NEW: Annual Report - George Mason University

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Fluorescence was determined before and after acidification with 2 drops of 10% HCl. Chlorophyll a was calculated from the following equation which corrects for pheophytin interference: Chlorophyll a (µg/L) = FsRs(Rb-Ra)/(Rs-1) where Fs=concentration per unit fluorescence for pure chlorophyll Rs=fluorescence before acid /fluorescence after acid for pure chlorophyll Rb=fluorescence of sample before acid Ra=fluorescence of sample after acid All chlorophyll analyses were completed within one month of sample collection. To determine radiocarbon uptake, frozen filters were first placed in concentrated HCl fumes for 10 minutes to drive off residual inorganic carbon. Then, each filter was placed in a scintillation vial and scintillation cocktail was added. Vials were counted for 10 minutes each in a Packard Tricarb 2100TR liquid scintillation counter and corrected for efficiency by the external standard ratio method. Photosynthetic rate was determined from the following equation: (DPM)(ALK) (CF)(1.06) Photosynth eticRate(mgC/L/hr) = (DPMwat)(TIME) where DPM= 14 C activity on filter (algae), (DPM/L) ALK=Total alkalinity, (mg/L as CaCO3) CF=conversion factor from total alkalinity to dissolved inorganic carbon (Wetzel and Likens 1991) DPMwat= 14 C activity in incubation water (DPM/L) 1.06=isotopic discrimination factor TIME=incubation time, (hr) All filters were counted within one month of sample collection. Phytoplankton species composition and abundance was determined using the inverted microscope-settling chamber technique (Lund et al. 1958). Ten milliliters of well-mixed algal sample were added to a settling chamber and allowed to stand for several hours. The chamber was then placed on an inverted microscope and random fields were enumerated. At least two hundred cells were identified to species and enumerated on each slide. Counts were converted to number per mL by dividing number counted by the volume counted. Microzooplankton and macrozooplankton samples were rinsed by sieving a well-mixed 7
8 subsample of known volume and resuspending it in tap water. This allowed subsample volume to be adjusted to obtain an appropriate number of organisms for counting and for formalin preservative to be purged to avoid fume inhalation during counting. A one mL subsample was placed in a Sedgewick-Rafter counting cell and whole slides were analyzed until at least 200 animals had been identified and enumerated. A minimum of two slides was examined for each sample. References for identification were: Ward and Whipple (1959), Pennak (1978), and Rutner-Kolisko (1974). Zooplankton counts were converted to number per liter with the following formula: Zooplankton = (N)( V s ) c )( V f ) where N=number of individuals counted Vs=volume of reconstituted sample, (mL) Vc=volume of reconstituted sample counted sample counted, (mL) Vf=volume of water sieved, (L), normally 96 L ( V Ichthyoplankton samples were sieved through a 333 µm sieve to remove formalin and reconstituted in ethanol. Larval fish were picked from the reconstituted sample with the aid of a stereo dissecting microscope. Identification of ichthyoplankton was made to family and further to genus and species where possible. If the number of animals in the sample exceeded several hundred, then the sample was split with a plankton splitter and resulting counts were multiplied by the subsampling factor. The works of Hogue et al. (1976), Jones et al (1978), Lippson and Moran (1974), and Mansueti and Hardy (1967) were used for identification. The number of (N)(10) Ichthyopla nkton = V ichthyoplankton in each sample was expressed as number per 10 m 3 using the following formula: where N=number of ichthyoplankton in the sample V=volume of water filtered, (m 3 ) C. Adult and Juvenile Finfish Fishes were sampled by trawling at Stations 7, 9, and 10 (Figure 1). A try-net bottom trawl with a 15-foot horizontal opening, a 3/4 inch square body mesh and a 1/4 inch square cod end mesh was used. The otter boards were 12 inches by 24 inches. Towing speed was 2-3 miles per hour and tow length was 5 minutes. In general, the trawl was towed across the axis of the cove at Stations 7 and 10 and parallel to the channel at Station 9, but most tows curved up to 90E from the initial heading and many turned enough to head in the opposite direction. The direction of tow should not be crucial. Dates of sampling and weather conditions are found in Table 1.
