Hello Party People.
Surface water, whether it's a Lake Wobegon (shout-out to my homies in MN) or a backyard koi pond, will confound you at times with its many mood swings from season to season. There are many parameters (environmental, chemical, physical, biological, celestial....), that contribute to the conditions that you observe at any given time down at the pond. I have put together this article to shed some light on the basics of the elements that drive change in your pond. There are bunch more factors that contribute to the conditions we see, but here I am focusing on nitrogen.
Nitrogen is everywhere...... The air we breathe is 80% nitrogen, and Mother Nature has harnessed this nitrogen into the essential building blocks of life as we know it. Nitrogen-containing molecules (like Ammonia, Nitrate, Nitrite and their derivatives) makes up crucial parts of amino acids and proteins that build critters like human beings. These molecules are also needed to make plant material. Without nitrogen-containing molecules, we would not have the photosynthetic organisms that produce the oxygen that's needed to bloviate about your fantasy football team (perish the thought).
(BTW..... the author of this article is a three-time Champ of the Shut The Front Door Fantasy Football league.....Please inquire in the comment for the details.......)
On land, the cycling and recycling of nitrogen plays out mostly in the soil. Nitrogen from the atmosphere is "fixed" into usable molecules by lightning strikes and bacteria. These molecules then turn into plants, which animals eat, and return to the soil as waste or decomposing plant/animal parts.
Ok, as fascinating as all that is, this is a water article...... Who cares about land stuff anyway?
BEHOLD! THE NITROGEN CYCLE!!!!!!!!!!!!!
Fresh water acts somewhat differently than terrestrial environments when dealing with nitrogen (N). On land, nitrogen is widely available...in aquatic environments, nitrogen is limiting. That is, in a healthy aquatic environment, there is not enough of it to go around. Any available nitrogen-containing molecules are sucked up in rapid fashion to be utilized for primary production (plants and algae). It is noteworthy here to mention that it does not take a large waterbody to complete the nitrogen cycle; it can easily occur in your back yard koi pond.
What does this mean for you?
If your nitrogen levels are artificially high, you are in for lots of algae growth, and potential fish health issues too.
Please notice in the above picture (thank you, internet) that all internal cycling of nitrogen within the pond biome requires the decomposition of organic material (plant/animal/algae). This is the area where we as resource managers can effect the amount of nitrogen in our ponds.
In watergardens, you can physically remove nitrogen by doing a water-change or a good spring cleanout. In larger systems, physical removal is harder and very expensive, as dredging or re-excavation are our only options.
As in most of the articles that I've posted here, I'm going to lean heavily on aeration. No matter the size of your system, aeration is the single best tool for managing water. For small backyard watergardens that means: run the waterfall/fountain/filter as much as you can. For larger systems, it means diffused aeration and/or large aerating fountains.
Properly aerating the water achieves many things. For our purposes here, I will stay focused on how it helps you out with excess nitrogen.
Nitrogen is bound up in organic material that sits on the bottom of the pond and gets kicked up into solution in the form of nitrate, nitrite, and ammonia. Maximizing the efficiency of our pond ecosystem will mitigate these molecules, making them less available to fuel excess weed and algae growth. The lifting action of rising air bubbles brings the volatilized nitrogen containing molecule ammonia to the surface where it can blow away on the wind. Bringing air to the bottom (and throughout the water column) allows for the bottom of your food chain to become more active and plentiful. The bacteria and insects (and other creatures) that feed on nitrogen-laden organic material need oxygen to survive. More oxygen = more critters available to tie up nutrients (like nitrate, nitrite and many others). If the bulk of the nitrogen is tied up within the food chain, it is unavailable to algae and/or nuisance plantlife. Higher organisms (fish, frogs, insects) can sequester and concentrate nitrogen-containing molecules more efficiently than algae and plants. They also tend to hang onto those molecules for longer as higher lifeforms live for a relatively long time. In a lot of cases, these organisms leave the pond altogether, taking their stored nitrogen with them. Every time a fish is eaten by a heron, or a dragonfly grows its wings and flies away, they take all their contiguous nutrients with them.
So lets prop up the ecosystem, shall we?
- If you are not on a bacteria regime, start one. Bolstering the bacteria that are living in your pond (especially watergardens) can bring about positive change to the pond biome.
There are a lot of choices for bacteria out there, so please ask questions if you get confused/overwhelmed by all of the products offered. We have plenty to choose from on Midwestponds.com, so search away.......
- Maintain a balanced fishery..... fish are a great way to tie up nutrients, but each system can only support so much fish biomass. Encourage your best specimens, while removing the smaller, less important fish so the system can stay balanced.
- Harvest off dead or dying plant matter so that the nitrogen in those plant parts cannot be re-cycled back into the system.
Mother Nature is undefeated. She will have her way no matter what we do, so work with her in helping keep your pond environment stable and healthy. As always, please ask for clarifications or further questions in the comments. I am here to help!
Thanks for taking the time.....