Foam production as a side effect of an offshore liquefied natural gas terminal: how do plankton deal with it?

The future growing demand of fossil fuels likely will lead to an increased deployment of liquefied natural gas terminals. However, some concerns exist about their possible effects on the marine environment and biota. Such plants showed to cause the production of foam, as occurred at the still operative terminal of Porto Viro (northern Adriatic Sea). Here, we present results from two microcosm experiments focused on the effects of such foam on microbially mediated degradation processes and its consequent incorporation within the pelagic food web. Such material could be considered as a heterogeneous matrix of both living and non-living organic matter, which constitutes an important substrate for exoenzymes as suggested by the faster hydrolytic rates measured in the treatment microcosms. In the second experiment, a quite immediate and efficient carbon transfer to planktonic biomass through prokaryotic incorporation and consequent predation by heterotrophic flagellates was highlighted. Although no negative effect was evidenced on the overall microbes' growth and foam-derived C seemed to be easily reworked and transferred to higher trophic levels, an important reduction in biodiversity was evidenced for microalgae. Among them, mixotrophic organisms seemed to be favoured suggesting that the addition of foam could cause a modification of the microbial community structure.