University, Orlando, Florida ... its range and there has been considerable research on control tech- ... lando, Florida on November 11 and 12, 1969 .
Hydrobiologia, vol . 38, 3--4, pga . 409-414, 1971 .
Variation in the Elemental Content of Eichhornia crassipes* by CLAUDE E . BOYD
Savannah River Ecology Laboratory, Drawer E Aiken, South Carolina
DAVID H . VICKERS
Department of Biological Sciences, Florida Technological University, Orlando, Florida INTRODUCTION
The water hyacinth, Eichhornia crassipes (MART .) SOLMS, is widely distributed in tropical and subtropical regions of the world . This aquatic macrophyte is recognized as a serious pest plant over all of its range and there has been considerable research on control techniques (HOLM, WELDON & BLACKBURN, 1969) . There is an abundance of information on the general ecology and life history of E. crassipes (PENFOUND & EARLE, 1948) . Considerable data on nitrogen content and some information on other inorganic nutrients and organic constituents are available from studies which indicated that this plant may have value as a feedstuff (LITTLE, 1968 ; BOYD, 1969a) . Preliminary appraisal indicates that cultivation and removal of water hyacinth is a promising technique for stripping nutrients from waste effluents or from eutrophic lakes (BOYD, 1970a) . Therefore, additional data on the elemental composition of this plant are needed. Results of elemental analyses of samples of E . crassipes form habitats with different environmental regimes are presented in this report. * This research is supported by Contract AT (38-1)-310 between the University of Georgia and the U . S . Atomic Energy Commission . Received Jan . 16 1971 . 40 9
MATERIALS AND METHODS
Plants were collected from 17 sites within a 80 km radius of Orlando, Florida on November 11 and 12, 1969 . Sites represented an extremely wide range of habitat variations, including lakes, small ponds, drainage ditches, and natural streams . Several of these sites were known to receive significant amounts of nutrient pollution, while others were suspected to be unpolluted natural waters . Four to eight lush green plants were selected from each site and placed on ice until processed 24 to 72 hr later . Water samples from each site were analyzed for total alkalinity and dissolved phosphorus (American Public Health Association, 1963) . Macronutrient cations were determined by atomic absorption spectrophotometry . Plants were carefully washed in tap water, picked free of debris, and dried at 60°C in a forced-draft oven . Samples were pulverized with a Wiley mill, redried, and desiccated . Nitrogen was determined by the micro-Kjeldahl technique (Association Official Agricultural Chemist, 1960) . Sulfur was measured by the method of SANFORD & LANCASTER (1962) . Concentrations of other elements were determined with a jarrell-Ash direct reading 1 .5 m emission spectrograph (Model Series 6600) . RESULTS AND DISCUSSION
Data for mineral composition of the dried E . crassipes samples are presented in Table I . As evident by the wide standard errors and large coefficients of variation (usually above 30%), elemental concentrations of samples from different sites varied greatly . When individual elements are considered, samples with maximum concentrations were often several times higher than specimens with minimum levels . Frequency distributions of the values for all elements followed a fairly normal distribution . This was to be expected since the plants were collected from a diversity of habitats . The ranges of elemental concentrations in Table I are probably a good estimate of the ranges of values that can be expected in most water hyacinth populations. Within site variation in the elemental composition of E . crassipes was not determined . However, based on findings for Justicia americana, Alternanthera philoxeroides, Typha latifolia, Scirpus americanus, and Juncus effusus (BOYD, 1969b, 1970b, 1971), within site variation in elemental concentrations of plants is much smaller than between site variation for all elements . Elemental values for water hyacinth fall within the range of values reported for native terrestrial species (GERLOFF, MOORE & CURTIS, 41 0
