Pacific Science (1976), Vol. 30, No.2, p. 197-205 Printed in Great Britain The Correlation of Soil Algae, Airborne Algae, and Fern Spores with Meteorological Conditions on the Island of Hawaii I J OHNNY L. CARSON2 AND R. MALCOLM BROWN, JR.2 ABSTRACT : Correlations of the generic diversity of soil and airborne algae with altitude on the island of Hawaii are noted.Distribution of the soil algae was deter­ mine d by culturing an aqueous soil extract fro m designated altitudes on agarized inorganic growth media. Distribution of airborne algae and fern spores was deter­ mined by investigations of viable particulate impactions on the surface of agarized inorganic growth media identical to that used in culturing the soil samples. Lit tle correlation occurs between the generic dive rsity of the airborne and soil algae at corresponding altitudes, which suggests a cosmopolitan mixing of air­ borne propagules that have been released from different altitudes. However, striking relationships were noted in the quantitative determinations of airborne green and blue-green algae and of fern spore impactions with the varying meteorological conditions of rain, fog-mist, and clear, sunny conditions accompanying the altitude change. uniform and predictable (Jones 1939, Leopold INTRODUCTION and Stidd 1949). Such conditions more readi ly THE H AWAllAN ISLANDS of the Pacific Ocean permit analysis and modelling of dispersal are ideal natural sites for many scientific in­ mechanisms and patterns. The trade winds and quiries, particularly for studies of atmospheric the barriers provided by th e topography of the dispersal both of microorganisms and higher islands con stitute the principle variations in plants (Brown 1965, 1971). The advantages of weather conditions (Doty and Muel ler-Dorn­ the islands for such investiga tions are twofold. bois 1966). These factors at times result in First, the islands lie at least 2000 miles from extreme variations of climate within very short any major land mass, and the prevalent north­ distances. Humidity can vary from 0 to 100 east trade winds carry few viab le disseminules percent within distances of several tens of miles, over the many miles of ocean and into the and temperatures can vary from 90° F at sea islands. The ability of the marine environment level to below zero at the summits of tall to " scrub " particulates from the atmosphere mountains (Carlquist 1970). has been observed and reported (Glynn 1933, Stud ies of atmospheric dispersal of algae Stepanov 1935, May 1958, Davies 1959, Brown have receive d greater acknowledgment in re­ 1971, and personal communication). Viable cent years with concurrent findin gs that air­ airborne microorganisms have been collected borne algae and other airborne microbes are and cultured from air samples over the islands, causal agents in inhalant allergies and other suggesting that release and dispersal of these respiratory disorders (Hatch 1961; McElhenney particulates is largely an activity of each indi­ et al. 1962; McGovern, McElhenney, and vidual island (Brown 1971). Secondly, weather Brown 1965; Bernstein and Safferman 1966, conditions throughout the islands are highly 1970). Extensive studies of airborne fungal and bacterial particulates have been conducte d I This work was supported in part by a grant from (Pady and Gregory 1963, Pathak and Pady the Research Council of the Unive rsity of North 1965, Pady and Kramer 1967). H owever, it has Carolina to the junior auth or. Manuscript accepted 30 been shown that algae may be predominant No vember 1975. members of the aerial flora and that algae are 2 University of North Carolin a, Department of Botany, Chapel Hill , North Carolina 27514. important colonizers of isolated land areas 197 198 PA CIFIC SCIE N CE, Volume 30, Ap ril 1976 FIGURE 1. View of Mauna Loa and a portion of the Mauna Loa transect looking no rthwest at app rox imately 4000 feet above sea level. (Brown 1965) and bodies of water (Mag uire particularly evident along the no rtheastern 1963). Hamakua Coast of th e island. Secondly, hig h Schlichting's studies (1961, 1964, 1969, 1971) mountain masses like Mauna Loa (Figures 1 include the collection of viable airborne algae and 2), being very broad and wide, absorb and protozoa and the correlation of meteoro­ great quantities of heat during the day, form­ logical conditions with th eir dispersal. He noted ing updrafts toward the summit. During the the relationship of the aerial biota with the afternoon, air surrounding th e mountains is movement of air masses, but emphasized a rapidly drawn upward and the moisture it con­ greater correlation of the aerial flora with th e tains can be condensed rapidly. This can result micrometeorological conditions within the air in extensive rainfall on the low er slopes, taper­ mass. ing off to light showers higher up , and clear Hawaii, the " Big Island ," is an excellent site sunny conditions