Technical Report No. 77
Sea Grant College Program, Year 05
Project Principal Investigator
L. STEPHEN LAU
Sea Grant Cooperative Report UNIHI-SEAGRANT-CR-74-05
This report summarizes the results of the second year of investigative and evaluative work of the University of Hawaii’s Sea Grant Program project, “Quality of Coastal Waters” The general objectives of this multidisciplinary project are to identify, develop, and evaluate the critical physical, biological, and rational parameters needed in formulating effective policies, institutions, and systems for protecting the quality of coastal waters in Hawaii. To this end, the attainment of eight specific objectives is assigned to faculty specialists participating in the 14 activities which comprise the Project. These specialists also assist the Principal Investigator in planning the work and in interpreting the results.
Research activities for the project year consisted principally of field and laboratory studies of coastal waters initiated in the first project year but with increased emphasis on biota and sediment. Assistance was rendered to the State Department of Health in the revision and updating of the State Water Quality Standards.
Kahana Bay was selected for study as a coastal water area under the influence of relatively undeveloped land. Land contribution of nutrients to the bay via Kahana Stream and all nonpoint routes was found to be small despite the perennial nature of the surface and subsurface discharges. However, the nitrogen and phosphorus levels measured for Kahana Bay waters and in the contiguous open ocean water exceeded the levels allowed under its state Class AA water classification. Coliform organism concentrations met the Class A rather than Class AA standards. Thus, the Kahana Bay water quality tends to satisfy the Class A standard rather than the Class AA standard.
Heavy metals, especially lead, copper, zinc, chromium, and nickel, appeared consistently and within a range of a few to a few hundred ppm in the bay sediments, stream sediments, and watershed soils. The ubiquitous nature of their presence is related to the parent rocks from which the soils and sediment are derived. However, mercury and cadmium were only occasionally detected in the sediments and when detected, occurred at only within a range of a fraction of to a few parts per million. DDT was detected in the range of a few parts per trillion in the Kahana Bay sediment together with only periodically detected and very low levels of dieldrin, DDE, a and y chlordane. In the Kahana Bay water both heavy metals and DDT were detected but only at levels similar to open ocean water, i.e., a fraction of, or a few parts per billion for the heavy metals, and only a few parts per trillion for DDT.
The project’s approach to revealing the effects of urban land development is selection of single predominant type of urbanization of land to reveal the cause-effect relation.
Recreational use of coastal land and water in and domestic urban use of water and the abutting land in Hawaii Kai Marina and east Maunalua Bay furnish such situations. Domestic sewage is collected and removed from the areas.
Investigative results for the Hawaii Kai area and Maunalua Bay showed a general trend to improvement in water quality from the marina to the near-ocean bay waters. Nitrogen levels in the bay and only the near-ocean station were within the Class A state standard by which the water bodies are classified but phosphorus levels exceeded the standard elsewhere. All heavy metals were consistently present in the coastal sediments in the parts per million level. The levels of the ubiquitous pesticides analyzed, DDT, dieldrin, and PCP, (the latter is used primarily for termite control in house construction), were at least one order of magnitude higher than in the Kahana Bay sediments, thus reflecting intensive urban activities associated with a relatively new and growing residential development.
In the Hawaii Kai Marina and coastal waters, heavy metals were detected in the usual minimal parts per billion level as in open ocean water, and DDT, dieldrin and PCP were in the usual parts per trillion range. A turbid water plume in Maunalua Bay was occasionally identified and apparently was related to currents and roiling bottom sediments rather than any liquid discharge. A biota study of the bay waters was completed and detailed.
Coastal water quality data obtained for the Mamala Bay waters off in support of a conjunctive study by Chave for the Corps of Engineers and coliform monitoring by the Department of Health are reported. in general the data satisfied state requirements for Class A waters except for phosphorus. Coral abundance was generally less toward Diamond Head than toward Ala Wai Canal. which is the only major drainage canal intercepting the surface runoff from the valleys and discharging into coastal waters. From the findings, there is little evidence which would attribute any specific water quality effect solely to the presence of intense recreational activity at Sandy Beach represents a rather complex situation and departs from the project approach: the open ocean coast beach being popular, the land use changing from rural and undeveloped to residential urban development, and above all, the coastal water receiving treated domestic effluent. Shoreline water quality data were obtained to complement the studies undertaken by the consulting firm of Sunn, Low, Tom, and Hara, and the routine monitoring by the State Health Department. Results for the project area showed clear shoreline water similar to but with higher nutrients than Kahana Bay water and the state Class A standard Levels. However, the study by the consulting firm of the offshore condition adjacent to the Hawaii Kai sewer outfall showed that there is little significant effect to the coastal water and benthos from the discharge of treated wastewater off Sandy Beach.
