CHAPTER 6. COMMUNITY COMPONENTS - INVERTEBRATES 



6.1 ECOLOGICAL RELATIONSHIPS bryozoans, and tunicates. The most ob- 

 vious and dominant organisms are usually 



The mangrove ecosystem, with its tree barnacles, crabs, oysters, mussels, iso- 



canopies, masses of aerial roots, muddy pods, polychaetes, gastropods and, tuni- 



substrates, and associated creeks and cates. 

 small embayments, offers many habitat 



opportunities for a wide variety of inver- A striking characteristic of most 



tebrates. While there are few comparisons mangrove swamps is the pattern of horizon- 



of species richness with other types of tal and vertical zonation of invertebrates 



coastal ecosystems, mangrove swamps appear (Figure 9). Characteristic vertical zona- 



to be characterized by moderately high tion patterns are found on the prop roots 



invertebrate species diversity. Abele (Rutzler 1969) and not so obvious horizon- 



(1974) compared H' (Shannon Weaver) diver- tal distributions occur as you move back 



sity of decapod crustaceans between into the center of the swamp (Warner 



various littoral marine communities and 1969). Invertebrate biomass in the red 



found mangrove swamps in an intermediate mangrove zone on the edge of the swamp may 



position with more decapod species than be very high, often in excess of 100 dry 



Sparti na marshes but considerably less g/m of organic matter in many locations 



than were associated with rocky substrate (personal observation). In the center of 



communities. the swamp, particularly where there is 



little flooding, biomass is usually an 



There is little doubt that the maze order of magnitude less; Golley et al. 



of prop roots and muddy substrates under (1962) found an average of 6.4 g/m of 



intertidal mangrove trees provides habitat invertebrates in the center of a Puerto 



for a wide range of invertebrates and Rican mangrove swamp, 

 fishes (Figure 10) (see section 7 for the 



latter). The nursery value of the prop Mangrove-associated invertebrates can 



root complex for juvenile spiny lobsters, be placed in four major categories based 



Panulirus argus , is well established on trophic position: 

 (01 sen et al. 1975; Olsen and Koblic 1975; 



Little 1977; Witham et al. 1968). Ac- (1) direct grazers - limited to 

 cording to these researchers, the phyl- 



losome larvae of spiny lobsters often (a) insects and the mangrove tree 



settle among the prop roots and remain crab, Aratus pisonii , all of which feed on 



there for much of their juvenile lives. leaves in the mangrove canopy and 

 The prop roots provide protection from 



predators and a possible source of food in (b) a group of small invertebrates 



the associated populations of small inver- which graze the prop root and mud algae 



tebrates. To provide the best habitat, a directly; 

 section of the prop roots should extend 



below mean low tide. If conditions are (2) filter feeders - largely sessile 



suitable, the juveniles may remain in prop root invertebrates which filter phy- 



close association with the prop root com- toplankton and detritus from the water; 

 munity for as much as 2 years until they 



reach a carapace length of 60 to 70 mm. (3) deposit feeders - mobile inverte- 

 brates which skim detritus, algae and 



In addition to its value as spiny occasional small animals from the surface 

 lobster habitat, mangrove ecosystems also of the mud and forest floor; 

 harbor the following invertebrates: bar- 

 nacles, sponges, polychaete worms, gastro- (4) carnivores - highly mobile inverte- 

 pod mollusks, pelecypod mollusks, isopods, brates which feed upon the three preceding 

 amphipods, mysids, crabs, caridean shrimp, groups in all locations from the tree 

 penaeid shrimp, harpacticoid copepods, canopy (largely insects) to the mud sur- 

 snapping shrimp, ostracods, coelenterates, face. Food sources in mangrove swamps and 

 nematodes, a wide variety of insects, energy flow are discussed in section 3.6. 



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