The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Israel.
Institute of Soil, Water and Environmental Sciences, The Volcani Center, Agricultural Research Organization, Bet Dagan, Israel.
Water Res. 2017 Jan 1;108:412-421. doi: 10.1016/j.watres.2016.11.028. Epub 2016 Nov 8.
Recirculating aquaculture systems (RAS), offering many economic and fish husbandry benefits, are characterized by an accumulation of dissolved organic matter (DOM) and, specifically, humic substances (HS). As reported in a number of studies, HS may affect biological activity in both invertebrates and vertebrates. Given the accumulation of HS in RAS, it is therefore of great interest to characterize DOM and, specifically, its HS fraction in the RAS. The present study was aimed at characterizing long-term changes in fluorescent DOM composition in the culture water of RAS systems, which were operated in a novel, zero water exchange mode. Two such zero-discharge recirculating systems (ZDS) were examined: a freshwater system, stocked with hybrid tilapia (Oreochromis aureus x Oreochromis niloticus) and a marine system, stocked with gilthead seabream (Sparus aurata). Excitation-emission matrices (EEMs) of fluorescence, coupled with parallel factor analysis (PARAFAC), were used to characterize and quantify the different DOM components in the ZDS. In the culture water, one tryptophan-like and four HS-like components were identified. The fluorescence intensities of three of the HS-like components as well as the tryptophan-like component increased at comparable rates during ZDS operation while a much slower accumulation of these compounds was observed in a parallel operated, flow-through, freshwater aquarium. The ZDS examined in this study comprised a sludge digestion stage where a considerable accumulation of all fluorescent components was detected. A HS-like components and a tryptophan-like component in blood of tilapia from the freshwater ZDS were similar to components found in the culture water. Blood levels of both components were higher in fish cultured in the DOM-rich ZDS than in fish raised in the control, flow-through freshwater aquarium. Fluorescence of the HS-like component found in the fish blood increased also with time of ZDS operation. The finding that fish blood contains a HS-like fluorescent component may have important implications for the understanding of the physiological effects of HS in fish and the possible benefits of these substances in aquaculture.
循环水产养殖系统（RAS）具有许多经济和鱼类养殖优势，其特点是溶解有机物（DOM）的积累，特别是腐殖质（HS）的积累。正如许多研究报告的那样，HS 可能会影响无脊椎动物和脊椎动物的生物活性。鉴于 RAS 中 HS 的积累，因此对 DOM 进行特征描述，特别是对 RAS 中 HS 部分进行特征描述非常重要。本研究旨在对 RAS 系统养殖水中荧光 DOM 组成的长期变化进行特征描述，这些系统以一种新颖的、零水交换模式运行。检查了两个这样的零排放循环系统（ZDS）：一个淡水系统，饲养杂交罗非鱼（奥利亚罗非鱼×尼罗罗非鱼），一个海水系统，饲养金头鲷（真鲷）。采用激发-发射矩阵（EEM）与平行因子分析（PARAFAC）相结合的方法对 ZDS 中的不同 DOM 成分进行特征描述和定量分析。在养殖水中，鉴定出一个色氨酸样和四个 HS 样成分。在 ZDS 运行过程中，三个 HS 样成分和色氨酸样成分的荧光强度以可比的速度增加，而在平行运行的、流水式淡水水族馆中，这些化合物的积累速度要慢得多。本研究中检查的 ZDS 包括一个污泥消化阶段，在这个阶段检测到所有荧光成分的大量积累。来自淡水 ZDS 的罗非鱼血液中的一个 HS 样成分和一个色氨酸样成分与在养殖水中发现的成分相似。在富含 DOM 的 ZDS 中养殖的鱼类血液中这两种成分的含量都高于在对照、流水式淡水水族馆中饲养的鱼类。在 ZDS 运行过程中，发现鱼类血液中 HS 样成分的荧光也随时间增加。发现鱼类血液中含有 HS 样荧光成分可能对理解 HS 对鱼类的生理影响以及这些物质在水产养殖中的可能益处具有重要意义。
