Fish: Sediment Buildup From Human Activities Impairs Breathing

New research shows that suspended sediment accumulated via human activities can impair the breathing of fish, as well as increases the rate of disease in fish.

"Suspended sediments result from flood plumes, coastal agricultural and industrial development and from dredging operations and are increasing in coastal waters worldwide," study co-author Dr. Amelia Wenger said in a news release.

"Fish gills are in direct contact with their environment and are the first line of defense in the animal's immune response, which makes them the perfect place to look for damage associated with sediment," noted co-author Dr. Jodie Rummer. "Plus, harm to this vital organ affects every activity in the animal's body that requires oxygen."

To better assess the impact of sediment build-up on marine life, researchers from the ARC Centre of Excellence for Coral Reef Studies at James Cook University simulated sediment conditions frequently found on inshore reefs on the Great Barrier Reef. However, that's not to say the problem is limited to Australian waters. Suspended sediment is a global phenomenon, and tends to overlap critical fish habitats and nurseries.

Juvenile reef fish, for instance, are often exposed to sediment as they swim in open waters before settling on a chosen reef. This early stage in life is critical for development, during which time juvenile fish need lots of oxygen - but damage to their gills can hinder their ability to acquire it.

"The gills in sediment-exposed larval clownfish fish were congested, exhibiting twice as much mucous of what could be found in clean-water exposed fish," said study lead author, Sybille Hess. "Sediment-exposed fish also increased the number of protective cells on their gills, presumably safeguarding the delicate tissue from the damage that sediment particles could cause."

"Larval fish have very high growth rates," explained Rummer. "They're swimming a lot, often over long distances. They have a very high metabolic rate and high-energy costs and need their gills to be working as efficiently as possible."

The gills of affected fish were also found to harbor disease-causing bacteria.

"The presence of bacteria linked to fish disease on the gills of sediment-exposed fish suggests that exposure to, and accumulation of sediment, may trigger the development of fish diseases," said co-author Dr. Tracy Ainsworth.

These results, published in the journal Scientific Reports, highlight the need to monitor future coastal developments, which is having an adverse effect on fish.

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