1 State of San Lorenzo River Symposium Nicole Beck, PhD 2NDNATURE April San Lorenzo Lagoon A Decade of Dry Season WQ Monitoring

2 Chain of Aquatic Ecosystem Cause and Effect Morphology Hydrology Vegetation Habitat Biological Communities Morphology Hydrology Vegetation Habitat Biological Communities Water Quality proxy

3 Overview Watershed development Lagoon encroachment

4 National Estuarine Eutrophication Assessment (

5 Integration & Application Network Univ. of Maryland ( ) National Estuarine Eutrophication Assessment (

6 San Lorenzo Lagoon Phytoplankton Dominated Macro Algae Bloom August 2014 Macro Algae Bloom August 2014 No submerged aquatic vegetation (SAV)

7 Soquel Creek Aptos Creek Laguna Creek Branciforte Creek San Lorenzo River Valencia Creek 0.05 mg/L 0.06 mg/L 0.11 mg/L 0.22 mg/L 0.34 mg/L 0.62 mg/L May-Oct averages Dissolved Nitrate-N Loading Santa Cruz Tributaries to Lagoons increasing dissolved nitrate –N concentrations Data compilation from 2NDNATURE, City of Santa Cruz and County of Santa Cruz Environmental Health Scott Creek 0.09 mg/L MALIBU LAGOON; 100 uM Nitrate - N SAN LORENZO LAGOON; 25 uM Nitrate - N

8 Lagoon Morphology 1853 Summer Lagoon ( US Coast Survey Map) 80% reduction in Lagoon surface area (2N 2006) 1997 aerial Deeper lagoon Smaller footprint Less shading

9 Less Shading = Higher water temperatures 1.Salmonids are cold water species 2. Increased organic production and oxygen consumption via respiration > 22 o C threshold of potential impact to habitat quality (71.6 o F) RESPIRATION RATES PHOTOSYNTHETIC RATES 70% increase O2O2 O2O2 O2O2 WATER TEMP 18 o C 24 o C ORGANIC DETRITUS X O 2 consumed 2 x faster 65 o F 75 o F WATER TEMP

10 Why Stratification Matters 100 % 33% 55% Integration & Application Network O2O2 Exacerbate bottom water dissolved oxygen minimums

11 WORMS Minimum Dissolved Oxygen Requirements 100 % 11% 33% 55% Salmonid mortality begins to occur when dissolved oxygen concentrations are below 3 mg/L for periods longer than 3.5 days (US EPA 1986). mg/L % saturation Carter, K. (2005, August) North Coast RWQCB

12 Depth Salinity Water Temperature Dissolved Oxygen Depth Salinity Water Temperature Dissolved Oxygen Inflow (cfs) Monthly DN DP loading Water Quality Monitoring ( ) May - Oct YSI ( ) YSI (30 min; SFC + BTM)

13 San Lorenzo SL3 YSI station ( ) Distance from left bank (ft)

14 Depth Salinity Water Temperature Dissolved Oxygen Depth Salinity Water Temperature Dissolved Oxygen Water Quality Monitoring ( ) May - Oct YSI ( ) Vertical profiles YSI (2014) YSI (30 min; SFC + BTM) (2 weeks; every 0.5 ft) Depth Salinity Water Temperature Dissolved Oxygen Depth Salinity Water Temperature Dissolved Oxygen

15 Santa Felton Water Year Precipitation Water year types defined by City of Santa Cruz Water Department 2014 AUGUST Q md = 1.9 cfs LOWEST OF RECORD

SANDBAR STATUS OPEN CLOSED OPEN CLOSED

CLOSED 115 days OR 89% of the season (MAY-OCT) MOST FREQUENTLY CLOSED LAGOON OF RECORD May- Mid July Mostly OPEN Late Aug – Oct Mostly CLOSED Mid July- Late Aug 50/50 SANDBAR CLOSURE May – Oct 2014 # of days per week OPEN

