Creeping Dead Zones

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The Great Global Fertilization Experiment

It’s summer 2003. After a long winter, the citizens of Lamèque, New Brunswick on the Acadian Peninsula are looking forward to enjoying the best of what New Brunswick summers offer – warm days, blue water, outdoor living. What they got instead was the gut-wrenching stench of rotten egg gas – hydrogen sulfide – emanating from the shoreline and sediments of beautiful Lamèque Bay. The levels of H2S were so high, the provincial government issued a public health advisory, warning people to stay inside.

For several years, area residents had been living with and complaining about pollution from the local fish plant. Year after year, heavy discharges of fish waste and process water had loaded the semi-enclosed, shallow bay with nutrients or “fertilizers” (in the form of nitrogen compounds) and solids which settled on the bottom. Together they created the conditions that resulted in a very sick bay.

Lamèque is not alone. Every summer, the bright green and brown mats of algae on beaches and shorelines that smother rockweed and eelgrass, have become more widespread. All along the New Brunswick coast — Tracadie, Cocagne, Bouctouche, Shediac, L’Etete, L’Etang — sheltered bays and estuaries are suffering from nutrient pollution.

Nutrients – When too much of a good thing turns into a problem

Nitrogen and phosphorus are nature’s fertilizers. These nutrients spur the growth of plants and are staples in commercial agriculture and home gardens. But too much of a good thing can bring death, not life.

Over-loading of phosphorus in fresh water and nitrogen in salt water triggers a process called eutrophication. These nutrients fuel massive blooms of fast-growing, short-lived aquatic plants. They can be phytoplankton blooms which are microscopic, or they can be larger algae species. Along marine coasts, these include the bright green mats of enteromorpha and ulva (sea lettuce), and brown algae and epiphytes that coat rockweeds and eelgrass.

As these algae die, they sink to the bottom where bacteria decompose the dead plant material. The process of decomposition uses up oxygen. As oxygen levels drop (hypoxia), carbon dioxide levels increase. The low-oxygen conditions in the sediments provide an ideal environment for certain types of bacteria that produce ammonia, hydrogen sulfide or methane gases in the sediments. These gasses are released into the water and eventually to the air. They are hazardous to humans and toxic to marine life. Low-oxygen conditions can be seasonal or they can become prolonged as nutrient loading persists.

This effect is worsened where solid wastes have accumulated on the bottom, such as from sewage and fish plants, pulp mills or finfish aquaculture sites. These wastes are also decomposed by bacteria, and oxygen is also used up in the process. The release of these types of solid waste is called organic enrichment, organic referring to material that was once living.

Loading high levels of nutrients and organic matter starts a complex chain reaction that can eventually transforms a healthy aquatic ecosystem teeming with a diversity of plants and animals into sterile dead zones suitable only for worms and bacteria that can tolerate low oxygen conditions.

Toxic Tides: Harmful Algal Blooms Threaten Fish and People

The very base of the marine food chain is made up of thousands of species of microscopic algae. Collectively, they are referred to as phytoplankton.  A few dozen species are classified as “harmful” because of the toxins they produce. When physical, chemical and biological conditions are right, population explosions of these species occur. Scientists call them “harmful algal blooms” or HABs. We generally call them “red tides” or “brown tides” because of their colour in the water.

HABs have been known to exist for thousands of years – aboriginal people knew well to avoid shellfish during warmer months. The old adage that you only harvest clams in months with an “r” was a way to protect against poisoning long before governments started monitoring for HABs. Yet HABs worldwide have been increasing in number and frequency over the past several decades. These increased outbreaks coincide with the increase in nutrient loading to coastal waters. While the precise interactions between nutrients and HABs are still being investigated, a major report published by the Ecological Society of America notes that at least in some incidences of HABs the evidence connecting the two is very strong (Issues in Ecology, No. 7, Fall 2000).

In August 1999, several thousand salmon in aquaculture sites in Passamaquoddy Bay were killed by a bloom of Mesodimium rubrum. This species affects the central nervous system of the fish. The next year, Alexandrium killed farmed salmon in southwest Nova Scotia. In 2003, both Alexandrium and Mesodimium bloomed off Grand Manan and in Passamaquoddy Bay, killing between 50,000 and 60,000 salmon.


Dead Zones – A Global Problem

Normally, the International Botanical Congress, which every six years draws several thousand scientists from 100 countries to discuss the latest research on plants and their relationship to humans, doesn’t warrant much attention from the mainstream media or the general public. Not so for the XVI Congress held in Missouri in 1999.

That year, Dr. Jane Lubchenco of Oregon State University and her colleagues Harold Mooney and Peter Vitousek of Stanford University created an international stir with their presentation on the “human footprint on Earth.” They concluded that humans have gravely altered the chemistry, biology and physical structure of the Earth’s land and water. Nearly half of the Earth’s land surface has been transformed by actions such as filling in wetlands, converting tall grass prairie into cornfields, and converting forests into urban areas, part of a “disturbing negative trend in the Earth’s ability to maintain the quality of human life,” said Lubchenco.

