So you think there is competition in an aquarium? OK lets take a look at competition. I am going to quote others for this and to keep the space of this post lower I am not going to include the diagrams and photos. Those who wish to see them can follow the reference link.
Species Interactions and Competition
By: Jennifer M. Lang (University of Dayton) & M. Eric Benbow (University of Dayton) © 2013 Nature Education
Citation: Lang, J. M. & Benbow, M. E. (2013) Species Interactions and Competition. Nature Education Knowledge 4(4):8
Introduction Organisms live within an ecological community, which is defined as an assemblage of populations of at least two different species that interact directly and indirectly within a defined geographic area (Agrawal et al. 2007; Ricklefs 2008; Brooker et al. 2009). Species interactions form the basis for many ecosystem properties and processes such as nutrient cycling and food webs. The nature of these interactions can vary depending on the evolutionary context and environmental conditions in which they occur. As a result, ecological interactions between individual organisms and entire species are often difficult to define and measure and are frequently dependent on the scale and context of the interactions (Harrison & Cornell 2008; Ricklefs 2008; Brooker et al. 2009). Nonetheless, there are several classes of interactions among organisms that are found throughout many habitats and ecosystems. Using these classes of interactions as a framework when studying an ecological community allows scientists to describe naturally occurring processes and aids in predicting how human alterations to the natural world may affect ecosystem properties and processes.
At the coarsest level, ecological interactions can be defined as either intra-specific or inter-specific. Intra-specific interactions are those that occur between individuals of the same species, while interactions that occur between two or more species are called inter-specific interactions. However, since most species occur within ecological communities, these interactions can be affected by, and indirectly influence, other species and their interactions. The ones that will be discussed in this article are competition, predation, herbivory and symbiosis. These are not the only types of species interactions, just the most studied — and they are all parts of a larger network of interactions that make up the complex relationships occurring in nature.
Competition Competition is most typically considered the interaction of individuals that vie for a common resource that is in limited supply, but more generally can be defined as the direct or indirect interaction of organisms that leads to a change in fitness when the organisms share the same resource. The outcome usually has negative effects on the weaker competitors. There are three major forms of competition. Two of them, interference competition and exploitation competition, are categorized as real competition. A third form, apparent competition, is not. Interference competition occurs (Holomuzki et. al 2010) Figure 1.occurring in nature.
When an individual directly alters the resource-attaining behavior of other individuals, the interaction is considered interference competition. For example, when a male gorilla prohibits other males from accessing a mate by using physical aggression or displays of aggression, the dominant male is directly altering the mating behavior of other males. This is also an example of an intra-specific interaction. Exploitation competition occurs when individuals interact indirectly as they compete for common resources, like territory, prey or food. Simply put, the use of the resource by one individual will decrease the amount available for other individuals. Whether by interference or exploitation, over time a superior competitor can eliminate an inferior one from the area, resulting in competitive exclusion (Hardin 1960). The outcomes of competition between two species can be predicted using equations, and one of the most well known is the Lotka-Volterra model (Volterra 1926, Lotka 1932). This model relates the population density and carrying capacity of two species to each other and includes their overall effect on each other. The four outcomes of this model are: 1) species A competitively excludes species B; 2) species B competitively excludes species A; 3) either species wins based on population densities; or 4) coexistence occurs. Species can survive together if intra-specific is stronger than inter-specific competition. This means that each species will inhibit their own population growth before they inhibit that of the competitor, leading to coexistence.
