P.I. - Dr. James Moncur, Economics
Sponsor - City of Honolulu, Wastewater Management Department

Researchers at the University of Hawaii's Water Resources Research Center (WRRC) continue to monitor the marine fauna around the City and County of Honolulu's ocean sewage outfalls at Sand Island, Barbers Point, Waianae and Mokapu. This monitoring is performed in order to detect any effects that the discharge of sewage effluent at the outfall may be having on the surrounding ecosystem, and is conducted in partial fulfillment of the requirements for a waiver from secondary treatment granted to the Sand Island Wastewater Treatment Plant (SIWWTP) by the Federal Environmental Protection Agency (EPA). The following describes the work done at Sand Island, however most of the same research tasks are also being done at the abovementioned other outfalls.

WRRC researchers started monitoring the benthic fauna around the City's outfalls on an irregular basis in 1985. In 1995 the Center completed a 5 year contract with the City's Department of Wastewater Management to monitor marine life at the Sand Island, Barbers Point, and Waianae outfalls annually, and at the Mokapu outfall once during this period. In 1997 another 5 year contract was entered into, followed by another in 2002, and the biomonitoring work continues. In order to detect changes over time, every effort has been made to be consistent in the methodology used from year to year. Due to extreme natural fluctuations inherent in populations of the marine organisms being monitored, differentiating between natural changes and man-made changes is problematic. In order to be able to tell if a change in the population of organisms is within the bounds of natural variability or is due to pollution, a sufficiently lengthy period of observation is needed to determine what the normal fluctuations are, and to be able to tell when there is a true imbalance.

The WRRC team performs a variety of studies in the vicinity of the outfalls. One type of study involved obtaining samples of sediment from the ocean floor at various locations around the outfalls and sorting through this material to determine the types and numbers of certain groups; polychaetes (worms), mollusks, and crustaceans, of bottom dwelling organisms living therein. The research team comprises some of Hawaii's foremost authorities on the biology of these groups of organisms. Samples are taken from the same locations every year in order to see if changes in the population makeup and distribution are occuring. Such changes could indicate imbalances in the ecosystem around the outfall.

The work performed by the WRRC biomonitoring group is only one facet of the overall study conducted at the outfalls. Samples of sediment are also sent to an EPA certified contract lab on the mainland for chemical analysis to detect a number of so-called priority pollutants according to EPA guidelines. Other chemical analyses are performed by the City's own laboratory. Some of the parameters examined include total organic carbon, oil and grease, total Kjeldahl nitrogen, oxidation-reduction potential, and grain size analysis. Changes in these parameters can signal an accumulation of sewage derived sediment around the outfall.

Another aspect of the study looks at larger life forms around the outfall. Fish and coral communities at various sites are observed and quantified.

As with the sediment dwelling animals, the fish and corals are monitored at the same sites every year. These fish and coral censuses are performed by divers in shallow waters shoreward of the diffuser pipe. Further out, at the diffuser where the depth of water makes diving hazardous, remotely controlled video cameras are used to monitor the fish and other animals.

In 1994 a supplemental study was added to the project. Livers removed from fish caught at sites around the outfall are analyzed for pathological changes to the cells that could be attributable to pollution.

The data collected are analyzed statistically, significant changes in any population observations or parameters of chemistry are noted, and the findings are reported to the EPA for their consideration.

SUMMARY OF OBSERVATIONS AT SAND ISLAND 1990-1995

POLYCHAETES

Polychaete abundance and species composition have remained stable over the years of study, with Station B3 (see figure 1 - Sand Island outfall) usually having fewer species and lower abundances than the other six stations. The only species to appear in large numbers at zone of initial dilution (ZID) stations Z and B3 from 1987 (even before the monitoring period reported here) to 1992 was Neanthes arenaceodentata, but its numbers declined and it was not found at Station B3 in 1993 and 1994. Only three individuals of this species were present in 1994 and 1995. A smaller species, Ophyotrocha spA become abundant at some of the ZID stations in 1995.

