Aquatic Plant life, unifying principles

Evolution: Theodosius Dobzhansky (1900-1975) said “Nothing in biology makes sense except in light of Evolution.”1 Aquatic macrophytes2 possess a size and diversity that is truly spectacular in the plant kingdom. Aquatic macrophyte diversity covers roughly 440 genera covering 103 families of embryo bearing plants alone (Cook 1999). Cook suggest that embryo bearing plants have re entered the water at least 222 times and perhaps as much as 271 times in the past evolution of aquatic plants. Some of the oldest known angiosperm plants are aquatic, unlike past contentions that the world’s aquatic seed plants returned to the water much later in evolution, there is evidence from fossils in China that show that Archaefructus was aquatic and among the first known flowering plants (Dilcher 2002, Stokstad 2000). This means that some angiosperm aquatic plants evolved in the water and stayed there while some did evolve on to land only to later return to their aquatic past. It should not be overlooked that not all plants followed this same evolutionary pathway nor did many algae. Table one shows the orders that possess families that have aquatic representatives.

Order

Relative number of aquatic families/genera



Podostemonales

Exclusively Aquatic



Hydrocharitales

Exclusively Aquatic



Zosterales

Exclusively Aquatic



Nymphaeales

Exclusively Aquatic



Alismatales

Exclusively Aquatic



Typhales

Exclusively Aquatic



Pontederales

Exclusively Aquatic



Hippuridales

Exclusively Aquatic



Hydrostaciyales

Exclusively Aquatic



Hydatellales

Exclusively Aquatic



Lamiales

Two or more aquatic families



Haloragales

Two or more aquatic families



Myrtales

Two or more aquatic families



Caryophllales

Two or more aquatic families



Arales

Two or more aquatic families



Campanulales

Two or more aquatic families



Cyperales

Two or more aquatic families



Eriocaulales

Two or more aquatic families



Zingerales

Two or more aquatic families



Asparagales

Two or more aquatic families



Poales

Four or more aquatic genera


Primulales

Four or more aquatic genera


Araliales

Four or more aquatic genera


Anterales

Four or more aquatic genera


Gentlanales

Four or more aquatic genera


Fabales

Four or more aquatic genera


Saxifragales

Orders with three or less aquatic genera


Solanales

Orders with three or less aquatic genera


Capparidales

Orders with three or less aquatic genera


Droserales

Orders with three or less aquatic genera


Theales

Orders with three or less aquatic genera


Philydrales

Orders with three or less aquatic genera


Juncales

Orders with three or less aquatic genera


Euphobiales

Orders with three or less aquatic genera


Nelumbonales

Orders with three or less aquatic genera


Liliales

Orders with three or less aquatic genera


Piperales

Orders with three or less aquatic genera

Balsaminales

Orders with three or less aquatic genera

Gefamtales

Orders with three or less aquatic genera

Ranunculales

Orders with three or less aquatic genera






The organization of living things can be seen like a pyramid or tree with seven major levels or categories: Kingdom, Phylum, Class, Order, Family, Genus, Species. The kingdom Plantae has recently included green algae and red algae on the basis of molecular and biochemical criteria (Campbell 1999). Traditional organizational schemes considered green and red algae in other kingdoms in the past but the new research shows a clearer lineage than past methods and the DNA techniques have elucidated many unknown relationships and answer many questions while raising many questions as well (Bhattacharya and Medlin L 1998). Many plant discoveries have been made using algae, such as CO2 fixation reactions in photosynthesis by Calvin, Benson, and Bassham in the 1940’s and 1950’s (Calvin 1989). Many researchers will often refer to many marine macro algae as “plants” (Littler and Littler, Chapman, et al) they are large and leafy much like flowering plants. Freshwater macro algae such as Chara and Nitella are often mistaken for vascular plants such as Najas. Marine kelps such as Protelsia look very much like small palm trees and Caulpera possesses rhizoids and stolons runners much like that of vascular plants. There is a general public perception that algae are less advanced, but in many ways, they are more advanced for the habitat that they live.

