Saving the Shortnose Sturgeon, a Look at Eutrophication

I found the following article on the shortnose sturgeon (Acipenser brevirostrum) this morning on ScienceDaily, and due to the conservation problems we're having with the endangered fish, I thought it would be a good opportunity to discuss eutrophication and hypoxia, two huge issues in marine and aquatic sciences.

Dwindling numbers of shortnose sturgeon in Georgia's blackwater Ogeechee River system have prompted an effort to quantify the causes and prioritize recovery efforts.

Yetta Jager and colleagues at Oak Ridge National Laboratory are conducting a population viability analysis, which will provide a scientific basis for assessing cumulative and separate effects of factors thought to be impacting the shortnose sturgeon population.

These factors include siltation of spawning areas, degradation of water quality in summer due to upstream agriculture, urban development and military land management, atmospheric mercury and introduction of saline water introduction through rice canals.

While 19 distinct populations of shortnose sturgeon have been identified in coastal rivers, only two southern populations are thought to be viable. The Ogeechee population has fewer than 500 fish.

All along the east coast of the US researchers are trying to devise methods to save the sturgeon, which, as a species, has roots going back 70 million years, living alongside the dinosaurs. Closer to my home, in Maryland, ecologists are combating water quality issues in the Chesapeake system.

One of the major factors affecting the shortnose (and damn near everything else) in the Chesapeake is eutrophication. The term eutrophication has become a buzz word of sorts in this area, usually associated with an artificial source of pollution, which is not entirely true.

Whenever you see the root "trophic", the word usually refers to productivity or feeding in an ecosystem (from the Greek trophe, meaning food). The term eutrophic is used to describe a body of water (usually a lake) that contains an excessive amount of nutrients in its waters, usually from a long build up of sediments and aquatic plants growing, dying and decaying.

A naturally eutrophic lake is in the last stages of its life as a standing body of water; the build up is causing it to lose depth, while the excess of nutrients causes an algal bloom, a tremendous increase of productivity among algae and other small aquatic plants, which sucks up dissolved oxygen (DO) and reduces sunlight. The lack of DO and light energy kills off dependent organisms, especially in the benthic, or bottom layer of the lake. Areas depleted of DO are hypoxic, more commonly known as "dead zones."

Cultural eutrophication is the culprit regarding the Chesapeake Bay system. The Chesapeake's drainage system - nine rivers and some 140 streams - extends into six states, from New York to Virginia. All the runoff, nutrients from roads, waste systems and agriculture, flows into the streams and rivers, eventually winding up in the Bay. Only one percent of the waste influx is circulated into the Atlantic, which has turned the Bay system into a eutrophic mess, complete with algal blooms and hypoxic zones. These zones cripple the shortnose population, one of the most oxyphilic organisms in those waters.

There was once hundreds of thousands of these fish in the Chesapeake's waters, an integral part of its ecosystem. Now, like the Atlantic oyster and the blue crab, sturgeon populations are mere vestiges, contrasting the huge human population boom in recent years (from 3.7 million to near 18 million in 60 years).