Mamala Bay Research Articles

The distribution of estuarine and oceanic water masses on the southern shore of O'ahu, Hawai'i: Ecological and coastal management implications, and novel methodology

The distribution of estuarine and oceanic water masses along the shelf of Mamala Bay, O'ahu, Hawaii, were determined by use of larval supply and recruitment patterns of benthic invertebrate species, stable C and N isotopic compositions of the suspension‐feeding bivalve, Spondylus tenebrosus, turbidity, drifter, and CTD data. The recruitment of different species among estuaries was used to associate larval species with particular estuarine waters. Recruitment patterns of these species along the shelf were then used to infer water‐mass distributions along the shelf. The spatial recruitment pattern of an oceanic lepadomorph barnacle, Conchoderma virgatum, was useful to infer shelf areas exposed to oceanic waters. Water‐mass distributions inferred from the recruitment distribution of these species concurred with spatial patterns of turbidity and stable C and N isotopic compositions of S. tenebrosus, as well as drifter observations. Water‐mass distributions observed in this study also concurred with biological distributional patterns observed in other studies, such as distributions of phytoplankton and zooplankton and the distribution of coral bio‐erosion in the Bay. The ecological implications of this work include further evidence of the physical control of recruitment and biological pattern and the possible control of patch dynamics on the scale of kilometers due to significant recruitment variability at this scale. The prevailing distribution of water masses determined in this study also has important implications for the management of watersheds associated with Mamala Bay.

Closure to “Modeling Mamala Bay Outfall Plumes. II: Far Field” by Philip J. W. Roberts

Closure to “Modeling Mamala Bay Outfall Plumes. II: Far Field” by Philip J. W. Roberts

Closure to “Modeling Mamala Bay Outfall Plumes. I: Near Field” by Philip J. W. Roberts

Closure to “Modeling Mamala Bay Outfall Plumes. I: Near Field” by Philip J. W. Roberts

Internal tide effects on a sewage plume at Sand Island, Hawaii

The variability in the vertical position of a sewage plume, far from its point of discharge, is described and explained by the forcing from an internal tide. The sewage plume, discharged from the Sand Island treatment plant in the coastal waters of Mamala Bay, Oahu, Hawaii, was mapped using ship-board towyo observations collected during September 25 – October 1, 1994. Horizontal currents and temperature were measured in 1994–1995 at moorings located throughout Mamala Bay. Data at mooring D2, located close to the diffuser, suggested that the presence of an internal tide of 18 km wavelength propagating along the isobaths at speed 0.4 m s −1 was responsible for large (more than half the total depth) semi-diurnal vertical displacements of the isotherms. Comparison of the vertical far-field plume position and isotherm displacements at the mooring showed that the horizontal propagation of the internal tide was westward along the isobaths. These data challenge the classical view of a sewage plume “established” at a constant depth of equilibrium and are the first example showing the effects of internal tides on sewage plumes.

Modeling Mamala Bay Outfall Plumes. I: Near Field

Modeling Mamala Bay Outfall Plumes. I: Near Field

Modeling Fate of Pathogenic Organisms in Coastal Waters of Oahu, Hawaii

A comprehensive modeling study was undertaken to examine the transport and fate of pathogenic organisms in the coastal waters of Mamala Bay, the southern shore of the island of Oahu, Hawaii. Specifically, two mathematical models were developed, calibrated, and validated in an attempt to understand both the relative contributions of various outfall and shoreline sources to organism counts throughout Mamala Bay and the benefits achieved by various source control options. A three-dimensional hydrodynamic model was constructed to simulate the advective and dispersive processes observed in the bay. A near field plume model was coupled with the hydrodynamic model to realistically incorporate initial mixing dynamics. Results of the hydrodynamic model were then used by a pathogen fate model to predict the distributions of fecal contamination indicator organisms and specific pathogens at several locations throughout the bay. Two sources were identified as primary contributors of contamination within Mamala Bay: the outfall from the Sand Island wastewater treatment plant and the Ala Wai Canal. The relative importance of the sources was dependent on the indicator organism used to assess fecal contamination. Using the fate model results and assuming a seven consecutive day exposure, the maximum risk of infection at Waikiki Beach was estimated to be 1.3/100 for virus and 3.1/10,000 for Giardia. The upgrade of the Sand Island treatment plant to chemically-enhanced primary treatment reduced organism counts throughout the bay by about a factor of two. Additional reductions were achieved by adding disinfection or upgrading the plant to secondary treatment. The implementation of the evaluated source control options would reduce the risks of infection at Waikiki Beach.

