Deep-Sea Macrobenthic Communities at Contrasting Sites off Portugal,Preliminary Results: I Introduction and Diversity Comparisons

Species diversity, faunal composition and abundance in the deep-sea macrobenthos are investigated at two, adjoining deep-sea areas off Portugal experiencing contrasting hydrodynamic conditions in order to test for the importance of disturbance in structuring the community. The first was located at 5,035 m depth on a presumably low current-energy site on the Tagus Abyssal Plain (TAP) and the second was centered in the lower end of the Setubal Canyon (SC) at 3,400 m depth where high levels of hydrodynamic activity are inferred from ripple bedforms visible in sea bed photographs. Closely grouped, transponder-mapped, “vegematic” box core samples were taken at each site. Agglutinated foraminifers numerically dominate the macrofauna (retained by 300 μm sieve) at both sites. Seagrass content in the SC cores indicates downslope detrital input from shallow water which is absent in the TAP samples. This must contribute, possibly with high levels of resuspended particles in near-bed flow, to the almost tenfold difference in abundance of metazoan macrofauna at the two sites. Expected species diversity measured from rarefaction is highest at TAP, both for pooled data and when foraminifers. tanaids and bivalve are considered separately. Evenness (equitability) in species' abundances is also higher at TAP than at SC. These differences are compared with benthic community data from the hydrodynamically disturbed High Energy Benthic Boundary Layer (HEBBLE) site on the Nova Scotia continental rise, and from the Rockall Trough (N.E. Atlantic). In common with these sites, strong bed flow at SC is thought to result in relatively high abundances, lower species richness and greater unevenness by acting to periodically disturb and reduce populations. Differences in the degree to which different faunal groups seem to be affected might be related to differences in lifestyle, particularly burrowing depth.     

Small-scale heterogeneity in deep-sea nematode communities around biogenic structures

The unexpected high species richness of deep-sea sediments gives rise to the questions, which processes produce and maintain diversity in the deep sea, and at what spatial scales do these processes operate? The idea of a small-scale habitat structure at the deep-sea floor provides the background for this study. At small scales biogenic structures create a heterogeneous environment that influences the structure of the surrounding communities and the dynamics of the meiobenthic populations. As an example for biogenic structures, small deep-sea sponges (Tentorium semisuberites Schmidt 1870) and their sedimentary environment were investigated for small-scale distribution patterns of benthic deep-sea nematodes. Sampling was carried out with the remotely operated vehicle Victor 6000 at the Arctic deep-sea observatory HAUSGARTEN. In order to investigate nematode community patterns sediment cores around three small sponges and corresponding control cores were analysed. A total of approx. 5800 nematodes were identified. The comparison of the nematode communities from sponge and control samples indicated an influence of the biogenic structure “sponge” on diversity patterns and habitat heterogeneity. The increased number of nematode species and functional groups found in the sediments around the sponges suggest that on a small scale the sponge acts as a gradient and creates a more divers habitat structure. The nematode community from the sponge sediments shows a greater taxonomic variance and species richness together with lower relative abundances of the species compared to those from control sediments. Obviously, the more homogeneous habitat conditions of the control sediments offer less micro-habitats than the sediments around the sponges. This seems to reduce the number of functional groups and species coexisting in the control sediments.     

Marine subsurface eukaryotes: the fungal majority

Studies on the microbial communities of deep subsurface sediments have indicated the presence of Bacteria and Archaea throughout the sediment column. Microbial eukaryotes could also be present in deep-sea subsurface sediments; either bacterivorous protists or eukaryotes capable of assimilating buried organic carbon. DNA- and RNA-based clone library analyses are used here to examine the microbial eukaryotic diversity and identify the potentially active members in deep-sea sediment cores of the Peru Margin and the Peru Trench. We compared surface communities with those much deeper in the same cores, and compared cores from different sites. Fungal sequences were most often recovered from both DNA- and RNA-based clone libraries, with variable overall abundances of different sequence types and different dominant clone types in the RNA-based and the DNA-based libraries. Surficial sediment communities were different from each other and from the deep subsurface samples. Some fungal sequences represented potentially novel organisms as well as ones with a cosmopolitan distribution in terrestrial, fresh and salt water environments. Our results indicate that fungi are the most consistently detected eukaryotes in the marine sedimentary subsurface; further, some species may be specifically adapted to the deep subsurface and may play important roles in the utilization and recycling of nutrients.     