While a number of algae possess habitats in soil and terrestrial systems, the terrestrial and aquatic “embryophytes” plants are what most of the public tend to think of when they speak of plants and algae. These include bryophytes (Riccia), lycophytes (Isoetes), pteriophytes (Microsorium) and seed plants (Hygrophila). Aquatic researchers use the term “Macrophytes” to include similar morphological plant like algae such as Nitella and many times the term “Microphyte” for smaller algae. Some Cyanobacteria are considered macrophytes such as Lygnbya while some green algae such as Cladophora aerogiphilia, (Marimo balls) would be considered macrophytes as well. Chara (Stone wort) would be considered a macrophyte, while Ankistrodesmus (Green dust algae) would not be. These two “plants” are in different ecological niches (Bowes 2004). This difference requires each to have different strategies for growth and genetic persistence in the aquatic environment.

The Niche concept: Many aquarist fall into the trap of equating small microphytes into the same niche as the larger Macrophytes. A single celled alga has very little nutrient demand to survive and grow while billion celled Echinordorus will need a much larger concentration to maintain the similar rates of growth relative to the size ratios (See figure 1).

Nutrient uptake dynamics




Where V = velocity of uptake by organism, V max is the maximum uptake rate, V’s units are mol/time so this is a “rate of uptake”. Ksp ½ is the half saturation constant used to compare two different organisms uptake rate. When the Substrate is very low, the microphyte has the advantage and the uptake line goes almost to zero at the origin. The macrophyte uptake rate stops before zero and this means that it takes a certain critical concentration of substrate before the macrophyte will induce substrate uptake. When the concentration of the substrate increases further, the macrophyte them has the uptake advantage. This model is counter to past assumptions from aquatic plant hobbyist about excess nutrient substrates causing algae blooms as it shows that the macrophytes have the uptake advantage in the ideal model.

See footnote for more information3.

This is one reason why algae can persist for months even when the aquarist performs many water changes, uses nutrient chemical removers and activated carbon. The plants just stop growing and waits, algae can do the same thing and produces resting spores that are activated when ammonium (NH4+) or large CO2 variations occurs (Barr 1998). There are other algae inducers, generally these involve a lack of something rather than an excess. Algae possess much higher surface to volume ratios than plants, this allows them to be far more competitive and responsive at low concentrations of nutrient substrates. Many algae possess enzymes that allow cleavage of organically bound PO4 and NO3 (Münster, Heikkinen and Knulst 1998). Algae also do not have internal transport of nutrients (nuisance algae, Kelps and other larger macrophytes have transport systems and morphology). Past literature on culturing aquatic plants dealing with algae nuisances over looked this niche concept and nutrient uptake dynamics. This has lead to many myths and problems relating to plant growth health and problems with algae.

Size: The Victorian Water (Victoria amazonica) lily possesses some of the largest leaves known in the plant kingdom (7 feet in diameter!) and are able to support a small 65 pound child floating on the water while the tiny Wolffia is one of the world’s smallest flowering plants, at 1 to 1.5 mm long yet even these two seeming opposite plants are very similar. Both plants have the same fundamental similar processes and have the same basic architecture. Both plants have flowers, chloroplast, emergent floating leaved aquatic plants, similar biochemical pathways and nutrient needs. Both are genetically very similar. Are they in the same niche?

Temperature: Other macrophytes such as Chara and Veronica can be found in the desert south west of the United States in springs at 40C or higher (Barr 2002) and Hydrilla is also found up to 40C in some locations (Bowes 2004). Echinodorus berteroi can be found in similar conditions in its native range in the Santa Ynez river valley (Barr 2003). On the other extreme, Potamogeton filiformis and Hippuris vulgaris have been found under frozen ice lakes in Greenland (Pedersen and Brodersen 2003).

Depth: Various aquatic mosses Chara have been found in Lake Tahoe to several hundred meters (Hutchinson 1975) and Crater lake has reported some of deepest embryophytes observed at 253 meters and a sample was collected at a depth of 221 meters while most vascular plants are limited to the upper 10 meters (Larson 1988, Sculpthorpe 1967). The aquatic habitat is very heterogeneous, it changes through time, hours, days weeks, months and years and sometimes decades or longer.

