The Meiobenthos in the Area of Japanese Scallop Cultivation in Minonosok Bay (Peter the Great Bay,Sea of Japan)

In Minonosok Bay, in a region of long-term industrial mariculture of mollusks, a steady biohydrochemical complex with increased organic matter content has been formed, in which the meiobenthos community was represented by a rather complete set of taxonomic groups of low population density. There were 16 groups (order, class) of the meiobenthos revealed, and the greatest population density was recorded in the central part of the bay under installations with suspended mollusks, (333000 ind./m²). Nematodes dominated in the eumeiobenthos; however, crustaceans prevailed in the bottom water layer and sediments at stations with increased oxygen content. Bivalves and gastropods dominated in the pseudomeiobenthos. Correlation analysis has revealed the dependence of the population density of the total meiobenthos and eumeiobenthos on the type of ground. There were 42 nematode species revealed; Axonolaimus seticaudatus, Enoplolaimus medius, Daptonema sp., Paracomesoma sp., and Oncholaimium paraolium dominated. Three nematode taxocens were discriminated by dominating species in the population density and results of cluster analysis of the data. Detritivorous nematodes prevailed in all types of ground. A correlation was found between the index of species diversity of nematodes and the content of organic carbon in the ground.     

Meiofauna distribution and mesoscale variability in two sites of the Ross Sea (Antarctica) with contrasting food supply

Meiofauna abundance, biomass and community structure were investigated in two comparable deep sites of the Ross Sea (Antarctica) characterized by different trophic and sediment characteristics. Site B (567 m depth, dominated by muddy sediments) and site C (439 m depth, characterized by the presence of calcareous debris and coarse sand) were located at increasing distance from the polynyas and were subject to different inputs of organic material to the seabed. Total meiofauna abundance ranged from 192.0 to 1191.2 ind. 10 cm⁻², and total biomass varied between 9.5 and 50.3 μgC 10 cm⁻². Meiofauna densities from the Ross Sea are, on average, 2–7 times lower than those reported from other similar deep polar regions and displayed significant differences between the sites. Nematodes dominated the samples at both sites, but their relative significance changed between the sites (80% at site B and 56% at site C), followed by copepods (1.6% and 35% at sites B and C, respectively). Meiofauna composition at site B appeared similar to that reported for deep-sea antarctic or temperate sediments, whereas the composition at site C was similar to that of coastal areas. On a macroscale, the different inputs of utilizable organic material at the two sites were reflected in meiofaunal distribution patterns, indicating that meiofaunal communities from the Ross Sea are dependent on particulate organic matter fluxes from the photic layer and are coupled to pelagic phenomena. Very low microscale variations (i.e. between replicates) in meiofauna density contrasted with large mesoscale variability, which was related to the concentration of the main food indicators (phytopigments, proteins, carbohydrates and lipids). Accepted: 18 February 1999     

Annual cycles of benthic community oxygen uptake in a deep oligotrophic lake (Attersee,Austria)

Benthic community oxygen uptake of Lake Attersee sediments was measured between 1976 and 1979, along two profiles at 25, 50 and 100 m depth. Profile I was situated in the bay of Unterach into which the main tributary, Mondsee-Ache, discharges a high load of organic matter. Profile II was chosen at Weyregg to avoid the eutrophying effect of Mondsee-Ache. Oxygen uptake rates of Unterach sediments at 25 and 50 m depth were found to be higher when compared to the other sites (mean rates: Unterach 25 m = 15.56, 50 m = 11.05 mg O₂ · m⁻² · h⁻¹; Weyregg 25 m = 6.43, 50 m = 5.14 mg O₂ · m⁻² · h⁻¹). Organic content of the uppermost sediment layer was also higher in the bay of Unterach than at Weyregg. Oxygen uptake rates of undisturbed sediment cores vary considerably throughout the year, but no simple correlation existed with variations in organic content of the sediments. Peaks of organic matter were found to concur with following peaks of oxygen uptake rates, which implies that a certain time span is necessary for transforming freshly sedimented organic matter into a state digestable for the benthic community. The retardation between increasing organic matter of the sediment and the corresponding increase of benthic oxygen uptake was different at Unterach and Weyregg respectively, which is explained by the different quality of sedimenting material.     

