P ART II Lead in a Cypress-Gum Swamp, Jackson County, Florida Part II has four chapters summarizing the studies of a lead-filled swamp in Florida. Chapter 5 contains the ecological studies by Lowell Pritchard, Jr. Chapter 6 contains the chemical studies by Shanshin Ton and Joseph J. Delfino. Chapter 7 has the studies of leaded wetland microcosms by Shanshin Ton. Finally, Chapter 8 reports the computer simulation of a model of lead in the wetland by Shanshin Ton and Howard T. Odum. L1401-frame-P2 Page 69 Monday, April 10, 2000 9:32 AM © 2000 by CRC Press LLC 71 CHAPTER 5 Ecological Assessment of the Steele City Swamps* Lowell Pritchard, Jr. CONTENTS Toxicity Assessment with Planted Tree Seedlings 72 Basal Area of Tree Trunks 72 Green Leaf Area 72 Productivity of Emergent Plants 75 Metabolism of the Underwater Ecosystem 75 Invertebrate Animals 77 Indices of Biodiversity 79 Overview Conclusion 79 At the time of this study the Steele City Swamps showed varying degrees of impact, caused less by the large quantities of lead that was filtered than by the high acidity of the battery plant water. Figure 5.1 shows the distribution of lead in sediments, with larger values upstream and along the pathway of water flow. At Station A (Figure 5.2) there were a few dead trees, and the wood (in cross section) was strangely red colored. Much of the pond at B was devoid of trees but covered in part with floating plants ( Nymphaea ). The waters were turbid with underwater objects visible only a few inches below the surface. Gum trees were scattered at Stations C and F, but these had just a few leaves each. In backwater areas (Stations D and H) more trees were found including cypress. In other words, trees were absent in the areas where the most lead had been absorbed (Figure 5.2). Station RF (reference forest) was in a pond which had not received lead wastes and had a normal concentration of cypress and swamp black gum trees. A limited ecological assessment was made by testing seedling survival and growth in the field, by measuring the area of green leaves, by estimating plant productivity with two methods, and by sampling enough underwater invertebrates to calculate indices of biodiversity. Details on the methods are given in Appendix A5 A . * Condensed by the Editor. L1401-frame-C5 Page 71 Monday, April 10, 2000 9:36 AM © 2000 by CRC Press LLC 72 HEAVY METALS IN THE ENVIRONMENT: USING WETLANDS FOR THEIR REMOVAL TOXICITY ASSESSMENT WITH PLANTED TREE SEEDLINGS Tree seedlings (pond cypress, bald cypress, and swamp black gum) were planted where bare bottoms had become exposed, measured September 24, 1990 and monitored again June 6, 1991. In the interim there were very high water levels because of heavy rains. Since wetland tree seedlings die if covered with water, mortality was large (Table 5.1). Surviving seedlings showed growths 10 to 30 cm. Growth and survival at station F may indicate that the sediments, although still containing lead (Chapter 6), were not toxic to new seedlings. BASAL AREA OF TREE TRUNKS By measuring the diameter of live trees, the area of the trunk cross sections may be calculated, which is called the forest basal area. Table 5.2 shows zero values in the upper stations without trees, increasing downstream to 57 cm 2 /m 2 of land, a bit less than that in the reference forest. GREEN LEAF AREA In a normal wetland forest there are several layers of leaves on top of each other. The area of leaves per area of ground below is called the leaf area index. Leaf area of the sparse tree areas was Figure 5.1 Sediment lead concentrations in Steele City Bay, in hundreds of parts per million sediment by weight. Isoconcentration lines were calculated with data from Mundrink (1989). 