FeedingGuilds
Feeding Guilds and Trophic Levels
Feeding Guilds
As Merriam-Webster dictionary defines it, a feeding guild is “a group of organisms that use the same ecological resource in a similar way”. In simpler terms, feeding guilds can be described as groups of living things that get their energy necessary to survive from the same source. Feeding guilds do not have to be made up of the same or similar species; they can be completely unrelated, only alike in the fact that they acquire resources from their surroundings in similar ways. Because members of a guild use the same resources, competition is common within that guild. A feeding guild is composed of three major categories: autotrophs, heterotrophs, and detritivores.
Autotrophs
Autotrophs are "self-nourishing organisms capable of absorbing solar energy and photosynthetically building high-energy organic substances" [1] Because these organisms need light to survive, they are most commonly found within the top 70 meters of water in marine environments. Since most coral reefs reside in shallower waters, they provide a great environment for autotrophs. Two examples of autotrophs in coral reef ecosystems are seaweed and zooxanthellae, a type of algae that makes up part of the coral and gives it color.
Heterotrophs
Heterotrophs are consumers, they obtain their energy necessary to survive from other organisms. Heterotrophs can be broken down into seven different subcategories: herbivores, carnivores, omnivores, filter feeders, planktivores, oppurtunistic feeders, and parasites.
Herbivores
Herbivores feed only upon autotrophs. There is a large guild of herbivores in coral reef environments. Two examples are the Green Sea Turtle, which eats sea grass, and a sea urchin, which eats algae.
Carnivores
Carnivores feed only upon other animals. In coral reefs, they range from top predators such as barracudas and eels to smaller predators such as lobsters.
Omnivores
Omnivores consume both autotrophs and other heterotrophs.An example of an omnivore in coral reefs are anglefish which feed algae, smaller fish, and shrimp.
Filter/Suspension feeders
Filter/suspension feeders primarily consume organic material (pseudo-plankton) floating in the water column.[2] Suspension feeders capture particles of food from the water using tentacles while filter feeders use a filtration system to filter out dissolved particles after pumping in water. Zooplankton and sponges are good examples of these in coral reef environments.
Planktivores
Planktivores eat the small organisms (collectively known as plankton) that drift in the water. They can herbivorous and consume primarily phytoplankton, or they can be zooplanktivores that consume suspended animals. [2] The whale shark, which feeds primarily on plankton, is an example of planktonivores in coral reef ecosystems.
Opportunistic feeders
This group targets prey based on what is available at the time. Scavengers and cannibals, such as some species of crabs, are included in this group. [2]
Parasites
Parasites "live on or in another organism", taking their nutrition from the host organism while giving nothing in return. [2] A common example seen on coral reef fish, is the cymothoid isopod.
Decomposers
Decomposers obtain their energy from dead and decomposing matter. They are extremely important to coral reef ecosystems because the break down the dead waste, convert it to energy they can use, and then return important materials back into the environment. For coral reefs, the main decomposers are bacteria. Bacteria play an essential role in the nitrogen cycle to provide the environment with necessary nutrients, such as nitrate, while also keeping toxic waste levels low.
Trophic Levels
For coral reefs:
Why It's Important: Imbalances in the System
“Coral reefs are complex ecosystems that require a balanced trophic structure to function properly and efficiently. Imbalances can occur in this intricate trophic cascade from the top down or the bottom up.”
An example of bottom up effect imbalances that illustrates why feeding guilds and trophic levels are important to the coral reef ecosystem comes from an incident in the Great Barrier Reefs. Coral in the Great Barrier Reefs is now being threatened not only by coral bleaching but an even bigger predator, the Crown of thorns starfish. Agricultural runoff containing fertilizer has caused an excess of phytoplankton to be present in the waters around the reefs. The Crown of thorn starfish larvae feed on this phytoplankton and thus caused a population explosion in the area. The problem is that the crown of thorn starfish feeds on coral and can eat up to 10 square meters of tissue a year. This bottom up effect has taken its toll on the reefs surrounding Australia, with 42% of coral reef decline in the area due to the crown of thorns invasion.
By: Kathryn Bennett and Richa Solanki
References
http://www.coralscience.org/main/articles/climate-a-ecology-16/coral-reef-ecology
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0063797
http://www.coral.org/resources/about_coral_reefs/threats_to_coral_reefs
"A trophic model of the coral reef ecosystem of La Parguera,Puerto Rico: synthesizing fisheries and ecological data"
"Comparisons of Coral Reef Ecosystems along a Fishing Pressure Gradient"
Feeding Guilds
The "[relationship] between different organisms can be described by their trophic associations." On the most fundamental level, trophic associations describe "what an organism eats and what eats it."[1] All organisms can be divided into three different categories: producers, consumers, and decomposers. [1][2]
Autotrophs
Autotrophs are primary producers, "self-nourishing organisms capable of absorbing solar energy and photosynthetically building high-energy organic substances" [1] A classic example of an autotroph on the reef are zooxanthellae.
Heterotrophs
Heterotrophs are consumers that feed upon other organisms.
Herbivores
Herbivores feed primarily upon autotrophs.
Carnivores
Carnivores feed upon other animals. On the reef, carnivores can feed upon other fish, coral, other creatures like mollusks, etc.
Omnivores
Omnivores consume both autotrophs and other heterotrophs.
Filter/Suspension feeders
Filter feeders primarily consume organic material (pseudo-plankton) floating in the water column.[2] Organic matter can take the form of particulate organic matter (POM), suspended organic matter (SOM), or dissolved organic matter (DOM). [1]
Planktivores
Planktivores eat the small organisms (collectively known as plankton) that drift in the water column. They can herbivorous and consume primarily phytoplankton, or they can be zooplanktivores that consume suspended animals. [2] Phytoplankton are single-celled microscopic organisms and "account for the major share of primary productivity in the marine environment." Cyanobacteria, chrysophyta, and dinophyta form the three major groups of phytoplankton. [1]
Opportunistic feeders
This group targets prey based on what is available at the time. Scavengers and cannibals are included in this group. [2]
Parasites
Parasites "live on or in another organism", taking their nutrition from the host organism while giving nothing in return. [2]
Detritivores
Detritovores are decomposers like bacteria that feed upon the waste products and dead remains of other organisms. [1]
References
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Sumich, James L. An Introduction to the Biology of Marine Life, Seventh Edition. WCB/McGraw Hill. 1999.
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 Tackett, Denise and Larry. Reef Life: Natural History and Behaviors of Marine Fishes and Invertebrates. Neptune City, NJ: T.F.H Publications, 2002, p. 117-118. Print.