METOXFISH

Metal pollution and fish larval recruitment in harbour environments

Project at a glance

2021-2022

Port-Vendres (FR)

Diplodus vulgaris

Ecotoxicology

Ecophysiology

Endocrinology

Context

Harbors are highly modified coastal environments that concentrate multiple anthropogenic pressures. Maritime activities, antifouling products, urban runoff and historical contamination can result in elevated concentrations of trace metals in harbor sediments and water. Yet harbor environments can simultaneously support large numbers of juvenile fishes and may constitute important nursery habitats for coastal species. This apparent paradox raises an important question:

Can these harbor environments function as a fish nurseries while exposing juveniles to contaminants capable of disrupting their development?

METOXFISH was developed to investigate this question in Port-Vendres harbor, using the two-banded seabream Diplodus vulgaris as a model species.

Objectives

A critical developmental window

At the end of their pelagic larval phase, Diplodus vulgaris larvae recruit into shallow coastal habitats and undergo metamorphosis. This transition involves coordinated changes in morphology, pigmentation, physiology and behavior and is regulated by endocrine pathways, particularly thyroid hormone signaling. Because endocrine and developmental systems can be highly sensitive to environmental contaminants, exposure to metals during recruitment may have biological consequences even when juvenile fishes remain abundant within harbor habitats. METOXFISH therefore investigates metal contamination not simply as an environmental chemistry issue, but as a potential developmental and endocrine stressor during a critical life-history transition.

Key questions

1. How heterogeneous is metal contamination within Port-Vendres harbor?

Port-Vendres contains areas exposed to different maritime activities and environmental conditions. METOXFISH compares larval and juvenile Diplodus vulgaris originating from four contrasted harbor sectors in which we explore levels of metal contamination. This spatial approach makes it possible to examine whether biological differences between fishes are associated with local environmental conditions within the same harbor.

2. Does harbour metal pollution affect juvenile phenotype and condition?

Throughout the recruitment season, newly recruited Diplodus vulgaris are sampled at regular intervals to characterise their developmental trajectory. We examine several complementary phenotypic traits, including:

body size and weight
body morphology
pigmentation patterns
developmental stage

By comparing fishes sampled across contrasting harbour areas, METOXFISH investigates whether environmental contamination is associated with altered growth or developmental phenotype.

3. Is endocrine regulation of metamorphosis affected?

Thyroid hormones play a central role in coordinating fish metamorphosis. METOXFISH therefore examines endocrinological markers in juvenile Diplodus vulgaris, including thyroid hormone levels and expression levels for genes associated with the larva-to-juvenile transition. This allows us to investigate whether exposure to harbor-associated contaminants may be associated with changes in the molecular controls, timing or progression of metamorphosis.

4. Can metals directly disrupt metamorphosis?

Correlations observed in wild fishes cannot by themselves establish causality. METOXFISH therefore also uses controlled experimental exposures to investigate the effects of environmentally relevant metals, particularly waterborne copper, on Diplodus vulgaris metamorphosis. By combining field observations with experimental ecotoxicology, the project aims to distinguish environmental associations from direct biological effects of contaminant exposure.

From environmental contamination to biological effects and ecological consequences

Coastal nurseries are essential for the renewal of marine fish populations, but many occur within or close to heavily urbanized environments. If juvenile fishes are attracted to or retained within contaminated habitats, high juvenile abundance may mask more subtle physiological or developmental effects. By investigating the effects of metal contamination during larval recruitment and metamorphosis, METOXFISH contributes to understanding the quality – rather than simply the occupancy – of anthropized fish nursery habitats. The project also provided a scientific foundation for subsequent work examining the broader consequences of harbor redevelopment within JUVAPORT.

Project team and partners

CEFREM - CNRS, Université de Perpignan Via Domitia

Philippe Lenfant - Coordinator
Carmen Palacios
Dominique Aubert
Gilles Saragoni
Nicolas Lucchini

BIOM - CNRS, Sorbonne Université

Laurence Besseau
Charles-Hubert Paulin

Funding

Office Français de la Biodiversité

METOXFISH
2021-2022

People involved in the EcoEvoDevo team

Laurence Besseau

Maître de Conférences

Related Publications

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