The effect of Ascophyllum nodosum (Ochrophyta) extract powder on the epibiosis of Kappaphycus alvarezii (Rhodophyta) commercially cultivated on floating rafts

Abstract

Acadian marine plant extract powder (AMPEP), a product derived from Ascophyllum nodosum, has been widely used as a plant growth stimulant and recently has been tested on seaweeds with successful results on increasing growth and preventing epibiosis in Kappaphycus alvarezii cultivation. Although, the AMPEP ability to deal with epibiosis on seedlings cultivated in tubular nets and its commercial implications are still unknown. Between July 2012 and September 2013, three sampling periods were randomly selected at a Brazilian commercial farm in order to evaluate the effect of AMPEP on K. alvarezii daily growth rate, carrageenan yield and quality, and epibiont settling. Ten tubular nets containing three 100 g seedlings each (five treated with AMPEP and five not) were tied on floating rafts. Control samples displayed higher biomass of epibionts [0.76 ± 0.52 g (dry mass) tubular net−1] when compared to the AMPEP-treated samples [0.26 ± 0.27 g (dry mass) tubular net−1]. Carrageenan yield (44.65 ± 7.09 %) showed no significant difference between treatments (t = 0.46; p = 0.64), with larger percentages by the end of the third sampling period (F = 130.96, p < 0.001). When comparing AMPEP treatment with the control, carrageenan gel strength (252.14 ± 82.4 g cm−3) and viscosity (106.72 ± 45.11 cP) showed opposite results. The gel strength of AMPEP-treated samples was higher than their controls (t = 2.88; p = 0.007), while the gel viscosity of samples treated with AMPEP was lower than samples from their control (t = −2.4; p = 0.02). K. alvarezii daily growth rates between treatments were not different (t = 0.92; p = 0.36), exhibiting low commercial values probably due to herbivory. It was concluded that AMPEP was efficient against epibiont settlement on K. alvarezii cultivated on tubular nets tied on floating rafts maintaining favorable commercial results for carrageenan yield.