GEOLOGICAL SCIENCES 100
CORAL REEFS MINI-COURSE
KYGER C LOHMANN

 
1. The Reef Environment and Biological Constituents

 
Biological Constituents of the Reef and Marine System

      Biological Components of the Reef System can be characterized the PRODUCERS  and the CONSUMERS.  Primary production of carbohydrates through photosynthesis is dominated by members of the Plant Kingdom.  In this case, carbon dioxide and water are synthesized into organic molecules with energy derived from sunlight.  A byproduct of this process is the production of oxygen. 
      Consumers harvest energy from these carbohydrates through a process called respiration, recombining oxygen with the organic material to produce carbon dioxide and water.  In effect, the process is a reversible reaction even though some energy is lost during the conversion.

      From this simple relation one can broadly define the major groupings of organisms in the Plant and Animal Kingdoms.

 


        Photosynthesis                         ----------------------------->       Respiration  see Figure
CO2+H2O+energy (sunlight) = CH2O (organic material) + O2 => CO2 + H2O
Notes and definitions:
1.  The primary producers of biomass in the ocean are phytoplankton, or "floating plants".  These
        include diatoms which form there skeletons from SiO2 (opaline silica) and coccoliths that
        form there skeletons from CaCO3.
2.   The single celled animals that consume the phytoplankton are called zooplankton.
3.  There are three basic lifestyles associated with marine life:
         Planktonic =  floaters
         Nektonic = swimmers
         Benthonic = bottom dwellers  -- Attached lifestyle is termed "sessile benthonic".
4. In general, the number of individuals (density) as the number of kinds of organisms diversity increases.

 
SOME IMPORTANT PHYLA COMPRISING THE REEF SYSTEM
**Good website:  http://www.ucmp.berkeley.edu/help/index/metazoa.html**
When in this link, select Animals, then the specific Phylum of interest

PHYLUM PORIFERA -- Sponges
     This group generally can be considered as part of the Constructive components of the reef system.  They occur as free standing or as encrusting forms.  Do note, however, that some groups of sponges actively bore into the skeletons of other animals in their search for food.  The result of these boring sponges is quite evident when examining the porous and hole ridden surface of many clam shells.

PHYLUM COELENTERATA -- Corals, hydras, jellyfish (see below for characteristics) http://www.ucmp.berkeley.edu/cnidaria/cnidaria.html
 

PHYLUM ECHINODERMATA -- Starfish, Sea urchins, Sea cucumbers, Brittle Stars 
        Crinoids and Starfish.

PHYLUM MOLLUSCA -- Clams, Snails

Other miscellaneous phyla include:  Annelids (worms), Brachiopods (clam-like), 


 

Notes and definitions: 
1. Phytoplankton are autotrophs and comprise both diatoms and coccoliths. 
2. Primary producers are always more abundant than consumers in the trophic (feeding) relationship.
3.  Eutrophic systems are "nutrient-rich" whereas oligotrophic systems (characteristic of most reefal systems) are "nutrient - poor".

 
Hierarchical Classification of Corals
Kingdom Animal
 Phylum Coelenterata
  Subphylum Cnidaria -- possess cnidoblasts and nematocysts
      Class Scyphozoa (Cambrian to Recent) -- Jellyfish 4-fold endodermal infolds
      Class Hydrozoa (Late Cambrian to Recent)—firecoral, hydras Cylindrical gastral cavity
      Class Anthozoa -- corals
          Subclass Octacorallia – soft corals (Silurian to Rec) 8 fold endodermal infolds
          Subclass Ceriantipatharia "black corals" (Mio-Rec)
          Subclass Zoantharia -- Hexacorals-- "hard or stony" corals 6 fold endodermal infolds
               Order Rugosa extinct (Ordo-Permian)
               Order Tabulata extinct (Ordo-Perm, Trias?)
               Order Scleractinia (Mid-Triassic to Recent) All hard corals living today
                       Family Acropora 
                             Species palmata
 
 

Characteristics of Phylum Coelenterata
Highlighted words are important features that you should note in the attached figure or in figures that are accessed by clicking on the link

 1. Radially symmetrical 
       All structures both within the soft (tissue) and skeletal components of the coral radiate symmetrically around the central axis of the coral which coincides with the opening to the gastrovascular cavity. 
2. Simple tissue structure, " no organs"
3. mouth and gastrovascular cavity (stomach) – no anus
      This is a multi-functional orifice.  The mouth opening, called the oral disc, serves as the opening for the gastrovascular cavity (stomach).  While a primary function of the stomach is for feeding, gonads (sexual cells) are located on the mesenteries (internal folds of the stomach wall). 
4. Possess tentacles 
       The primary function of the tentacles is for feeding and defense.  These structures, in combination with nematocysts (see #5), are can paralyze and immobilize prey.  Crude muscular movement of the tentacles then serves to manipulate the prey into the stomach for digestion.
5. cnidoblasts (stinging cells) with nematocysts (stinging filaments or barbs)
       The presence of cnidoblasts is characteristic of the Subphylum Cnidaria.  These stinging cells serve for feeding and defense of the coral/jellyfish/hydrozoan polyp. When stimulated they discharge a barb-like structure to inject toxins into its prey.


 


 

Basic Structures and Features associated with Corals


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