Effect of environmental conditions on variation in the sediment-water interface created by complex macrofaunal burrows on a tidal flat

We quantified the increase in the sediment-water interface created by the burrowing activities of the resident macrofaunal community and its variation with respect to the physical conditions of the habitat on a tidal fat. We investigated environmental factors and dimensions of macrofaunal burrows with respect to tidal height and vegetation during spring and summer at three sites. A resin-casting method was used to quantify the dimensions of all burrows at each site. The dimensions of macrofaunal burrows varied both temporally and spatially and the increase in the sediment-water interface reached a maximum of 311%, ranging from 20 to 255% under different habitat conditions. The sediment-water interface depended on the duration of exposure resulting from tidal height, increased temperatures resulting from seasonality, and marsh plant density. Burrows were deeper and more expansive at both higher tidal levels and higher temperatures in summer. Burrow dimensions were sharply reduced with the disappearance of adult macrofauna in areas where the roots of the marsh plant Suaeda japonica were dense. The significance of this study lies in quantifying the burrow dimensions of the entire macrofaunal community, rather than just a single population, and confirming their spatial and temporal variation with respect to physical conditions of the habitat. Environmental factors responsible for variation in burrow dimensions are discussed.     

The sediment-water interface increment due to the complex burrows of macrofauna in a tidal flat

The architecture of macrofaunal burrows and the total area of the sediment-water interface created by biogenic structure were investigated in the Donggeomdo tidal flat on the west coast of Korea. Resin casting methods were applied to recover burrows of four dominant species, Macrophthalmus japonicus, Cleistostoma dilatatum, Perinereis aibuhitensis, and Periserrula leucophryna, and whole burrows within the casting area at three sites in different tidal levels.P. leucophryna excavated the largest burrow in terms of a surface area among them. In the case of whole burrow casting, the space occupied by the biogenic structure was extended into deeper and expanded more greatly at the higher tidal level. In the uppermost flat, the burrow wall surface area within sediment was more extensive than the sediment surface area. Increased oxygen supply through the extended interface could enhance the degradation rates of organic carbon and also change the pathways of degradation. Quantifying the relationship between the extended interface and mineralization rate and pathway requires more extensive study.     

Oxygen penetration through invertebrate burrow walls in Korean tidal flat

Macrofaunal burrows increase the surface area of the sediment-water interface, which has a great impact on the metabolism of aerobic microbes and the oscillation of reduced metabolites within the sediment. Given the importance of macrofauna in surficial sediments, the aim of this study is to examine the effects of burrow architectures on dissolved oxygen diffusion rates in comparison with unburrowed sediment, and thereby to evaluate the theoretical assumption used for modeling solute distribution in the burrow system using field samples. Employing microsensors, horizontal oxygen profiles were measured on a micrometer scale around burrows of seven invertebrates in tidal flats of the west coast of Korea. Oxygen diffusion distance through the burrow walls of seven invertebrates showed spatio-temporal variation with a range of 0.6 to 2.9 mm. Two groups of burrows were identified based on their oxygen diffusive properties relative to unburrowed sediments: 1) oxygen penetration similar to that of ambient sediments and 2) clearly enhanced oxygen penetration. Differences in the diffusive properties of the burrow wall were related to the burrow depth and diameter, existence of mucus lining on the wall, sediment grain size, and tidal phases. Also inhabitant activity was an important factor affecting oxygen penetration, which is discussed in the paper. These results further demonstrate that simplified assumptions (i.e. burrow structures are viewed as direct biogeochemical extensions of the sediment-water interface) may not be exact representation of the nature.     

The tidal flushing of multiple-loop animal burrows

Tidal flushing of animal burrows in mangrove swamps provides an effective and important mechanism for transport of salt and other soluble substances. The burrows have complex morphologies consisting of multiple loops. Using established computational modelling techniques, burrow geometries were simulated from characteristic burrow dimensions and the effect of multiple loops on flushing is studied. The computational models show that flushing is enhanced in multiple-loop burrows as upper loops can be completely evacuated, increasing the volume of burrow water removed. The models indicate that there may be a depth limit to which flushing occurs in complex burrow structures. Periscope loops extend further than one characteristic loop depth and are shown to affect the flushing of burrows if the surface-water plume penetrates to their lower depth. Periscope loops with surface openings on the downstream side of the burrow, relative to the tidal inundation, most frequently experience this condition and thus have a great impact on burrow flushing. Field measurements of salinity agree with the hypothesis that there is a depth limit of flushing for complex burrows that is independent of burrow salinity, and suggest a value of 30–35 cm. The measurements also support the suggestion that significant flushing of burrows occurs within a single tidal event. An experiment considered the movement of animals across the interface created by low-salinity surface water and high-salinity burrow water after a partial flushing event. The motion enhances the effective diffusion coefficient of salt by a factor of at least 10², as compared with free diffusion of salt in water, resulting in a more even distribution of dissolved salt in the burrow water between tidal inundations. This distribution may lead to an increase in the depth to which flushing occurs during subsequent inundations.     