Coastal water quality in Hawaii: the importance of buffer zones and dilution

A study of the relationship between point and nonpoint source freshwater discharges and marine water quality were studied during a period of 1 year in Mamala Bay, a coastal indentation on the south shore of the island of Oahu, Hawaiian Islands. Despite the fact that 100–300×10 6 m 3 year −1 of land runoff/groundwater seepage and 150×10 6 m 3 year −1 of treated sewage effluent enter Mamala Bay and its tributaries, coastal water quality as judged by standard chemical and physical parameters is high at virtually all locations in the bay. The explanation for the high water quality reflects several important factors. First, much of the nonpoint source discharge enters either estuaries or harbors, which function as buffer zones by trapping some of the sediment and nutrients that would otherwise enter the coastal ocean. Second, the principal point source discharges are located in water sufficiently deep that their wastewater plumes are trapped below the surface most of the time. When the plumes surface they are sufficiently diluted that their impact on parameters, such as nutrient concentrations, is undetectable. Third, the coastal current system is greatly diluted by exchange with the offshore ocean. Based on a simple box model, the degree of mixing with the offshore ocean is roughly 40 times the rate of input of fresh water from point and nonpoint sources. The offshore wastewater outfalls have no discernible effect on water quality at any recreational beach along the shoreline. The principal impact on water quality at the recreational beaches comes from nonpoint source discharges, and with the exception of one beach located directly adjacent to a stream mouth, that impact is on the composition rather than the concentration of the plankton. There is a systematic shift from a chlorophyte- to a diatom-dominated phytoplankton community due to the high silicate concentration in groundwater and land runoff, and there is a systematic increase in the δ 15N of suspended particles due to the high δ 15N of the biologically available nitrogen in groundwater seepage. ©

Far field modeling of the Mamala Bay outfalls

The results of far field modeling of the wastefield formed by the Sand Island, Honolulu, ocean outfall are presented. A far field model, FRFIELD, was coupled to a near field model, NRFIELD. The input data for the models were long time series of oceanographic observations over the whole water column including currents measured by Acoustic Doppler Current Profilers and density stratification measured by thermistor strings. Thousands of simulations were made to predict the statistical variation of wastefield properties around the diffuser. It was shown that the visitation frequency of the wastefield decreases rapidly with distance from the diffuser. The spatial variation of minimum and harmonic average dilutions was also predicted. Average dilution increases rapidly with distance. It is concluded that any impact of the discharge will be confined to a relatively small area around the diffuser and beach impacts are not likely to be significant.

Holocene coral reef accretion in Hawaii: a function of wave exposure and sea level history

In the high Hawaiian Islands, significant accretion due to coral reef growth is limited by wave exposure and sea level. Holocene coral growth and reef accretion was measured at four stations off Oahu, Hawaii, chosen along a gradient in wave energy from minimum to maximum exposures. The results show that coral growth of living colonies (linear extension) at optimal depths is comparable at all stations (7.7–10.1 mm/y), but significant reef accretion occurs only at wave sheltered stations. At wave sheltered stations in Hanauma Bay and Kaneohe Bay, rates of long term reef accretion are about 2.0 mm/y. At wave exposed stations, off Mamala Bay and Sunset Beach, reef accretion rates are virtually zero in both shallow (1 m) and deeper (optimal) depths (12 m). At wave sheltered stations, such as Kaneohe Bay and Hanauma Bay, Holocene reef accretion is on the order of 10–15 m thick. At wave exposed stations, Holocene accretion is represented by only a thin veneer of living corals resting on antecedent Pleistocene limestone foundations. Modern coral communities in wave exposed environments undergo constant turnover associated with mortality and recruitment or re-growth of fragmented colonies and are rarely thicker than a single living colony. Breakage, scour, and abrasion of living corals during high wave events appears to be the major source of mortality and ultimately limits accretion to wave sheltered environments. Depth is particularly important as a modulator of wave energy. The lack of coral reef accretion along shallow open ocean coastlines may explain the absence of mature barrier reefs in the high Hawaiian Islands.

