Benthic faunal sampling adjacent to the Sand Island ocean outfall, Oahu, Hawaii, 1986-2010 (NODC Accession 9900088)

Benthic fauna in the vicinity of the Sand Island ocean outfall were sampled from 1986-2010. To assess the environmental quality, sediment grain size and sediment chemistry were measured. To identify the fauna, mollusk species and non-mollusk species sitings were tabulated. Stations were located both within and on the boundary of the zone of initial dilution (ZID) and at distances of 1.2 to 2 km from the ZID boundary. In summary, the response patterns of benthic fauna near the Sand Island ocean outfall showed little or no indication of a strong influence by the diffuser effluent.

The sampling methodology used in this study generally followed the recommendations of Swartz (1978) and US EPA guidelines(EPA 1987a, 1987b), hereafter refered to as EPA procedures.

A modified 0.16-m2 van Veen grab sampler deployed from a stern-mounted A-frame on the research vessel Noi I Kai was used to obtain bottom samples at all seven stations. Penetration of the sampler was adequate for all replicates. The minimum penetration depth for all grabs was 6 cm and the maximum was 13 cm.

Six van Veen grabs were taken at each station. A subsample 7.6 cm in diameter by 5 cm deep was taken from each grab sample for infaunal analysis and a subsample 4.8 cm in diameter by 5 cm deep for mollusk analysis. Subsampling was necessary because the epifauna and infauna in the area are known to be both small and abundant and processing of the entire sample would be impractical. Replicated grab samples at each station, rather than replicated subsamples from one grab sample, were used to provide information on intrastation variability. All six nonmollusk subcores were processed on a 0.5-mm screen.

Samples for geochemical analyses (total organic carbon (TOC), oxidation-reduction potential (ORP), sediment oil and grease (O&G), total Kjeldahl nitrogen (TKN), and grain size) were obtained from the grabs from which the biological subcores were taken. Each replicate van Veen grab contained more than enough sediment for both purposes (methods HI0020117). Three subsamples 7.6 cm in diameter by 5 cm deep (one from each of three differnt grab samples) were taken from all stations. The top 2 cm of sediment of each subsample were used for geochemical analysis. Samples for TOC and sediment O&G analysis were put in screw-cap jars, placed on ice, and taken to the laboratory for analysis. Sediment analyses of sediment grain size, ORP, TKN, and O&G followed EPA procedures. Analysis of TOC was carried out by Severn Trent Laboritories (Colchester, Vermont), using the modified Lloyd Khan method, which utiliezes an infrafred detector to measure carbon dioxide. Inorganic carbon was removed from the samples by treating them with a 1:1 solution of hydrochloric acid prior to TOC analysis.

1986年至2010年间，对桑迪岛（Sand Island）海洋排污口附近的底栖动物（benthic fauna）开展了采样工作。为评估环境质量，研究人员测定了沉积物粒径与沉积物化学特征。为鉴定底栖动物类群，研究人员对软体动物（mollusk）物种与非软体动物物种的出现记录进行了制表统计。采样站位设置在初始稀释区（zone of initial dilution, ZID）内部、边界处，以及距ZID边界1.2至2公里的区域。综上，桑迪岛海洋排污口附近底栖动物的响应模式几乎未表现出扩散器排放物的显著影响。

本研究采用的采样方法总体遵循了Swartz（1978）的建议与美国环境保护署（United States Environmental Protection Agency, US EPA）指南（EPA 1987a、1987b），下文统称为EPA标准流程。

本研究使用改装后的0.16平方米范维恩采泥器（van Veen grab sampler），搭载于研究船“Noi I Kai”的船尾A型架上，在全部7个站位采集底质样品。该采泥器的插入深度满足所有重复采样的要求，所有采泥样品的最小插入深度为6厘米，最大为13厘米。

每个站位采集6个范维恩采泥样品。从每个采泥样品中分别截取直径7.6厘米、深度5厘米的子样品用于底内动物（infaunal）分析，以及直径4.8厘米、深度5厘米的子样品用于软体动物分析。开展子采样是因为该区域的表栖动物（epifauna）与底内动物个体微小且数量繁多，处理全部原始样品并不现实。本研究采用各站位的重复采泥样品而非单一样品的重复子样品，以获取站位内的变异性信息。全部6个非软体动物子岩心均通过0.5毫米孔径的筛网进行分选处理。

用于地球化学分析的样品（总有机碳（total organic carbon, TOC）、氧化还原电位（oxidation-reduction potential, ORP）、沉积物油脂类污染物（sediment oil and grease, O&G）、凯氏总氮（total Kjeldahl nitrogen, TKN）及沉积物粒径）均取自采集生物子样品的采泥样品。每个重复采泥样品所获得的沉积物量均满足两项分析的需求（方法编号HI0020117）。从每个站位的3个不同采泥样品中分别截取直径7.6厘米、深度5厘米的子样品，共3份。取每份子样品的表层2厘米沉积物用于地球化学分析。总有机碳与沉积物油脂类污染物分析样品被装入螺旋盖罐中，置于冰上运至实验室进行分析。沉积物粒径、氧化还原电位、凯氏总氮及油脂类污染物的分析均遵循EPA标准流程。总有机碳的分析由佛蒙特州科尔切斯特的Severn Trent实验室完成，采用改良的Lloyd-Khan法，通过红外检测器测定二氧化碳含量。总有机碳分析前，需将样品用1:1体积比的盐酸溶液处理以去除无机碳。