swamp: /swämp/ noun- An area of low-lying, uncultivated ground where water collects; a bog or marsh.
It's been a while since we've taken a more detailed look at a wild habitat, to get some insights in how it formed, what it's influences are, and how we can use this information to create aquariums which seek to replicate their form and function. So today, let's return to the swamps! Well, not just any old swamps- let's check out the peat swamps of Borneo!
The island of Borneo is widely known as one of the most biodiverse ecosystems on earth, and the peat swamp forests there cover around 12% of the land in Southeast Asia! Peat swamp forests are a form of tropical forest in which very saturated soils (called "histosols" by geologists) inhibit the decomposition of organic materials, such as leaves and other parts of trees and forest vegetation, which leads to the formation over time of peat.
In areas with poor drainage, peat can accumulate over long periods of time until it rises above normal groundwater levels, which creates raised bogs, known to ecologists as "ombrogenous" bogs, which are fed only by rain, and thus have their own water table. The peat retains water via capillary action. These bogs can be as much as 60 feet (20 meters) deep(!), and are largely deficient in nutrients because of the lack of input of mineral input. The leaching of organic compounds from the peat causes the water contained in these bogs to be extremely acidic (like pH4 or lower!).
These "omborgoenous" peat swamps can develop in in areas between rivers in locales with year-round rainfall, as well. They're fascinating structures, home to an enormous diversity of life. Here's where it gets interesting to us fish geeks:
Studies have shown that approximately 219 species of fishes have been found in peat swamps, with approximately 80 of these species restricted to this habitat alone! And 31 are what are known as "point endemic" species, found only in single locations!
That's a LOT of species in a very unique habitat, huh?
Some scientists suggest that the conditions in peat swamps have favored the evolution of smaller, specialized fish species, and that each area of peat swamp could support its own group of endemic species. This is interesting and important...Some species (17 have been identified at the moment) from these habitats are classified as vulnerable, endangered, or critically endangered.
In fact, the environments themselves are endangered...and humankind's encroachment, exploitation, and destruction of these habitats is a very dangerous problem for our planet's existence.
During the wet season, the peat swamps are inundated with water, which slows down the aerobic decomposition which occurs in the substrate- conditions which facilitate the formation of peat. During the dry season, the water levels in the swamps decrease, exposing a significant amount of peat to the air (which leads to decomposition and the release of CO2 into the atmosphere. This is exacerbated by human intervention, such as slash and burn agriculture, etc.
We all know what that means.
Sadly, these vast swamplands are not well understood, and often are under appreciated in the nations in which they are found, treated like "wastelands", which need to be converted to other human-important uses. This has resulted in their rapid disappearance and an increasing in fires, logging, and conversion to agricultural and industrial uses.
Scientists on the front line of studying ecological dangers are concerned about this, because of the huge quantity of carbon that these swamplands store and potential release into the atmosphere. It's thought that as much as 3% of the total global emissions of CO2 can come from these habitats if they are destroyed- sparking a huge amount of concern and urgency to understand their impact as carbon stores.
And there are several types of well-studied peat types found in these swamps, varying by composition, based upon the materials found in the locales, and the amount of water present in the peat.
There's so much more than just peat and water in these habitats, and much more to study.
These are precious environments.
They require us to understand, explore, and preserve them. As aquarists, we can do our part by attempting to replicate these habitats in our aquariums, and to breed the species which come to the hobby from these habitats. Yeah, not only will our work help us to get a better understanding of the ecosystem, it will (if we're lucky and diligent) relieve some of the pressures on these vulnerable wild populations.
Species from the genera Sphaerichthys, Desmopuntius, Rasbora, Betta, and Channa are well-represented in these habitats.
Average water depth in these swamp habitats ranges from about 1/2" to as much as 3 feet (approx. 0.1 meters to 0.9 meters). Researchers have found that these peat swamp fish communities are typically more species rich in habitats which offered higher levels of dissolved oxygen, interesting because we tend to think of swamp fish as being found typically in low oxygen environments, right?
That being said, there are plenty of fishes which have evolved to thrive in these habitats. For example, Betta hendra, one of the betta species, is only known to be found in the Sebangau forest! These are also specially adapted for life in the peat-swamp environment, with its lower dissolved oxygen levels. According to Fish Base, it's found in Found in, "...peat swamps with depth of about 5 to 50 cm and with no water current. The water was shaded by trees and bushes. Collected among the aquatic and marsh plants..."
(A great pic of B. hendra by our friend, Sumer TIwari)
Another gem from my research about dissolved oxygen levels and their impact on fish populations:
"Forest pools and canals in these regions have consistently lower dissolved oxygen levels the rivers and streams in the region do. This is probably due to the inherent nature ofthe aquatic habitat in peat swamp forests, where DO levels are kept low due to the high amount of tannins in the water (from the high organic matter content of the peat), with the accumulation of decaying organic matter depleting DO levels.
Additionally, there is low or no water flow (especially in the pools) which further ensure low levels of DO regardless of the lower surface temperatures of forest water bodies(Yule & Gomez 2009). Low concentrations of DO can make water uninhabitable for certain fish species, therefore the forest is likely to be a more challenging environment for fish survival."