Incidence of enteroviruses in Mamala Bay, Hawaii using cell culture and direct polymerase chain reaction methodologies

The consequence of point and nonpoint pollution sources, discharged into marine waters, on public recreational beaches in Mamala Bay, Hawaii was evaluated using virus cell culture and direct reverse transcriptase-polymerase chain reaction (RT-PCR). Twelve sites, nine marine, two freshwater (one stream and one canal), and one sewage, were assessed either quarterly or monthly for 1 year to detect the presence of human enteric viruses. Water samples were concentrated from initial volumes of 400 L to final volumes of 30 mL using Filterite electronegative cartridge filters and a modified beef extract elution procedure. Cell culture was applied using the Buffalo Green Monkey kidney cell line to analyze samples for enteroviruses. Positive samples were also evaluated by RT-PCR, using enterovirus-specific primers. Levels of RT-PCR inhibition varied with each concentrated sample. Resin column purification increased PCR detection sensitivity by at least one order of magnitude in a variety of sewage outfall and recreational marine water samples but not in the freshwater canal samples. Using cell culture, viable enteroviruses were found in 50 and 17% of all outfall and canal samples, respectively. Samples were positive at beaches 8% of the time. These data illustrate the potential public health hazard associated with recreational waters. Using direct PCR, viruses were detected at the outfall but were not found in any beach or canal samples, in part, owing to substances that inhibit PCR. Therefore, conventional cell culture is the most effective means of detecting low levels of infectious enteroviruses in environmental waters, whereas direct RT-PCR is rendered less effective by inhibitory compounds and low equivalent reaction volumes.

Characterization of marine temperate phage-host systems isolated from Mamala Bay, Oahu, Hawaii.

To understand the ecological and genetic role of viruses in the marine environment, it is critical to know the infectivity of viruses and the types of interactions that occur between marine viruses and their hosts. We isolated four marine phages from turbid plaques by using four indigenous bacterial hosts obtained from concentrated water samples from Mamala Bay, Oahu, Hawaii. Two of the rod-shaped bacterial hosts were identified as Sphingomonas paucimobilis and Flavobacterium sp. All of the phage isolates were tailed phages and contained double-stranded DNA. Two of the phage isolates had morphologies typical of the family Siphoviridae, while the other two belonged to the families Myoviridae and Podoviridae. The head diameters of these viruses ranged from 47 to 70.7 nm, and the tail lengths ranged from 12 to 146 nm. The burst sizes ranged from 7.8 to 240 phage/bacterial cell, and the genome sizes, as determined by restriction digestion, ranged from 36 to 112 kb. The members of the Siphoviridae, T-phi HSIC, and T-phi D0, and the member of the Myoviridae, T-phi D1B, were found to form lysogenic associations with their bacterial hosts, which were isolated from the same water samples. Hybridization of phage T-phi HSIC probe with lysogenic host genomic DNA was observed in dot blot hybridization experiments, indicating that prophage T-phi HSIC was integrated within the host genome. These phage-host systems are available for use in studies of marine lysogeny and transduction.

Incidence of enteroviruses in Mamala Bay, Hawaii using cell culture and direct polymerase chain reaction methodologies

Incidence of enteroviruses in Mamala Bay, Hawaii using cell culture and direct polymerase chain reaction methodologies

Far field modeling of the Mamala Bay outfalls

Far field modeling of the Mamala Bay outfalls

Coliphage and indigenous phage in Mamala Bay, Oahu, Hawaii.

