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I will be examining how chlorophyll relates to exceedences in the following water quality parameters (criteria/thresholds in parentheses): 1.

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Presentation on theme: "I will be examining how chlorophyll relates to exceedences in the following water quality parameters (criteria/thresholds in parentheses): 1."— Presentation transcript:

1 I will be examining how chlorophyll relates to exceedences in the following water quality parameters (criteria/thresholds in parentheses): 1

2 I will be examining how chlorophyll relates to exceedences in the following water quality parameters (criteria/thresholds in parentheses): 1) Dissolved oxygen (5.5 mg/l or 5.0 mg/l) 2

3 I will be examining how chlorophyll relates to exceedences in the following water quality parameters (criteria/thresholds in parentheses): 1)Dissolved oxygen (5.5 mg/l or 5.0 mg/l) 2)pH (6-9) 3

4 I will be examining how chlorophyll relates to exceedences in the following water quality parameters: 1)Dissolved oxygen (5.5 mg/l or 5.0 mg/l) 2)pH (6-9) 3)Percent-Light-Through-Water (22% or 13%) From EPA-CPB’s “Chesapeake Bay Submerged Aquatic Vegetation Water Quality and Habitat-Based Requirements and“Chesapeake Bay Submerged Aquatic Vegetation Water Quality and Habitat-Based Requirements and Restoration Targets: A Second Technical Synthesis” (2000) 4

5 I will be examining how chlorophyll relates to exceedences in the following water quality parameters: 1)Dissolved oxygen (5.5 mg/l or 5.0 mg/l) 2)pH (6-9) 3)Percent-Light-Through-Water (22% or 13%) 4)DO Saturation (125%) 5

6 Excessive dissolved gas super-saturation is associated with: · Bubble formation in the cardiovascular system, causing blockage of blood flow and death (Jensen 1980, Weitkamp and Katz 1980, Fidler 1988). · Overinflation and possible rupture of the swim bladder in young (or small) fish, leading to death or problems of overbuoyancy (Shirahata 1966, Jensen 1980, Fidler 1988, Shrimpton et al. 1990a and b). · Extracorporeal bubble formation in gill lamella of large fish or in the buccal cavity of small fish, leading to blockage of respiratory water flow and death by asphyxiation (Fidler 1988, Jensen 1988). · Sub-dermal emphysema on body surfaces, including the lining of the mouth. Blistering of the skin of the mouth may also contribute to the blockage of respiratory water flow and death by asphyxiation (Fidler 1988, White et al. 1991). Source: British Columbia Water Quality Guidelines of Dissolved Gas Supersaturation (1994)British Columbia Water Quality Guidelines of Dissolved Gas Supersaturation (1994) Gas bubble trauma in a juvenile rainbow trout 6

7 In addition to being linked to harmful impacts on aquatic life, DO super-saturation is also an excellent indicator of algal blooms. USA EPA (1986) recommends a dissolved gas criterion of 110% to protect aquatic life. Other sources suggest 125% for DO saturation. This is the number I’ve chosen to use as a threshold. 7

8 8 I will be examining how chlorophyll relates to exceedences in the following water quality parameters: 1)Dissolved oxygen (5.5 mg/l or 5.0 mg/l) 2)pH (6-9) 3)Percent-Light-Through-Water (22% or 13%) 4)DO Saturation (125%) 8

9 I’m analyzing three types of monitoring data: 1)DATAFLOW (HRSDS and VIMS) 2)Long-term, mid-channel fixed stations (DEQ) 3)Continuous (VIMS) 9

10 DATAFLOW provides a precise estimation of chlorophyll in space. When run frequently (as it is in the lower James), it also captures temporal variability. These two qualities make DATAFLOW the ideal dataset for assessing chlorophyll. So if there are relationships between chlorophyll and water quality exceedences, I would expect to find evidence in the DATAFLOW data. 10

11 Step 1. Plot DATAFLOW cruisetrack points… Case study: JMSMH 11

12 …over Bay Interpolator cells JMSMH 12

13 Step 2. Generate descriptive statistics for each cell that intersects a cruise point mean chlorophyll mean DO concentration mean K d mean pH mean DO Saturation % JMSMH 13

