Marine Biology

SUMMARYParasites can exert strong effects on population to ecosystem level processes, but data on parasites are limited for many global regions, especially tropical marine systems. Characterizing parasite diversity and distributions are the first steps towards understanding the potential impacts of parasites. The Panama Canal serves as an interesting location to examine tropical parasite diversity and distribution, as it is a conduit between two oceans and a hub for international trade. We examined metazoan and protistan parasites associated with ten oyster species collected from both Panamanian coasts, including the Panama Canal and Bocas del Toro. We found multiple metazoan taxa (pea crabs,Stylochusspp.,Urastoma cyrinae). Our molecular screening for protistan parasites detected four species ofPerkinsus(Perkinsus marinus, Perkinsus chesapeaki, Perkinsus olseni, Perkinsus beihaiensis) and several haplosporidians, including two genera (Minchinia, Haplosporidium). Species richness was...

Marine microbes provide the backbone for pelagic ecosystems by cycling and fixing nutrients and establishing the base of food webs. Microbial communities are often assumed to be highly connected and genetically mixed, with localized environmental filters driving minor changes in structure. Our study applied high-throughput Illumina 16S ribosomal RNA gene amplicon sequencing on whole-community bacterial samples to characterize geographic, environmental, and stochastic drivers of community diversity. DNA was extracted from seawater collected from the surface (N = 18) and at depth just below the deep chlorophyll-a maximum (DCM mean depth = 115.4 m; N = 22) in the Sargasso Sea and adjacent oceanographic regions. Discrete bacterioplankton assemblages were observed at varying depths in the North Sargasso Sea, with a signal for distance-decay of bacterioplankton community similarity found only in surface waters. Bacterial communities from different oceanic regions could be distinguished st...

Protistan oyster parasites in the genus Bonamia have been observed in recent years infecting new hosts on five continents, with most of these parasites genetically similar to austral species Bonamia exitiosa and Bonamia roughleyi. Identification of the newly observed parasites as one or another of these described species has been complicated by the fact that B. exitiosa and B. roughleyi are phylogenetically indistinguishable at the small-subunit ribosomal DNA (SSU rDNA) level, with samples of B. roughleyi type material no longer available for genetic re-analyses using more informative internal transcribed spacer (ITS) region DNA sequences. To resolve this issue, we evaluated B. roughleyi in field collections of hosts Saccostrea glomerata and Ostrea angasi (as well as Crassostrea gigas) in New South Wales, Australia in 2006 and 2007, and re-analyzed histological samples from the original description of this parasite species using in situ hybridization. Despite (1) reports of the oyster disease putatively caused by B. roughleyi during the time of collections, (2) the observation of gross lesions characteristic of the disease, and (3) the observation of B. roughleyi cells in association with the lesions, we detected a Bonamia sp. by PCR in just 1/42 O. angasi (2.4%), and 1/608 S. glomerata (0.2%), the latter oyster of which is the type host. SSU rDNA sequences of the amplicons were nearly identical to those of B. exitiosa and B. roughleyi, and phylogenetic analysis of ITS region sequences placed them on a B. exitiosa clade. A Haplosporidium sp. sequence similar to that of H. costale was PCR-amplified from nearly half the S. glomerata and O. angasi, but no Haplosporidium sp. was observed histologically. Our inability to identify a Bonamia sp. sequence in association with the B. roughleyi observed histologically suggests that this parasite is not a Bonamia sp. at all, and should be regarded as B. roughleyi nomen dubium. We conclude that the Bonamia sp. that we and other investigators detected in southeastern Australian S. glomerata and O. angasi was B. exitiosa.

