Diatom biofilms: ecosystem engineering and niche construction

Ecology is complex and while there is a modern drive towards a holistic or “ecosystem approach” for managing marine systems, we are still a long way from fully understanding the interactions between the various components of different ecosystems and fully valuing their contributions. Microphytobenthos (MPB), and diatom biofilms, are an excellent example. While they are relatively widespread, their role has often been overlooked in favor of more charismatic species or assemblages. However, the understanding of their ecological importance has increased with a growing body of evidence outlining their important role in system functions ranging from biogeochemical cycles, trophic interactions and a direct influence of sediment dynamics. The latter effect is related to the secretion of extracellular polymeric substances (EPS) which have a number of roles in ecosystem dynamics, including the mediation of sediment erosion. Therefore, it is understandable that characterization of MPB assemblages as ecosystems engineers is becoming more widespread. A more recent development is the debate surrounding the evolutionary impact of ecosystem engineering and whether this is sufficiently distinct and important that it should be considered a separate evolutionary pressure, as described in the “niche construction” theory. Microphytobenthos have already been cited in this debate and this chapter briefly introduces the range of functionality of MPB and discusses their role as ecosystem engineers and their potential place in niche construction theory.