Nutrition
 
  Nutrition
 
 
Detritivory hot buttons for nutrition part of BCCR hot button for Corals: a case study part of BCCR hot button for primary productivity part of BCCR hot button for herbivory part of BCCR hot button for carnivory part of BCCR hot button for detritivory/bacterivory part of BCCR

This part of nutrition deals with detritivory/bacterivory, that is, with coral-reef organisms that eat detritus, or bacteria, or both. Other topics relating to nutrition of coral reefs can be accessed via the icons.

NOTE detritus is dead organic matter colonised by a variety of microorganisms. It sifts to the sea bottom and accumulates in crevices and within algal matrices. Microorganisms associated with detritus include bacteria, fungi, protists, and actinomycetes

 
 

Detritivory

  This section deals with detritivory, while BACTERIVORY is found in its own section.
 
 
seahorse dive leader for Biology of Caribbean Coral Reefs website photograph of a parrotfish defecating, taken from a video

"Wow! That's quite a dump! As we follow the lovely rain of parrotfish feces we should think about how much organic detritus is sifting down and accumulating in cracks and crevices, and in the surrounding sand. This detritus is an important food source for many animals." - Litle Cayman 2001

NOTE stoplight parrotfish Sparisoma viride

 

 
  pie diagram illustrating the composition of detritus in the Great Barrier Reef
Studies on the Great Barrier Reef show that detritus may comprise up to 80% of the filamentous algae assemblage on the reef, and is often more nutritious to the fishes than the algae themselves. The "pie" diagram shows a breakdown of the organisms contributing to the detritus in summer after their deaths. Wilson et al. 2003 Oceanogr Mar Biol: Ann Rev 41: 279.
 
 
seahorse dive leader for Biology of Caribbean Coral Reefs website photograph of a porcupinefish taken from a video

"This porcupinefish is swimming through a snowstorm of particulates. It's made up of fine sediments, bits of organic material, feces, plankton, and other junk. It doesn't make for a good dive, but it's good food source for many of the invertebrates, and even some fishes." - Cayman Brac 2001

NOTE Diodon histrix

 

 
 

photograph of redtail parrotfish Sparisoma chrysopterum defecating
Fishes that eat from the sea bottom, such as parrtofishes, surgeonfishes, gobies, and blennies, consume large quantities of detritus. Because they are large, eat copious amounts of turf and filamentous algae including calcareous matter, and defecate considerable volumes, parrotfishes add significantly to the detritus and mineral contents of sands around reefs.

 

 

 

The culprit that just defecated is the
redtail parrotfish Sparisoma chrysopterum
presently at the 8 o'clock position. The other "plumes"
are from 2 SCUBA-divers located in the background 0.15X

 

photograph of finger coral Porites poritesCorals produce mucous sheets not just for suspension-feeding, but also periodically during lunar cycles and in times of stress. Studies in Panama show that mucus produced by finger corals Porites porites in response to experimental conditons of low salinity and high load of sediment can contribute significant nutritive pulses to the reef's food-webs. Coffroth 1989 Dissert Abstr Intern Part B: Sci & Engineer 50: 162.

 

 

 

 

Finger coral Porites porites 0.5X

  photograph of a spaghetti worm Eupolymnia crassicornis feedingCiliated troughs in the tentacles of spaghetti worms Eupolymnia crassicornis transport sediment and organic particles to the mouths of the worms, whose bodies reside in protetive burrows. The tentacles seem to have no defenses and are vulnerable to predatory attacks by carnivorous fishes and invertebrates.
 


Sea cucumbers, heart urchins, and certain sea stars are major bioturbators of surface sediments through their practically non-stop ingestion and defecation of detritus-containing sediments. Scheibling 1982 Bull Mar Sci 32: 624.

NOTE lit. "biological disturbance", as opposed to physical disturbance as, for example, from wavesphoto composite of various detritus-eaters on Caribbean coral reefs

 

photograph of 3-rowed sea cucumber Isostichopus badionotusIn Jamaica, a three-rowed sea cucumber Isostichopus badionotusactively feeds from late afternoon through to midnight, reduces its rate during morning hours, and rests through midday.  Distance traveled over a 10d period is only about 2m.  Measurements of feeding and defecation rates indicate that duration of gut passage is about 5h.  Hammond 1982 Bull Mar Sci 32 (2): 549.

 

 

 

Three-rowed sea cucumber Isostichopus
badionotus
complete with fecal pile 1.3X

 

photograph of black durgeonSome species of wrasses, damselfishes, triggerfishes, and surgeonfishes are coprophagous, but are actually quite selective in terms of what they eat. Feces from zooplanktivorous and other carnivorous fishes are preferred over feces from herbivores such as parrotfishes and certain triggerfishes.