Effects of oil/gas field produced water on the macrobenthic community in a small gradient estuary

Little is known about how climatic events (i.e., drought) inhibit or enhance movement of petroleum hydrocarbon laden sediments in estuarine systems and how this in turn effects the macrobenthic populations exposed to these sediments. Seventeen collection stations were established and monitored at New Bayou, Texas, a small gradient estuary which receives petroleum products via oil/gas field produced water discharge. Hydrographic, geologic and biotic samples were taken monthly from each station during a period of reduced rainfall. Both temperature and dissolved oxygen data taken during the study followed patterns typical for the area. Salinity values increased into the polyhaline range at near-bay stations during the reduced rain period, while upper bayou stations remained within the oligohaline range. Sediment grain sizes along the bayou were generally in the silty-clay range. Sediment hydrocarbon concentrations were highest (11.4 mg g⁻¹ dry sediment) around the produced water discharge site and lowest at near-bay stations (0.2 mg g⁻¹ dry sediment). Ninety-six macrobenthic species were collected during the study. General effects from produced water discharge on macrobenthic populations followed the classical pattern outlined by other research in shallow bay systems. A sediment hydrocarbon concentration of 2.5 mg g⁻¹ dry sediment was found to reflect the average value needed to depress population abundances. Both abundance and diversity values were lowest at central stations near the discharge site. This zone of depressed macrobenthic populations extended from the discharge site at least 107 m downstream and 46 m upstream. The zone of stimulated macrobenthic populations occurred 1486 m downstream and 381 m upstream from the discharge site.     

Long-term trends of subtidal macrobenthos in North Inlet,South Carolina

Analyses of seasonal and yearly trends in subtidal macrobenthic samples collected bi-weekly at a sandy site (1981–1984) and a muddy site (1981–1985) in North Inlet, South Carolina, show large fluctations in abundance and high variability between replicate samples. Sampling variability at the sandy site, thought to be influenced more by physical disturbance than by biotic interactions, was especially high and prevented the interpretation of seasonal trends in abundance. Increased replication at the muddy site in 1985 revealed abundance patterns of winter/spring maxima and summer minima. Despite short-term (seasonal) and high year-to-year variability, the fauna at both sites were characterized by long-term stability in abundance. That is, although abundances varied considerably between seasons or years only 9 of 22 taxa analyzed showed a directional change in abundance. These 9 taxa increased in abundance over the four (sandy site) or five (muddy site) years of examination while the other 13 taxa fluctuated about a mean value. The taxonomic composition of benthic fauna at both sites was also very stable through time, with the sandy site always numerically dominated, in order, by polychaetes, amphipods, and bivalves and the muddy site by polychaetes, oligochaetes, and bivalves.     

Macrobenthic prey availability and the potential for food competition between 0 year group Pleuronectes platessa and Limanda limanda

This study describes the feeding habits of plaice Pleuronectes platessa and dab Limanda limanda during early juvenile development and relates differences between nursery grounds and sampling years to spatial and temporal variabilities in macrobenthic prey availability. The main prey taxa of both species were copepods, bivalves, amphipods, polychaetes and oligochaetes and size-related variation in diet was found. Despite considerable similarity in the prey items, differences in food composition between the two species were observed and spatial variability in diet confirmed their opportunistic feeding behaviour. A high degree of dietary overlap was found in June and decreased steadily throughout the season. The prey composition in the guts of both species largely reflected the composition of the main macrobenthic taxa in the sediment. The overall data suggest that resources were not limiting in the littoral sandy nursery areas in the west of Ireland and no indications were found that exploitative competitive forces upon the benthic prey assemblages occurred between P. platessa and L. limanda. Feeding success, Fulton's K condition and dietary overlap, however, showed spatial and temporal variations, and were probably affected by the availability and density of macrobenthic prey.     