CORAL REEF STUDY

Analysis of the five years of data collected from the six permanently marked transects at the coral reef stations shows that there has been no statistically significant change in the following biological measures: percent coral cover, number of invertebrate species, total number of invertebrates, number of fish species, total number of fish, and biomass of fishes present at each station. The mean number of coral species has shown a statistically significant increase over the five-year period. Hurricane Iniki, which occurred in September 1992, impacted marine communities along the south shore of O'ahu. Coral communities received considerable damage, especially at the westernmost study site. Recovery in these communities is evident from the data collected since the storm.

CRUSTACEANS

Dr. William J. Cooke

The crustacean community in the area of the Sand Island outfall is the least diverse of the three south shore outfalls monitored , with 68 taxa collected through 1994. The average yearly collection has included approximately 37 taxa. Typically, Sand Island stations have between 5 and 19 taxa. The only outfall effect appears to be at Station B3, which has consistently been lowest (except in 1992 when it was second lowest) in diversity. Other stations which might be expected to experience some effects from the outfall (such as Station Z) have shown reasonable diversity since 1990. Whatever impact the outfall may be having on crustacean populations, it appears to be restricted to the area immediately adjacent to the end of the outfall pipe.

Dr. E. Alison Kay, University of Hawaii, Department of Zoology

The patterns of abundance and species composition of the benthic assemblages of micromollusks were repeated year after year between 1990 and 1994 in a series of peaks and valleys, each peak or valley marking one of the seven stations and showing impressive stability, but neither peaks nor valleys appear to reflect the influence of the wastewater outfall. The most abundant micromollusks are three species of epifaunal detritivores and the sea cucumber parasite Balcis. Mollusk abundance is consistently greatest at station B2 with a lesser abundance peak at B4; relatively more species are collected at the easternmost stations, B5 and B6. Station B1 is recognizable as the only station with large numbers of the microgastropod Finella pupoides.

Click on this picture to see a graph of mollusk counts at the Sand Island sampling stations from 1986 to 1995

Dr. Richard E. Brock, University of Hawaii, Hawaii Institute of Marine Biology

Because the Sand Island Ocean Outfall diffuser lies at depths below safe diving limits, remotely controlled video cameras have been used annually since 1991 to inspect the marine communities along the pipe. This system provides data which are difficult to quantify, and many uncontrollable variable factors such as weather, water clarity, winds, and currents can dramatically affect the quality of the videotapes. Other difficulties inherent in the remote video system include poor camera resolution, constantly changing camera angle, small fish sizes, and the fishes' nature to flee from the approaching camera. Nevertheless, the tapes are useful in affording the researchers a qualitative perspective on communities in the deep water along the diffuser pipe. Five permanent transects have been established along the 1,036-meter-long diffuser. These cover about 40% of the total length of the pipe. The 1992 tape showed an increase in number of species, number of individuals, and total biomass over 1991. The 1993 tape showed a decrease in these parameters from the previous year. In 1994 these numbers rose again. Changes in the mean numbers of fish between these time periods were statistically significant, but changes in biomass were not. Starting in the year 2000 the ROV studies will be discontinued at the Sand Island outfall as the EPA believes that the data already collected is sufficient.

FISH LIVER HISTOPATHOLOGY

Dr. James A. Brock, Department of Land and Natural Resources

Chronic exposure to cancer-inducing chemicals has been associated with the increased occurrence of skin and liver tumors in wild fish populations. The shelter and protection from predators afforded by the outfall and diffuser pipes have resulted in a relatively high fish population density around the outfall. Necropsy was carried out in 1992, 1994, and 1995 on fish collected along the Sand Island Ocean Outfall diffuser to determine if tumors indicative of exposure to cancer-inducing chemicals are occurring on fish exposed to the effluent. No skin or liver neoplasms were found in the 71 fish representing six species examined.

DATA ANALYSIS

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