Chapter 2. Oceanographic Conditions

Home , Mission Bay (San Diego)

Chapter 2. Oceanographic Conditions relative to other input sources, (3) determine the extent INTRODUCTION to which water mass movement or mixing affects the The City of San Diego monitors oceanographic dispersion/dilution potential for discharged materials, conditions in the region surrounding the Point Loma and (4) demonstrate the infl uence of natural events Ocean Outfall (PLOO) to assist in evaluating possible such as storms or El Niño/La Niña oscillations. impacts of wastewater discharge on the marine environment. Treated wastewater is discharged to the The evaluation and interpretation of bacterial Pacifi c Ocean via the PLOO at depths of ~94–98 m distribution patterns and remote sensing and at a distance of approximately 7.2 km west of observations (e.g., aerial and satellite imagery) may the Point Loma peninsula. The fate of wastewater also provide useful information on the horizontal discharged into offshore waters is determined by transport of wastewater plumes (Pickard and oceanographic conditions that impact water mass Emery 1990; Svejkovsky 2009; also see Chapter 3 movement, including horizontal and vertical mixing of this report). Thus, the City of San Diego combines of the water column and current patterns. These same measurements of physical oceanographic parameters factors can also affect the distribution of turbidity with assessments of fecal indicator bacteria (FIB) (or contaminant) plumes that originate from various concentrations and remote sensing data to provide point and non-point sources. In the Point Loma further insight into the transport potential in coastal region these include tidal exchange from San Diego waters surrounding the PLOO discharge site. Bay and Mission Bay, outfl ows from the San Diego River, the Tijuana River and northern San Diego This chapter describes the oceanographic conditions County lagoons and estuaries, storm drains or other that occurred in the Point Loma region during 2008. water discharges, and surface water runoff from local The results reported herein are also referred to in watersheds. For example, fl ows from San Diego subsequent chapters to explain patterns of FIB Bay and the Tijuana River are fed by 1075 km2 distributions (see Chapter 3) or other changes in the and 4483 km2 of watershed, respectively, and can local marine environment (see Chapters 4–7). contribute signifi cantly to nearshore turbidity, sediment deposition, and bacterial contamination (see Largier et al. 2004, Terrill et al. 2009). Overall, MATERIALS AND METHODS these different sources can affect water quality conditions either individually or synergistically. Field Sampling

Because of the above, evaluations of oceanographic Oceanographic measurements were collected at ﬁxed parameters such as water temperature, salinity, and sampling sites located in a grid pattern surrounding density that determine the mixing potential of the the PLOO (Figure 2.1). Thirty-six offshore stations water column are important components of ocean (designated F01–F36) were sampled quarterly in monitoring programs (Bowden 1975). Analysis of January, April, July, and October, usually over a 3-day the spatial and temporal variability of these and other period. Three of these stations (F01–F03) are located parameters (e.g., light transmittance or transmissivity, along the 18-m depth contour, while 11 sites are dissolved oxygen, pH, and chlorophyll) may located along each of the following depth contours: also elucidate patterns of water mass movement. 60-m contour (stations F04–F14); 80-m contour Monitoring patterns of change in these parameters for (stations F15–F25); 98-m contour (stations F26–F36). the receiving waters surrounding the PLOO can help: Eight additional stations located in the Point Loma (1) describe deviations from expected oceanographic kelp bed are subject to the 2001 California Ocean Plan patterns, (2) assess the impact of the wastewater plume (COP) water contact standards (SWRCB 2001). These

PLOOOceanCond2008.indd 11 6/29/2009 2:47:04 PM La Jo lla Remote Sensing – Aerial and Satellite Imagery

F14 F03 F25 ! ! F36 ! ! Coastal monitoring of the PLOO region during 2008 F13 F24 ! ! o River also included aerial and satellite image analysis F35 F02 San D ieg ! ! F12 San Diego performed by Ocean Imaging of Solana Beach, CA F23 ! F34 ! ! C8 a (see Svejkovsky 2009). All usable images for the ! F11 F22 ! F33 ! monitoring area captured during the year by the ! C7 o Ba ! nt Lom eg y Di n F10 a Moderate Resolution Imaging Spectroradiometer F21 ! Poi S F32 ! ! A6 C6 Co r o na do (MODIS) satellite were downloaded, and 22 high ! ! F31 F20 F09 ! ! ! C5 clarity Landsat Thematic Mapper (TM) images and A7 ! F08 ! F19 ! two Aster images were acquired. High resolution F30 ! C4 ! Outfall ! Point Loma A1 1 ! 0 m aerial images were collected using Ocean Imaging’s F18 F07 F29 ! ! ! DMSC-MKII digital multispectral sensor. The F01 ! F17 F06 F28 ! DMSC’s four channels were confi gured to a ! ! specifi c wavelength (color) combination designed LA5 F27 F16 F05 ! ! ! to maximize detection of the wastewater discharge F26 F15 F04 ! ! ! signature by differentiating between the waste field 150 4 m LA4 and coastal turbidity plumes. Depth of penetration km

