Marine Science Faculty Publications

A Comparison of Phytal Substrate Preferences of Archaias Angulatus and Sorites Orbiculus in Mixed Macroalgal-Seagrass Beds in Florida Bay

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Habitat preferences of epiphytic foraminifers, particularly Archaias angulatus and Sorites orbiculus, were studied in a mixed macroalgalseagrass bed in Florida Bay near Long Key. Ten common plant species with different growth forms were sampled. On all ten macrophytal substrates, foraminifers belonging to the Order Miliolida made up at least 75% of the foraminiferal assemblage, with smaller miliolids accounting for between 30 and 60% of the assemblages. Archaias angulatus composed more than 30% of the assemblage on seven of the ten substrates. The smaller miliolids and A. angulatus were most abundant on entangled or epiphytized macroalgae, indicating that such substrate provides optimal three-dimensional habitats that are sheltered from water motion, yet provide abundant food and light resources.

Sorites orbiculus was present on all macrophytal substrates, but was responsible for more than 5% of the assemblage on only three, notably both species of seagrass examined and on the rhodophyte Laurencia intricata. S. orbiculus appears to prefer flat, bare surfaces of phytal substrates such as blades of the seagrass Thalassia testudinum, to which it may semi-permanently adhere.

Habitat preferences of A. angulatus and S. orbiculus provide insight into the documented decline of symbiont-bearing Soritidae relative to smaller Miliolidae in Florida Keys sediments. Anthropogenic nutrification of nearshore waters is promoting epiphytic algal growth on seagrasses and macroalgae. Epiphytic growth may deter attachment of S. orbiculus juveniles or smother individuals once attached. A. angulatus populations, which might otherwise benefit from the epiphytic growth, are intolerant of episodic anoxia that results when overproduction of organic matter increases benthic oxygen demand.

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Journal of Foraminiferal Research, v. 29, issue 2, p. 143-151