NOTE lit. "feces eat"

 

 

 

Black durgon triggerfishes Melichthys niger are
omnivorous, eating algae, small invertebrates,
detritus, and sometimes small fishes 0.4X

 
 

Another characteristic of coprophagous fishes is that while they may readily eat the feces of other species of fishes, they are less willing to eat the feces of conspecifics. Why do you think this is? Consider the possible answers below, then CLICK HERE for explanations.

The taste of conspecific feces is less good.

There is less nutrition in conspecific feces.

Transfer of parasites is minimised.

Conspecific feces look unappetising.

NOTE individuals of the same species

 
 
seahorse dive leader for Biology of Caribbean Coral Reefs website photograph of a sea cucumber Isostichopus badionotus with feces taken from a video

"Sea cucumbers are really just lumps, aren't they? This one looks to be resting after processing all of its sandy food into fecal matter." - Bonaire 2005

NOTE three-rowed Isostichopus badionotus

 
 

photograph of three-rowed sea cucumber Isostichopus badionotus
Feces of sea cucumbers are often richer in organic content than the surrounding sediments, and may be re-eaten preferentially by the same, or other, sea cucumbers.

 

 

 

 

Sea cucumber Isostichopus
badionotus
with feces 1X

 

 

 
  Father knows best:
 
cartoon 1 in a series of 6 showing sea cucumbers discussing the nutritional aspects of feces cartoon 2 in a series of 6 showing sea cucumbers discussing the nutritional aspects of feces
cartoon 3 in a series of 6 showing sea cucumbers discussing the nutritional aspects of feces cartoon 4 in a series of 6 showing sea cucumbers discussing the nutritional aspects of feces
cartoon 5 in a series of 6 showing sea cucumbers discussing the nutritional aspects of feces cartoon 6 in a series of 6 showing sea cucumbers discussing the nutritional aspects of feces
 
 
seahorse dive leader for Biology of Caribbean Coral Reefs website photograph of a lugworm burrow taken from a video

"Well, what's this? Someone built a sand pile. Actually, it's the fecal deposit of a worm, probably a lugworm. The worm's burrow is U-shaped with a big mound in the back. The front end...well, it's usually a shallow depression...perhaps this small hole on the right." - Grand Cayman 2001, Bonaire 2003

NOTE possibly southern lugworm Arenicola cristata

 
  Burrowing shrimps, worms, heart urchins, and sediment-snuffling fishes like goatfishes are major bioturbators of sediments. A large sandy mound often indicates the presence of a lugworm. These small segmented worms live in U-shaped burrows and spend their time eating sand and detritus, extracting the usable organic matter from it, and then defecating the remainder as a sandy cone.

photo composite of lugworm Arenicola cristata burrows
 

diagram of lugworm burrow Arenicola cristataLugworms Arenicola cristata live in U-shaped burrows. As shown in the drawing, the worms feed on nutrient-containing sand at the front end, creating a depression, and defecate at the rear end, creating a volcano-shaped mound.

 

 

 

Movement of the worm at the front end
during feeding creates a "puddling" effect,
thus aiding in ingestion of the sand and
causing the sand to subside as a depression

 
 
seahorse dive leader for Biology of Caribbean Coral Reefs website photograph of feeding goatfishes taken from a video

"Feeding goatfishes are like little whirlwinds. They're searching for worms, crustaceans, and other small invertebrates which they sense with their probing barbels. Anybody see them eat? Maybe it happens really quickly." - Bonaire 2003, Turneffe Island 2000. Second part of video courtesy Andy Stockbridge, Belize.

NOTE spotted goatfish Pseudupeneus maculatus

 
 

photograph of midnight parrotfish
Goatfishes, parrotfishes, and other bottom-feeding species must ingest considerable quantities of detritus as they forage for their regular photograph of goatfishesfoods.

 

Blue parrot-
fish Scarus
coeruleus

0.15X

 

 

Yellow goatfishes Mulloidichthys martinicus 0.2X

  photo composite of detritivorous echinoids Mellita sexiesperforata and Meoma ventricosaSand dollars and heart urchins burrow in the sediments looking for vegetative detritus to eat. Studies on sand dollars Clypeaster rosaceus show that an individual can annually convert about 5kg of coarse green-alga Halimeda detritus to much finer calcareous bits. These bits eventually drift inshore where they contribute to the formation of white-sand beaches. Kampfer 1995 p. 309 In, Biology and ecology of shallow coastal waters.
 

graph showing relationship of densities of co-occurring curshion stars and heart urchinsStudies in St. Croix show that cushion sea stars Oreaster reticulatus and heart urchins Meoma ventricosa inhabit the same areas of fine-grained sands and may compete for space. Although too few observations have been made to be confident, there is suggestion that where sea-star numbers are high, heart-urchin numbers are low, and vice versa. Both species ingest organic-rich detrital surface layers of the sediments. Scheibling 1982 Bull Mar Sci 32: 624.

 

 

 

The orange dot on the left indicates that where
cushion stars are abundant, heart urchins are not,
while the right orange dot indicates the reverse

 
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