Coastal Circulation and Potential Coral-larval

Dispersal in Maunalua Bay, O‘ahu, Hawaii—

Measurements of Waves, Currents, Temperature, and 

Salinity, June–September 2010

By M. Katherine Presto, Curt D. Storlazzi, Joshua B. Logan, Thomas E. Reiss, and Kurt J. Rosenberger

Open-File Report 2012–1040

U.S. Department of the Interior

U.S. Geological Survey
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U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director 

U.S. Geological Survey, Reston, Virginia: 2012 

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Suggested citation:

Presto, M.K., Storlazzi, C.D., Logan, J.B., Reiss, T.E., and Rosenberger, K.J., 2012, Coastal circulation 

and potential coral-larval dispersal in Maunalua Bay, O‘ahu, Hawaii—Measurements of waves, currents, 

temperature, and salinity, June–September 2010: U.S. Geological Survey Open-File Report 2012-1040, 

67 p., available at http://pubs.usgs.gov/of/2012/1040/. 

COVER 

Left: Ph/oto of satellite-tracked Lagrangian surface drifter deployed in Maunalua Bay, O‘ahu

Right: Photo of Montipora Capitata, the coral studied in Maunalua Bay during its spawning season
ii

Contents

Abstract ..........................................................................................................................................................1

Introuction ......................................................................................................................................................1

Project Objectives.......................................................................................................................................2

Study Area..................................................................................................................................................2

Operations .....................................................................................................................................................3

Research Platform and Field Operations....................................................................................................3

Equipment and Data Review......................................................................................................................3

Data Acquisition and Quality ..........................................................................................................................5

Results ...........................................................................................................................................................5

General Meteorology..................................................................................................................................5

Tides...........................................................................................................................................................5

Waves ........................................................................................................................................................6

Currents......................................................................................................................................................6

Temporal Variations of Water-column Properties.......................................................................................6

Spatial Variations in Water-column Properties ...........................................................................................7

Spatial Variations in Currents .....................................................................................................................7

Discussion ......................................................................................................................................................8

Meteorologic and Oceanographic Forcing During the 2010 Summer Coral-Spawning Season..................8

Temporal and Spatial Variability in Temperature and Salinity During the 2010 Summer CoralSpawning Season................................................................................................................................9

Circulation and Potential Coral-larval Dispersal During the 2010 Summer Coral-Spawning Season .........9

Summary......................................................................................................................................................12

Acknowledgments........................................................................................................................................12

References Cited .........................................................................................................................................13

Additional Digital Information........................................................................................................................13

Direct Contact Information ...........................................................................................................................14

Appendixes ..................................................................................................................................................33

Appendix 1. Acoustic Doppler Current Profiler (ADCP) Information .........................................................33

Appendix 2. Conductivity and Temperature (CT) Information...................................................................35

Appendix 3. Weather Station (WS) Information........................................................................................35

Appendix 4. Water-Column Profiler (WCP) Information............................................................................35

Appendix 5. Water-Column Profiler (WCP) log, June 2010 ......................................................................36

Appendix 6. Time-series Plots of Variations in Water Level, Wave Heights, Wave Periods, and Wave 

Directions from Acoustic Doppler Current Profilers (ADCPs) in Maunalua Bay for 2010 Year 

Days 170–250 (June 19–September 7) .............................................................................................38

Appendix 7. Time-Series Plots of Variations In Water Level, Currents, and Temperature from 

Acoustic Doppler Current Profilers (ADCPs) in Maunalua Bay for 2010 Year Days 170–250 

(June 19–September 7) .....................................................................................................................41

Appendix 8. Time-Series Plots of Variations in Temperature and Salinity from 

Conductivity/Temperature (CT) Sensors in Maunalua Bay for 2010 Year Days 170–250 (June 

19–September 7) ...............................................................................................................................44

Appendix 9. Maps Showing the Spatial Variability in Temperature and Salinity from Water-Column 

Profiler (WCP) Casts in Maunalua Bay ..............................................................................................50
iii

Appendix 10. Maps Showing the Spatial Variability in Near-Surface Current Speeds and Directions 

from Vessel-Mounted Acoustic Doppler Current-profiler (VM-ADCP) Surveys in Maunalua Bay ...... 58

Appendix 11. Maps and Time-Series Plots of Lagrangian Surface-Drifter Deployments in Maunalua 

Bay ..................................................................................................................................................... 62

Figures

1. A, Aerial photograph and scanning hydrographic operational airborne lidar surveys (SHOALS) 

bathymetric map of Maunalua Bay and its location on O‘ahu, Hawaii. Also shown are the location 

of instrument packages and major landmarks. B, Vessel-mounted acoustic Doppler current-profiler 

(VM-ADCP) tracklines and water-column Profiler (WCP) cast locations are denoted by italic white 

numbers and numbers in dots, respectively........................................................................................... 21

2. A–C, Photographs of the equipment used in Maunalua Bay during the 2010 summer experiment. A, 

Underwater photograph of a MiniProbe with an acoustic Doppler current profiler (ADCP) and a 

conductivity and temperature (CT) sensor along the 10-m isobath at the Paikō 10-m site. B, Watercolumn Profiler (WCP). C, Example of a Lagrangian surface drifter in the ocean taken from the R/V 

Alyce C. D, Example of the coral, Montipora capitata, the spawning of which was the focus of the 

2010 summer experiment. ..................................................................................................................... 22

3. Time-series plot of meteorologic and oceanographic forcing in Maunalua Bay during the 2010 

summer experiment. A, Barometric pressure, in millibars. B, Air temperature, in degrees Celsius. 

C, Wind speed, in meters per seconds, with average wind speed in blue and peak wind speed in 

red. D, Wind speed and direction, in meters per second from true north. E, Half-hour rainfall (blue) 

and cumulative rainfall (red), in millimeters. F, Tidal height, in meters. G, Average (blue) and peak 

(red) wave height, in meters. ................................................................................................................. 23

4. Map showing the mean (blue vectors) and variability (red ellipses) in wave heights and directions, in 

meters from true north, in Maunalua Bay during the 2010 summer experiment for the Diamond 

Head 20-m, Wailupe 20-m, and Paikō 10-m sites. ................................................................................ 24

5. Map showing the mean (vectors) and variability (ellipses) in current speeds and directions, in meters 

per second from true north, in Maunalua Bay for the 2010 summer experiment. ................................. 25

6. Scatter plot showing the relationship between water temperature, in degrees Celsius, and salinity, in 

Practical Salinity Units (PSU) along the cross-shore transect off Paikō from 5-m to 30-m water 

depth. .................................................................................................................................................... 26

7. Map showing the spatial variability in temperature, in degrees Celsius, averaged from water-column 

Profiler (WCP) surveys in Maunalua Bay made during the June 12–15 (2010 Year Days 162-166) 

coral-spawning period.. A, Averaged data from 1 m below the surface. B, Averaged data from 1 m 

above the seabed. The near-surface temperature data show very uniform temperature throughout 

the bay, with slightly warmer temperatures close to shore on the western side of the bay. .................. 27

8. Map showing the spatial variability in salinity, in Practical Salinity Units (PSU), from the watercolumn Profiler (WCP) surveys in Maunalua Bay averaged over the 4 days of the June 12–15 

(2010 Year Days 162-166) coral-spawning period. A, Averaged data from 1 m below the surface. 

B, Averaged data from 1 m above the seabed. The near-surface salinity was fairly uniform 

throughout the bay, with the highest salinity values observed close to shore, possibly because of 

evaporation. .......................................................................................................................................... 28

9. Map showing of mean current speeds and directions (arrows) and variability (ellipses), in meters per 

second from true north, for the vessel-mounted acoustic Doppler current-profiler (VM-ADCP) data 

from surveys made during the June 12–15 (2010 Year Days 162-166) coral-spawning period, 

averaged at 400 m intervals along each VM-ADCP survey line. ........................................................... 29
iv

10. Map showing the areal extent of satellite drifters released from 4 locations (A-D) in Maunalua Bay 

over three nights June 12–15 (2010 Year Days 163–165) in Maunalua Bay following predicted 

times of coral-spawning in an attempt to track potential coral-larval dispersal. A, Inshore location on 

the east side of the bay near Hawai‘i Kai harbor. B, Mid-shore location on the east side of the bay 

near Koko Head. C, Inshore location near Wailupe Peninsula. D, Offshore location near Koko 

Head. ....................................................................................................................................................30

11. Time-series plots showing the vertical variation in acoustic Doppler current profiler (ADCP) 

acoustic backscatter data before, during, and after the 2010 summer predicted coral-spawning 

periods in Maunalua Bay and tide data from the Paikō 10-m site. A, Data from the June spawning 

period (2010 Year Days 162–166). B, Data from the July spawning period (2010 Year Days 191–

195). C, Data from the August spawning period (2010 Year Days 221–225). D, Data from the 

September spawning period (2010 Year-Days 250–254). ....................................................................31

12. Map showing the areal extent of potential coral-larval dispersal (Storlazzi and others, 2006) from 

the Diamond Head 20-m (green), Wailupe 20-m (blue), and Paikō 10-m (red) sites during the 2010 

summer predicted coral-spawning events in June, July, August, and September in Maunalua Bay. ....32

Tables

1. Experiment personnel. ............................................................................................................................15

2.. Instrument package sensors and location information. ..........................................................................15

3. Instrument package location information.................................................................................................15

4. Water-column profiler (WCP) cast location and depth information..........................................................16

5. Vessel-mounted acoustic Doppler current profiler (VM-ADCP) log information.......................................17

6. Lagrangian surface-drifter log information...............................................................................................18

7. Meteorological statistics. .........................................................................................................................18

8. Wave statistics. .......................................................................................................................................18

9. Current statistics. ....................................................................................................................................19

10. Water temperature statistics..................................................................................................................19

11. Salinity statistics....................................................................................................................................19

12. Lagrangian surface-drifter statistics. .....................................................................................................20
Coastal Circulation and Potential Coral-larval

Dispersal in Maunalua Bay, O‘ahu, Hawaii—

Measurements of Waves, Currents, Temperature, and 

Salinity, June–September 2010

By M. Katherine Presto, Curt D. Storlazzi, Joshua B. Logan, Thomas E. Reiss, and Kurt J. Rosenberger

Abstract

This report presents a summary of fieldwork conducted in Maunalua Bay, O‘ahu, Hawaii

to address coral-larval dispersal and recruitment from June through September, 2010. The 

objectives of this study were to understand the temporal and spatial variations in currents, waves, 

tides, temperature, and salinity in Maunalua Bay during the summer coral-spawning season of 

Montipora capitata. Short-term vessel surveys and satellite-tracked drifters were deployed to 

measure currents during the June 2010 spawning event and to supplement the longer-term 

measurements of currents and water-column properties by fixed, bottom-mounted instruments 

deployed in Maunalua Bay. These data show that currents at the surface and just below the 

surface where coral larvae are found are often oriented in opposite directions due primarily to 

tidal and trade-winds forcing as the primary mechanisms of circulation in the bay. These data 

extend our understanding of coral-larvae dispersal patterns due to tidal and wind-driven currents 

and may be applicable to larvae of other Hawaiian corals. 

Introduction

Coral recruitment is low in Maunalua Bay, O‘ahu, Hawaii, but it is not clear whether this 

is due to a low supply of coral larvae in the bay or to anthropogenic stressors that impair 

recruitment success. To help resolve this question, a multi-partner (University of Hawai‘i, 

Mālama Maunalua, U.S. Coral Reef Task Force, and the U.S. Geological Survey) experiment 

investigated coral spawning and larval recruitment during summer 2010 in Maunalua Bay. This 

study focused on the coral species Montipora capitata, because it is one of the major reef 

builders along the coastline of the bay and the egg-sperm bundles are large enough (0.95–1.05 

mm; Mate and others, 1998) to be seen with the naked eye, allowing visual identification of both 

the initiation and cessation of spawning. The peak spawning periods for this species are during

summer new moons between 20:00 and 22:00 local/Hawaiian Standard Time (HST) (Heyward, 

1986; Kolinski and Cox, 2003). In the summer of 2010, this placed the beginning of spawning at 

or about the evening of Saturday, June 12. Spawning lasted for approximately three to four 

nights and reoccurred during the new moons in July, August, and September, 2010. 

