RESPONSE OF PHYTOPLANKTON TO WATER QUALITY IN THE CHOWAN RIVER SYSTEM A. M. Witherspoon, Associate Professor Charles Balducci, Graduate Student Oliver C. Boody, Graduate Student Jimmie Overton, Graduate Student Department of Botany North Carolina State University Raleigh, North Carolina 27650 The work upon which this publication is based was supported in part by funds provided by the Office of Water Research and Technology, U. S. Department of the Interior, Washington, D.C., through The University of North Carolina Water Resources Research Institute, as authorized under the Water Research and Devel- opment Act of 1978. Additional support was provided by the Department of Natural Resources and Community Development of the State of North Carolina. Project No. B-091-NC Agreement No. 14-34-0001-6104 April 1979 TABLE OF CONTENTS (continued) Page Phosphorus Chemistry . 99 Alkaline Phosphatase Activity . 100 Phosphate Uptake Rates and Turnover Times . 102 Light . 104 Phytoplankton Growth Rates . 104 Temperature . 110 Die1 Studies . 11 0 PHYTOPLANKTON AND BACTERIA ACTIVITY, 1976-1977 . 113 Procedure . 11 3 Results . 11 3 Physical Factors . 113 Chemical Parameters . 116 Nitrogen . 116 Phosphorus . 116 N:P................................ 120 Carbon.. , . 120 Chloride Ion, Chemical Oxygen Demand, and pH . 120 Phytoplankton ........................... 122 Bacteria . , . 133 DISCUSSION . 135 Dominant Species Importance . 136 AlgalBiomass ............................ 138 Biomonitor Biomass . 139 Phosphate Enrichment . 140 LITERATURE CITED . 143 APPENDICES............................... 145 Appendix A - Biomass at Various Stations Sampled Bimonthly in the Chowan River and Tributaries . 145 Appendix B - Temporal and Spacial Location of Species in the Chowan River System, March 1974-March 1975 . 147 Appendix C - Dominant Species at Tunis, Colerain, and Edenton . 156 Appendix D - Environmental Data, 1975-1976 . 165 Appendix E - Miscellaneous Data - July 1976-April 1977 . 170 1. Algal Occurrence . , . 170 2. Algal Cell Density, Biomass, Cell Carbon, and Species Present. 185 3. Algal Cell Density, Biomass, Cell Carbon, and Species Present by Group . 186 4. Algal Species, Cell Degsity, Biomass, and Cell Carbon by Period, Site, and Season . 190 5. Chemical and Bacterial Data . 203 ACKNOWLEDGMENTS This study was financed in part by the Office of Water Research and Technology's Matching Grants Program through The University of North Caro- lina Water Resources Research Institute. Additional funds were provided by the Department of Natural Resources and Community Development of the State of North Carolina. Several people were associated with the project in various ways. Dr. L. A. Whitford provided expert algal identification and general advice on many species. The 1974-75 samples were collected by Mr. Grover Cook and the sampling crew from the Department of Natural Resources and Community Development, the State of North Carolina. Technical support was given by Ms. Cheryl Dicks, phytoplankton enumeration; Ms. Pat Boody, algal assay; Mr. Roger Pearce, data reduction and computer graphing. Dr. William S. Galler aided with data retrieval and Dr. Don W. Hayne critiqued the regres- sion analysis. Typing and table preparation were done by Mrs. Sarah Miller and Mrs. Sandra Perkins of the Botany Department and by the clerical staff of the Water Resources Research Institute. Several graduate students in the Botany Dcp~rtmentof N. C. State Uni- versity contributed to this report through their graduate studies for the Master's Degree, Botany (phycology): Mr. Charles Balducci, 1975-1976 assay studies on phosphorus uptake kinetics; Mr. Jimmie Overton, 1975-1976 biomoni- tor biomass study; and Mr. Oliver Boody, 1976-77 phytoplankton-bacteria studies. Full reports of these theses will be filed in the D. H. Hill Library at N. C. State University. DISCLAIMER STATEMENT Contents of this publication do not necessarily reflect the views and policies of the Office of Water Research and Technology, U. S. Department of the Interior, nor does mention of trade names or commercial products constitute their endorsement or recommendation for use by the U. S. Government. ABSTRACT An investigation of seasonal changes in phytoplankton species diversity and biomass, phosphorus uptake kinetics, in-situ and in-vitro algal growth potential and phytoplankton-bacteria interaction in the Chowan River system was conducted from March 1974 through June 1977. Due primarily to differences in flow patterns, the river is divided into two sections with respect to phytoplankton dominants: (I) the upper, faster- flowing narrow section from its beginning at the confluence of the Nottoway and Blackwater Rivers to the bend in the river some 16 km downstream; and (2) the lower, wider section