Continuous water quality monitoring to determine the cause of coral reef ecosystem degradation for coastal Windward Oahu streams during 2002 (NODC Accession 0001070)

Waimanalo Stream was sampled along the Kahawai tributary and below the confluence of Kahawai and Waimanalo Streams near the mouth of the stream where it discharges into Waimanalo Bay. Most of the Waimanalo Stream stations were sampled a total of 10-12 times at roughly 3-4 week time intervals during the period February-October, 2002. Kaneohe Stream sampling was carried out at roughly three-week intervals during the period June-November, 2002. Most Kaneohe Stream stations were sampled a total of nine times. Waimanalo stations 2-5 and 7 lie along a hardened section of the stream that extends for a distance of approximately 0.8 km upstream and immediately downstream of Kalanianaole Highway. Station 1 lies immediately upstream of the hardened section. Station 6 is the effluent from an underground storm sewer that discharges beneath the Kalanianaole Highway bridge. Stations 7-9 lie at the beginning, midpoint, and end, respectively, of a stream restoration project carried out by the Waimanalo Watershed Project. Station 10 is at the head of the Waimanalo Stream estuary. In the Kaneohe Stream study, station 1 is located in a natural stream channel with no upstream hardening. Station 5 is the effluent from a spring that seeps into Kamooalii Stream near the Likelike Highway culvert. Station 10 is immediately downstream of the hardened section of the stream in the head of the Kaneohe Stream estuary. The remaining stations are located along the hardened section of Kamooalii/Kaneohe Stream. Water samples were collected in 250-ml plastic bottles and immediately placed in an ice chest. Measurements of temperature, pH, oxygen concentration, and turbidity were made in the field. Temperature was recorded to the nearest 0.1oC with a thermometer calibrated at 0oC (ice bath) and 100oC (boiling water). Oxygen concentrations were recorded with a YSI model 58 dissolved oxygen meter. pH was recorded to the nearest 0.1 using an IQ Scientific model 3000 portable pH meter. In the laboratory, the water samples were filtered through pre-weighed glass fiber filters (Whatman GFF) with a nominal porosity of 0.7 ?m. The filters were dried in a drying oven at 105oC to constant weight. The filters were weighed on a Mettler model H20T analytical balance to the nearest 0.01 mg. Duplicates were run on random samples as a check on precision. Blanks were run by filtering 250 mL of distilled water through a filter. The weight of material collected on the filters ranged from a few milligrams to several tens of milligrams. The blank correction was less than 0.1 mg. The concentration of total suspended solids (TSS) was calculated from the difference in the weights of the filter before and after filtering. The filtrate from the suspended solids filtration step was transferred to plastic bottles and processed for nutrient concentration measurements. The filtrates were frozen if not immediately analyzed. Concentrations of nitrate + nitrite (hereafter, nitrate), phosphate, and silicate were measured on the filtrate using colorimetric techniques on a Technicon Instruments AutoAnalyzer. The procedures used for the colorimetric assays adhered to those described in APHA (1998). Limits of detection were 0.5 ?M for silicate and 0.1 ?M for nitrate and phosphate. Concentrations of total dissolved nitrogen (TDN) and total dissolved phosphorus (TDP) were determined by first oxidizing the filtrates with an Ace-Hanovia ultraviolet light photo-oxidation unit and then assaying for nitrate and phosphate, respectively. Concentrations of particulate nitrogen (PN) and particulate phosphorus (PP) were calculated by assuming that the TSS contained 0.35% nitrogen and 0.11% phosphorus byweight (Laws and Ferentinos 2002). Concentrations of total nitrogen (TN)and total phosphorus (TP) were then calculated as TDN + PN and TDP + PP,respectively.