Novel mechanism of stream formation in coastal wetlands by crab–fish–groundwater interaction

A novel mechanism of stream development in coastal wetlands was observed in the form of interaction between the burrowing crab (Chasmagnathus granulata) and groundwater seepage. This process may eventually be further promoted by the predatory action of the white croaker fish (Micropogon opercularis). These so-called crab streams occur on the banks of major tidal channels in a salt marsh of the Bahía Blanca Estuary (Argentina). As the tide recedes, water is retained in the crab burrows on the marsh surface. The presence of lateral burrows produced by crab recruits promotes subterranean piping flow driven by the hydraulic head in the vertical burrow. Groundwater generally seeps along the tidal channel banks but is particularly prominent and concentrated where crab burrows perforate the banks. Where predatory attacks by the croaker fish enlarge the burrow mouths, the drainage rills become wider and deeper because more seeping water is collected in the shallow crater from where it is funnelled into the developing streams. The crab stream is then produced by water draining from the crab burrow mouth, acting initially by cut-back erosion and followed by forward erosion of the relatively unconsolidated muddy sediments.     

米草属植物Spartina angilica和Spartina alterniflora引种后江苏海岸湿地生态演化的初步探讨

选取江苏王港潮滩的盐蒿滩、大米草滩及互花米草滩,分析这三类滩面的地面以上生物量、初级生产力、动物洞穴参数和沉积物粒度,探讨大米草和互花米草引种区的湿地生态系统相对于盐蒿滩的变化.分析结果表明,互花米草滩的生物量远大于盐蒿滩和大米草滩;单位面积上动物洞穴数量相近,但洞穴大小有一定差异,互花米草滩动物洞穴稍大,数量也相对较多,这可能与初级生产力的提高有关.表层底质的粒径以互花米草滩为最细,盐蒿滩最粗,这种分布状况与互花米草引种前不同,说明互花米草促进了细颗粒物质的堆积.互花米草的引种在江苏海岸具有促淤和提高初级生产力的作用,而它对湿地生态系统的结构和功能的影响需要进一步研究.     

Colonization, succession, and nutrition of macrobenthic assemblages in a restored wetland at Tijuana Estuary, California

Modes of colonization, the successional trajectory, and trophic recovery of a macrofaunal community were analyzed over 19 months in the Friendship marsh, a 20-acre restored wetland in Tijuana Estuary, California. Traditional techniques for quantifying macrofaunal communities were combined with emerging stable isotopic approaches for evaluation of trophic recovery, making comparisons with a nearby natural Spartina foliosa habitat. Life history-based predictions successfully identified major colonization modes, although most taxa employed a variety of tactics for colonizing the restored marsh. The presence of S. foliosa did not seem to affect macrofaunal colonization or succession at the scale of this study. However, soil organic matter content in the restored marsh was positively correlated with insect densities, and high initial salinities may have limited the success of early colonists. Total macrofaunal densities recovered to natural marsh levels after 14 months and diversity, measured as species richness and the Shannon index (H′), was comparable to the natural marsh by 19 months. Some compositional disparities between the natural and created communities persisted after 19 months, including lower percentages of surface-feeding polychaetes (Polydora spp.) and higher percentages of dipteran insects and turbellarians in the Friendship marsh. As surficial structural similarity of infaunal communities between the Friendship and natural habitat was achieved, isotopic analyses revealed a simultaneous trajectory towards recovery of trophic structure. Enriched δ¹³C signatures of benthic microalgae and infauna, observed in the restored marsh shortly after establishment compared to natural Spartina habitat, recovered after 19 months. However, the depletion in δ¹⁵N signatures of macrofauna in the Friendship marsh indicated consumption of microalgae, particularly nitrogen-fixing cyanobacteria, while macroalgae and Spartina made a larger contribution to macrofaunal diets in the natural habitat. Future successional studies must continue to develop and employ novel combinations of techniques for evaluating structural and functional recovery of disturbed and created habitats.     

