Bald eagles are telling us an interesting story about the Columbia River and its estuary. There are lessons to be learned – lessons that apply directly to our own Coos River and its estuary.

Back in the 1960s there were only 20 nesting pairs of bald eagles in the Columbia River drainage. With the passage of the Endangered Species Act, they quickly became our most famous endangered species.

The main culprits in the near-demise of the eagles were the toxic contaminants DDT, now largely transformed within the environment into its byproduct DDE, and dioxin.

Environmental regulations that were put into effect were largely successful in reducing the input of these toxins into the river system. As a result, the number of nesting pairs has increased to about 800 pairs today, and the bald eagle was removed from the endangered species list back in 2007.

Continued monitoring of the bald eagle situation over the years has established the fact that levels of DDE and dioxin have dropped markedly throughout the river system. But, these monitoring activities have also identified an interesting anomaly.

One specific section of the river has higher toxin levels than the rest of the river. Eagles living along this specific section have markedly lower reproduction rates as a result, which raises unanswered questions as to how young salmon within this area might also be impacted by the higher toxin levels.

The section of river showing these higher toxin levels is the lower estuary, the area between Astoria and Cathlamet.

This has not come about because there was direct input of more of these contaminants in the area. Rather, it is the result of the natural processes whereby silt and contaminants get washed downriver and tend to accumulate in the lower estuary where river currents tend to dissipate and deposit the loads of silt and contaminants they may carry.

Let’s apply the lessons learned on the Columbia to Coos Bay.

It is an established fact that juvenile Chinook salmon, after spending about 6 months in Coos River and estuary, head back into the ocean carrying significant loads of DDT, PCBs, and PAHs within their bodily tissues. Obviously, it is safe to assume these contaminants, as well as others, are widely spread throughout the ecosystem.

Based on the Columbia River experiences, it is also safe to assume that the silts and sediments in the lower Coos estuary, through a process called sequestration, probably contain the highest levels of toxins within the Coos ecosystem.

These persistent organic contaminants are extremely long-lived, and are not readily broken down by natural processes. They can be effectively removed and prevented from cycling through the food chain by becoming trapped and isolated within silts and sediments.

This brings us to the ongoing proposals and discussions relating to various schemes to dredge lower Coos Bay.

Normal annual maintenance dredging to maintain the existing shipping channel is probably not a major concern. Of great concern, however, should be the proposals for major relocation and reconstruction of the shipping channel to service an LNG terminal, or a major container shipping terminal, or to provide access to Panamax-type vessels.

These types of major excavations would be certain to stir up older sediments – sediments that carry significant loads of contaminants dating back to a time when there were no controls on the types or amounts of toxic releases. In effect, these old contaminants that had been removed from the aquatic food cycle by sequestration would be released to cycle yet again and re-enter into the present-day food chain.

Will this pulse of additional contaminants push our already compromised estuarine ecosystem to a threshold whereby significant and irreversible negative impacts occur?

Judging from the lack of any significant discussion or analysis of this potential problem, nobody knows – and nobody cares.