Another mechanism for avoiding competitive exclusion is to adopt alternative life history and dispersal strategies, which are usually reinforced through natural selection. This mechanism reduces competitive interactions and increases opportunities for new colonization and nutrient acquisition. The success of this is often dependent upon events (such as tide, flood, or fire disturbances) that create opportunities for dispersal and nutrient acquisition. Consider that Plant Species A is more efficient than Plant Species B at nutrient uptake, but Plant B is a better disperser. In this example, the resource under competition is nutrients, but nutrient acquisition is related to availability. If a disturbance opens up new space for colonization, Plant B is expected to arrive first and maintain its presence in the community until Plant A arrives and begins competing with Plant B. Eventually Plant A will outcompete Plant B, perhaps by growing faster because Plant A is more efficient at nutrient acquisition. With an increasing Plant A population, the Plant B population will decline, and given enough time, can be excluded from that area. The exclusion of Plant B can be avoided if a local disturbance (for example, prairie fires) consistently opens new opportunities (space) for colonization. This often happens in nature, and thus disturbance can balance competitive interactions and prevent competitive exclusion by creating patches that will be readily colonized by species with better dispersal strategies (Roxburgh et al. 2004) (Figure 2). The success of the dispersal versus nutrient acquisition trade-off depends, however, on the frequency and spatial proximity (or how close they are) of disturbance events relative to the dispersal rates of individuals of the competing species. Coexistence can be achieved when disturbances occur at a frequency or distance that allows the weaker, but often better dispersing, competitor to be maintained in a habitat. If the disturbance is too frequent the inferior competitor (better disperser) wins, but if the disturbance is rare then the superior competitor slowly outcompetes the inferior competitor, resulting in competitive exclusion. This is known as the intermediate disturbance hypothesis (Horn 1975, Connell 1978).
Apparent competition occurs when two individuals that do not directly compete for resources affect each other indirectly by being prey for the same predator (Hatcher et al. 2006). Consider a hawk (predator, see below) that preys both on squirrels and mice. In this relationship, if the squirrel population increases, then the mouse population may be positively affected since more squirrels will be available as prey for the hawks. However, an increased squirrel population may eventually lead to a higher population of hawks requiring more prey, thus, negatively affecting the mice through increased predation pressure as the squirrel population declines. The opposite effect could also occur through a decrease in food resources for the predator. If the squirrel population decreases, it can indirectly lead to a reduction in the mouse population since they will be the more abundant food source for the hawks. Apparent competition can be difficult to identify in nature, often because of the complexity of indirect interactions that involve multiple species and changing environmental conditions.
Predation and Herbivory
Predation requires one individual, the predator, to kill and eat another individual, the prey (Figure 3). In most examples of this relationship, the predator and prey are both animals; however, protozoans are known to prey on bacteria and other protozoans and some plants are known to trap and digest insects (for example, pitcher plant) (Figure 4). Typically, this interaction occurs between species (inter-specific); but when it occurs within a species (intra-specific) it is cannibalism. Cannibalism is actually quite common in both aquatic and terrestrial food webs (Huss et al. 2010; Greenwood et al. 2010). It often occurs when food resources are scarce, forcing organisms of the same species to feed on each other. Surprisingly, this can actually benefit the species (though not the prey) as a whole by sustaining the population through times of limited resources while simultaneously allowing the scarce resources to rebound through reduced feeding pressure (Huss et al. 2010). The predator-prey relationship can be complex through sophisticated adaptations by both predators and prey, in what has been called an "evolutionary arms race." Typical predatory adaptations are sharp teeth and claws, stingers or poison, quick and agile bodies, camouflage coloration and excellent olfactory, visual or aural acuity. Prey species have evolved a variety of defenses including behavioral, morphological, physiological, mechanical, life-history synchrony and chemical defenses to avoid being preyed upon (Aaron, Farnsworth et al. 1996, 2008)
Another interaction that is much like predation is herbivory, which is when an individual feeds on all or part of a photosynthetic organism (plant or algae), possibly killing it (Gurevitch et al. 2006). An important difference between herbivory and predation is that herbivory does not always lead to the death of the individual. Herbivory is often the foundation of food webs since it involves the consumption of primary producers (organisms that convert light energy to chemical energy through photosynthesis). Herbivores are classified based on the part of the plant consumed. Granivores eat seeds; grazers eat grasses and low shrubs; browsers eat leaves from trees or shrubs; and frugivores eat fruits. Plants, like prey, also have evolved adaptations to herbivory. Tolerance is the ability to minimize negative effects resulting from herbivory, while resistance means that plants use defenses to avoid being consumed. Physical (for example, thorns, tough material, sticky substances) and chemical adaptations (for example, irritating toxins on piercing structures, and bad-tasting chemicals in leaves) are two common types of plant defenses (Gurevitch et al. 2006) (Figure 5).
