Freezing and chemical preservatives alter the stable isotope values of carbon and nitrogen of the Asiatic clam (Corbicula fluminea)

We tested the impacts of most common sample preservation methods used for aquatic sample materials on the stable isotope ratios of carbon and nitrogen in clams, a typical baseline indicator organism for many aquatic food web studies utilising stable isotope analysis (SIA). In addition to common chemical preservatives ethanol and formalin, we also assessed the potential impacts of freezing on δ¹³C and δ¹⁵N values and compared the preserved samples against freshly dried and analysed samples. All preservation methods, including freezing, had significant impacts on δ¹³C and δ¹⁵N values and the effects in general were greater on the carbon isotope values (1.3-2.2% difference) than on the nitrogen isotope values (0.9-1.0% difference). However, the impacts produced by the preservation were rather consistent within each method during the whole 1 year experiment allowing these to be accounted for, if clams are intended for use in retrospective stable isotope studies

Turnover rates of nitrogen stable isotopes in the salt marsh mummichog, Fundulus heteroclitus, following a laboratory diet switch

Author Posting. © The Authors, 2005. This is the author's version of the work. It is posted here by permission of Springer-Verlag GmbH for personal use, not for redistribution. The definitive version was published in Oecologia 147 (2006): 391-395, doi:10.1007/s00442-005-0277-z.Nitrogen stable isotopes are frequently used in ecological studies to estimate trophic position and determine movement patterns. Knowledge of tissue-specific turnover and nitrogen discrimination for the study organisms is important for accurate interpretation of isotopic data. We measured δ15 N turnover in liver and muscle tissue in juvenile mummichogs, Fundulus heteroclitus, following a laboratory diet switch. Liver tissue turned over significantly faster than muscle tissue suggesting the potential for a multiple tissue stable isotope approach to study movement and trophic position over different time scales; metabolism contributed significantly to isotopic turnover for both liver and muscle. Nitrogen diet-tissue discrimination was estimated at between 0.0 and 1.2‰ for liver and –1.0 and 0.2‰ for muscle. This is the first experiment to demonstrate a significant variation in δ15 N turnover between liver and muscle tissues in a fish species.This study was funded by NSF LTER grant OCE-9726921

Biophysical Factors Affecting the Distribution of Demersal Fish around the Head of a Submarine Canyon Off the Bonney Coast, South Australia

We sampled the demersal fish community of the Bonney Canyon, South Australia at depths (100–1,500 m) and locations that are poorly known. Seventy-eight species of demersal fish were obtained from 12 depth-stratified trawls along, and to either side, of the central canyon axis. Distributional patterns in species richness and biomass were highly correlated. Three fish assemblage groupings, characterised by small suites of species with narrow depth distributions, were identified on the shelf, upper slope and mid slope. The assemblage groupings were largely explained by depth (ρw = 0.78). Compared to the depth gradient, canyon-related effects are weak or occur at spatial or temporal scales not sampled in this study. A conceptual physical model displayed features consistent with the depth zonational patterns in fish, and also indicated that canyon upwelling can occur. The depth zonation of the fish assemblage was associated with the depth distribution of water masses in the area. Notably, the mid-slope community (1,000 m) coincided with a layer of Antarctic Intermediate Water, the upper slope community (500 m) resided within the core of the Flinders Current, and the shelf community was located in a well-mixed layer of surface water (<450 m depth)

Toward a standardised protocol for the stable isotope analysis of scleractinian corals

peer reviewedRationale: The stable isotope analysis of carbon and nitrogen is a powerful tool in many ecological studies, but different sample treatments may affect stable isotope ratios and hamper comparisons among studies. The goal of this study was to determine whether treatments that are commonly used to prepare scleractinian coral samples for stable isotope analysis yield different δ15N and δ13C values, and to provide guidelines toward a standardised protocol. Methods: The animal tissues and Symbiodiniaceae of two symbiotic scleractinian coral species (Stylophora pistillata and Porites lutea) were divided into subsamples to test the effects of the drying method, lipid extraction, acidification treatment and water washing. All of the subsamples were analysed for δ15N and δ13C values, using continuous flow – elemental analysis – isotope ratio mass spectrometry. Results: The drying method and lipid extraction treatment had no substantial effects on the δ15N and δ13C values of Symbiodiniaceae and animal tissues. Acid treatment did cause significant differences in δ13C values (mean differences ≤ 0.5‰, with individual samples becoming up to 2.0‰ more negative), whereas no ecologically significant differences were observed in δ15N values. Animal tissue δ13C values may vary depending on whether samples are washed or not. Conclusions: For going toward a standardised protocol in coral research, we recommend using either available drying method (as they are equally acceptable) for the stable isotope analysis of scleractinian corals, examining the need for lipid extraction on a case-by-case basis, performing a direct acidification of Symbiodiniaceae and animal tissues, and avoiding washing animal tissue with distilled water

Submarine Canyons in the Mediterranean: A Shelter for Cold-Water Corals

5 pagesIn the Mediterranean Sea, many of the locations where cold-water coral communities have been reported and documented tend to be associated to submarine canyon environments. This contribution provides a summary of the Mediterranean canyons where, up to date, cold-water corals develop, describing the most common species, their water depth distribution and degree of preservation, and the prevalent hydrodynamic forcing at specific sites. Considering that the inventory, characterisation and detailed mapping of Mediterranean submarine canyons is far from complete, this compilation urges to focus new research and exploration efforts on these morphological features, as they appear to act as natural shelters of cold-water coral communities at present time

Applying new tools to cephalopod trophic dynamics and ecology: perspectives from the Southern Ocean Cephalopod Workshop, February 2-3, 2006

A two day workshop on Southern Ocean cephalopods was held in Hobart, Tasmania, Australia prior to the triennial 2006 Cephalopod International Advisory Council (CIAC) symposium. The workshop provided a second international forum to present the current state of research and new directions since the last Southern Ocean cephalopod meeting held in 1993. A major focus of the workshop was trophic ecology and the use of a variety of tools that can be applied in Southern Ocean trophic studies for both cephalopod and predator researchers. New tools that are being used as trophic indicators and tracers in food chain pathways include stable isotope, heavy metal and fatty acid signature analysis. Progress is also being made on understanding squid population dynamics in relation to other key components of the ecosystem by incorporating squid data in ecosystem models. Genetic barcoding is now of great value to fish taxonomy as well as other groups and it is expected that a cephalopod barcoding initiative will be an important tool for cephalopod taxonomy. There is a current initiative to produce a new cephalopod beak identification guide to assist predator biologists in identifying cephalopod prey items. There were also general discussions on specific taxonomic issues, Southern Ocean Cephalopod paralarvae and parasites, and suggestions for future CIAC workshop topics