at higher altitudes (Carlquist to investigate the variations among airborne 1970). Finally, the two preceding features may algae with altitude and changing meteorological be influenc ed further by the inve rsion layer, conditions within short geographical distances. which generally occurs from 5000 to 7000 feet. Within a distance of 50 miles is an altitudinal Such conditions result in a predictable varia­ gradient from sea level to 6500 feet as well as tion of the soil algal flora. This, in turn, medi­ meteo rological conditions that may vary from ates the dispersal of biologically significant extensive rain downpours at the lower eleva­ materials with potential reproductive capacity. tions to dry, sunny conditions at the higher It is important that inquiries be made into altitudes. This is due to several features of the the nature of dispersal in various geog raphical meteorological regime of th e island. First, distances under predictable and consistent Hawaii, like the other islands of the chain, is meteorol ogical conditions. The transect des­ influenced by orographic rainfall. This is cribed here is on the order to 50 miles through Tran sect Route .,. ;;:. Boundary Hawaii Vo lcanoes National Park - - -- Mauna Kea 0 13, 7 96' 1000' ~-..... 6500' 2000':/ .....···· Mauna r-;> ';.:. ,5000' . Lo~ 10 6000 .." 4000' : 13,677 / __I"~ "J ..... ·.... 3000, -~ N « , II I, I! I 5 0 5 10 15 M i lE S ISLAND OF HAWAII FIG URE 2. Map of the island of Hawaii showing the transect route. 200 PACI FIC SCIENCE, Volume 30, April 1976 areas of pronounced meteorological changes (Figure 2). A similar scheme has been des­ RESULTS AND DISCU SSIO N cribed by Brown (1963), which was on the Cultures made from soil samples indicated order of 15 miles and which also ran ged that the greatest generic diversity of the soil through zones of marked meteorological algae occurs at an altitude of 4000 ft (Figure 3). changes. Concurrently with these data, Figure 4 indi­ cates that th e generic diversity of airborne algae is also quite high at these altitudes. This MATE RIALS AND METH ODS area may be considered wet upland forest, and During the summer of 1971, a transect was rainfall is sufficient to support a lush growth set up on the island of Hawaii from th e of many plants (Carlquist 1970). The persis­ coastal city of Hilo up to 6500 ft on the tence of the orographic cloud cover at this slopes of Mauna Loa. Soil sampl es were altitude further enhances the effect of the rain, collected aseptically in sterile plastic bags as little evaporation occurs. from the top 1.0 inch of the substrate at Relatively little correlation is apparent be­ 1000-ft-altitude intervals and packaged and tween the generic diversity of the soil algae sent by air to our laboratory at the Uni­ and the airborne algae at the same altitude. The versity of North Carolina. There, 5 g of each greatest coincidence of generic similarity of soil sample were suspended in 30 ml of Bold 's soil and airborne algae occurs at th e 3000-ft Basal Medi a (BBM)(Brown and Bold 1964), level, an area permeated by fog-mist conditions, sonicated mildly, and 0.5 ml of the suspension which may assist in the redeposition of viable was cultured on each of three Petri dishes of particulates on a small scale. It seems apparent, agarized BBM. The cultures were inspected however, that dispersal at other altitudes is for algal generic diversity after bein g incu­ little related to the soil flora at that altitude bated for 1 month on a continuous light cycle and, in fact, that some generic exchange of th e of approximately 7000 lux and 19° C. During air spo ra between altitudes may occur. Such the autumn of 1973, the same transect was an interaltitude exchange of particulates may mad e; sterile Petri dishes of agarized BBM be derived from daytime updrafts and convec­ were exposed at 500-ft-altitude intervals for tion. The released airborne particles may then 1 minute each from an automobile traveling at be washed out or depos ited by other mech­ 35 miles per hour from Hilo to 6500 ft on anisms such as gravitation or turbulent Mauna Loa . The air-sampling transect was deposition. mad e two tim es at different hours of the day An extensi ve downpour occurred at th e under similar meteorological conditions. These lower altitudes (1000- 2000 ft) at the time of the plates were incubated for 1 month on a con­ air-sampling experiments. However, at alti­ tinuous light cycle of approximately 3500 lux tudes of 2500-3000 ft, weather conditions were and 19° C. Determinations of algal generic those of the fog-mist characteristic of this diversity were made as well as quantitative area. At thos e sampling stations 4000-6500 ft colony counts of the different taxa of airborne in altitude, conditions ranged from partly algae and fern spore impactions as a function cloudy with intermittent sunshine to an almost of viable fern gametophytes observed.