...and a cast of thousands!

An excerpt from a movie poster? Could be, but no. I am talking about the multitude of micro-organisms (plant and animal) that call your pond home. I briefly discussed those that live on the bottom or Benthic layer in a previous post. In this post I want to explore those that live in the water column. They are commonly referred to as Plankton.

Plankton is divided into two (2) groups-

   -Phytoplankton which is microscopic plants (algae) and some species of bacteria. These are the primary producers in the aquatic food chain.

   -Zooplankton consists predominately of crustaceans and rotifers. They are usually larger than phytoplankton. They are predators and feed on phytoplankton and other zooplankton.

As an example of the sheer magnitude of their numbers, in a fish culture pond it is not unusual for plankton (dry weight) to account for up to 50% of the total biomass (dry weight) of the pond (this includes the fish). That is a lot of little critters! But very important little critters! They comprise the bulk of any aquatic food chain and web. A pond’s biological balance would collapse without their existence in such great numbers

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Your Koi and/or Goldfish may be the Stars in your perception but, in biological terms, they are only bit players. They, because they are the top consumer in the food chain, are dispensable as far as maintaining biological balance. The lower an organism exists in the food chain, the more indispensable they become. This truly makes the existence of algae, for instance, more important than the fish. This is not to say that you can’t have too much algae. An overgrowth of algae can be problematic for the balance in a pond as can too many fish.

The USDA recently did away with the Food Pyramid in favor of a dinner plate diagram as a nutritional guide. I prefer the pyramid for it emphasizes the real importance of the food groups. Those most important and also in greatest numbers are at the bottom or base of the pyramid. The same applies to the food chain in a pond. Those organisms of greatest number and importance are at the bottom.  Phyto-plankton.are part of this pyramid base.. Zooplankton are just one level higher in the pyramid.

All plankton serve as nutritional sources for organisms higher in the food chain. Insects, amphibians, annelids and some fish specie look to plankton as a food source.

Just observe all of the activity around your pond. It can be quite a pageant. A pageant that requires........... ‘a cast of thousands’.

Algae - The Propitious PITA

Listen in on most any conversation about ponds and you will eventually hear the word Algae mentioned, many times along with some unpleasant descriptive adjectives. In the majority of cases, it is the ‘Green Algae’ that is the subject of the verbal derision.

It is true that out-of-control algae can turn an otherwise beautiful Water Feature into a most disgusting eyesore. It is wrong, however, to put any blame on this simple organism. “Don’t shoot the messenger”.  Algae are not the problem. It has been explained in countless means of communication, for countless times and for countless years that….excess algae is a direct result of an excess nutrient level in the pond water. So, if your pond has an abundance of algae, it is your fault because: (a)You have too many fish; (b) You overfeed your fish; (c) You do not have a sufficient size aquatic plant population; (d) You allow leaves, twigs and other organic debris to accumulate in you pond; (e) All of the above.

Algae are, by their nature, quite beneficial. Nearly all algae are photosynthetic (the ability to produce Oxygen), so much so that the total amount of Oxygen produced by all algae EXCEEDS the total amount produced by the entire plant kingdom. That’s impressive!

Algae are an extremely important source of nutrition for most aquatic organisms and are an integral part of the foundation of the overall food web. Extremely high in nutritional value, several species of Algae are used for human consumption, from wrapping sushi (Nori-Red Algae) to nutritional supplements such as Chlorella and Spirulina (Green Algae).

There are over 300,000 identified species of algae (no one knows the exact number) and around 6,000-7,000 species of green algae (again no one know for sure) and range in size from the single cell microscopic to the multi-cell giant sea kelp

Algae have existed in vast numbers for millions of years. The sparkling white sand beaches of the Caribbean and many other areas in the world are largely the sun-bleached and eroded calcium-carbonate remains of green algae.

They are an important part of the Nitrogen cycle (the use of Nitrates as an energy source) and the Carbon cycle. Like Oxygen, the total amount of Carbon contained in all algae exceeds the total amount contained in the entire plant kingdom.

In conclusion, the next time you think of hurling epithets at the green invasion of your pond, just remember all of the beneficial aspects of algae and, more to the point, remember that it is likely your fault. Like any other pesky organism…quit feeding it and it will go away.