Stimulation of sulfate reduction rates in Mediterranean fish farm sediments inhabited by the seagrass <Emphasis Type="Italic">Posidonia oceanica</Emphasis>

Sulfate reduction rates and biogeochemical parameters of fish farm sediments across the Mediterranean were investigated in the order to evaluate the potential effects of organic matter inputs on habitat quality for the common seagrass Posidonia oceanica. Four study sites were selected in Spain, Italy, Greece and Cyprus to represent the Mediterranean basin. P. oceanica was found in immediate vicinity of all the farms, which were located at physically exposed sites about 1 km from the shore lines. Organic matter accumulation, sulfate reduction rates and sulfur pools were measured in depth profiles along transects from the farms in both bare and vegetated sediments. Results show that although the organic matter accumulation was minor at the sites (POC < 2.8% DW), the sulfate reduction rates were high, in particular at the largest farm in Italy (up to 212 mmol m⁻² d⁻¹), similar to rates found at shallower, temperate fish farm sites, where higher sedimentation rates can be expected. Sulfate reducing bacteria in these low-organic, carbonate-rich Mediterranean sediments respond strongly to organic matter loadings and cause habitat degradation. Sulfate reduction rates measured in the P. oceanica sediments were among the highest recorded (7.8–42.0 mmol m⁻² d⁻¹) similar to rates found in degrading meadows impacted by organic matter loadings. As sulfate reduction rates were correlated with the sedimentation rates along the transects rather than organic matter pools this suggests mineralization processes were controlled by organic matter loading in fish farm sediments. The vegetated sediments near the net cages were more reduced due to accumulation of sulfides compared to control sites, which is a possible contributing factor to the observed seagrass decline in the farm surroundings. It is recommended that Mediterranean fish farms are placed in areas with rapid dispersal of particulate waste products to minimize organic matter loading of the sediments and thereby preserve habitat quality for benthic fauna and flora.     

Composition and community structure of the coralline algal reefs from Atol das Rocas, South Atlantic, Brazil

 Coralline-algal frameworks from Atol das Rocas reefs were sampled along windward and leeward transects, and multivariate statistical analysis was used to investigate the composition and community structure of the encrusting community. The following components of the reefs were identified in slabbed and polished reef blocks sampled along each transect: encrusting coralline algae dominated by Porolithon cf. pachydermum, vermetid gastropods, Homotrema rubrum, acervulinid foraminiferans, molluscs, corals, polychaete tubes, clionid sponge borings, polychaete/sipunculid borings, cemented sediments, and growth cavities. Q-mode cluster analysis correctly classified 78% of all windward samples and 69% of all leeward samples, and R-mode separated reef components adapted to high wave energy environments from those adapted to low wave energy. Separate classification and ordination of samples from each transect indicate that seriation breakdown occurs in the windward reef between 25 and 45 m from the reef front. In the leeward reef between 75 and 90 m from the leeward reef front, seriation breakdown was not found to be significant. These results confirm that seriation (zonation) is best developed in the windward reef, as has been documented in coral-dominated reefs. Accepted: 28 February 2000     

Meiofaunal (re)colonization of the Arctic intertidal (Hornsund,Spitsbergen) after ice melting: role of wrack deposition

Intertidal meiobenthos of Hornsund—the southernmost fjord of Spitsbergen—was investigated between July and September 2005. Mean total meiofaunal densities ranged between 4.3 and 328 ind. 10 cm⁻². Nematode assemblages were impoverished in terms of the number of genera when compared with those from the western Spitsbergen coast (11 vs. 25–28 genera in total, respectively). It is suggested that severe environmental conditions in the southern part of Spitsbergen overcome the adaptation skills of many nematode species and hamper the establishment of a diverse community. Comparatively high nematode numbers on a beach subject to heavy macroalgal wrack input contrast sharply with numerically poor communities in sparse-wrack beaches (up to 315 vs. 31 ind. 10 cm⁻², respectively). It is suggested that the wrack input to the Arctic beach may substantially influence the richness and composition of the intertidal meiobenthic community. Nematode assemblages were dominated by extreme colonizers: Geomonhystera disjuncta and rhabditids. Their relatively high densities in beach sediments recorded at the beginning of July indicate their ability to recover rapidly after the winter period and to effective (re)colonization of the intertidal habitat just after the ice melt. Average concentration of rhabditids and monhysterids associated with macroalgal wrack deposited on the upper shore was as high as 52 × 10³ individuals per gram of the substrate. It is hypothesized that nematodes can play a substantial role in the wrack decomposition in the Arctic intertidal.     

