Introduction to Eutrophication

Algal blooms are one of the most common processes in the marine environment – they occur whenever nutrient levels in the water get too high and small photosynthetic algae multiply uncontrollably until the nutrient supply is exhausted. This process is called eutrophication, and while it may seem innocuous – algae are small, after all, how could they really affect the marine environment? Well, these seemingly harmless creatures can end up creating “dead zones”, huge areas of barren seascape primarily found at the outflows of freshwater rivers.

The way in which this happens starts with the first blush of the algae bloom. As the tiny protists multiply, they cloud the water until sunlight can barely penetrate, interfering with the photosynthesis of the marine plants below, which kills them and lowers the amount of oxygen available in the water. The problems are only exacerbated after the nutrient supply runs out and the algae begin to die off – as their billions of tiny bodies decompose, they take up yet more oxygen and plunge the area into a state of hypoxia (low dissolved oxygen, 3-5 mg/L) or worse, anoxia (no dissolved oxygen at all). Fish and other motile organisms flee the area, and benthic organisms that are sessile (immobile) cannot move to more oxygen-rich areas and thus suffocate. This creates a massive area devoid of all life that cannot be repopulated unless oxygen levels rebound.

These dead zones are found throughout the world wherever rivers empty into the ocean, most notably in the Gulf of Mexico, the Baltic Sea, and the southeastern Australian coast. They are caused primarily by a sharp increase in the demand for agricultural products. This demand triggers more usage of fertilizers, which ultimately start the cycle of algal growth and death. Algae blooms are a huge marine problem, decimating large swaths of the ocean annually, and they are almost cocmpletely anthropogenic – caused by our own human greed or carelessness.

Causes of Eutrophication

Algal blooms and eutrophication are basically caused by an excess of nutrients being added to the system. Mainly, these extra nutrients are anthropogenic, stemming from human activity. Stormwater runoff carries such things as fertilizers into lakes and rivers, which all eventually lead to the ocean. These fertilizers are filled with phosphates and nitrates, two limiting nutrients that algae feed on. Once these enter the water column, it is only a matter of time before an algae bloom occurs. The fertilizers can be manmade agricultural fertilizers or “natural” fertilizer from livestock – the former is more potent, but both are prevalent in our waterways.

Eutrophication Causes Graphic

Eutrophication Research

Research for Eutrophication

Eutrophication Graphic

Solutions for Eutrophication

Aside from the obvious increase in regulations dealing with fertilizer intensity and use or stormwater runoff control, there are several engineering-minded solutions that can be deployed to halt or prevent algae blooms. The easiest is increased replenishment of salt marshes and mangrove swamps. If stormwater has to travel through these natural filters before it reaches the open ocean, the plants there will likely take up the nutrients before the algae have a chance to explode in population. It is natural and very safe, and relatively easy to gain public support for. If bigger natural filters are an issue, true filters can be used at the outflow of rivers and lakes to trap algae which have started to bloom in freshwater. These filters would be unobtrusive and would deal with many different kinds of pollution as well as eutrophication. The mesh of the sponge of the filter would only be a few microns wide, and would likely have to be cleaned or replaced every couple of weeks - more expensive but still relatively simple.

If the algae bloom is already in progress, a technique called ultrasonic irradiation can be used, which involved hitting the algae bloom with high-pitched sound waves in order to puncture the vacuoles that keep them afloat. After being hit by the waves, the algae sink to the bottom and die in seconds. Though this method still depletes oxygen through the rotting algae, the fact that the marine plants gain immediate access to the sun will mostly counteract this. If used early enough, this method can completely halt the effects of an algae bloom and return the area to full prosperity. If used in conjunction with one of the preventative measures, this technology can ensure a bloom-free coastline for the foreseeable future – a definite positive result.

Introduction to Rainforest Deforestation

As the needs of humans and their demands on industry grow, rainforest deforestation is becoming an increasingly large environmental problem. The devastating effects of human activity on the rainforests can be seen in the dramatic reduction in the amount of earth’s surface they cover. Once rainforests coated as much as 14% of Earth’s surface, but today the number is closer to 6%, and shrinking. Every second, one and a half acres of rainforest are lost forever, complete with nearly 137 plant, animal, and insect species every day. Many of these estimated 5,000 species lost every year were never discovered and now never will be. Some estimates hold that the rainforest will be completely wiped out in as little as 40 years.

The possible impacts of this tragedy are menacingly colossal when one considers that nearly half of all plant and animal species on Earth are endemic to the rainforest. About 25% of medicines used in the modern pharmaceutical market are derived from rainforest ingredients. However, currently less than one percent of the trees in the rainforest have been tested for medicinal properties. Imagine the potential contained within this vast pool of resources that is currently being ruined.