Extent of Eutrophication in Southern California Estuaries

Transcription

1 Extent of Eutrophication in Southern California Estuaries Martha Sutula and Karen McLaughlin SCCWRP Presentation to Orange County Coastal Coalition May 17, 2012

2 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

3 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?

4 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

5 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)

6 Study Design 27 Segments from 23 Estuaries; Randomly Selected Monitored from Nov Oct 2009 Targeted index area within each estuary-- Most Conservative Answer

7 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

8 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

9 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 % cover 25 g dw m % cover 76 g dw m % cover

10 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 Very Low 30 Chlorophyll a (mg/l) Chlorophyll a (mg/l) /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 /1/08 2/1/09 4/1/09 6/1/09 8/1/09 10/1/09 12/1/09 Low

11 Dissolved Oxygen Assessment 10th percentile of hourly running average DO data (mg/l) Very High 5.7 High Moderate Low Very Low < % Time Ecological Condition Interpreted from WFD Framework Very Low Moderate Very High th %tile Dissolved Oxygen Concentration (mg/l) 25

12 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

13 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

14 What OC Estuaries Were Monitored?

15 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

16 OC Estuaries Ranking Among 27 Sites Segment Percentile Rank Among All Estuarine Segments Macroalgae Phytoplankton Dissolved Oxygen Seal Beach - Full Seal Beach- Muted Bolsa Chica- Full Bolsa Chica - Muted Santa Ana River San Juan Creek Higher is Better

17 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

18 Questions? Martha Sutula Karen McLaughlin

19 Representative Primary Producers: Macroalgae Dominant with Few Exceptions January September May % Carbon Biomass 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