云南省把边江流域不同土地利用方式对大型底栖动物群落的影响

研究土地利用对大型底栖动物群落的影响,对流域土地利用规划修编和河流生态修复等有重要意义。以红河上游的把边江流域为研究区,调查大型底栖动物群落现状,计算37个样点上游集水区土地利用组分、配置、多样性和水文距离4个方面20个土地利用指标,分析不同土地利用方式对大型底栖动物群落的影响。本次调查共鉴定出25个大型底栖动物分类单元,其中水生昆虫最多,占分类单元总数的72%;摄食功能群以捕食者（PR）、刮食者（SC）和直接收集者（GC）为主。把边江流域城镇用地和林地对大型底栖动物群落的影响占主导地位,而耕地对大型底栖动物群落的影响较小。影响把边江流域大型底栖动物群落的关键土地利用指标为城镇用地面积比（3PLA）、城镇用地最大斑块指数（3LPI）、城镇用地聚合指数（3AI）、城镇用地水流长度（3FLOW）、林地最大斑块指数（1LPI）和林地形状指数（1LSI）。土地利用组分、配置和水文距离是影响把边江流域大型底栖动物群落的主要方面,而土地利用多样性对大型底栖动物群落的影响较小。大型底栖动物物种密度和物种多样性与3PLA、3LPI、3AI、3FLOW和1LSI呈负相关,与1LPI呈正相关。1LPI与浮游目（如小蜉科、扁蜉科）为代表的清洁物种呈现较明显的正相关关系。城镇用地指标与SC和SH（撕食者）密度具有显著的负相关关系,与GC密度有较弱的正相关关系,而与其他功能群没有明显的相关关系。SC和SH对水质和环境条件敏感,而GC对人类干扰耐受性较强。1LPI与SC和FC（滤食收集者密度）正相关,而与PR和GC密度负相关。SC和FC对生境的完整性要求较高,而GC和PR对人为干扰和较为破碎的生境更为适应。一方面,随着城镇用地的规模、边界复杂性和聚集程度增加,研究区大型底栖动物密度和多样性降低;另一方面,随着林地完整性降低,大型底栖动物物种均匀度降低。土地利用与大型底栖动物物种多样性和功能群多样性的关系不完全一致,1LSI和3FLOW与物种多样性负相关,而与功能群多样性呈正相关关系,土地利用对物种-功能群-群落不同尺度上的影响差异还需要更深入的研究。     

珠江口及邻近海域大型底栖动物多样性随盐度、水深的变化趋势

利用2006年7-8月(夏季)、2007年4-5月(春季)和2007年10-12月(秋季)珠江丰水期、平水期和枯水期3个航次在南中国海北部珠江口附近海域4条由河口、近岸到深水区调查断面的数据, 研究大型底栖动物多样性由河口-近岸-深水的变化趋势及与环境因子的关系。春季、夏季和秋季分别获得大型底栖动物273、256和148种, 各季节均以环节动物种类最多, 节肢动物次之。大型底栖动物种类数、丰度、生物量和Shannon-Wiener多样性指数均由河口向近岸海域升高, 再由近岸向外海深水区降低。Pielou均匀度深水区最高, 其次为近岸。河口和深水区大型底栖动物k-优势度曲线位于近岸浅水域曲线之上, 表明生物多样性由河口向近岸升高, 而由近岸向深水则降低。大型底栖动物与环境因子Pearson相关性分析表明, 春、秋季大型底栖动物种类数、丰度和生物量与水深呈显著的负相关, 秋季种类多样性指数和均匀度也与水深呈显著的负相关性, 而夏季仅生物量与水深呈显著的负相关; 春、秋季大型底栖动物种类数、生物量、丰度、多样性指数和种类均匀度与盐度的相关性不显著, 但是夏季大型底栖动物种类数、丰度、多样性指数和种类均匀度与盐度呈显著正相关。单位面积(0.2 m²)内, 珠江口及邻近海域大型底栖动物在近岸浅水区较深水区和河口生物多样性高, 且生物量丰富。     

Recolonisation of new habitats by meiobenthic organisms in the deep Arctic Ocean: an experimental approach

Commercial exploitation and abrupt changes of the natural conditions may have severe impacts on the Arctic deep-sea ecosystem. The present recolonisation experiment mimicked a situation after a catastrophic disturbance (e.g. by turbidites caused by destabilised continental slopes after methane hydrate decomposition) and investigated whether the recolonisation of a deep-sea habitat by meiobenthic organisms is fostered by variations in nutrition and/or sediment structure. Two “Sediment Tray Free Vehicles” were deployed for 1?year in summer 2003 at 2,500?m water depth in the Arctic deep-sea in the eastern Fram Strait. The recolonisation trays were filled with different artificial and natural sediment types (glass beads, sand, sediment mixture, pure deep-sea sediment) and were enriched with various types of food (algae, yeast, fish). After 1?year, meiobenthos abundances and various sediment-related environmental parameters were investigated. Foraminifera were generally the most successful group: they dominated all treatments and accounted for about 87?% of the total meiobenthos. Colonising meiobenthos specimens were generally smaller compared to those in the surrounding deep-sea sediment, suggesting an active recolonisation by juveniles. Although experimental treatments with fine-grained, algae-enriched sediment showed abundances closest to natural conditions, the results suggest that food availability was the main determining factor for a successful recolonisation by meiobenthos, and the structure of recolonised sediments was shown to have a subordinate influence.     

