U.S. ENVIRONMENTAL PROTECTION AGENCY NATIONAL EUTROPHICATION SURVEY WORKING PAPER SERIES REPORT ON GREEN LAKE KING COUNTY WASHINGTON EPA REGION X WORKING PAPER No, 868 CORVALLIS ENVIRONMENTAL RESEARCH LABORATORY - CORVALLIS, OREGON and ENVIRONMENTAL MONITORING & SUPPORT LABORATORY - LAS VEGAS, NEVADA ------- REPORT ON KING COUNTY WASHINGTON EPA REGION X WORKING PAPER No, 868 WITH THE COOPERATION OF THE WASHINGTON DEPARTMENT OF ECOLOGY AND THE WASHINGTON NATIONAL GUARD JULY, 1977 ------- REPORT ON GREEN LAKE KING COUNTY, WASHINGTON EPA REGION X by National Eutrophication Survey Water and Land Quality Branch Monitoring Operations Division Environmental Monitoring & Support Laboratory Las Vegas, Nevada and Special Studies Branch Corvallis Environmental Research Laboratory Corvallis, Oregon Working Paper No. 868 OFFICE OF RESEARCH AND DEVELOPMENT U.S. ENVIRONMENTAL PROTECTION AGENCY July 1977 ------- CONTENTS Page Foreword i i List of Washington Study Lakes iv Lake and Drainage Area Map v Sections I. Introduction 1 II. Conclusions 1 III. Lake Characteristics 3 IV. Lake Water Quality Summary 4 V. Literature Reviewed 10 VI. Appendices 11 ------- ii FOREWORD The National Eutrophicatlon Survey was Initiated 1n 1972 1n response to an Administration commitment to Investigate the nation- wide threat of accelerated eutrophlcatlon to freshwater lakes and reservoirs. OBJECTIVES The Survey was designed to develop, In conjunction with state environmental agencies, information on nutrient sources, concen- trations, and impact on selected freshwater lakes as a basis for formulating comprehensive and coordinated national, regional, and state management practices relating to point source discharge reduction and nonpolnt source pollution abatement in lake water- sheds. ANALYTIC APPROACH The mathematical and statistical procedures selected for the Survey's eutrophlcatlon analysis are based on related concepts that: a. A generalized representation or model relating sources, concentrations, and Impacts can be constructed. t b. By applying measurements of relevant parameters associated with lake degradation, the generalized model can be transformed Into an operational representation of a lake, its drainage basin, and related nutrients. c. With such a transformation, an assessment of the potential for eutrophlcatlon control can be made. LAKE ANALYSIS In this report, the first stage of evaluation of lake and watershed data collected from the study lake and its drainage basin is documented. The report 1s formatted to provide state environmental agencies with specific Information for basin planning [§303(e)], water quality criteria/standards review [§303(cj], clean lakes [§314(a,bj], and water quality monitoring [§106 and §305(b)] activities mandated by the Federal Water Pollution Control Act Amendments of 1972. ------- Beyond the single lake analysis, broader based correlations between nutrient concentrations (and loading) and trophic condition are being made to advance the rationale and data base for refine- ment of nutrient water quality criteria for the Nation's freshwater lakes. Likewise, multivariate evaluations for