Advances in our understanding of pelagic-benthic coupling

We synthesized our present understanding of pelagic-benthic (P-B) interactions in the northern Adriatic Sea (NAS) and Chesapeake Bay (CB) in a comparative analysis that builds on a prior comparison. We focus on primary production (PP) in the water column and benthos, the sedimentation and horizontal transport of particlulate organic matter (POM), and biogeochemical responses of the benthic community to sedimentation. Phytoplankton net PP (NPP) remains higher in CB (five times that in NAS) and rates of benthic respiration appear greater in CB (three times that in NAS). A lower fraction of phytoplankton NPP plus riverine inputs of POM is deposited to sediments in the NAS (23%) compared to CB (83%). A high percentage of organic matter inputs are respired by plankton and exported in the NAS and CB, and benthic communities respired a similar percentage of POM (86% in the NAS, 92% in CB). Net release of regenerated N from the benthos (0.2-0.3 mol N m-2 year-1) is also similar in both systems. At 0.53 mol N m-2 year-1, rates of benthic denitrification are higher in CB than in the NAS (0.3 mol N m-2 year-1), and the NAS appears to bury similar fractions of deposited N and P (N: 23% in NAS, 19% in CB; P: 50% in NAS, 45% in CB). To address the impacts of future climatedriven warming and acceleration of the water cycle, we recommend a return to sustained monitoring combined with numerical simulations to allow improved understanding and predictions of changes in P-B interactions.