As part of this experiment, the general hydrography and circulation of Maunalua Bay 

during summer spawning conditions were measured, complementing a dataset collected during 

the 2008–2009 winter (Storlazzi and others, 2010). This effort included deploying satellite-
2

tracked differential Global Positioning System (GPS) drifters in coral larvae slicks to track the 

movement of the buoyant coral larvae and determine if they were transported into, retained in, or 

dispersed out of Maunalua Bay. Surveys of currents and water-column properties were 

conducted before, during, and after the June 2010 spawning event to provide information on the 

general hydrography of the bay during summer conditions and to identify the presence of eddies 

or shear zones in the bay that might help to retain larvae, sediment, nutrients, or contaminants. 

These relatively short-duration vessel surveys were supplemented by longer-term measurements 

of currents and water-column properties from instruments deployed at a number of fixed stations 

in the bay from June through September 2010. Both the vessel surveys in June and the longerterm fixed stations deployed from June through September used acoustic Doppler current 

profilers (ADCPs). The acoustic backscatter data from these instruments have been shown 

(Storlazzi and others, 2006) to be useful for imaging M. capitata egg-sperm bundles and 

quantifying the relative intensity of spawning events in Hawaii. Collectively, the combination of 

mobile vessel surveys and fixed instrument deployments allowed us to determine whether the 

flow patterns and spawning intensity observed in the intensive June surveys were representative 

for the full June through September M. capitata spawning season. 

Project Objectives 

The objective of this study was to understand the temporal variations in currents, waves, 

tides, temperature, and salinity in Maunalua Bay during the summer coral-spawning season. To 

characterize the spatial variability in the physical oceanographic processes surrounding coralspawning sites, three datasets were collected: (1) a vessel-mounted acoustic Doppler current 

profiler (VM-ADCP) was used to map current velocities throughout the bay during the 4 days 

following coral-spawning events; (2) vertical profiles of water-column properties, including 

salinity, temperature, and turbidity, were measured throughout the bay during the same period; 

and (3) Lagrangian surface drifters were released in Maunalua Bay at night during the coralspawning events to map the potential drift of coral larvae in the initial hours following release 

into the water column. To place these short-term, spatially distributed measurements into a 

longer time-scale context, bottom mounted oceanographic instruments were deployed for the 3-

month period (June–September, 2010) following the spatial surveys. The combination of these 

spatially and temporally distributed measurements provide insight into the potential fate of 

terrestrial sediment, nutrient, or contaminant delivery and coral-larval transport within the 

embayment. Such information is useful for providing baseline information for future watershed 

decisions and for establishing guidelines for the U.S. Coral Reef Task Force’s (USCRTF) 

Hawaiian Local Action Strategy to address land-based pollution (LAS-LBP) threats to coral reefs 

in the Maunalua ahupua‘a (linked watershed-reef system). These measurements support the 

ongoing process studies being conducted as part of the U.S. Geological Survey (USGS) Coastal 

and Marine Geology Program’s Pacific Coral Reef Project; the ultimate goal is to better 

understand the transport mechanisms of sediment, larvae, nutrients, contaminants, and other 

particles in coral reef settings.

Study Area

Spatial and temporal measurements of meteorologic and oceanographic data were made 

during the 2010 summer in Maunalua Bay, on the south side of O‘ahu, Hawaii (fig. 1A,B). The 

bay, which is approximately 10 km long and 3 km wide, is flanked by two dormant volcanic 

craters, Koko Head to the east and Diamond Head to the west. Rainfall in the watersheds that 

drain into Maunalua Bay, which primarily occurs in the winter months, ranges from more than 
3

200 cm/year at the top of the Ko‘olau Range that borders the northwestern part of the bay to less 

than 70 cm/year to the east at Koko Head. 

Operations

This section provides information about the personnel, equipment, and field operations 

used during the study. See table 1 for a list of personnel involved in the experiment and tables 2 

through 12 for complete listings of instrument and deployment information and statistical data 

summaries.

The study used three suites of instruments to provide an integrated understanding of 

circulation and potential coral-larval dynamics in Maunalua Bay: a weather station, bottommounted time-series oceanographic instrument packages, and spatial oceanographic-survey 

instruments. The weather station was deployed on top of the Mt. Terrace Condominiums in 

Hawai‘i Kai to quantify meteorologic forcing that might influence circulation and water-column 

properties in Maunalua Bay. Bottom-mounted oceanographic instrument packages were 

deployed along the 20-m isobaths at the western (off Diamond Head) and central part of the bay 

(off the Wailupe Peninsula), as well as in a cross-shore array on the eastern side of the bay off 

Paikō Lagoon. This cross-shore array included bottom-mounted oceanographic instrument 

packages on the 10-m and 20-m isobaths and moorings on the 5-m and 30-m isobaths. 

In addition to fixed, bottom-mounted, time-series measurements, intensive spatial surveys 

of currents and water-column properties were made in the bay over a 4-day period, June 12–15, 

2010 (2010 Year Days [YD] 163–166), when coral-spawning was predicted to occur (fig. 1B). 

All vessel operations involving oceanographic instrumentation and spatial surveys, 

including mobilization and demobilization, were based out of the Ala Wai Boat Harbor

approximately 5 km to the east of Maunalua Bay, and all instrument packages were situated on 

the sandy seabed in water depths less than 30 m. Night dives to verify coral spawning were 

based out of Hawai‘i Kai Harbor, located in the northeast corner of Maunalua Bay. 

Research Platform and Field Operations

Instrument deployments and recoveries were conducted using the F/V Alyce C. Watercolumn profiler casts were conducted from the vessel using a hand line. A differential-equipped 

GPS compass was mounted on the F/V Alyce C. to provide accurate position and heading 

information for the vessel-mounted current-profiler data-acquisition and processing system. The 

driver’s station was outfitted with a laptop computer and GPS-enabled navigation system to 

provide the vessel captain with a graphic display of position information, speed, heading, and 

distance to the next location. The Lagrangian surface drifters were deployed over reefs each 

night from the D/V Sea Fox, following the predicted coral spawning; the F/V Alyce C. and the 

D/V Leila were used to recover the drifters.

Equipment and Data Review

Acoustic Doppler Current Profilers—Four upward-looking acoustic Doppler current 

profilers (ADCP) were mounted on stainless steel platforms called MiniPROBE instrument 

packages (fig. 2A) along the 10-m and 20-m isobaths in Maunalua Bay. These ADCPs measured 

currents at 2 Hz for 150 s every 5 min, in 1.0-m bins from 1.0 m above the seabed up to the 

surface. These data allow calculation of tides (m), mean current speeds (m/s), mean current 

directions (degrees true north), and higher frequency motions such as internal tidal bores and 

nonlinear internal waves. Directional wave data were recorded at 2 Hz for 1,024 s every 2 hours; 

these data allow calculation of significant wave height (m), dominant wave period (s), and mean 
4

wave direction (degrees true north). Acoustic backscatter data (dB) collected from the ADCPs 

during the current measurements provide information on particulates in the water-column and are 

used as a qualitative measurement of coral-larvae abundance. Instrument package locations are 

listed in table 3; complete sensor and processing information is listed in appendix 1.

Conductivity and Temperature Sensors—Six conductivity and temperature (CT) sensors 

(fig. 2A) collected and averaged 4 samples every 5 minutes to measure water temperature (°C) 

and conductivity (S/m), from which salinity (Practical Salinity Units, PSU) was calculated. The 

rapid sampling rate was used to facilitate identification of transient freshwater plumes generated 

by surface runoff and (or) submarine groundwater discharge being advected past the instruments. 

Two additional conductivity and temperature sensors collected and averaged four samples every 

1 minute at the base of the moorings on the 5-m and 30-m isobaths to examine the propagation of 

internal waves from deeper ocean water into the shallow part of the bay. The sensor locations are 

listed in table 3; complete sensor and processing information is listed in appendix 2. 

Weather Station (WS)—Meteorological data were acquired by a self-contained weather 

station (WS) deployed on top of the Mt. Terrace Condominiums, approximately 71 m above sea 

level, in the northeast corner of the bay (fig. 1A). The WS recorded 25 minutes averages of 

barometric pressure (mb), air temperature (°C), precipitation (mm), wind speed (m/s), and wind 

direction (degrees true north) every 30 minutes. The station location is listed in table 3; complete 

sensor information is listed in appendix 3. 

Water-Column Profiler (WCP)—Depth profiles of water properties were obtained using a 

water-column profiler (WCP) (fig. 2B) with conductivity, temperature, depth, optical 

backscatter, light transmission, and chlorophyll sensors. The profile surveys were conducted over 

4 days (June 12–15, 2010) between Koko Head and Diamond Head craters at the beginning and 

end of each vessel-mounted acoustic Doppler current profiler survey line. Profile locations and 

depth information are listed in table 4; complete sensor information and individual cast 

acquisition logs are listed in appendixes 4–5. 

Vessel-Mounted Acoustic Doppler Current Profiler—Hydrographic surveys of current 

speeds and directions, along with acoustic backscatter, throughout the water-column were 

conducted using a downward-looking 600 kHz vessel-mounted acoustic Doppler current profiler 

(VM-ADCP) mounted to the starboard side of the R/V Alyce C. The data were collected in 1 m 

bins from the surface down to the seabed every second and averaged every 30 s. Bottom tracking 

by the VM-ADCP and a boat-mounted differential GPS (DGPS) and digital compass were used 

to accurately determine the location, magnitude, and direction of the currents throughout the 

water-column. Data were collected along approximately 7 cross-shore and 5 alongshore transects 

between Diamond Head and Koko Head (fig. 1B) each day from June 12 through 15, 2010 (YD 

163–166). Both the order and start and end location of each survey transect were reversed each 

day to minimize the influence of tidal stage and diurnal sea-breeze forcing.

Lagrangian Surface Drifters—Satellite-tracked, DGPS, Lagrangian surface drifters were 

deployed each night during coral spawning (June 12–15, 2010, YD 163–165) to track surface (1 

m below the surface) currents (fig. 2C). The drifters logged their location internally every 1 

minute and transmitted their positions to Iridium satellites every 5 minutes. Two drifters were 

released each night, one from the 10 m MiniProbe site where night dives were conducted to 

verify spawning of M. capitata (fig. 2D) and the second from a different location in the bay to 

provide additional spatial information on the surface currents. The drifters were recovered the 

following day by boat, refurbished, and prepared for release the following evening. 
5

Miscellaneous Data Sources—Navigation equipment for deployment, recovery, and 

survey operations included a hand-held wide area augmentation system (WAAS)-equipped 

DGPS unit and a computer with positioning and mapping software. The positioning and mapping 

software enabled real-time DGPS position data to be combined with data from previously 

collected high-resolution scanning hydrographic operational airborne lidar surveys (SHOALS), 

bathymetry, 5-m isobaths, and aerial photographs. 

Data Acquisition and Quality

Data were acquired for 98 days during the period between June 12 and September 13, 

2010 (YD 163–256). More than 2 million data points were recorded by the ADCPs, CTs, and 

WS; more than 8,000 data points were recorded by the WCP and 0.5 million data points by the 

VM-ADCP. The raw data were archived, and copies of the data were post-processed for analysis.

The ADCP, CT, and WS data generally appeared to be of high quality. The ADCP at the 

Wailupe 20-m site had a malfunctioning pressure sensor for the first 60 days, rendering the tide 

and wave data unusable during that period. The instrument package at the Paikō 20-m site tilted 

and was eventually buried by sand at the beginning of the deployment, likely due to strong 

currents. This rendered the ADCP data unusable and reduced the quality of the CT data at this 

location. The WCP data were very high in quality, with spurious surface data removed during 

processing. The VM-ADCP data were also very high in quality, and any spurious data were 

removed during processing.

Results

This section reviews the data collected by the instruments during the deployments and 

addresses the significance of the findings to better understand the oceanographic conditions in 

the study area.

