Detecting the presence of fish farm-derived organic matter at the seafloor using stable isotope analysis of phospholipid fatty acids

Abstract

The expansion of global aquaculture activities is important for the wellbeing of future generations in terms of employment and food security. Rearing animals in open-exchange cages permits the release of organic wastes, some of which ultimately reaches the underlying sediments. The development of rapid, quantitative and objective monitoring techniques is therefore central to the environmentally sustainable growth of the aquaculture industry. Here, we demonstrate that fish farm-derived organic wastes can be readily detected at the seafloor by quantifying sediment phospholipid fatty acids (PLFAs) and their carbon stable isotope signatures. Observations across five farms reveal that farm size and/or distance away from it influence the spatial distribution of the generated organic wastes and their effect on benthic bacterial biomass. Comparison to the isotopic signatures of fish feed-derived PLFAs indicates that 16:0 and 18:1(n-9) are potential biomarkers for fish farm-derived organic wastes. Our results suggest that stable isotope analysis of sediment PLFAs has potential for monitoring the environmental performance of aquaculture activities, particularly given the increasing prevalence of terrigenous organic matter in aquaculture feed stocks because it is isotopically district to marine organic matter.

Marine Aquaculture Impacts on Marine Biota

“…Likewise in our study, the sedimentary OM was depleted under fish cages compared to the reference, in Tasmania (Ye et al, 1991). Mayor et al (2017) reported that phospholipid fatty acid (PLFA) extracted from surficial sediments in five Scottish fish farms also showed a trend to more depleted δ 13 C values with increasing farm size and production. Contrary, Yokoyama et al (2006), , and Callier et al (2013) did not find a clear trend in δ 13 C of sedimentary OM in relation to fish farming in Japan, Spain, Greece, Italy, and Ireland.…”

“…The stable isotopes were used to reveal the impact of fish rearing on the environment in several studies (Ye et al, 1991;Sara et al, 2006;Landrum and Montoya, 2009). According to Mayor et al (2017) the analysis of the carbon stable isotopes of bulk sediment represents an alternative and fast approach to quantify the fate of fish farmderived organic matter. Moreover, the isotopic signature of the fish feed pellets can be distinct from the local sources, as they are composed of terrestrial material and fishmeal originating from other seas (Moreno-Rojas et al, 2008).…”

The Depleted Carbon Isotopic Signature of Nematodes and Harpacticoids and Their Place in Carbon Processing in Fish Farm Sediments

“…Likewise in our study, the sedimentary OM was depleted under fish cages compared to the reference, in Tasmania (Ye et al, 1991). Mayor et al (2017) reported that phospholipid fatty acid (PLFA) extracted from surficial sediments in five Scottish fish farms also showed a trend to more depleted δ 13 C values with increasing farm size and production. Contrary, Yokoyama et al (2006), Holmer et al (2007, and Callier et al (2013) did not find a clear trend in δ 13 C of sedimentary OM in relation to fish farming in Japan, Spain, Greece, Italy, and Ireland.…”

“…The stable isotopes were used to reveal the impact of fish rearing on the environment in several studies (Ye et al, 1991;Sarà et al, 2004;Sara et al, 2006;Holmer et al, 2007;Landrum and Montoya, 2009). According to Mayor et al (2017) the analysis of the carbon stable isotopes of bulk sediment represents an alternative and fast approach to quantify the fate of fish farmderived organic matter. Moreover, the isotopic signature of the fish feed pellets can be distinct from the local sources, as they are composed of terrestrial material and fishmeal originating from other seas (Moreno-Rojas et al, 2008).…”

A review of data collection methods used to monitor the associations of wild species with marine aquaculture sites

“…For FA analysis, fatty acid methyl esters (FAME) are created by homogenising tissue samples with chloroform and methanol and rinsing off non-lipid impurities. 98,170,174,175 The total lipids in FAME are then separated and quantified through a process such as gas-liquid chromatography (GLC), where peak retention times are measured against known FAME standards and FA composition can subsequently be expressed as a percentage of total lipid content. 164,175,176 These FA proportions present in the tissues can then be compared to feed pellets used at the aquaculture site to determine if wild species have been consuming significant amounts of fish feed.…”