Methods for monitoring tidal flushing in large animal burrows in tropical mangrove swamps

The typically anaerobic nature of mangrove sediments provides significant challenges to the mangrove trees and biota inhabiting them. The burrowing activities and flow of water through the numerous and complex animal burrows perforating the sediments of mangroves have a major influence on the biogeochemistry of the sediments and are important to the enhancement of nutrient and oxygen exchange. Two new methods are presented for monitoring the tidal flushing of Sesarma messa and Alpheus cf macklay burrows in a Rhizophora stylosa mangrove forest – by measuring oxygen content of burrow water and by determining the change in fluorescence of a dye tracer through tidal inundation. A case study using the first of these showed oxygen consumption rates at the burrow wall deep within the burrow were found to be between 210 and 460 μmol O₂ m⁻² h⁻¹. The influx of oxygen during a flood tide was found to be significant and indicated that approximately 40% of the burrow water is flushed during a single tidal event. However, the high consumption rate of oxygen within the burrow resulted in the oxygen concentration remaining at or below one-third of the oxygen content of the flooding tidal water. A test application of the second method, using rhodamine dye as a tracer, indicated that the exchange of water between the burrow and the flooding tide was found to be in the order of 30% of the burrow volume. These new techniques provide a means to further study the nutrient exchange within these burrow systems and verify the initial findings that several tidal inundations are necessary to completely flush the burrows.     

Variation in groundwater salinity in a tidal salt marsh basin,North Inlet Estuary,South Carolina

Groundwater flow of freshwater from upland forests into salt marshes is influenced by hydrologic forces that operate over a wide range of temporal scales, including storm events, tidal fluctuations, seasonal variations in rainfall and evapotranspiration (ET). Groundwater salinity can be a useful first order indicator of the balance between these flow processes. A dipole-dipole electrical resistivity survey was conducted approximately monthly during 2005 to measure groundwater salinity across a portion of Crabhaul Creek, a tidal salt marsh basin at the boundary of the upland forest and the North Inlet marsh in South Carolina. The monthly electrical resistivity surveys were designed to provide a detailed, spatially continuous measurement of subsurface conductivity to a depth of 4 m in order to further investigate the seasonal variation in groundwater salinity. Resistivity models were corroborated by simultaneous measurements of salinity in nearby piezometers. The freshwater-brackish water interface was clearly imaged by the resistivity. Movement of this interface occurs on a timescale of months rather than a regular seasonal variation. The average salinity in the marsh basin is highest in late Summer (July–August) when ET is highest, and lowest during the Winter (November–December). The position of the brackish-freshwater interface changes, but is not well correlated to local rainfall or tidal cycles except under specific circumstances. A steady-state hydrological model correctly predicts the average position of the freshwater-brackish interface and suggests a linear relationship between the height of the water table and the location of the interface. These results suggest a complex relationship between precipitation events and groundwater flow from the forest into the marsh.     

Sediment dynamics modulated by burrowing crab activities in contrasting SW Atlantic intertidal habitats

Biogenic bottom features, animal burrows and biological activities interact with the hydrodynamics of the sediment–water interface to produce altered patterns of sediment erosion, transport and deposition which have consequences for large-scale geomorphologic features. It has been suggested that depending on the hydrodynamic status of the habitat, the biological activity on the bottom may have a variety of effects. In some cases, different bioturbation activities by the same organism can result in different consequences. The burrowing crab Neohelice granulata is the most important bioturbator at SW Atlantic saltmarshes and tidal plains. Because of the great variety of habitats that this species may inhabit, it is possible to compare its bioturbation effects between zones dominated by different hydrodynamic conditions. Internal marsh microhabitats, tidal creeks bottoms and basins, and open mudflats were selected as contrasting zones for the comparison on a large saltmarsh at Bahía Blanca Estuary (Argentina). Crab burrows act as passive traps of sediment in all zones, because their entrances remain open during inundation periods at high tide. Mounds are generated when crabs remove sediments from the burrows to the surface and become distinctive features in all the zones. Two different mechanisms of sediment transport utilizing mounds as sediment sources were registered. In the first one, parts of fresh mound sediments were transported when exposed to water flow during flooding and ebbing tide, with higher mound erosion where currents were higher as compared to internal marsh habitats and open mudflats. In the second mechanism, mounds exposed to atmospheric influence during low tide became desiccated and cracked forming ellipsoidal blocks, which were then transported by currents in zones of intense water flow in the saltmarsh edge. Sedimentary dynamics varied between zones; crabs were promoting trapping of sediments in the internal saltmarsh (380 g m⁻² day⁻¹) and open mudflats (1.2 kg m⁻² day⁻¹), but were enhancing sediment removal in the saltmarsh edge (between 10 and 500 g m⁻² day⁻¹ in summer). The implication is that biologically mediated sedimentological changes could be different among microhabitats, potentially leading to contrasting geomorphologic effects within a particular ecosystem.     

