Trophic Lake Terms??

[LegitFish]

I'm trying to figure out what Georgian Bay would be considered...?

 

Oligotrophic?

Mesotrophic?

Eutrophic?

 

Tried google but found sites that gave me all different answers

 

Thanks!

[12 Volt Man]

georgian bay would probably be considered mesotrophic.

 

basically, oligotrophic lakes are new lakes (formed usually from the gouging out of the canadian sheild by the glaciers)

 

 

they will be cold, clear, often deep not much weed growth (eg. Lake Muskoka)

 

Mesotrophic lakes are 'middle age lakes' that have a good amount of weed growth, and are quite productive in terms of plants/fish etc.

 

eutrophic lakes are the oldest lakes, where they are extremely thick with vegetation algae etc. and are often shallow from millions of years of sediment deposits.

 

I don't think we have any true eutrophic lakes around Ontario.

 

keep in mind that nutrient run off can cause a lake to become eutrophic, as it results in excess algea/plant growth.

 

but this is different than the natural progression of lakes over thousands of years.. its whats known as 'cultural eutrophication"

Edited June 26, 2010 by 12 Volt Man

[a.cortellessa]

I never knew that age had to do with the classification of the lake. I thought it just depending on depth, clarity and weed growth.

Ya learn something every day!

[12 Volt Man]

see, age can be part of the picture as lakes will naturally progress through the stages (called succession) without any human influence.

 

a new lake starts out deep and cold

 

over thousands of years, sediment from rivers and streams fills it up

 

makes it shallower, which allows for plants to grow on the bottom and still get sunlight

 

over time, plants increase oxygen levels, plankton begin to flourish, fish feed on plankton etc.

 

the lake becomes very productive in terms of plants and animals even though it started off with nothing.

 

 

 

however, given that this is the 2000's, few lakes are free from human impacts. agricultural runoff adds nitrogen and phosphorus into lakes which causes them to become eutrophic very quickly (compared to the amount of time it would take with no human influence).

 

I took a course in freshwater biology at university (a long time ago now though lol) so I remember a lot of this stuff.

 

biologists classify lakes as being eutrophic or not based on their nitrogen to phosphorus ratio. so they really don't care about the age of the lake.

[LegitFish]

Wow. Thanks man. I just learned alot!

[timmeh]

Depending on what part of Georgian Bay you are in. The open waters would most likely be oligotrophic, while some of the bays and coastal area would be meso mostly due to human influence.

[houski]

Lots of eutrophic lakes in Ontario. As in all of the Kawartha Lakes.

[Burtess]

Hey 12 Volt.... are you the same 12 Volt Man that's on MFK??

 

Burt

[12 Volt Man]

yup. thats me