General Meteorology

The study period from 2010 YD 163–256 covered the dry, summer, trade-wind season in 

Hawaii (fig. 3). Precipitation ranged from 0.0 to 2.5 mm, with a mean rainfall ± one standard 

deviation of 0.01±0.1 mm (fig. 3E). The greatest amounts of rainfall occurred between days 2010 

YD 213–218, days which coincided with low barometric pressure and cooler air temperatures 

(fig. 3E,F). The air temperature ranged from 21.19o to 29.19oC, with a mean temperature ± one 

standard deviation of 24.99±1.55oC (fig. 3B). Daily heating/cooling on the order of 1 to 2oC was 

observed, with a slight warming trend over the course of the deployment. The mean wind speeds 

at the weather station (WS) ranged from 1.62 m/s to 11.81 m/s (fig. 3C), with a mean speed ± 

one standard deviation of 6.28±1.52 m/s during the deployment. The mean wind direction ± one 

standard deviation during the deployment was 78.69±10.13° (table 7). Winds mainly from the 

east were classified as “trade winds” and were associated with dry, stable weather with low 

rainfall; this type of forcing characterized approximately 90 percent of the study period (fig. 

3C,D).

Tides

The study period encompassed seven complete spring-neap tidal cycles (fig. 3F). The 

tides in Maunalua Bay are typical for the Hawaiian Islands: microtidal, mixed, semidiurnal with 

two uneven high tides and two uneven low tides per day. As a result, the interval between 

successive low and high tides was just every 6 hours. The mean daily tidal range was 
6

approximately 0.6 m, whereas the minimum and maximum daily tidal ranges were 0.4 m and 1.0 

m during neap and spring tides, respectively. 

Waves

Significant wave heights ranged from 0.17 m at the Paikō 10-m site to 1.91 m at the 

Diamond Head 20-m site, with a mean significant height ± one standard deviation of 0.87±0.23 

m for all of the sites (table 8). Dominant wave periods varied from 3.0 s at Wailupe 20-m site to 

14.1 s at the Diamond Head 20-m site, with a mean dominant period ± one standard deviation of 

6.9±1.1 s for all the sites. The mean wave direction ± one standard deviation for all the sites was 

185.1±15.9° (table 8). The waves measured at all of the sites were consistently from the south, 

most likely generated by the strong easterly trade winds and refraction into the bay (fig. 3G). The 

largest wave heights were measured between 2010 YD 212–218. This wave event was associated 

with strong winds, rainfall, and cooler temperatures, indicating that the event was most likely 

generated locally from the passage of a low-pressure system (fig. 3, shaded area). Appendixes 

6.1—6.3 show all of the time-series wave data for the Diamond Head 20-m, Wailupe 20-m, and 

Paikō 10-m sites. 

Currents

The mean current speed at the Paikō 10-m site was 0.04±0.06 m/s close to the surface and 

0.03±0.03 m/s close to the seabed (table 9). The mean current speeds ± one standard deviation at 

the Wailupe 20-m and Diamond Head 20-m sites were 0.08±0.20 m/s close to the surface and 

0.05±0.15 m/s close to the seabed (table 9), this was approximately two times greater than those 

close to the surface at the Paikō 10-m site and approximately four times greater than those near 

to the bed at the Paikō 10-m site. Appendixes 7.1–7.3 show the time-series data for the Diamond 

Head 20-m, Wailupe-20 m, and Paikō 10-m sites for near-surface, mid-water-column, and nearseabed currents. 

Temporal Variations of Water-column Properties

The water-column properties that were measured by the CTs included variations in 

temperature (oC), salinity (PSU). These measurements were made to address the temporal 

variability in water-column properties during the summer coral-spawning period and to provide 

additional information about the physical controls on the Maunalua Bay’s hydrography.

Temperature—Water temperatures at the monitored sites ranged between 22.96° and 

26.79°C, with a mean temperature ± one standard deviation of 25.10±0.40°C (table 10), with the 

coolest temperature measured at the Paikō 30-m site and the warmest temperature measured at 

the Paikō 5-m site. The daily variations in temperature at all of the sites appear to be controlled 

by daily insolation-driven heating and cooling of 1–2°C (appendixes 8.1A–8.6A). The seasonal 

signal showed a slight warming trend from June through September. Significant decreases in 

temperature were observed at the deep (>20 m) sites, which may be the result of internal waves 

advecting deeper, cooler water up into the shallow parts of the bay; the occurrence of these 

features appears to be related to the tidal cycle.

Salinity—Salinity at the monitored sites ranged between 28.22 and 35.82 PSU, with a 

mean salinity ± one standard deviation of 34.83±0.31 PSU (table 11). The lowest salinity was at 

the Paikō 10-m site and the highest salinity was at the Paikō 30-m site. The salinity at the sites 

along the 20-m isobath had fairly constant salinity values of about 35 PSU but showed decreases 

following periods of rainfall (for example, 2010 YD 210–220), suggesting these sites may be 

influenced by submarine freshwater discharge (appendixes 8.1B–8.2B). The Paikō 5-m and 10-m 

sites may be influenced by surface freshwater input from streams and the Hawai‘i Kai harbor 
7

following rainfall, as occurred during 2010 YD 210–220 (appendixes 8.3B–8.4B). The Paikō 30-

m site showed intermittent increases in salinity, which may be attributed to internal waves 

advecting deeper, cooler, more saline water up into the shallow parts of bay; these intermittent 

increases in salinity coincided with decreases in temperature (appendix 8.6B) 

Spatial Variations in Water-column Properties

Spatial variability of water-column properties in Maunalua Bay were characterized using 

the WCP on 2010 YD 163–166 (June 12–15, 2010), in conjunction with the VM-ADCP surveys. 

The WCP casts were conducted at the beginning and end of each line (fig. 1B); the start of the 

surveys alternated between the western and eastern parts of the bays each day. The mean for the 

top and bottom 1 m of the water-column for temperature and salinity, along with the mean and 

standard deviation for the entire water-column for each day, are shown in appendixes 9.1–9.8. 

Day-to-day differences in the near-surface and near-seabed temperature data probably are due 

mostly to the time of day when the water-column was profiled. For instance, the relatively high 

surface temperature values on 2010 YD 163 (June 12) and 165 (June 14) may simply be because 

the WCP casts on those days were made later in the day; the slightly higher temperatures at 

depth, especially in the shallow parts of the bay, may also be because of the timing of sampling 

during the day (appendixes 9.1–9.4). 

Water-column averaged salinity values were relatively consistent across the bay 

(appendixes 9.5–9.8). The near-surface salinity closer to shore was higher than offshore, possibly 

owing to evaporation; the near-bed salinity close to shore was also higher than offshore, possibly 

owing to greater submarine groundwater discharge at depth. An anomalously high salinity (0.5 

PSU greater than the surrounding points) was measured off Hawai‘i Kai harbor (appendixes 

9.5A, B–9.7A, B); later, the salinity off Hawai‘i Kai harbor was almost 0.5 PSU lower than the 

surrounding sites (appendixes 9.8A, B). The great variation at this site was most likely caused by 

tidal exchange and freshwater runoff from the Hawai‘i Kai harbor.

Spatial Variations in Currents

VM-ADCP Surveys—The daily VM-ADCP surveys are shown in appendix 10, and the 

times that each transect was surveyed are presented in table 5. Appendix 10.1 shows the nearsurface current speeds and directions on 2010 YD 163 (June 12). The survey started in the east 

side of the bay during a flooding tide. The currents were mainly to the east in the eastern side of 

the bay and shifted to the west near the middle part of the bay later in the day (appendix 10.1). 

The currents were strongest at the outer parts of the bay and weaker and more variable closer to 

shore. Appendix 10.2 shows near-surface current speeds and directions on 2010 YD 164 (June 

13); the currents began at the western side of the bay and continued east during a flood tide. The 

currents were consistently to the east and strongest offshore, with more variable currents close to 

shore near the Hawai‘i Kai harbor. The third day of surveys (2010 YD 165 [June 14]) started 

from the east side of the bay during slack to flooding tide (appendix 10.3). The currents on the 

eastern side of the bay were strongly to the east up to VM-ADCP survey line 12 (fig. 1B), with a 

transition at line 13, where the currents were strongly to the west for the rest of the survey. The 

fourth survey (2010 YD 166 [June 15]) began from the west side of the bay during slack low 

tide, as shown in appendix 10.4. The currents were consistently from the west throughout the bay 

and more variable closer to shore. 

Lagrangian Surface Drifters—Lagrangian surface drifters were deployed over three 

nights (2010 YD 163–165 [June 12–15]) in Maunalua Bay following the predicted times of 

coral-spawning in an attempt to track potential coral-larval dispersal. The start and stop dates, 
8

times, and locations of each drifter are listed in table 6. The drifters were designed so that they 

floated with the currents 1 m below the surface. Appendixes 11.1–11 .6 show the nightly drifter 

release and recovery locations, as well as timelines showing drifter velocity and direction 

through each deployment. Each plot also shows the wind velocity and the tidal regime during the 

deployment, with the gray shaded regions denoting nighttime. Statistics for the drifter 

deployments are shown in table 12. The drifters travelled primarily to the west after being 

released, but were influenced by both tidal and wind forcing. A maximum velocity of 1.09 m/s 

was measured by a drifter released at location B; this drifter also travelled the greatest net and 

total distance. The drifter released at location D travelled the least net distance, as it was caught 

in a series of small (on the order of ~100 m) eddies propagating back and forth around Koko 

Head.

Discussion

Meteorologic and Oceanographic Forcing During the 2010 Summer Coral-Spawning Season 

The deployment in Maunalua Bay took place from June to September 2010 during the 

summer trade-wind season in Hawaii, which is characterized by consistent winds from the 

northeast, minimal rainfall, and predominately southerly swells (fig. 3). Trade-wind conditions 

during this time period are defined as wind speeds greater than 4 m/s and wind directions 

between 45° and 135°; these conditions generally occur 90 percent of the time. The wave climate 

for the summer months is marked by trade-wind waves of less than 1 m and 5–7 s periods 

(Moberly and Chamberlain, 1964) with occasional larger and longer period swell from the south. 

Vectors showing the mean wave height and direction during the deployment for the Diamond 

Head 20-m, Wailupe 20-m, and Paikō 10-m sites are shown in figure 4. The waves impacting

Maunalua Bay came primarily from the south, with small variations in direction owing to 

refraction of the trade-wind waves. The waves were largest in the central part of the bay at the 

Wailupe 20-m site because of the greater exposure of this site compared to the other sites 

(appendix 6.1). The smallest waves were measured at the Paikō 1-m site, which is relatively 

protected in the lee of Koko Head (appendix 6.3). Wave height and directions for the June 2010 

experiment were consistent with the wave heights and directions measured between November 

2008 and February 2009 (Storlazzi and others, 2010). 

The currents during the summer coral-spawning season were influenced by the dominant 

trade-wind conditions that occurred throughout the experiment. The mean near-surface and nearseabed current speeds and directions are shown in figure 5 for the three primary study sites off 

Diamond Head, Wailupe, and Paikō. The currents measured during this experiment were 

consistent in speed and direction with currents measured previously in the area under trade-wind 

forcing (Storlazzi and others, 2010). The fastest currents near the surface and near the seabed 

were measured at the Wailupe 20-m site because of its exposure to trade winds; the strong wind 

forcing at this location resulted in currents directed primarily to the west. The strong offshore 

currents measured at the Diamond Head 20-m site may result from the bathymetry at the site as 

well as the topographical steering of the trade winds by Diamond Head crater. The current 

directions in the eastern, inner part of Maunalua Bay at the Paikō 10-m site were to the east and 

were weaker than currents measured in other parts of the bay. The weaker, easterly directed 

currents may be influenced by a circulation eddy created by flow around Koko Head (Storlazzi 

and others, 2010). 
9

Temporal and Spatial Variability in Temperature and Salinity During the 2010 Summer CoralSpawning Season

The cross-shore array of temperature and salinity sensors near the seabed in the eastern 

part of Maunalua Bay provided temporal information on the influence of freshwater and the 

transport of colder, more saline water into shallower areas (fig. 6). The two shallowest locations 

(Paikō 5-m and 10-m sites) show the greatest influence by freshwater. At the nearshore Paikō 5-

m site, daily heating and cooling of the water by insolation with fairly constant salinity was 

observed. The salinity intermittently decreased 1–2 PSU, which could be attributed to freshwater 

inputs either from surface runoff mixing into the water-column or submarine groundwater. The 

Paikō 10-m site shows more regular and substantial decreases in salinity, which may be 

attributed to pulses of submarine groundwater discharge like those observed in a previous 

experiment in 2008–2009 (Storlazzi and others, 2010). The Paikō 20-m site shows a smaller 

decrease in salinity caused by inputs from freshwater sources but shows a slight trend of inputs 

of cooler, higher salinity water. This pattern may indicate the transport of deeper ocean water up 

into the shallower depths, potentially by internal waves. The temperature and salinity patterns at 

the 30 m mooring also show higher salinity and lower temperatures that may be attributed to 

internal waves advecting colder, saltier water from deeper offshore into the study area.