The Biology of Upogebia pusilla (Petagna) (Decapoda, Thalassinidea) I. The Burrows

Abstract. The biology of the thalassinidean shrimp Upogebia pusilla was studied on a tidal flat in the Lagoon of Grado (Northern Adriatic). Burrows were investigated using in situ resin casting and with additional in situ and laboratory observations. Burrows show a basic pattern consisting of a U or a double U with turning chambers and a vertical shaft. Mean burrow diameter depends on animal size, it is smaller than the rigid carapace of the animal. Dimensions, distance between openings, depth of U, total depth, volume and surface are size dependent. The burrow wall is smooth and oxidized. Burrows are always inhabited by a single shrimp. Although they overlap, they are never interconnected. They are mainly constructed by compression of the sediment and are relatively permanent structures. A comparison of the burrows of Thalassinidea with regard to shape, number and appearance of openings, dimensions, properties of the burrow wall and dynamics is given.     

Salt marsh pore water geochemistry does not correlate with microbial community structure

Spatial and temporal trends in pore water geochemistry and sediment microbial community structure are compared at three intertidal sites of a saltmarsh on Sapelo Island, GA. The sites include a heavily bioturbated, unvegetated creek bank, a levee with dense growth of Spartina alterniflora, and a more sparsely vegetated ponded marsh site. The redox chemistry of the pore waters ranges from sulfide-dominated at the ponded marsh site to suboxic at the creek bank site. At the three sites, the vertical redox stratification of the pore waters is more compressed in summer than in winter. The trends in redox chemistry reflect opposing effects of sediment respiration and pore water irrigation. Intense and deep burrowing activity by fiddler crabs at the creek bank site results in the efficient oxidation of reduced byproducts of microbial metabolism and, hence, the persistence of suboxic conditions to depths of 50 cm below the sediment surface. Increased supply of labile organic substrates at the vegetated sites promotes microbial degradation processes, leading to sharper redox gradients. At the levee site, this is partly offset by the higher density and deeper penetration of roots and macrofaunal burrows. Surprisingly, the microbial community structure shows little correlation with the variable vertical redox zonation of the pore waters across the saltmarsh. At the three sites, the highest population densities of aerobic microorganisms, iron- plus manganese-reducing bacteria, and sulfate reducers coexist within the upper 10 cm of sediment. The absence of a clear vertical separation of these microorganisms is ascribed to the high supply of labile organic matter and intense mixing of the topmost sediment via bioturbation.     

台风作用下的港湾型潮滩沉积过程 以2008年“凤凰”台风对福建省罗源湾的影响为例

通过对"凤凰"台风的现场观测和沉积物样品的分析,结果表明,在台风影响下潮水淹没时间增长,增水达1.1 m;台风期间互花米草盐沼内流速变化较复杂,而且盐沼内部流速大于盐沼边缘的;台风期间盐沼边缘潮周期平均悬沙含量是台风前2 d的7倍;台风期间十分之一波高最大为1.54 m。滩面重复测量结果显示,台风登陆期间整个光滩滩面都发生了侵蚀,盐沼内部有部分地区发生侵蚀,侵蚀深度为4.5~5.5 cm,盐沼边缘的侵蚀深度仅为0.7 cm,侵蚀原因主要是植被在风浪作用下从根部折断,从而带走了滩面的沉积物;随着台风强度的减弱,整个滩面均接受悬沙沉降;台风带来的强降雨是影响滩面沉积物活动的重要因素。     

Intertidal mangrove boundary zones as nursery grounds for the mud crab Scylla serrata