Ecology: Ecology deals with changes of organisms through space and time. The Aquatic habitat changes dramatically through a year’s time. Consider the Amazon basin. Water levels change up to (Melack et al 2001, Sioli 1984) 15 meters are common. The amount of light reaching the plant changes dramatically under these conditions. Vascular plants cannot survive for long periods below 10 meters or so due in large part hydrostatic pressure but also light will play a critical role due to attenuation of light by the water and changes in turbidity (Brenner 2003, Payne 1982, Dale 1981, Bodkin et al 1980). Wet seasons are punctuated by large debris covering and dislodging plants. While a through discussion may seem appropriate here, a Limnology text is a good source for more on the theory of light attenuation and a more thorough coverage in another later chapter will address this topic in full. The main point here is that Submersed Aquatic Plants(SAM’s) have enormous changes in their environment through space and time.

Nutrients: SAM’s can obtain their nutrients from both the substrate and the water column (Cedergreen, Madsen 2002, 2001). This makes them unique and specific when address the issue of whether they prefer the substrate or the water column for a nutrient source. Most researchers that study SAM’s conclude that if the nutrients are in the water column in non-limiting conditions, they will use those. If conditions become limiting in the water column, the SAM’s will use the nutrients in the substrate (Bowes 2004). In order for a researcher to conclude that a plant prefers one source over another, we should see an increase in growth rates from one source. The data does not show this to be the case. What much of the data does show is that aquatic plants do use the substrate for a nutrient source in most cases, but this is due to the water column being limited, not because the plants were given a choice as to a source. Future studies at UC Davis will investigate the isolated substrate influences (No water column nutrient sources) on SAM’s relative growth rates and these can then be compared to water column dosing of nutrients.

Correlations: Larger plants need more nutrients and carbon than the algae although past correlations have caused problems and lead to the aquarist assuming NO3 and PO4 are the causes of algae. Many aquarist have been lured into the notion of excess nutrients cause nuisance algae, but correlation of excess nutrients does not imply causation. The plants are not taking in the NO3 or the PO4 due to something else, most often it will be poor CO2 and NO3 and/or too many fish and not enough plants. Many aquarist want to place a direct correlation with algae and excess nutrients, but the issue is that the plants are not using the nutrients. This problem should be approached by asking “Why aren’t they using the PO4 and NO3?” When the plants stop growing, algae have their chance to grow. The plants stop growing and stop removing the NH4. Their surfaces become inactive, their nutrient contents will leech out of their leaves more when a stressed (Johnston 1991). This leeching effect plus decreased NH4 uptake can allow algae to settle on plant leaves and grow very well. The algae are non-limited while the plants are limited. Algae prefer CO2 as well like plants (Both use CO2 to fix carbon and may use or store malic acids (CAM and C4 plants or reduce HCO3 to CO2), but they do not need much relative to the plants. The goal is plant growth therefore the focus should be to provide the plants with the proper level of nutrients, CO2 and light. Algae have the advantage and grow well when the plants are not growing well. Past recommendations regarding PO4 removers only showed part of the problem, it caused the algae to slow down temporarily, but the plants slowed down their growth as well. The long-term effect selected for the algae, which are better able and better adapted at low levels of PO4, NH4 and NO3 in the water column.

Rate of growth: Growing well and growing slowly are different terms. If a tank has lower light, then the plants can grow slower but still “well”. If a tank has high light and some plant growth, but not fully utilized, the aquarist can have some plant growth and it can appear to grow well enough for their taste, but algae will also persist and grow as well. This can lead the aquarist to search for algae killers, “snake oil” remedies and a general focus on the algae’s needs rather than that of the plants. Our goal in planted tanks is generally to grow the macrophytes. So we should fully examine their requirements for health and growth. Nuisance algae can be dealt with any number of ways but unless the plant growth is addressed, the aquarist will have repeated infestations of algae and lack luster plant growth. Many new plant aquarist do not realize how well plants will truly grow when they have their needs fully met and maximized. Some aquarist feel that they need a leg up and should still use algae killers to help them get over this temporary issue. The cause of the problem was plant growth and most algae killers are not plant nutrients and also harm the plants in some way. Various method exist that work well to grow SAM’s in aquariums. Some do not involve CO2 or carbon enrichment while some do. Both methods work for the same reasons, but the growth rate is different, in both cases the plant’s nutrients and assimilation needs are being met for that light intensity and CO2 level. Adding more light drives more CO2 demand in SAM’s. Adding more CO2 drives more NO3 uptake and so on down the list of nutrients. When aquarist change their methods, they need to address these demand changes by the SAM’s. This issue alone has caused great confusion in the hobby of aquatic plants. The “best method” allows the aquarist the rate of growth they desire. This should be considered when approaching a method.

