1983 were two orders of magnitude below those in 1986, whereas ambient light levels were over 3 times higher. The kelp canopy caused similar proportional light reductions (20–30%) during both years. Blades grew 18% slower under the canopy than in the clearing in 1983 and about 77% slower under the canopy in 1986. Blade-stage individuals grew at the same rates in clearings in 1983 and 1986. Regardless of shading, the average growth rate of blade-stage kelp under the ambient, low-nutrient conditions of 1983 was higher than that later observed for multifronded juveniles during the same El Niño. The growth of blade-stage kelp was more like that of larger juveniles growing under high-nutrient conditions. The difference may be due to greater concentrations of nutrients very near the sea floor where single blades are growing compared to concentrations higher in the water column where larger kelp have most of their tissues.     

Production of <Emphasis Type="Italic">Macrocystis pyrifera</Emphasis> (Laminariales; Phaeophyceae) in northern Chile on spore-based culture

Since the establishment of abalone farming, there has been an increase in the demand for Macrocystis as a food source. Therefore, the pressure on natural stock has also augmented and the sustainability of the actual harvesting practices has been questioned. In this article, an attempt to farm Macrocystis pyrifera by zoospores in northern Chile is described; initially under laboratory conditions and subsequently by cultivation in the sea. The experiments were executed during 1 year and two different cultivation methodologies were used: a direct and an indirect method. A maximum frond length of 175 cm was reached and 22 kg m⁻¹of rope was produced after 120 to 150 days of cultivation in the sea. The algae grew under both methodologies, and no differences in algal length and biomass were detected between the two cultivation systems. However, the direct culture method can be recommended for productive and practical reasons.     

ETIOLOGY AND DEVELOPMENT OF HYPERPLASIA INDUCED BY STREBLONEMA SP. (PHAEOPHYTA) ON MEMBERS OF THE LAMINARIALES (PHAEOPHYTA)1

Filaments of Streblonema sp. isolated from hyperplasia (galls) on Nereocystis luetkeana (Mert.) Post. et Rupr. induced similar gall growths when inoculated on young sporophytes of Nereocystis luetkeana, Macrocystis integrifolia Bory, and Laminaria japonica Aresch. Filaments were irregularly branched and uniseriate with cells 5–8 μm in diameter and 10–30 μm long. Growth under varied cultured conditions produced unilocular sporangia. Zoospores released from the sporangia germinated into identical filaments which also formed unilocular sporangia. Gall tissue originated from the innermost cells of the epidermal meristematic zone. When infected these cells divided in an irregular and unorganized manner. The resulting structure was a pronounced departure from normal morphology.     

Removal of phosphate by the green seaweed <Emphasis Type="Italic">Ulva lactuca</Emphasis> in a small-scale sewage treatment plant (Ios Island,Aegean Sea,Greece)

In the present study, the use of seaweeds for phosphate absorption was examined as a tertiary treatment in sewage treatment plants, to improve the water quality and reduce eutrophication risks. The data came from both laboratory and field experiments that took place on Ios Island sewage treatment plant. Three different macroalgae were tested and Ulva lactuca was finally chosen thanks to its high survivability in low salinity waters. Since the main restrictive factor was low salinity, we initially established the ratio of seawater:effluent that combined satisfactory viability with maximum phosphate absorption. The biomass growth under these conditions was also examined. Based on the above results, we designed a continuous-flow system with a 1/4 volume per hour water turnover, in a mixture of 60% sewage effluent: 40% sea water and 30 g L^-1 initial biomass of U. lactuca that must be renewed every 10 days. Under these conditions and time frame, the phosphate content of the effluent was reduced by about 50%.     