the relationships between land use, nutrient export, and trophic condition, by lake class or use, are being developed to assist in the formulation of planning guidelines and policies by the U.S. Environmental Protection Agency and to augment plans implementation by the states. ACKNOWLEDGMENTS The staff of the National Eutrophication Survey (Office of Research and Development, U.S. Environmental Protection Agency) expresses sincere appreciation to the Washington Department of Ecology for professional involvement, to the Washington National Guard for conducting the tributary sampling phase of the Survey, and to those Washington wastewater treatment plant operators who provided effluent samples and flow data. Ms. Barbara Blau, Lake Restoration Program, and the staff of the Washington Department of Ecology, Lake Restoration Program, provided invaluable lake documentation and counsel during the Survey, reviewed the preliminary reports and provided critiques most useful in the preparation of this Working Paper Series. Major General Howard S. McGee, Adjutant General of Washington, and Project Officer Colonel Clinton C. Johnson, who directed the volunteer efforts of the Washington National Guardsmen, are also gratefully acknowledged for their assistance to the Survey. ------- iv LAKE NAME NATIONAL EUTROPHICATION SURVEY STUDY LAKES STATE OF WASHINGTON American Lake Banks Lake Chelan Lake Diamond Lake Green Lake Keechelus Lake Mayfield Lake Medical Lake Moses Lake Ozette Lake Sammamish Lake Lake Whatcom Lower Granite Reservoir COUNTY Pierce Grant, Douglas Chelan Pend Oreille King Kittitas Lewis Spokane Grant Clallam Ki ng Whatcom Garfield, Whatcom ------- GREEN LAKE Woodland Park X Lake Sampling Site Wash. .—•"• Map Location ------- REPORT ON GREEN LAKE, WASHINGTON STORET NO. 5305 I. INTRODUCTION Green Lake was included in the National Eutrophication Survey (NES) as a water body of special interest to the Washington State Department of Ecology. Tributaries and nutrient sources were not sampled, and this report relates only to lake sampling data. II. CONCLUSIONS A. Trophic Condition:* Survey data indicate that Green Lake is eutrophic, i.e.,. nutrient rich and highly productive. Whether such nutrient enrichment is to be considered beneficial or deleterious is determined by its actual or potential impact upon designated beneficial water uses of each lake. Chlorophyll a_ values in the lake ranged from 0.4 yg/1 in April to 5.5 yg/1 in July, with a mean of 3.0 vig/1. Potential for primary productivity as measured by algal assay control yields was high. Of the 13 Washington lakes sampled in 1975, 3 had higher median total phosphorus values (0.027 mg/1), 10 had higher median inorganic nitrogen values (0.050 mg/1) and 5 had higher median ortho- phosphorus levels (0.009 mg/1) than Green Lake. *See Appendix C. ------- Survey limnologists reported some emergent and floating macro- phytes during the July sampling, and submerged weeds were noted during October. Ketelle and Uttormark (1971) report that although Green Lake is naturally eutrophic, the addition of low nutrient city water to the lake has resulted in improved water quality and fewer nuisance blue-green algal blooms. B. Rate-Limiting Nutrient: The algal assay results indicate that Green Lake was limited by available phosphorus during the spring (04/01/75) and autumn (10/29/75) samplings. Lake data suggest nitrogen limitation in the spring and summer and phosphorus limitation in the fall. ------- III. LAKE CHARACTERISTICS A. Lake Morphometry:* 2 1. Surface area: 1.04 km . 