TABLE I
The elemental composition of samples of Eichhornia crassipes .from 17 different habitats . Element Min . Average ,t std . error
Max,
Coefficient of variation (%)
% Dry wt . basis Nitrogen
1 .33
2 .39 + 0 .13
3 .33
22 .68
Phosphorus
0 .14
0 .54 + 0 .05
0 .80
38 .30
Sulfur
0 .37
0 .48 + 0 .02
0 .63
13 . 76
Calcium
0 .66
1 .35 + 0 .12
2 .10
37 .95
Magnesium
0 .20
0 .55 + 0 .04
0 .88
31 .35
Potassium
1 .60
4 .45 + 0 .34
6 .70
31 .98
Sodium
0 .17
0 .41 ± 0 .05
0 .75
49 .79
pp. Dry wt basis 522
3420 + 824
14,440
99 .22
Manganese
87
270 ± 25
400
38 .47
Zinc
25
67 +
11
209
68 .39
7
15 +
5
100
144 .19
15
20 +
1
25
19 .22
2
12 +
3
40
89 .47
Iron
Copper Boron Molybdenum
1964) and other aquatic species (STRASKRABA, 1966 ; RIEMER & TOTH, 1968) . No special features in nutrient content were obvious . Results of water analyses from the 17 sites were within the following ranges ; total alkalinity (2 .0 to 201 .1 ppm as CaCo 3), phosphorus (0 .005 to 2 .095 ppm), calcium (1 .9 to 100 .0 ppm), magnesium (1 .03 to 26.81 ppm), potassium (0 .4 to 18 .0 ppm), and sodium (7 .6 to 66 .6 ppm) . This illustrates that E . crassipes occurs over a wide spectrum of water quality . All correlation coefficients between environmental and tissue levels of the above macronutrients were nonsignificant . However, those samples with higher levels of phosphorus and potassium were usually from sites with high concentrations of these nutrients . Conversely, samples having smaller amounts of potassium and phosphorus were from waters low in these elements . This relationship between water and tissue concentrations did not hold for plants of intermediate phosphorus and potassium content . The lack of significant correlations between water and water hyacinth nutrient levels may be related to several factors . In small closed systems with comparatively small water volumes relative to plant biomass, nutrient supplies in the water were possibly largely depleted prior to the time of sampling . In large deep lakes, it is less likely that nutrient levels would be appreciably lowered by plant uptake due to the greater water volume-plant biomass ratio . Observed dissolved nutrient levels in flowing systems do not necessarily 41 1
reflect prior nutrient concentrations . This is also true for lakes, but variations in dissolved nutrient levels should be greater in streams due to fluctuations in flow rates . The situation in streams is further complicated in that the plants are exposed to a much greater volume of water (due to flow) from which to extract nutrients, as compared to plants in lakes . Furthermore, above a certain point, increases in external concentrations of a particular nutrient fail to cause increased uptake of the nutrient by the plant (MILLAR, 1955) . Ratios of nutrients in waters of the different sites did not differ in the same proportions between sites . The uptake of many elements are influenced by environmental concentrations of other elements (WALLACE, 1966) . Due to the multiplicity of factors influencing the uptake of a particular nutrient, it is not surprising that we failed to find significant linear correlations between concentrations of macronutrients in the water and in water hyacinth biomass . E. crassipes produces relatively large standing crops . PENFOUND & EARLE (1948) reported a standing crop of 1 .5 kg/m 2. DYMOND (1949) and SAHAI & SINHA (1969) reported standing crops of 1 .4 and 0.72 kg/m2, respectively . Standing crops are expected to vary greatly from one site to another as in other species of macrophytes (BOYD & HESS, 1970 ; BOYD, 1969b), but water hyacinth appears to be a fairly productive species. Large water hyacinth populations such as found in many tropical and subtropical areas (HOLM, WELDON & BLACKBURN, 1969) remove large quantities of nutrients from the water and are dominant factors in biogeochemical cycles . Using a conservative estimate of 1,276 g dry wt/m 2 (PENFOUND, 1956) for the standing crop of E . crassipes and minimum and maximum elemental concentrations from Table I, from 17 .0 to 42 .5 g/m2 of nitrogen, 1 .8 to 10 .2 g/m 2 of phosphorus, and 20 .4 to 85 .5 g/m2 of potassium would be bound in hyacinth