Public concern over the discharge of primarily treated sewage by two offshore outfalls in Mamala Bay, Oahu, prompted a multidisciplinary study to determine the impact of such activities on the water quality in the bay and at adjacent recreational beaches. As part of this study, we determined the abundance of coliphage as an indicator of fecal pollution along with total viral direct counts and phages infective for Vibrio parahaemoltyicus 16 at stations in Mamala Bay in four quarterly samplings over 13 months. Coliphage (< 1 to 1.2 x 10(3)/liter) were found during each quarterly sampling along an offshore transect to the Sand Island waste treatment facility outfall. The nonpoint coastal stations (Pearl Harbor, Ala Wai Canal, and Ke'ehi Lagoon) had high levels of coliphage during the storm event sampling in February 1994 but much lower levels or none when sampled during dry weather. Coliphage were absent at all samplings at Waikiki Beach and at the control station off Diamond Head. Viral direct counts in eutrophic coastal stations (Pearl Harbor, Ke'ehi Lagoon, Ala Moana Beach, and Ala Wai canal) averaged 10(9)/liter, while counts at offshore stations ranged from 9 x 10(7) to 1 x 10(9) viruses/liter, values similar to those for other marine environments. Vibriophage were found mainly in eutrophic coastal environments (Ala Wai Canal, Pearl Harbor, and Ke'ehi Lagoon) and at the Sand Island Transect stations D1 and D2. The greatest abundance was found during the storm event (February 1994) sampling. These results suggest that the Sand Island outfall influenced the water quality of the immediate surrounding waters but had little effect on the quality of the recreational beaches. Nonpoint discharge sources appeared to be more important in the distribution of fecal indicators in the coastal zone.

A method for the detection and quantitation of PCR template in environmental samples by high performance liquid chromatography

This study describes methodology for the detection and quantitation of PCR amplified DNA. Specifically we report the estimation of the prevalence of E. coli in marine waters and other environmental samples from Mamala Bay, Hawaii. High performance liquid chromatography (HPLC) was used to quantitate PCR products containing between 1 and 250 ng DNA. PCR was used to amplify E. coli DNA through the use of lamB primers. A standard curve was generated that related initial cell template concentrations to amplified product DNA concentrations within a template range of 520 to 5.2×10 7 cells. The standard curve was used to determine initial template concentrations of the lamB gene sequence present within 11 different environmental samples. Quantified PCR analyses were most useful when samples contained only low numbers of target organisms, and when environmental samples contained few PCR inhibitory substances, as for example in marine water samples. Quantitation of amplified DNA and comparison with culture data also suggested the presence of viable but nonculturable organisms in some environmental samples. Overall these data are unique in that they indicate the successful use of HPLC to quantitate PCR amplifications with concomitant estimation of PCR template within environmental samples.

Coral reefs in an urban embayment in Hawaii: a complex case history controlled by natural and anthropogenic stress

The effects of natural and anthropogenic stress need to be separated before coral reef ecosystems can be effectively managed. In this paper, a 25 year case history of coral reefs in an urban embayment (Mamala Bay) off Honolulu, Hawaii is described and differences between natural and man-induced stress are distinguished. Mamala Bay is a 30 km long shallow coastal bay bordering the southern (leeward) shore of Oahu and the city of Honolulu in the Hawaiian Islands. During the last 25 years, this area has been hit by two magnitude 5 hurricane events (winds > 240 km/h) generating waves in excess of 7.5 m. Also during this period, two large sewer outfalls have discharged up to 90 million gallons per day (mgd) or (360 × 106 L/day) of point source pollution into the bay. Initially the discharge was raw sewage, but since 1977 it has received advanced primary treatment. Non-point source run-off from the Honolulu watershed also enters the bay on a daily basis. The results of the study show that discharge of raw sewage had a serious but highly localized impact on shallow (∼10 m) reef corals in the bay prior to 1977. After 1977, when treatment was upgraded to the advanced primary level and outfalls were extended to deep water (> 65 m), impacts to reef corals were no longer significant. No measurable effects of either point or non-point source pollution on coral calcification, growth, species composition, diversity or community structure related to pollution can now be detected. Conversely the effects of hurricane waves in 1982 and 1992 together caused major physical destruction to the reefs. In 1982, average coral cover of well-developed offshore reefs dropped from 60–75% to 5–15%. Only massive species in high relief areas survived. Today, recovery is occurring, and notwithstanding major future disturbance events, long-term biological processes should eventually return the coral ecosystems to a more mature successional stage. This case history illustrates the complex nature of the cumulative effects of natural and anthropogenic stress on coral reefs and the need for a long-term data base before the status of a coral reef can be properly interpreted.