2. Mean depth: 3.8 meters. 3. Maximum depth: 8.8 meters. 4. Volume: 3.952 x 106 m3. B. Precipitation: 1. Year of sampling: 109.6 cm. 2. Mean annual: 90.6 cm. *0tt, Charles R., I960. ------- IV. LAKE WATER QUALITY SUMMARY Green Lake was sampled three times during the open-water season of 1975 by means of a pontoon-equipped Huey helicopter. Each time, samples for physical and chemical parameters were collected from two stations on the lake and from a number of depths at each station (see map, page v). During each visit, depth-integrated samples were collected from each station for chlorophyll ^analysis and phyto- plankton identification and enumeration. During the first and last visits, 18.9-liter depth-integrated samples were composited for algal assays. Maximum depths sampled were 5.5 meters at Station 01, and 3.4 meters at Station 02. For a more detailed explanation of NES methods, see NES Working Paper No. 175. The results obtained are presented in full in Appendix B and are summarized in III-A for waters at the surface and at the maximum depth for each site. Results of the phytoplankton counts and chlorophyll a_ determinations are included in III-B. Results of the limiting nutrient study are presented in III-C. ------- -/ 1/7", ) •r-rsicAL AND CHEMICAL CHARACTERISTICS ( 7/13/75 ) ( 10/29/75 ) PABA«ETFP TEMOEU4TIJEE: u^.fi Cr,r, n , — 1 . = v n E P T '-i 3 UAXDFPTH-*0 ? DIS?">LVF.O oxYiirf. C'G/! > n.-i.5 M DE&TH 3 WAX .JFPTWto ? CONDUCTIVITY (ijMHOC) O.-l .5 M OEPTH 3 "AX OEPTH"* 7 O.-l .S M OF.PTH 3 MA" DF.PTH»» ? TOTAL ALKALINITY <"G/L> O.-l .^ M Lifi-Tri 3 MAX DEPTH** 2 TOTAL P (MG/L) O.-l .S M DEPTH 3 *A* OF.°TH»* ?. DISSOLVED OwTHO P (wr,/D O.-l.- M DEPTH 3 MAX DFPTH»» ? N02+NO3 ("fi/l ) fl.-l.^ '" TE^TH 3 "A< OFPTH»« 7 AMMONIA (MG/L) O.-l. 5 M DEPTH 3 MA* OF.PTH** ? KJELCAHL f-i (MCi/Ll 0.- 1 .S M nE^TH 3 ••'•AX OFPTrt«» 2 S'*'' = ' *.'-•- 9. A -<.6 '-).4- 9.6 9.S 11.6- 1?." 11. fc, ! 1 .?- 11 -11 1 1 .t 49.- 50. 50. 52.- «-4. 5S. 7.3- 7.6 7.4 7.3- 7.4 7.4 ? 1 . - 2 4 . ? 4 , !«.- 24. ?1 . 0.027-0.050 O.mj ^.033-0.05^. n.f<4^ n. 004-n. 009 0 . n n b o.nos-p.o05 o.oob (>.0?0-0. 03(i y.n?n 0.0?0-0.0?0 !'.r; °U 0. 0^0-0. 05fl 0 . O^U 0.030-0.03'! 0 . 1 3 0 0.500-1.50!) 0.5mj 2.300-0.510 0.40 (i ( -EU-^) '1.0- I . 5 '.1- J.4 o.O- l.S ?.l- 3.4 n.O- 1.5 ?.l- 3.4 0.0- 1.5 2.1- 3.4 " .0- 1.5 2.1- 3.4 0.0- 1.5 ? . ! - 3.4 0.0- 1 .S ? . 1 - 3.4 n.O- 1.5 2.1- 3.4 1.0- 1.5 2.1- 3.4 o.n- i .^ '.1- 3.4 ^AN 3 1 * . 2 - c 1H.3- 3 4.4- 2 rt .H- 3 21 .- 2 20.- 3 7.8- 2 7.7- 3 ??.- ? 22.- 3 O.Ol^-O 2 0.019-0 ? 0.013-0 2 0.014-0 3 0.020-0 2 n. 020-0 3 0.030-0 2 0.020-0 3 0. 3 00-0 2 O.?00-0 s*»» 19.2 IB. 4 9.0 9.0 35. 25. 8.1 7.8 26. 23. .026 .020 .016 .016 .020 .020 .030 .040 .900 .500 = ? MEDIAN 19.2 1*.3 3.8 3.9 33. 