Light-Induced Adaptive Responses under Greenhouse and Controlled Conditions in the Fern Pteris cretica var. ouvrardii

The photosynthetic capabilities of the fern Pteris cretica var. ouvrardii were analysed by means of the light response curves of CO₂ exchange. In control growth conditions (greenhouse, low-light: 20–32 W m^?2); photosynthesis was shown to be saturated for low irradiance (20–25 W m^?2); the saturating photosynthetic rate, very low as compared to higher plants, was due to an extremely high intracellular resistance. When irradiance during the photosynthesis measurement was higher than 60–80 W m^?2, a constant decline of net CO₂ exchange as a function of time was observed. When irradiance during growth was enhanced, whether in greenhouse (20–250 W m^?2) or controlled (62 W m^?2) conditions, the first fronds that had developed in the new condition from the crosier stage exhibited decreased net maximal photosynthesis and a decreased efficiency in low light, but saturating irradiance was unmodified. However, the fronds whose entire differentiation (from meristem) occurred under these moderate irradiances (plants defoliated of all fronds and crosiers at the time of transfer), possessed more efficient photosynthetic characteristics than control plants. Pteris is able to grow under extreme shade conditions (4–8 W m^?2); light saturating photosynthesis and efficiency are higher under extreme shade than under control conditions. These adaptive characteristics indicate that Pteris is a well-adapted shade species.     

Temperature and salinity regulation of growth and gas exchange of Salicornia fruticosa (L.) L.

Summary Salicornia fruticosa was collected from a salt marsh on the Mediterranean sea coast in Libya. Growth and gas exchange of this C₃ species were monitered in plants pretreated at various NaCl concentrations (0, 171, 342, 513 and 855 mM). Maximum growth was at 171 mM NaCl under cool growth conditions (20/10° C) and at 342 mM NaCl under warm growth conditions (30/15° C) with minimum growth at 0 mM NaCl (control). Net photosynthesis (Pn) was greatest in plants grown in 171 mM NaCl with plants grown at 513 and 855 mM having lowest rates. Maximum Pn was at 20–25° C shoot temperatures with statistically significant reductions at 30° C in control plants while salt treated plants showed such reductions at 35° C. Salt treatments increased dark respiration over the control at 171 and 342 mM but reduced it at higher concentrations. Photorespiration was reduced by salt treatment and increased by increasing shoot temperature. Greatest transpiration was in 171 mM NaCl treated plants and increasing shoot temperature increased transpiration in all treatments. Stomatal resistance to CO₂ influx was influenced only moderately by temperature while increasing salinity resulted in increased stomatal resistance. In general both temperature and salinity increased the mesophyll resistance to CO₂ influx. The species seems adapted to the warm saline habitat along the Mediterranean sea coast, at least partially, by its ability to maintain relatively high Pn at moderate NaCl concentrations over a broad range of shoot temperatures.     

Effects of various environmental conditions on growth and reproduction of the sea hareAplysia oculifera (Adams and Reeve, 1850)

We studied the influences of food type, food quantity, water currents, starvation and light on growth and reproduction of the sea hareaplysia oculifera (Adams and Reeve, 1850) under laboratory conditions. Out of five species of algae served as food,Enteromorpha intestinalis promoted the fastest growth ofA. oculifera, Ulva spp. slower growth,Cladophora sp. allowed maintenance spp. slower growth,Cladophora sp. allowed maintenance of steady body mass, and the brown algaeColpomenia sp. andPadina pavonia were rejected by the sea hares. When sea hares were exposed to four levels of water currents, growth rates decreased as water currents increased. Sea hares fed on 50% ration grew slower than those fed on 100% ration (ad libitum). During 10 days of starvation sea hares lost weight, but when subsequently fed 100% ration they recovered and grew at a rate similar to those fed continuously with 100% ration. Under shade and under natural sunlight sea hares grew at the same rates. Whenever growth rates decreased, sea hares began to spawn at a smaller body size.A. oculifera demonstrated physiological plasticity that adapted them to varied and unpredictable environmental conditions. At different conditions of food availability they applied different tactics of resource allocation between growth and reproduction.     

