Seminar: Ammar Hanif

Title: Diet and Stomach Microbiota of Juvenile Menhaden, a Key Forage Filter Feeding Fish Species

Speaker: Ammar Hanif (Graduate Student, UMCES-IMET)

Abstract: Menhaden represent a key filter feeding forage fish species that serves as a trophic link between the plankton and piscivorous predators in the marine environment. Dietary analysis is difficult because >80 % of the stomach content consists of amorphous material. DNA metabarcoding, using the V3-V4 hypervariable region of 16S and the V4-V5 hypervariable region of 18S rRNA gene sequences respectively, has allowed a comprehensive assessment of gut microbiota and diet items. The method was optimized looking at DNA preparation, comparison of two sequencing methods, determination of the representation of host DNA, quality filtering of sequences, post-sequence processing and taxonomic identification. Stomach microbiota and diet were compared in juvenile Gulf menhaden, Brevoortia patronus, caught at two locations, Two Mile Channel and St. Vincent Sound, in Apalachicola Bay, FL in May and July, 2013. The stomach microbiota of samples from both locations showed a predominance of Proteobacteria, Chloroflexi, Bacteroidetes, Acidobacteria and Actinobacteria, although significant differences in composition at the class level were seen in samples from the different locations. The microbiota from Two-mile Channel showed a higher level of taxonomic richness and there was a strong association between the microbiota and sampling location, correlating with differences in salinity. Approximately 1050 diet items were identified, although significant differences in the species represented were found in samples from the two locations. Members of the Stramenopile/Alveolate/Rhizaria (SAR) clade account for 66 % representation in samples from Two Mile Channel, dominated by the diatoms Cyclotella and Skeletonema, as well as the ciliate Oligotrichia. In contrast, Metazoa (zooplankton) dominate in samples from St. Vincent Sound, accounting for over 80 % of the reads. These are mainly Acartia copepods. Since ciliates are considered to be microzooplankton, this means there is just over 60 % representation of phytoplankton in samples from Two Mile Channel and over 90 % representation of zooplankton in samples from St. Vincent Sound. Overall, we demonstrate a wider picture of the diversity of menhaden juvenile diet items that supports a picture of menhaden as an environmental sampler.