Experimental setup
All meta-ecosystems consisted of a heterotrophic and an autotrophic
patch (ecosystem), respectively. The heterotrophic ecosystems consisted
of a community of nine, mostly heterotrophic ciliates
(Blepharisma sp., Colpidium sp., Euplotes
aediculatus , Loxocephalus sp., Paramecium aurelia ,Paramecium caudatum , Spirostomum sp., Spirostomum
teres , and Tetrahymena cf. pyriformis) , and one rotifer
(Cephalodella sp.). The autotrophic ecosystem consisted of a
photosynthesising mixotrophic flagellate (Euglena gracilis ). We
subsequently refer to all these organisms as “protists”. Before the
experiment, the protists were individually cultured in pre-autoclaved
bottles with protist medium (0.46 g of Protozoa Pellet by Carolina per L
of water) and bacteria (Serratia fonticola , Bacillus
subtilis , and Brevibacillus brevis ) acting as food for protists
and constituting 5 % of the total volume of the culture. See Altermatt
et al. (2015) for further details and protocols.
At the beginning of the experiment (day zero), we prepared two large
bottles either containing E. gracilis or the mix of the 10
heterotrophic protists (the latter at 1/10 of their carrying capacity).
From these large bottles, we prepared 60 cell flasks (40 mL volume) with
different culture volumes—20 flasks of small ecosystem size (7.5 mL),
medium ecosystem size (22.5 mL), and large patch size (37.5 mL) (3 sizes
x 2 trophic types x 2 connection treatments x 5 replicates = 60 flasks).
Subsequently, the position of the cultures was randomised within an
incubator, maintained at a constant temperature of 20 °C with continuous
illumination.