Extent of Eutrophication in Southern California Estuaries Martha Sutula and Karen McLaughlin SCCWRP Presentation to Orange County Coastal Coalition May 17, 2012
Why Assess Eutrophication in Southern California Bight Estuaries? Eutrophication is one of the leading causes of degraded biological condition in US water bodies Regional problem, lack of data Bight Program = opportunity First large scale assessment in southern California Consensus on indicators and protocols
Key Questions What is the extent and magnitude of eutrophication in southern California estuaries? How do OC estuaries rank among those assessed? Is indicator response driven by nutrient concentrations or nutrient loads?
Conceptual Model of Development of Eutrophication in SCB Estuaries Nutrient load Nutrient load Shading Light Light Macroalgae Phytoplankton Changes in Water Chemistry (DO, ph) Minimally Disturbed Increased Nutrient Loading Changes in Sediment Chemistry (Sulfide, Ammonia) Affected by Eutrophication Seagrass Benthic Diatoms Macroalgae Phytoplankton
Approach Indicators of eutrophication: Primary producers biomass and cover, bimonthly Macroalgae Phytoplankton Brackish-Water Submerged Aquatic Vegetation Dissolved Oxygen continuous in bottom water Nutrient loads or nutrient concentrations? Estuarine ambient nutrients- bimonthly Riverine Nutrient Loading Continuous flow Dry weather concentrations- bimonthy MS4 data or modeled (Sengupta et al. in prep)
Study Design 27 Segments from 23 Estuaries; Randomly Selected Monitored from Nov 2008 - Oct 2009 Targeted index area within each estuary-- Most Conservative Answer
How to Assess Extent and Magnitude of Eutrophication? CA NNE still in development Evaluated existing frameworks, selected EU-WFD Framework Macroalgae Phytoplankton European Union-Water Framework Directive ASSETS- National Estuarine Eutrophication Assessment National Coastal Assessment Dissolved Oxygen X X X Nutrients Concentration, load, or combination Narrative Only X X Only loads Narrative Only Narrative Only X Only concentration
European Union Water Framework Directive Categorize estuaries based on ecological condition Very High Thresholds for indicators related to biological response to eutrophication Dissolved oxygen Macroalgae Phytoplankton Doesn t specify how to combine indicators Ecological Condition High Moderate Low Very Low Considered Problem Area
Macroalgae Assessment Biomass (g dw m -2 ) Ecological Condition Interpreted from WFD Framework Percent Cover 5% > 5% > 15% > 25% > 75% > 415 Moderate Low V. Low V. Low V. Low > 140 Moderate Moderate Low V. Low V. Low > 70 High Moderate Moderate Low Low > 15 V. High High High Moderate Low 15 V. High High High Moderate Moderate Very High High Moderate Low 2 g dw m -2 4% cover 7 g dw m -2 17 % cover 25 g dw m -2 65 % cover 76 g dw m -2 79 % cover
Phytoplankton Assessment Ecological Condition Interpreted from WFD Framework Annual Average of Sonde Chlorophyll a (µg/l) Very High < 5 High 5-7 Moderate 7-10 Low 10-30 Very Low 30 Chlorophyll a (mg/l) Chlorophyll a (mg/l) 100 50 0 12/1/08 2/1/09 4/1/09 6/1/09 8/1/09 10/1/09 12/1/09 Very High 100 Annual Average: 3 mg L -1 Annual Average: 21 mg L -1 50 0 12/1/08 2/1/09 4/1/09 6/1/09 8/1/09 10/1/09 12/1/09 Low
Dissolved Oxygen Assessment 10th percentile of hourly running average DO data (mg/l) Very High 5.7 High 4.0-5.7 Moderate 2.4-4.0 Low 1.6-2.4 Very Low < 1.6 100 80 % Time Ecological Condition Interpreted from WFD Framework Very Low Moderate Very High 60 40 10th %tile 20 0 0 5 10 15 20 Dissolved Oxygen Concentration (mg/l) 25
According to WFD, Eutrophication is Pervasive in SCB Estuaries Indicator % With Ecological Condition Less than High Any One 96% Either Primary Producer & DO 52% Macroalgae 78% Phytoplankton 37% Dissolved Oxygen 59% Ecological Condition Very High High Moderate Low Very Low
Uncertainties Did we adequately capture variability? Temporal variability Spatial variability What is the appropriate assessment framework for SCB estuaries? Relevance of European thresholds? Little guidance on data management Little guidance on frequency of sampling or how to incorporate event duration
What OC Estuaries Were Monitored?
How Did OC Estuaries Fair? Segment Macroalgae Phytoplankton Dissolved Oxygen Very High Seal Beach - Full Seal Beach- Muted Bolsa Chica- Full Bolsa Chica - Muted Santa Ana River Ecological Condition High Moderate Low San Juan Creek Very Low
OC Estuaries Ranking Among 27 Sites Segment Percentile Rank Among All Estuarine Segments Macroalgae Phytoplankton Dissolved Oxygen Seal Beach - Full 85 70 48 Seal Beach- Muted 67 56 85 Bolsa Chica- Full 41 59 81 Bolsa Chica - Muted 30 85 44 Santa Ana River 56 93 67 San Juan Creek 52 7 70 Higher is Better
Summary Based on WFD, eutrophication is pervasive in SCB segments OC Estuaries are high to low condition (moderately eutrophic) Indicator response related to nutrient loads, not nutrient concentrations Additional work to increase precision Indicators related to nutrient loading on different time scales Macroalgae and phytoplankton significantly correlated with nutrient loading DO significantly correlated with sediment organic matter; integrating effects of eutrophication over a longer period
Questions? Martha Sutula marthas@sccwrp.org Karen McLaughlin karenm@sccwrp.org
Representative Primary Producers: Macroalgae Dominant with Few Exceptions 100.00 January September May 2009 2009 2009 75.00 % Carbon Biomass 50.00 25.00 1.00 0.75 0.50 0.25 0.00 DL UCL GS SCR MLM MLF ZC TC BL BW SBM SBF BCM BCF SAR SJC SMC SME AHL BQL SEL LPL MB SDR SDF SDM TJE SAV Macroalgae Phytoplankton