Symbiosis: Mutualism, Commensalism and Parasitism
Symbiosis is an interaction characterized by two or more species living purposefully in direct contact with each other. The term "symbiosis" includes a broad range of species interactions but typically refers to three major types: mutualism, commensalism and parasitism. Mutualism is a symbiotic interaction where both or all individuals benefit from the relationship. Mutualism can be considered obligate or facultative. (Be aware that sometimes the term "symbiosis" is used specifically to mean mutualism.) Species involved in obligate mutualism cannot survive without the relationship, while facultative mutualistic species can survive individually when separated but often not as well (Aaron et al. 1996). For example, leafcutter ants and certain fungi have an obligate mutualistic relationship. The ant larvae eat only one kind of fungi, and the fungi cannot survive without the constant care of the ants. As a result, the colonies activities revolve around cultivating the fungi. They provide it with digested leaf material, can sense if a leaf species is harmful to the fungi, and keep it free from pests (Figure 6). A good example of a facultative mutualistic relationship is found between mycorrhizal fungi and plant roots. It has been suggested that 80% of vascular plants form relationships with mycorrhizal fungi (Deacon 2006). Yet the relationship can turn parasitic when the environment of the fungi is nutrient rich, because the plant no longer provides a benefit (Johnson et al. 1997). Thus, the nature of the interactions between two species is often relative to the abiotic conditions and not always easily identified in nature.
Commensalism is an interaction in which one individual benefits while the other is neither helped nor harmed. For example, orchids (examples of epiphytes) found in tropical rainforests grow on the branches of trees in order to access light, but the presence of the orchids does not affect the trees (Figure 7). Commensalism can be difficult to identify because the individual that benefits may have indirect effects on the other individual that are not readily noticeable or detectable. If the orchid from the previous example grew too large and broke off the branch or shaded the tree, then the relationship would become parasitic.
Parasitism occurs when one individual, the parasite, benefits from another individual, the host, while harming the host in the process. Parasites feed on host tissue or fluids and can be found within (endoparasites) or outside (ectoparasites) of the host body (Holomuzki et al. 2010). For example, different species of ticks are common ectoparasites on animals and humans. Parasitism is a good example of how species interactions are integrated. Parasites typically do not kill their hosts, but can significantly weaken them; indirectly causing the host to die via illness, effects on metabolism, lower overall health and increased predation potential (Holomuzki et al. 2010). For instance, there is a trematode that parasitizes certain aquatic snails. Infected snails lose some of their characteristic behavior and will remain on the tops of rocks in streams where food is inadequate and even during peaks of waterfowl activity, making them easy prey for the birds (Levri 1999). Further, parasitism of prey species can indirectly alter the interactions of associated predators, other prey of the predators, and their own prey. When a parasite influences the competitive interaction between two species, it is termed parasite-mediated competition (Figure 8). The parasite can infect one or both of the involved species (Hatcher et al. 2006). For example, the malarial parasite Plasmodium azurophilum differentially infects two lizard species found in the Caribbean, Anolis gingivinius and Anolis wattsi. A. gingivinius is a better competitor than A. wattsi but is susceptible to P. azurophilum, while A. wattsi rarely contracts the parasite. These lizards are found coexisting only when the parasite is present, indicating that the parasite lowers the competitive ability of A. gingivinius' (Schall 1992). In this case, the parasite prevents competitive exclusion, therefore maintaining species diversity in this ecosystem.
Summary
The species interactions discussed above are only some of the known interactions that occur in nature and can be difficult to identify because they can directly or indirectly influence other intra-specific and inter-specific interactions. Additionally, the role of abiotic factors adds complexity to species interactions and how we understand them. That is to say, species interactions are part of the framework that forms the complexity of ecological communities. Species interactions are extremely important in shaping community dynamics. It was originally thought that competition was the driving force of community structure, but it is now understood that all of the interactions discussed in this article, along with their indirect effects and the variation of responses within and between species, define communities and ecosystems (Agrawal 2007).
from
http
/www.nature.com/scitable/knowledge/library/species-interactions-and-competition-102131429
Sorry about being so long winded but I did not want to leave myself open to criticism that I left anything out even if it is not really relevant to this discussion.
Now that we have reached a basic understanding about what competition is all about, the one theme that runs trhough the above from start to finish- is this is in nature, in functioning self sustaining ecosystems. And therein lies the rub. An aquarium could not be further from being a real ecosystem. We can go into the woods and study the balance between plants and bacteria, we can do it in ponds, in oceans.