23. 8.0 7.8 23. 23. 0.020 0.019 0.016 0.015 0.020 0.020 0.030 0.030 0.600 0.350 MAX OEPTH WANGF; (METE 0.0- 2.1- 0.0- 2.1- 0.0- 2.1- 0.0- 2.1- 0.0- 2.1- 0.0- 2.1- 0.0- 2.1- o.o- 2.1- o.o- 2.1- 0.0- 2.1- HS) 1.5 5.5 1.5 5.5 1.5 5.5 1.5 5.5 1.5 S.5 1.5 5.5 1.5 5.5 1.5 5.5 1.5 5.5 1.5 5.5 N* 3 2 3 2 3 2 3 2 3 2 3 ? 3 2 3 2 3 2 3 2 RANGE 12.2- 12.3 12.2- 12.3 9.8- 10.4 9.8- 9.8 31.- 34. 31.- 32. 7.1- 7.2 7.1- 7.1 19.- 21. 20.- 22. 0.023-0.036 0.028-0.070 0.005-0.010 0.002-0.009 0.060-0.060 0.060-0.060 0.0«0-0.080 0.070-0.090 0.200-0.200 0.200-0.300 = 2 MEDIAN 12.2 12.2 10.0 9.8 32. 32. 7.1 7.1 20. 21. 0.026 0.049 0.006 0.005 0.060 0.060 0.080 0.080 0.200 0.250 MAX DEPTH PANGE (METEPS) 0.0- 2.1- 0.0- 2.1- 0.0- 2.1- 0.0- 2.1- 0.0- 2.1- 0.0- 2.1- 0.0- 2.1- 0.0- 2.1- 0.0- 2.1- 0.0- 2.1- 1.5 3.4 1.5 3.4 1.5 3.4 1.5 3.4 1.5 3.4 1.5 3.4 1.5 3.4 1.5 3.4 1.5 3.4 1.5 3.4 SeCCHI DI=C 1.?- 2.7- 2.7 2.7 2.4- 2.4 2.4 MAXIMUM Ot-T~: .lA-'^LKO AT EACH s = ,MO. OF StTtS CAMPLED ON THI1^ HATE ------- B. Biological Characteristics: 1. Phytoplankton - Sampling Date 04/01/75 07/18/75 10/29/75 Dominant Genera 1. Asterionella 2. Aphanizomenon 3. Fragilaria 4. Flagellate 5. Centric Diatom Other genera Total 1. 2. 3. 4. 5. Microcystis Oscillatoria Cyclotella Chroomonas Closterium 1. 2. 3. 4. 5. Other genera Total Asterionella Chrysophytan Anabaena Fragilaria Aphanizomenon Other genera Total Algal Units per ml 3,960 2,487 1,301 287 57 192 8,284 341 341 189 114 38 37_ 1,060 676 204 157 157 94 158 1,446 ------- 2. Chlorophyll a_ - Sampling Station Chlorophyll a_ Date Number (yg/1) 04/01/75 01 0.6 02 0.4 07/18/75 01 2.0 02 5.5 10/29/75 01 4.5 02 4.9 ------- C. Limiting Nutrient Study: 1. Autoclaved, filtered, and nutrient spiked a. 04/01/75 Spike (mg/1) Control 0.05 P 0.05 P + 1.0 N 1.00 N b. 10/29/75 Ortho P Cone, (mg/1) 0.009 0.059 0.059 0.009 Spike (mg/1) Control 0.05 P. 0.05 P + 1.0 N 1.00 N Ortho P Cone, (mg/1) 0.010 0.060 0.060 0.010 Inorganic N Cone, (mg/1) 0.044 0.044 1.044 1.044 Inorganic N Cone, (mg/1) 0.140 0.140 1.140 1.140 Maximum yield (mg/1-dry wt.) 0.8 3.6 20.6 0.8 Maximum yield (mg/1-dry wt.) 2.9 6.1 30.5 3.5 ------- 2. Discussion - The control yields of the assay alga, Selenastrum capri- cornutum. indicate that the potential for primary productivity in Green Lake was moderate during spring sampling (04/01/75) and high at the time of autumn sample collection (10/29/75). In both assays, a significant increase in yield over that of the control occurred when phosphorus was added alone and in combination with nitrogen, indicating phosphorus limitation. The addition of nitrogen alone did not produce a significant growth increase beyond that of the control. The mean inorganic nitrogen to orthophosphorus (N/P) ratios in the lake data were approximately 11/1, 3/1, and 24/1 in the spring, summer, and fall, respectively, suggesting primary limitation by nitrogen in the spring and summer, and phosphorus limitation in the fall (a mean N/P ratio of 14/1 or greater generally reflects phosphorus limitation). ------- 10 V. LITERATURE REVIEWED Ketelle, Martha J. and Paul D. Uttormark. 