14 From EPA’s 2008 Technical Support for Criteria Assessment Protocols Addendum2008 Technical Support for Criteria Assessment Protocols Addendum percent-light-through-water 14

15 Step 3. Repeat for each cruise. For the results I’m going to show, I used 71 summertime cruises from This resulted in 8748 samples (cell averages). 15

16 Probability of Exceeding Selected Water Quality Parameter Thresholds Based on cell-averaged DATAFLOW measurements JMSMH, July-September (n=8748) criterion= 10 ug/l 16

17 Based on cell-averaged DATAFLOW measurements JMSMH, summer months (n=8748) DO and pH exceedences are very rare in the daytime surface waters monitored by DATAFLOW. Exceedence rates in DO Sat and PLW appear to increase with chlorophyll. This analysis would seem to suggest that the current criterion (10 ug/l) is protective of water quality. Probability By bin Cumulative Probability By bin Cumulative Probability 17

18 JMSMH Summer Based on semi-monthly/monthly fixed station monitoring conducted by DEQ and VIMS, (n=29). BUT… There doesn’t seem to be a relationship between seasonal chlorophyll averages and water quality exceedence rates. Dissolved Oxygen Water Clarity 18

19 Summer chlorophyll averages and 90 th percentiles based on DATAFLOW, plotted against the exceedence rate of the 30-Day Mean DO criterion (5.0 mg/l) observed at DEQ/VIMS fixed stations JMSMH 19

20 CONMON data allow us to answer these important questions: 1)Over what time period(s) do we see relationships between chlorophyll and water quality exceedences? 2) How do these relationships change with increasing duration? 20

21 Four durations examined: 1)Instantaneous chlorophyll (15-minute observations) 2)24-hour average chlorophyll 3)7-day average chlorophyllrolling averages 4) 30-day average chlorophyll Following results are for JMSOH Summer 21

22 JMSOH CONMON Summer Instantaneous Chlorophyll n=23,115 22

23 n=23,353 JMSOH CONMON Summer hour Average Chlorophyll 23

24 n=22,624 JMSOH CONMON Summer Day Average Chlorophyll 24

25 n=16,000 JMSOH CONMON Summer Day Average Chlorophyll 25

26 Three things jump out at me… 26

27 Three things jump out at me… 1.The chlorophyll bin where we see a jump in exceedences shifts to lower values with increasing duration. 27

28 The chlorophyll bin where we see a jump in exceedences shifts to lower values with increasing duration. 28

29 Three things jump out at me… 1.The chlorophyll bin where we see a jump in exceedence rate shifts to lower values with increasing duration. 2. The strength of a relationship is dependent on the duration. 29

30 “If we can keep the chlorophyll at less than 10 ug/l, water clarity will still be poor. But at least we won’t make it worse!” “There isn’t a relationship between chlorophyll and water clarity.” 30

31 Three things jump out at me… 1.The chlorophyll bin where we see a jump in exceedence rate shifts to lower values with increasing duration. 2. Exceedences can be obscured by increasing duration. 3. The duration affects how we talk about exceedences. 31

32 “DO saturation was excessive in JMSOH 6% of the time during the summer months.” “JMSOH experienced excessive DO saturation levels during 26% of the 24-hour periods monitored during this study.” “22% of the 7-day periods sampled in JMSOH were characterized by at least 16 hours of excessive DO saturation levels.” “12% of the 30-day periods sampled in JMSOH were found to have at least 72 hours of excessive DO saturation levels.” All the statements below describe the same dataset, just parsed in different ways. But which statement is more meaningful to aquatic life? 32

33 ns ns= no significant difference, Wilcoxon-Rank Sum test 33

34 ns a a b a b c ns= no significant difference Kruskal-Wallis ANOVA Pairwise Wilcoxon Rank Sum 34

35 Based on summertime DEQ/VIMS fixed station monitoring in JMSOH, Red line indicates the chlorophyll criterion for this segment-season. (n = 29) 35

36 36 Spearman r=.56


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