Background: Cultivation of algae for conversion to biofuels has gained global interest. Outdoor raceway
cultivation is preferred because of its lower capital and operating costs. A major disadvantage of outdoor
cultivation is susceptibility of algal crops to attack by predatory rotifers. In order to quantify the impact of
rotifer attack on different species of algae, we evaluated the growth of eleven microalgal species over a 21-d
period after being infected by the predatory rotifer
Brachionus rubens.
Results: Of the eleven species,
Chlorella sorokiniana was the most susceptible with rapid decline in algal growth
concomitant with increase in rotifer population growth (3.82/d). In contrast,
Synechococcus elongatus
and
Scenedesmus dimorphus
were both resistant to the rotifer and suppressed rotifer growth (-0.06/d). An index of
algal species susceptibility to be consumed by the rotifer was generated with
C. sorokiniana as the baseline
(index = 1.000) indicating most susceptible among species tested. Other species' susceptibilities are indicated
in parenthesis as follows:
Monoraphidium spp. (0.997),
Chlamydomonas globosa (0.827),
Botryococcus braunii (0.740),
Chlorella minutissima (0.570),
Chlamydomonas augustae (0.530),
Chlamydomonas yellowstonensis (0.500),
Scenedesmus bijuga (0.420), and
Haematococcus pluvialis (0.360). Two species, namely,
S. dimorphus
and
S. elongatus were unique in that they exhibited an ability to suppress the growth of the rotifer as indicated
by the decline in rotifer populations in their presence.
Conclusions: Variations in susceptibility of algal species to rotifer predation could be a result of their individual
morphology, cell walls structure, or the biochemical composition of individual species.