5 100 50 10 15 100 meters 2 5 2 5 10 1 1 5 1 1 1 + + + L1401-frame-C5 Page 72 Monday, April 10, 2000 9:36 AM © 2000 by CRC Press LLC ECOLOGICAL ASSESSMENT OF THE STEELE CITY SWAMPS 73 Figure 5.2 Site map of Sapp Battery, Steele City Bay, and other downstream wetlands. Locations of samples and measurements are shown. Overall drainage pattern in this area is from northwest to southeast. Table 5.1 Tree Seedling Survival Location Species Number Planted Number Surviving Average Growth of Survivors (cm) F TAAS 21 10 20 TADI 21 12 10 NYSY 21 5 29 G TAAS 20 0 — TADI 20 0 — NYSY 20 0 — H TAAS 14 0 — TADI 13 13 29 Reference forest TAAS 20 0 — TADI 20 19 10 NYSY 20 0 — Note: TAAS = Taxodium ascendens ; TADI = T. distichum ; NYSY = Nyssa sylvatica var. biflora. SAPP BATTERY SITE West Swamp East Swamp RF US 231 A B C D E F G H RP Steele City Bay N 0 500 1000 (Feet) L1401-frame-C5 Page 73 Monday, April 10, 2000 9:36 AM © 2000 by CRC Press LLC 74 HEAVY METALS IN THE ENVIRONMENT: USING WETLANDS FOR THEIR REMOVAL measured by the annual litterfall into baskets set above the water (Table 5.2). In a fully developed forest there may be 4 to 7 m 2 of leaves per square meter of ground, but much less (0 to 2.9) in the impacted wetland with few healthy trees remaining (Table 5.2). The index was about 3 in the reference wetland without lead (Figure 5.3, Table 5.3). Floating lilies ( Nymphaea odorata ) were present at Stations B, C, D, F, and G and the index on July 7, 1991 ranged from 0.70 to 1.25 (Table 5.2). A statistical analysis of variance comparing values from the different stations did not find any difference between stations that was greater than the general variation among data samples. Table 5.2 Summary Statistics for Water Lilies and Trees Location Water Lilies LAI (mean ± S.D.) Trees Basal Area (cm 2 /m 2 ) Trees LAI (mean ± S.D.) Trees Leaf Area/Basal Area (m 2 /m 2 ) A 0.0 ± 0.0 0.0 0.00 ± 0.000 — B 1.2 ± 0.3 0.0 0.00 ± 0.000 — C 1.3 ± 0.5 0.0 0.00 ± 0.000 — D 1.1 ± 0.1 0.0 0.00 ± 0.000 — F 1.1 ± 0.2 10.1 0.04 ± 0.007 42 G 1.1 ± 0.3 26.8 0.25 ± 0.004 95 H 0.0 ± 0.0 57.0 2.10 ± 1.527 368 RefFor 0.0 ± 0.0 77.9 2.85 ± 1.807 366 RefPond 0.7 ± 0.2 0.0 0.00 ± 0.000 — Note: LAI = leaf area index; RefFor = reference forest; RefPond = reference pond; S.D. = standard deviation. Figure 5.3 Leaf area indices of trees using several estimation methods. Table 5.3 Litterfall Trap Data and Calculations Location Mean ± S.E. Litterfall (g/m 2 ) Fraction Canopied Corrected Litterfall (g/m 2 ) Leaf Area/Mass Ratio (m 2 /g) Corrected LAI (m 2 /m 2 ) F 90.3 ± 23.9 0.079 7.2 0.00985 0.068 G 288.6 ± 93.0 0.139 40.1 0.00985 0.378 H 355.5 ± 29.6 0.800 284.4 0.00985 2.682 RefFor 348.2 ± 67.0 1.000 348.2 0.00985 3.284 Note: S.E. = standard error of the mean; LAI = leaf area index; RefFor = reference forest. 0 1 2 3 Location Leaf Area Index, m 2 /m 2 Litterfall Visual Bow and Arrow F G H RefFor Method: L1401-frame-C5 Page 74 Monday, April 10, 2000 9:36 AM © 2000 by CRC Press LLC ECOLOGICAL ASSESSMENT OF THE STEELE CITY SWAMPS 75 PRODUCTIVITY OF EMERGENT PLANTS Since cypress and black gum drop their leaves in winter, and water lilies in this area die back in winter, the leaf area at the end of summer is a measure of a year’s leaf production. However, the total organic matter made by plant photosynthesis (gross production) is much greater than this estimate of net storage in the leaves, since much of the organic matter that was made during the year went to support necessary respiration of leaves, limbs, trunks, roots, and insects. The ratio of gross plant production to net production from studies of similar wetlands was used to estimate gross production (Table 