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 heav...

http://img2.tapuz.co.il/CommunaFiles/40529686.pdf

Biomonitoring Atmospheric Heavy Metals with Lichens: Theory and Application

Lichens are well known as sensitive indicators of air pollution, particularly for sulfur dioxide. In part, this is related to their unique biology. Evidence supporting this assertion goes back well over 100 years and is based on extensive field and laboratory studies. In general, these studies reinforce each other, but for oxidants the data are not entirely consistent, and consequently require further work. At the least, lichens appear to be less sensitive to oxidants than vascular plants. Acid precipitation effects are closely related to SO2 effects. The mechanistic basis for SO2 effects is briefly reviewed. The extreme sensitivity of lichens to SO2 is partially related to their ability to absorb more SO2 for a given concentration than typical vascular plants. The use of lichens as long-term integrators of elemental deposition patterns is well established, but their use for monitoring dry deposition has only recently been recognized. Air pollutants adversely impact not only growth, reproductive potential, and morphology, but also a wide variety of physiological processes, which also becomes reflected in ultrastructural changes. The impact of organic pollutants on lichens is largely undocumented and is a prime area for future work, even though much work remains to be accomplished with the traditionally recognized air pollutants.

https://link.springer.com/content/pdf/10.1007/BF00607929

Lichens as Indicators of Air Pollution

The effect of Cu, Zn and Pb on the chlorophyll content of the lichens Cladonia convoluta and Cladonia rangiformis

This essay is part of the second presentation of an educational project of the American Society of Zoologists. The purpose of the project is to offer suggestions for improving the first-year biology courses in the universities. The method consists of emphasizing the conceptual framework of the biological sciences, showing how scientific information is obtained and evaluated, pointing out the strengths and limitations of scientific procedures, and above all showing the relevance of science for human hopes and welfare. Each year a major topic will be considered. Last year it was Evolutionary Biology . This year it is Human Ecology .

/pdf/science-as-a-way-of-knowing-human-ecology-3litnz9bbl.pdf

Science as a Way of Knowing—Human Ecology

An efficient method for estimating bryophyte diversity in forest stands must consider more than just the dominant forest mesohabitat. We compared two methodologies commonly used for estimating diversity in forest ecosystems. Floristic habitat sampling (FHS) utilizes stratification of all forest mesohabitats, which includes the natural diversity of microhabitats found within and stratifies a mosaic of mesohabitats (e.g. forest, streams, seeps, and cliffs) and microhabitats (e.g. rocks logs, etc.) that are often not considered in forest research projects that use plot sampling to estimate species diversity. In Canadian cedar hemlock forest, FHS methodology recorded more than twice as many bryophyte species as plot sampling (PS). A comparison of the dominant forest mesohabitat concluded that plot sampling was not as efficient as FHS in estimating bryophyte diversity and that plot sampling can result in different interpretations of species diversity. Rare species ordination of stands sampled using FHS showed strong clustering of sites with respect to biogeoclimatic zones and age since the last major disturbance (fire or logging) as compared with rare species ordinations from PS data, which showed no delineation of stands along temporal gradients. Plot sampling has many useful applications in ecology, but floristic habitat sampling is more efficient for quantifying overall bryophyte diversity. FHS provides an excellent way to record a comprehensive list of species.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1366-9516.2005.00123.x

The ones we left behind: Comparing plot sampling and floristic habitat sampling for estimating bryophyte diversity