An immuno-marking technique for thrips

Rabbit immunoglobulin G (R‐IgG) was used successfully as an external mark for thrips. Females of both Thrips tabaci Lindeman and Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) were marked with 1 mg ml^?1 R‐IgG solution with 1%‘Tween 20’ by the contact exposure method. Determining the retention of the mark was by running the rinsing solution of individual thrips in an enzyme‐linked immunosorbent assay (ELISA). The sandwich ELISA method was used with an additional biotin–avidin step. The threshold for a positive marking score was defined as three times the mean optical density readings of the negative control thrips. Under laboratory conditions, on bean pods, all marked thrips scored positive up to 6 days after marking (DAM). When marked thrips were kept in the laboratory on marigold flowers for 2 days, they all scored positive. When marked and unmarked thrips were placed together on these flowers, the mark was transferred to 10–20% of the unmarked thrips and they became positive. Under field conditions, on sticky traps covered with water‐base glue, 100, 80, and 20% of the marked T. tabaci scored positive by the 3rd, 6th, and 9th DAM, respectively. Under the same conditions 100, 90, and 10% of the marked F. occidentalis scored positive by the 3rd, 6th, and 9th DAM, respectively. The retention of the R‐IgG decreased significantly under conditions of wetness and high humidity. After 6 days on chive plants kept at 80–100% r.h., all marked thrips scored negative while on plants kept at 40–60% r.h., 85% of the marked thrips scored positive. Rabbit IgG can be used as an external marker for thrips. The suitability of this marking method for dispersal studies of these important pests needs to be evaluated.     

Developpement de Leveillula taurica en Fonction des Facteurs Climatiques et Sensibilité de Capsicum annuumà Differents Stades Végétatifs

Influence of environmental factors on the development of L. taurica on pepper genotypes To our knowledge, the effects of certain environmental factors, as well as those of host genotype on the development of Leveillula taurica on pepper have not been extensively investigated. To study effects of the above factors on the development of this parasite, two Capsicum genotypes (‘Yolo Wonder' and ‘line 815’) have been tested and compared under different light and relative humidity conditions. In vitro, optimal light intensity for spore germination was situated between 20 and 80 μE/m²/s, and for the growth of germ tubes it was 20 μE/m²/s. In vivo, under continous darkness during 20 days, the different organs of the hosts were only slightly affected. Under light conditions, during 20 days after inoculation, the highest infection level on leaves was observed at 20 μE/m²/s, (60 % of leaves) while with the cotyledons it was observed between 20–80 μE/m²/s. Effects of relative humidity on the development of this parasite were also studied on ‘Yolo Wonder’ and ‘line 815′. With relative humidity below 50 %, 60 % of ‘Yolo Wonder’ plants and 33 % of ‘line 815’ were infected. Under conditions of saturated relative humidity, the level of infection was the inverse, i. e. 13 and 55 %, respectively. Moreover, ‘Yolo Wonder’ plants were found more or less susceptible to infection with L. taurica during their different development stages. At the cotyledon stage all plants were infected. After this stage, up to flowering, susceptibility depended on the physiological age of the leaves. First leaves (older leaves) were not infected, while young ones near the apex became progressively susceptible.     

A SHORT-TERM DEMOGRAPHIC STUDY OF CYSTOSEIRA OSMUNDACEA (FUCALES: CYSTOSEIRACEAE) IN CENTRAL CALIFORNIA1

Several demographic features were examined in the field over a period of eleven months for the subtidal alga Cystoseira osmundacea (Turner) C. Agardh at two localities near Monterey, California. This species showed a restricted distribution with depth, with peak average numbers of 3–4 plants per m² occurring at 6–8 m and forming a dense canopy on the surface of the sea. Below 10 m depth, there was a decline in the abundance of plants and also in the proportion of plants which bore seasonal fronds and reproductive tissue. Macrocystis pyrifera (L.) C. Agardh plants were also common at both localities. There was a negative correlation between the presence of this species and C. osmundacea at a scale of 1 m², but no correlation at 4, 9, and 25 m². Cohorts of C. osmundacea were mapped and tagged at one locality. The plants had markedly seasonal growth, with the greatest elongation of fronds occurring between March and June. Dense surface canopies and reproductive tissue were present during the summer months of June–August. These seasonal fronds were shed during September, leaving small perennial holdfasts and fronds. Plants were strictly dioecious, and there was a one-to-one ratio of male to female plants at both localities. Length-dry weight relationships showed that the largest plants had over 80% of their weight invested in seasonal fronds (vegetative plus reproductive tissue). Recruits of C. osmundacea at one locality appeared during September–November only in areas cleared to bare substratum. There was 15% survival of recruits between November and the following May, while 98% of the original mapped cohort survived for the 11 months of the study.     

