JACK J. MIDDELBURG, KARLINE SOETAERT, PETER M. J. HERMAN, HENRICUS T.S. BOSCHKER AND CARLO H.R. HEIP BURIAL OF NUTRIENTS IN COASTAL SEDIMENTS: THE ROLE OF PRIMARY PRODUCERS 1. INTRODUCTION Anthropogenic nutrient inputs to aquatic systems exceed those under pristine conditions. This has resulted in numerous changes in their functioning of which eutrophication effects, the development of nuisance algal blooms, seasonal anoxia, the disappearance of seagrasses are illustrative, well-documented examples (Heip, 1995; Duarte, 1995). Concern about these changes in ecosystem functioning has initiated large amount of research on nutrient cycling with the ultimate aim to predict consequences of policy measures and management options. One of the basic tools used in the study of nutrient cycling in aquatic ecosystems is the construction of nutrient budgets. Nutrient budgets are very much alike financial bookkeeping systems with revenues and assets on one side and expenses and debts on the other side. Accountancy has developed into a mature discipline that is able to deal with internal and external losses and revenues and with disparate, not always accurate or quantifiable data. For instance, long-term depreciation costs have to be balanced against the expected enhanced profit of an investment. Biogeochemists and ecologists constructing nutrient budgets are faced with similar complexities. On the one hand there are event-like input terms such as atmospheric deposition of nutrients during rain that cover a period of a few hours at most and on the other hand there are long-term (years) loss terms such as the nutrient contained in accumulating sediments. For ecosystem budgets, it is important to distinguish between internal sinks (primary production and nutrient assimilation) and sources (remineralisation) and external (river) input and output terms (denitrification and burial). In this chapter we will address the burial term for nutrients in coastal sediment ecosystems. We will first provide a definition and then discuss the two main components (sediment accumulation and nutrient concentration). Special attention will be given to the influence of primary producers on nutrient burial via enhancement of sediment accumulation rates or via their effect on organic matter production or preservation. 2. BURIAL DEFINED The term burial is used within various subdisciplines with the consequences that it is used for different processes that operate on different time scales. Here we define burial as the longer-term removal (annual to decadal scale) of nutrients from the 217 © 2004 Kluwer Academic Publishers. Printed in the Netherlands. S. Nielsen, G. Banta and M. Pedersen (eds.), Estuarine Nutrient Cycling: The Influence of Primary Producers, 217-230.