A comparison of energy flow through the Dublin Bay and Baie de Somme intertidal ecosystems and their network analysis

Energy (biomass) and energy flows (production, inputs, transfers and losses) were calculated for eight and twelve compartment systems (phytoplankton, benthic primary producers (macroalgae, microphytobenthos), zooplankton, benthos (meiofauna, suspensivores, deposivores and predators), fish, birds and particulate organic matter (POM) in sediment and suspended particulate matter (SPM)) both balanced and unbalanced of Dublin Bay and the Baie de Somme. The resultant models were analysed with the Scientific Committee on Oceanic Research (SCOR) network analysis package. While the two systems share many properties such as the dominant biosedimentary facies, there are fundamental differences in both structuring and responses of the systems. The network analysis suggested that the Baie de Somme was far more productive, notably in terms of water column productivity, and was the more mature system. The high organic SPM input to Dublin Bay greatly elevated the degree of detritivory such that the analysis generated metrics indicative of a mature system but which rather reflected the degree of anthropogenic stress on the system. However, the analysis of both systems displayed varying degrees of maturity. Increasing the number of compartments greatly increased the calculated throughput (T) of the system and other associated metrics such as capacity (C), ascendancy (A) and redundancy (R). In the case of Dublin Bay, a higher number of compartments increased the various measures of system maturity, but this was much less marked for the Baie de Somme. Balancing the systems also increased T, C, A and R, and, to a lesser extent but not invariably, the system maturity metrics. The ratios of the comparative system metrics such as comparative ascendancy (A/C) were much less changed by the different methodologies and as such are recommended as robust measures for intercomparison of system performance.