Figure 7 shows the mean temperature and variability near the surface and near the seabed 

during the 4 days of vessel surveys. Overall, near-surface temperatures were fairly constant 

throughout the bay, with slightly warmer temperatures closer to shore in the western part of the 

bay (fig. 7A). The temperatures close to the seabed were also fairly constant throughout the bay, 

except close to shore on the eastern side of the bay. The lower temperatures near the seabed may 

have been a result of submarine groundwater discharge in this area. In general, the temperature 

near the surface was higher than the near-seabed values, likely because of insolation. Figure 8 

shows the mean salinity and variability near the surface and near the seabed during the 4 days of 

vessel surveys. The salinity data near the surface was higher close to shore and most variable 

near Hawai‘i Kai harbor (fig. 8A). The salinity data near the seabed also were lower offshore, 

with the highest salinity values and variability near Hawai‘i Kai harbor (fig. 8B). Overall, the 

vertical salinity stratification was small, and for the most part, the salinity was fairly consistent 

throughout the bay. 

Circulation and Potential Coral-larval Dispersal During the 2010 Summer Coral-Spawning 

Season

M. capitata spawning events were predicted to occur every 28 days for approximately 5 

days between 20:00 and 22:00 HST during the summer months of June, July, August, and 

September. Understanding the meteorological (wind) and oceanographic (wave, current, and 

tidal) forcing during these times was important for predicting the transport and ultimate fate of 

the coral larvae in Maunalua Bay. The winds were, on average, from the northeast at 

approximately 6 m/s during the four 2010 summer spawning events. These events were also 

marked by relatively stable barometric pressure, diurnal insolation-driven heating and cooling, 

and little to no rainfall. The tidal regime during the coral-spawning was spring tides, 

transitioning to neap tides. The wave climate during the four 2010 summer spawning events was 

characterized by trade-wind generated waves, with wave heights averaging 0.65 m with 6.5 s 

periods, out of the southeast in Maunalua Bay. 

To better understand the overall trend in near-surface currents during the 4-day study 

period, 2010 YD 163–166 (June 12–15), it was necessary to reduce the potential bias introduced 

by tidal, wind, and wave forcing. This was accomplished by averaging the VM-ADCP data at 
10

400-m intervals along each VM-ADCP survey line (fig. 1B). The resulting mean near-surface (2 

m below the surface) currents are shown in figure 9. The predominant near-surface current 

direction for the 4-day period was to the east for most of the bay. The near-surface currents 

closest to shore were weaker and more variable than the near-surface currents in the middle of 

the bay and offshore. At a depth of 2 m, the effect of the easterly trade winds on the currents was 

reduced such that the currents shown in figure 9 are more likely a result of the tidal asymmetry in 

Maunalua Bay than the influence of the trade winds. Consequentially, the potential transport of 

coral larvae during the June coral-spawning event by currents 2 m below the surface was mainly 

to the east. The data from the 4-day study period indicates coral larvae released in the bay may 

be transported to the east by near-surface currents (2 m below the surface). Coral larvae released 

close to shore would have a longer residence (flushing) time due to the weak currents, compared 

to offshore where the faster currents would result in shorter residence times (fig. 9). 

The Lagrangian surface drifters provided information on the currents 1 m below the 

surface and thus differed from the VM-ADCP survey data (fig. 10) that measured the currents 2 

m below the surface. The majority of the drifters released over reefs following the predicted 

period of coral-spawning each night travelled downwind to the west and were influenced more 

by tidal currents during the initial hours of dispersal at night when the wind speeds were lowest

(appendix 11.1–11.6). The areal extent of the regions occupied by the drifters are shown in figure 

10. The two drifters released close to shore in the eastern and central parts of Maunalua Bay (fig. 

10A,C) travelled primarily to the west and stayed close to shore. The drifter released in the 

eastern part of Maunalua Bay just to the west of Koko Head (fig. 10C) travelled offshore and 

ultimately to the west. The drifter that was released south of Koko Head and initially travelled 

eastwards towards Hanauma Bay was trapped in an eddy that was on the order of 100 m across. 

As the tide changed and wind speeds increased, this drifter was then advected back into 

Maunalua Bay by tidal- and wind-driven currents. 

Acoustic backscatter from 600-kHz ADCPs can provide a semiquantitative measure of 

M. capitata coral larvae in the water-column during spawning events (Storlazzi and others, 

2006). The Paikō 10-m site was situated in an area of M. capitata colonies that were predicted to 

spawn during the 2010 summer months. Figure 11 shows 7-day periods centered on the 2010 

predicted 5-day coral-spawning events in June, July, August, and September. Warmer colors in 

each plot are areas of higher backscatter that indicate greater concentrations of particles (such as 

sediment or coral larvae) in the water column that scatter the acoustic signals emitted from the 

ADCP. Because coral egg-sperm bundles are positively buoyant and float to the surface, the 

presence of elevated backscatter high in the water column during the 5-day spawning periods is 

likely an indication of the presence of coral larvae. Although it is known that some of the 

backscatter was caused by coral larvae in the water-column, it is not possible at this time to 

distinguish the larvae from other material suspended in the water column (fig. 11). With this 

understanding, the backscatter data provide a semiquantitative measurement that confirms the 

presence of coral larvae during the four 2010 summer spawning periods and allows analyses of 

potential coral-larval dispersal using surface current speeds and directions provided by the 

ADCPs.

Based on the currents and acoustic backscatter measured throughout the water column at 

three locations during the four summer 2010 predicted coral-spawning events, the areal extent of 

potential coral-larval dispersal for these time periods can be calculated using the method of 

Storlazzi and others (2006), which is described below. For the purpose of these calculations, 

current velocities and directions are assumed to be homogeneous throughout the study area. This 
11

assumption provides an adequate basis for calculation of the relative direction and magnitude of 

flow during the projected time period if forcing mechanisms (wind and tides) remain uniform 

over the projected travel path. The areal extent of potential coral-larval dispersal over a 96-hour 

period from the three observation sites (Diamond Head, Wailupe, and Paikō) is shown in figure 

12. The smallest area of potential coral-larval dispersal was at the Paikō 10-m site in the 

northeastern part of the bay because of slower currents resulting from less wind-driven forcing in 

the lee of Koko Head; this area may also be affected by an eddy that was suggested by Storlazzi 

and others (2010). Data from the Wailupe 20-m site showed the greatest areal extent of potential 

coral-larval dispersal because of the presence of fast wind-driven currents to the west during 

periods of predicted coral-spawning. This area of the bay experiences fast current speeds 

(maximum speeds of 1 m/s) to the west, because trade winds are uninhibited by any topographic 

highs. The areal extent of potential coral-larval dispersal at the Diamond Head 20-m site was 

also smaller than the middle of the bay off Wailupe and showed potential dispersal offshore to 

the south. This may have been a result of the steep gradient in bathymetry offshore and 

topographic steering of the trade winds offshore from Diamond Head crater. 

The mean VM-ADCP data (fig. 9), Lagrangian surface drifter data (fig. 10), and potential 

coral-larval dispersal pathways calculated from the ADCP data (fig. 12) together suggest that 

material is transported at different speeds and directions from different depths and locations in 

Maunalua Bay during the summer coral-spawning period. At the surface, there appears to be two 

different transport patterns related to the relatively strong trade-wind forcing that is characteristic 

of the Hawaiian Islands in the summer. Most of the surface waters in the central and western 

parts of Maunalua Bay are rapidly transported downwind to the west during the daytime when 

insolation-driven sea breezes contribute to strong wind forcing, resulting in relatively short water

residence times of water and surface material. During the night, however, the surface currents in 

the bay follow the tidal currents, which during and just following the 2010 M. capitata spawning 

periods were toward the east. In contrast to the majority of the bay, the current field in the lee of 

Koko Head appears to be protected from strong trade-wind forcing. Currents flowing around 

Koko Head, combined with high cross-shore velocity shear (as seen in fig. 9), appear to generate 

small-scale eddies that cause relatively long residence times of water and surface material during 

both the daytime and nighttime. In general, currents a few meters below the surface are faster 

farther offshore than closer to shore, likely because of the greater height of the water column

relative to the hydrodynamic roughness of the coral reefs and seabed. Close to shore, the current 

flow a few meters below the surface varies substantially along Maunalua Bay. Off Koko Head 

and Diamond Head, the mean currents are faster near shore (~10 cm/s) than in the middle of the 

bay, where mean currents are weaker (~1 cm/s). The faster currents are likely caused by flow 

constriction and acceleration around these headlands. These observations suggest that water

residence times are much shorter in the deep, middle part of the bay and off Diamond Head and 

Koko Head, and much longer in the shallows (<10-m depth) along the upper fore reef of the 

fringing reef between Wailupe and Hawai‘i Kai. 

The meteorologic and oceanographic data from both this study and previous 

investigations (Storlazzi and others, 2010) show that flow in Maunalua Bay during small wave 

conditions is primarily controlled by the winds and tides. The general flow patterns and seawater 

properties show greater consistency during the summer months, when the forcing by northeast 

trade winds is relatively steady, storms are infrequent, and nearshore surface-wave-induced 

flows are at a minimum. During both the initial, intensive survey period (2010 YD 163–166) and 

the summer coral-spawning season (June–September), both the forcing (winds and tides) and the 
12

resulting flow and environmental patterns were relatively consistent, with northeast-southwest 

oscillating tidal currents having a superimposed net flow to the southwest and offshore, 

consistent with previous datasets (Storlazzi and others, 2010). Similar wind forcing and flow 

response across multiple spawning periods resulted in comparable models of projected water and 

coral-larvae dispersal pathways during the 2010 spawning season. Because M. capitata always 

spawns during the nights following a new moon, these spawning events occur during the 

transition from spring to neap tides, and thus the relative magnitude of the tidal-current forcing 

during each spawning period is relatively consistent. These consistent patterns, along with the 

similar paths that the drifters followed over multiple deployments, suggest that the temporally

limited Lagrangian surface-drifter trajectories from the survey period (2010 YD 163–166) are 

likely a good model for initial coral-larvae dispersal patterns of M. capitata in Maunalua Bay 

during the summer months and may be applicable to larvae of other Hawaiian corals.

Summary 

In all, more than 3 million measurements of meteorologic and oceanographic forcing and 

the resulting water-column properties were made during this study of factors affecting corallarval dispersal in Maunalua Bay in the summer of 2010. Key findings from these measurements 

and subsequent analyses include:

(1) The currents at the surface (0–2 m) measured by the bottom mounted ADCP’s and 

surface drifters and the currents below the surface (>2 m) measured by the VM-ADCP were 

often oriented in opposite directions. Surface currents were generally to the west because of 

prevailing trade-wind forcing. The currents just below the surface down to the seabed were 

toward the east, resulting in shear and causing material at different depths in the water-column to 

be transported in different directions. 

(2) Water-column properties, including salinity and temperature, were more uniform 

throughout the bay than those observed during the winter of 2008–2009 (Storlazzi and others, 

2010), likely because there is less rainfall and terrestrial runoff and smaller waves during the 

summer. 

(3) Small eddies were observed off the eastern part of Maunalua Bay in the lee of Koko 

Head. These eddies likely increase the residence time of particles (such as coral larvae) at the 

surface in the eastern part of the bay. Just to the west of Paikō, the surface currents were strongly 

to the west, causing shorter residence times in the central and western parts of the bay than in the 

eastern part of the bay in the lee of Koko Head. 