with very low water flow that extends approximately 64 km from the deep bend in the river to its mouth near Edenton, North Carolina. The upper river is characterized by seasonal changes in dominants, usually of the flagellated types. Diatoms are omnipresent with fewer blue-green, green, and yellow-green algal types appearing seasonally. The lower river is char- acterized by filamentous blue-green algae during spring and summer. The slower-moving water in this section promotes longer residence time for nutri- ents and algae; therefore, it is plagued with seasonal algae blooms. There are five species that may become dominant during the blooms: (1) Anabaena circinalis, (2) Anabaena aegmlis, (3) Anabaena wisconsinense, (4) Anacystis (Microcystis) firma, and (5) Aphanizomenon fzos-ayme (gracile). The blooms are inversely correlated with nitrate and phosphate concentrations in the river. However, substantial levels of biomass are able to persist after P04, NO3, and NH3 concentrations are below detectable levels. Nutrient recycling by bacteria and fungal activity, nitrogen fixation, and algal physiological utilization of organic phosphorus may facilitate this process. Nitrate was found to be a preferred source of nitrogen by the bloom algae while other algae seemed to prefer ammonia. Nutrient concentrations in the river (NOj, NH3, PO4) were found to quan- titatively support an annual phytoplankton biomass of 0.01 to 30 mg/liter. The higher biomass was found in the lower river during the spring-summer sea- son and in the upper river during the late fall and winter season. Increase in total biomass did not always represent a negative change in water quality. However, poor water quality or late-winter/early-spring increases in nutrient levels subsequently promoted increased biomass by a few species in the lower Chowan, accompanied by a reduction in biomass of other species. This resulted in a rather constant total seasonal biomass even though there may have been a visible bloom on the river. The minimum visible bloom had a mean biomass of 1 mg/l (10~~~/1). The reduced flow in the lower Chowan increased the "nutrient-algal" residence time thereby increasing the potential for an increased algal stand- ing crop; in addition, engendered warmer water promoted increased bacterial- fungal action releasing recycling nutrients into the system. This gave a com- petitive advantage to species with morphological or physiological compatibility to the changed ecological conditions. In its present status, Chowan River water quality, without point-source input, is sensitive to the hydrographical and hydrophysical condition of the river. Sound management practices, therefore, must concentrate on the control- lable conditions that potentially could further decrease water quality. LIST OF FIGURES -No. Page 1 The Chowan River drainage basin of northeastern North Carolina and southeastern Virginia . 7 2 The Chowan River System in southeastern Virginia and northeastern North Carolina, showing towns and sampling sections for project years 1975-77 . 8 3 Diagram showing sampling stations in the Chowan River System . 10 4A Seasonal distribution of algal biomass in the Chowan River, 1974- 1975;StationC-1 .......................... 13 4B Seasonal distribution of algal biomass in the Chowan River, 1974- 1975;StationC-2 .......................... 14 4C Seasonal distribution of algal biomass in the Chowan River, 1974- 1975; Station C-3 (Winton) . .- . 15 4D Seasonal distribution of algal biomass in the Chowan River, 1974- 1975; Station C-4 (Tunis) . 16 4E Seasonal distribution of algal biomass in the Chowan River, 1974- 1975; Station C-5 (below C. F. Industries) . 17 4F Seasonal distribution of algal biomass in the Chowan River, 1974- 1975; Station C-7 . 18 4G Seasonal distribution of algal bi.omass in the Chowan River, 1974- 1975;StationC-8 .......................... 19 4H Seasonal distribution of algal biomass in the Chowan River, 1974- 1975; Station C-9 (Harrellsville) . 20 41 Seasonal distribution of algal biomass in the Chowan River, 1974- 1975; Station C-10 . 21 45 Seasonal distribution of algal biomass in the Chowan River, 1974- 1975; Station C-11 (Colerain) . 22 4K Seasonal distribution of algal biomass in the Chowan River, 1974- 1975; Station C-16 (Edenhouse) . 23 5A Total algal biomass, March 9, 1974 . 24 5B Totalalgalbiomass, April23,1974 . 25 5C Total algal biomass, May 21, 1974 . 26 5D Totalalgalbiomass, June 5,1974. 27 5E Totalalgalbiomass, June 18, 1974 . 28 .. LIST OF FIGURES (continued) Page Total algalbiomass. July 10. 1974 ................ 29 Total algalbiomass. July 11. 1974 ................ 30 Total algal biomass. July 14. 1974 ................ 31 Total algal biomass. August 6. 1974 ............... 32 Total algal biomass. August