An aquarium is not
[SIZE=12pt]"an ecological community"[/SIZE], it can not be defined as such. Communities exist naturally, nothing in any fish tank got their in any natural way. From the actual container to almost every single thing in it, they all got there the same way. Human beings put it all there. Most aquariums are not even close to being natural. We put plants native to Asia in tanks with fish from Brazil and water and whatever it contains from our local tap. An aquarium is in no way natural beyond the fact that everything that goes into it that is not man made actually does exist somewhere in nature. The closest we can come in this respect is a biotope and even then it is nowhere near a real natural system unless one can put all of the organisms and resources found in that biotope nature into such a tank ecosystem.
And as for the resources in an aquarium, whether you wish to discuss plants, fish, inverts, bacteria etc. Almost all of them are there because of the direct or indirect actions of the human fish keeper. Even the water goes in by artificial means. I would argue that while we as fish keepers usually want colonies of bacteria in our tanks, we exercise little control over getting them intentionally. And when it comes to plants this is especially true.
We select the types and number and size of every single plant that goes into a tank. Moreover, we put in many more plants than the resources in a tank can support. Go ahead and set up a tank and cover 75% of the substrate with them. Now sit back and watch your tank. Close the lid and add nothing to that tank at all. Put it in natural sunlight or even use a light to simulate the sun similar to how light would be in nature. How long will the plants live? There is no competition for resources in an aquarium because there are none. We have to add them regularly. If we do not, the plants will die. Looking at this another way, plant a tank slightly, keep fertilizing it and the plants grow and spread. The more nutrients for the plants we make available, the more they spread and grow until finally they have to pruned. None of this is competition, not of it is natural, it is not an ecosystem.
The same would apply to the fish we add. If human intervention does not add food, they will starve to death.
And lets touch on the nitrifying autotrophs now. Fish keepers want these in our tanks. And we put them there intentionally and encourage them to grow just like we do with live plants. We add bacteria in any number of ways, we almost always get some simply by filling our tanks with our tap water. But we also seed tanks with bacteria carrying items from other tanks or even buy and add them. Again almost none of this is natural except the presence of bacteria in tap water. But it still only gets into a tank because of human action.
So it should be obvious to most folks that there is no ecosystem in an aquarium and further, humans do not compete with anything in a tank. Despite not competing, we have total control over what happens in a tank. Even when that control may be accidental rather than intentional. An example is new fish with unseen ich going into a tank. nobody wants to introduce ich, but our actions cause it.
Here is an example of natural competition between bacteria and plants in a tank. Set it all up and get it healthy and functioning and then stop interfering. No electricity, no fish food, no plant nutrients. add nothing. Now tell me what the last things to die in that tank will be. I guess they be whatever out competed all the rest. What you will find is the nitrifying bacteria will be some of the last life forms to go.
And it is for these reasons that one cannot refer to what goes on in an aquarium as competition. I can cause the bacteria in a planted tank to multiply simply by removing some number of plants because i don't like the way they look. Have the bacteria then out competed the plants or have I changed the balance by interfering?
And for all of the above reasons the only way one can discuss actual competition between plants and autotrophic nitrifiers is to look to nature. And when one does, what you see in terms of the interaction between the two species is not competitive exclusion but rather a degree of cooperation and symbiosis. That is why one finds nitrifiers living on and alongside plants in nature and even in tanks. That is why neither species eliminates the other in competition. They share the resources. And they do this in terms of ammonia and ammonium because they exist together when in water (even the water in soil) and because plants normally take up NH4 while the bacteria NH3. this facilitates sharing resources.
And it would be very simple to end the discussion here, but there are instances where there is ammonia in water whose pH causes total ammonia to be 100% ammonium. One hears how nitrification ceases. An urban myth. There are strains of bacteria which normally thrive on NH3 which also are present and working in water and soil with a pH of 4.0 or a tad lower. It turns out they have some receptors for NH4. When faced with a no available NH3 environment, they are able to process the ammonium, albeit less efficiently than they can process NH3. But don't take my word for it, read this:
Nitrification in a Biofilm at Low pH Values: Role of In Situ Microenvironments and Acid Tolerance http/aem.asm.org/content/72/6/4283.full
I would note that in nature, in biology, in an ecosystem many resources are limited which fosters competition between species. In an aquarium the resources present are there soley because we add them. A tank needs constant additions for whatever is in it to survive. If we stop putting things into the tank and removing the bad things, everything dies. Neither he plants, fish or bacteria can up and move to a nearby tank. They can not evolve. They can do nothing to change this. There are no naturally occurring resources in a tank.