5.4). METABOLISM OF THE UNDERWATER ECOSYSTEM The oxygen generated by the photosynthesis of underwater plants (algae and macrophytes) goes into the water as dissolved oxygen, increasing during hours of sunlight. At night plants, animals, and microbes use this oxygen to operate their normal metabolism, and the dissolved oxygen goes down (community respiration). Oxygen also diffuses into waters from the atmosphere until the molecules going into water equal those diffusing out (equilibrium). If the dissolved oxygen in the water gets higher than the atmosphere’s equilibrium level, it diffuses out. If the dissolved oxygen is less than the equilibrium level, then oxygen diffuses in. Summarizing these processes, the dissolved oxygen is the balance between gross photosynthesis and diffusion in, minus community respiration and diffusion out. By measuring the dissolved oxygen every few hours for 24 h or more and plotting a graph, a curve of dissolved oxygen is usually observed going from a minimum at sunrise after a night of respiration to a maximum near sunset after a day of photosynthesis. With methods given in Appendix A5 A , one may subtract out the diffusion so that respiration can be calculated from the oxygen Table 5.4 Ecosystem Productivity in Sampled Locations Location Gross Primary Productivity (E6 J/m 2 /year) Empower d (E10 sej/m 2 /year)Canopy a Herbaceous b Aquatic c Total A 0 0 7 7 0.9 B 0 34 3 38 5.0 C 0 37 11 48 6.3 D 0 32 16 48 6.3 F 3 33 8 44 5.8 G 16 34 9 59 7.8 H 134 0 0 134 17.6 RefFor 185 0 0 185 24.3 RefPond 0 21 15 35 4.7 Note: RefFor = reference forest; RefPond = reference pond; GPP = gross primary production; LAI = leaf area index. a GPP was calculated for the reference forest using an LAI/GPP regression from data on wetland forests in Brown et al. (1984: p. 317). GPP for trees in other locations is a fraction of reference forest GPP based on the ratios of their LAI. b GPP was calculated for Nymphaea by setting the highest LAI equal to two times a conser- vative estimate of freshwater marsh net primary production (1000 g dry wt/m 2 ; Mitsch and Gosselink 1986: p. 274) and assigning productivities based on the ratios of LAI. c Aquatic GPP is the average of summer and winter values from Table 5.5. GPP in units of grams O 2 m 2 year –1 was multiplied by 3.5 kcal/g O 2 (Cole 1975: p. 179), 4186 J/kcal, and 365.25 d/year. d Using the emergy/hectare calculated for Northwest Florida wetlands in Pritchard (1992, Appendix F), a transformity for gross primary productivity (GPP) of the reference forest was calculated (1317 sej/J). Empower of run-in and rain was divided by the energy flow. This transformity was used to convert the GPP at other locations to emergy. L1401-frame-C5 Page 75 Monday, April 10, 2000 9:36 AM © 2000 by CRC Press LLC 76 HEAVY METALS IN THE ENVIRONMENT: USING WETLANDS FOR THEIR REMOVAL decrease at night. The oxygen increase in daytime is the gross photosynthesis minus the concurrent respiration. You can add the night respiration to the daytime oxygen increase to get an estimate of gross photosynthesis. It helps to plot the hourly changes in dissolved oxygen on a “rate of change” graph after corrections for the diffusion (Figure 5.4). Points above the horizontal line are increases (positive), and points below the line are decreases (negative). The shaded area above the line is net photosyn- thesis, and the shaded area below the line is night respiration. To get the gross photosynthesis, an estimate is made of the daytime respiration using some assumption about the way it varies. In Figure 5.4 the daytime respiration (darkly shaded) is made to increase during the day, based on the idea that the more sugar made by the