Ecological Indicators 69 (2016) 284–294 Contents lists available at ScienceDirect Ecological Indicators jo ur nal ho me page: www.elsevier.com/locate/ ecolind Seasonal and spatial shifts in copepod diets within tropical estuaries measured by fatty acid proﬁles Gustavo Correia de Moura a,∗ , José Etham de Lucena Barbosa b , Joana Patrício c , Janiele Franc ¸ a Nery d , Ana Marta Mendes Gonc ¸ alves c,e a Postgraduate Program in Ecology and Conservation, Paraíba State University, 58429-500 Campina Grande, Brazil b Department of Biology, Paraíba State University, 58429-500 Campina Grande, Brazil c MARE (Marine and Environmental Sciences Centre), Faculty of Sciences and Technology, University of Coimbra, 3004-517 Coimbra, Portugal d Postgraduate Program in Ecology of Aquatic Environments (PEA), Nucleus of Limnology Research, Ichthyology and Aquiculture (Nupélia), Maringa State University, 87020-4040 Paraná, Brazil e Department of Biology and CESAM, University of Aveiro, 3810-193 Aveiro, Portugal a r t i c l e i n f o Article history: Received 29 September 2015 Received in revised form 15 April 2016 Accepted 20 April 2016 Keywords: Zooplankton Feeding ecology Food quality Bio-indicator Brazil a b s t r a c t Fatty acids are the main components of lipids and are necessary for the production and permeability of cell membranes, playing an essential role in the physiological responses of organisms. The biochemical composition of zooplankton might be used as bio-indicators of the trophic status of aquatic ecosystems. Aiming to ﬁll the gap of knowledge in tropical estuaries, the main aim of this study was to test if the fatty acid proﬁles can reveal spatial and temporal shifts in the diet of copepods and therefore can be used as indicators of the trophic status of estuarine systems. We investigated the fatty acids composition of copepod species and their possible food sources along the salinity gradient of two tropical estuaries (Paraíba do Norte and Mamanguape estuaries, northeastern Brazil), during the rainy and dry seasons. We found clear seasonal differences regarding fatty acids composition and concentration in copepods, with maximal concentrations and diversity of total fatty acids during the rainy season. The copepods species were mainly carnivorous in the dry season and omnivorous in the rainy season and, in both estuaries, the diet of most copepods was dependent on food availability. The fatty acid proﬁles suggest that, in general, feeding patterns of zooplankton change spatially and temporally, reﬂecting the shifts in their food sources abundance (i.e., dominance among diatoms and ﬂagellates, terrestrial detritus and small animals). We observed a residual proportion of terrestrial detritus and green algae in the diets and these items were only present in the dry season. Furthermore, the food sources in the Paraiba do Norte estuary, a system with high levels of anthropogenic disturbance, showed lower feeding quality, with lower essential fatty acids concentrations. Our study showed that fatty acid proﬁles can be used as ecological indicator to assess seasonal and spatial shifts in the trophic ecology of copepods in tropical estuaries and to distinguish systems with different levels of human impact in a fast and accurate way. © 2016 Elsevier Ltd. All rights reserved. 1. Introduction Estuaries are located at the interface between the continental and marine domains and represent one of the most productive ecosystems worldwide (David et al., 2005; Isari et al., 2007). This productivity is associated with unique characteristics, such as the environmental ﬂuctuations to which these transitional ecosystems are subjected (e.g., changes in the marine and freshwater inﬂuxes, accumulation of organic matter and nutrients that stimulate ∗ Corresponding author. Tel.: +55083991874847. E-mail address: gustavocorreia2@gmail.com (G.C.d. Moura). productivity, etc.). Plankton (and mainly zooplankton) is known to be particularly sensitive to these variations because it is strongly inﬂuenced by climatic features and changes in hydrological condi- tions (Beaugrand et al., 2000; Ara, 2001). Zooplankton play a crucial role in converting plant food into an animal food source, and are in turn fed upon by organisms from higher trophic levels, which gives them a key position and a considerable trophic importance. Indeed, some authors (e.g., Borja et al., 2009) have emphasized its potential as an aquatic bio-indicator group of trophic status in terms of water quality. Copepods are the dominant group of zoo- plankton and are capable of utilizing a wide range of diets (Kleppel, 1993), playing a key role in the food web as they form a link between primary producers and secondary consumers (Richmond http://dx.doi.org/10.1016/j.ecolind.2016.04.037 1470-160X/© 2016 Elsevier Ltd. All rights reserved.