Vulnerability of tropical coastal ecosystems to eutrophication

Home institute : CNRS Ecology & Environment

Country of cooperation: Brazil

Website :

1. Introduction

The coastal environment is made up of ecosystems of great scientific, ecological and economic interest, under increasing pressure from various forcings linked to climate or land use. In tropical countries, very large agglomerations continue to spread along the coast, while wastewater treatment rates are generally very low. These massive discharges of organic matter and nutrients impact biodiversity, cause drastic changes in the biogeochemical and ecological functioning of aquatic environments and impair ecosystem services for these developing societies. Perception of the issues involved in preserving the oceans and marine resources is often more fragmented in southern societies, with urban populations less aware of the exact nature of the problems, and local and federal authorities dealing with other political, economic and social emergencies. While continuing to warn of the need to preserve ecosystems and invest in water purification, academic research must also adapt thematically to the reality of eutrophication, as a dominant forcing on ecosystems in space and time. Describing and understanding the phenomena at work within ecosystems enables us to predict their evolution on different spatial and temporal scales, and to prioritize actions for the future, with the aim of optimizing their effectiveness given the limited resources available. Raising awareness, particularly among the younger generation, of the challenges posed by what is still “invisible” pollution for many, is also of strategic importance for the future of these companies, which would benefit greatly from turning more to the sea.

2. Missions and research topics

The aim of the VELITROP International Research Program (IRP) is to structure Franco-Brazilian research in marine ecology and biochemistry around the issue of eutrophication in tropical coastal ecosystems. The scale of the disturbances and the specific climatic and geomorphological features of its coastline call for conceptual and methodological approaches specific to the tropical environment. The project is based on the complementary skills of the Brazilian and French proposing teams, several members of which have been working closely together for some ten years. With its high population density and diversity of ecosystems, and thanks to the history of the Brazilian partners’ research, the coastline of the State of Rio de Janeiro is a privileged field of study for tackling the main scientific questions linked to eutrophication. However, comparisons are planned with ecosystems in Brazil’s northeastern states with different levels of contamination, notably in Céara. Drawing on the history of environmental conditions in the region’s coastal ecosystems, research will focus on the key mechanisms by which eutrophication alters biogeochemical cycles in tropical coastal environments:

  • Nutrient storage and removal in interconnected ecosystems and the cascading response of planktonic and benthic primary producer communities and CO2 and CH4 fluxes ;
  • Changes in the trophic resources of filter-feeding bivalve molluscs, used as eutrophication biosensors;
  • Vulnerability of blue carbon stocks in mangrove soils through fine characterization of sources and biodegradability of organic matter and heterotrophic microbial activity;
  • Alteration of microbial mat metabolism and impact on carbonate chemistry and biocalcification in hypersaline lagoons.

The IRP VELITROP also aims to promote knowledge of environmental issues relating to the coast to a wide audience in Carioca, particularly young people from disadvantaged backgrounds and coastal users, through thematic and sporting days involving a wide network of players (schools, social players in the favélas, coastal users (fishing and boating), conservation units, etc.).

IRP is structured around three research themes:

  1. Spread of eutrophication at the continent-ocean interface
  2. Blue carbon vulnerability of mangrove soils
  3. Microbiology, carbonate chemistry and biocalcification in hypersaline lagoons

3. Main research projects

VuBleu “Vulnerability of blue carbon in mangroves to eutrophication” LEFE-INSU project 2019-2020

Impact of eutrophication on the capacity of mangroves to store blue carbon: understanding and prevention. Project funded by the TOTAL Foundation, 2020-2022

4. Institutions and laboratories involved

In France :

  • CNRS
  • Muséum National d’Histoire Naturelle
  • Sorbonne Université
  • Université d’Angers
  • Université des Antilles
  • L’Université de Lille
  • Université du Littoral Côte d’Opale

In Brazil :

  • Universidade Federal Fluminense (UFF)
  • Universidade Estadual do Estado do Rio de Janeiro (UERJ)
  • Universidade Federal do Ceará (UFC)

The associated laboratories are :

  • Biologie des Organismes et Ecosystèmes Aquatiques (BOREA) – FRE 2030
  • Laboratoire de Planétologie et Géodynamique (LPG) – UMR 6112
  • Laboratoire d’Océanologie et de Géosciences (LOG) – UMR 8187
  • Programa de pós-graduação em Geoquímica (UFF)
  • Programa de pós-graduação em Biologia Marinha (UFF)
  • Departamento de Ocenaografia fisica e meteorologia, faculdade de Oceanografia (UERJ)
  • Instituto de Ciências do Mar – Labomar (UFC)


    • Gwenaël Abril, Coordinator France