plant the more respiration there is. See Appendix A5 A for more details. In Figure 5.4 the respiration (below the line) is greater than the daytime net photosynthesis (above the line). In other words, in the course of a day and night, more oxygen is used than is produced. This means that the swamp water remains below equilibrium with the atmosphere most of the time, a condition resulting from the quantities of decomposing organic matter from litterfall stream transport, tree roots, and animals. The results of diurnal curve measurements of oxygen and the resulting calculations of metab- olism are summarized for several stations in Table 5.5 and Figure 5.5. As expected, respiration was consistently higher than underwater photosynthesis; rates were higher in summer, and slightly higher downstream. The gross primary production of the below-water ecosystem and the above-water canopy estimates were combined in Figure 5.6. Because so many trees were missing, the upper stations had lower totals. Figure 5.4 Example graph for calculating aquatic metabolism from the rate of change of dissolved oxygen, in parts per million per hour. 0 4 8 12 16 20 24 Time, Hours Oxygen Rate of Change, ppm/hour 0.6 0.4 0.2 0 -0.2 -0.4 -0.6 Sunrise Sunset Observed Corrected for Diffusion Net Photosynthesis 24 hour Respiration Gross Photosynthesis L1401-frame-C5 Page 76 Monday, April 10, 2000 9:36 AM © 2000 by CRC Press LLC ECOLOGICAL ASSESSMENT OF THE STEELE CITY SWAMPS 77 INVERTEBRATE ANIMALS With procedures detailed in Appendix A5 A , small animals, mostly aquatic insects, were sampled with a cylindrical collector from underwater and the taxonomic family identified. (Lists of types, dates, and stations are in Appendix A5 B , Tables A5 B .2 and A5 B .3.) The numbers of animals per square meter (density) increased a little downstream away from the lead source (Figure 5.7, Table 5.6). Table 5.5 Total Aquatic Metabolism for Locations in and around Steele City Bay Volume Basis Area Basis Location Distance to Site (m) Depth (m) P g (g O 2 /m 3 /d) R 24 (g O 2 /m 3 /d) P g (g O 2 /m 2 /d) R 24 (g O 2 /m 2 /d) SWSWSWSWAVGSWAVG A0— 0.6 — 1.2 — 1.7 — 0.6 1.3 — 0.9 2.4 B 40 0.8 0.9 1.2 0.3 3.7 0.8 0.9 0.3 0.6 3.0 0.7 1.9 C 244 0.7 0.9 3.8 1.3 6.1 2.0 2.9 1.1 2.0 4.6 1.7 3.2 F 259 0.4 0.7 3.7 2.8 8.4 4.6 1.3 1.8 1.6 2.9 3.0 3.0 D 387 0.9 1.0 5.5 1.0 6.2 1.4 4.9 1.0 3.0 5.6 1.4 3.5 G 700 0.5 0.7 5.8 0.8 9.7 2.0 2.9 0.6 1.7 4.9 1.4 3.1 RefPond 800 — 0.7 — 1.3 — 1.9 — 0.9 2.7 — 1.3 3.0 Note: P g = gross primary productivity; R 24 = 24-h community respiration; S = summer measurement, August 21, 1990; W = winter measurement, February 1, 1991; AVG = average; g = grams; m = meters; d = days; O 2 = dissolved oxygen. Figure 5.5 Aquatic metabolism on area basis. P g = gross primary production; R 24 = 24-h community respiration. 0.0 1.0 2.0 3.0 4.0 5.0 6.0 0 100 200 300 400 500 600 700 800 900 0.0 1.0 2.0 3.0 4.0 5.0 Distance from discharge, meters SUMMER WINTER R P A B B C C D D F F G G RP g 24 P g R 24 Grams oxygen per square meter per day L1401-frame-C5 Page 77 Monday, April 10, 2000 9:36 AM © 2000 by CRC Press LLC 78 HEAVY METALS IN THE ENVIRONMENT: USING WETLANDS FOR THEIR REMOVAL Figure 5.6 Gross primary productivity for each sample location estimated from diurnal oxygen curves, litterfall, and/or leaf area indices. Figure 5.7 Indices of macroinvertebrate community structure for sample locations: (a) density, (b) family rich- ness, (c) Shannon diversity. Sample dates: 08/21/90 ( ⅷ ) and 02/03/91 ( ⅜ ). AB CDFG HRFRP 0.0 5.0 10.0 15.0 20.0 Location Canopy Herbaceous Aquatic Gross Primary Production x 10 7 J/m 2 /year Location (a) (b) (c) Individuals/Square meter Thousands Families