Jacob Garty

Biomonitoring Atmospheric Heavy Metals with Lichens: Theory and Application

Recent records of environmental contamination noted a moderate decrease of SO2 pollution, whereas the burden of atmospheric heavy metals is still considerable. The present review refers to the entrapment, uptake, and accumulation of heavy metals by lichen thalli, made apparent by parameters of lichen vitality and stress. The particulate nature of airborne heavy metals is made evident by parameters referring to the entrapment of heavy-metal containing particles by lichen thalli. The mechanism of uptake of heavy metals, investigated by means of controlled experiments, refers to extracellular and intracellular uptake. The rate of absorption and the accumulation of heavy metals is dependent on morphological features of lichen thalli in addition to kind and intensity of emission sources and to nonanthropogenic factors such as climate and topography. The role of lichens as biomonitors is demonstrated by the case of lead. In contrast to data obtained by retrospective studies, using lichens as biomonitors of heavy metal pollution, performed in the 1970s, which indicated an increase of Pb as a result of the massive use of leaded gasoline, the subsequent disuse of this additive led to a decrease detected in later studies. The disparity of emission sources is illustrated by the case of Hg. Mercury is a product of anthropogenic activity in addition to its natural derivation. The dominance of the anthropogenic factors is made obvious by high levels of Hg recorded near chlor alkali plants and other industrial sites. The role of the substrate in the uptake and accumulation of heavy metals was investigated to detect its relative share. Airborne metals were, however, determinant factors in the metal content of lichen thalli. The interaction of contaminants and biomonitors has a definite physiological impact on the vitality of the biomonitors. Physiological processes of disintegration investigated in this context are degradation of cell membranes and chlorophyll, decrease of the quantum yield of photosynthesis, decrease of the photosynthetic rate, increase of stress-ethylene production, and severe ultrastructural change. Lichens exposed to heavy metal pollution exhibit changes of the spectral reflectance response, an increase of malondialdehyde (MDA), a decrease of ATP, and injury to enzymatic activities. A comparative analysis of data referring to the accumulation of airborne elements in lichens and of data referring to alterations in physiological parameters of lichen viability substantiates the validity of assessments of environmental quality.

NATURAL SELECTION CAUSES MICROSCALE ALLOZYME DIVERSITY IN WILD BARLEY AND A LICHEN AT 'EVOLUTION CANYON', MT. CARMEL, ISRAEL

Allozymic diversity was studied for proteins encoded by 28 putative loci in 170 plants of wild barley, Hordeum spontaneum, and for 13 loci in 78 different thalli of the lichen Caloplaca aurantia, from the Lower Nahal Oren microsite, Mt. Carmel, Israel, designated by us ‘Evolution Canyon’. The samples of wild barley were collected from six stations: three (upper, middle, lower) on the south-facing slope (SF-slope) and three (lower, middle, upper) on the north-facing slope (NF-slope). The samples of C. aurantia were collected from three stations: two (middle and upper) on the SF-slope and one (upper) on the NF-slope. Higher solar radiation on the SF- than on the NF-slope makes it warmer, drier, spatiotemporally more heterogeneous, and climatically more fluctuating and stressful. Consequently, it exhibits an open park forest representing an ‘African’ savanna landscape. Significant inter- and intraslope allozymic differentiation was found in both organisms with generally higher polymorphism, heterozygosity, allele and gene diversity on the more variable and stressful upper station of the SF-slope, as expected by the niche-width variation hypothesis, and the environmental theory of genetic diversity. Solar radiation, temperature and aridity stress caused interslope and intraslope differences on the SF-slope in genotypes and phenotypes of wild barley and the lichen at the ‘Evolution Canyon’ microsite, as was the case for beetles, diplopods and earthworms tested at the site. Diversifying natural (microclimatic) selection appears to be the major evolutionary driving force causing interslope and SF-intraslope adaptative genetic divergence. ‘Evolution Canyon’ proves an optimal model for unravelling evolution in action, across life and organizational levels.

Effect of low pH, heavy metals and anions on chlorophyll degradation in the lichen Ramalina duriaei (de not.) bagl.

Abstract Lichen thalli were soaked in water adjusted to pH 1.0–12.0 to study the influence of different pH conditions on the integrity of the photobionts chlorophyll. The ratio OD 435 nm/OD 415 nm, used to estimate the chlorophyll degradation, decreased after a 30 min treatment in water acidified to pH 1.0–2.0. Thalli were exposed to solutions containing potassium or heavy metal chlorides, sulfates and nitrates under acidic conditions, all of which exerted different degrees of chlorophyll damage. The chlorophyll integrity was especially affected following treatment of the thalli with Cu, Zn, Mn, Pb, Fe(II) and Fe(III) salts under pH 2.0. Under the same pH, SO42− combined with K+ proved more harmful to the photobiont chlorophyll than Cl− anions. After a treatment with CuCl2, a very low OD 435 nm/OD 415 nm ratio was obtained.