(4) The consistent meteorologic and oceanographic forcing during the coral-spawning 

season and the resulting consistent flow patterns and water-column properties suggest that the 

temporally limited Lagrangian surface-drifter trajectories from the survey period (2010 YD 163–

256) are likely a good model for initial dispersal patterns of M. Capitata coral larvae in 

Maunalua Bay during the summer months and may be applicable to larvae of other Hawaiian 

corals. 

Acknowledgments 

This work was carried out as part of the USGS Coral Reef Project as part of an effort in 

the United States and its trust territories to better understand the effect of geologic processes on 

coral reef ecosystems. Robert Richmond and Jonathan Martinez of the University of Hawai‘i and 

the staff at the University of Hawai‘i’s Kewalo Marine Laboratory helped with project planning 

and provided significant logistical help and facilities to support our field operations. Alyssa 
13

Miller, Dede Mamiya, and others at Mālama Maunalua helped with local project coordination 

and outreach. Steven Anthony and Ron Rickman of the USGS Pacific Islands Water Science 

Center and Gordon Tribble of the USGS Pacific Islands Ecological Research Center provided 

field support and scientific insight while also helping with project coordination. Richard Boyd, 

the manager at Mt. Terrace Condominiums, provided us with access and security that made it 

possible to deploy a weather station atop the facility. Matt Zimmerman of Island Divers 

graciously allowed us the use of the D/V Sea Fox and D/V Leila for nighttime scuba-diving 

operations and drifter deployment and recovery operations. We would also like to thank Amy 

Draut and Dan Hoover of the USGS, who contributed numerous excellent suggestions and a 

timely review of our work. 

References Cited

Heyward, A.J., 1986, Sexual reproduction in five species of the coral Montipora, in Jokiel, P.L., 

Richmond, R.H., and Rogers, R.A., eds., Coral reef population biology: Kaneohe, Oahu, 

Hawaii, Institute of Marine Biology, Technical Report 37, p. 170–178. 

Kolinski, S.P., and Cox, E.F., 2003, An update on modes and timing of gamete and planula 

release in Hawaiian scleractinian corals with implications for conservation and 

management: Pacific Science, v. 57, p. 17–27. 

Mate, J.L., Wilson, J., Field, S., and Neves, E.G., 1998, Fertilization dynamics and larval 

development of the scleractinian coral Montipora verrucosa in Hawai‘i, in Cox, E.F., 

Krupp, D.A., Jokiel, P.L., eds., Reproduction in reef corals: Kaneohe, Oahu, Hawaii, 

Hawaii Institute of Marine Biology, Technical Report 42, p. 27–39. 

Moberly, R.M., and Chamberlain, T., 1964, Hawaiian beach systems: University of Hawaii, 

Honolulu, Hawaii Institute of Geophysics Report HIG 64–2, p. 177. 

Storlazzi, C.D., Brown, E.K., and Field, M.E., 2006, The application of acoustic Doppler current 

profilers to measure the timing and patterns of coral-larval dispersal: Coral Reefs, v. 25, 

p. 369–381. 

Storlazzi, C.D., Presto, M.K., Logan, J.B., and Field, M.E., 2010, Coastal circulation and 

sediment dynamics in Maunalua Bay, Oahu, Hawaii—Measurements of waves, currents, 

temperature, salinity, and turbidity; November 2008–February 2009: USGS Open-File 

Report 2010-1217, 60 p., available at http://pubs.usgs.gov/of/2010/1217. 

Additional Digital Information

For additional information on the instrument deployments, please see: 

http://walrus.wr.usgs.gov/infobank/a/a210oa/html/a-2-10-oa.meta.html

http://walrus.wr.usgs.gov/infobank/a/a310oa/html/a-3-10-oa.meta.html

For an online PDF version of this report, please see:

http://pubs.usgs.gov/of/2012/1040/. For more information on the U.S. Geological Survey Western 

Region’s Coastal and Marine Geology Team, please see:

http://walrus.wr.usgs.gov/

For more information on the U.S. Geological Survey’s Coral Reef Project, 

please see:

http://coralreefs.wr.usgs.gov/
14

Direct Contact Information

General Project Information

Curt D. Storlazzi (USGS Coral Reef Project chief): cstorlazzi@usgs.gov

Regarding this Report:

Kathy Presto: kpresto@usgs.gov
15

Tables

Table 1. Experiment personnel.

Person Affiliation Responsibilities

Curt Storlazzi USGS Chief scientist, diver

Kathy Presto USGS Oceanographer, Instrument specialist

Joshua Logan USGS Physical scientist, diver

Tom Reiss USGS Dive safety officer

Pete Dal Ferro USGS Mechanical technician, diver

Jamie Grover USGS Mechanical technician, diver

Tim Elfers USGS Mechanical technician

Kurt Rosenberger USGS Oceanographer

Joe Reich F/V Alyce C Vessel captain

Table 2. Instrument package sensors and location information.

Site name Depth

[m]

Sensors

Wailupe 20 m 22 Nortek 600 kHz AWAC acoustic Doppler current profiler

22 Seabird SBE-37SI Microcat conductivity-temperature sensor

Diamond Head 20 m 16 RD Instruments 600 kHz Workhorse Monitor acoustic Doppler current 

profiler

16 Seabird SBE-37SI Microcat conductivity-temperature sensor

Paikō 30 m 30 Seabird SBE-37SI Microcat conductivity-temperature sensor

Paikō 20 m 20 RD Instruments 600 kHz Workhorse Monitor acoustic Doppler current 

profiler

20 Seabird SBE-37SI Microcat conductivity-temperature sensor

Paikō 10 m 9 RD Instruments 600 kHz Workhorse Monitor acoustic Doppler current 

profiler

9 Seabird SBE-37SI Microcat conductivity-temperature sensor

Paikō 5 m 5 Seabird SBE-37SI Microcat conductivity-temperature sensor

Weather Station [71]1 NovaLynx WS-16N-A weather station

1

Height, in meters

Table 3. Instrument package location information.

Site name Latitude

[decimal degrees]

Longitude

[decimal degrees]

Wailupe 20 m 21.2582760 -157.7543004

Diamond Head 20 m 21.2449005 -157.7990587

Paikō 30 m 21.2561031 -157.7190399

Paikō 20 m 21.2603369 -157.7201058

Paikō 10 m 21.2720695 -157.7245325

Paikō 5 m 21.2739577 -157.7243602

Weather Station (WS) 21.2876970 -157.7194594
16

Table 4. Water-column profiler (WCP) cast location and depth information.

Cast location Latitude

[decimal degrees]

Longitude

[decimal degrees]

Depth

[m]

1 21.25573 -157.711634 36.9

2 21.27250 -157.719923 6.4

3 21.27292 -157.736445 7.1

4 21.26427 -157.733499 18.1

5 21.27055 -157.715829 4.4

6 21.28028 -157.712304 1.9

7 21.26060 -157.712136 5.4

8 21.25768 -157.731398 20.6

9 21.27289 -157.736287 7.1

10 21.26912 -157.756957 5.9

11 21.25406 -157.752922 19.9

12 21.25028 -157.769402 24.6

13 21.26302 -157.774762 10.9

14 21.25175 -157.799892 7.6

15 21.24315 -157.750340 22.1

16 21.24412 -157.797837 15.4

17 21.25191 -157.799873 6.1

18 21.26388 -157.774500 5.9

19 21.25023 -157.769893 23.1

20 21.25361 -157.752997 20.4

21 21.26914 -157.756860 5.4

22 21.27347 -157.735662 3.9

23 21.25733 -157.731310 21.1

24 21.26056 -157.712052 5.1

25 21.28019 -157.712175 2.4

26 21.27056 -157.715975 5.4

27 21.26383 -157.733745 18.9

28 21.27294 -157.721457 5.4

29 21.25687 -157.712139 32.1

30 21.25602 -157.711589 37.6

31 21.27168 -157.719714 5.4

32 21.27342 -157.736055 4.9

33 21.26406 -157.733364 18.1

34 21.27041 -157.716249 5.4

35 21.28051 -157.712169 1.1

36 21.26038 -157.712024 5.6

37 21.25761 -157.730646 20.9

38 21.26931 -157.756982 4.9

39 21.25397 -157.752879 19.9

40 21.25024 -157.769337 24.9

41 21.26360 -157.774937 6.4

42 21.25210 -157.799914 7.4

43 21.24414 -157.798911 20.4

44 21.24423 -157.799100 19.9

45 21.25233 -157.800075 4.1

46 21.26398 -157.774537 5.9

47 21.24998 -157.769916 20.4

48 21.25389 -157.752797 20.1

49 21.26886 -157.756978 5.9

50 21.27362 -157.735817 6.1

51 21.25756 -157.731307 20.9

52 21.26013 -157.712311 12.1
17

Table 4. Water-column profiler (WCP) cast location and depth information.—Continued

Cast location Latitude

[decimal degrees]

Longitude

[decimal degrees]

Depth

[m]

53 21.28065 -157.712155 1.4

54 21.27056 -157.715854 4.4

55 21.26409 -157.733478 18.4

56 21.27317 -157.721260 5.4

57 21.25603 -157.711875 37.1

Table 5. Vessel-mounted acoustic Doppler current profiler (VM-ADCP) log information.

[HST, Hawaii Standard Time]

Line number Line name Filename Date [MM/DD/YYYY] Start time [HST] Stop time [HST]

1 T-5 ADCP_001 06/12/2010 09:23:05 09:41:20

3 T-6 ADCP_003 06/12/2010 10:12:05 10:25:40

4 T-7 ADCP_004 06/12/2010 10:37:30 10:53:20

5 T-8 ADCP_005 06/12/2010 10:58:09 11:03:37

6 T-9 ADCP_006 06/12/2010 11:20:02 11:34:22

7 T-10 ADCP_007 06/12/2010 11:37:22 11:51:21

8 T-11 ADCP_008 06/12/2010 11:55:56 12:09:56

9 T-12 ADCP_009 06/12/2010 12:12:17 12:25:46

10 T-13 ADCP_010 06/12/2010 12:40:51 12:52:31

11 T-14 ADCP_011 06/12/2010 12:57:00 13:15:46

12 T-15 ADCP_012 06/12/2010 13:18:04 13:26:34

13 T-15 ADCP_013 06/13/2010 08:38:05 08:46:03

14 T-14 ADCP_014 06/13/2010 08:48:54 09:12:54

15 T-13 ADCP_015 06/13/2010 09:14:55 09:27:45

16 T-12 ADCP_016 06/13/2010 09:44:23 09:59:11

17 T-11 ADCP_017 06/13/2010 10:01:42 10:21:30

18 T-10 ADCP_018 06/13/2010 10:23:01 10:38:51

19 T-9 ADCP_019 06/13/2010 10:43:04 10:59:35

20 T-8 ADCP_020 06/13/2010 11:19:45 11:27:04

21 T-7 ADCP_021 06/13/2010 11:29:26 11:42:55

22 T-6 ADCP_022 06/13/2010 11:54:42 12:07:19

23 T-5 ADCP_023 06/13/2010 12:10:41 12:24:52

24 T-4 ADCP_024 06/13/2010 12:28:29 12:31:57

25 T-3 ADCP_025 06/14/2010 09:21:48 09:23:30

26 T-4 ADCP_026 06/14/2010 09:26:08 09:29:02

27 T-5 ADCP_027 06/14/2010 09:33:49 09:50:17

28 T-6 ADCP_028 06/14/2010 09:52:52 -

29 T-6 ADCP_029 06/14/2010 09:54:28 10:06:46

30 T-7 ADCP_030 06/14/2010 10:17:43 10:34:32

31 T-8 ADCP_031 06/14/2010 10:37:14 10:47:14

32 T-9 ADCP_032 06/14/2010 11:05:29 11:21:00

33 T-10 ADCP_033 06/14/2010 11:24:29 11:41:02

34 T-11 ADCP_034 06/14/2010 11:42:55 11:59:14

35 T-12 ADCP_035 06/14/2010 12:02:04 12:17:15

36 T-13 ADCP_036 06/14/2010 12:35:10 12:48:52

37 T-14a ADCP_037 06/14/2010 12:53:09 13:09:52

38 T-14b ADCP_038 06/14/2010 13:10:49 13:17:27

39 T-15 ADCP_039 06/14/2010 13:19:45 13:26:52

40 T-15 ADCP_040 06/15/2010 08:59:09 09:07:39

41 T-14 ADCP_041 06/15/2010 09:10:27 09:34:48

42 T-13 ADCP_042 06/15/2010 09:37:18 09:50:48

43 T-12 ADCP_043 06/15/2010 10:08:39 10:23:41

44 T-11 ADCP_044 06/15/2010 10:39:13 10:57:53

45 T-10 ADCP_045 06/15/2010 11:02:02 11:16:41

46 T-9 ADCP_046 06/15/2010 11:20:39 11:36:28
18

Table 5. Vessel-mounted acoustic Doppler current profiler (VM-ADCP) log information.—Continued

Line number Line name Filename Date [MM/DD/YYYY] Start time [HST] Stop time [HST]

47 T-8 ADCP_047 06/15/2010 11:54:32 12:03:22

48 T-7 ADCP_048 06/15/2010 12:05:53 12:22:04

49 T-6 ADCP_049 06/15/2010 12:33:04 12:46:02

50 T-5 ADCP_050 06/15/2010 12:49:18 13:05:09

51 T-4 ADCP_051 06/15/2010 13:10:13 13:13:20

Table 6. Lagrangian surface-drifter log information.