What got the headlines, however, was their declaration that there has also been a dramatic alteration of the Earth’s oceans. Lubchenco reported there were then 50 ‘dead zones’ in the world’s coastal waters, areas with little or no oxygen. The largest in the Western Hemisphere is in the Gulf of Mexico (in 2004 spanning 21,000 sq km), generated by the nutrient-laden discharge of the huge Mississippi River. Triggering this ‘dead zone’ phenomenon is the burning of fossil fuels which releases nitrogen compounds, and excess fertilizer use in agriculture. These have more than doubled the amount of nitrogen that is naturally available in the environment, according to Lubchenco.

“We’ve long thought of oceans as having an infinite ability to provide food and other goods and services to humans. But massive human-wrought changes in our oceans are impairing their ability to function as we assume they will,” warned the Distinguished Professor of Zoology. “We’re degrading the water, changing our coastlines, filling in our estuaries, and changing our rivers. And we’re witnessing many signals of the problems that will result from these changes, including toxic algal blooms, coral bleaching and sudden disappearance of fish from key fisheries.”

Since that 1999 warning, things have only gotten worse. In 2001, a report on the state of the world’s oceans by the United Nations Environment Program (UNEP) identified 50 dead zones caused by excessive nutrient loading. In 2004, the number of dead zones rose to 150 . In 2006, UNEP reported that the number had risen to 200. In most cases, these dead zones are nursery grounds for marine species, which inhibits the ability of these populations to replenish themselves. Experts call it a major threat to fish stocks and to communities that depend on them.

Nutrient Pollution in New Brunswick – how bad is it?

In 2005, a workshop was convened in Prince Edward Island to examine the ecological impact of nutrient loading to freshwater and marine ecosystems. Participants heard that episodes of oxygen starvation and subsequent fish kills due to nutrient loading from agricultural run-off are reported annually at 18 to 20 freshwater and estuary sites around PEI and that these events were becoming more frequent and spread out over the calendar year. The Island’s long estuarial residence times and relatively low tidal range exacerbate the problem.

How bad is the nutrient pollution problem in New Brunswick? Unlike in the US, no systematic surveys have been done in Atlantic Canada to quantify the degree and scope of the problem here.

For the Conservation Council, there is enough observational evidence to suggest our inland bays and estuaries are suffering from nutrient overloading as well. This was especially true along the Northumberland Strait and around the Acadian Peninsula where, like PEI, the bays and estuaries are shallow and, in general, protected by barrier islands or sand bars, which reduce tidal flushing.

In 2001, the Conservation Council conducted an ecological survey of natural oyster beds on the north and east coasts of New Brunswick (Milewski and Chapman 2002). This study reported that hundreds of natural oyster beds and reefs had been buried under many metres of sediment and many existing beds were being threatened with the same fate. In addition, most bays were exhibiting symptoms of nutrient pollution such as nuisance (green) algal blooms on beaches, oysters covered in blue-green algae and eelgrass blades smother with epiphytic diatoms.

As a follow-up to the oyster survey and as part of CCNB’s ongoing commitment to addressing nutrient pollution issues in New Brunswick’s marine waters, researchers working with the Conservation Council conducted a eutrophication assessment of eelgrass beds in selected estuaries in northern and eastern New Brunswick (Lotze et al. 2003). In 2004, the Conservation Council developed a simple export model to estimate the amount of nitrogen being released to estuaries from point and non-point sources.

Along with the atmospheric fall-out of nitrogen compounds from fossil fuel power plants and gaseous ammonia from manure lagoons, fish plants, run-off from peat mining and forestry operations, pulp mills, agriculture, sewage treatment plants and septic systems all contribute nutrients to these water bodies. While the sources vary from one estuary or bay to the next, the result is the same – slimy green algae rotting on the shore, epiphytes smothering eel grass and oysters, floating mats of algae sinking to bottom and destroying habitat, and the telltale smell of rotten egg gas.

The Conservation Council appeared as a witness before the Senate Standing Committee on Energy, Environment and Natural Resources reviewing the Canadian Environmental Protection Act (CEPA) in November 2006. Several months earlier we had submitted a brief outlining the mechanism by which CEPA could regulate nutrients.

Canada is signatory to the UN agreement called the Global Programme of Action for the Protection of the Marine Environment from Land-based Activities (the GPA). The GPA lists nutrients as a contaminant of concern. Canada’s National Program of Action (NPA) developed to implement the GPA classified nutrients as a low priority nationally and in the Pacific, Arctic and St. Lawrence regions. In the Atlantic Region, nutrients are rated a medium priority. Based on our research, we believe this classification underestimates the problem of coastal eutrophication. Leading marine scientists say nutrients are the greatest contamination threat to coastal waters worldwide.