100

80 m 20 1 60 m 0 1 2 3 4 5 50

m m m for this sensor varies between 8–15 m depending Figure 2.1 on water clarity. The spatial resolution of the data Water quality monitoring stations where CTD casts are is dependent upon aircraft altitude, but is typically taken, Point Loma Ocean Outfall Monitoring Program. maintained at 2 m. Fifteen DMSC overflights were conducted in 2008, which consisted of one to five stations include three sites (stations C4, C5, C6) located fl ights per month during winter when the surfacing along the inshore edge of the kelp bed paralleling the potential was greatest for the wastewater plume 9-m depth contour, and fi ve sites (stations A1, A6, A7, (see below) and when rainfall was also greatest. In C7, C8) located along the 18-m depth contour near contrast, only three surveys were fl own during the the offshore edge of the kelp bed. To meet 2001 COP spring and late summer months. sampling frequency requirements for kelp forest areas, sampling at the eight kelp bed stations was conducted Data Treatment fi ve times per month. The water column parameters measured in 2008 Data for the various oceanographic parameters were were summarized by quarter in two different ways: collected using a SeaBird conductivity, temperature, and (1) means calculated over the entire water column depth (CTD) instrument. The CTD was lowered through for each station, and (2) means calculated over all the water column at each station to collect continuous stations located along each depth contour (i.e., 9-m, measurements of water temperature, salinity, density, 18-m, 60-m, 80-m, 98-m). In order to get a view of pH, water clarity (transmissivity), chlorophyll a, and the entire PLOO region for each quarterly survey, dissolved oxygen (DO). Profi les of each parameter these analyses included data from all 36 of the were then constructed for each station by averaging the offshore stations, as well as the data from the eight data values recorded over 1-m depth intervals. This data kelp bed stations that were sampled at approximately reduction ensured that physical measurements used the same time (i.e., ± one day). Each water column in subsequent analyses could correspond to discrete parameter was also summarized over all kelp bed sampling depths for indicator bacteria (see Chapter 3). stations each month for surface (≤ 2 m) and bottom Visual observations of weather and water conditions depths (10–20 m); this was done to identify seasonal were recorded just prior to each CTD cast. trends not necessarily evident in the quarterly data.

PLOOOceanCond2008.indd 12 6/29/2009 2:47:10 PM Finally, the spatial distributions of temperature and 5 A 2008 mean salinity values at each offshore station were mapped 4 Historical mean for each quarterly survey, with the data limited to 3 SD the discrete depths at which seawater samples are 2 collected for bacterial analysis. 1

Rainfall (in.) 0 In addition to the above, mean temperature, salinity, -1 DO, pH, and transmissivity data from 2008 were

75 compared with historical proﬁ le plots consisting B 70 of means for 1991–2007 ± one standard deviation. Data for these historical analyses were summarized 65 at 5-m depth increments and limited to the three 60 stations located nearest the outfall discharge site 55