Lichens were surveyed at 128 sites around a coal-fired power plant in an unurbanized region of southeastern Ohio. Corticolous lichens were found to be useful indicators of air quality while terricolous and saxicolous species were not. Mapping revealed void areas in the distribution of Parmelia caperata (L.) Ach. and P. rudecta Ach. The area of affect was smaller than most of those re- ported for cities, and in this hilly region, site elevation was found to be an impor- tant factor influencing lichen distribution. Many previous studies have related disappearance of lichens to a deterioration of air quality in cities. These studies have been done around large urban and industrial areas, primarily in Europe and Canada. The recent book edited by Ferry et al. (1973) contains an excellent summary of lichen studies to date. Most workers agree that the disappear- ance of lichens as an industrial area is approached correlates with an increase in atmo- spheric sulfur dioxide (SO,). However, the situation in urban and industrial areas is very complex. Smoke is emitted from a number of low-level sources, and usually con- tains a mixture of phytotoxic compounds. In addition, city factors such as lower humid- ity, higher temperatures, and lower availability of suitable substrates are also present. These variables create a very complex system and meaningful conclusions are indeed difficult to obtain. Studies done around unurbanized emissions sources have the potential of yielding more information, but studies of this type are few. Skye (1958) and Rao and LeBlanc (1967) have shown that lichens decrease around isolated factories that emit primarily SO,. In a recent study, Nash (1972) found that species diversity is markedly reduced near an isolated zinc factory where both SO2 and zinc are released. With the growing interest in air quality and the use of lichens as natural indicators, more studies in areas without city effects are in order. This study was conducted in an unurbanized area around a coal-fired power gener- ating plant. Muskingum Plant is located adjacent to the Muskingum River, above the town of Beverly, in southeastern Ohio (Fig. 1). The nearest city is Marietta, Ohio, 17

Lichens as Indicators of Air Quality around a Coal-Fired Power Generating Plant'