The impact of air pollution on the integrity of cell membranes and chlorophyll in the lichenRamalina duriaei (de not.) bagl. transplanted to industrial sites in Israel

The impact of air pollution on the integrity of cell membranes and chlorophyll in the lichenRamalina duriaei was studied. The lichen was transplanted from a relatively unpolluted site in Israel to a highly polluted area for a period of 10 months. The seasonal variation of the percentages of Mg as detected with the aid of scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX) on/in the cortical cells of the lichen was compared with changes in the chlorophyll integrity as expressed by the ratio OD 435 nm/OD 415 nm. The rate of damage of air pollution to cell membranes in the lichen was compared with the increase of S as detected on the surface of the lichen thalli retrieved from industrial sites. The present study indicates that the electric conductivity parameter reflecting the integrity of lichen cell membranes was found to express the cellular damage caused to lichen thalli transplanted to a steel smelter and to oil refineries. Symptoms of damage to cell membranes are detectable inR. duriaei long before any indication of damage becomes apparent in the photobiont chlorophyll. Magnesium seems to represent a significant leakage from intracellular sites of the thallus. The accumulation of sulfur on/in the cortical cells ofR. duriaei indicates that the biomonitoring sites at the Haifa Bay are contaminated by SO2.

Heavy metals in the lichen Caloplaca aurantia from urban, suburban and rural regions in Israel (a comparative study)

The content of eight heavy metals: Mn, Zn, Fe, Pb, Ni, Cu, Cr and Cd in the lichen Caloplaca aurantia growing on roof-tiles in urban, suburban and rural settlements in Israel has been evaluated. The data obtained and their statistical analysis indicated the following: (1) The content of all the above listed metals was generally higher in the lichen growing in ‘town’ than in ‘village’ areas; among these metals Ni and Zn were found most suitable for the distinction between ‘town’ and ‘village’ settlements. (2) Comparisons of the coefficient of variation of metal content values in ‘town’ versus ‘village’ furnished indications on the dispersion capacity of the metal particles. (3) Correlation analysis among the metals in ‘town’ and ‘village’ resulted in suggestive information on the emission sources. (4) Leaching tests indicated the tenacity of metal retainment and incorporation efficiency into the lichen tissue. Lichen species like C. aurantia, which grow both in ‘clean’ and metal contaminated areas are suggested as comparative monitors and for assessing periodical changes in metal output and concentrations.

Correlation between chlorophyll degradation and the amount of some elements in the lichen Ramalina duriaei (de not.) Jatta

Abstract The lichen Ramalina duriaei was transplanted to 13 biomonitoring stations for one year. The pigments of the transplanted lichen thalli and of indigenous R. duriaei thalli were then extracted with DMSO and the ratio OD 435/OD 415 used to estimate chlorophyll degradation in comparison with this ratio in control samples. The ratio values decreased with increase in amounts of Br, Pb, Fe and Ti. There was no significant correlation between the amount of sulphur, calcium, chlorine, strontium, zinc and phosphorus in the lichen and chlorophyll degradation.

Ecophysiology of Lichens in the Dry Valleys of Southern Victoria Land, Antarctica I. Microclimate of the Cryptoendolithic Lichen Habitat

Summary The microclimate of the cryptoendolithic lichen habitat was studied on Linnaeus Terrace (1,600–1,650 m alt.) in the mountainous region of the Antarctic dry valleys between Nov. 30 and Dec. 11, 1979. Three types of weather conditions occurred: 1) overcast, with periods of fog and snow, 2a) clear and windy, and 2b) clear with no winds. Air temperature was consistently below −6 °C. Relative humidity rose to 74% on an overcast day, but was lower (16–47%) on clear days. The northern face of sandstone rocks, mostly exposed to the sun, is colonized by lichens, while the southern, shaded face is free of lichens. Temperature of rocks with a southern exposure remained at all times below 0 °C. For rock surfaces exposed to the north, temperatures rose to 7 °C on clear days, but remained below 0 °C on overcast days. On a windy day, mean rock temperatures were significantly lower. Heat gradients were recorded in the upper 15 mm of the rock substrate. Photosynthetically active solar radiation at the rock surface amounted to over 1,000 μ E m −2 S −1 on an overcast day and to about 1,500 μ E m −2 S −1 on clear days. Approximately 1 % of incident light penetrates the rock to the level of the lichens. Relative humidity inside the rock was generally high and remained at 80 % or more for 5 days following snowfall. Meltwater entering the porous rocks is a water reservoir for the lichens. Measurements on rock samples collected in earlier years at Linnaeus Terrace indicated that the water content of rocks may not stay high at all times. Steep or vertical rock faces where snow cannot accumulate are dry and are not colonized by lichens. Water loss (evaporation) from the rock surface is of the same order of magnitude as that from an open water-saturated system. The results show that both temperature and humidity conditions are significantly more favorable for the life in the lichen zone inside the rock than on the surface. It was estimated tentatively that, on an overcast day, cryptoendolithic lichens may have been photosynthetically active for about 15 h, although these conditions were suboptimal. On a clear and windy day, photosynthesis may have been possible for 11 h, with 4 h optimal activity. On a clear, warm and calm day, the estimates amounted to 13.5 and 6.5 h, respectively.