[HST, Hawaii Standard Time]

Start 

Location 

ID

Start Latitude

[decimal 

degrees]

Start Longitude 

[decimal 

degrees]

Start Date and 

Time [HST]

Stop Latitude

[decimal 

degrees]

Stop Longitude 

[decimal 

degrees]

Stop Date 

and Time 

[HST]

A 21.27194 -157.72471 6/12/2010 

22:50

21.24962 -157.80060 6/13/2010 

13:18

C 21.26963 -157.74484 6/12/2010 

23:27

21.26643 -157.87117 6/13/2010 

07:54

A 21.27221 -157.72432 6/13/2010 

23:18

21.25023 -157.80171 6/14/2010 

13:40

D 21.25647 -157.70618 6/13/2010 

23:33

21.26444 -157.72078 6/14/2010 

19:57

A 21.27210 -157.72404 6/14/2010 

23:11

21.26935 -157.76783 6/15/2010 

10:20

B 21.26389 -157.71682 6/14/2010 

23:18

21.25280 -157.85039 6/15/2010 

0:29

Table 7. Meteorological statistics.

[All statistics were calculated from 2010 Year Days 163-256; wind direction is “from”]

Parameter Mean ± 1 standard

deviation Minimum Maximum

Barometric pressure [mb] 1009.38±1.27 1005.75 1013.25

Air temperature [

o

C] 24.99±1.30 21.19 29.19

Precipitation [mm] 0.014±0.10 0 2.5

Wind speed [m/s] 6.28±1.52 1.62 11.81

Wind direction [o] 78.69±10.13 0.31 135.88

Table 8. Wave statistics.

[All statistics were calculated from 2010Year Days 163–256; wave direction is “from”]

Site name Parameter Mean ± 1 standard 

deviation

Minimum Maximum

Wailupe 20 m1 Height [m] 0.68 ±0.16 0.59 1.48

Period [s] 4.33±0.47 3.04 5.81

Direction [o] 152.06±8.50 127.33 175.18

Diamond Head 20 m Height [m] 0.85±0.21 0.43 1.91

Period [s] 8.14±1.4 5.4 14.1

Direction [o] 179.11±23.59 87.0 223.0

Paikō 20 m Height [m] N.D.±N.D. N.D. N.D.

Period [s] N.D.±N.D. N.D. N.D.

Direction [o] N.D.±N.D. N.D. N.D

Paikō 10 m Height [m] 0.71±0.32 0.17 1.49

Period [s] 8.30±1.56 4.7 13.9

Direction [o] 191.88±8.25 159.0 222.0

1

Statistics were calculated only for 2010 Year Days 223–256.

N.D., No data.
19

Table 9. Current statistics.

[All statistics were calculated from 2010 Year Days 163–256; current direction is “going to”]

Site name Parameter Depth [m] Mean ± 1 standard deviation Minimum Maximum

Wailupe 20 m Speed [m/s] 2 [N.S.] 0.08±0.15 0.00 0.96

Direction [o] 2 [N.S.] 180.92±91.21 0.0 359.95

Speed [m/s] 19 [N.B.] 0.04±0.15 0.00 0.86

Direction [o] 19 [N.B.] 241.19±97.69 0.0 359.82

Diamond Head 20 m Speed [m/s] 2 [N.S.] 0.08±0.24 0.01 1.00

Direction [o] 2 [N.S.] 180.92±84.33 6.14 332.22

Speed [m/s] 15 [N.B.] 0.05±0.14 0.00 0.87

Direction [o] 15 [N.B.] 215.69±80.44 8.48 336.96

Paikō 20 m Speed [m/s] 2 [N.S.] N.D.±N.D. N.D. N.D.

Direction [o] 2 [N.S.] N.D.±N.D. N.D. N.D.

Speed [m/s] 19 [N.B.] N.D.±N.D. N.D. N.D.

Direction [o] 19 [N.B.] N.D.±N.D. N.D. N.D.

Paikō 10 m Speed [m/s] 2 [N.S.] 0.04±0.06 0.00 0.40

Direction [o] 2 [N.S.] 123.83±84.33 1.34 358.58

Speed [m/s] 9 [N.B.] 0.03±0.03 0.00 0.19

Direction [o] 9 [N.B.] 81.62±89.46 2.39 358.68

N.D., No data.

N.S., Near surface. 

N.B., Near bed. 

Table 10. Water temperature statistics.

[All statistics were calculated for 2010 Year Days 163–256] 

Site name

Depth

[m]

Mean ± 1 standard 

deviation

[

o

C]

Minimum

[

o

C]

Maximum

[

o

C]

Wailupe 20 m 22 25.60±0.22 24.92 26.31

Diamond Head 20 m 16 25.60±0.22 24.40 26.33

Paikō 30 m 30 25.42±0.41 22.96 26.22

Paikō 20 m1 20 25.46±0.28 24.47 26.30

Paikō 10 m 9 25.58±0.24 24.85 26.33

Paikō 5 m 5 25.65±0.29 24.73 26.79

1

Statistics were calculated only for 2010 Year Days 162–222.

Table 11. Salinity statistics.

[All statistics were calculated for 2010 Year Days 163-256; PSU, Practical Salinity Units]

Site Name

Depth

[m]

Mean ± 1 standard 

deviation

[PSU]

Minimum

[PSU] 

Maximum

[PSU] 

Wailupe 20 m 22 35.01±0.12 33.94 35.25

Diamond Head 20 m 16 34.64±1.21 28.87 35.25

Paikō 30 m 30 35.09±0.06 34.28 35.82

Paikō 20 m1 20 34.78±0.19 33.44 35.10

Paikō 10 m 9 34.74±0.66 28.22 35.45

Paikō 5 m 5 35.09±0.08 33.08 35.47

1

Statistics were calculated only for 2010 Year Days 162–222.
20

Table 12. Lagrangian surface-drifter statistics.

Start location ID Duration [hr] Total distance 

Traveled [km]

Net distance 

Traveled [km]

Net direction [o] Max velocity 

[m/s]

A 14:20 15.8 8.2 252 0.57

C 8:20 14.2 13.1 268 0.75

A 14:15 13.3 8.4 253 0.53

D 20:20 15.8 1.7 300 0.64

A 11:00 6.4 4.5 266 0.46

B 09:05 16.0 13.9 265 1.09
21

Figures

Figure 1. A, Aerial photograph and scanning hydrographic operational airborne lidar surveys (SHOALS) 

bathymetric map of Maunalua Bay and its location on O‘ahu, Hawaii. Also shown are the location of 

instrument packages and major landmarks. B, Vessel-mounted acoustic Doppler current-profiler (VMADCP) tracklines and water-column Profiler (WCP) cast locations are denoted by italic white numbers 

and numbers in dots, respectively. 

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22

Figure 2. A–C, Photographs of the equipment used in Maunalua Bay during the 2010 summer 

experiment. A, Underwater photograph of a MiniProbe with an acoustic Doppler current profiler (ADCP) 

and a conductivity and temperature (CT) sensor along the 10-m isobath at the Paikō 10-m site. B,

Water-column Profiler (WCP). C, Example of a Lagrangian surface drifter in the ocean taken from the 

R/V Alyce C. D, Example of the coral, Montipora capitata, the spawning of which was the focus of 

the 2010 summer experiment.
23

Figure 3. Time-series plot of meteorologic and oceanographic forcing in Maunalua Bay during the 2010 

summer experiment. A, Barometric pressure, in millibars. B, Air temperature, in degrees Celsius. C, 

Wind speed, in meters per seconds, with average wind speed in blue and peak wind speed in red. D, 

Wind speed and direction, in meters per second from true north. E, Half-hour rainfall (blue) and 

cumulative rainfall (red), in millimeters. F, Tidal height, in meters. G, Average (blue) and peak (red) 

wave height, in meters. The shaded area highlights the largest wave event during the summer and the 

associated meteorological conditions. The tidal signal reflects the semidiurnal nature of the tide and the 

time period shown encompassed 6 spring-neap tidal cycles. 
24

Figure 4. Map showing the mean (blue vectors) and variability (red ellipses) in wave heights and 

directions, in meters from true north, in Maunalua Bay during the 2010 summer experiment for the 

Diamond Head 20-m, Wailupe 20-m, and Paikō 10-m sites. All of the sites show the predominant wave 

direction from the south, with the largest waves measured in the more exposed central part of the bay. 
25

Figure 5. Map showing the mean (vectors) and variability (ellipses) in current speeds and directions, in 

meters per second from true north, in Maunalua Bay for the 2010 summer experiment. Red, nearsurface currents; blue, near-bed currents. Currents directions in the bay vary as a result of proximity to 

headlands and local bathymetry. Current speeds are greater near the surface than near the bed and 

are mainly to the west and offshore except at the Paikō 10-m site, which was deployed in the lee of 

Koko Head crater.
26

Figure 6. Scatter plot showing the relationship between water temperature, in degrees Celsius, and 

salinity, in Practical Salinity Units (PSU) along the cross-shore transect off Paikō from 5-m to 30-m 

water depth. Plots show the influence of freshwater close to shore at the shallow sites (lowered 

salinities) and possibly the influence of internal waves at the deepest site (colder, saltier observations). 
27

Figure 7. Map showing the spatial variability in temperature, in degrees Celsius, averaged from watercolumn profiler (WCP) surveys in Maunalua Bay made during the June 12–15 (2010 Year Days 162-

166) coral-spawning period. A, Averaged data from 1 m below the surface. B, Averaged data from 1 m 

above the seabed. The near-surface temperature data show very uniform temperature throughout the 

bay, with slightly warmer temperatures close to shore on the western side of the bay. The near-bed 

data show relatively uniform temperature data across the bay, with slightly cooler temperatures close to 

shore on the eastern side of the bay. In general, warmer temperatures were measured near the surface 

than close to the seabed, although the thermal stratification was small. 
28

Figure 8. Map showing the spatial variability in salinity, in Practical Salinity Units (PSU), from the watercolumn profiler (WCP) surveys in Maunalua Bay averaged over the 4 days, June 12–15 (2010 Year 

Days 162-166) coral-spawning period. A, Averaged data from 1 m below the surface. B, Averaged data 

from 1 m above the seabed. The near-surface salinity was fairly uniform throughout the bay, with the 

highest salinity values observed close to shore, possibly because of evaporation. The near-bed salinity 

values were, in general, higher close to shore and near Hawai‘i Kai harbor. 
29

Figure 9. Map showing of mean current speeds and directions (arrows) and variability (ellipses), in 

meters per second from true north, for the vessel-mounted acoustic Doppler current-profiler (VMADCP) data from surveys during the June 12–15 (2010 Year Days 162-166) coral-spawning period,

averaged at 400 m intervals along each VM-ADCP survey line. The predominant near-surface (2 m 

below the surface) current direction for the four-day period was to the east for most of the bay. The 

near-surface currents closest to shore were the most variable and weak, with the fastest near-surface 

currents occurring in the middle of the bay and offshore. 
30

Figure 10. Map showing the areal extent of satellite drifters released from 4 locations (A-D) in Maunalua 