Did you see the part about the tannins keeping dissolved oxygen levels lower? That's the first time I've heard that correlation made. Although, the next sentence clarified it for me, when it touched on the high level of organic matter depleting dissolved oxygen levels. So, my thinking is that the tannin is the result of the organic matter, but the organic matter itself is responsible for the lower oxygen levels.
This makes perfect sense, right?
We all know by now that too much botanical material added to the water in your aquarium in a short time period can result in depleted oxygen levels, leaving fishes gasping at the surface! If there is one "common botanical-style aquarium disaster trigger", that would be it. See- that happens in Nature happens in our aquariums. You can push it, but you can't hide from the consequences of trying to beat Nature's rules!
Interestingly, our captive aquariums might function in a very similar manner to the wild ecosystems.
The water of the peat swamps is very high in dissolved organic carbon, and it's thought by ecologists that the dissolved organic carbon is used as a substrate for microbial growth- thusly lowering the concentration of dissolved organic carbon in the water, and transferring energy from decomposing leaves and other materials to other trophic levels (defined as "hierarchical levels in an ecosystem, comprising organisms that share the same function in the food chain and the same nutritional relationship to the primary sources of energy.").
This would explain how tropical peat swamps support diverse, abundant flora and fauna despite incredibly low nutrient levels and lack of rapid leaf litter cycling, such as that which occurs in other types of tropical rainforests.
So, with some of this information in our grasp, how can we interpret it for use in our aquarium work? Now, sure, I could easily devote an entire piece to how you can recreate this habitat in your aquarium from a "functionally aesthetic" perspective- and we will. However, I'm not going to sell it short by just sort of touching on it here with a laundry list of, "Use this botanical!", or similar. Let's just touch on one aspect- what I feel is the most important, and then we can cover the rest of this stuff in future piece.
Personally, I believe that we'd be both wise- and challenged- to attempt to replicate the peaty soils of the swamps. I think that it's the whole game here.
Now, many of us have mixed feelings about utilizing peat in our aquariums; however, there ARE some sources of sustainably-harvested peat available, but you'll have to do your homework to find them. We've covered this conundrum a couple of years back right here in "The Tint."
Are there alternatives?
Well, sure. I think so.
In peat swamps, the peat layers may be well in excess of 3 feet (1m) deep. The floodplain forests are found along rivers, streams, coasts, and lakes. The seasonal flooding inundating the forests for short periods leads to an influx of sediment and mineral enrichment during high water periods.
These soils are best replicated by using "non-traditional" substrates, like...coconut-based materials, finely-crushed botanicals, mud, sediments, etc...
(If you're thinking that we should come out with a "NatureBase" substrate inspired by this habitat, your correct! I've already formulated a version, and have been testing it for some time. We'll definitely release it as a "limited release" substrate in the coming months!
There are some characteristics of these soils which will make them challenging in aquariums. For one thing, the physical characteristics of these materials will make them "behave differently" in water than traditional sands and other aquarium substrates. Peat, in its natural state, contains excessive amounts of water and is not exactly "sturdy" like sand or gravel because of its high permeability and has very low shear strength. And of course, it has a really low pH.
If we're trying to replicate the habitat as faithfully as possible, we'd want to use reverse osmosis/deionized water, or water with minimal carbonate hardness, and a soil with properties similar to peat. This could be challenging to manage for many hobbyists, because of the resulting pH. Not impossible- simply challenging.
We need to create a biological support web that is similar to that found in Nature, and that involves bacteria. We have a product, "Culture", which contains Purple Non Sulphur bacteria, which are extremely adaptive to low pH environments. We believe that this will make management of such systems a bit easier than it has been for hobbyists in years past.
Now, one thing to consider, of course, is that the fishes which reside in this habitat are intimately linked to it, and I think you'd do well to study the overall habitat. I could go on an on about each fish species, etc., but I think there are way better sources for that than I. What we need to discuss is really how to recreate the habitat more faithfully.
I also think that the aquarium configuration is important. I'd go with a smaller aquarium, depending upon the species you're wanting to keep, to create a very tightly controlled, cohesive environment. I'd look for a shallow, wide "footprint" for such an aquarium.
I don't presume to be an expert on planted aquariums, but I do know that some species, such as Cryptocoryne, are found extensively in these environments, and would be the natural and easy choice for plants in such an aquarium.
Filtration would be best accomplished with a canister or external power filter with gentle return flow, as water movement is minimal in these swamps. Plus, with a mix of rather buoyant substrate materials, you'd probably want to limit the heavy flow to keep them from blowing all over your tank!
I'd plant fairly densely, and intersperse lots of botanicals, to replicate some of the materials found in these swamps.
Perhaps you'd even want to include some palm fronds?
The maintenance of this aquarium would be no different than any of the Amazonian biotopes that we discuss so frequently here. Common sense water quality management, and regular water changes would go a long way towards maintaining a healthy environment for your little swamp!
Let's sort of leave it there, as we can go into much more aquarium-specific ideas on the recreation of this unique habitat in another blog post.
I hope that we've not only given you a few new insights on the peat swamps, but more important, inspired you to do further research on them. There is so much more than "tinted, low pH water" to the recreation of one of these habitats. It's going to require a lot of research and work to understand the unique dynamics of these fascinating ecosystems, and how to recreate them functionally in our home aquariums.
Let's roll up our sleeves and get to work!
Stay inspired. Stay creative. Stay observant. Stay brave...
And Stay Wet.