Generalist fishes provide an effective measure of the composition of basal carbon source pools fueling benthic communities, by integrating inputs across major consumer groups. In Doubtful Sound, New Zealand, shallow water invertebrate communities differ from those in other areas in Fiordland due to low salinity caused by freshwater output of a hydroelectric power station. To investigate whether the composition of basal carbon sources supporting this benthic community differed from that in unaltered sites, we sampled a generalist wrasse, Notolabrus celidotus, from altered and unaltered habitats throughout Fiordland, and quantified its δ 13 C, δ 15 N, δ 34 S and the abundance of its fatty acids. N. celidotus from the altered sites in Doubtful Sound had significantly lower δ 13 C, δ 15 N and δ 34 S than those collected from similar habitats throughout the Fiordland region, indicating a higher proportion of chemosynthetically fixed organic matter for Doubtful Sound N. celidotus and the invertebrate community upon which they feed. Relatively high abundances of cis-vaccenic acid (18:1ω7c) in fish from Doubtful Sound and δ 13 C values that were ~-33 ‰ for 18:1 isomers confirmed the incorporation of chemosynthetic bacteria, and indicated that the original source of carbon was forest litter. Despite these differences in carbon supply to N. celidotus, analysis of otolith sections revealed no differences in growth rates among sites. The results of this study demonstrate that a shift in invertebrate composition can be indicated by higher order consumers. In Doubtful Sound, decreased abundance of filter-feeding bivalves has reduced the flux of marine derived carbon through the benthic community to higher trophic levels relative to more pristine sites in Fiordland.KEY WORDS: Notolabrus celidotus · Stable isotopes · Fatty acid biomarkers · Compound specific δ 13 C · Food web Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 411: [127][128][129][130][131][132][133][134][135][136] 2010 tures of fish muscle tissue integrate carbon source use by a community over months to years (e.g. Guelinckx et al. 2007, Suring & Wing 2009). We designed a sampling scheme to test whether anthropogenic modifications to the salinity environment in a New Zealand fjord had altered carbon routing in the benthic community. While the marine and terrestrial environments of the 15 fjords in southern New Zealand, collectively known as Fiordland, remain relatively pristine, Doubtful Sound receives an average of 450 m 3 s -1 of freshwater outflow from the Manapouri Hydroelectric Power Station. The resulting persistent shallow low salinity layer (Gibbs et al. 2000) has led to a reduction in the abundance of filter-feeding invertebrates including infaunal clams (Tallis et al. 2004, Rutger & Wing 2006, McLeod & Wing 2008 and mussels (Jack et al. 2009). The decreased biomass of filterfeeding bivalves could dramatically reduce the capture of particulate carbon (from both phytoplankton and eroded macroalg...

It is increasingly accepted that coastal habitats such as inshore coral reefs do not function in isolation but rather as part of a larger habitat network. In the Caribbean, trophic subsidies from habitats adjacent to coral reefs support the diet of reef fishes, but it is not known whether similar trophic links occur on reefs in the Indo-Pacific. Here, we test whether reef fishes in inshore coral, mangrove, and seagrass habitats are supported by trophic links. We used carbon stable isotopes and mathematical mixing models to determine the minimum proportion of resources from mangrove or seagrass habitats in the diet of five fish species from coral reefs at varying distances (0-2,200 m) from these habitats in Moreton Bay, Queensland, eastern Australia. Of the fish species that are more abundant on reefs near to mangroves, Lutjanus russelli and Acanthopagrus australis showed no minimum use of diet sources from mangrove habitat. Siganus fuscescens utilized a minimum of 25-44 % mangrove sources and this contribution increased with the proximity of reefs to mangroves (R 2 = 0.91). Seagrass or reef flat sources contributed a minimum of 14-78 % to the diet of Diagramma labiosum, a species found in higher abundance on reefs near seagrass beds, but variation in diet among reefs was unrelated to seascape structure. Seagrass or reef flat sources also contributed a minimum of 8-55 % to a fish species found only on reefs (Pseudolabrus guentheri), indicating that detrital subsidies from these habitats may subsidize fish diet on reefs. These results suggest that carbon sources from multiple habitats contribute to the functioning of inshore coral reef ecosystems and that trophic connectivity between reefs and mangroves may enhance production of a functionally important herbivore.

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Identifying pathways that animals use to move among ecosystems has become a focus for improving conservation planning. The function of habitat corridors in facilitating animal movement among terrestrial ecosystems is well established. By contrast, the role of habitat corridors for the movement of marine animals is poorly understood. We used underwater video cameras to evaluate the effects of seagrass corridors and water depth on fish abundance, and the arrival of prey and predatory species on intertidal coral reef flats in eastern Australia. Cameras were placed in intertidal seagrass and unvegetated habitats during incoming tides and recorded fish that moved across these habitats. We found some evidence that fish were more abundant over intertidal seagrass, particularly garfish Hyporhamphus regularis ardelio, striped barracuda Sphyraena obtusata and striped grunter Pelates sexlineatus, but most species did not appear to use the intertidal seagrass as a corridor. Prey fish were generally more abundant at shallower water depths, whereas predators were more common in deeper water, but many species were present over intertidal flats throughout the incoming tide. Our findings show that the movement of fishes across intertidal flats is dynamic, and depends on the species of interest, the composition of intertidal seascapes and tidal condition. Understanding how biotic and abiotic factors interact to influence fish movement and shape patterns in habitat use is a critical challenge for conservation planning in shallow coral reef seascapes.