H', Bits/Individual RPBBG A1 A2 C F HRF 12.0 10.0 8.0 6.0 4.0 2.0 0.0 15.0 10.0 5.0 0.0 3.0 2.0 1.0 0.0 L1401-frame-C5 Page 78 Monday, April 10, 2000 9:36 AM © 2000 by CRC Press LLC ECOLOGICAL ASSESSMENT OF THE STEELE CITY SWAMPS 79 INDICES OF BIODIVERSITY Often pollution causes the biodiversity of ecosystems to diminish. There may be large numbers of one species (example: Station A1 in Table 5.6). In this study four indices of diversity were calculated from a series of winter and summer data on invertebrates (Table 5.6). Details on these indices are included in Appendix A5 A : S is the number of kinds (families) represented (richness) H is the “information theory content in bits per individual (Shannon)” D is the Simpson index M the number of species in a set of individuals counted (Margalef) In Figure 5.8 three indices were adjusted to a common scale showing similarity among indices. The lowest diversity values were in areas formerly most stressed with lead-acid (Stations A and F), but for most of the stations the results were highly variable, not consistent indicators of lead content. OVERVIEW CONCLUSION The measurements in this chapter show that, in the absence of a tree canopy, the processes of the aquatic ecosystem are dominant and returning to normal, with restoration little affected by residual lead. A much longer time may be required for restoration of the wetland forest, a delay inherent in the slower turnover time and reseeding of trees. Table 5.6 Diversity Indices for Macroinvertebrates Distance (m) Density (N/m 2 ) Shannon Simpson's Location S N H ′ s 2 D s S 2 M a August 21, 1990 A1 0 5 251 10780 0.42 0.01 0.115 0.001 0.7 A2 0 6 63 2706 1.23 0.04 0.436 0.004 1.2 B 40 12 41 1761 2.87 0.05 0.806 0.003 3.0 C 244 8 38 1632 2.52 0.03 0.801 0.002 1.9 D 259 7 26 1117 2.46 0.04 0.806 0.003 1.8 F 387 5 46 1976 1.36 0.04 0.504 0.005 1.0 G 700 12 31 1331 3.12 0.05 0.871 0.002 3.2 H 500 10 154 6614 1.24 0.02 0.347 0.002 1.8 February 3, 1991 A1 0 1 3 129 0.00 0.00 0.000 0.000 0.0 A2 0 1 2 86 0.00 0.00 0.000 0.000 0.0 B 40 10 77 3307 1.72 0.05 0.511 0.004 2.1 C 244 8 35 1503 1.91 0.07 0.617 0.007 2.0 D 259 9 65 2792 2.08 0.04 0.671 0.003 1.9 F 387 7 72 3092 1.23 0.04 0.414 0.004 1.4 G 700 14 141 6056 1.84 0.03 0.534 0.002 2.6 H 500 11 54 2319 2.73 0.04 0.797 0.002 2.5 RefFor NA 9 11 4767 1.80 0.03 0.558 0.003 1.7 RefPond NA 16 153 6571 2.38 0.02 0.691 0.001 3.0 Notes: Distance is distance from site; S is number of families; N is number of individuals; H ′ is Shannon diversity in bits/individual; D s is Simpson diversity; and M a is Margalef diversity. Reference sites were added for the winter sampling event. L1401-frame-C5 Page 79 Monday, April 10, 2000 9:36 AM © 2000 by CRC Press LLC [...]...L1401-frame-C5 Page 80 Monday, April 10, 2000 9:36 AM 80 HEAVY METALS IN THE ENVIRONMENT: USING WETLANDS FOR THEIR REMOVAL 2 (a) 1 .5 Relative diversity 1 0 .5 NA 0 NA (b) 1 .5 1 0 .5 0 A1 A2 B C D F G H RF RP Location Shannon Simpson Margalef Figure 5. 8 Comparison of normalized macroinvertebrate diversity indices for locations A to H, reference forest (RF), and reference pond . Bay N 0 50 0 1000 (Feet) L1401-frame-C5 Page 73 Monday, April 10, 2000 9:36 AM © 2000 by CRC Press LLC 74 HEAVY METALS IN THE ENVIRONMENT: USING WETLANDS FOR THEIR REMOVAL measured by the annual. the GPP at other locations to emergy. L1401-frame-C5 Page 75 Monday, April 10, 2000 9:36 AM © 2000 by CRC Press LLC 76 HEAVY METALS IN THE ENVIRONMENT: USING WETLANDS FOR THEIR REMOVAL decrease. L1401-frame-C5 Page 79 Monday, April 10, 2000 9:36 AM © 2000 by CRC Press LLC 80 HEAVY METALS IN THE ENVIRONMENT: USING WETLANDS FOR THEIR REMOVAL Figure 5. 8 Comparison of normalized macroinvertebrate