along the 98-m depth contour. These included station Temperature (°F) 50 l F30 located immediately offshore of the center of n y n u c eb a J the outfall wye, station F29 located 1.25 km south Ja F Mar Apr M Ju Aug Sep Oct Nov De of the southern diffuser leg, and station F31 located Month ~1.42 km north of the northern diffuser leg. Figure 2.2 Comparison of rainfall (A) and air temperatures (B) at Lindbergh Field (San Diego, CA) for 2008 compared to historical levels. For 2008, rainfall data are expressed as ESULTS AND ISCUSSION R D total inches per month, whereas temperature data are monthly averages. Historical rainfall and temperature data Climate Factors and Seasonality are expressed as monthly means ± one standard deviation (SD) for the historical period 1914 through 2007. Southern California weather can generally be classifi ed into wet (winter) and dry (spring–fall) begin to warm surface waters resulting in increased seasons (NOAA/NWS 2009a), and differences surface evaporation (Jackson 1986). Mixing conditions between these seasons affect certain oceanographic diminish with decreasing storm activity, and seasonal conditions (e.g., water column stratifi cation, current thermoclines and pycnoclines become re-established. patterns and direction). Understanding patterns of Once the water column becomes stratifi ed again by late change in such conditions is important in that they spring, minimal mixing conditions typically remain can affect the transport and distribution of wastewater, throughout the summer and early fall months. In storm water, or other types of turbidity plumes that October or November, cooler temperatures associated may arise from various point or non-point sources. with seasonal changes in isotherms, reduced solar Winter conditions typically prevail in southern input, along with increases in stormy weather, begin to California from December through February during cause the return of well-mixed or non-stratifi ed water which time higher wind, rain and wave activity column conditions. often contribute to the formation of a well-mixed or relatively homogenous (non-stratified) water column, Total rainfall in 2008 was just over 12 inches in the and can decrease surface salinity (Jackson 1986). The San Diego region, which exceeded the historical chance that the wastewater plume from the PLOO average (NOAA/NWS 2009b). Rainfall followed may surface is highest during such times when there is expected seasonal storm patterns, with the greatest little, if any, stratifi cation of the water column. These and most frequent rains occurring during the winter conditions often extend into March as the frequency and fall months (Figure 2.2A). Air temperatures of winter storms decreases and the seasons begin to were generally similar during the year to historical transition from wet to dry. In late March or April the values, although exceptions occurred in October and increasing elevation of the sun and lengthening days November (Figure 2.2B).

PLOOOceanCond2008.indd 13 6/29/2009 2:47:11 PM and then declined through December (Figure 2.4). Oceanographic Conditions in 2008 These relatively high salinities correspond to the lower temperatures that were found at both surface Water Temperature and bottom depths in April as described above, In 2008, mean surface temperatures across the which is likely indicative of some upwelling in entire PLOO region ranged from 13.4°C in January the region during the spring months. Salinity to 20.9°C in October, while bottom temperatures values demonstrated no detectable trends relative averaged from 9.5°C in April to 18.5°C in October to the wastewater discharge site (Appendix A.1, (Table 2.1). Water temperatures varied as expected Figure 2.5). by depth and season, with no discernible patterns relative to wastewater discharge (Appendix A.1, Density Figure 2.3). For example, the lowest temperatures Seawater density is a product of temperature, of the year occurred during April at bottom depths salinity, and pressure, which in the shallower along all of the depth contours (Table 2.1), which coastal waters of southern California is influenced probably refl ected typical spring upwelling in the primarily by temperature differences since salinity region. Thermal stratifi cation at stations within the is relatively uniform (Bowden 1975, Jackson 1986, Point Loma kelp forest also followed normal seasonal Pickard and Emery 1990). Therefore, changes in patterns with the least stratification occurring density typically mirror those in water temperatures. during the winter months of January, February This relationship was true in the Point Loma region and December, and the greatest stratifi cation in during 2008; the differences between surface and July–August (Figure 2.4). Although data for the bottom water densities resulted in a pycnocline at the 36 offshore stations off Point Loma are limited to offshore stations that was evident in the April, July, only four times a year, thermal stratifi cation at these and October survey data, with maximum density stations appeared to follow typical seasonal patterns stratifi cation occurring in July (Appendix A.1). as well, with the water column ranging from slightly stratifi ed in January to strongly stratifi ed in July Dissolved Oxygen and pH and October (see Figure 2.3). Since temperature is Dissolved oxygen (DO) concentrations averaged the main contributor to water column stratification from 6.5 to 10.1 mg/L in surface waters and from 2.4 in southern California (Dailey et al. 1993, Largier to 7.4 mg/L in bottom waters, while mean pH values et al. 2004), differences between surface and ranged from 8.1 to 8.3 in surface waters and from bottom temperatures were important to limiting the 7.7 to 8.1 in bottom waters across the Point Loma surface potential of the waste fi eld throughout the region in 2008 (Table 2.1). Changes in pH patterns year. Moreover, the PLOO wastewater plume was were closely linked to changes in DO since both not detected in surface waters at any time during parameters tend to refl ect the loss or gain of carbon the year based on remote sensing observations dioxide associated with biological activity in shallow (see Svejkovsky 2009) or the results of discrete waters (Skirrow 1975). For example, concentrations bacteriological samples (see Chapter 3). of both parameters peaked during June in surface waters at the kelp bed stations, which corresponded Salinity to peak concentrations of chlorophyll a indicative of Average salinities ranged from a low of 33.21 ppt seasonal plankton blooms (Figure 2.4). In contrast, the in January to 33.83 ppt during April in surface lowest concentrations of both parameters occurred in waters, and from 33.35 ppt in October to 34.14 ppt bottom waters along all depth contours during April in April at bottom depths (Table 2.1). As with (Table 2.1). These low values near the sea fl oor during temperature, salinity values also appeared to follow spring may be due to regional upwelling as suggested expected seasonal patterns. Salinities were highest by temperature and salinity data (see above). Changes at bottom depths across the region in April. At the in DO and pH levels relative to the wastewater kelp bed stations, salinities also peaked in April discharge were not discernible (Appendix A.1).