biomass . From the standpoint of pollution abatement, continual harvests of these plants from lakes would represent considerable nutrient removal (BOYD, 1970a ; YOUNT & CROSSMAN, 1970) . The plants could possibly be dried and then used as a feedstuff . The practicality of such operations should be investigated . The role of these plants in nutrient cycles is important in eradication programs employing herbicides. Once water hyacinth is killed, the nutrients contained in their biomass will rapidly return to the water . Another plant species will utilize the nutrients for growth and an aquatic plant problem may still exist . The aquatic plant problem cannot be considered independently of nutrient pollution in most cases, so plant management techniques must be developed along with pollution abatement programs . 41 2
SUMMARY
The elemental composition of E. crassipes falls within the range of elemental values reported for other aquatic and terrestrial plants . Concentrations of macronutrients in water hyacinth biomass were not correlated with environmental levels of these nutrients . E. crassipes produces large, dense stands and dominates biogeochemical cycles in many aq,Jatic ecosystems . REFERENCES AMERICAN PUBLIC HEALTH ASSOCIATION . - 1963 - Standard methods for the examination of water and waste water . Amer . Publ . Health Assoc., Inc., New York . ASSOCIATION OFFICIAL AGRICULTURAL CHEMIST - 1960 - Methods of analysis_ Assoc . Off. Agr . Chem ., Washington, D . C . BOYD, C . E. - 1969a - The nutritive value of three species of water weeds . Econ . Bot ., 23 : 123-127 . BOYD, C . E . - 1969b - Production, mineral nutrient absorption, and biochemical assimilation by Justicia americana and Alternanthera philoxeroides . Arch . Hydrobiol., 62 : 139-160 . BOYD, C. E . - 1970a - Vascular aquatic plants for mineral nutrient removal from polluted waters . Econ . Bot ., 24 : 95-103 . BOYD, C . E . - 1970b - Production, mineral accumulation and pigment concentrations in Typha latifolia and Scirpus americanus. Ecology, 51 : 285-290 . BOYD, C . E . - 1971 - The dynamics of dry matter and chemical substances in a ,funcus effusus population . Amer . Midi . Nat ., 86 (In Press) . BOYD, C . E . & HESS, L. W . - 1970 - Factors influencing shoot production and mineral nutrient levels in Typha latifolia . Ecology, 51 : 296-300 . DYMOND, G . C . - 1949 - The water-hyacinth, a cinderella of the plant world . p . 221-227 . In : VAN VUREN, Soil fertility and sewage . London . GERLOFF, G . C., MOORE, D . D ., & CURTIS, J . T . - 1964 - Mineral content of native plants of Wisconsin . Agri . Expt . Sta ., Univ . Wise ., Madison, Research Report 14 . HOLM, L . G ., WELDON, L . W., & BLACKBURN, R . D . - 1969 - Aquatic weeds . Science N. T., 166 : 699-709 . LITTLE, E . C . S. - 1968 - Handbook of utilization of aquatic plants . Food and Agri . Org . United Nations, Rome . MILLAR, C . E . - 1955 - Soil fertility . John Wiley, New York . PENFOUND, W . T . - 1956 - Primary productivity of vascular aquatic plants . Lim-nol . Oceanogr., 1 : 92-101 . PENFOUND, W . T . & EARLE, T. T . - 1948 - The biology of the hyacinth . Ecol . Monogr ., 18 : 448-472 . SANFORD, J . O . & LANCASTER, J . D . - 1962 - Biological and chemical evaluation of the readily available sulfur status of Mississippi soils . Soil Sci. Soc . Amer . Proc ., 26 : 63-65 . SAHAI . R . & SINHA, A . B . - 1969 - Contribution to the ecology of Indian aquatics . I . Seasonal changes in biomass of water hyacinth (Eichhornia crassipes (MART.) SOLMS . Hydrobiol., 35 : 376-382 . STRASKRABA, M . - 1966 - Das Anteil der hoheren Pflanzen an der Produktion der Gewasser . Mith . int. Ver. Theor. angew. Limno l ., 14, Stoffhaushalt der Binnengewasser : Chemie and Mikrobiologie .
41 3
RIEMER, D . N . & TOTH, S . J . - 1968 - A survey of chemical composition of aquatic plants in New Jersey. New Jersey Agri . Expt . Sta . Bull., 820 . WALLACE, A . - 1966 - Current topics in plant nutrition. Edward Bros . Ann
Arbor, Michigan . YOUNT, J . T. & CROSSMAN, R . A . JR . - 1970 - Eutrophication control by plant harvesting . J . Water Poll. Cont. Fed., 42 : 173-183 .
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