Spatial Patterns and Temperature Predictions of Tuna Fatty Acids: Tracing Essential Nutrients and Changes in Primary Producers

Abstract

Fatty acids are among the least understood nutrients in marine environments, despite their profile as key energy components of food webs and that they are essential to all life forms. Presented here is a novel approach to predict the spatial-temporal distributions of fatty acids in marine resources using generalized additive mixed models. Fatty acid tracers (FAT) of key primary producers, nutritional condition indices and concentrations of two essential long-chain (≥C20) omega-3 fatty acids (EFA) measured in muscle of albacore tuna, Thunnus alalunga, sampled in the south-west Pacific Ocean were response variables. Predictive variables were: location, time, sea surface temperature (SST) and chlorophyll-a (Chla), and phytoplankton biomass at time of catch and curved fork length. The best model fit for all fatty acid parameters included fish length and SST. The first oceanographic contour maps of EFA and FAT (FATscapes) were produced and demonstrated clear geographical gradients in the study region. Predicted changes in all fatty acid parameters reflected shifts in the size-structure of dominant primary producers. Model projections show that the supply and availability of EFA are likely to be negatively affected by increases in SST especially in temperate waters where a 12% reduction in both total fatty acid content and EFA proportions are predicted. Such changes will have large implications for the availability of energy and associated health benefits to high-order consumers. Results convey new concerns on impacts of projected climate change on fish-derived EFA in marine systems.

Climate warming is predicted to reduce omega‐3, long‐chain, polyunsaturated fatty acid production in phytoplankton

“…Our data set, which contains a global distribution of phytoplankton, predicts that a global average estimate of 2.5 °C increase in water temperature could result in reductions of 8% and 28% for EPA and DHA, respectively. The mean of these estimates (~18%) is close to other model projections that indicate a 12% reduction in n‐3 LC‐PUFA supply as a result of increasing sea surface temperature (Pethybridge et al ., ). Diatoms, in particular, which contribute to most of the world's supply of EPA and DHA, may show a 6% reduction in EPA and 7% reduction in DHA production with a 2.5 °C increase in water temperature.…”

Fatty Acid Composition and Contents of Seven Commercial Fish Species of Genus Coregonus from Russian Subarctic Water Bodies

“…Among the ecological factors, water temperature was often regarded as a driver of the PUFA contents in fish. There are also some data on higher PUFA contents in wild fish in cold waters compared to those in warm waters [55,56]. For instance, Arts et al [54] found that under a laboratory conditions an increase of water temperature from 12 to 19 °C caused a decrease of DHA content in juvenile Atlantic salmon (Salmo salar) from 4.6 to 3.3 mg g −1 wet weight (recalculated from dry weight using mean moisture content in Salmoniformes 72.5%).…”

“…For instance, Arts et al [54] found that under a laboratory conditions an increase of water temperature from 12 to 19 °C caused a decrease of DHA content in juvenile Atlantic salmon (Salmo salar) from 4.6 to 3.3 mg g −1 wet weight (recalculated from dry weight using mean moisture content in Salmoniformes 72.5%). There are also some data on higher PUFA contents in wild fish in cold waters compared to those in warm waters [55,56]. However, other authors did not find any significant effect of water temperature on the PUFA levels in fish in a laboratory or in natural waters [18,[57][58][59][60][61].…”

Content of highly unsaturated fatty acids in fish from rivers of contrasting temperature

“…As a result, our first hypothesis, which fish species in the cold river have higher EPA and DHA contents in their tissue than fish species from the warm rivers, was not confirmed. Many authors in experimental and field studies did not find any effect of water temperature on EPA and DHA contents in fish (Gokce et al, ; Laurel et al, ; Murzina et al, ; Wijekoon et al, ; Gribble et al, , but see Wall et al, ; Arts et al, ; Pethybridge et al, ). Our study represented the combination of experimental and field approaches, and its results supported laboratory and field findings, which water temperature does not determine the contents of the essential HUFAs.…”

“…Moreover, many authors question the role of EPA and DHA in homeoviscous adaptation compared with that of other fatty acids such as mono‐unsaturated and short‐chain saturated fatty acids (Arts & Kohler, ; Dymond, ; Stillwell & Wassall, ). Concerning natural conditions, some authors reported an increase of EPA and DHA in fish from cold waters compared with those from warmer waters (Pethybridge et al, ; Wall, Ross, Fitzgerald, & Stanton, ). In contrast, other authors have not reported an increase of these HUFA in relatively cold habitats and seasons (Gokce, Tasbozan, Celik, & Tabakoglu, ; Gribble et al, ; Murzina et al, ).…”