The role of microphytobenthos in soft-sediment ecological networks and their contribution to the delivery of multiple ecosystem services

Sediment dwelling, microscopic primary producers, that occupy sediments in the photic zone, are commonly referred to as microphytobenthos (MPB). The MPB are essential components of soft-sediment systems, but are often overlooked when assessing coastal ecosystem functionality and service delivery. The MPB are involved in several complex interactions and feedback that underpin the delivery of vital ecosystem services. MPB profoundly influence the flow and cycling of carbon and nutrients, such as nitrogen, directly and indirectly underpinning highly productive shallow water marine food webs. The MPB can also stabilize sediments through the formation of biofilms, and significantly improve water quality by mediating the benthic-pelagic coupling of nutrients, sediment and pollutants. The functional role of the MPB is compromised by increasing anthropogenic pressures such as nutrient enrichment, sedimentation, herbicides and emerging contaminants such as microplastic pollution. However, MPB are extremely good at buffering the effects of these land-sourced stressors at the interface between land and sea. Synthesis. Society often appreciates the final provisioning of goods and services from our coastal marine environments. However, provisioning services are only possible due to the multitude of supporting and regulating services that underpin them. Microphytobenthos (MPB) are central to benthic ecological networks, and contribute to ecosystem service delivery through various pathways. Understanding the critical role of MPB in complex networks is therefore essential to appreciate their importance in ecosystem function and service delivery into the future.