Stable isotope analysis of production and trophic relationships in a tropical marine hard-bottom community.
Seagrasses produce much of the organic carbon in the shallow waters of the Caribbean and it has long been assumed that a substantial portion of this carbon is exported to nearby habitats, contributing substantially to their food webs. In the shallow coastal waters of the Florida Keys (USA), seagrass intersperses with hard-bottom habitat where bushy, red macroalgae are the most prominent primary producers. However, the relative importance of seagrass-derived carbon versus autochthonous algal production or phytoplankton in supporting higher trophic levels within hard-bottom communities has never been investigated. We compared the carbon and nitrogen isotopic values of potential primary producers and representative higher trophic level taxa from hard-bottom sites on the bay-side and ocean-side of the Florida Keys. We also included in our study a set of bay-side sites that experienced significant ecological disturbances over the past decade (e.g., cyanobacteria blooms, seagrass die-off, and sponge die-offs) that may have altered trophic relationships in those regions. We did not detect any differences among regions in the trophic status of hard-bottom taxa that might be associated with ecosystem disturbance. However, our results suggest that autochthonous production of algal detritus is an important source of secondary production in these hard-bottom communities, with seagrass and phytoplankton contributing smaller fractions.
Department of Biological Sciences, Old Dominion University, Norfolk, VA 23529-0266, USA. dbehringer@comcast.net
Donald C
DC
Behringer
Mark J
MJ
Butler
D000818:Animals; D002247:Carbon Isotopes; D017691:Caribbean Region; D017753:Ecosystem; D005431:Florida; D031321:Hydrocharitaceae / Q000502:physiology*; D044722:Laurencia / Q000502:physiology*; D008121:Nephropidae / Q000502:physiology; D009587:Nitrogen Isotopes; D011161:Porifera / Q000502:physiology; D012616:Sea Cucumbers / Q000502:physiology; D012908:Snails / Q000502:physiology
D002247:Carbon Isotopes; D009587:Nitrogen Isotopes