1971. Problem Lakes in the United States. U.S. Environmental Protection Agency Project #16010EHR. University of Wisconsin, Madison, Wisconsin. Ott, Charles R. 1960. A Study of the Environmental Factors Affecting the Eutrophication of Green Lake. MS Thesis, Civil Engineering Department, University of Washington, Seattle, Washington. U.S. Environmental Protection Agency. 1975. National Eutrophi- cation Survey Methods 1973-1976. Working Paper No. 175. National Environmental Research Center, Las Vegas, Nevada, and Pacific Northwest Environmental Research Laboratory, Con/all is, Oregon. ------- 11 VI. APPENDICES APPENDIX A CONVERSION FACTORS ------- CONVERSION FACTORS Hectares x 2.471 = acres Kilometers x 0.6214 = miles Meters x 3.281 = feet Cubic meters x 8.107 x 10 = acre/feet Square kilometers x 0.3861 = square miles Cubic meters/sec x 35.315 = cubic feet/sec Centimeters x 0.3937 = inches Kilograms x 2.205 = pounds Kilograms/square kilometer x 5.711 = Ibs/square mile ------- APPENDIX B PHYSICAL AND CHEMICAL DATA ------- STORE! RETRIEVAL OATF 76/11/16 NATL FUTROPHIC4TIO^ SURVEY EPA-LAS VEGAS 530501 47 45 5?.0 122 20 15.0 3 GREEN LAKE 53033 WASHINGTON 0015 FEET DEPTH CL«SS 00 75/04/01 10 45 10 45 10 45 0011 75/07/18 08 35 0000 08 35 0005 na 35 001« 75/10/29 12 35 0000 12 35 0007 00010 DATE TI»*E OEPT^1 FPOM OF TO DAY FFET CFNT 9.6 9.5 9.4 19.2 19.2 18.4 12.3 12.3 1 1 .6 11.6 1 1.8 9.0 4.4 9.0 9.8 9.8 00300 00077 00094 oo TRANSP CNDUC cECCHI FIELD INCHES MICRO! 108 96 14 VY IHO 49 50 64 35 33 25 32 32 00400 PM su 7.60 7.40 7.35 8.10 R.OO 7.70 7.20 7.15 00410 T ALK CAC03 M&/L 24 24 24 23 22 22 19 20 00610 NH3-N TOTAL MG/L 0.030 0.050 0.030 0.030 0.030 0.040 0.080 0.090 00^25 TOT KJEL N MG/L 0.500 0.500 0.500 0.600 0.300 0.200 0.200 0.200 006TO N02&N03 N-TOTAL MG/l 0.020K 0.030 0.020K 0.020K 0.020K 0.020K 0.060 0.060 00671 PHOS-OIS O«TMO MG/L P 0.005 0.009 0.005 0.016J 0.016J 0.014J 0.005 0.002 DATE TIME DEPTi-' FRO" OF TO DAY FF.ET 75/04/01 10 45 0000 10 45 0005 10 45 0011 75/07/18 08 35 0000 08 35 000^ PR 35 001P 75/10/29 12 35 0000 12 35 0007 0665 S-TOT /L P 0.027 0.050 0.056 0.019 0.0?0 0.019 0.023 0.028 32217 CHLRPHYL A DG/L 0.6 2.0 4.5 00031 INCDT LT REMNING PERCENT K VALUE KNOWN TO BE LESS THAN INDICATED J VALUE KNOWN TO BE ESTIMATED ------- STORET ^RETRIEVAL D«TE NATL FUTROPrtlCATION S'IRVEY E.PA-LAS VEGAS DATE FPOK TO 75/04/01 75/07/18 75/10/29 TIME DEPTH OF OAY FEET 11 15 0000 11 15 0007 08 20 0000 06 20 0007 12 15 0000 12 15 0005 12 15 0011 00010 WATEP TFMP CENT 9.6 9.6 18.? 18.3 12.2 12.? 1?.2 530502 47 40 25.0 122 20 29.0 3 GREEN LAKE 53033 WASHINGTON 131191 11EPALES 00300 DO "G/L 12.0 11.2 8.8 «.8 10.0 10.4 9.8 00077 THANSP SECCHI INCHED 54 108 96 00094 CNOUCTVY FIELD MICPOMHO 50 52 21 20 34 31 31 noil 00400 PH su 7.35 7.40 7.80 7.85 7.15 7.10 7.10 211 i FEET OE»TH CLASS 00410 T ALK CAC03 MG/L 21 18 26 23 20 21 22 00610 NH3-N TOTAL MG/L 0.030 0.030 0.030 0.020 0.080 0.080 0.070 1202 On 00625 TOT KJEL N MG/L 0.500 0.300 0.900 0.500 0.200 0.200 0.300 006^0 f>0671 N02&NO3 PHOS-niS N-TOTAL ORTHO MG/L MG/L P 0.020K 0.020K 0.020 0.020K 0.060 0.060 0.060 0.004 0.005 0.013J 0.016J 0.010 0.006 0.009 DATE TO OF