Species-energy relationships in deep-sea molluscs

Consensus is growing among ecologists that energy and the factors influencing its utilization can play overarching roles in regulating large-scale patterns of biodiversity. The deep sea--the world's largest ecosystem--has simplified energetic inputs and thus provides an excellent opportunity to study how these processes structure spatial diversity patterns. Two factors influencing energy availability and use are chemical (productive) and thermal energy, here represented as seafloor particulate organic carbon (POC) flux and temperature. We related regional patterns of benthic molluscan diversity in the North Atlantic to these factors, to conduct an explicit test of species-energy relationships in the modern day fauna of the deep ocean. Spatial regression analyses in a model-averaging framework indicated that POC flux had a substantially higher relative importance than temperature for both gastropods and protobranch bivalves, although high correlations between variables prevented definitive interpretation. This contrasts with recent research on temporal variation in fossil diversity from deep-sea cores, where temperature is generally a more significant predictor. These differences may reflect the scales of time and space at which productivity and temperature operate, or differences in body size; but both lines of evidence implicate processes influencing energy utilization as major determinants of deep-sea species diversity.     

Distribution of polychlorinated biphenyls (PCBs), lead,and cadmium in Manko Tidal Flat,Okinawa

Concentrations of polychlorinated biphenyls (PCBs), Pb, and Cd in sediment samples from the Manko Tidal Flat, an important area for migratory birds in Okinawa, were analyzed. High concentrations of PCBs were detected in the sediment samples from sites under a bridge at the end of the Manko Flat, whereas Pb and Cd concentrations did not indicate specific pollution. The spatial distribution and homologue proportion of PCBs indicated that these PCBs are probably attributed to the residue of paints used on the bridge in the 1970s. PCBs were detected in tilapias from sites in the Manko Flat and in a river connecting to the flat without head constructions. PCBs were also detected in small invertebrates, tanaids, in the flat. The distribution of PCB concentrations in the fauna was parallel to that in the sediments. The average PCB homologue proportions in tilapias and tanaids were similar to those in sediments.     

Effects of the burrowing mud shrimp,Upogebia yokoyai,on carbon flow and microbial activity on a tidal flat

Mud shrimps, Upogebia spp., are major constituents of macrobenthic communities in tidal flats in Japan. The impact of Upogebia yokoyai on carbon flow on tidal flats was examined by comparing CO₂ emission rates from plots with and without burrows in the Kurose River estuary, Japan. In situ CO₂ emission rates from plots with burrows were significantly higher than from those without. Laboratory measurements using sediment core samples that excluded respiration of macrobenthic organisms showed similar trends. Although there were no significant differences in grain size distribution, water content, or ignition loss between the sediment cores with and without burrows, oxidation–reduction potential was significantly higher in sediment cores with burrows. Analysis of phospholipid fatty acids (PLFA) indicated that microbial biomass and community structure did not differ significantly between cores with and without burrows. However, microbial respiration activity, as indicated by CO₂ emission rates per total PLFA content, was significantly higher in sediment cores with burrows than in those without. Our results indicate that burrows of U. yokoyai change the physicochemical conditions and increase microbial activity in the sediment, significantly affecting carbon flow in the tidal flat.     

Vertical distribution and abundance of gymnamoebae (Rhizopoda) in bottom sediments of the brackish water Nivå Bay (Baltic Sea,The Sound)

The sandy sediments of Niv? Bay (Baltic Sea, The Sound, Denmark) are often covered with the mats of sulphur bacteria and are temporarily anoxic. The vertical distribution and abundance of naked amoebae species in three sediment cores from this bay were studied. Amoebae were most abundant and diverse in the upper 1 cm of sediment, and their number and diversity decreased with increasing depth into the sediment. Amoebae were recovered from both upper oxygenated and deep anoxic layers of sediments. The species composition and abundance of amoebae was very heterogeneous, even at spatial scales of several centimeters, suggesting the existence of microhabitats selectively occupied by particular species. All species found were recorded from aerobic cultures and some of these amoebae occur in both the aerobic and anaerobic layers of the sediment. Minimal possible number of amoebae in the sediments, estimated for the first time as areal abundance integrated for depth was: core 1 -597 cm(-2); core 2 -1,110 cm(-2); core 3 -1,430 cm(-2). These abundances are probably best regarded as "potential" abundances of amoebae hidden in the sediments, as the question of the ratio between active and resting amoebae remains open.     