The demand for mud crab Scylla serrata (Forsskål 1775) in the global market has increased, hence there is growing momentum to farm the species in Africa. Aquaculture production in Kenya and elsewhere in East Africa currently relies on juvenile seeds sourced from the wild. Wild-seed collection calls for management of the juvenile crab industry founded on knowledge of the species’ ecology, so as to achieve a sustainable seed supply and recruitment to the capture fishery. This study investigated the tidal, diurnal and seasonal occurrence of juvenile crabs in three habitats (intertidal-flat boundary zones, inside the mangroves, and in channels) in small creeks (Mida, Kilifi and Mtwapa) and Gazi Bay, on the coast of Kenya. Sampling was done with scoop nets and seining at receding tides and via burrow searches at low spring tides (day and night). Juveniles in the mangrove/intertidal-flat boundary zone were found sheltered under mangrove leaves or debris, or in shallow burrows during low spring tides, whereas at receding tides they could be seen moving out with the tide or searching for sheltering substrate or burrows. Catch per unit effort at high-abundance sites varied between 59 and 68 crabs fisher^?1 day^?1. More juvenile crabs, sized 10–80 mm internal carapace width (ICW), occurred at night during the receding tide. Net-seining was effective in the collection of juvenile mud crabs <30 mm ICW, whereas burrow sampling was effective for gathering larger crabs. However, collection of juveniles by seining reduced the quality of the crabs caught due to frequent loss of chelipeds, as compared with retrieving individual crabs by searching burrows. Some juveniles collected in the intertidal-flat boundary-zone habitat were either in the process of moulting or had just moulted, indicating the significance of this habitat for mud crabs at this physically delicate life stage.     

汕头3种人工红树林湿地大型底栖动物群落的比较

对广东省汕头市莲阳河口区恢复背景相同的拉关木(Laguncularia racemosa)、无瓣海桑(Sonneratia apetala)、海桑(Sonneratia caseolaris)3种人工林和光滩湿地中大型底栖动物群落进行比较研究。结果显示,4种生境中大型底栖动物优势种(Y0.02)存在差异;相似性分析检验(One-Way ANOSIM)表明4种生境间大型底栖动物群落结构差异显著。等级聚类和非参数多变量标序也显示4种生境间的大型底栖动物群落结构差异显著。3种人工林中,无瓣海桑、海桑人工林中大型底栖动物群落结构较为相似;3种人工林中大型底栖动物物种多样性和生物量从大到小的排列次序为:拉关木海桑无瓣海桑。BIOENV分析表明大型底栖动物分布与林地土壤p H、有机质、砂粒和粉粒含量、红树植物平均株高、平均胸径、平均基径和冠幅(南北×东西)这些理化因子显著相关,这进一步证实了红树植物种类对林地大型底栖动物多样性和分布的影响。     

Reproductive ecology of the mudskipper Boleophthalmus pectinirostris

The reproductive ecology of the mudskipper Boleophthalmus pectinirostris was investigated during the spawning season in the Funing Bay, Fujian, China. The fish burrows were basically Y-shaped and had two openings onto the mudflats. Part of the intersection at the center of the burrow was dilated to form a "spawning chamber". The dissolved oxygen concentrations (0.40~0.65 mg/dm3)of water 15 cm deep inside the burrows were much lower than those (5.96~6.19 mg/dm3) of intertidal pool water. Water temperatures inside the burrows were much lower than those of intertidal pools. Field investigations indicated that eggs were laid on the inner wall and ceiling of the spawning chamber by means of filamentous attachments, and a male stayed inside the burrows to guard it. Field investigations also suggested that fish of both sexes constructed mud burrows by themselves but that the spawning chamber was made only in the male burrow. The male attracted a female to his burrow for mating and spawning. There was no water in the spawning chamber, and thus the eggs were exposed to the air in the chamber. Changes in spawning readiness and gonadosomatic index indicated that synchronization of spawning was related to the semi-lunar periodicity, and this is the first report of this relationship in the mudskippers.     

崇明岛南侧盐沼潮滩消能状态研究

沿海盐沼潮滩可以有效降低波浪高度,耗散波浪能量,在海岸防护和沿海城市安全中扮演着重要角色。以长江河口崇明岛南侧盐沼潮滩为对象,基于不同潮间带实测波浪变化数据,采用波能衰减模型对波浪横向沿潮滩衰减状态进行定量分析,由此探讨波浪衰减主控要素。结果表明:波浪沿盐沼潮滩向岸传播过程中,波高以及波能大幅下降,其中光滩—芦苇前部区域波能平均下降19%,芦苇区域波能平均下降71%,有植被覆盖区域对波浪的衰减效应更为显著。同时,水深、入射波高及阻力是影响盐沼潮滩波浪衰减的主要因素,波浪衰减强度随水深增大而减小,入射波高增加以及阻力的增大而增强。     