So if one want to understand the relationships between plants and nitrifying bacteria, one must study these in nature in a functioning ecosystem to understand whether they compete each other into extinction or they manage to coexist. At best you can argue that the actions of the human fish keeper come closest to being competition because what we do determines all that happens in a tank. This might qualify as interference competition, except we are not a part of the system. Whether a tank exists or not, whether it thrives or not has very little to do with natural competition and everything to do with fish keeper behavior.
In nature many organisms share resources without eliminating each other. They may affect the population sizes, but that is far from out competing. A tank Is a system where the resources are not limited because they are constantly being renewed by a non-member of that community, not by nature. Like I said, take and established healthy tank with plants and fish and nitrifying bacteria in it and remove the fish and stop adding fertilizer and the last things alive will become the bacteria. The nitrifiers will just go dormant and some can last a very long time before they are all gone and not able to recover. Bottled bacteria can survive in a bottle easily for a year, can any plants do this? Does this mean I can argue that the bacteria can out compete the plants? If i put a live plant into the same dark resourceless bottle with the bacteria, it will die and what results may actually help the bacteria to survive even longer. Is this competition?
If you look at the bacteria in nature, they are very often found in the substrate, just as they are in many aquariums. They do well there because there is no light. The ammonia they need also penetrates to some extent. So even as the plants are busy taking up ammonium via their leaves, there is NH3 for the bacteria near the plant roots. And those roots may even be supplying the bacteria with the O they need to function. In the absence of the intervention of man adding nutrients via crop fertlization and other ways to create run offs into natural aquatic ecosystems, the amount of ammonia available for aquatic plants is normally limited. If the plants are taking up all the ammonia, why are there so many nitryfiyng bacteria and archaea in environments where plants are thriving without the interference of man?
And even when man adds fertilizers to encourage plant growth in nature, this does not result in the plants eliminating bacteria, it results in more bacteria. And this is true even though the plants can uptake the NH4 at a much faster rate than the bacteria can uptake the NH3.
So I will simply toss the competition ball back into your court. All you have to do is show how species competition can happen in a basically man made and sustained artificial
environment. How can any species out compete another when the nutrient resources are not limited. Each will find its own niche and they will coexist. neither will eliminate the other.
And none of the above has delved into the nitrogen cycle itself. I have stated that plants are an integral part of the nitrogen cycle along with the bacteria and other organisms. I am happy to read any scientific work that you can provide which shows this not to be the case. I would remind you that there are strrains of AOA and AOB that can exist at ammonia levels too low to support plants. And some of these strains are in our tanks. (Read Tom Barr on this. see the quote from him further down in reference to elodia and ammonia at .5 ppm.)
In nature, when man does not artificially introduce nitrate into the environment, where does the nitrate which plants consume originate? If the plants are out competing the bacteria, there should often be very little or no nitrate.
Nitrate salts are found naturally on earth as large deposits, particularly of
Chile saltpeter, a major source of sodium nitrate.
Nitrites are produced by a number of species of
nitrifying bacteria, and the nitrate compounds for
gunpowder (see this topic for more) were historically produced, in the absence of mineral nitrate sources, by means of various
fermentation processes using urine and dung. Nitrates are found in man-made fertilizers.
from
http/en.wikipedia.org/wiki/Nitrate
Eliminate man made ferts and the primary way for many environments to have a supply of nitrate is from bacterial action. If the plants out competed the nitrifying bacteria in such habitats, they, in essence, would be committing suicide. So can you argue that plants do this and provide the science to back it up?
But read up on plants and nutrients. Most plants do not subsist on ammonium as their only or even primary source of N, they also use nitrate. Some plants actually rely more on nitrate than ammonium. Read what Ton Barr wrote in 2005 when asked "Is there a preference by the plants for ammonia vs. nitrates?"
It depends on the plant in question.
There is no rule because the plants we keep have not all bene tested, only maybe 20 or so.
Wheat for example prefers NO3.