Several common lichens and their isolated symbionts exhibited abnormal photosynthetic and respiratory rates after exposure to sulfur dioxide. Chlorophyll damage was not present in exposed phycobionts. Physiological evidence partially explains the great differences in lichen sensitivity which have been documented in urban areas. Air pollution has eliminated or excluded most lichens from large cities, a phenomenon that has been documented by many floristic mapping studies (DeSloover & LeBlanc, 1968; Gilbert, 1965; Laundon, 1967; LeBlanc & DeSloover, 1970; Skye, 1968; Skye & Hallberg, 1969). These researchers agree that lichen distributions correlate with sulfur dioxide concentrations in the air. However, some workers feel the depauperate lichen floras of urban areas are the result of city-induced drought rather than atmospheric pollution (Rydzak & Krysiak, 1970). Drought conditions indeed may occur; however, studies done at an isolated source of pollution, an iron-sintering plant without urbanization, show that SO2 is a major determining factor of lichen distribution (Rao & LeBlanc, 1967). Very little research has been done with the physiological effects of SO2 on lichens. In one study, Pearson and Skye (1965) exposed thalli of Parmelia sulcata to SO2 and found decreased net photosynthetic rates in the exposed thalli. The SO2 concentrations used, however, were so unrealistically great (100-100,000 ppm) that their results are of little interpretive value. Rao and LeBlanc (1965) exposed thalli of several common lichens to 5 ppm SO2 at various humidity conditions. Subsequent analysis showed that algal chlorophyll a had been degraded to phaeophytin a and that this breakdown was greatest at the higher humidity conditions. Plasmolysis, and brown spots on the chloroplasts of exposed phycobiont cells, were also observed. Rao and LeBlanc concluded that SO2 combines with water and acts in the form of sulfurous acid and the sulfate ion, degrading algal chlorophyll and plasmolyzing algal cells, thus disrupting the delicate symbiotic balance between phycobiont and mycobiont. The idea that the phycobiont is the more vulnerable partner is reasonable since it has been shown that most of the water in a nonsaturated lichen thallus is held in the algal layer (Showman & Rudolph, 1972). I thank Dr. Emanuel D. Rudolph for his continuing assistance with this research, and the Committee of Institutional Cooperation, Biometeorology Graduate Program, Ohio State University, for financial aid during this study. 2 Present address: 312 S. Locust St., McArthur, Ohio 45651. This content downloaded from 157.55.39.6 on Mon, 19 Sep 2016 05:54:02 UTC All use subject to http://about.jstor.org/terms 336 THE BRYOLOGIST [Volume 75 This brief literature survey indicates that many questions concerning the effects of SO2 on lichens are still unanswered. My research was designed to quantify and study the residual effects of SO2 on the net photosynthetic and respiratory rates of lichen thalli and cultured lichen symbionts. Test organisms were exposed to 2, 4, and 6 ppm SO2 in air to determine the effects on each organism at different SO2 concentrations. Some test materials were also exposed to SO2 in aqueous solution. Chlorophylls a and b of exposed phycobionts were assayed to detect chlorophyll damage. MATERIALS AND METHODS Plant Materials.-The lichens used in this study were: Cladonia cristatella Tuck., Caloplaca holocarpa (Hoffm.) Wade, and Lecanora dispersa (Pers.) Somm. Nomenclature is in accord with Hale and Culberson (1970). Cladonia cristatella was collected from the Scioto Trail State Forest, Ross County, Ohio. Only podetia were collected, and these were stored at 11-190C in a lighted growth cabinet until used. Podetia kept longer than two weeks were not used for physiological studies. Caloplaca holocarpa and L. dispersa were collected from a limestone wall on the campus of Ohio State University, Columbus. Thalli of C. holocarpa were collected just before use, and care was taken to remove all substrate particles. The very small size of L. dispersa prohibited the use of whole thalli for physiological experiments. Voucher specimens of the lichens used in this study are deposited in the Ohio State University lichen herbarium. Symbionts of the above lichens were isolated and cultured axenically by the techniques of Ahmadjian (1967). Each symbiont was given what was thought to be optimum growth conditions. Mycobionts were grown on malt extract-yeast extract medium and kept in the laboratory where the temperature was 24 ? 20C. Phycobionts were grown on Trebouxia Organic Nutrient Medium I (Ahmadjian, 1967) and kept in a growth chamber where the daily temperature in the culture tubes cycled from 11-190C. Paper was placed around the storage baskets so that cultures received no direct light. Exposure to SOE.-Fumigation with 2 and 4 ppm SO2 was done in plastic chambers (7000 ml volume). The control chamber was fumigated with dry, SO-free air. Compressed (laboratory line) air was scrubbed through a 4% sodium bicarbonate solution, passed through a water trap, then dried with Drierite (anhydrous CaSO4) and passed through activated charcoal. The test chamber was fumigated with either 2 ppm SO2 in dry air from a tank prepared by Baker Chemical Co., or with 4 ppm SO2 in dry air prepared by diluting a 50 ppm SO2 mixture. Dilution of the 50 ppm mixture was accomplished with two Brooks flowmeters and a mixing chamber. The fumigation mixtures were checked with an Erickson SO2 analyzer and found to be within 10% of the desired concentration. Fumigation of both test and control chambers was done in the laboratory at 24 ? 1?C. Light intensity during fumigation was well below the compensation points of the organisms studied; exposure time was 24 hr. at a flow rate of 200 ml min.-' Six ppm SO2 exposure was done in a controlled environment room in conjunction with a study on human tolerance by the Ohio State University Department of Preventive Medicine. Temperature was 21?C, relative humidity was 50%, light was again below the compensation point, and exposure time was 24 hr. Sulfur dioxide concentration was periodically monitored and maintained at 6 ppm. For exposure to gaseous SO2, symbiont cultures were removed from culture tubes but left on the agar cylinders. Sixor seven-week cultures of the phycobionts were used and six-month cultures of the mycobionts were used. Whole lichens were placed in petri dishes lined with moist filter paper. Aqueous SO2 solutions were prepared by diluting concentrated sulfurous acid (7.0%). Control plants were submerged in distilled water and test plants were submerged in a 138 ppm sulfurous acid solution (= 1 ppm SO2 in air; Saunders, 1970). Exposure time was 24 hr. at 24?C and minimal light. Respirometry.-Respiratory and net photosynthetic rates of the same plants were measured in a 1.3% (v/v) CO2 atmosphere by differential respirometry. The instrument consisted of all-glass volumometers placed in a Gilson Differential Respirometer unit. Changes in O_ volume were measured while CO, was held constant with Pardee buffer (Umbreit et al., 1964). All measurements were done 24 hr. after termination of SO2 exposure. Changes in 02 This content downloaded from 157.55.39.6 on Mon, 19 Sep 2016 05:54:02 UTC All use subject to http://about.jstor.org/terms 1972] SHOWMAN: EFFECTS OF SO2 ON LICHENS 337 TABLE 1. Mean dark respiratory rates of lichen mycobionts exposed to 2 and 4 ppm SO2 in air and 138 ppm SO, in solution. Rates were measured at 200C, 1.3% CO2; and are expressed as the net microliters of oxygen consumed per milligram dry weight per hour. Numbers are the means of three replicate samples + standard deviations. Mycobiont of Mycobiont of Mycobiont of Treatment Cladonia cristatella Caloplaca holocarpa Lecanora dispersa Control 1.68 + .55 1.91 +_ .10 2.32 + .60 2 ppm SO2 .58 + .06 1.48 + .15 1.74 ? .65 Control .89 ? .19 1.81 ? .50 2.59 + .52 4 ppm SO2 .58 ? .11 1.47 ? .19 1.46 + .27 Control .80 ? .12 1.20 ? .09 138 ppm SO2 .19 + .05 .71 ? .11 volume were determined at 10-minute intervals both in light (6.77 mw cm-2, measured with a Yellow Springs Instruments Model 65 radiometer and a 65-51 sensor-= 0.097 cal./cm2/min., or about 7,500 lux) and in the dark. The light intensity used was photosaturating for all three phycobionts. Temperature of the water bath was 200C. Three replicate samples were studied for each different SO2 exposure. Extraction and Determination of Chlorophyll.-The extraction procedure of Rao and LeBlanc (1965) was used for phycobionts. Chlorophyll a, chlorophyll b, total chlorophyll, and the a/b ratio were determined spectrophotometrically (Arnon, 1949) with a Gilford Model 2000 spectrophotometer.

