Development of a multiplex qPCR for the quantification of three protozoan parasites of the eastern oyster Crassostrea virginica

A multiplex quantitative PCR (qPCR) assay for the simultaneous detection of 3 eastern oyster Crassostrea virginica parasites, Perkinsus marinus, Haplosporidium nelsoni, and H. costale, was developed using 3 different fluorescently labeled hydrolysis probes. The primers and probe from a previously validated singleplex qPCR for P. marinus detection were combined with newly designed primers and probes specific for H. nelsoni and H. costale. The functionality of the multiplex assay was demonstrated on 2 different platforms by the linear relationship of the standard curves and similar cycle threshold (CT) values between parasites. Efficiency of the multiplex qPCR assay on the Roche and BioRad platforms ranged between 93 and 101%. The sensitivity of detection ranged between 10 and 100 copies of plasmid DNA for P. marinus and Haplosporidium spp., respectively. The concordance between the Roche and BioRad platforms in the identification of the parasites P. marinus, H. nelsoni, and H. costale was 91, 97, and 97%, respectively, with a 10-fold increase in the sensitivity of detection of Haplosporidium spp. on the BioRad thermocycler. The concordance between multiplex qPCR and histology for P. marinus, H. nelsoni, and H. costale was 54, 57, and 87%, respectively. Discordances between detection methods were largely related to localized or low levels of infections in oyster tissues, and qPCR was the more sensitive diagnostic. The multiplex qPCR developed here is a sensitive diagnostic tool for the quantification and surveillance of single and mixed infections in the eastern oyster

Mapping the world's coral reefs using a global multiscale earth observation framework

Coral reefs are among the most diverse and iconic ecosystems on Earth, but a range of anthropogenic pressures are threatening their persistence. Owing to their remoteness, broad spatial coverage and cross‐jurisdictional locations, there are no high‐resolution remotely sensed maps available at the global scale. Here we present a framework that is capable of mapping coral reef habitats from individual reefs (~200 km2) to entire barrier reef systems (200 000 km2) and across vast ocean extents (>6 000 000 km2). This is the first time this has been demonstrated using a consistent and transparent remote sensing mapping framework. The ten maps that we present achieved good accuracy (78% mean overall accuracy) from multiple input image datasets and training data sources, and our framework was shown to be adaptable to either benthic or geomorphic reef features and across diverse coral reef environments. These new generation high‐resolution map data will be useful for supporting ecosystem risk assessments, detecting change in ecosystem dynamics and targeting efforts to monitor local‐scale changes in coral cover and reef health

Insecticides and a fungicide affect multiple coral life stages

Coral reefs are under threat from land-based agricultural pollutants on a global scale. The vulnerability of early life stages of corals is of particular concern. Here, we compared the sensitivity of gametes, larvae and adult branches of the broadcast-spawning coral Acropora millepora (Ehrenberg) to a number of common pollutants, including 4 classes of insecticides—2 organophosphates (chlorpyrifos, profenofos), an organochlorine (endosulfan), a carbamate (carbaryl) and a pyrethroid (permethrin)—and a fungicide (2-methoxyethylmercuric chloride, MEMC). Fertilisation of gametes was not affected by any of the insecticides at concentrations up to 30 µg l–1. In contrast, settlement and metamorphosis were reduced by between 50 and 100% following 18 h exposure to very low concentrations (0.3 to 1.0 µg l–1) of each insecticide class. The insecticides had few visible effects on adult branches following 96 h exposure to a concentration of 10 µg l–1, with the exception of profenofos, which caused polyp retraction, bleaching (i.e. algal symbiont densities were reduced) and a slight reduction in photosynthetic efficiency of the algal symbionts. The fungicide MEMC affected all life-history stages: both fertilisation and metamorphosis were inhibited at 1.0 µg l–1, and polyps became withdrawn and photosynthetic efficiency was slightly reduced at 1.0 µg l–1. At 10 µg l–1 MEMC, branches bleached and some host tissue died. This high susceptibility of coral larvae to pesticides at concentrations around their detection limit highlights the critical need to assess toxicity against all life-history stages of keystone organisms: to focus on mature individuals may underestimate species sensitivity

Keeping It Local: Dispersal Limitations of Coral Larvae to the High Latitude Coral Reefs of the Houtman Abrolhos Islands.

In 2011 the first recorded bleaching event for the high latitude Houtman Abrolhos Islands (HAI) coral communities was documented. This bleaching event highlighted the question of whether a supply of 'heat tolerant' coral recruits from the tropical north would be sufficient to provide a level of resistance for these reefs to future warming events. Using Lagrangian modelling we showed that due to its regional isolation, large-scale larval input from potential tropical northern source populations to the HAI is unlikely, despite the southward flowing Leeuwin current. Successful recruitment to artificial substrates was recorded following the bleaching event. However, this was negligible (0.4 ± 0.1 recruits per tile) compared to 2013 post impact recruitment (128.8 ± 15.8 recruits per tile). Our data therefore provides preliminary evidence suggesting that the connectivity of the HAI with coral communities in the north is limited, and population maintenance and recovery is likely driven primarily by self-recruitment. Given the low thermal tolerance of the HAI coral communities, the dominance of Acropora, and the apparent reliance on self-recruitment, an increased frequency of thermally anomalous conditions at the HAI (such as experienced in 2011) has the potential to reduce the long-term stability of the HAI coral populations and species that depend upon them

a) NOAA Sea surface temperature data from 2010–2013. Note 2010 represents a typical temperature profile for HAI, unlike the anomalous temperatures seen in 2011. b) Average number of coral recruits tile^-1 (± Standard Error) at the HAI following the autumn mass spawning from 2011–2013.

<p>a) NOAA Sea surface temperature data from 2010–2013. Note 2010 represents a typical temperature profile for HAI, unlike the anomalous temperatures seen in 2011. b) Average number of coral recruits tile^-1 (± Standard Error) at the HAI following the autumn mass spawning from 2011–2013.</p