-1 Solute dynamics in a North Brazilian mangrove: the influence of sediment permeability and freshwater input Luitgard Schwendenmann 1, *, Rainer Riecke 2 and Rube´n J. Lara 3 1 Tropical Silviculture, Institute of Silviculture, University of Goettingen, Buesgenweg 1, D-37077, Goettingen, Germany; 2 BARD Engineering GmbH, Domshof 21, D-28195, Bremen, Germany; 3 Center for Tropical Marine Ecology, Fahrenheitstr. 6, D-28359, Bremen, Germany; *Author for correspondence (e-mail: lschwen@gwdg.de; fax: +49-551-394019) Received 9 May 2005; accepted in revised form 16 January 2006 Key words: Adsorption, DOC, DON, Phosphate, Rainfall, Salinity, Transport, Wetland Abstract Although water in mangrove sediments influences nutrient cycling in both, mangrove forest and estuary, little information exists on seasonal and vertical distribution of dissolved organic and inorganic compounds in the sediment column. We studied the influence of sediment texture and chemistry, permeability (K), tides, and rainfall on dissolved organic carbon (DOC) and nitrogen (DON), dissolved inorganic phosphate (DIP) and salinity in creek and sediment waters of a mangrove in Para´ , Brazil. Water samples were taken from boreholes and piezometers in the mangrove forest and from an adjacent tidal creek at neap and spring tides, during the dry and rainy season. Forest sediment was analysed for carbon (C), nitrogen (N), salinity and permeability. Clay, C and N decreased with depth. Sediment permeability (K) was lowest (<0.1 m day 1 ) in the upper, clay- rich and crab-burrow-free mud layer. In the deeper, fine sand strata, K ranged from 0.7 to 1.8 m day 1 . Tidal range in the creek was 3.5 and 5.5 m for neap and spring tides, respectively. Salinity, DOC, DON and DIP in creek water were inversely related to tidal height. Piezometer data revealed significant water level changes in deeper, sandy sediment layer, which followed, time-lagged, the tidal fluctuations. In contrast, tide did not affect the water level in the upper sediment due to low permeability. Compared with creek water, sediment water was enriched in DOC, DON and DIP because of organic matter input and mineralization. In deeper layers, solute concentration was most likely affected by sorption processes (DOC and DIP) and reduction reactions (DIP). During the rainy season, DOC and DON in creek and sediment water were higher than in the dry season. DIP appeared invariant to seasonal changes. In the rainy season, salt flushing from surface sediments resulted in higher salinities at intermediate sediment depths, while in the deeper layers salinity was lower due to exchange with water from the tidal creek. Introduction Mangroves are highly productive systems and the export of organic and inorganic nutrients from these forests can considerably affect the biogeo- chemical cycles of coastal regions (Alongi et al. 1989; Rivera-Monroy et al. 1995). Although a number of studies have been undertaken, differ- ences in inherent ecosystem characteristics and methodological aspects do not allow generalized conclusions to be drawn regarding the extent and pathways of material import or export in man- grove forests (Alongi et al. 1989; Dittmar and Lara 2001a). The amount and composition of organic and inorganic compounds in wetland sediments are influenced by inundation regime, rates of sediment accumulation, bioturbation, primary productivity, Wetlands Ecology and Management (2006) 14:463–475 Ó Springer 2006 DOI 10.1007/s11273-006-0008-1