Description of freshwater eutrophic soures to Monterey Bay, California, with categorization according to nutrient ratio characteristics Jenny Q. Lane 1, David M. Paradies 2, Karen R. Worcester 3, Raphael M. Kudela 1 1 Department of Ocean Sciences, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA Bay Foundation of Morro Bay, 601 Embarcadero, Suite 11, Morro Bay, CA Central Coast Regional Water Quality Control Board, 895 Aerovista Place, Suite 101, San Luis Obispo, CA Abstract Blooms of Pseudo-nitzschia in central California have alternately been linked to river discharge and/or upwelling processes; a recently published model for toxigenic Pseudo-nitzschia blooms in Monterey Bay, CA suggests resolution of these viewpoints through the consideration of seasonality (Lane et al., 2009). The development of seasonal models identified Pajaro River discharge and nitrate concentration as significant predictors specific to the period of the year when, by definition, local oceanographic conditions are not dominated by upwelling processes. As described by the models, river discharge, through concentrated low- flow periods and ‘load’ events, may provide a eutrophic source of nitrogen conducive to seasonal bloom formation, while allaying immediate bloom formation during periods of peak discharge. The Pajaro River introduces disproportionately large nitrate loads on a highly seasonal basis and is frequently paired with nitrate in conversations on changing regional water quality: nitrate concentration in the Pajaro River has risen from <0.1 mM in the 1950’s to levels that regularly exceed the drinking-water standard of mM (Ruehl et al., 2007). Historical perspectives on the relative significance (or insignificance) of freshwater N-loading to the Monterey Bay system were clearly based on assumptions that no longer apply, and these perspectives are due for re-evaluation. In response to the model results, and to recent evidence that Pseudo-nitzschia growth dynamics and toxicity vary according to N-substrate (nitrate, urea, ammonium), we present quantitative and comparative results from the collection of nitrate, ortho-phosphate, silicic acid, urea, and ammonium samples at: (1) river outflows (monthly), (2) wastewater treatment effluent outflows (quarterly), and (3) stormdrain outflows (seasonally). Categorization of these eutrophic sources according to nutrient ratio characteristics is also discussed. Objectives: Objectives: 1.Describe nutrient concentrations in rivers, streams, stormdrains and wastewater outfalls around Monterey Bay, CA. 2.Characterize these sources of freshwater eutrophication according to their nutrient ratios. Acknowledgements This work was supported by a Benjamin Hammett Award for Research on Climate Change, a STEPS Institute Graduate Research Grant, and a CDELSI Graduate Research Award, and is presented with the support of a CERF Student Travel Award. We would also like to thank M Los Huertos, G Conley, B Hoover, D Harden, L Breaker, S Palacios, M Jacox, M Blakely, M McKibben, and all P3 Project & CCAMP staff and volunteers. Methods Freshwater nutrient concentrations (P3 Project) Sample collection Grab samples were collected by volunteers and staff at the California Department of Fish and Game (CDFG) as part of the Pathogens Pollution Project (P3 Project). River, slough and creek grab samples were collected monthly (May Sept 2008) during daylight hours when outgoing tides reduce the marine influence at the stream mouths. Stormdrain grab samples were collected from each outfall every 1.5 hours over a 4.5 hour period during a winter storm event (08 Jan 2008). Wastewater effluent grab samples were collected quarterly (June Sept 2008) from spigots built into each treatment plant for sample collection. All grab samples were collected into acid-washed plastic bottles (PETG) and transported to the analyzing laboratory (UCSC) in a cooler with blue ice. The grab samples