Kudoa inornata is a myxosporean parasite that develops in the somatic muscle of spotted seatrout Cynoscion nebulosus, an economically and ecologically important fish in estuaries and harbors in southeastern North America. In South Carolina (SC), USA, over 90% of wild adult spotted seatrout are infected. To inform potential mitigation strategies, we conducted 3 experiments using naïve sentinel seatrout and infectious stages of K. inornata naturally present in raw water from Charleston Harbor, SC, to determine (1) if K. inornata infection follows a seasonal pattern, and (2) how long it takes for myxospores to develop in fish muscle. Infection by K. inornata was determined by visual detection of myxospores in fish muscle squashes, and any visually negative samples were then assayed for K. inornata ribosomal DNA using novel parasite-specific PCR primers. We observed that K. inornata infection in seatrout followed a seasonal pattern, with high prevalence when water temperature was highest (27-31°C; July-September) and infections that were either covert (at ~13-15°C) or not detected (<13°C) at the lowest water temperatures in January-February. Myxospore development occurred within 476 degree-days, i.e. 2 wk in a typical SC summer. Infection was dependent on fish density, which limited presumptive actinospore dose. Our findings suggest that the life cycle of the parasite may be disrupted by preventing spore-rich seatrout carcasses (e.g. at angler cleaning stations) being thrown back into harbors and estuaries throughout the year.

For endangered sea turtle populations, microbial pathogens of developing embryos are of concern at nesting sites around the globe. For olive ridley turtles, hatching success is markedly lower at mass-nesting sites than at solitary nesting beaches, a case presumably resulting from the abundance of decomposing eggs generated by nesting turtles destroying adjacent eggs. This organic input drives microbial activity, affecting the nest environment (i.e. pO2 and temperature), and reducing embryo survivorship and hatching success. However, the composition of microbial communities in nest sand has not been studied in detail and the presence of potential pathogens can, therefore, not be discounted. As a part of a larger study that investigated microbial abundance in nests, we employed high-throughput DNA sequencing to compare fungal and bacterial composition in nest sand from areas of disparate embryo survivorship. While we found no differences in alpha-diversity (mean operational taxonomic ...

For many taxa, including isomorphic haplodiplontic macroalgae, determining sex and ploidy is challenging, thereby limiting the scope of some population demographic and genetic studies. Here, we used double‐digest restriction site‐associated DNA sequencing (ddRAD‐seq) to identify sex‐linked molecular markers in the widespread red alga Agarophyton vermiculophyllum. In the ddRAD‐seq library, we included 10 female gametophytes, 10 male gametophytes, and 16 tetrasporophytes from one native and one non‐native site (N = 40 gametophytes and N = 32 tetrasporophytes total). We identified seven putatively female‐linked and 19 putatively male‐linked sequences. Four female‐ and eight male‐linked markers amplified in all three life cycle stages. Using one female‐ and one male‐linked marker that were sex‐specific, we developed a duplex PCR and tested the efficacy of this assay on a subset of thalli sampled at two sites in the non‐native range. We confirmed ploidy based on the visual observation of reproductive structures and previous microsatellite genotyping at 10 polymorphic loci. For 32 vegetative thalli, we were able to assign sex and confirm ploidy in these previously genotyped thalli. These markers will be integral to ongoing studies of A. vermiculophyllum invasion. We discuss the utility of RAD‐seq over other approaches previously used, such as RAPDs (random amplified polymorphic DNA), for future work designing sex‐linked markers in other haplodiplontic macroalgae for which genomes are lacking.

Benthic microalgae are of great significance to coastal productivity and nutrient cycling, yet determinants of their biogeography and community assembly remain unclear. We identified and compared spatial and environmental mechanisms that shape beach diatom biogeography and diversity at regional scales. We sampled at various spatial scales (from 10 cm to 120 km) from 4 barrier island beaches in South Carolina, USA, and characterized diatom assemblages using DNA metabarcoding. Twelve environmental variables from sediments, adjacent waters, and atmosphere were recorded. Despite attempts to sample from similar habitat types, environmental factors varied among islands. Correspondingly, biomass and α-diversity metrics likewise varied and were positively related to sediment nutrient levels. Community composition also varied, with each island dominated by different diatom taxa. Redundancy analysis revealed that spatial influences, in addition to environmental factors (water temperature and ...