title: Spatio-Temporal Variation in Effects of Upwelling on the Fatty Acid Composition of Benthic Filter Feeders in the Southern Benguela Ecosystem: Not All Upwelling Is Equal.
abstract: Variability in mesoscale nearshore oceanographic conditions plays an important role in the distribution of primary production and food availability for intertidal consumers. Advection of nutrient rich waters by upwelling usually allows the proliferation of diatoms, later replaced by dinoflagellates. We examined upwelling effects on the fatty acid (FA) signature of a benthic intertidal filter feeder to identify its response to pulsed variability in food availability. The study took place in two contrasting seasons and at two upwelling and two non-upwelling sites interspersed within the southern Benguela upwelling system of South Africa. We investigated the FA composition of the adductor muscles and gonads of the mussel Mytilus galloprovincialis to assess how FA are apportioned to the different tissues and whether this changes between upwelling and non-upwelling conditions. In situ temperature loggers used to identify upwelling conditions at the four sites indicated that such events occurred only at the upwelling centres and only in summer. Tissues differed strongly, with gonads presenting a higher proportion of essential FAs. This could reflect the faster turnover rate of gonad tissue or preferential retention of specific FA for reproductive purposes. FA composition did not vary as a direct function of upwelling, but there were strong dissimilarities among sites. Upwelling influenced mussel diets at one upwelling site while at the other, the expected signature of upwelling was displaced downstream of the core of upwelling. Condition Index (CI) and Gonad Index (GI) differed among sites and were not influenced by upwelling, with GI being comparable among sites. In addition, FA proportions were consistent among sites, indicating similar food quality and quantity over time and under upwelling and non-upwelling conditions. This suggests that the influence of upwelling on the west coast of South Africa is pervasive and diffuse, rather than discrete; while nearshore retention or advection of upwelled water is critical and site-specific so that the effects of upwelling differ even among sites categorised as upwelling centres.
authors: Department of Zoology and Entomology, Rhodes University, Grahamstown, South Africa.|Department of Oceanography, Marine Research Institute, University of Cape Town, Rondebosch 7701, Cape Town, South Africa.
authors: Eleonora
authors: http://orcid.org/0000-0002-6144-6650
authors: E
authors: Puccinelli
authors: Department of Zoology and Entomology, Rhodes University, Grahamstown, South Africa.
authors: Christopher David
authors: CD
authors: McQuaid
authors: Department of Zoology and Entomology, Rhodes University, Grahamstown, South Africa.|Marine Research Institute, Department of Biological Sciences, University of Cape Town, Rondebosch 7701, Cape Town, South Africa.
authors: Margaux
authors: M
authors: Noyon
mesh_terms: D000818:Animals; D017753:Ecosystem; D005227:Fatty Acids / Q000032:analysis*; D006066:Gonads / Q000502:physiology; D049878:Mytilus / Q000502:physiology; D012098:Reproduction / Q000502:physiology; D013019:South Africa; D013696:Temperature
chemical_list: D005227:Fatty Acids