Mussels matter: postlarval dispersal dynamics altered by a spatially complex ecosystem engineer

This study investigated postlarval dispersal of soft-bottom macrofauna at a spatially complex intertidal mudflat comprising patches of bare sediment and an ecosystem engineer, the mussel Mytilus edulis. At each of four sites in Guard Point Cove, Maine, USA, we took core samples and deployed bedload traps in bare sediment and mussel bed habitats to estimate ambient densities, rates of sediment flux, and several measures of postlarval dispersal. Univariate and multivariate nonmetric multidimensional scaling (nMDS) results showed few significant site effects and no habitat×site interactions. In contrast, there were numerous significant habitat effects. Compared to the bare sediment, the mussel bed habitat had: fewer species; higher ambient density and proportional abundance of the oligochaete Tubificoides benedeni (the dominant species in both habitats); lower ambient densities and proportional abundances of major taxa and the nonoligochaetes as a group; and higher sediment flux and relative (i.e., per capita) dispersal of nonoligochaetes. Macrofauna species dispersed in relative proportions that were different from those in the ambient assemblage. Per capita T. benedeni transport rates were low in mussel beds compared to those for nonoligochaetes, consistent with the view that beds represent favorable habitat for oligochaetes. The number of total macrofauna individuals trap⁻¹ day⁻¹ was negatively correlated with ambient density and positively correlated with sediment flux in both habitats, but these relationships were significant only in the mussel bed. The results indicate that altered transport rates of sediment and postlarvae are important mechanisms by which mussels act as ecosystem engineers to modify soft-bottom habitats. Differential transport rates caused by aggregations of mussels and other foundation species must be considered in explanations of spatial pattern in soft-bottom communities.     

Sand-dollar mellita quinquiesperforata (Leske) burrow trails: sites of harpacticoid disturbance and nematode attraction

The effect of sand-dollar Mellita quinquiesperforata (Leske) burrowing on a soft-bottom meiofauna community was examined at a subtidal site located off the northwest Florida coast. M. quinquiesperforata were common at the site with an average of 3 ind · 0.25 m ⁻² and their burrow trails were a distinctive feature of the sediment surface. At the site, sand dollars disrupted ≈ 14% of the sediment surface · h⁻¹. Sand-dollar burrowing did not decrease total meiofauna abundances significantly (P > 0.05); however, the abundances of one harpacticoid species, Halectinosoma sp., foraminifera and mites were significantly lower (P < 0.05) in samples collected from a burrow trail than in samples collected in front of the sand dollar. The lower abundances of Halectinosoma sp. and mites in the burrow trail were probably due to sediment disturbance. The lower abundances of foraminifera in the burrow trails were probably due to sand-dollar predation. In contrast to studies in intertidal areas, total nematode abundances were significantly higher (P < 0.05) in the samples collected behind a moving sand dollar than in samples collected in front of the sand dollar. Possible reasons for the enhanced abundances are: (1) increased food availability in the form of mucus and/or excreted cells that line the sand-dollar gut; and (2) increased pore space within the sediment.     

Shallow lake sediments provide evidence for metapopulation dynamics: a pilot study

The aim of this pilot study is to test the hypotheses that sediment cores can provide evidence for metapopulation dynamics and that these can be linked with site characteristics. We focus on temporal patterns of incidence and abundance of overwintering stages (statoblasts) produced by the freshwater bryozoan Cristatella mucedo, an organism characterised by a metapopulation ecology, in sediment cores retrieved from 18 UK lakes. Runs and goodness-of-fit tests provided evidence for population instability, periods of low abundance and absence, and of asynchrony—all signatures of metapopulation dynamics. Further hypothesis testing indicated that extinction risk is greater in more isolated sites and in sites of smaller size. Absence of statoblasts from the top sections of spatially separated, replicate cores provided independent evidence for extinction in one site. Our study demonstrates how the abundances of sedimentary-bound propagules may be analysed initially for metapopulation dynamics and subsequently how this may lead to working hypotheses regarding the drivers of such dynamics. The sediment archive represents a unique historical record whose potential for characterising metapopulation dynamics has previously been untapped but is broadly relevant for understanding the population biology of freshwater organisms.     