were filtered upon arrival either by syringe-filtration (Whatman ® 0.2  m GD/X) or canister-filtration with low vacuum (Poretics ® 0.6  m polycarbonate membrane; <100mm Hg). Filtrates for ammonium and urea analyses were collected into 50 mL polypropylene (PP) centrifuge tubes (Corning ® ); previous tests have confirmed that these tubes are contaminant free for both urea and ammonium. Filtrates for macronutrient analysis (nitrate plus nitrite [hereafter referred to as nitrate], silicic acid, and ortho-phosphate (hereafter referred to as phosphate]) were collected into in 20 mL low-density polyethylene (LDPE) scintillation vials and stored frozen at -20 °C until analysis. Sample analysis Macronutrients were analyzed with a Lachat Quick Chem 8000 Flow Injection Analysis system using standard colorimetric techniques (Knepel and Bogren, 2001; Smith and Bogren, 2001a,b). Ammonium samples were manually analyzed using the fluorescence method of Holmes et al. (1999). Urea samples were manually analyzed using the diacetyl monoxime thiosemicarbazide technique (Price and Harrison, 1987) modified to account for a longer time period (72 hr) and lower digestion temperature (22 °C) as suggested by Goeyens et al. (1998). Nutrient loading by rivers and wind-driven upwelling Upwelling nutrient loading Daily averaged temperature at 60 m was obtained from the MBARI OASIS mooring dataset for mooring M1 (36.75 N, W). A temperature - nitrate relationship previously established from 6 y of Monterey Bay mooring data (M1/H3; m depth; ) was used to estimate seawater nitrate concentration at depth (Olivieri and Chavez, 2000). A MATLAB script for the calculation of upwelling index from wind vector data was adapted for use with daily averaged winds as they are reported for MBARI OASIS mooring M1, and used to generate estimates of upwelling (volume transport) localized to Monterey Bay. A daily mean upwelling index was obtained from NOAA PFEL for 36 N 122 W for comparative purposes ( Daily volume transports were coupled with corresponding daily estimates of nutrient concentration at 60 m to calculate daily nitrate loading. River and stream nutrient loading Daily nutrient load estimates for Monterey Bay rivers and streams were provided through the the Central Coast Ambient Monitoring Program (CCAMP) and K Worcester (Central Coast Regional Water Quality Control Board). Daily loads were calculated with application of a modified NHD (National Hydrography Datasets) flow model developed by D Paradies to data generated through the CCAMP grab sampling program. Validation exercises have indicated very good model validity (R 2 > 0.86) for Monterey Bay sampling locations. References Goeyens L, Kindermans N, Abu Yusuf M, Elskens M (1998). A room temperature procedure for the manual determination of urea in seawater. Estuarine, Coastal and Shelf Science 47, 415–418. Holmes RM, Aminot A, Kerouel R, Hooker BA, Peterson BJ (1999). A simple and precise method for measuring ammonium in marine and freshwater ecosystems. Canadian Journal of Fisheries and Aquatic Science 56, 1801–1808. Knepel K, Bogren K (2001). Determination of orthophosphorous by flow injection analysis in seawaters. QuickChem Method H, 14 pp. Lane JQ, Raimondi PT, and Kudela RM (2009). Development of a logistic regression model for the prediction of toxigenic Pseudo-nitzschia blooms in Monterey Bay, California, Marine Ecology Progress Series, 383, 37–51. Price N, Harrison P (1987). A comparison of methods for the measurement of dissolved urea concentration in seawater. Marine Biology 92, 307–319. Olivieri RA, Chavez FP (2000). A model of plankton dynamics for the coastal upwelling system of Monterey Bay, California. Deep Sea Research II 47, 1077–1106. Ruehl CR, Fisher AT, Los Huertos M, Wankel SD, Wheat CG, Kendall C, Hatch CE, Shennan C (2007). Nitrate dynamics within the Pajaro River, a nutrient-rich, losing stream J. North American Benthological Society 