Page 1 and 2: An Ecological Study of Gunston Cove
Page 3 and 4: ii An Ecological Study of Gunston C
Page 5 and 6: iv were collected on three sample d
Page 7 and 8: vi We recommend that: 1. Long term
Page 9 and 10: 2 INTRODUCTION This section reports
Page 11 and 12: 4 Table 1 Sampling Dates and Weathe
Page 13: 6 immediately with formalin to a co
Page 17 and 18: 10 A. Climate and Hydrological Fact
Page 19 and 20: 12 B. Physico-chemical Parameters:
Page 21 and 22: 14 Dissolved Oxygen (mg/L) 16 14 12
Page 23 and 24: 16 pH, NC Lab 9.5 9.0 8.5 8.0 7.5 7
Page 25 and 26: 18 Secchi Depth (m) 1.2 1.0 0.8 0.6
Page 27 and 28: 20 Ammonia Nitrogen (mg/L) 0.30 0.2
Page 29 and 30: 22 Organic Nitrogen (mg/L) 1.2 1.0
Page 31 and 32: 24 N/P Ratio (by mass) 60 50 40 30
Page 33 and 34: 26 C. Phytoplankton Chlorophyll a,
Page 35 and 36: 28 Figure 32. Phytoplankton Density
Page 37 and 38: 30 The dominant cyanobacteria on a
Page 39 and 40: 32 Total phytoplankton biovolume ca
Page 41 and 42: 34 Melosira Figure 44. Phytoplankto
Page 43 and 44: 36 Bosmina Density by Station (#/L)
Page 45 and 46: 38 Moina Density by Station (#/m 3
Page 47 and 48: 40 Diaptomus Density by Station (#/
Page 49 and 50: 42 E. Ichthoplankton Larval fishes
Page 51 and 52: 44 Clupeid Larvae (#/10m 3 ) 50 40
Page 53 and 54: 46 Table 4 Adult and Juvenile Fish
Page 55 and 56: 48 The abundance of each species in
Page 57 and 58: 50 Average Number of Fish per Trawl
Page 63 and 64: 56 Average Fish per Seine 600 500 4
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58 Macrobenthos (#/m 2 ) 500 400 30
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60 Total phosphorus levels were fai
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62 Table 10 Correlation and Linear
Page 71 and 72:
64 Water Temperature (oC) 35 30 25
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66 Chloride (mg/L) 350 300 250 200
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68 Dissolved Oxygen (% saturation)
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70 Light Attenuation Coefficient (m
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72 Lab pH, GMU 11 10 9 8 7 Station
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74 Total Alkalinity (mg/L CaCO3), G
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76 Biochemical Oxygen Demand (mg/L)
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78 Volatile Suspended Solids (mg/L)
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80 Soluble Reactive Phosphorus (mg/
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82 Un-ionized Ammonia Nitrogen (mg/
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84 Nitrite Nitrogen (mg/L) 0.100 0.
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86 Nitrogen:Phosphorus Ratio 70 60
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88 Chlorophyll a, Surface (ug/L) 10
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90 PBmax (ug C/ug Chl a/hr) 30 25 2
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92 D. Zooplankton Trends: 1990-2003
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94 Brachionus (#/L) 1000.0 100.0 10
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96 Filinia (#/L) 1000.0 100.0 10.0
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98 Polyarthra (#/L) 1000.0 100.0 10
Page 107 and 108:
100 Diaphanosoma (#/m3) 100000.00 1
Page 109 and 110:
102 Chydorid Cladocera (#/m3) 1000.
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104 Copepod Nauplii (#/L) 1000.0 10
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106 Clupeid Larvae (#/10m3) 1000.0
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108 Atherinid Larvae (#/10m3) 10.00
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110 F. Adult and Juvenile Fish Tren
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112 Table 14 Mean catch of adult an
Page 121 and 122:
Page 123 and 124:
Page 125 and 126:
118 Mean Catch Per Trawl 50 40 30 2
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120 Mean Catch Per Trawl 8 6 4 2 Tr
Page 129 and 130:
122 Mean Catch Per Trawl 120 100 80
Page 131 and 132:
124 Mean Catch Per Trawl 16 14 12 1
Page 133 and 134:
126 Seines The mean annual catch pe
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128 Table 19 The number of seines i
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130 Mean Catch Per Seine 300 250 20
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132 Mean Catch Per Seine 250 200 15
Page 141 and 142:
134 G. Benthos Trends Oligochaetes
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136 Amphipods (#/m2) 16 12 8 4 Stat
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138 Corbicula (#/m2) 40 30 20 10 St
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140 Table 21 Summary of Important T
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142 observed through 1995. This has
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144 being filled. A dredged channel
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146 Anadromous Fish Survey Pohick,
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148 sized fishes were seen, an atte
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150 Table 3. Fish eggs and larvae c
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152 Total 7 11 237 13 2 64 119 (2.3
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154 Table 7. Adult anadromous and s
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156 Table 8. Summary of alewife spa
Page 165 and 166:
158 Spawning information on gizzard
Page 167 and 168:
160 The information that pertains t
Page 169 and 170:
162 lower reaches of Pohick Creek i
Page 171 and 172:
164 Table 13. Catches of adult clup
Page 173 and 174:
Appendix A Phytoplankton Species Di
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