Effects of growth temperature and nitrogen nutrition on expression of C3–C4 intermediate traits in Chenopodium album

Proto-Kranz plants represent an initial phase in the evolution from C₃ to C₃–C₄ intermediate to C₄ plants. The ecological and adaptive aspects of C₃–C₄ plants would provide an important clue to understand the evolution of C₃–C₄ plants. We investigated whether growth temperature and nitrogen (N) nutrition influence the expression of C₃–C₄ traits in Chenopodium album (proto-Kranz) in comparison with Chenopodium quinoa (C₃). Plants were grown during 5 weeks at 20 or 30 °C under standard or low N supply levels (referred to as 20SN, 20LN, 30SN, and 30LN). Net photosynthetic rate and leaf N content were higher in 20SN and 30SN plants than in 20LN and 30LN plants of C. album but did not differ among growth conditions in C. quinoa. The CO₂ compensation point (Γ) of C. album was lowest in 30LN plants (36 µmol mol^–1), highest in 20SN plants (51 µmol mol^–1), and intermediate in 20LN and 30SN plants, whereas Γ of C. quinoa did not differ among the growth conditions (51–52 µmol mol^–1). The anatomical structure of leaves was not considerably affected by growth conditions in either species. However, ultrastructural observations in C. album showed that the number of mitochondria per mesophyll or bundle sheath (BS) cell was lower in 20LN and 30LN plants than in 20SN and 30SN plants. Immunohistochemical observations revealed that lower accumulation level of P-protein of glycine decarboxylase (GDC-P) in mesophyll mitochondria than in BS mitochondria is the major factor causing the decrease in Γ values in C. album plants grown under low N supply and high temperature. These results suggest that high growth temperature and low N supply lead to the expression of C₃–C₄ traits (the reduction of Γ) in the proto-Kranz plants of C. album through the regulation of GDC-P expression.

     

THE LIFE CYCLE OE SARGASSUM HORNERI (PHAEOPHYTA) IN LABORATORY CULTURE1

The life cycle of the large dioecious alga Sargassum horneri (Turner) C. Agardh was completed in unialgal culture by controlling photoperiod in relation to the phase of growth. Embryos isolated from a naturally grown female thallus gave rise to early germlings that rapidly formed blades under both short-day (9 h L) and long-day (15 h L) conditions at 20° C Shoot elongation, which followed early blade formation, occurred under the short-day conditions hut not under the long-day conditions. Functional female and male receptacles developed when thalli 8–14 cm long grown under the short-day conditions were transferred to the long-day conditions; gamete fusion occurred when male and female thalli were grown together. Fertilized oospores gave rise to normal thalli in a manner similar to that for in situ plants. Thus, the life cycle of S. horneri was completed in laboratory culture.     

Simulated sea level change alters anatomy, physiology, growth, and reproduction of red mangrove (Rhizophora mangle L.)