Generally the issue is less defind by increasing growth ratesas it is fish health and algae blooms.
I find it very hypocritical for folks to suggest NH4 dosing, high fish loading etc and then in the same breath tell me that the high NO3 which really are not that high and has a lot more dosing flexibility is better for plants.
NH4 is very toxic to small fish and very useful(Increasingly more as the light intensities are increased) when added can easily induce algae blooms.
Now all aquatic plants do quite well with a trace amount of NH4 from fish etc, and most from KNO3 dosing.
Why folks would like to increase the growth of plants more is really the key question here. At what cost for the method involved?
In terrestrial agriculture, do we have fish and shrimps? No.
Do we have algae? Not anything that bother's crops or farmers.
So it these cases, yes, the addition for some crops is very useful.
Plants use more energy to use NO3, but they can store and have a lot more access to larger amounts by a factor of 100-1000X more than NH4.
I'd rather have a slightly slower growth, than higher growth with a lot more risk to fish health and algae blooms.
If you look at Diana Walstad's book on this topic, you'll see my point.
There is a figure that illustrates that NH4 is preferred in Elodea.
But at what concentration?
Yuo will note that the rate of uptake falls with NH5 as it hits 0.5ppm.
It's zero, the rate of uptake is essentially zero there.
Now look what occurs with NO3 all the way down?
It starts up and is fast when the levels of NH4 are less than about 0.5ppm of NH5.
Try adding 1-2ppm of NH4 to your tank sometime, it'll kill all your fish.
Try adding 10-20ppm of NO3. No effect.
from
http/www.barrreport.com/showthread.php/2405-Ammonia-vs-NO3
(Tom is more of a plant expert than a bacteria expert. I can add 1 ppm of ammonia to a tank with a variety of fish in it and if the pH is low enough to hold down the amount of toxic NH3, the ammonia will be gone long before it harms and certainly before it kills any fish. So he was not quite accurate in that respect/ perhaps if he tried to maintain that level for an extended period of time it would harm fish. But to do that he would also have to either inhibit the growth of any AOB or else keep adding ever increasing amounts of ammonia to stay ahead of the bacteria in order to maintain that 1 ppm level.)
or in 2007
I'm not trying to get rid of NO3...........just NO2/NH4.
Good steady plant growth=> no NH4.
Good aeratrion, aerobic filtration=> no NH4/NO2.
from
http/www.barrreport.com/showthread.php/3356-Filtermedia-to-break-down-ammonia-nitrite-and-nitrate
Gee, Tom Barr is indicating tank ammonia in a planted tank will not be there due, to some extent, from aerobic filtration- I believe this means bacteria . And I can find more quotes where Tom indicates nitrification and plants both are ongoing in even the highest tech tanks.
As for that old objection that light + ammonia = algae, I can show you how to prevent this during cycling with plants where ammonia is being added to fill the cycling gap between ammonia creation and plants via the presence of bacterial colonies. It is not all that hard to do over the period of time involved and with the amount of ammonia needed. In fact I will be doing just that in a forthcoming article for the site. This is a far cry from my stating that one can be adding largerish doses of ammonia to a planted tank for any amount of time while leaving the lights one etc . One needs to do things a specific way to prevent the algae. But the way is simple and a lot easier for a newbie than trying to plant up a very sophisticated heavily planted first tank. And it will work in any level of plants that is not extremely low, i.e. a tank with only a couple of small plant, and it will work all the way up to a heavily planted tank.
I am happy to hear from anyone as to why any aquarium is actually a functioning ecosystem if you feel I am wrong in this respect. I would love to hear how plants and bacteria can compete in an environment that is essentially devoid of naturally occurring resources. To hark back to my comment about a race between and adult and a child the adult will always win unless I jump on my Harley, ride out onto the track and scoop up the child and speed past the adult and across the finish line. The child did not outrun the man, human interference cause the child to cross the line first. What is the real difference between this and the fish keeper deciding how and what to put into a tank? if you slant the race, you slant the outcome. If you want to know about plant/bacteria competition look the those studies I quoted and which three dismissed as not being at all relevant, that is the only way to get a valid answer here.
How can we talk about competition in an aquarium when the main job of the fish keeper is to keep everything in the tank healthy and thriving, nature itself provides almost nothing directly. We actively work to blunt competition in a tank.