Residual Effects of Sulfur Dioxide on the Net Photosynthetic and Respiratory Rates of Lichen Thalli and Cultured Lichen Symbionts

Air quality improvement near a coal-fired power plant led to recol- onization of Parmelia caperata (L.) Ach. in a pollution-induced void area. Recol- onization was first observed about four years after pollution abatement. Least- affected sites, i.e. near the edge of the original void, were first to recover while most-affected sites were slowest to recover. After eight years of improved air quality, the distribution of P. caperata has returned to near normal. Lichen bio- monitoring is useful not only to detect the effects of poor air quality but to docu- ment air quality improvement as well. There are numerous reports detailing the depauperate condition of lichens in polluted environments (Ferry et al. 1973). However, reports of lichen recovery following pollution abatement are almost nonexistent. This could be because repeating lichen work in a known area does not have the research appeal of new studies in an unknown area. It might also be because lichen recolonization is a relatively slow process. Henderson-Sellers and Sea- ward (1979) have followed the progress of Lecanora muralis (Schreb.) Rabenh. in an improved environment. They found a lag time of about five years before air quality im- provement was reflected by improved lichen distribution. Changes in fuels and industrial technology to meet strict emission standards have led to decreased air pollution levels in many areas. Information on lichen recolonization is valuable for interpreting lichen studies in those areas where pollution levels have decreased.