Tropical coastal forests – mangroves – will be one of the first ecosystems to be affected by altered sea levels accompanying global climate change. Responses of mangrove forests to changing sea levels depend on reactions of individual plants, yet such responses have not been addressed experimentally. We report data from a long-term greenhouse study that assessed physiological and individual growth responses of the dominant neotropical mangrove, Rhizophora mangle, to levels of inundation expected to occur in the Caribbean within 50–100 years. In this study, we grew potted plants in tanks with simulated semidiurnal (twice daily) high tides that approximated current conditions (MW plants), a 16-cm increase in sea level (LW plants), and a 16-cm decrease in sea level (HW plants). The experiment lasted 2½ years, beginning with mangrove seedlings and terminating after plants began to reproduce. Environmental (air temperature, relative humidity, photosynthetically active radiation) and edaphic conditions (pH, redox, soil sulfide) approximated field conditions in Belize, the source locale for the seedlings. HW plants were shorter and narrower, and produced fewer branches and leaves, responses correlated with the development of acid-sulfide soils in their pots. LW plants initially grew more rapidly than MW plants. However, the growth of LW plants slowed dramatically once they reached the sapling stage, and by the end of the experiment, MW plants were 10–20% larger in all measured growth parameters. Plants did not exhibit differences in allometric growth as a function of inundation. Anatomical characteristics of leaves did not differ among treatments. Both foliar C:N and root porosity decreased from LW through MW to HW. Relative to LW and HW plants, MW plants had 1–7% fewer stomata/mm², 6–21% greater maximum photosynthetic rates, 3–23% greater absolute relative growth rates (RGRs), and a 30% higher RGR for a given increase in net assimilation rate. Reduced growth of R. mangle under realistic conditions approximating future inundation depths likely will temper projected increased growth of this species under concomitant increases in the atmospheric concentration of CO₂.     

Response of the invasive pompom weed,Campuloclinium macrocephalum (Asteraceae), to feeding by the foliage-deforming thrips Liothrips tractabilis (Phlaeothripidae) under outdoor conditions in South Africa

The foliage-deforming thrips Liothrips tractabilis Mound and Pereyra (Thysanoptera: Phlaeothripidae) was recently released in South Africa as the first classical biological control agent against the invasive South American herb, Campuloclinium macrocephalum (Less.) DC. (Asteraceae). The impact of the thrips on young plants and regrowth of C. macrocephalum was assessed under outdoor conditions, and the results were compared to those of earlier laboratory trials that were conducted while the agent was still under investigation in quarantine. The outdoor trials revealed that feeding by L. tractabilis reduced the growth and biomass accumulation of C. macrocephalum, particularly in young plants and to a lesser extent in regrowth, which was largely consistent with the results of the earlier laboratory trials. Thrips-infested young plants were significantly shorter, produced fewer leaves and displayed significantly lower wet root masses and lower below- and above-ground dry masses, compared to the control plants. Although thrips-infested regrowth were significantly shorter, produced fewer leaves and displayed significantly lower above-ground dry masses than the control plants, the differences in wet root masses and below-ground dry masses were not significant. Although laboratory-based impact assessments are not necessarily an accurate reflection of field impact, in this instance the results were largely validated by the outdoor assessments. The results suggest that L. tractabilis will have a negative impact on C. macrocephalum populations in the field and thus contribute towards the weed’s biological control. The establishment of L. tractabilis has recently been confirmed in South Africa, providing the opportunity to verify these predictions.     

Kelp rafts in the Southern Ocean

Kelp rafts were surveyed during three summer traverses between Hobart and Macquarie Island (subAntarctic) to determine the potential for dispersal of kelp‐associated macroinvertebrates across the latitudes of 46–53°S. Rafts of Durvillaea antarctica dominated the sightings (94% of rafts) and extrapolations to the full Southern Ocean between these latitudes indicate a figure of over 70 million rafts afloat at any one time, 20 million of which support a holdfast, the habitat supporting the highest faunal diversity in attached kelp plants. In contrast, few, small rafts of Macrocystis pyrifera were observed. The potential for dispersal of fauna is presumed to be related to the species of kelp with which they are associated. Empirical studies of survival of animals while drifting at sea, and also on making land‐fall, are required to allow fuller interpretation of the significance of these findings.     

