[DATE OF SAMPLING UNKNOWN OR NOT APPLICABLE.] Seagrasses are important 
sources of organic matter for food webs in many coastal ecosystems. However, stable 
isotopic investigations conducted over the past decade have shown that phytoplankton 
and epiphytic algae can have an equal or greater nutritional importance than seagrasses 
for consumers in many seagrass meadows. Nutrient availability may govern the 
relative importance of algal and seagrass foods, with the result that eutrophic waters 
favor food webs based on algae, but detrital seagrasses are more important in 
oligotrophic waters. This review summarizes many previously unpublished stable 
isotopic studies of seagrass ecosystems. Assumptions commonly made in interpretation 
of isotopic values are evaluated, and four main conclusions are drawn: (1) Within one 
species, seagrass 5 13 C varies significantly between individuals, populations, and 
seasons; (2) Carbon isotopic changes during seagrass decomposition are small, 
approximately 1 °/oo; (3) Little fractionation of carbon isotopes occurs during food web 
processing of live or detrital seagrasses; and (4) Benthic algae can have carbon 
isotopic values close to those of seagrasses, consequently 5 13 C measurements are not 
always unambiguous tracers of seagrass carbon. Latter sections show that stable 
hydrogen, nitrogen, and sulfur isotopic measurements can be used in conjunction with 
carbon isotopic measurements to show consumer dependence on seagrass organic 
matter, and that isotopic measurements can be useful for mapping highly localized food 
webs. 
1987 0 
Gilmore, R. G. (1987) Subtropical-tropical seagrass communities of the southeastern United 
States: fishes and fish communities. Fla. Mar. Res. PubL 42:117-137. 
[DATE OF SAMPLING UNKNOWN OR NOT APPLICABLE.] Paper reviews the community 
relationships of fishes associated with seagrasses and is based on studies done in the 
southeastern US including Florida Bay. Prior to 1960, most ichthyofaunal research was 
necessarily taxonomic and zoogeographic, with little attention given to habitat or 
substrate associations. With the advent of long-term faunal studies within specific 
habitats and analyses of physical and biological parameters affecting fish distribution, 
seagrasses were recognized as a distinct fish habitat. Regional ichthyological research 
in seagrass ecosystems has been conducted primarily in the northeastern Gulf of 
Mexico and principally in the Apalachee Bay region. Consequently, regional tropical and 
subtropical seagrass ichthyofaunas have received little study. The available literature 
on tropical and subtropical fish-seagrass associations is not adequate for quantitative 
assessment, but it reveals zoogeographic distribution patterns and enables some 
prediction of species occurrence in seagrass ecosystems. Fishery species have 
received the most intense study, particularly certain sciaenids and sparids, such as the 
spotted seatrout, Cynoscion nebulosus, and the pinfish, Lagodon rhomboides. However, 
many species need further treatment as their microhabitat associations, general 
biology, behavior, and mortality rates during juvenile developmental periods have not 
received adequate attention. Typically diminutive and numerically abundant nonfishery 
species, such as gobiids and syngnathids, make up the majority of resident species 
within the seagrass ecosystem. Their biology and impact on this ecosystem await 
further study. The inter- and intraspecific interactions of various seagrass residents 
and systematically occurring transients need to be researched, particularly with 
regard to predatory relationships, territorial behavior, invertebrate population 
dynamics and distribution, seagrass morphology, and meadow homogeneity. The 
hierarchical predatory relationships between various fish species guilds throughout the 
total ecosystem, particularly with regard to tertiary and upper level predators, have 
been virtually ignored. 
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