DAY 75/04/01 11 15 0000 11 75/07/18 08 20 0000 08 20 0007 75/10/29 12 15 0000 12 15 12 l^ EPTH EET 0000 0007 ooon 0007 ooon 0005 0011 00665 «>HOS~TOT MG/L P 0.033 0.033 0.026 0.020 0.036 0.026 0.070 32217 CHLftPHYL A UG/L 0.4 5.5 4.9 00031 INCDT LT RFMNING PERCENT K VALUE KNOWN TO BE LESS THAN INDICATED J VALUE KNOWN TO BE ESTIMATED ------- APPENDIX C PARAMETRIC RANKINGS OF LAKES SAMPLED BY NES IN 1975 STATE OF WASHINGTON Mean or median values for six of the key parameters evaluated in establishing the trophic conditions of Washington lakes sampled are presented to allow direct comparison of the ranking, by parameter, of each lake relative to the others. Median total phosphorus, median inorganic nitrogen and median dissolved orthophosphorus levels are expressed in mg/1. Chlorophyll a_ values are expressed in yg/1. To maintain consistent rank order with the preceding parameters, the mean Secchi disc depth, in inches, is subtracted from 500. Similarly, minimum dissolved oxygen values are subtracted from 15 to create table entries. ------- LAKE DATA TO BE USED IN RANKINGS LAKE CODE LAKE NAME 5301 AMERICAN LAKE 5302 BANKS LAKE 5303 CHELAN LAKE 5304 DIAMOND LAKE 5305 GREEN LAKE 5306 KEECHELUS LAKE 5307 MAYFIELO LAKE 5308 MEDICAL LAKE 5309 MOSES LAKE 5310 07ETTE LAKE 5311 SAMMAMISH LAKE 5312 WHATCOM LAKE 5313 LOWER GRANITE RESERVOIR MEDIAN TOTAL P 0.027 0.021 0.005 0.014 0.027 0.007 0.014 0.275 0.115 0.010 0.015 0.009 0.033 . MEDIAN INORG N 0.105 0.040 0.070 0.060 0.050 0.040 0.100 0.225 0.150 0.110 0.210 0.320 0.150 500- MEAN SEC 343.000 364.533 111.900 303.667 415.000 280.250 402.000 401.714 463.600 403.333 374.000 288.000 435.500 MEAN CHLORA 4.822 7.373 , 0.905 14.537 2.983 1.400 4.250 16.425 29.060 1.225 7.290 3.422 •4.875 15- MIN DO 15.000 10.800 6.400 14.200 10.600 9.200 10.600 15.000 14.600 7.200 14.600 10.800 7.200 MEDIA DISS ORTH 0.007 0.007 0.003 0.010 0.009 0.00? 0.007 0.166 0.038 0.009 0.006 0.009 0.022 ------- PERCENT OF LAKES WITH HIGHER VALUES (NUMBER OF LAKES WITH HIGHER VALUES) LAKE CODE LAKE NAME 5301 AMERICAN LAKE . 5302 BANKS LAKE 5303 CHELAN LAKE 5304 DIAMOND LAKE 5305 ,GREFN LAKE 5306 KEECHELUS LAKE 5307 MAYFIELD LAKE 5308 MEDICAL LAKE 5309 MOSES LAKE 5310 07ETTE LAKE 5311 SAMMAMISH LAKE 5312 WHATCOM LAKE 5313 LOWER GRANITE RESERVOIR MEDIAN TOTAL P 29 ( 42 < 100 < 6? ( 29 1 92 1 62 1 0 1 8 1 75 I 50 i 83 17 : 3) 5) ; 12) : 7) ! 3) [ 11) ! 7) : 0) [ 1) I 9) ( 6) ( 10) ( 2) MEDIAN INORG N 50 < 100 < 67 1 75 1 83 1 92 1 58 I 8 1 29 I 42 i 17 0 29 : 6) : 12) : 8) I 9) I 10) : ID 1 7) ! 1) ! 3) ( 5) ( 2) ( 0) ( 3) 500- MEAN SEC 67 ( 58 I 100 ( 75 1 17 1 92 1 33 I 42 1 0 1 25 I 50 i 83 8 I 8) ; 7> : 12) : 9) ! 2) [ 11) 1 4) ! 5) I 0) [ 3) ( 6) ( 10) ( 1) MEAN CHLORA 50 ( 25 ( 100 < 17 < 75 ( 83 1 58 1 8 1 0 1 92 I 33 i 67 42 I 6) : 3) : 12) : 2) [ 9) : 10) [ 7) [ 1) I 0) [ 11) t 4) ( 8) ( 5) 15- MIN DO 4 1 46 ( 100 ( 33 ( 62 1 75 1 62 1 4 ( 21 1 87 1 21 i 46 < 87 1 ,0) ; 5) ! 12) ! 4) ! 7) 1 9) t 7) [ 0) E 2) [ 10) t 2) ( 5) ( 10) MEDIAN DISS OPTHO 58 1 71 1 92 1 25 1 46 1 100 I 71 1 0 I 8 I 33 i S3 46 17 : 7) i ft) ! 11) I 3) t 5) t 12) [ -P) ! 0) I 1) t 4) ( 10) ( 5) ( 2) ------- |