Near-field modeling of the Mamala Bay outfalls

Preliminary results of near-field modeling of the wastefield formed by the Sand Island, Honolulu, outfall are presented. Over one thousand simulations were run with the mathematical model RSB using as input data long time series of effluent flowrate and oceanographic observations over the whole water column including currents measured by Acoustic Doppler Current Profilers (ADCPs), and density stratification measured by thermistor strings. It was found that considerable variability in plume behavior occurs, whose extremes depend on particular combinations of flowrate, current, and density stratification. The wastefield is predicted to be submerged, usually deeply, about 90% of the time for the conditions simulated. It is demonstrated that the use of these recently developed instruments combined with appropriate mathematical models can lead to greatly improved predictions of the statistical characteristics of wastefield behavior in coastal waters than has been previously possible.

Near-field modeling of the mamala bay outfalls

Preliminary results of near-field modeling of the wastefield formed by the Sand Island, Honolulu, outfall are presented. Over one thousand simulations were run with the mathematical model RSB using as input data long time series of effluent flowrate and oceanographic observations over the whole water column including currents measured by Acoustic Doppler Current Profilers (ADCPs), and density stratification measured by thermistor strings. It was found that considerable variability in plume behavior occurs, whose extremes depend on particular combinations of flowrate, current, and density stratification. The wastefield is predicted to be submerged, usually deeply, about 90% of the time for the conditions simulated. It is demonstrated that the use of these recently developed instruments combined with appropriate mathematical models can lead to greatly improved predictions of the statistical characteristics of wastefield behavior in coastal waters than has been previously possible.

ENVIRONMENTAL IMPACTS ON AN ISLAND COMMUNITY

The environmental impacts of coastal engineering projects generally affect island communities to a greater degree than they would affect continental land mass communities. This occurs because of the smaller land area; close interdependence and interaction of land and sea communities, both natural and human; and relatively small projects having relatively large overall impacts on island ecosystems. The natural flora and fauna of Pacific Islands have developed rather precariously unbalanced communities that are extremely fragile and susceptible to change, both natural and man induced. This susceptibility dictates that, where possible, man induced or proposed changes, such as coastal engineering projects, should be designed such that as little change as possible occurs to the natural environment. Additionally, the natural resources of island communities are generally limited and this too dictates that conservation practices be employed that assure the highest and best use of those limited resources. The purpose of this paper is to indicate the environmental effects of a major coastal engineering project on an island community. This will be accomplished by describing the environmental quality control monitoring program that has been performed as an integral part of the Honolulu International Airport (HIA) Reef Runway construction project on Oahu, Hawaii, and presenting the initial findings of that environmental monitoring program. The Honolulu International Airport reef runway planning and design began in earnest in 1968 and 1969 with hydrographic and topographic surveys, foundation investigations, two- and three-dimensional hydraulic model studies, and environmental studies that were conducted (J. K. K. Look, 1970; Berger, 1971; Sunn, et_ al_, 1969). These studies, and others, were utilized to determine the technical feasibility, and to gather the engineering and environmental data for final design and construction. The Reef Runway, located south of the HIA runway system on the fringing coral reef, seaward of Keehi Lagoon, in Mamala Bay, is 12,000 feet long and 200 feet wide. The runway and taxiway complex is protected from the sea by a 16,000-foot long protective structure constructed of rock and dollose (Figure 1).