Marine Environmental Research 161 (2020) 105118 Available online 17 August 2020 0141-1136/© 2020 Elsevier Ltd. All rights reserved. Larvae of the South Atlantic coral Favia gravida are tolerant to salinity and nutrient concentrations associated with river discharges Cristiano M. Pereira a, b, * , Juliana S. Fonseca c , Edney S. Paiva d , Patrícia G. Costa c , Miguel Mies a, e , Allison G. Silva a, d , Emiliano N. Calderon a, f , Adalto Bianchini a, c , Clovis B. Castro a, b a Instituto Coral Vivo, R. dos Coqueiros 87, Parque Yaya, Santa Cruz Cabr´ alia, BA, Brazil b Departamento de Invertebrados, Museu Nacional, Universidade Federal do Rio de Janeiro, Quinta da Boa Vista, S˜ ao Crist´ ov˜ ao, Rio de Janeiro, RJ, Brazil c Instituto de Ciˆ encias Biol´ ogicas, Universidade Federal do Rio Grande, Av. It´ alia Km 8, Rio Grande, RS, Brazil d Instituto Federal de Educaç˜ ao, Ciˆ encia e Tecnologia da Bahia, Rod. BR 367 Km 57,5, Porto Seguro, BA, Brazil e Instituto Oceanogr´ afco, Universidade de S˜ ao Paulo, Praça do Oceanogr´ afco 191, S˜ ao Paulo, SP, Brazil f Instituto de Biodiversidade e Sustentabilidade, Universidade Federal do Rio de Janeiro, Av. S˜ ao Jos´ e Barreto 764, Maca´ e, RJ, Brazil A R T I C L E INFO Keywords: Energy metabolism Nearshore reef Pollution Reef-building Settlement Stress-tolerant ABSTRACT Rivers release freshwater, nutrients and pollutants into reefs. This type of environmental stress reduces coral larvae settlement and alter its energy metabolism. We investigated the tolerance of Favia gravida (Scleractinia) larvae to river discharges. We exposed larvae to (i) different salinities (25, 30, 35 and 40 PSU); and (ii) dilutions of river water containing nutrients and metals (0, 20, 40, 60, 80 and 100% river water) under control salinity of 35 PSU. We then examined settlement and larval enzymatic activity. No differences in settlement were detected among salinities. Settlement was also similar to control for larvae under 100% river water. Enzymatic activity for citrate synthase remained unaltered for all treatments. Lactate dehydrogenase activity was slightly altered under different salinities, suggesting a mild stress response. Findings suggest that F. gravida larvae are tolerant to a wide range of salinity and nutrient conditions and that this is a stress-tolerant species. 1. Introduction Although reef-building corals are usually intolerant to salinity vari- ations (Sheppard et al., 2018), there are many coral reefs that develop under the constant or seasonal infuence of river discharges (Wolanski et al., 1984; Moberg et al., 1997; West and van Woesik, 2001). Besides freshwater, rivers are also the main source of nutrients, sediments and pollutants for coastal reefs (van Dam et al., 2011). Together, these ele- ments produce a variety of potentially adverse effects on coral com- munities, including impaired photosynthetic activity, macroalgal growth, siltation and smothering, and metal contamination (Holthus et al., 1989; Telesnicki and Goldberg, 1995; Fabricius and Wolanski, 2000; Ramos et al., 2004; Fabricius, 2005; De’ath and Fabricius, 2010). Few adaptations against the infuence of freshwater and suspended particles have been reported for reef-building corals, mainly associated with sediment-cleaning and increased heterotrophic feeding (Riegl, 1995; Mies et al., 2018). As a consequence, nearshore and naturally turbid reefs tend to display lower coral cover and diversity than offshore reefs, with communities comprised of fast-growing and stress-tolerant species (Kleypas, 1996; Anthony, 2006; Golbuu et al., 2011; Cacciapa- glia and van Woesik, 2016). River discharges are also reported to affect the early developmental stages of both nearshore and offshore coral populations. Their main effects include reduced gametogenesis and fecundity, and lower larval survival and settlement rates, all of which are mostly caused by nutrient enrichment, reduced salinity and increased sediment load (Tomascik and Sander, 1987; Edmunds and Davies, 1989; Wittenberg and Hunte, 1992; Gilmour, 1999; Gleason and Hoffman, 2011). River discharges also affect the larval metabolism because of the additional energy required to recover and maintain homeostasis (Sokolova et al., 2012; Sokolova, 2013). Although not yet addressed specifcally for the stress induced by river discharges, there are several different metabolic changes in coral larvae caused by environmental stress. These include variations in oxygen consumption, expression of antioxidant enzymes, * Corresponding author. Universidade Federal do Rio de Janeiro, Museu Nacional, Quinta da Boa Vista, S˜ ao Crist´ ov˜ ao, 20940-040, Rio de Janeiro, RJ, Brazil. E-mail address: cristianomp@gmail.com (C.M. Pereira). Contents lists available at ScienceDirect Marine Environmental Research journal homepage: http://www.elsevier.com/locate/marenvrev https://doi.org/10.1016/j.marenvres.2020.105118 Received 28 April 2020; Received in revised form 24 July 2020; Accepted 12 August 2020