Rehydration of the Lichen Ramalina lacera Results in Production of Reactive Oxygen Species and Nitric Oxide and a Decrease in Antioxidants

ABSTRACT Lichens are slow-growing associations of fungi and unicellular green algae or cyanobacteria. They are poikilohydric organisms whose lifestyle in many cases consists of alternating periods of desiccation, with low metabolic activity, and hydration, which induces increase in their metabolism. Lichens have apparently adapted to such extreme transitions between desiccation and rehydration, but the mechanisms that govern these adaptations are still poorly understood. In this study, the effect of rehydration on the production of reactive oxygen species and nitric oxide as well as low-molecular-weight antioxidants was investigated with the lichen Ramalina lacera. Rehydration of R. lacera resulted in the initiation of and a rapid increase in photosynthetic activity. Recovery of photosynthesis was accompanied by bursts of intracellular production of reactive oxygen species and nitric oxide. Laser-scanning confocal microscopy using dichlorofluorescein fluorescence revealed that formation of reactive oxygen species following rehydration was associated with both symbiotic partners of the lichen. The rate and extent of reactive oxygen species production were similar in the light and in the dark, suggesting a minor contribution of photosynthesis. Diaminofluorescein fluorescence, indicating nitric oxide formation, was detected only in fungal hyphae. Activities associated with rehydration did not have a deleterious effect on membrane integrity as assessed by measurement of electrolyte leakage, but water-soluble low-molecular-weight antioxidants decreased significantly.

Lichens as biomonitors around a coal-fired power station in Israel

In the present study epiphytic lichens were applied as biomonitors of air pollution to determine the environmental impact of a coal-fired power station. Thalli of the lichen Ramalina lacera (With.) J.R. Laund. growing on carob twigs (Ceratonia siliqua L.) were collected with their substrate in July 2000 in a relatively unpolluted forest near HaZorea, Ramoth Menashe, Northeast Israel, and transplanted to 10 biomonitoring sites in the vicinity of the coal-fired power station Oroth Rabin near the town of Hadera. The lichens were retrieved in January 2001. We examined the following parameters of lichen vitality: (a) potential quantum yield of photosynthesis expressed as fluorescence ratio F(v)/F(m), (b) stress-ethylene production, and (c) electric conductivity expressing integrity of cell membranes. Following an exposure of 7 months, the lichens were retrieved and physiological parameters and data of elemental content were analyzed comparatively. Electric conductivity values correlated positively with B, Fe, Mg, Mn, Na, Pb, S, Sn, and Ti content. Concentrations of stress-ethylene correlated positively with Al, Ba, Pb, S, and V content and negatively with Cu and Sn. F(v)/F(m) ratios correlated negatively with S content. Some of the heavy metals reached lower levels than those reported in the relevant literature despite a wind regime that should have blown pollutants toward the biomonitoring sites.

Characterization of Enzymatic Antioxidants in the Lichen Ramalina lacera and Their Response to Rehydration

ABSTRACT Lichens are slow-growing associations of fungi and green algae or cyanobacteria. This symbiotic association forms a common thallus that does not possess roots or a waxy cuticle and depends mainly on atmospheric input of mineral nutrients. The lifestyle of most lichens is composed of alternating periods of desiccation with low metabolic activity and hydration that induces increase in their metabolism. We have previously shown that rehydration of the naturally desiccated lichen Ramalina lacera resulted in a rapid increase in photosynthesis and was accompanied by a burst of intracellular production of reactive oxygen species and nitric oxide, as well as a transient decrease in water-soluble antioxidant capacity. We report here on enzymatic antioxidants of R. lacera and their response to rehydration. Native gel electrophoresis of crude extracts of R. lacera stained for superoxide dismutase (SOD) activity revealed four Fe-SOD and four Mn-SOD electromorphs that are synthesized by the alga, a Cu/Zn-SOD and a Mn-SOD that are the product of the fungus, and two catalases synthesized one by the fungus and the other by the algae. In addition, we detected glutathione reductase and glucose-6-phosphate dehydrogenase activities in crude extracts of R. lacera. Rehydration of the thalli resulted in a decrease in SOD activity of all forms, and a transient decrease in total catalase activity, as well as a decrease in the antioxidant auxiliary enzymes glutathione reductase and glucose-6-phosphate dehydrogenase.