Regulation and maintenance ecosystem services in a coastal-marine continuum: Unravelling the underlying ecological structure and functioning

• Regulation and maintenance ES are fundamental for supporting the supply of other ES. • Network approach of the ES cascade framework at coastal and marine region. • Revealed direct and indirect importance of lower trophic levels in function provision. • Some functions lacked resistance, relying on few species; others involve diverse groups. • Holistic understanding aids in mitigating indirect pressures on marine ecosystems. Understanding the ecological complexity underlying ecosystem services supply is essential to improve the practical application of the ecosystem services concept, enhance stakeholder understanding, and support effective ecosystem-based management. This study applied a theoretical network-based overview of the ecosystem services cascade framework, linking the different ‘steps’, from the ecological structure and functioning to ecosystem services and societal goods and benefits. Combining ecosystem models, information from the literature, and empirical data, the robustness of the ecological sub-system ecological functions supply underpinning the supply of regulation and maintenance ecosystem services was analyzed, at a coastal-marine interface of the northern coast of Portugal. The findings highlight the intricate relationships within the system ecological components that contribute to regulation and maintenance ecosystem services supply. The analysis shows that lower trophic levels (e.g. algae and macroalgae, macrophytes, macrozoobenthos or suprabenthic invertebrates) are key to directly sustaining function supply and the consequent regulation and maintenance ecosystem services, and phytoplankton and zooplankton the most important groups in indirectly support the ecological functioning in the region. Some ecological functions revealed a potential lack of resistance and resilience due to being supplied by one or a few functional groups, while most functions were supplied by various biota groups. The findings emphasize the significance of considering the different biota group relationships in management practices. This holistic approach allows managers and regulators to navigate the complexities in marine and coastal ecological systems that support its functioning and the provision of regulation and maintenance ecosystem services, and thus the provision of the other types of services and hence societal goods and benefits, to mitigate potential unaccounted or indirect pressures on system components.