18 SL6 SL3 SALINITY ppt +8 ppt

19 SL6 SL3 TEMPERATURE o C +24 o C Frequency SURFACE Temp > 22 o C: 64% Frequency of BOTTOM Temp > 22 o C: 78% HIGHEST OF RECORD Frequency SURFACE Temp > 22 o C: 64% Frequency of BOTTOM Temp > 22 o C: 78% HIGHEST OF RECORD 10yr means SFC (16%) BTM (24%)

20 SL6 SL3 DISSOLVED OXYGEN 2014 Frequency of BOTTOM Dissolved Oxygen < 3 mg/L: 30% 10 yr AVERAGE Frequency of BOTTOM Dissolved Oxygen < 3 mg/L: 30% 10 yr AVERAGE

21 San Lorenzo Lagoon 10 yr average ( ) Salinity OPEN CLOSED Lagoon Water Surface Surface YSI Bottom YSI

22 San Lorenzo Lagoon 10 yr average ( ) Temperature OPEN CLOSED +22 o C

23 San Lorenzo Lagoon 10 yr average ( ) Dissolved Oxygen OPENCLOSED < 4 mg/L OPEN Lagoon (on average) More mixing Less volume Cooler Higher dissolved oxygen OPEN Lagoon (on average) More mixing Less volume Cooler Higher dissolved oxygen

24 Surface Bottom cooling San Lorenzo Lagoon July – September CLOSED sand bar 10 year average 2014 in black Increasing summer inflows cools SFC water temperatures by over 3 o C. Similar, but less dramatic, decreasing trend in bottom waters temperatures. Increasing summer inflows cools SFC water temperatures by over 3 o C. Similar, but less dramatic, decreasing trend in bottom waters temperatures.

25 Salinity Ratio Bottom Dissolved Oxygen increase stratification Stratification increases with increasing summer inflows Summer inflows have no consistent influence on Lagoon DO Stratification increases with increasing summer inflows Summer inflows have no consistent influence on Lagoon DO San Lorenzo Lagoon July – September CLOSED sand bar 10 year average 2014 in black

26 San Lorenzo Lagoon Annual Cycle Storm conveyance: Bed scour OPEN; Daily tidal exchange NET EXPORT Storm conveyance: Bed scour OPEN; Daily tidal exchange NET EXPORT CLOSED 50% of the time Reduced tidal exchange MAX annual temperatures Peak photosynthetic rates CLOSED 50% of the time Reduced tidal exchange MAX annual temperatures Peak photosynthetic rates WINTER (Nov- Mar) SPRING (April – May) SUMMER (June – Aug) FALL (Sept- Oct) Inflow variability declines Predominately OPEN; Daily tidal exchange Organic accumulation begins Inflow variability declines Predominately OPEN; Daily tidal exchange Organic accumulation begins CLOSED 80% of the time Minimal to NO tidal exchange MAX volume of organic material Annual dissolved oxygen MIN CLOSED 80% of the time Minimal to NO tidal exchange MAX volume of organic material Annual dissolved oxygen MIN

27 Take Home Messages San Lorenzo Lagoon is relatively eutrophic and the existing morphology exacerbates these effects. Nitrogen source control actions Increase shading Promote SAV establishment all may be effective at improving summer lagoon conditions. In its current condition, summer Lagoon water quality is consistently better when the sand bar is open. (also has more salmonids). Increasing summer inflow cools the lagoon, but also increases the magnitude of stratification. Available data suggests inflow has no direct influence on BTM DO. San Lorenzo Lagoon is relatively eutrophic and the existing morphology exacerbates these effects. Nitrogen source control actions Increase shading Promote SAV establishment all may be effective at improving summer lagoon conditions. In its current condition, summer Lagoon water quality is consistently better when the sand bar is open. (also has more salmonids). Increasing summer inflow cools the lagoon, but also increases the magnitude of stratification. Available data suggests inflow has no direct influence on BTM DO.