The characteristics of nutrient removal and inhibitory effect of Ulva clathrata on Vibrio anguillarum 65

Abstract

To investigate the ecological effect of macroalgae on de-eutrophication and depuration of mariculture seawater, the variation of dissolved inorganic nitrogen (DIN) and phosphate (DIP), the amount of Vibrio anguillarum, and total heterotrophic bacteria in Ulva clathrata culture, as well as on the algal surface, were investigated by artificially adding nutrients and V. anguillarum strain 65 from February to April 2006. The results indicated that U. clathrata not only had strong DIN and DIP removal capacities, but also showed a significant inhibitory effect on V. anguillarum, although not reducing the total heterotrophic bacteria. Vibrio anguillarum 65 dropped from 5∼8× 10 7 cfu mL −1 to 10 cfu mL −1 (clone-forming units per mL) in 10 g L −1 of fresh U. clathrata culture within 2 days; i.e., almost all of the Vibrios were efficiently eradicated from the algal culture system. Our results also showed that the inhibitory effect of U. clathrata on V. anguillarum strain 65 was both DIN-and DIP-dependent. Addition of DIN and DIP could enhance the inhibitory effects of the algae on the Vibrio, but did not reduce the total heterotrophic bacteria. Further studies showed that the culture suspension in which U. clathrata was pre-cultured for 24 h also had an inhibitory effect on V. anguillarum strain 65. Some unknown chemical substances, either released from U. clathrata or produced by the alga associated microorganisms, inhibited the proliferation of V. anguillarum 65.

Biofiltering efficiency, uptake and assimilation rates of Ulva clathrata (Roth) J. Agardh (Clorophyceae) cultivated in shrimp aquaculture waste water

“…Finally, macroalgae can excrete allelopathic substances and inhibit phytoplankton growth. Production and excretion of allelochemicals by Ulva is an effective defence strategy against other phototrophic organisms competing for light and nutrients like phytoplankton and epiphytes (Wang et al 2007a), and against pathogens (Lu et al 2008). It has been found that green-tide forming algae, particularly Ulvales, produce allelopathic effects with release of toxic substances for several microalgae (Nelson et al 2003), including harmful algal blooms (Jin and Dong 2003;Wang et al 2007a, b).…”

“…It has been found that U. clathrata can have high growth rates and yields under wide ranges of temperature, salinity and pH, even growing without inorganic carbon supplementation and with low water exchange (Moll and Deikman 1995). Although large-scale cultivation of U. clathrata has been maintained for food and feed grade use (Moll and Leon 2007), studies on the potential use of the species in integrated aquaculture systems are scarce (Lu et al 2008). This paper aims to evaluate growth, biofiltering efficiency, nutrient uptake and assimilation rates of U. clathrata, cultivated under outdoor conditions within aquaculture waste water from a semi-intensive shrimp farm, located off the south coast of Brazil.…”

The Phytoplankton Nannochloropsis oculata Enhances the Ability of Roseobacter Clade Bacteria to Inhibit the Growth of Fish Pathogen Vibrio anguillarum

“…Regarding the second mechanism described above involving complex intercellular interactions, there was no direct inhibition of fish pathogens by phytoplankton, in contrast to other findings [39], [40]. As there was no difference in the viabilities of V. anguillarum between ESM and NCF (Fig.…”

Probiotic Biofilms

“…The second one, and more complex, involves a direct interaction between phytoplankton and microbes such as phytoplankton and pathogenic bacteria, probiotic bacteria and pathogenic bacteria, and phytoplanktonprobiotic bacteria and pathogenic bacteria. Regarding the first mechanism, competition for entry of nutrients, the abundance of the Roseobacter clade in the coastal sea is correlated with the release of organic substances from natural phytoplankton blooms such as dimethylsulfoniopropionate (DMSP) and amino acids [105,106]. In turn N. oculata may also excrete some substances similar to DMSP or amino acids that support more optimally bacterial growth of the clade [94].…”