The goal: The goal in this series of chapters is to help the aquarist to grow plants not based on a particular product or system, nor to suggest a single method, but rather general concepts that can be applied to any routine or system to fit their needs and goals for growing plants. Where possible, references to the scientific primary literature are used to show support of the observations in planted impoundments and aquariums. This is seldom done in plant hobby levels books in the past with a notable exception to Diana Walstad’s book, The Ecology of the Planted Aquarium. This book focuses on non-CO2 enrichment methods exclusively and is highly suggested for anyone serious about growing SAM’s. This series will cover non-CO2 methods as well and compare them to CO2 and higher light methods as well as marine SAM growth and methods as well as education of weed related problems. There are many methods that can grow plants but they all have some unifying concepts: good plant growth, dense plant biomass in the aquarium, routine maintenance and some source of nutrients. Each component of growth must be scaled up to meet the needs of the plant’s growth rate. At lower light, there is more flexibility in methods as the rate of nutrient assimilation is slower. Many of the older methods dealt with lower light aquariums and plants. As time has progressed, many aquarist have begun to use higher lighting such as power compact fluorescent and metal halide lighting rather than older T-12 fluorescent lamps. This placed more demand on the CO2 and the nutrients than past methods. A very good thing came of this process, the nutrient needs and uptake rates became much clearer and easier to tease apart. It is the goal of this series to get the aquarist to the point where they can grow the plants well and not deal with algae but also to understand why. Most aquarist seeking a planted tank seek to grow plants well, a few will also aquascape and think of the overall look at first. Once they accomplish the growing part, they can focus their energies on their aquascapes, designs, produce vibrant examples of aquarist plant growth and artistry. This series will focus always be on the plant’s needs rather than the algae. This approach is the long-term solution to the noxious algae problem and works with all methods used today. This concept is unique in the hobby as many methods have never been shown and discussed with this philosophy in mind in one single text. This book is a response to a large lack of literature that has truly attempted to give credence to a unifying methodology for aquatic plant growth principles in aquariums and pulls in elements from Limnology, practical testing, Botany, Phycology, Biology, biogeochemistry, research literature, and other aquarist experiences. Theory and lab studies are not the same as practical applied aquatic plant aquarium, but carefully considering the application of the research as it applies to aquarium plants is very useful.


References:


Alsdorf, D., C. Birkett, T. Dunne, J. Melack, and L. Hess, 2001. Water level changes in a large Amazon lake measured with spaceborne interferometry and altimetry. Geophysical Research Letters 28(14): 2671-2674.


Barr 2004, unpublished data


Barr 2002, Collecting Aquatic Plants in the Santa Ynez River Drainage, California. The Aquatic Gardener - Vol. 15 No. 3 Oct-Nov 2002


Bodkin PC, Spence DHN, Weeks DC (1980) Photoreversible control of heterophylly in Hippuris vulgaris L. New Phytol 84: 533-542


Bowes, G. 2004 course notes University of Florida, Gainesville, FL.


Brenner M. 2003 course note University of Florida, Gainesville, FL.


Campbell, N.A., J. B. Reece, & L.G. Mitchell 1999. Biology. 5th Edition. Addison Wesley Longman Publishers.


Cedergreen, N., T.V. Madsen 2002. Nitrogen uptake by the floating macrophyte Lemna minor. New Phytologist 155:2 p. 285


Cook, C. D. K. 1999. The number and kinds of embryo-bearing plants which have become aquatic: a survey. Persp. Pl. Ecol. Evol. Syst. 2: 79-102.