IN VITRO SOMATIC EMBRYOGENESIS AND REGENERATION OF SOMATIC EMBRYOS FROM PIGMENTED CALLUS OF KAPPAPHYCUS ALVAREZII (DOTY) DOTY (RHODOPHYTA,GIGARTINALES)1

In vitro somatic embryogenesis and regeneration of somatic embryos to whole plants through micropropagules was successfully demonstrated from pigmented uniseriate filamentous callus of Kappaphycus alvarezii (Doty) Doty in axenic cultures. More than 80% of the explants cultured on 1.5% (w/v) agar‐solidified Provasoli enriched seawater (PES) medium showed callus development. The callus induction rate was consistently higher for laboratory‐adapted plants. The excised callus grew well in subcultures and maintained its growth for prolonged periods if transferred to fresh medium in regular intervals. Some subcultured calli (<10%) did undergo transformation and produced densely pigmented spherical or oval‐shaped micropropagules (1–5 mm in diameter) that subsequently developed into young plantlets in liquid PES medium. The micropropagule production was further improved through somatic embryogenesis by a novel method of culturing thin slices of pigmented callus with naphthaleneacetic acid (NAA) or a mixture of NAA and 6‐benzylaminopurine. Transfer of embryogenic callus along with tiny somatic embryos to liquid medium and swirling on orbital shaker facilitated rapid growth and morphogenesis of somatic embryos into micropropagules that grew into whole plants in subsequent cultivation in the sea. The daily growth rate of one tissue cultured plant was monitored for seven generations in field and found to be as high as 1.5–1.8 times over farmed plants. The prolific somatic embryogenesis together with high germination potential of somatic embryos observed in this study offers a promising tool for rapid and mass clonal production of seed stock of Kappaphycus for commercial farming.     

Distribution of Rhopalosiphum padi (Hornoptera: Aphididae) on spring barley plants

The distribution of Rhopalosiphum padi on spring barley plants in the field and the laboratory is described. Aphids fed mainly on the lower parts of the plants in both the field and the laboratory. A relatively large proportion of the field population was found beneath the soil surface early in the season. In the laboratory, aphids preferred the stem base and auricles of young and old plants respectively. The highest soluble nitrogen concentration was found in the stem base of young plants. The aphids avoided temperatures above 25°C in a temperature gradient (20°C-40°C). The soil surface temperature in a barley stand can reach lethal levels for aphids during clear days early in the season. It is concluded that the preference of R. padi for the lower part of young spring barley plants is mainly a consequence of the stem base being the most nutritious part of the plant and that a harsh microclimate possibly forces the aphids beneath the soil surface. This tendency to feed near or below soil level must be taken into account when assessing field densities of R. padi.     

Effects of copper enrichment on survival,growth and photosynthetic pigment of seedlings and young plants of the eelgrass Zostera marina

Copper (Cu²⁺) is an essential nutrient for plants but toxic at high concentrations. We subjected seedlings and young plants of eelgrass Zostera marina to different seawater Cu concentrations (3, 4, 5, 10, 30 and 50?µg?l^?1) for over 30 days under controlled laboratory conditions. Natural seawater without added Cu (3?µg?l^?1) was used as reference seawater. We measured plant response in terms of survivorship, morphology, growth, productivity and leaf pigment concentration. Survival analysis combined with morphological, dynamic and productive assessment suggested that the optimum seawater Cu concentration for the establishment of Z. marina seedlings and young plants is 4?μg?l^?1. The photosynthetic response of young plants to copper enrichment, including an increase in chlorophyll content under low Cu concentration treatment but significant decrease when treated with high concentrations of Cu, is similar to those reported for other seagrass species. NOEC (no observed effect concentration), LOEC (lowest observed effect concentration) and LC₅₀ (lethal concentration that caused an increase in mortality to 50% of that of the control) values of seedlings were significantly lower than those of young plants, implying a reduced Cu tolerance to high concentrations (>10?μg?l^?1). This study provides data that could prove helpful in the development of successful eelgrass restoration and conservation.