PLOOOceanCond2008.indd 14 6/29/2009 2:47:12 PM Table 2.1 Summary of temperature, salinity, dissolved oxygen, pH, transmissivity, and chlorophyll a for surface and bottom waters in the PLOO region during 2008. Values are expressed as means for each survey pooled over all stations along each depth contour. Jan Apr Jul Oct Jan Apr Jul Oct Temperature pH 9-m Surface 13.5 14.7 20.4 19.8 9-m Surface 8.1 8.3 8.2 8.1 Bottom 13.4 11.1 15.7 18.5 Bottom 8.1 8.0 8.1 8.1

18-m Surface 13.4 14.3 19.5 19.6 18-m Surface 8.1 8.2 8.2 8.2 Bottom 12.9 10.5 12.8 13.8 Bottom 8.0 7.9 8.0 8.0

60-m Surface 13.6 15.4 19.5 20.2 60-m Surface 8.2 8.1 8.1 8.3 Bottom 11.8 9.9 10.9 12.2 Bottom 7.9 7.7 7.8 8.0

80-m Surface 13.6 15.6 19.3 20.9 80-m Surface 8.2 8.2 8.1 8.3 Bottom 11.4 9.7 10.4 11.9 Bottom 7.8 7.7 7.7 8.0

98-m Surface 13.8 15.4 19.1 20.7 98-m Surface 8.2 8.1 8.1 8.3 Bottom 11.0 9.5 10.0 11.5 Bottom 7.8 7.7 7.7 7.9

Salinity Transmissivity 9-m Surface 33.37 33.83 33.65 33.37 9-m Surface 76 59 80 85 Bottom 33.41 33.96 33.71 33.51 Bottom 75 59 81 77

18-m Surface 33.21 33.78 33.63 33.46 18-m Surface 76 67 83 86 Bottom 33.52 33.94 33.65 33.35 Bottom 76 78 81 82

60-m Surface 33.42 33.65 33.61 33.49 60-m Surface 82 77 87 86 Bottom 33.68 34.00 33.69 33.39 Bottom 81 84 87 87

80-m Surface 33.44 33.67 33.57 33.52 80-m Surface 84 80 87 86 Bottom 33.78 34.07 33.78 33.50 Bottom 87 88 87 90

98-m Surface 33.50 33.66 33.52 33.53 98-m Surface 86 81 88 87 Bottom 33.86 34.14 33.92 33.58 Bottom 89 89 89 90

Dissovled Oxygen Chlorophyll a 9-m Surface 7.8 10.1 8.7 6.5 9-m Surface 1.3 8.7 2.6 1.7 Bottom 7.4 3.7 6.4 6.8 Bottom 1.6 7.0 2.8 2.9

18-m Surface 8.1 9.0 8.5 7.7 18-m Surface 3.7 8.4 3.4 2.0 Bottom 6.8 3.7 6.7 6.6 Bottom 2.7 7.0 5.7 2.1

60-m Surface 8.0 8.9 8.4 8.0 60-m Surface 2.7 4.6 1.3 1.0 Bottom 4.9 2.7 4.8 6.6 Bottom 1.3 2.4 1.1 1.6

80-m Surface 8.1 8.9 8.3 7.9 80-m Surface 2.8 3.1 1.3 1.1 Bottom 3.7 2.5 4.2 6.1 Bottom 0.6 0.6 0.3 0.7

98-m Surface 8.1 8.7 8.2 7.8 98-m Surface 3.1 3.6 1.4 1.0 Bottom 3.3 2.4 3.6 5.6 Bottom 0.4 0.5 0.2 0.4

PLOOOceanCond2008.indd 15 6/29/2009 2:47:12 PM La Jolla January LaLa JollJoll a a April

