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The opinions expressed by the experts in the Question & Answer section are those of the experts. They do not reflect EPA policy, endorsement, or action, and EPA does not verify the accuracy or science of the contents of the responses and/or videos.


Q: I grew up on the shores of Lake Superior during the 1960s and early 1970s spending most of my summers on the lake boating the north shore with my family. Returning many years later I have noticed a distinct color change in the lake. Please explain?

A: This is a curious observation. I am not sure what color you recently perceived, but there are two plausible answers to your question. First, since the 1960s the sewage discharge controls have become much better, greatly reducing nutrient additions to our coastal environment. By reducing this fertilizing effect, the lake has become cleaner and clearer, which may account for the color change. Also, if you visit the "north shore" of Lake Superior on a windy day, especially Duluth or Two Harbors, you'll notice the lake has a dark, almost dirty color. The wind suspends clay at the bottom of the lake, which gives it this characteristic color that may linger for days after the wind subsides.


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Q: @EPAresearch #LakeSci11 So what's the latest on invasive species threats (e.g. Asian carp) to the Great Lakes, and what's new in the efforts to combat them?

A: The good news is that no new species have been identified in the Great Lakes in the past few years. The most recent invaders include Hemimysis, a shrimp-like organism, and VHS. New ballast water rules are being implemented to help prevent the transport of exotic species into the Great Lake from other international locations. For the most recent information on Asian carp, all the ongoing activities are posted at www.asiancarp.gov. One interesting idea for combating the spread of asian carp is to use pheromones to interrupt their natural reproduction.


Q: What are some of the biggest seiches that have been recorded on Lake Superior?  Do you have any references for documentation and or pictures showing the effects of seiches?  I hope you are having a great week on the lake.  It is perfect weather to be away from land.  Thank You!

A: Seiches are changes in the lake water level due to the effect of wind. A prolonged, steady wind from a constant direction will drive lake water towards one end of the lake. When the wind relaxes, the water will slide back towards the other side of the lake. To picture this, imagine a teeter-totter going up and down, with the board representing the surface of the lake. The dominant seiche period in Lake Superior is 8 hours. Shoreline areas experience a typical change in lake level of about 5-8 inches during this seiche.
 
Rapid seiches associated with storms can be quite dramatic. Although I do not know if this is the largest seiche recorded, Minnesota Sea Grant Exit EPA Disclaimer reports that a seiche in 1995 caused a drop in lake level of 3 feet in the Lake Superior port of Two Harbors.


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Q: @EPAresearch In 5 years time, will the fishing industry be in a better spot than it is today? #LakeSci11

A: Traditionally, the aim of fisheries scientists is to create a sustainable fishery - one that harvests only enough fish so that there will be sufficient fish to maintain the population in the future. Today, fishery scientists also try to manage these fisheries as part of an interconnected ecosytem because harvesting one fish species may have important implications for other species. This is called ecosystem management. The important point is that fish populations, as well as the entire fishing industry, are reliant on the health of the ecosytem. A major, recent threat to our Great Lakes fisheries is the collapse of the food web in Lakes Huron and Michigan due to the invasive species quagga mussel and zebra mussel. This collapse has severely impacted important fisheries, such as whitefish and salmon. Whether the industry will be in a better spot in five years time is dependent on our ability to find a solution to the mussel problem and restore the food web. This is an important scientific challenge that is key to our fishing industry.


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Q: @EPAresearch #LakeSci11 So what's the latest on invasive species threats (e.g. Asian carp) to the Great Lakes, and what's new in the efforts to combat them?

A: The good news is that no new species have been identified in the Great Lakes in the past few years. The most recent invaders include Hemimysis, a shrimp-like organism, and VHS. New ballast water rules are being implemented to help prevent the transport of exotic species into the Great Lake from other international locations. For the most recent information on Asian carp, all the ongoing activities are posted at www.asiancarp.gov. One interesting idea for combating the spread of asian carp is to use pheromones to interrupt their natural reproduction.


Q: I'd appreciate your comments on the real effects of the ice boom used in Lake Erie. My research concludes it's very bad for the environment and yet people sit by. What's your take? Thanks

A: I am not an expert on the ice boom. To provide some context, the ice boom on Lake Erie is under management of the International Joint Commission (www.ijc.org), a bi-national body established to oversee many important Great Lakes management issues. The purpose of the ice boom is to reduce ice runs into the Niagara River that historically caused flooding and ice-related damage. The ice dam has been installed every year since 1964 at the eastern end of Lake Erie. According to the IJC, "The boom is made up of a series of floating steel pontoons each 9.1 metres (30 feet) long and 76 centimetres (30 inches) in diameter. There are 22 spans, each consisting of up to 11 pontoons, anchored to the bottom of the lake at 122 metre (400 foot) intervals by 76 centimetre (2 ½ inch) steel cables. When in position about 3 kilometres (2 miles) upstream from the Peace Bridge, the ice boom spans the outlet of Lake Erie." (see more info (PDF) Exit EPA Disclaimer (5 pp, 1 MB) ). My personal take is that the best way to understand the effects of management actions is to encourage the International Joint Commission to support research that could identify relevant environmental impacts, if present.


