Paraskevi Malea

Bioaccumulation of metals by the green alga Ulva rigida from Thermaikos Gulf, Greece

Abstract Fe, Pb, Cu, Zn and Cd concentrations in the green alga Ulva rigida C. Agardh and in the sediment and seawater were studied at five stations of the Thermaikos Gulf, which is the recipient of domestic and industrial wastes. The relative abundance of metals in U. rigida and seawater (concerning Zn, Pb, Cu, Cd) decreased in the order: Fe>Zn>Pb>Cu>Cd, whereas in the sediment the order was the same except in the case of Pb>Fe>Zn. The seasonal variation of metal concentrations in the alga was significant for Cd and Zn. The mean values in the alga increased from spring to fall reaching a maximum in October or June (only for Cu). These variations are discussed in relation to growth dynamics, the concentrations of metals in the environment and tissue age. The concentrations of all metals in the alga were distributed uniformly among the five stations. There is a significant positive correlation in U. rigida between Pb–Cu, Fe–Cu and Cd–Pb. Pb and Cu concentrations in the alga were positively correlated with the respective concentrations in the sediment. Pb, Zn and Cd values in U. rigida from the study area exceeded those in the same or other species of the genus from other areas. U. rigida could be regarded as an indicator species for Pb, Zn and Cd. ©

Seasonal and local variations of metal concentrations in the seagrass Posidonia oceanica (L.) Delile in the Antikyra Gulf, Greece

Abstract The accumulation of Fe, Pb, Zn, Cu, Cd, Na, K, Ca and Mg in the leaves of seagrass Posidonia oceanica (L.) Delile was studied in the Gulf of Antikyra. The investigated area was of interest because of the specific composition of its substrate (involving bauxite) and also because of the nearby discharge wastes from an aluminium factory. All metal concentrations in the phanerogam were evenly distributed at the seven stations where there were adequate data for analysis. Cd, K and Ca displayed significant seasonal variation with high concentrations in P. oceanica during summer and autumn and low levels in winter and spring. This variation could have been the effect of age-dependent distribution of these metals in the leaves. Significant variation was also evident in Pb concentrations, which was probably associated with the growth dynamics of Posidonia oceanica. Other factors playing a role were the biomass of calcareous epiphytes on the plant leaves (as concerns Ca) and the interactions of metals for binding by the plant tissues. The dependence of metal concentrations in the plant on their concentrations in the environment (sediment and seawater) was also relevant. A significant correlation was found between Cd concentrations in the plant and those in sediment. A comparison between metal concentrations in P. oceanica of the Antikyra Gulf and those of the species belonging to the subfamily Posidonioideae from other areas is also presented. Cu, Pb, Cd, Fe, Ca and Mg concentrations in P. oceanica in the study area were generally high.

Use of the green alga Ulva rigida C. Agardh as an indicator species to reassess metal pollution in the Thermaikos Gulf, Greece, after 13 years

The concentrations of metals (Mn, Pb, Fe, Zn, Cu, Cd,Co, Ni, Cr, Na, K, Ca, Mg) were determined in thegreen alga Ulva rigida, in the sediment andseawater of Thermaikos Gulf (Greece) during monthlysamplings in 1994–1995. This Gulf is the recipientof domestic and industrial effluents. Pb, Fe, Cu, Coand Cr concentrations in U. rigida at the studyarea were higher than those 13 years earlier andapparently came from different sources than those forZn, Cd and Ni. The relative abundance of metals inthe alga decreased in the order: Mg > Na > K >Ca > Pb > Fe > Mn > Zn > Cr, Cu > Ni >Co > Cd. Only Cu concentrations in the alga fromKalochori and Cd ones from Viamyl showed significantseasonal changes. Cu and Cd concentrations ingeneral followed the same pattern of variation, withminimum values in winter-spring. This pattern isdiscussed in relation to growth dynamics and tissueage. Only Pb concentrations in the alga showed asignificant positive correlation with concentrationsin the seawater. There were both positive andnegative correlations among some metals in the alga. It is concluded that U. rigida can be used as anindicator species, especially for Pb.