Bay over three nights June 12–15 (2010 Year Days 163–165) in Maunalua Bay following predicted 

times of coral-spawning in an attempt to track potential coral-larval dispersal. A, Inshore location on the 

east side of the bay near Hawai‘i Kai harbor. B, Mid-shore location on the east side of the bay near 

Koko Head. C, Inshore location near Wailupe Peninsula. D, Offshore location near Koko Head. Most of 

the drifters that were released in the bay followed the tidal currents but ultimately traveled to the west 

toward Diamond Head, except for the drifter released offshore of Koko Head. This drifter traveled in 

and out of the bay, travelling as far as offshore of Hanauma Bay and then back into the eastern side of 

Maunalua Bay. 
31

Figure 11. Time-series plots showing the vertical variation in acoustic Doppler current profiler (ADCP) 

acoustic backscatter data before, during, and after the 2010 summer predicted coral-spawning periods 

in Maunalua Bay and tide data from the Paikō 10-m site. A, Data from the June spawning period (2010 

Year Days 162–166). B, Data from the July spawning period (2010 Year Days 191–195). C, Data from 

the August spawning period (2010 Year Days 221–225). D, Data from the September spawning period 

(2010 Year-Days 250–254). Relative abundance of coral larvae were detected by the ADCP’s acoustic 

backscatter data, as shown by elevated acoustic backscatter (red, highest values; blue, lowest values)

from the seabed up to the surface during the periods of spawning. Tidal stage is also shown for 

reference on each plot. 
32

Figure 12. Map showing the areal extent of potential coral-larval dispersal (Storlazzi and others, 2006) 

from the Diamond Head 20-m (green), Wailupe 20-m (blue), and Paikō 10-m (red) sites during the 

2010 summer predicted coral-spawning events in June, July, August, and September in Maunalua Bay. 

Note the similarities, and differences, between these data and the Lagrangian surface drifter tracks 

shown in figure 10. 
33

Appendixes

Appendix 1. Acoustic Doppler Current Profiler (ADCP) Information

RD Instruments 600-kHz Workhorse Monitor upward-looking acoustic Doppler current profiler

s/n: 2074

Transmitting Frequency: 614 kHz 

Depth of Transducer: 20 m 

Blanking Distance: 0.25 m 

Height of First Bin above Transducer: 1.45 m 

Bin Size: 1.0 m 

Number of Bins: 24 

Operating Mode: High-resolution, broad bandwidth 

 Sampling Frequency: 2 Hz

 Time per Ping: 00:04.00 

 Pings per Ensemble: 75 

 Profile Ensemble Interval: 0:05:00.00 

Wave Ensemble Interval: 2:00:00.00 

Sound Speed Calculation: Set salinity, updating temperature by

 sensor 

RD Instruments 600-kHz Workhorse Monitor upward-looking acoustic Doppler current profiler

s/n: 2432

Transmitting Frequency: 614 kHz 

Depth of Transducer: 16.5 m 

Blanking Distance: 0.25 m 

Height of First Bin above Transducer: 1.45 m 

Bin Size: 1.0 m 

Number of Bins: 24 

Operating Mode: High-resolution, broad bandwidth 

 Sampling Frequency: 2 Hz

 Time per Ping: 00:04.00 

 Pings per Ensemble: 75 

 Profile Ensemble Interval: 0:05:00.00 

Wave Ensemble Interval: 2:00:00.00 

Sound Speed Calculation: Set salinity, updating temperature by 

 sensor 
34

RD Instruments 600-kHz Workhorse Monitor upward-looking acoustic Doppler current profiler

s/n: 7447

Transmitting Frequency: 614 kHz 

Depth of Transducer: 10 m 

Blanking Distance: 0.25 m 

Height of First Bin above Transducer: 1.45 m 

Bin Size: 1.0 m 

Number of Bins: 12 

Operating Mode: High-resolution, broad bandwidth 

 Sampling Frequency: 2 Hz

 Time per Ping: 00:04.00 

 Pings per Ensemble: 100 

 Profile Ensemble Interval: 0:05:00.00 

Wave Ensemble Interval: 2:00:00.00 

Sound Speed Calculation: Set salinity, updating temperature by 

 sensor 

Nortek Instruments 1-MHz AWAC upward-looking acoustic Doppler current profiler

s/n: 5471

Transmitting Frequency: 1 MHz

Depth of Transducer: 20 m 

Blanking Distance: 0.50 m 

Height of First Bin above Bed: 1.50m 

Bin Size: 1.00m 

Number of Bins: 24 

Average interval: 0:07:30.00 

Profile interval: 0:10:00.00 

Wave interval: 1:00:00.00 

Wave cell size: 2.4 m 

Operating Mode: High-resolution 

 Sound Speed Calculation: Set salinity, updating temperature via 

 sensor 

Data Processing:

The RD Instruments current data were processed using the WinADCP program and the wave data 

using the WavesMon program. The Nortek current data were processed using the Prof2NDP 

program and the wave data using the QuickWave program.

The data were averaged over 1 hour ensembles, all of the spurious data above the water surface 

were removed and all of the data in bins where the beam correlation dropped below 80% were 

removed for visualization and analysis.
35

Appendix 2. Conductivity and Temperature (CT) Information

Seabird Microcat SBE-37SM temperature-conductivity (CT) sensors

s/n: 3800, 3801, 4368, 4369, 7046, and 7047

 Sampling Frequency: 2 Hz

 Measurements per Burst: 4 

 Time Between Bursts: 00:05:00.00

Data Processing:

The CT data were post-processed for visualization and analysis by removing all instantaneous 

(only one data point in time) data spikes that exceeded the deployment mean + 3 standard 

deviations.

Appendix 3. Weather Station (WS) Information

NovaLynx WS-16N-A Marine-grade Weather Station:

Anemometer: 200-05106-MA (marine model)

Temperature & Relative Humidity: 110-WS-16TH-A w/radiation shield

Barometric Pressure Sensor: 110-WS-16BP

Rain Gauge: 110-WS-16RC

Sampling Frequency: 1 Hz

Measurements per Burst: 1,500

 Time Between Bursts: 00:30:00.00

Appendix 4. Water-Column Profiler (WCP) Information

Conductivity/Temperature/Depth (CTD) Profiler with Optical Backscatter (OBS),

Photosynthetically-Available Radiation (PAR), Dissolved Oxygen (DO), and

Chlorophyll (chl) Sensors

Instruments:

Seabird 19plus CTD sensor; s/n: 5250

D&A Instruments OBS-3 sensor; s/n: 1135

Seabird pressure sensor; s/n: 2632709

Wet Labs CStar; s/n: 712

Sampling Frequency: 4 Hz

Position Information:

Garmin GPS-76 GPS; s/n: 80207465; USGS/CRP unit#1

Data Processing:

The profiler data were processed using the SBEDataProcessing program.

 

 The data were averaged into 0.5 m vertical bins and all of the spurious data

marked by a flag in the raw data were removed for visualization and analysis.

Stratification were measured as the difference between the mean of the top

three bins (0.5–1.5 m below the surface) and the bottom three bins (0.5–1.5 m

above the bed).
36

Appendix 5. Water-Column Profiler (WCP) log, June 2010

Cast 

Number/Site

Date 

[MM/DD/YYY]

Time

[HST]

Latitude

[decimal degrees]

Longitude

[decimal degrees]

Depth

[m]

1 06/12/2010 09:19:07 21.25573 -157.711634 36.9

2 06/12/2010 09:42:15 21.27250 -157.719923 6.4

3 06/12/2010 10:26:19 21.27292 -157.736445 7.1

4 06/12/2010 10:34:39 21.26427 -157.733499 18.1

5 06/12/2010 10:53:53 21.27055 -157.715829 4.4

6 06/12/2010 11:03:59 21.28028 -157.712304 1.9

7 06/12/2010 11:18:24 21.26060 -157.712136 5.4

8 06/12/2010 11:34:59 21.25768 -157.731398 20.6

9 06/12/2010 11:51:50 21.27289 -157.736287 7.1

10 06/12/2010 12:10:45 21.26912 -157.756957 5.9

11 06/12/2010 12:26:22 21.25406 -157.752922 19.9

12 06/12/2010 12:38:20 21.25028 -157.769402 24.6

13 06/12/2010 12:53:21 21.26302 -157.774762 10.9

14 06/12/2010 13:16:12 21.25175 -157.799892 7.6

15 06/12/2010 13:27:13 21.24315 -157.750340 22.1

16 06/13/2010 08:36:07 21.24412 -157.797837 15.4

17 06/13/2010 08:46:56 21.25191 -157.799873 6.1

18 06/13/2010 09:13:29 21.26388 -157.774500 5.9

19 06/13/2010 09:28:29 21.25023 -157.769893 23.1

20 06/13/2010 09:41:51 21.25361 -157.752997 20.4

21 06/13/2010 09:59:52 21.26914 -157.756860 5.4

22 06/13/2010 10:21:24 21.27347 -157.735662 3.9

23 06/13/2010 10:39:33 21.25733 -157.731310 21.1

24 06/13/2010 10:59:57 21.26056 -157.712052 5.1

25 06/13/2010 11:17:45 21.28019 -157.712175 2.4

26 06/13/2010 11:27:34 21.27056 -157.715975 5.4

27 06/13/2010 11:43:56 21.26383 -157.733745 18.9

28 06/13/2010 12:07:51 21.27294 -157.721457 5.4

29 06/13/2010 12:25:29 21.25687 -157.712139 32.1

30 06/14/2010 09:30:28 21.25602 -157.711589 37.6

31 06/14/2010 09:50:51 21.27168 -157.719714 5.4

32 06/14/2010 10:07:11 21.27342 -157.736055 4.9

33 06/14/2010 10:14:40 21.26406 -157.733364 18.1

34 06/14/2010 10:35:21 21.27041 -157.716249 5.4

35 06/14/2010 10:47:21 21.28051 -157.712169 1.1

36 06/14/2010 11:03:37 21.26038 -157.712024 5.6

37 06/14/2010 11:21:46 21.25761 -157.730646 20.9

38 06/14/2010 12:00:18 21.26931 -157.756982 4.9

39 06/14/2010 12:17:51 21.25397 -157.752879 19.9

40 06/14/2010 12:31:53 21.25024 -157.769337 24.9

41 06/14/2010 12:49:48 21.26360 -157.774937 6.4

42 06/14/2010 13:18:13 21.25210 -157.799914 7.4

43 06/14/2010 13:27:36 21.24414 -157.798911 20.4

44 06/15/2010 08:56:08 21.24423 -157.799100 19.9

45 06/15/2010 09:08:29 21.25233 -157.800075 4.1

46 06/15/2010 09:35:26 21.26398 -157.774537 5.9

47 06/15/2010 09:51:38 21.24998 -157.769916 20.4

48 06/15/2010 10:06:09 21.25389 -157.752797 20.1

49 06/15/2010 10:25:32 21.26886 -157.756978 5.9

50 06/15/2010 10:58:39 21.27362 -157.735817 6.1

51 06/15/2010 11:17:33 21.25756 -157.731307 20.9

52 06/15/2010 11:36:56 21.26013 -157.712311 12.1
37

Cast 

Number/Site

Date 

[MM/DD/YYY]

Time

[HST]

Latitude

[decimal degrees]

Longitude

[decimal degrees]

Depth

[m]

53 06/15/2010 11:53:39 21.28065 -157.712155 1.4

54 06/15/2010 12:04:02 21.27056 -157.715854 4.4

55 06/15/2010 12:22:47 21.26409 -157.733478 18.4

56 06/15/2010 12:46:36 21.27317 -157.721260 5.4

57 06/15/2010 13:06:01 21.25603 -157.711875 37.1

Appendix 5. Water-Column Profiler (WCP) log, June 2010—Continued 
38

Appendix 6. Time-series Plots of Variations in Water Level, Wave Heights, Wave Periods, 

and Wave Directions from Acoustic Doppler Current Profilers (ADCPs) in Maunalua Bay for 