F36 F25 F14 F03 F36 F25 F14 F03 ! ! ! ! ! ! ! ! F35 F24 F13 F35 F24 F13 ! F02 ! F02 ! ! ! ! ! iver ! ego Riivverer F12 go R San DiDi ego R F34 F23 San Die F34 F23 F12 San ! San Diego ! SaSan Diego ! ! a ! ! F33 F22 F11 F33 F22 F11 Lom ! ! ! Loma ! ! F21 o Ba ! F21 Ba i eg y i ego y F32 F10 D F32 F10 D n oint Loma n a Point a ! P o i n t S ! P S F31 ! F31 ! ! F20 ! F20 Coronado CoCorronad o n a doo F09 F09

! ! ! ! ! ! a Lom a F19 Point F19 Point Lom F30 l F30 ! Outfal ! Outfall ! ! ! ! F08 10 m F08 F18 F07 F18 F07 10 m ! ! ! ! F29 ! F29 ! F01 F01 F06 ! F06 ! F28 F17 F28 F17 ! 20 m ! 20 m ! ! ! !

O F05 Depth (m) Temperature ( C) F05 ! ! F16 ! ! ! F16 ! F27 1 9.0- 11.0 F27 F04 25(12*) 11.1- 13.0 F04 60(18*) ! ! ! 13.1- 15.0 ! ! ! 80 F15 15.1-17.0 F15 m F26 98 F26 17.1-19.0

100m 4 10 0 60 m 4 60 m 150 m 80 19.1-21.0 150 m 8 0 m km *F01, F02, F03 km m 012345 21.1-23.0 m 012345 LaLa JollaJolla July La Jolla October

F36 F25 F14 F03 F36 F25 F14 F03 ! ! ! ! ! ! ! ! F35 F24 F13 F35 F24 F13 ! ! F02 F02 ! ! ! r ! ! go River ! iver San Dieego Ri F12 Diego R F34 F23 F12 San Di F34 F23 San ! San Diego ! San Diego ! ! ! !

F33 F22 F11 ma F33 F22 F11

! ! ! ! ! F21 Ba ! F21 o B a i eg o y i eg y F32 F10 D F32 F10 D oint Lo n n Point Loma a a ! P S ! Point Loma S F31 ! F31 ! ! F20 ! F20 CoCoronador o n a d o Coronado F09 F09

! ! ! ! ! ! a Lom Loma F30 F19 Point F30 F19 Point l ! Outfall ! Outfa l ! ! ! ! F08 10 m F08 10 m F18 F07 F18 F07 ! ! ! ! F29 ! F29 ! F01 F01 F06 ! F06 ! F28 F17 F28 F17 ! ! ! 20 m ! ! 20 ! m F05 F05 ! ! F16 ! ! ! F16 ! F27 F27 F04 F04 ! ! ! ! ! ! F15 F15 m F26 F26

100m 100 m

60 m 4 60 m 1 80 m 4 80 m 50 150 m km m km 012345 012345 Figure 2.3 Seawater temperatures during quarterly surveys at the offshore PLOO stations in 2008. For each station, data are limited to the discrete depths at which bacterial samples are collected (see Chapter 3).

PLOOOceanCond2008.indd 16 6/29/2009 2:47:13 PM 24 Surface 20 Bottom 16 (°C) (°C) 12 Temperature 8

33.8 33.6 (ppt) (ppt) Salinity 33.4 33.2 10

DO 6 (mg/L) (mg/L)

4 8.4

8.2

pH 8.0

7.8 90 85 80 (%) (%) 75

Transmissivity 70

a 12

8 g/L) g/L) P ( 4 Chlorophyll Chlorophyll 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Month Figure 2.4 Monthly mean temperature, salinity, dissolved oxygen (DO), pH, transmissivity, and chlorophyll a. values for surface (≤2m) and bottom (10–20 m) waters at the Point Loma kelp stations during 2008.

