November 28, 2017

Those leaves don't fall far from the tree...or maybe, they do?

The ongoing obsession we have with leaves in water is hardly a surprise these days. Seems like we're constantly talking about the physical and chemical interactions with leaves, and the aquatic organisms which reside in them. In fact, It probably sounds repetitive after a while, geeking out over decomposing leaves, branches, and other stuff in my tanks. Getting excited about darkening water, decomposition, etc.

But hey, we LOVE this stuff!

I know that there are more and more of us. And it's as compelling an environment as exists in nature, filled with biological complexity, animal diversity, and, of course- fascinating aesthetics (for aquarium geeks!).

We talk a lot about those flooded Igapo forests in South America. We share the awesome pics, and we talk about ways to replicate the look- and more recently- the function of these fascinating systems. And, although they are compelling and alluring to us aesthetically, they are vital to nature for the processes which they foster. Like so many things, there is more to it than just a pretty face!

It is known by science that the leaf litter and the community of aquatic animals that it hosts is, according to one study "... of great importance in assimilating energy from forest primary production into the blackwater aquatic system." It also functions as a means to preserve the nutrients that would be lost to the forests which would inevitably occur if all the material which fell into the streams was simply washed downstream. The fishes, crustaceans, and insects that live in the leaf litter and feed on the fungi, detritus, and decomposing leaves themselves are very important to the overall habitat.

In the aquarium, leaf litter and botanicals certainly perform a similar role in helping to sequester these materials. However, in the closed confines of the aquarium, what are the impacts of deep leaf litter beds? We've already started to see some hobbyists exploring this, and they're finding out lots of interesting stuff.

Is there a "practical limit" to how deep you can go with botanicals in an aquarium? Do various botanical materials have different impact and function within the bed? You know, possibly creating void spaces for dentrification, sequestering of detritus or dissolved organic materials...or even forming microhabitats for fishes?

As we've talked about before briefly, another interesting thing about leaf litter beds is that they actually have "structure" and even longevity. In several studies I read on the subject, the accumulations of leaves in various streams are documented to have existed in the same locations for years- to the point where scientists actually have studied the same ones for extended periods of time.

Some litter beds form in what stream ecologists call "meanders", which are stream structures that form when moving water in a stream erodes the outer banks and widens its "valley", and the inner part of the river has less energy and deposits silt- or in our instance, leaves.

There is a whole, fascinating science to river and stream structure, and with so many implications for understanding how these structures and mechanisms affect fish population, occurrence, behavior, and ecology, it's well worth studying for aquarium interpretation! Did you get that part where I mentioned that the lower-energy parts of the water courses tend to accumulate leaves and sediments and stuff? It's logical, right? And it's also interesting, because, as we know, fishes and their food items tend to aggregate in these areas, and embracing the "theme" of a litter/botanical bed or even wood placement, in the context of a stream structure in the aquarium is kind of cool!

Huh?

Well, rather than covering the whole bottom of your tank with leaves, would it be cool to create some sort of hardscape structure- with driftwood, etc., to retain or keep these items in one place..to create a "framework" for a long-term, organized, specifically-placed litter bed. You could build upon, structure, and replace leaves and botanicals in this "framework"- like, indefinitely...sort of like what happens in the "meanders!"

How would fishes react when presented with a deep litter bed in part of the aquarium; would they prefer to reside there? Or would they simply forage there and stay in the more open areas of the aquarium? Would the spawn there? Probably some fry would seek shelter there, right? If you did what Mike Bognich does, and cultivated "on board" food sources in the litter /botanical bed, it's a sure bet that many fishes would at least spend part of their day there, foraging away as they do in the wild. What other interesting behaviors could we observe in such an area?

As always, these ideas seem to spur on more questions than they answer! However, the questions that we're addressing at this point in our botanical journey are truly fascinating ones, with the answers promising potential breakthroughs and improvements in technique and understanding of these dynamic aquatic systems!