Exposure to contaminated sediments induces alterations in the gill epithelia in juvenile Solea senegalensis: a comparative in situ and ex situ study
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1
IMAR - Instituto do Mar, Departamento de Ciências e Engenharia do Ambiente, Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa, Portugal
The loss of biodiversity in aquatic ecosystems is a major problem for society, with very significant ecological and economic deleterious effects. Estuaries, as the Sado Estuary (SW Portugal), are fragile ecosystems always associated to multiple anthropogenic stressors, such as heavy industry, shipping and agricultural activities, which can affect biodiversity and, therefore, environmental health, as well as the local economy, through its impact on fisheries. In the Sado Estuary there are many important commercial fish species that support a significant part of the local communities. As such, fish population are continuously exposed to pollutants that can have repercussions in the animals’ physiology and survival. This estuary is characterized by its multiple sources of toxicants, which is reflected onto a complex pattern of sediment contamination. In order to evaluate the physiological effects onto an important commercial species in the Sado Estuary, juvenile Solea senegalensis were subjected to a series of in and ex situ sediment-based bioassays, since this flatfish, being benthic, is particularly exposed to sediment-bound pollutants. Histological alterations in gill epithelia were taken as the main endpoint, since this is the main apical entry organ of toxicants. Sediment contaminants, mostly adsorbed to fine particles and organic matter, namely organochlorides, PAHs and same metals, presented a relation with alterations in gill epithelia. Even though no significant gross histopathological lesions were found, the animals exposed to sediments from the most polluted sites presented physiological alterations, when compared to those exposed to sediments from a reference site. These alterations were particularly related to the number of mucous cells and hypertrophied chloride cells per interlamellar space. These changes imply physiological hampering of normal gill functions and, therefore, affect the health status of animals exposed to contaminated sediments. Hypertrophied chloride cells are a consequence of a hindered osmotic regulation by the impairment of ionic active transport, leading to loss-of-function and excessive fluid retention in the cytoplasm. On its turn, a reduction in number and size of gill mucous cells likely reduced the protection provided by mucous to these delicate structures. In general, the alterations were more pronounced in the ex situ study than in situ bioassays, which is probably linked to differences in contaminant bioavailability between laboratory and field scenarios. This variation is likely related to, for instance, estuarine hydrodynamics and sediment steady-state parameters. Interestingly, the results suggest that time of exposure is a key factor, since fewer alterations were observed in animals sampled at the end of the assay (28 days) compared to the mid-term (14 days), revealing adaptation to toxicological challenge. In conclusion, mixed sediment contamination can cause physiological alterations in fish gill epithelia that can be determined histologically. These subtle changes may affect the health status of animals by impairing key vital functions such as osmotic balance. As such, physiological alterations to fish gill epithelia may reflect, as in the present case, estuarine sediment contamination even when severe gill lesions are reduced or absent, which mandates caution when interpreting histopathological data in fish for the purpose of environmental risk assessment.
Acknowledgements
P.M. Costa was supported by the Portuguese Science and Technology Foundation (FCT) through the grant SFRH/BPD/72564/2010.
Keywords:
Sediment contamination,
mucous cells,
Histology,
flatfish,
osmotic balance
Conference:
IMMR | International Meeting on Marine Research 2014, Peniche, Portugal, 10 Jul - 11 Jul, 2014.
Presentation Type:
Oral Presentation
Topic:
BIODIVERSITY, CONSERVATION AND COASTAL MANAGEMENT
Citation:
Martins
C,
Costa
MH and
Costa
PM
(2014). Exposure to contaminated sediments induces alterations in the gill epithelia in juvenile Solea senegalensis: a comparative in situ and ex situ study.
Front. Mar. Sci.
Conference Abstract:
IMMR | International Meeting on Marine Research 2014.
doi: 10.3389/conf.fmars.2014.02.00039
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Received:
16 May 2014;
Published Online:
18 Jul 2014.
*
Correspondence:
Miss. Carla Martins, IMAR - Instituto do Mar, Departamento de Ciências e Engenharia do Ambiente, Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa, Caparica, Portugal, c.martins@campus.fct.unl.pt