(Appendix A.1). For example, transmissivity Transmissivity averaged between about 59 and 90% over all depths Transmissivity values were within historical ranges during the year (Table 2.1). Additionally, water in the PLOO region during 2008 and there were no clarity was consistently greater at the offshore apparent patterns relative to wastewater discharge stations when compared to inshore stations by as

PLOOOceanCond2008.indd 17 6/29/2009 2:47:18 PM La Jolla January LaLa J o ll l l a a April

F36 F25 F14 F03 F36 F25 F14 F03 ! ! ! ! ! ! ! ! F35 F24 F13 F35 F24 F13 ! F02 ! ! ! F02 ! ! ! River ! ver F12 n Diego ego Riv F34 F23 Sa F34 F23 F12 SaSann Di ! San Diego ! SaSann DiegoDiego ! ! ! ! F33 F22 F11 F33 F22 F11 oma ! ! Lom a ! L ! ! ! t F21 g o B ay F21 go Ba y i e int Loma i e F32 F10 i n t D F32 F10 in D n n a a ! Po S ! PoPo S F31 ! F31 ! ! F20 ! F20 Coronado CoCoronaronad o F09 F09

! ! ! ! ! ! a Lom Loma F30 F19 Point F30 F19 Point all l ! Outf ! Outfal ! ! ! ! F08 10 m F08 10 m F18 F07 F18 F07 ! ! ! ! F29 ! F29 ! F01 F01 F06 ! F06 ! F28 F17 F28 F17 ! 20 m ! 20 m ! ! ! !

F05 Depth (m) Salinity (ppt) F05 ! ! F16 ! ! ! F16 ! F27 1 -33.00 F27 F04 25(12*) 33.01-33.30 F04 60(18*) ! ! ! 33.31-33.60 ! ! ! 80 F15 33.61-33.90 F15 98 F26 33.91-34.20 F26

1 100 m 60 m

4 60 m 00 m 4 1 80 m 150 80 m 50 m *F01, F02, F03 km m km 012345 012345 La Jolla July LaLa JollaJolla October

F36 F25 F14 F03 F36 F25 F14 F03 ! ! ! ! ! ! ! ! F35 F24 F13 F35 F24 F13 ! F02 ! F02 ! ! ! ! ! River ! o Riverver F12 n Diego n DiDieg ego Ri F34 F23 Sa F34 F23 F12 SaSan ! San Diego ! Sann DiegoDiego ! ! ! ! a a F33 F22 F11 ma F33 F22 F11 om ! ! ! ! L ! ! t F21 eg o Ba y F21 g o Ba y int Lo i i e F32 F10 D F32 F10 D n n P o a a F31 ! S ! Poin S ! F31 ! ! F20 ! F20 Point Lom Coronado CoCoronaronad do o F09 F09

! ! ! ! ! ! a Loma Lom F30 F19 Point F30 F19 Point ! tfall all Ou ! Outf ! ! ! ! F08 F07 10 F08 10 m F18 m F18 F07 ! ! ! F29 ! F29 ! ! F01 F01 F28 F06 ! F06 ! F17 F28 F17 20 m ! ! ! ! 20 m ! !

F05 F05 ! ! F16 ! ! ! F16 ! F27 F27 F04 F04 ! ! ! ! ! ! F15 F15 F26 m F26 4 1

60 m 4 00 m 100 150 m 80 m 60 m 1 80 m km km 50 m 012345 m 012345

Figure 2.5 Salinity concentrations during quarterly surveys at the offshore PLOO stations in 2008. For each station, data are limited to the discrete depths at which bacterial samples are collected (see Chapter 3).