Q: Hola! quisiera saber, el proceso de eutroficación en un lago profundo (aproximadamente 240) y que problemas trae consigo las cianobacterias dentro de los lagos.

Hi! I wanted to know, the eutrophication process in a deep lake (approximately 240) and what problems cyanobacteria bring to lakes?

A:Cultural eutrophication occurs when additional nutrients are added to water bodies, both freshwater and marine, from human sources such as run-off from fertilizer applications and discharge from waste water treatment plants. The nutrients have a fertilizing effect. In response, algae (microscopic plants that float in the water) grow rapidly. Effects from eutrophication range from mild to severe. Mild effects include cloudier water that has the color of pea soup and associated changes to the invertebrates that consume algae. Severe effects include loss of sensitive invertebrates and fish, as well as areas of low oxygen, often called "dead zones" because oxygen can fell below a level to sustain life. That level is about 2 milligrams per liter dissolved oxygen. Commonly identified dead zones include those in Lake Erie, the Gulf of Mexico, and Chesapeake Bay. These are formed when the algae bloom dies off and the plant material sinks to the bottom of the lake or ocean. As bacteria break the decaying matter down, oxygen is rapidly used-up in the water, leading to the low oxygen area. These same process applies to all lakes, including Great Lakes. Some Great Lakes are very deep and do not experience enough wind energy required to mix the water from top to bottom. These lakes, such as Lake Tanganyika in east Africa, always have a deep water portion that is deprived of oxygen because they never mix with oxygen-rich surface waters. Cyanobacteria are a group of bacteria that can photosynthesize. They often form large blooms that can be a nuisance and have associated toxicity.

El proceso de eutrificación cultural ocurre cuando los nutrientes adicionales están añadas a los cuerpos de agua, ambos agua fresca y marinera, de las fuentes humanas como escorrentía de la aplicación de fertilizante y descarga de las plantas que trata a aguas residuales. Los nutrientes tienen un efecto fertilizante. En respuesta, las algas (las plantas pequeñitas que flotan en el agua) crece muy rápidamente. Los efectos de eutrificación van desde leve a grave. Los efectos leves incluyen agua menos claro que tiene el color de la sopa verde y otros cambios a los invertebrados que toman las algas. Los efectos graves incluyen la pierda de los invertebrados y peces más sensibles, así como los áreas de oxígeno de nivel baja, muchas veces llamados "zonas muertes" porque el oxígeno como por debajo de un nivel para sostener la vida. Este nivel es más o menos dos miligramos por litre de oxígeno disuelto. Las zonas muertes que están más comunes son ellas del lago Erie, el golfo de México, y la bahía Chesapeake. Estas zonas están formadas cuando la floración de algas muere y la material de planta hunde hasta el fondo del lago o océano. Como la bacteria descompone la materia en descomposición, el oxígeno está usado muy rápidamente en el agua, que conduce al área baja de oxígeno. Estos mismos procesos aplican a todos lagos, incluyendo los Lagos Grandes. Algunos Lagos Grandes están muy profundos y no reciben el nivel de energía del viento que es necesario para mezclar el agua de arriba a abajo. Estos lagos, como lago Tanganyika en el este de África, siempre tienen un área de agua profundo que está privado del oxígeno porque nunca mezcla con la agua de superficie que contiene mucho oxígeno. Cianobacterias son grupos de bacteria que pueden preformar fotosíntesis. Muchas veces, los forman las floraciones grandes que son una molestia y tienen toxicidad asociado.


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Q: What is being done to make previously polluted #greatlakes like Lake Oregon cleaner? #LakeSci11

A: In the United States, there are two major federal initiatives to clean-up the Great Lakes. The Great Lakes Restoration Initiative is a new program that is the largest investment in the Great Lakes Basin in two decades. Eleven federal agencies were involved in developing the plan which is designed to clean up toxic sites, combat invasive species, promote nearshore health by reducing run-off, restore habitat, and increase outreach. You can learn more about the program at http://www.epa.gov/greatlakes/glri/ The other initiative is the Great Lakes Legacy Act, a program designed to clean-up toxic materials in the Great Lakes Basin. You can learn more about this program at http://www.epa.gov/glla/index.html.


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Q: My follow-up question would be how do they craft the phermones to target just the Asian carp, so it doesn't impact other species? Or are the phermones so specific to Asian carp there are no worries of nontarget impacts? @EPAresearch #newquestion 

A: Yes, the idea is to use a pheromone that is species-specific so it can be used to attract the carp. Similar work is ongoing with common carp.

 

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