Patterns of unsuccessful shell-crushing predation along a tidal gradient in two geographically separated salt marshes

Gradients in salt marsh ecosystems that result from reduced tidal inundation time in the high marsh offer an opportunity to assess the importance of predation as a selective agent (indexed by the time-averaged record of unsuccessful predation, which integrates potentially confounding short-term – inter-seasonal and inter-annual – fluctuations in predation pressure). Spatial patterns in selection pressure are expected to decrease landward from the seaward edge of the marsh. Interaction between shell-breaking predators and their snail prey, Littoraria irrorata, however, generated a pattern in the frequency of sublethal injury (shell repair), standardized for snail size, that did not follow this simple, single-variable prediction of decreasing repair frequencies with distance from the seaward edge of the marsh, based on inundation time alone. Patterns of repair frequency increased landward from the seaward edge of the marsh, only declining as predicted after a zone of dense stands of salt marsh grass. The interaction of tidal inundation time and primary habitat structure ( e.g. physical vegetative barriers to dispersion of predators into the marsh) is hypothesized to shape selection gradients in salt marshes, as inferred from the record of unsuccessful predation.     

泉州湾洛阳江口2种红树林生境大型底栖动物群落多样性比较

为探讨泉州湾洛阳江口桐花树和秋茄2种红树林生境的大型底栖动物群落是否存在明显差异,于2011年4月至2012年1月对2种红树林生境的大型底栖动物进行了季度定量调查.结果表明：4个季度在2种红树林生境定量取样获得大型底栖动物49种,其中多毛类15种,腹足类8种,甲壳类15种,鱼类3种,昆虫2种,刺胞动物、扁形动物、纽形动物、星虫动物、寡毛类和双壳类各1种.寡鳃齿吻沙蚕（Nephtys oligobranchia）、短拟沼螺（Assiminea brevicula）、弧边招潮蟹（Uca arcuata）、指海葵（Actinia sp.）等在2种生境均有较高的栖息密度,可口革囊星虫（Phascolosoma esculenta）是2种生境的常见种,但栖息密度不高.虽然秋茄生境的大型底栖动物平均生物量高于桐花树生境,但桐花树生境的大型底栖动物群落的物种数、栖息密度、多样性指数（H’）、均匀度指数（J）和丰富度指数（d）均高于秋茄生境.单变量双因素方差分析（Two-way ANOVA）表明,2种红树林生境的大型底栖动物群落的多样性指数和均匀度指数有显著的季节差异、生境差异以及生境×季节差异.聚类分析表明,2种红树林生境的大型底栖动物群落组成的相似性较高,其原因是它们所处的潮区相同、沉积物类型相似和底质粒径相近.     

Tidal exchange of nitrogen and phosphorus between a mesohaline vegetated marsh and the surrounding estuary in the lower Chesapeake Bay

A 22-month study was conducted to determine the exchange of nitrogen and phosphorus between a mesohaline vegetated marsh in the Carter's Creek area of Virginia and the surrounding estuary, focusing on the role of the vegetated marsh surface in the processing of these constituents. On an annual basis there was a removal of $\text{NH}{}_4{}^{\mathrm{+}}$, $\text{PO}{}_4{}^{\mathrm{3?}}$, $\text{NO}{}_3{}^{\mathrm{?}}$, dissolved organic nitrogen, dissolved organic phosphorus, particulate nitrogen and particulate phosphorus from the tidal water as it resided on the vegetated marsh. Only nitrite was transported from the marsh to the estuary. Most of the nitrogen and phosphorus species showed distinct seasonal trends with respect to the direction of transport except nitrate and orthophosphate. The ammonium flux data indicates that this nutrient was removed from the inundating water during late spring and fall, with a slight release of this constituent into the tidal water during the late summer. The transport of nitrite was from the estuary to the marsh for most of the year except during the fall. The large release of this nutrient into the tidal water at this time is associated with the senescence of the marsh vegetation. There was a large removal of DON from the tidal water during the fall, while the flux of DOP was from the estuary to the marsh for most of the year except during the summer. The largest removal of particulate nitrogen and phosphorus from the tidal water occurred during the summer months when the turbidity of the tidal water was highest, especially when wave scouring of the mudflats brings material into the water column. A loss of particulate nitrogen from the marsh to the estuary was evident during the fall and winter.