PLOOOceanCond2008.indd 18 6/29/2009 2:47:19 PM much as 20% at the surface and 30% at the bottom. depths below 60 m. These spring conditions suggest Lower transmissivity values in January along the the presence of upwelled water that is typical of this 10-m and 20-m depth contours were likely due season (Jackson 1986; see also discussion above). to storm and wave activity, while reductions in Values for most parameters were within historical water clarity in April co-occurred with peaks in ranges during the summer. The only exception was chlorophyll a values (i.e., phytoplankton blooms). transmissivity, which had values above normal at In fact, surface transmissivity values at the kelp bed mid-depths (i.e., between 25 and 60 m). In contrast, stations strongly reflect fl uctuations in chlorophyll a DO and pH values exceeded the upper end of the concentrations, which were relatively high in April historical range at depths around 40 m during the but peaked in June at these stations (Figure 2.4) fall survey, while transmissivity dropped below (see discussion below). the historical range near 30 m at this time. These unusual conditions during the fall may be due to Chlorophyll a very strong Santa Ana winds that took place during Mean chlorophyll a concentrations ranged from a the fi rst two weeks of October (J. Svejkovsky, low of 0.2 μg/L in bottom waters at the offshore personal communication). sites during July to a high of 8.7 μg/L at inshore surface waters in April (Table 2.1). Chlorophyll concentrations were fairly low at the offshore SUMMARY AND CONCLUSIONS stations throughout the year. In contrast, monthly averages at the kelp bed stations demonstrate that The Point Loma outfall region was characterized chlorophyll a concentrations were relatively high by relatively normal oceanographic conditions in this area during April, but were highest in June in 2008, which included localized upwelling and (Figure 2.4). Such spring blooms are likely related corresponding phytoplankton blooms in the spring. to upwelling events that typically occur during this Upwelling events were indicated by cooler than time of year (Jackson 1986). Unlike past years, normal water temperatures, especially at bottom no large plankton blooms were visible during the depths, and higher than normal salinity in April. The summer months in 2008 (e.g., see Svejkovsky 2009, presence of phytoplankton blooms was indicated City of San Diego 2008). by increased chlorophyll a concentrations during the spring, although these were not supported by Historical Assessment of remote sensing observations. Oceanographic Conditions There was no apparent relationship between the Water column profi les of temperature, salinity, DO, outfall and values of ocean temperature, salinity, pH, and transmissivity were analyzed for three pH, transmissivity, chlorophyll a, and dissolved nearfi eld stations (F29, F30, F31) sampled during oxygen during 2008. Instead, oceanographic the January (winter), April (spring), July (summer), conditions appeared to follow normal seasonal and October (fall) quarterly surveys in 2008, after patterns. For example, differences between surface which they were compared to historical profi les for and bottom waters (i.e., stratifi cation) were first 1991–2007 (Figure 2.6). Water temperatures were evident in the spring, were greatest during the fairly typical for the region throughout the year, summer, and then declined slightly in the fall. with values generally within the historical range Since temperature is the main contributor to water (i.e., mean ± one standard deviation) during each column stratifi cation in southern California, these survey. Only DO exceeded historical conditions differences between surface and bottom waters during the winter survey, with values well below were important in preventing the waste fi eld from the historical mean at depths of ≥60 m. During the surfacing. The restriction of elevated densities of spring survey, DO was below normal at most depths, fecal indicator bacteria to depths of 60 m or below while salinity was slightly higher than normal at also indicates that the wastewater plume remained

PLOOOceanCond2008.indd 19 6/29/2009 2:47:23 PM 2008 1991-2007 SD 0 January January

100

0 April April 20

100

Depth (m) 0 July July

100

0 October October

100

8 101214161820 22 32.8 33.2 33.6 34.034.4

Temperature (°C) Salinity (ppt) Figure 2.6 Water column temperature, salinity, dissolved oxygen, pH, and transmissivity profiles for 2008 compared to historical data for 1991–2007 at PLOO stations F29, F30, and F31. Data from 2008 are quarterly averages, whereas historical data represent 17-year means ± one standard deviation (SD); both are calculated for each month at 5-m depth intervals.

PLOOOceanCond2008.indd 20 6/29/2009 2:47:24 PM 2008 1991-2007 SD 0 January January January 20 40 60 80 100

0 April April April 20 40 60 80 100

0 July July July

Depth (m) 20 40 60 80 100

0 October October October

100

2 46 810 7.5 7.8 8.1 8.4 80 90 100

Dissolved Oxygen (mg/L) pH Transmissivity (%)

Figure 2.6 continued

PLOOOceanCond2008.indd 21 6/29/2009 2:47:24 PM trapped in relatively deep waters during the year Bradley, M. Weise, J. Harvey, C. Collins, (see Chapter 3). Moreover, the wastewater plume and N. Lo. (2007). The state of the California was not detectable in aerial imagery during 2008 Current, 2006–2007: Regional and local (Svejkovsky 2009). processes dominate. California Cooperative Oceanic Fisheries Investigations (CalCOFI) Oceanographic conditions for the SBOO region in Reports, 48: 33–66. 2008 remained notably consistent with long-term analysis of water column data collected between Jackson, G.A. (1986). Physical Oceanography of 1991 and 2007, which also did not reveal any changes the Southern California Bight. In: R. Eppley in oceanographic parameters near the PLOO that (ed.). Plankton Dynamics of the Southern could be attributed to wastewater discharge (see California Bight. Springer Verlag, New York. City of San Diego 2008). Instead, major changes p 13–52. in water temperatures and salinity off Point Loma region have generally corresponded to signiﬁcant Largier, J., L. Rasmussen, M. Carter, and C. climate events that occurred within the California Scearce. (2004). Consent Decree – Phase One Current System (e.g., Peterson et al. 2006; Study Final Report. Evaluation of the South Goericke et al. 2007, McClatchie et al. 2008). Bay International Wastewater Treatment Plant Additionally, transmissivity or water clarity has Receiving Water Quality Monitoring Program increased in the PLOO region over the past several to Determine Its Ability to Identify Source(s) years, and changes in pH and dissolved oxygen of Recorded Bacterial Exceedances. Scripps levels have not exhibited any apparent trends related Institution of Oceanography, University of to wastewater discharge. California, San Diego, CA.