Seasonal variation and local distribution of metals in the seagrass Halophila stipulacea (Forsk.) Aschers. In the Antikyra Gulf, Greece

Accumulation of Fe, Pb, Zn, Cu, Cd, Na, K, Ca and Mg concentrations by the seagrass Halophila stipulacea (Forsk.) Aschers. was studied at eight stations of the Antikyra Gulf (Viotia, Greece). This area was of interest because the contribution of bauxite to the mineral substrate and the discharge of an aluminium factorys wastes in it. Fe, Zn and K concentrations showed a significant seasonal variation with the same pattern (maximum mean value in summer and autumn), unlike Cu, Na and Mg concentrations which showed the opposite pattern. The observed patterns were mainly attributed to the dependence of metal concentrations in the plant on the tissue-age, the growth dynamics of the seagrass and the environment. All metal concentrations in the plant present uniform distribution in the inner part of the Gulf. The leaves of H. stipulacea accumulated higher Zn, Na, K and Mg concentrations than the stems, roots and rhizoids. There was a positive correlation between Cu, Zn, Cd and Na concentrations in the above-ground and below-ground plant parts.

Metal content in Enteromorpha linza (Linnaeus) in Thermaikos Gulf (Greece)

Local distribution and seasonal variation of Fe, Pb, Cu, Zn and Cd in Enteromorpha linza, in sediment and in seawater, were studied in Thermaikos Gulf (Greece), to which domestic sewage and industrial effluents are discharged. The mean metal concentrations (±SE) in the alga and seawater decreased in the following order: Fe>Zn>Pb>Cu>Cd and in the sediment: Pb>Fe>Zn>Cu>Cd. Only Cu concentrations in E. linza had a significant local distribution. Cadmium, Pb and Zn contents in E. linza were at maximum in the Harbour, whereas Cu and Fe were mininum in the Harbour and maximum at Biamyl station. These distributions were similar to those in the environment. Lead in E. linza correlated positively with Fe and Zn and negatively with Cd.Seasonal variation of most metals, except Cd, in E. linza was not significant. Lead, Cu, Zn and Fe variations followed a similar pattern, with minimum values in spring and an increase in autumn or winter, whereas Cd content was lower in January and at maximum in April. These variations reflect growth dynamics of the alga. Iron and Cu concentrations in E. linza from Thermaikos Gulf were lower but Pb, Zn and Cd higher than those in Enteromorpha spp. from other locations.

Thiol pools and glutathione redox ratios as possible indicators of copper toxicity in the green macroalgae Enteromorpha spp. from the Scheldt Estuary (SW Netherlands, Belgium) and Thermaikos Gulf (Greece, N Aegean Sea)

Defence mechanisms against Cu toxicity were examined in two dominant Enteromorpha species from two coastal water types. The macroalgae were collected at three locations in the eulittoral of the Scheldt Estuary (Netherlands, Belgium) and the Thermaikos Gulf (Greece). For 10 days E. prolifera (Scheldt) and E. linza (Thermaikos) were incubated in seawater media of different salinities: 6, 9, 23 psu and 25, 30, 35 psu, respectively. In one series, media were enriched with 100 μg Cu l-1; responses were compared with those in controls with no extra Cu added. Enteromorpha, which is frequently used as a monitor species for heavy metal contamination, had relatively high Cu tissue levels (0.5–3.8 μmol Cu gdwt-1). Cu levels in E. prolifera controls (Scheldt) decreased with salinity; this was not the case with Cu levels in E. linza controls (Thermaikos). During the 10-d incubation algal protein contents and tissue Cu were rather stable. In E. linza (Thermaikos) algal protein contents were significantly lower than those of E. prolifera (Scheldt), although there was no indication for nitrogen limitation in E. linza. E. linza also had much lower glutathione pools than E. prolifera. Only under acute Cu stress (metal addition) did E. prolifera synthesise metal-binding thiols (phytochelatins). Phytochelatin pools are not suitable as an indicator of the Cu levels in these algae. The glutathione redox ratio GSH:(GSH + 0.5GSSG) was used as an indicator of (Cu-induced) oxidative stress. In E. prolifera (Scheldt) this ratio decreased with algal Cu content (P <0.05), from ~0.5 to ~0.2. The average glutathione ratios in Enteromorpha from the Scheldt and Thermaikos showed some oxidative stress induction with increasing algal Cu contents, however more clearly if Cu was added. As this redox ratio can also be influenced by environmental factors such as irradiance and desiccation, it may not be useful as an indicator for Cu-induced oxidative stress in situ.

