The Dead Zone

by Paul Leline, Secretary

Lurking beneath the waters of Green Bay lies a menacing “monster”!  Undetected by most, it has been feeding upon the unsuspecting bodies of millions of creatures and has been doing so for decades. It resides in a region of the bay known as…The Dead Zone.

Unlike the fictional Stephen King novel of the same name, this DEAD ZONE IS REAL.

Since the early 70s, the Door County Environmental Council (DCEC) has been educating and advocating for a sustainable environment in and around Door County.  Recently, the DCEC has been focusing on the water. Certainly people have been drawn to the Door Peninsula because of its beauty and surrounding waters. However, most tourists and many locals have no idea that there is a toxic and hypoxic region in Green Bay that is growing ever closer to the Door County waters each summer. The Dead Zone.

Dead zones have become more and more numerous over the years and some have become infamous tragedies. There is a large dead zone in the Gulf of Mexico at the end of the Mississippi River, also one in Lake Erie, the Chesapeake Bay, and the Baltic Sea. Most concerning to us in Northeast Wisconsin are the dead zones found in Lake Winnebago and the bay of Green Bay.

Exactly what is a dead zone?

It refers to an area in a body of water where the oxygen levels are so low (hypoxic), most aquatic creatures cannot survive. 

How does a dead zone form?

It all begins with excessive nutrients flowing from the land and washing into the local waters usually during large rain events. These nutrients can be in the form of agricultural fertilizers, animal manure, lawn fertilizers, sewage treatment plant discharge, and storm waters. The main culprits in these nutrients are phosphorus and nitrogen. These two elements are the fuel that feeds the exponential growth of algae in the water forming algal blooms.

These algal blooms can become so thick that they create floating, pea green mats of algae. There can be many varieties of algae comprising the bloom, but one of the more dangerous ones is blue-green algae or more correctly called cyanobacteria. As the living algae cells eventually die, they sink to the bottom of the bay and are decomposed by a variety of bacteria and other organisms that feed upon the dead cells. In order to digest this organic matter, oxygen is needed in large amounts. As the decomposition process continues, more oxygen is removed from the water until it becomes hypoxic with low levels of oxygen or anoxic with zero oxygen present. 

Dead zone waters are found trapped in the very cold lake bottoms. Because northerly lakes have cold and warm areas, unlike the always warm southern lakes, they form stratified layers in the water due to varying temperatures. This temperature stratification is called the thermocline. The uppermost thermocline layer (the epi-limnion) is usually the warmest. The middle layer (the meta-limnion) is cold and often referred to as the thermocline. The lowest bottom layer (the hypo-limnion) is the densest form of water at 39°F or 4°C.

The Dead Zone in the bay of Green Bay Submitted by Paul Leline

As the seasons change, particularly in spring and fall, the rapidly changing temperatures of water create a rise and fall of the water’s layers according to their temperature. Since the top warmer layer is in contact with the atmosphere, it has become richer in oxygen through surface agitation. Then in the fall as the top layer gets colder, it begins to sink towards the bottom carrying with it the oxygen from the top. This “lake turn-over” phenomenon makes northern lakes more oxygenated than warm lakes. But, in the warm and often hot summers, the colder bottom layers are trapped with a finite amount of oxygen. This finite amount of oxygen is what the decomposers of algae must use on the bottom of the lake. When the oxygen is nearly all depleted, most life forms cannot survive, and we have a dead zone. Fish, including walleye, perch, and bass, along with many invertebrates, are particularly vulnerable. As oxygen levels drop, these organisms either migrate away from the area or perish if they cannot escape. In Green Bay, the reduction in biodiversity due to the dead zone, has significant ecological and economic consequences. The bottom dwelling goby fish in the southern portion of Green Bay, have been seen by the thousands climbing up onto rocks and shore, mouth’s gaping open and gasping for air, trying to escape the dead zone in the late hot summer, when algae growth is the greatest and dead zones are at their peak. Due to climate change, the warming waters are exacerbating the algal blooming process and causing the dead zone to grow in size along the bottom of Green Bay.

Aside from the loss of oxygen resulting from the blue-green algae cells decomposing, these cells also rupture and release toxic substances, endotoxins, into the surrounding waters. When exposed to humans or animals by eating, drinking, touching, or breathing, these endotoxins can cause serious health conditions affecting one’s liver, kidneys, nervous system, and/or skin.

Preventing dead zones from forming requires a multifaceted approach, with a focus on reducing nutrient pollution. Prevention includes:

·         Implementing better practices in agriculture, such as controlling fertilizer/ manure applications. 

·         Significantly reducing nutrient runoff.

·         Planting of cover crops and reducing the amount of nutrients applied to the land.

·         Creating larger buffer zones or “prairie strips” near drainage ditches, creeks, streams and rivers that lead into Green Bay. These buffers can act as natural filters, trapping nutrients before they reach the water.

What can we do?

Public awareness and political policy are the most important part of promoting better land use practices. Better regulation of nutrient discharges is essential. Presently, there is very little oversight of the nutrient spreading in Northeast Wisconsin. Also, there has been no control on the size of an industrial farm. Concentrated animal feeding operations (CAFOs) house thousands of dairy cows and are being allowed to expand their herds by the thousands, continually threatening the waters of Wisconsin. The Door Peninsula, with its karst bedrock and shallow soils is probably the worst place to spread the vast volumes of liquified nutrient waste─waste that continues to increase annually by the millions of gallons. And with that scenario, the Green Bay dead zone will continue to increase in size. There are solutions, and a balance can be reached. Wisconsin people need to speak up to our community members and lawmakers, to prevent the waters of Green Bay, along our Door County shoreline, from becoming a Dead Zone.