Fish stable isotope community structure of a Bahamian coral reef

Abstract

Stable isotopes have provided important insight into the trophic structure and interaction in many ecosystems, but to date have scarcely been applied to the complex food webs of coral reefs. We sampled white muscle tissues from the fish species composing 80% of the biomass in the 4-512 g body mass range at Cape Eleuthera (the Bahamas) in order to examine isotopic niches characterised by δ 13 C and δ 15 N data and explore whether fish body size is a driver of trophic position based on δ 15 N. We found the planktivore isotopic niche was distinct from those of the other trophic guilds suggesting the unique isotopic baseline of pelagic production sources. Other trophic guilds showed some level of overlap among them especially in the δ 13 C value which is attributable to source omnivory. Surprising features of the isotopic niches included the benthivore Halichoeres pictus, herbivores Acanthurus coeruleus and Coryphopterus personatus and omnivore Thalassoma bifasciatum being close to the planktivore guild, while the piscivore Aulostomus maculatus came within the omnivore and herbivore ellipses. These characterisations contradicted the simple trophic categories normally assigned to these species. δ 15 N tended to increase with body mass in most species, and at community level, the linear δ 15 N-log 2 body mass relationship pointing to a mean predator-prey mass ratio of 1047:1 and a relatively long food chain compared with studies in other aquatic systems. This first demonstration of a positive δ 15 N-body mass relationship in a coral reef fish community suggested that the Cape Eleuthera coral reef food web was likely supported by one main pathway and bigger reef fishes tended to feed at higher trophic position. Such finding is similar to other marine ecosystems (e.g. North Sea).

Metal concentrations in coastal sharks from The Bahamas with a focus on the Caribbean Reef shark

“…The developing nation of The Bahamas houses a diversity of productive marine ecosystems such as seagrass beds, oolitic sand banks, open ocean, coral reefs, and mangroves 27 . This high productivity supports biomass of upper trophic level predators, such as sharks, and large teleost fishes 28 , 29 . High shark diversity and abundance in this region stems from over two decades of legislated protection: commercial long-lining was banned in 1993 30 , 31 , and the Bahamian EEZ was declared a ‘shark sanctuary’ in 2011, thereby prohibiting the capture, harvest, or trade of shark products within the exclusive economic zone 31 , 32 .…”

Trophic structure of a nektobenthic community exploited by a multispecific bottom trawling fishery in Northeastern Brazil

“…For some zoobenthivores, isotopic niches often overlap with piscivorous [ 110 ], reflecting the opportunistic behavior of this group in an environment where food sources are highly available. Zoobenthivore fishes had wide feeding preferences [ 65 , 111 ], which would possibly provide large variations of δ 15 N composition [ 112 , 113 ].…”

Multi-trophic markers illuminate the understanding of the functioning of a remote, low coral cover Marquesan coral reef food web

“…In coral reef systems worldwide, the questions of ecosystem functioning, food web structure and function and organic matter sources fueling production are gaining attention 4 , 11 , 13 , 31 . Here we characterize the major energetic pathways that fuel the unusual, low coral cover ecosystem of the Marquesas and assess the extent to which this pelagic production penetrates the coral reef food web.…”