Annual versus perennial growth cycle in Ruppia maritima L.: temporal variation in population characteristics in Mediterranean lagoons (Monolimni and Drana Lagoons, Northern Aegean Sea)

Abstract A perennial population of Ruppia maritima in a permanent lagoon in the Evros Delta grew from April to October and reproduced during summer. Numbers of rhizome and stem internodes increased in spring–summer and in late summer–autumn, revealing two successive periods of both horizontal and vertical expansion; leaf density increased continuously until October (78,210 leaves m−2). An annual population in a temporary lagoon grew and reproduced from May to August, and died afterwards leaving seeds as the habitat temporarily dried. Numbers of rhizome internodes sharply increased only in August, while numbers of stem internodes increased in June, indicating that a slow horizontal expansion was followed by a fast and brief vertical expansion; subsequently a second intense horizontal expansion occurred; leaf density peaked in August (58,080 leaves m−2). Several characteristics increased after mid-spring, attaining similar maximum values in annual and perennial populations. However, the perennial population had larger leaves and higher root biomass, but lower reproductive organ biomass. Rhizome, stem and leaf biomass increased sharply in August (113.2 g dw m−2) in the annual population and progressively up to October (167.8 g dw m−2) in the perennial population. Using principal component analysis, growth and reproduction were found to be mainly affected by temperature.

The green seaweed Ulva rigida as a bioindicator of metals (Zn, Cu, Pb and Cd) in a low-salinity coastal environment

The capacity of Ulva rigida as a bioindicator of Zn, Cu, Pb and Cd contamination in oligohaline coastal waters was investigated. Metal concentrations in U. rigida, water and sediments and several environmental variables were measured seasonally at four stations in the coastal section of the Evros River Delta, Aegean Sea. All four metals in sediments had a significant local variation; in particular, they decreased with increasing distance from the fluvial end-member of Evros River. Mean Zn, Cu, Pb and Cd concentrations in U. rigida were 61.0, 22.4, 6.1 and 1.1 m gg -1 dry weight, respectively. This macroalga, compared to other co-occurring macroalgal species, had a high metal accumulation capacity, mainly of Cu and Cd. Local patterns of Zn, Cu and Pb in U. rigida were similar to those in sediments, while that of Cd was not; moreover, Cu and Pb in U. rigida correlated positively with their sediment contents, suggesting that this seaweed satisfies the basic prerequisite for a bioindicator of these elements in oligohaline environments. No metal in U. rigida displayed a significant seasonal variation, and there was no significant variation in ambient concentrations. A negative correlation between Zn in U. rigida and water salinity was found, probably due to both a higher metal burden in the freshwater flowing in the study area and to a decrease in Zn uptake with increasing salinity; Cd in the macroalga correlated negatively with water column ammonium.

Uptake of Cadmium and the Effect on Viability of Leaf Cells in the Seagrass Halophila stipulacea (Forsk.) Aschers.

The uptake of cadmium (Cd) in the leaves and lower parts of Halophila stipulacea (Forsk.) Aschers. was studied in laboratory experiments. Plants were incubated in seawater with 10 −4 -10 −9 mol L −1 Cd for 16 days. The toxicity of cadium was assessed by the leaf-cell viability test. At the lower Cd concentrations (10 −9 and 10 −8 mol L −1 ) all leaf-cells remained alive up to the end of experiment. In these solutions, Cd was taken up rapidly till the 4th day, after which the tissue contents stabilized; these «equilibrium» concentrations increased along with those in the medium. At the higher Cd levels the uptake continued after the 4th or 8th day; this may be due to cellular damage and fall of leaves in the highest solution (...)

Uptake of Cu, Cd, Zn, and Pb in Posidonia oceanica (Linnaeus) from Antikyra Gulf, Greece: preliminary note

Abstract The uptake of Cu, Zn, Cd and Pb was studied in the marine phanerogam Posidonia oceanica, sampled from seven stations in the Gulf of Antikyra, Biotia, Greece. There was a comparison between the mean values of the concentrations of the four heavy metals from all stations. There were no significant differences between stations in the accumulation of metals. However, there were seasonal variations: concentrations of Cu, Zn and Pb in Posidonia reached a maximum in the winter and in early spring and then decreased in the spring months to reach a minimum during the summer. This variation was only statistically significant for Cu; it was associated with the annual life-cycle of the plant. Cd also showed significant seasonal variation but concentrations reached a maximum during the summer and declined to a minimum during the spring.