A large variety of traditional contaminants including metals, hydrocarbons, halogenated hydrocarbons and pesticides, and emerging compounds (pharmaceuticals, personal care products, plastics, and nanoparticles) are generally found in the marine environment. These compounds are of special concern due to their intensive use and threats they can cause to the aquatic environment and human health. Moreover, climate change can also have an additional impact on the effects of these compounds. Due to the complex nature of these stressors, a great deal of research has been carried out to develop the best analytical technologies for the detection of these compounds in the aquatic environment and for assessing their biological effects.

This special issue is a collection of key articles addressing field and analytical aspects of multiple stressors in the aquatic environment presented to the 17th meeting on pollution Responses in Marine Organisms (PRIMO17) held at the University of Algarve (Portugal) from the fifth to the eighth of April 2013. This International Symposium series, Pollutant Responses in Marine Organisms (PRIMO) began in 1981 with a small group of NSF-funded researchers from Woods Hole Oceanographic Institution and from Plymouth Marine Laboratory who were addressing questions related to Chemical Effects and the Health of the Ocean. The first PRIMO Symposium was held in Plymouth, UK, in 1981 and addressed the mechanistic aspects of the same topic with the goal of stimulating international scientific interactions in this area. The success of the first PRIMO meeting led to biennial meetings held alternately in Europe, the USA, and South America. PRIMO meetings have been held in 13 cities of 8 countries: the UK (Plymouth 1981, 1985, 1989, 2001), the USA (Woods Hole, MA 1983, 1987, 1991; Asilomar Monterey, CA 1995; Williamsburg, VA 1999; Tampa, FL 2003 and Long Beach, CA, 2011), Sweden (Goteborg, 1993), Norway (Bergen, 1997), Italy (Alessandria, 2005), Brazil (Florianópolis, 2007), and France (Bordeaux, 2009). Although the word “marine” was used to produce the memorable acronym, the research presented has never distinguished between marine and freshwater, and always included research results from marine and freshwater organisms. The overall theme of PRIMO17 was dedicated to the impacts of large scale problems such as Ocean and Human Health, global climate change, ocean acidification, effects of multiple stressors from emerging contaminants to nanoscale materials, and mechanistic effects of toxicity from ecosystem scale to the exposome (www.cima.ualg.pt/primo17).

The meeting was characterized by the following major scientific themes: climate change; ocean acidification; emerging compounds (nanomaterials, pharmaceuticals, personal care products (PPCPS)); combination effects of multiple stressors; detection and monitoring of deliberately dumped chemicals at sea; endocrine disruption; cellular absorption, distribution, metabolism, and elimination; tissue levels and immune responses; biomarkers; ecotoxicology of large marine vertebrates; exposome and exposomics; geno- and phenotoxicity; epigenetic; computation toxicology; ecosystem-level effects; and environmental assessment.

PRIMO17 brought together more than 350 participants including academics, researchers, professionals, and policymakers from 32 countries of all continents, 36 % of which were young scientists. These are outstanding numbers when compared with previous PRIMO meetings, clearly reflecting the dynamism and scientific quality of these meetings.

The outcome of the discussions on the advancement of the understanding of the effects of multiple stressors in the marine environment will contribute to advise decision-makers on the policy to improve the quality of the aquatic environment.

We look forward to the next meeting to be held in Norway in 2015.