26(2):191–206. Smith P, Bogren K (2001a). Determination of nitrate and/or nitrite in brackish or seawater by flow injection analysis colorimeter: QuickChem Method E, Saline Methods of Analysis. Lachat Instruments, Milwaukee, WI, 12 pp. Smith P, Bogren K,( 2001b). Determination of silicate in brackish or seawater by flow injection analysis: QuickChem Method C, Saline Methods of Analysis. Lachat Instruments, Milwaukee, WI, 12 pp. Warrick JA, Washburn L, Brzezinski MA, Siegel DA (2005). Nutrient contributions to the Santa Barbara Channel, California, from the ephemeral Santa Clara River. Estuarine, Coastal and Shelf Science 62: 559–574. Nutrient concentrations N-to-S ‘eutrophic arc’. River outfalls to the north and south are relatively low in nutrient concentrations; higher nutrient concentrations are found in central-Bay river outfalls. N-to-S ‘eutrophic arc’. River outfalls to the north and south are relatively low in nutrient concentrations; higher nutrient concentrations are found in central-Bay river outfalls. Urban outfalls & urea. Urea concentrations in high-flow stormdrain outfalls can meet or exceed urea levels generally encountered in heavily eutrophic rivers, and are comparable to urea levels measured directly in wastewater treatment plant effluent. Urban outfalls & urea. Urea concentrations in high-flow stormdrain outfalls can meet or exceed urea levels generally encountered in heavily eutrophic rivers, and are comparable to urea levels measured directly in wastewater treatment plant effluent. Wastewater & phosphate. Phosphate concentrations in wastewater effluent exceed other sources by 1-2 orders of magnitude. Wastewater & phosphate. Phosphate concentrations in wastewater effluent exceed other sources by 1-2 orders of magnitude. SN SN Nutrient ratios Nitrate-enriched river outflows. Nitrate enrichment in the Pajaro and Salinas Rivers translates to nutrient ratios (Si:N:P ~ 250:2000:1) that are extreme relative to other source ratios (e.g. 13:10:1 and 16:5:1 for upwelling and river inputs, respectively [Warrick et al., 2005]). Otherwise, Monterey Bay rivers are relatively silicic acid- enriched (e.g. San Lorenzo River Si:N:P ~ 100:5:1). Nitrate-enriched river outflows. Nitrate enrichment in the Pajaro and Salinas Rivers translates to nutrient ratios (Si:N:P ~ 250:2000:1) that are extreme relative to other source ratios (e.g. 13:10:1 and 16:5:1 for upwelling and river inputs, respectively [Warrick et al., 2005]). Otherwise, Monterey Bay rivers are relatively silicic acid- enriched (e.g. San Lorenzo River Si:N:P ~ 100:5:1). Low Si:P in urban sourcewaters. Monterey Bay wastewater treatment plant effluent and stormdrain outflows are unique in their high P:X ratios (where X = Si and N). Low Si:P in urban sourcewaters. Monterey Bay wastewater treatment plant effluent and stormdrain outflows are unique in their high P:X ratios (where X = Si and N). Nitrate loading by rivers and by wind-driven upwelling A Tale of Three Timescales: is the relative significance (or insignificance) of river loading a matter of temporal resolution? Nitrate at Santa Cruz Municipal Wharf (SCMW) and nitrate loading patterns Seasonal increases in nitrate observed at SCMW align with patterns of nitrate loading by rivers; SCMW is a coastal station near the San Lorenzo River mouth. Rivers, sloughs and creeks * Monthly: May Nov 2008 Stormdrains * Storm event: 08 Jan 2008 Wastewater treatment plants (outflow) * Quarterly: June Nov 2008 Waddell Creek Scotts Creek San Lorenzo River Soquel Creek Pajaro River Watsonville Slough Elkhorn Slough Salinas River Carmel River Big Sur River Woodrow Avenue, Santa Cruz Greenwood Park, Pacific Grove Ocean Avenue, Carmel City of Santa Cruz treatment plant City of Watsonville treatment plant Monterey Regional treatment plant Carmel Area treatment plant S N Nitrate loading by rivers > nitrate loading by upwelling for 27% of daily estimates in these 3 years ( ).