Dale, H.M. 1981. Hydrostatic pressure as the controlling factor in the depth distribution of Eurasian watermilfoil, Myriophyllum spicatum L. Hydrobiologia 79: 239-244.


Dilcher D. 2002: http://aquat1.ifas.ufl.edu/aq-s02-5.html


Ge Sun, David L. Dilcher, Shaoling Zheng, Zhekun Zhou. 2002. In search of the first flower: a Jurassic Angiosperm, Archaefructus, from northeast China. Science 282: 1692-1695.


Ge Sun, Qiang Ji, D.L. Dilcher, Shaolin Zheng, Kevin C. Nixon, and Xinfu Wang. 2002 Archaefructaceae, a new basal angiosperm family. Science 296: 899-904.


Johnston, C.A. 1991. Sediment and nutrient retention by freshwater wetlands: effects on surface water quality. Critical Reviews in Environ. Control 21(5,6):491-565.


Madsen, T.V. & Cedergreen, N. (2002) Sources of nutrients to rooted submerged macrophytes growing in a nutrient-rich stream. Freshwater Biology, 47: 283-291


References and discussion in G. Evelyn Hutchinson, 1975. A Treatise on Limnology, Vol. III. pp. 408-423.


Stokstad, E. 2002. Fossil plant hints how first flower bloomed. Science 296: 821.


U. Münster,E. Heikkinen,J. Knulst. 1998. Nutrient composition, microbial biomass and activity at the air–water interface of small boreal forest lakes Hydrobiologia 363 (1-3): 261-270, 1997 - 1998


H. Sioli, 1984. The Amazon. Limnology and Landscape Ecology of a Mighty Tropical River and its Basin., editor. Dr. W. Junk Publishers, Dordrecht (ISBN 90-6193-108-8).


Killgore J., B. Payne. 1982. “A Positioning System for Field Studies in Aquatic Habitats; Organization of Aquatic Plant Control Research Program; Principal Investigators and Areas of Responsibilities,” A-82-3


A nice list of further references on depth of vascular plants: http://el.erdc.usace.army.mil/aqua/apis/ecology/html/referen3.html




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1 http://people.delphiforums.com/lordorman/light.htm.2 Aquatic macrophytes are aquatic plants that are large enough to be apparent to the naked eye; in other words, they are larger than most algae

3 For more on uptake dynamics see the reference on Michaelis-Menten uptake modeling: (http://math.fullerton.edu/mathews/n2003/michaelismenten/MichaelisMentenBib/Links/MichaelisMentenBib_lnk_1.html)

 

Re: Aquatic Plant life, unifying principles

Yes, you could infer this from a terrestrial/emergent wetland point of view certainly. the issue there really becomes one of the amount of many nutrients are much higher, wetlands are very productive since they typically contain lots of rich nutrients, some are not as productive and are use to lower nutrient sdlike the end of the Everglades with extremely low PO4 levels, less than 10ppb. They don't have lab test that can verify 10ppb accurately. They are working on it though.

If you add the water column and the substrate together, this is often the case to some degree with at least a few nutrients like Fe and Mn, then it can become more complicated. These are reasons for the problems when setting up experiements and basing them on field studies also.

Adding a tracer ion say, something like P32,N15 etc allows you to follow the path of the nutrients through the ecosystem.

In terrestrial systems and with fungi/bacteria and aerobic soils, things gte used up very fast before they know who and what got to them!
So submersed plants are actually easier in many respects and further ahead.

For the purpose of simplicity, I am talking about the water column in this concept and the article.

Adding the substrate in there only applies when the water column becomes limiting. Then there will be interaction, but the algae are still not limited if the water column becomes limiting for the SAM's(plants).

So the algae are never water column limited essentially.
They might respond and die back some intially, but they will persist.
The plants are slow to respond, but they will stunt of shut down not grow.

Many assume the plants are okay if they are not growing. They don't have to prune as much etc.

Regards,
Tom Barr