2010 Year Days 163–256 (June 12–September 13)

Appendix 6.1. Tide and wave data from the ADCP at the Wailupe 20-m site. A, Tidal height, in 

meters. B, Wave height, in meters, with significant wave height in blue and maximum wave 

height in red. C, Wave period, in seconds, with mean wave period in blue and peak wave period 

in red. D, Wave height (red), in meters, and wave height and direction (blue), in meters from true 

north. Because of issues with the pressure sensor, wave data were only collected from 2010 Year 

Days 223–256 (August 11–September 13). 
39

Appendix 6.2. Tide and wave data from the ADCP at the Diamond Head 20-m site. A, Tidal 

height, in meters. B, Wave height, in meters, with significant wave height in blue and maximum 

wave height in red. C, Wave period, in seconds, with mean wave period in blue and peak wave 

period in red. D, Wave height (red), in meters, and wave height and direction (blue), in meters 

from true north. 
40

Appendix 6.3. Tide and wave data from the ADCP at the Paikō 10-m site. A, Tidal height, in 

meters. B, Wave height, in meters, with significant wave height in blue and maximum wave 

height in red. C, Wave period, in seconds, with mean wave period in blue and peak wave period 

in red. D, Wave height (red), in meters, and wave height and direction (blue), in meters from true 

north. 
41

Appendix 7. Time-Series Plots of Variations In Water Level, Currents, and Temperature from 

Acoustic Doppler Current Profilers (ADCPs) in Maunalua Bay for 2010 Year Days 163–256 

(June 12–September 13)

Appendix 7.1. Tide, current, and water temperature data from the ADCP at the Wailupe 20-m 

site. A, Tidal height, in meters. B, Near-surface current speeds and directions, in meters per 

second from true north. C, Mid-depth current speeds and directions, in meters per second from 

true north. D, Near-bed current speeds and directions, in meters per second from true north. E, 

Temperature, in degrees Celsius. Because of issues with the pressure sensor, tidal data was not 

collected from this instrument. 
42

Appendix 7.2. Tide, current, and water temperature data from the ADCP at the Diamond Head 

20-m site. A, Tidal height, in meters. B, Near-surface current speeds and directions, in meters per 

second from true north. C, Mid-depth current speeds and directions, in meters per second from 

true north. D, Near-bed current speeds and directions, in meters per second from true north. E, 

Temperature, in degrees Celsius. 
43

Appendix 7.3. Tide, current, and water temperature data from the ADCP at the Paikō-10 m site. 

A, Tidal height, in meters. B, Near-surface current speeds and directions, in meters per second 

from true north. C, Mid-depth current speeds and directions, in meters per second from true 

north. D, Near-bed current speeds and directions, in meters per second from true north. E, Water 

temperature, in degrees Celsius. 
44

Appendix 8. Time-Series Plots of Variations in Temperature and Salinity from 

Conductivity/Temperature (CT) Sensors in Maunalua Bay for 2010 Year Days 163–256 (June 

12–September 13)

Appendix 8.1. Temperature and salinity data from the CT at the Wailupe 20-m site. A, Water 

temperature, in degrees Celsius. B, Salinity, in Practical Salinity Units (PSU).
45

Appendix 8.2. Temperature and salinity data from the CT at the Diamond Head 20-m site. A, 

Water temperature, in degrees Celsius. B, Salinity, in Practical Salinity Units (PSU).
46

Appendix 8.3. Temperature and salinity data from the CT at the Paikō 5-m site. A, Water 

temperature, in degrees Celsius. B, Salinity, in Practical Salinity Units (PSU).
47

Appendix 8.4. Temperature and salinity data from the CT at the Paikō 10-m site. A, Water 

temperature, in degrees Celsius. B, Salinity, in Practical Salinity Units (PSU).
48

Appendix 8.5. Temperature and salinity data from the CT at the Paikō 20-m site. A, Water 

temperature, in degrees Celsius. B, Salinity, in Practical Salinity Units (PSU).
49

Appendix 8.6. Temperature and salinity data from the CT at the Paikō 30-m site. A, Water 

temperature, in degrees Celsius. B, Salinity, in Practical Salinity Units (PSU).
50

Appendix 9. Maps Showing the Spatial Variability in Temperature and Salinity from WaterColumn Profiler (WCP) Casts in Maunalua Bay

Appendix 9.1. Maps showing the spatial variability in temperature, in degrees Celsius, from the 

WCP on 2010 Year Day 163 (June 12). A, Spatial variability of the mean temperature, in degrees 

Celsius, measured 1 m below the surface. B, Spatial variability of the mean temperature, in 

degrees Celsius, measured 1 m above the seabed. C, Spatial variability of temperature, in degrees 

Celsius, depth averaged for each cast, showing the mean and standard deviation. 
51

Appendix 9.2. Maps showing the spatial variability in temperature, in degrees Celsius, from the 

WCP on 2010 Year Day 164 (June 13). A, Mean temperature measured 1 m below the surface. B, 

Mean temperature measured 1 m above the seabed. C, Depth-averaged mean and variability in 

temperature. 
52

Appendix 9.3. Maps showing the spatial variability in temperature, in degrees Celsius, from the 

WCP on 2010 Year Day 165 (June 14). A, Mean temperature measured 1 m below the surface. B, 

Mean temperature measured 1 m above the seabed. C, Depth-averaged mean and variability in 

temperature. 
53

Appendix 9.4. Maps showing the spatial variability in temperature, in degrees Celsius, from the 

WCP on 2010 Year Day 166 (June 15). A, Mean temperature measured 1 m below the surface. B, 

Mean temperature measured 1 m above the seabed. C, Depth-averaged mean and variability in 

temperature. 
54

Appendix 9.5. Maps showing the spatial variability in salinity, in Pratical Salinity Units (PSU), 

from the WCP on 2010 Year Day 163 (June 12). A, Mean salinity measured 1 m below the 

surface. B, Mean salinity measured 1 m above the seabed. C, Depth-averaged mean and 

variability in salinity. 
55

Appendix 9.6. Maps showing the spatial variability in salinity, in Pratical Salinity Units (PSU), 

from the WCP on 2010 Year Day 164 (June 13). A, Mean salinity measured 1 m below the 

surface. B, Mean salinity measured 1 m above the seabed. C, Depth-averaged mean and 

variability in salinity.
56

Appendix 9.7. Maps showing the spatial variability in salinity, in Pratical Salinity Units (PSU), 

from the WCP on 2010 Year Day 165 (June 14). A, Mean salinity measured 1 m below the 

surface. B, Mean salinity measured 1 m above the seabed. C, Depth-averaged mean and 

variability in salinity. 
57

Appendix 9.8. Maps showing the spatial variability in salinity, in Pratical Salinity Units (PSU), 

from the WCP on 2010 Year-Day 166 (June 15). A, Mean salinity measured 1 m below the 

surface. B, Mean salinity measured 1 m above the seabed. C, Depth-averaged mean and 

variability in salinity. 
58

Appendix 10. Maps Showing the Spatial Variability in Near-Surface Current Speeds and 

Directions from Vessel-Mounted Acoustic Doppler Current Profiler (VM-ADCP) Surveys in 

Maunalua Bay

Appendix 10.1. Maps showing the spatial variability in near-surface current speed and direction, 

in meters per second from true north, from the VM-ADCP surveys. Mean and variability of 

current speed measured 2 m below the surface on 2010 Year Day 163 (June 12). 
59

Appendix 10.2. Maps showing the spatial variability in near-surface current speed and direction, 

in meters per second from true north, from the VM-ADCP surveys. Mean and variability of 

current speed measured 2 m below the surface on 2010 Year Day 164 (June 13). 
60

Appendix 10.3. Maps showing the spatial variability in near-surface current speed and direction, 

in meters per second from true north, from the VM-ADCP surveys . Mean and variability of 

current speed measured 2 m below the surface on 2010 Year Day 165 (June 14). 

 
61

Appendix 10.4. Maps showing the spatial variability in near-surface current speed and direction, 

in meters per second from true north, from the VM-ADCP surveys .Mean and variability of 

current speed measured 2 m below the surface for on 2010 Year Day 166 (June 15). 
62

Appendix 11. Maps and Time-Series Plots of Lagrangian Surface-Drifter Deployments in 

Maunalua Bay 

Appendix 11.1. Map of Lagrangian surface-drifter movement and time-series plot of data for a 

drifter released at location A on 2010 Year Day 163 (June 12) at 22:50 HST and recovered on 

2010 Year Day 164 (June 13) at 13:18 HST. A, Map of drifter hourly locations and velocities, in 

meters per second, through time. B, Stick plot of drifter velocity and direction, in meters per 

second from true north, during the deployment. Dashed line represents drifter speeds. C, Stick 

plot of wind velocity (black), in meters per second from true north, and tidal height (blue), in 

meters, during the drifter deployment. Dashed line represents wind speed. 
63

Appendix 11.2. Map of Lagrangian surface-drifter movement and time-series plot of data for a 

drifter released at location C on 2010 Year Day 163 (June 12) at 23:30 HST and recovered on 

2010 Year Day 164 (June 13) at 07:54 HST. A, Map of drifter hourly locations and velocities, in 

meters per second, through time. B, Stick plot of drifter velocity and direction, in meters per 

second from true north, during the deployment. Dashed line represents drifter speeds. C, Stick 

plot of wind velocity (black), in meters per second from true north, and tidal height (blue), in 

meters, during the drifter deployment. Dashed line represents wind speed. 
64

Appendix 11.3. Map of Lagrangian surface-drifter movement and time-series plot of data for a 

drifter released at location A on 2010 Year Day 164 (June 13) at 23:18 HST and recovered on 

2010 Year Day 165 (June 14) at 13:40 HST. A, Map of drifter hourly locations and velocities, in 

meters per second, through time. B, Stick plot of drifter velocity and direction, in meters per 

second from true north, during the deployment. Dashed line represents drifter speeds. C, Stick 

plot of wind velocity (black), in meters per second from true north, and tidal height (blue), in 

meters, during the drifter deployment. Dashed line represents wind speed. 
65

Appendix 11.4. Map of Lagrangian surface-drifter movement and time-series plot of data for a 

drifter released at location A on 2010 Year Day 164 (June 13) at 23:33 HST and recovered on 

2010 Year Day 165 (June 14) at 19:57 HST. A, Map of drifter hourly locations and velocities, in 

meters per second, through time. B, Stick plot of drifter velocity and direction, in meters per 

second from true north, during the deployment. Dashed line represents drifter speeds. C, Stick 

plot of wind velocity (black), in meters per second from true north, and tidal height (blue), in 

meters, during the drifter deployment. Dashed line represents wind speed. 
66

Appendix 11.5. Map of Lagrangian surface drifter movement and time-series plot of data for a 

drifter released at location A on 2010 Year Day 165 (June 14) at 23:11 HST and recovered on 

2010 Year Day 166 (June 15) at 10:20 HST. A, Map of drifter hourly locations and velocities, in 

meters per second, through time. B, Stick plot of drifter velocity and direction, in meters per 

second from true north, during the deployment. Dashed line represents drifter speeds. C, Stick 

plot of wind velocity (black), in meters per second from true north, and tidal height (blue), in 

meters, during the drifter deployment. Dashed line represents wind speed. 
67

Appendix 11.6. Map of Lagrangian surface drifter movement and time-series plot of data for a 

drifter released at location A on 2010 Year Day 165 (June 14) at 23:38 HST and recovered on 

2010 Year Day 166 (June 15) at 08:29 HST. A, Map of drifter hourly locations and velocities, in 

meters per second, through time. B, Stick plot of drifter velocity and direction, in meters per 

second from true north, during the deployment. Dashed line represents drifter speeds. C, Stick 

plot of wind velocity (black), in meters per second from true north, and tidal height (blue), in 

meters, during the drifter deployment. Dashed line represents wind speed.