Archaea: The not-so-new kids on the block

The oxidation of Ammonia was for decades believed to be performed solely by certain autotrophic bacteria (i.e. Nitrosomona)  Later it was discovered that this oxidation process was also performed by certain Heterotrophic bacteria under certain conditions that were completely void of any organic carbon source or oxygen.

With the advent of gene sequencing, it was discovered in 1977 that what was thought to be a type of bacteria was actually not a bacteria at all, but an entirely different and new domain. This group of microorganisms was given the name “Archaea”.

Originally thought to be exclusively extremeophiles that lived in environments such as hot springs and very acid and saline conditions, it was recently (2006) discovered and subsequently verified (2008) that Archaea are ubiquitous and exist in all environments and more importantly play a very large role in the oxidation of Ammonia. Unlike nitrifying bacteria, nitrifying Archaea are suspected to be adaptable to a wider range of temperatures. Evidence of their existence has been found in the very cold waters of Antarctica.

Unfortunately, at the present time, Archaea are very difficult, if not impossible, to reproduce under laboratory conditions, so current knowledge is limited.

No nitrite oxidizing Archaea have been detected to date, but, given the relative infancy and current limits of research, this does not mean that they don’t exist.

The results of future research could have a major impact on how we view the basic biological processes of our ponds. For example, it has already been shown that Archaea tend to colonize the rhizosphere (root zone) of aquatic plants. This fact alone increases the importance of aquatic plantings in maintaining water quality. Archaea’s wider tolerance of extreme temperatures could possibly shed light on why some Northern ponds endure winter stresses better than others.

Much still needs to be learned about this newly named, but very old, microorganism.

The Benthos

"The length of food chains is a crucial determinate of the functioning of ecosystems," says Alan Tessier, program director in the National Science Foundation (NSF)'s Division of Environmental Biology.

Roughly translated, diversity in an eco-system is of prime importance. This diversity is not limited to the number of levels in a food chain, but the diversity within each level provides a key element of stability to the entire food chain. The lower the level of the food chain, the more important and crucial this diversity becomes.

Biofilm, as indicated in the previous post, forms the true foundation upon which an aquatic food chain is established. Also of extreme importance is what is called the Benthic layer or Benthic zone.

The Benthic zone is the ecological region at the lowest level of a body of water including the sediment surface and some sub-surface layers. This region extends from water’s edge to water’s edge and encompasses the shallow (littoral) regions as well as the deepest (i.e. the profundal region that exists is lakes).Organisms living in this zone are called Benthos. They generally live in close relationship with the substrate bottom; many such organisms are permanently attached to the bottom. The superficial layer of the soil lining the given body of water, the benthic boundary layer or BBL, is an integral part of the benthic zone, as it influences greatly the biological activity which takes place there.

Benthos, in fresh water biology, refers to organisms at the bottom of bodies of water, such as lakes, ponds, rivers, and streams. The population make up of these communities is influenced not only by type of body of water, but also by the depth of the water plus nutrient availability and, of course, pH and temperature.

There are two types of Benthic organisms:

          Epifauna- live on the surface of the bottom

            Infauna- burrow into the sediment on the bottom

Of the two, Epifauna is the most prevalent form found in an eco-system pond, although some Infauna may exist depending on depth of bottom gravel and the amount of sedimentation.

They are also classified as to size:

Microbenthos (<100mm) includes bacteria & protests

Meiobenthos (100-500mm) includes small metazoan (multicellular animals) and larger protists (single cell organisms).

Macrobenthos (>500mm) includes larger metazoa and Megabenthos

          Megabenthos (very large.)  crustaceans, mollusks, etc.

By what they eat:

Herbivores- feeds on plant material

Carnivores/predators- feeds on other benthic organisms

Detritivores- feeds on dead plant and animal material

And how they eat:

Suspension feeders- eats using a mucus-covered appendage that catches particles in water column

Filter feeders- strain particles from the water column

Deposit feeders- ingest sediment and removing the nutrients

In our next post, we will delve deeper into the roles that each individual type plays in the complex world of an aquatic eco-system. It will be the beginning of an interesting journey into a world of such immense activity that, by comparison, the activity level of your fish is like watching paint dry.