Lichen recolonization following air quality improvement

Improvement in the air quality of the upper Ohio River valley has led to lichen recolonization at previously depauperate sites. Between 1973 and 1996 the number of corticolous macrolichen species in the area increased from 6 to 20. During the same time the mean species richness per site increased from 0.8 to 6.5. An indicator species, Flavoparmelia caperata, was absent from all study sites in 1973, but present at 27 of 28 study sites in 1996. Lichen studies performed over time provide a good tool to document air quality improvement, but a single study in a changing air quality environment may give problematic results. There are many published accounts of the detrimental effects of air pollution, especially sulfur dioxide, on lichen species distribution and community success (Ferry et al. 1973; Nash & Wirth 1988). Recently, however, industrial modernization and clean air legislation have led to decreases in sulfur emissions with concomitant decreases in ground-level SO2 concentrations both in North America and Europe. One source (Placet & Streets 1987) estimated that total SO2 emissions in the United States decreased from 26.8 million metric tons in 1975 to 21.2 million metric tons in 1985. There have been further decreases to 16.6 million metric tons in 1995 (USEPA 1996). Ohio has shown similar decreases in emissions with 2.99 million metric tons in 1975, 2.43 in 1985 and 1.90 in 1995. The upper Ohio River valley was once reputed to have the dirtiest air in the nation (Showman 1990). This area was heavily industrialized with coal-burning power plants, steel mills, foundries, and coking ovens. However, the region was severely affected by the economic recession in the late 1970s that led to the decline of the steel industry. Old plants were closed and others were upgraded and modernized. At the same time, clean air legislation led to particulate and gaseous emission controls on most electric power generation and industrial plants. This decrease in emissions had a dramatic effect on the ambient SO2 levels measured at upper Ohio River valley locations. Monitoring data (North Ohio Valley Air Authority, pers. comm.) show that in 1975, Steubenville, Ohio had an annual average SO2 concentration of 118 iggm-3. In 1985, this had almost halved to 60 agm-3, and by 1995 the value was further reduced to 34 agm-3. Likewise, East Liverpool, Ohio reported annual average SO2 concentrations of 120, 44, and 31 agm-3 during the same years. For comparison, the National ambient air quality standard (annual average) for SO2 is 80 Igm-3. Data from the several monitoring sites in the area consistently show a sharp decline from high to much lower values about 1981 (North Ohio Valley Air Authority, pers. comm.). Lichen studies in the upper Ohio River valley were first conducted in 1973 around Cardinal Power Plant, located just south of Steubenville, Ohio (Fig. 1). After the initial study, it was apparent that the regional SO2 background overwhelmed any contribution to ground-level concentrations by the power plant. Lichens were depauperate throughout a 570 km2 study area with no discernible differences between sites upwind and downwind from the Cardinal Plant. Studies were continued in order to monitor the impact of regional SO2 on lichens. Lichen re-surveys were performed in 1983, 1988, and then yearly to the present. Lichen improvement was first seen in 1988 and a note reporting this was published in 1990 (Showman 1990). The purpose of this paper is to describe lichen recolonization up to 1996 in greater detail, and to relate the observed changes in the lichen flora to potential associations with improved air quality over the same timespan.

Continuing lichen recolonization in the Upper Ohio River valley.

Improvement in the air quality of the upper Ohio River valley has led to lichen recolonization at previously depauperate sites. Between 1973 and 1989 the number of lichen species in the area almost doubled and the mean species per site increased from 0.8 to 3.5. An indicator species, Flavoparmelia caperata, was completely absent in 1973 but occurred at half of the study sites in 1989. While many papers have detailed the loss of lichens in poor air quality, only a few have reported the recovery of lichens in improving air quality. Sulfur dioxide air quality is now improving in most areas of the United States. One source (Placet & Streets 1987) estimates that total SO2 emissions in the United States decreased from 26.8 million metric tons in 1975 to 21.2 million metric tons in 1985. Ohio showed a similar decrease in SO2 emissions from 2.99 to 2.43 million metric tons during the same period. The upper Ohio River valley was once reputed to have the dirtiest air in the nation. This area was heavily industrialized with coal-burning power plants, steel mills, foundries, and coking ovens. However, the region was severely affected by the recession of the late 1970's and the concomitant decline of the U.S. steel industry. Old plants were closed and modernization and fuel switching at other facilities led to reduced SO2 emissions. This decrease in emission has had a dramatic effect on the ambient SO2 levels. Data from the North Ohio Valley Air Authority (Robert T. Carducci, pers. comm.) show that in 1975, Steubenville, Ohio had an annual average SO2 concentration of 118 ~g/m3. By 1985 this had almost halved to 60 jig/m3. East Liverpool, Ohio reported an annual average of 120 ig/m3 in 1975 and 44 ig/m3 in 1985. For comparison, the National ambient air quality standard is 80 Ug/m3. Data from several different monitoring sites in the area consistently show a sharp decline from high to much lower values about 1981. Lichen studies in the upper Ohio River valley were first conducted in 1973 around Cardinal Power Plant, located between Wheeling, West Virginia and Steubenville, Ohio. After the initial study, it was apparent that the regional SO2 background overwhelmed any contribution to ground-level SO2 by the power plant. Lichens were depauperate throughout the study area with no apparent differences between sites upwind and downwind from Cardinal Plant. Thus, studies were continued to monitor the impact of regional SO2 on lichens. Lichen resurveys were performed in 1983, 1988, and 1989.

Lichen Recolonization in the Upper Ohio River Valley

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