Springer Science and Business Media LLC

Environmental disturbances and fishing are well known drivers of coral reef fish population size, length-frequency, and assemblage structure. However, few studies have partitioned the spatial and temporal impacts of multiple disturbance events and long-term no-take marine reserve (NTMR) protection on the biomass of juvenile and adult reef-fishes based on the known size of sexual maturity. Here, we document responses in the biomass of juvenile and adult wrasses (Labridae) Hemigymnus melapterus, H. fasciatus, Cheilinus fasciatus, and Oxycheilinus digramma, to environmental disturbance events, NTMR protection, and predator density on inshore fringing coral reefs at the Palm and Whitsunday Island groups, Great Barrier Reef (GBR), Australia from 2007 to 2018 (12 years). The biomass of juvenile and adult wrasses on inshore GBR reefs were driven predominantly by benthic habitat associations, rather than by NTMR protection or density of wrasse predators (Plectropomus spp.). Despite similar species-specific associations of juvenile and adult wrasses with benthic cover, juvenile wrasse biomass consistently declined following coral bleaching and cyclone events. Conversely, adult wrasses had variable responses to disturbance events, including some increases in biomass. Disturbance-mediated declines in the biomass of juvenile wrasses are likely to generate ongoing reductions in the abundance of these species on inshore GBR reefs. Our findings provide further evidence that habitat loss impacts a range of coral reef fishes beyond those that are directly reliant upon live coral. Shifts in assemblage structure, loss of biodiversity, and reductions in fishery productivity will become increasingly apparent in coral reef ecosystems if anthropogenic global warming continues unabated.

Three forms of the iota-producing carrageenophyte,Eucheuma denticulatum, and four forms of the kappa-producing carrageenophyte,Kappaphycus alvarezii, obtained from seaweed farms in the Philippines have been grown in the laboratory under unialgal and axenic conditions. Comparison of media indicates that seed stocks of both species can be cultured using enriched seawater media ranging from ESS and SWMD-1 to inexpensive soil extract (Erdshreiber's) or holding in sterile seawater for up to three weeks. Micropropagation has been successful with at least two forms of each species resulting in clonal propagation from axenic explants within 4 to 8 weeks. Callus development and branch regeneration has also been induced in two forms of each species. The results indicate that culture facilities in the farming areas of the Philippines could maintain high-yielding and rapidly growing seed stock for the seaweed farmers.

Vampirovibrio chlorellavorus is an obligate, predatory bacterial pathogen of the genus Chlorella. It is recognized as an important pathogen of Chlorella sorokiniana, field isolate DOE 1412, a highly-favored microalga for cultivation in outdoor reactors in the arid USA Southwest for feedstocks used in biofuel production. To determine the V. chlorellavorus titer, based on gene copy number, required to cause infection and mortality of C. sorokiniana in an experimental outdoor reactor, a multiplexed quantitative polymerase chain reaction (qPCR) assay was developed for pathogen detection, based on the 16S and 18S ribosomal RNA gene of V. chlorellavorus and C. sorokiniana, respectively. The assay was further used to establish the optimal effective concentration of benzalkonium chloride required to achieve a below “disease-threshold”-bacterial titer, while minimizing biocidal effects on algal growth and enable economic biomass production. Reactors treated with 2.0 ppm benzalkonium chloride at four-day intervals throughout the cultivation cycle experienced runs of 22 days or longer, compared to 12 days for the untreated control. The qPCR assay was used to estimate disease severity over time using the Area Under the Disease Progress Stairs (AUDPS) metric, indicating a severity rating of 0.016 and 62.308 in biocide-treated and untreated cultures, respectively. The near-real time assay detected as few as 13 copies of V. chlorellavorus, allowing for the recognition of its presence in the reactor just before algal cell density decreased, an indication of pathogen attack, while also informing the timing of biocide applications to minimize DOE 1412 infection such that harvestable biomass could be produced.

Recently, yeast and microalgae mixed cultures have been widely used in biological effluent treatments and biofuel production because such cultures show many advantages over pure cultures. However, industrial effluents often contain toxic compounds; therefore, it is important to evaluate the cell stress response when growing in such conditions during the mixed culture development. In this work, flow cytometry (FC) was used to differentiate Rhodosporidium toruloides cells from Tetradesmus obliquus cells, based on their size, internal complexity, and chlorophyll content. FC coupled with SYTOX Green and CFDA fluorochromes was also used to characterize the cell stress response of R. toruloides and T. obliquus individual cells in a mixed culture. This work describes, for the first time, a simple and easy method to monitor individual stress response of R. toruloides and T. obliquus cells growing in mixed cultures on brewery effluents, using FC coupled with fluorescent dyes.