Quantitative ichnology of modern pelagic deposits in the abyssal Atlantic

Quantitative sedimentologic aspects of bioturbation were investigated in a series of deep-sea box cores, which were collected over a broad latitudinal range (35°N to 30°S) and bathymetric range (1.4 to 5.7 km) in the central Atlantic Ocean. All cores were thoroughly bioturbated, and numerous generations of burrowing could be discerned in many instances. Preservation of individually distinct burrows ranged from poor to excellent, and eight ichnogenera plus several unnamed biogenic structures were recognized.The distribution of calcium carbonate, organic carbon, selected species of planktic foraminifera and sediment grain size were examined in several cores. These measurements indicated that the surficial Mixed Layer, which ranged from 3 to 10 cm thick, was statistically more homogeneous than the underlying Transition Layer. This relationship is seen most clearly with respect to lateral and vertical variations in the calcium carbonate content of the cores. Bioturbation of abyssal pelagic deposits appears to be a two-phase process consisting of (a) homogenization of the upper few centimeters (i.e., the Mixed Layer) by shallow-burrowing meiofauna, and (b) heterogeneous mixing of the underlying strata (i.e., the Transition Layer) by relatively deep burrowers. The heterogeneously mixed Transition Layer becomes the preserved trace fossil record; under normal circumstances the homogenized Mixed Layer is not preserved.     

钦州湾大型底栖动物生态学研究

通过2008年~2009年在钦州湾及附近海域进行的4个航次的大型底栖动物调查,共获大型底栖动物8门62科94种,软体类最多,其次为多毛类,种类季节变化较大。以优势度指数Y>0.02为判别标准,调查区春季优势种为方格皱纹蛤（Periglypta lacerata (Hanley)）、刺足掘沙蟹（Scalopidia spinosipes Stimpsom）和独齿围沙蚕（Perinereis cultrifera Grube）,夏季优势种为方格皱纹蛤、刺足掘沙蟹和持真节虫,秋季优势种为曲波皱纹蛤和网纹藤壶,冬季优势种为肋鲳螺和方格皱纹蛤。春、夏季优势种变化不大,秋、冬季优势种变化较大,除方格皱纹蛤外均为季节特有种。海区底栖生物平均总密度和平均总生物量分别为439ind./m2和115.14g/m2。与20世纪80年代钦州湾茅尾海调查结果相比,平均栖息密度有所升高,但是平均生物量却有较大程度的降低。底栖动物群落的丰富度指数（D）、Shannon-Wiener多样性指数（H′）和均匀度指数（J′）平均值分别为4.01、1.80和0.73,水平不高。用SPSS软件将各站大型底栖动物的平均密度、平均生物量、多样性指数等生态特征值与水深等理化因子进行了Pearson相关分析,结果表明春季各特征指数与环境因子相关性不显著;夏季丰度、多样性指数和均匀度指数均与水深呈显著负相关,种类数、丰富度和多样性指数与沉积物pH呈显著负相关;秋季密度与硫化物呈显著正相关;冬季生物量与硫化物和有机质均呈显著正相关。     

Short-term variations in the fluxes and composition of seston in near-bottom traps in the southern North Sea

In this study we attempted to measure the potential food availability for macrobenthic interface feeders using a new device (sediment recorder) which traps bed load particles at a height of 10 cm above the sea floor. The recorder is positioned flat on the seabed and alternately exposes a shallow collector mounted in a smooth surface mimicking the sediment surface. The samples were analyzed for their content of chlorophyll a (Chl) and dry weight (DM). We compared the sediment recorder data with the results obtained with a sediment trap suspended 3.2 m above the sea floor. Measurements were carried out in spring and fall at two stations in the southern North Sea with different sediment type, maximum current velocities and biomass (sand, station B vs silty sand, station F). The recorder deployments in November yielded higher Chl fluxes and a higher quality of particles (Chl:DM ratio) than the trap at both stations. Unlike the trap samples, in which Chl and DM were always positively and strongly correlated, maximum Chl and DM fluxes in the recorder samples were out of phase, particularly at station B, pointing to a highly variable quality during the tidal cycle. Unexpectedly, Chl fluxes and Chl:DM ratios in the recorder samples at station B were higher than at station F in both seasons, although the benthic biomass at the latter station was five times higher. The highest Chl fluxes and particle quality (Chl:DM) at station B were measured during slack tides when interface feeding would be least hampered by drag forces. Station B is nevertheless characterized by a low macrobenthic biomass and a scarcity of interface feeders, specifically of suspension-feeding bivalves. Possible reasons for this apparent discrepancy are discussed. Electronic Publication