Fluorescence census techniques for the early detection of coral recruits

Many coral recruits are very small and often cryptic at settlement making them difficult to detect with normal census techniques. Here we show that fluorescence census techniques can increase the accuracy of juvenile coral counts in highly fluorescent taxa. Using fluorescent filters at night, counts of coral recruits were 20–50% higher than during the day. Acropora abundances were up to 300% higher, the difference being made up of cryptic individuals, and individuals that were too small to see during the day. Fluorescence techniques will be particularly useful in regions where fluorescent taxa are dominant, such as most Indo-Pacific reefs. The technique offers particular promise to determine the influence of early post-settlement mortality on the ecology of fluorescent taxa, because corals can be detected at the size at which they settle

Calcification by juvenile corals under heterotrophy and elevated CO[subscript 2]

Ocean acidification (OA) threatens the existence of coral reefs by slowing the rate of calcium carbonate (CaCO[subscript 3]) production of framework-building corals thus reducing the amount of CaCO3 the reef can produce to counteract natural dissolution. Some evidence exists to suggest that elevated levels of dissolved inorganic nutrients can reduce the impact of OA on coral calcification. Here, we investigated the potential for enhanced energetic status of juvenile corals, achieved via heterotrophic feeding, to modulate the negative impact of OA on calcification. Larvae of the common Atlantic golf ball coral, Favia fragum, were collected and reared for 3 weeks under ambient (421 μatm) or significantly elevated (1,311 μatm) CO[subscript 2] conditions. The metamorphosed, zooxanthellate spat were either fed brine shrimp (i.e., received nutrition from photosynthesis plus heterotrophy) or not fed (i.e., primarily autotrophic). Regardless of CO[subscript 2] condition, the skeletons of fed corals exhibited accelerated development of septal cycles and were larger than those of unfed corals. At each CO[subscript 2] level, fed corals accreted more CaCO[subscript 3] than unfed corals, and fed corals reared under 1,311 μatm CO[subscript 2] accreted as much CaCO[subscript 3] as unfed corals reared under ambient CO[subscript 2]. However, feeding did not alter the sensitivity of calcification to increased CO[subscript 2]; ∆ calcification/∆Ω was comparable for fed and unfed corals. Our results suggest that calcification rates of nutritionally replete juvenile corals will decline as OA intensifies over the course of this century. Critically, however, such corals could maintain higher rates of skeletal growth and CaCO[subscript 3] production under OA than those in nutritionally limited environments.National Science Foundation (U.S.) (OCE-1041106)National Science Foundation (U.S.) (OCE-1041052

Transcriptome sequencing and annotation of the polychaete Hermodice carunculata (Annelida, Amphinomidae)

Background: The amphinomid polychaete Hermodice carunculata is a cosmopolitan and ecologically important omnivore in coral reef ecosystems, preying on a diverse suite of reef organisms and potentially acting as a vector for coral disease. While amphinomids are a key group for determining the root of the Annelida, their phylogenetic position has been difficult to resolve, and their publically available genomic data was scarce. Results: We performed deep transcriptome sequencing (Illumina HiSeq) and profiling on Hermodice carunculata collected in the Western Atlantic Ocean. We focused this study on 58,454 predicted Open Reading Frames (ORFs) of genes longer than 200 amino acids for our homology search, and Gene Ontology (GO) terms and InterPro IDs were assigned to 32,500 of these ORFs. We used this de novo assembled transcriptome to recover major signaling pathways and housekeeping genes. We also identify a suite of H. carunculata genes related to reproduction and immune response. Conclusions: We provide a comprehensive catalogue of annotated genes for Hermodice carunculata and expand the knowledge of reproduction and immune response genes in annelids, in general. Overall, this study vastly expands the available genomic data for H. carunculata, of which previously consisted of only 279 nucleotide sequences in NCBI. This underscores the utility of Illumina sequencing for de novo transcriptome assembly in non-model organisms as a cost-effective and efficient tool for gene discovery and downstream applications, such as phylogenetic analysis and gene expression profiling