A baseline survey of benthic biota, particularly coral and micromollusc abundance and diversity, and fish was performed for Kailua Bay, the proposed Mokapu outfall site, and the existing Kailua sewer outfall. While the greatest abundance and species diversity of the fish were not near the outfall, the highest standing crop of micromolluscs is near the outfall. The occurrence of micromolluscs is comparable with the patterns in other areas of similar depth and substrate.
Nonpoint discharge studies of sugarcane production and milling wastes were continued but at a reduced scale on Kauai. Observations of mill waste discharge and coastal water, sediments, and biota were made both before and after the 90-year old Kilauea Sugar Company closed down its operations in north Kauai in 1971. Untreated mill wastes were found to be the major contributing factor to the presence of coliforms, sediments, trash, and bagasse. The effect was largely an extensive visible plume in the coastal waters and debris in both the water and on the beach. Sediments, rather than water, harbored most of the nutrients, heavy metals, and pesticides in the ocean. DDT, although not used by the sugarcane industry, was present in small amounts in all wastes and sediments. Herbicides used in sugarcane culture did not appear in coastal waters. A striking aesthetic improvement of the coastal water and the beach quickly followed the cessation of mill waste discharge. Coastal water qualities continued to improve: phosphorus decreased to better than Class AA standards, DDT and PCP were detectable only at parts per trillion level. The rapid improvement is attributed to both the cessation of mill waste discharge and the heavy sea. Beach and ocean sediments continue to harbor about the same level of heavy metals but contain a much decreased amount of nutrients. Fish have reappeared rapidly since 1973. No apparent changes in micromolluscs have been observed since the cessation of mill operation. Tentative conclusions of the continued Kilauea investigative studies are: no evidence of eutrophication in coastal water, adverse effects of discharge mostly transitory, and epibenthic communities more influenced by waves, currents, and coastal topography than by mill waste discharge.
Studies were continued in south Kauai to assess the effect of changed operation practices by the McBryde Sugar Company subsequent to an EPA survey of coastal waters of the area in 1968. Company practices demonstrate that it is possibze to operate milzing operations without discharge to the ocean, and to prevent irrigation tailwater overflows except flooding due to intense rainfall. At the time of reporting, the coastal waters of Wahiawa Bay showed an anomalously high nitrogen content while no pesticide residues were found in the offshore water except for the one to two parts per trillion DDT which seems to be present everywhere.
Evaluative summaries were detailed for several key quality parameters in water and sediment. Heavy metals were ubiquitous and in parts per million range in coastal sediment in Hawaii. This suggests that if standards for the level of heavy metals in dredge spoil were to be set, care should be taken not to fix unrealistic levels that cannot possibly be attained. In the coastal waters, heavy metals also occur but only in the parts per billion range, a level quite comparable to the level in ocean water. Conjunctive studies of mercury uptake in an aquatic food chain from the water and sediment were continued and detailed.
Of the insecticides, the presence of DDT in sediments is ubiquitous. In Maunalua Bay and Hawaii Kai sediments, dieldrin, and a and y chlordane are found frequently and with highest concentration in the Low parts per billion range. Their occurrence may be attributed to prior and current continous use of these chemicals in the abutting land area and the poor sediment circulation within the Hawaii Kai Marina. In coastal waters insecticides were generally undetectable or at only a few parts per trillion. PCP, like DDT, seems to occur ubiquitously.
Herbicide residues in West Loch of Pearl Harbor and Kaiaka Bay were studied. Atrazine and ametryne do not appear to be a problem, however, because of its persistence in soils, diuron can be found in coastal sediments because eroded agricultural soils are transported with storm runoff.
Kahana Bay water contains about the lowest amounts of nutrients in coastal waters. The state standards for nitrogen and phosphorus were exceeded in all areas except for Kilauea, in the case of nitrogen, and McBryde, in the case of phosphorus.
The use of mircomolluscs as an indicator organism was reported with a differentiation noted in species between coastal areas affected primarily by silting compared to areas affected primarily by nutrient input. In the former situation Bittium zebrum becomes the major fauna component and standing crops and diversity values are conspicuously depressed. In the latter case, the community changes towards dominance by suspension feeding forms which depend on primary productivity of the water columns. Also associated strongly with silted reef flats is Obtortio pupoides. The responses of an ecosystem to land-generated effects are changes in structure from a grazing herbivore environment with associated frondose algae to either a rubble associated ecosystem with few species or to a eutrophic state with many suspension feeders and Low diversity.
The principal changes in institutional arrangements noted in the project year are those resulting from the passage of the Federal Water Pollution Control Act Amendments PL 92-500. The effects of this legislation will be far-reaching and result in changes which include: new discharge permit requirements, reporting of operating and monitoring results for wastewater treatment facilities, a minimum requirement level of secondary treatment for municipal wastewaters, and industrial waste treatment effluent guidelines. The full impact of these and other changes is not yet apparent although some delays have incurred in regulatory actions and attempts to implement legislation.