It's no secret that we have a long-time, and continuously evolving obsession with brackish-water mangrove habitats. When we launched "Estuary by Tannin Aquatics", our foray into the "botanical-style brackish aquarium", it was driven by an obsession with the functional and aesthetic aspects of this unique ecosystem. With a heavy emphasis on substrate, decomposition, and all of the good stuff that us "Tinters" seem to love, this more "honest" interpretation of the blackwater aquarium is proving irresistible to many of you!
Mangrove communities tend to accumulate nutrients, such as nitrogen and phosphorus, as well as some heavy metals and trace elements which become deposited into estuarine waters from terrestrial sources. These communities become sort of "nutrient sinks” for these materials. And of course, nature has a plan for this stuff: Mangrove roots, and the epiphytic algae often found on and among them, as well as bacteria, microorganisms, and a wide variety of invertebrates that reside there, take up and store the nutrients in their tissues. Mangroves also function as continuous sources of carbon, nitrogen, and other elements, as their living material (i.e.; leaves and epiphytic organisms and plants) die and are decomposed. Tidal flushing assists in distributing this material to areas where other organisms may utilize it.
And here's the other cool thing:
Leaf litter is extremely important in a Mangrove ecosystem! Other materials, including twigs, branches, and other botanical items, is a major nutrient source to many creatures which function as "consumers" in these ecosystems. A study conducted in the 1970's by Pool et al, showed that the leaf litter in brackish Mangrove ecosystems is composed of "...approximately 68 – 86 % leaves, 3 – 15 % twigs, and 8 – 21 % "miscellaneous" material."
Thanks for the leaf litter "recipe", scientist friends!
Now, Mangroves are different types of leaves than we are currently using in our blackwater tanks, but the concept is entirely familiar to us, right? (Oh, and by the way, it's totally okay to use mangrove leaves in your freshwater botanical-style blackwater aquarium!)
Once fallen, leaves and twigs decompose fairly rapidly in these habitats. As you might imagine, areas which have high tidal flushing rates, or which are flooded frequently, have faster rates of decomposition and export than other areas. Studies also found that decomposition of red mangrove litter proceeds faster under brackish conditions than under fresh water conditions. Oh, and as the researchers so eloquently stated, some of these habitats have "brownish-colored water, resulting from organic matter leaching from the mangroves."
Algal growth, biofilms, brown water...at 1.005 specific gravity. Does it get any better?
So, let's think of this for just a minute, in terms of "that thing we do"- botanical-style aquariums. Just change up the "media" from "blackwater" to "brackish water", with a specific gravity of 1.005. We collectively have a lot of experience managing higher-nutrient blackwater botanical systems, containing large numbers of leaves and other botanicals, right? Can this experience be applied to the brackish game? Of course it can!
Now, first off- I have no illusions about using live Mangrove plants (available as "propugles") to serve as "nutrient export" mechanisms as they do in nature. They just grow too damn slow and achieve sizes far beyond anything we could ever hope to accommodate in our home aquarium displays as full-grown plants. We've played with this idea in saltwater tanks for decades and it's really more of a novelty than a legit nutrient export mechanism.
However, we could at least grow a few, for the enjoyment of it all, and utilize faster-growing, adaptable aquatic plants to provide some natural nutrient export. And of course, we could skip the live Mangroves altogether, and just utilize some driftwood (as has been done for decades) pieces to simulate the roots...However, the similarity to the aesthetically-driven "Mangrove thicket" tanks of the past ends there! We'd continue on, concentrating on building up the other "functional" aspects of the Mangrove habitat! (You know, decomposing leaves, etc.)
Utilizing very rich aquatic soils, similar to what has been used in "dirted" tanks by aquatic plant geeks, yet with a buffering component (finer, aragonite or calcareous substrates), we could create a "workable" plant environment, couldn't we? And by managing the water quality with regular, frequent water changes, and careful, automated topoff to keep specific gravity constant at a low brackish level (like-this is a fundamental thing), wouldn't we be able to simulate this environment on at least a superficially functional level? Kind of like what we're doing with blackwater, leaf-litter-bed aquariums?
Now, we have to learn a bit more about the impact of high-nutrient substrates, decomposing leaf litter and such in brackish systems, but it's a totally cool experiment, IMHO!
Mangrove habitats also function as fish "nurseries" and feeding zones, assist in preventing shoreline erosion because of their ability to trap sediments in the low-energy waters of brackish estuaries and breaks up wave action within their maze of prop roots. These prop root systems are just screaming at us as fish geeks to play with. I've waded, snorkeled and scuba dived in Mangrove systems many times, and am always blown away by the myriad of tempting aquarium possibilities that they inspire!
Numerous "sublittoral/littoral" organisms utilize the prop root zone of red mangroves as their primary habitat. The "prop root zone" provides sessile filter feeding organisms, like such barnacles, muscles, tunicates, and bryozoans with a perfect environment in which to live and reproduce. There are sponges in brackish ecosystems, but they are highly specialized feeders, often deriving sustenance from a very specific type of dissolved organic food source, so we're unlikely to be working with them. Oh, you also have the "seldom-kept-in-aquaria-intentionally" polychaete worms and "boring" crustaceans, like isopods.
Yeah...there is so much going on in this area...so much for us to play with as hobbyists, In fact, part of me is actually a bit guilty for unleashing the "Estuary" idea so early on (2.5 years) in Tannin's existence, as we're just now starting to venture out and unlock some secrets in the blackwater/botanical game...But I think that the two can develop together and spur on new hobby advances. In fact, I think that they already have...
So, if you were contemplating playing around with this whole brackish water/botanical-style aquarium game, now that we're heading into the heart of "Aquarium Season", it's a good time to experiment! We're looking forward to seeing more an more of your experiments and ideas coming to light...in this tinted, slightly salty world!
Stay bold. Stay excited. Stay adventurous. Stay curious...
And Stay Wet.