McClatchie, S., R. Goericke, J.A. Koslow, F.B. LITERATURE CITED Schwing, S.J. Bograd, R. Charter, W. Watson, N. Lo, K. Hill, J. Gottschalck, M. l’Heureux, Bowden, K.F. (1975). Oceanic and Estuarine Y. Xue, W.T. Peterson, R. Emmett, Mixing Processes. In: J.P. Riley and G. Skirrow C. Collins, G. Gaxiola-Castro, R. Durazo, (eds.). Chemical Oceanography, 2nd Edition. M. Kahru, B.G. Mitchell, K.D. Hyrenbach, Academic Press, San Francisco. p 1–41. W.J. Sydeman, R.W. Bradley, P. Warzybok, and E. Bjorkstedt. (2008). The state of City of San Diego. (2008). Annual Receiving the California Current, 2007–2008: La Waters Monitoring Report for the Point Loma Niña conditions and their effects on the Ocean Outfall, 2007. City of San Diego Ocean ecosystem. California Cooperative Oceanic Monitoring Program, Metropolitan Wastewater Fisheries Investigations (CalCOFI) Reports, Department, Environmental Monitoring and 49: 39–76. Technical Services Division, San Diego, CA. NOAA/NWS. (2009a). The National Oceanic and Dailey, M.D., D.J. Reish, and J.W. Anderson, eds. Atmospheric Association and the National (1993). Ecology of the Southern California Weather Service Archive of Local Climate Bight: A Synthesis and Interpretation. Data for San Diego, CA. http://www.wrh. University of California Press, Berkeley, CA. noaa.gov/sgx/climate/san-san.htm.

Goericke, R., E. Venrick, T. Koslow, W.J. Sydeman, NOAA/NWS. (2009b). The National Oceanic and F.B. Schwing, S.J. Bograd, B. Peterson, Atmospheric Association, Online Weather R. Emmett, K.R. Lara Lara, G. Gaxiola- Data for San Diego, CA. http://www.weather. Castro, J.G. Valdez, K.D. Hyrenbach, R.W. gov/climate/xmacis.php?wfo=sgx.

PLOOOceanCond2008.indd 22 6/29/2009 2:47:25 PM Peterson, B., R. Emmett, R. Goericke, E. Venrick, A. Svejkovsky, J. (2009). Satellite and Aerial Coastal Mantyla, S.J. Bograd, F.B. Schwing, R. Hewitt, Water Quality Monitoring in the San Diego/ N. Lo, W. Watson, J. Barlow, M. Lowry, Tijuana Region: Annual Summary Report, S. Ralston, K.A. Forney, B.E. Lavaniegos, 1 January, 2008 – 31 December, 2008. Ocean W.J. Sydeman, D. Hyrenbach, R.W. Bradley, Imaging, Solana Beach, CA. P. Warzybok, F. Chavez, K. Hunter, S. Benson, M. Weise, J. Harvey, G. Gaxiola-Castro, and [SWRCB] California State Water Resources R. Durazo. (2006). The state of the California Control Board. (2001). California Ocean Plan, Current, 2005–2006: Warm in the north, Water Quality Control Plan, Ocean Waters cool in the south. California Cooperative of California. California Environmental Oceanic Fisheries Investigations (CalCOFI) Protection Agency. Sacramento, CA. Reports, 47: 30–74. Terrill, E., K. Sung Yong, L. Hazard, and M. Otero. Pickard, D.L. and W.J. Emery. (1990). Descriptive (2009). IBWC/Surfrider – Consent Decree Physical Oceanorgraphy. 5th Edition. Pergamon Final Report. Coastal Observations and Press, Oxford. Monitoring in South Bay San Diego. Scripps Institution of Oceanography, University of Skirrow, G. (1975). Chapter 9. The Dissolved Gases– California, San Diego, CA. Carbon Dioxide. In: Chemical Oceanography. J.P. Riley and G. Skirrow (eds.). Academic Press, London.

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