Control of Branchionus sp. and Amoeba sp. in cultures of Arthrospira sp.

Abstract

ABSTRACT. Cultivation of cyanobacterium Arthrospira sp. has been developed in many countries for the production of proteins, pigments and other compounds. Outdoor mass cultures are often affected by biological contamination, drastically reducing productivity as far as bringing death. This study evaluates the control of Branchionus sp. and Amoeba sp. with two chemical compounds: urea (U) and ammonium bicarbonate (AB), in laboratory conditions and outdoor mass culture of Arthrospira sp. The lethal concentration 100 (LC100) at 24 h for Branchionus sp. and Amoeba sp. determined was of 60-80 mg L -1 (U) and 100-150 mg L -1 (AB). The average effective inhibition concentration for 50% of the population (IC50) in Arthrospira sp., after 72 h, was 80 mg L -1 (U) and 150 mg L -1 (AB). The application of doses of 60 mg L -1 (U) or 100 mg L -1 (AB) in the outdoor mass culture of this contaminated microalga, completely inhibited grazing and did not affect the growth of Arthrospira sp. but rather promoted rapid recovery of algal density at levels prior to infestation. These compounds provided an economical and effective control of predators in cultures of Arthrospira sp.

Contaminating microzooplankton in outdoor microalgal mass culture systems: An ecological viewpoint

“…If one or a few contaminating species can be determined, contamination control can be acquired gradually based on previous experience from references and well-designed laboratory and outdoor experiments. Méndez and Uribe [11] reported that the application of 60 mg/L urea or 100 mg/L ammonium bicarbonate completely inhibited the grazing of Branchionus sp. and Amoeba sp., and did not affect the growth of Spirulina.…”

“…However, the occurrence, population dynamics and impact of microzooplankton on microalgal culture has not well been studied [11][12][13]. In practice, many control strategies have been proposed to overcome the challenges of biological contamination: for instance, zooplankton predators of a relatively large size can be washed out by reducing the retention time of the algal culture [14], or removed using different sizes of mesh in algal pond [15][16][17][18], or treated with sonication [19]; but in most cases specific chemicals are utilized to control zooplankton contamination in mass algal cultures [11,20,21]. It is also worth mentioning the important study of Post et al [22], who demonstrated that lowering salinity could mitigate the effects of amoeba and ciliates in a Dunaliella pond.…”

Special issue in honour of Prof. Reto J. Strasser - Efficacy of botanical pesticide for rotifer extermination during the cultivation of Nannochloropsis oculata probed by chlorophyll a fluorescence transient

“…It seems that ammonium bicarbonate is the most effective agent for exterminating rotifers. The ammonium toxicity is related to nonionized ammonia, which can exterminate most of the rotifers (Méndez and Uribe 2012). However, growth inhibition of microalgae caused by ammonia also occurs (Yuan et al 2011).…”

Minimising losses to predation during microalgae cultivation

“…Most approaches rely on the culturing of extremophiles under highly selective growth conditions (Borowitzka 2005) with regards to pH or, in the case of marine species, salinity, with the latter having the potential double benefit of stimulating productivity while suppressing increases in invader populations (Bartley et al 2013). Other methods can include filtration and the use of chemical pesticides (Bacellar Mendes and Vermelho 2013; Wang et al 2013; McBride et al 2014), although the former can only work when predators are relatively large, while imprudent use of pesticides can destroy the microalgae along with the predator (Méndez and Uribe 2012). Pulsed electric fields, intended to cause structural and functional damage to predators while leaving the microalgal cells intact, have also been suggested (Rego et al 2015).…”