Movement of carbon among estuarine habitats and its assimilation by invertebrates

We measured the extent of movement of carbon and its assimilation by invertebrates among estuarine habitats by analysing carbon stable isotopes of invertebrates collected along transects crossing the boundary of two habitats. The habitats were dominated by autotrophs with distinct isotope values: (1) mudflats containing benthic microalgae (mean −22.6, SE 0.6‰) and (2) seagrass and its associated epiphytic algae (similar values, pooled mean −9.8, 0.5‰). Three species of invertebrates were analysed: a palaemonid shrimp, Macrobrachium intermedium, and two polychaete worms, Nephtys australiensis and Australonereis ehlersi. All species had a similar narrow range of isotope values (−9 to −14‰), and showed no statistically significant relationship between position along transect and isotope values. Animals were relying on carbon from seagrass meadows whether they were in seagrass or on mudflats hundreds of metres away. Particulate organic matter collected from superficial sediments along the transects had similar values to animals (mean −11.1, SE 1.3‰) and also showed no significant relationship with position. The isotope values of these relatively immobile invertebrates and the particulate detritus suggest that carbon moves from subtidal seagrass meadows to mudflats as particulate matter and is assimilated by invertebrates. This assimilation might be direct in the case of the detritivorous worm, A. ehlersi, but must be via invertebrate prey in the case of the carnivorous worm, N. australiensis and the scavenging shrimp, M. intermedium. The extent of movement of carbon among habitats, especially towards shallower habitats, is surprising since in theory, carbon is more likely to move offshore in situations such as the current study where habitats are in relatively open, unprotected waters.     

Phylogenetic analysis of culturable marine bacteria in sediments from South Korean Yellow Sea

Biogeochemical and microbiological characterization of marine sediments taken from the Yellow Sea of South Korea was carried out. One hundred and thirty six bacterial strains were isolated, characterized and phylogenetic relationship was evaluated. The gene sequences of 16S rDNA regions were examined to study the phylogenetic analysis of bacterial community in the marine sediments. Among 136 isolates, 5 bacterial isolates were identified as novel members, remaining 131 isolates were fall into 5 major linkages of bacterial phyla represented as follows: Firmicutes,, -@Proteobacteria, High G + C and Bacteroidetes. Bacterial community in sediments mainly dominated by Firmicute (58.77%) and followed by @-Proteobacteria (38.16%). @-Proteobacteria domain highly diverged and mainly consists of the genera Vibrio, Marinobacterium, Photobacterium, Pseudoalteromonas, Oceanisphaera, Halomonas, Alteromonas, Stenotrophomas and Pseudomonas. Total N and Organic matter content in Yellow Sea of South Korea were relatively high. The Total-N content in the sediments was varied from 177.31 to 1974.96 (mg/kg) and organic matter ranged from 0.82 to 4.23 (g/100 g⁻¹). The current research work provides clear explanation obtained for the phylogenetic affiliation of the culturable bacterial community in sediments of South Korean Yellow Sea and revealed the relationship with biogeochemical characteristics of the sediments.     

Community structure and spatial distribution of benthic fauna in the Bellingshausen Sea (West Antarctica)

The structure and spatial distribution of the macrofauna community of the Bellingshausen Sea in the western sector of Antarctica was studied during the ‘BENTART–06’ oceanographic expedition. This is one of the least explored Antarctic seas. A total of 20 box cores were sampled at 11 stations ranging from 157 to 3,304 m depth, using an USNEL-type box corer (BC) dredge. Representatives of 25 higher taxa of invertebrates were collected. Deeper sampling sites were less rich in taxa (4–7 taxa), whereas the figures were higher at shallower sites (up to 17 taxa). Faunal density on the sea bottom revealed a horizontal spatial gradient from the western sites with extremely low figures (90 indiv./m²) towards the eastern ones with the highest figures (1,360 indiv./m²) close to the Antarctic Peninsula. Several abiotic factors (depth, redox, organic matter, carbonates and particle size of surficial sediments) were measured simultaneously on the sea floor to characterise the substrate preferences of the fauna. Positive correlations were found between the faunal distribution and a combination of depth, redox values, and organic matter content of sediments. This indicates decreasing availability of food in the deeper bottoms of the Bellingshausen Sea with a prevalence of depauperated bottoms dominated almost exclusively by a foraminiferans community.     

The significance of food web structure for the condition and tracer lipid content of juvenile snail fish (Pisces: Liparis spp.) along 65-72{deg}N off West Greenland

Plankton community structure was analysed during summer along 65-72N off West Greenland, The south-north transect mimics a time span of months in the phytoplankton and zooplankton succession during the Arctic summer. In the south, the mixing depth was below the photic zone and the phytoplankton community was dominated by flagellates. North of Disko Bay (69°N), the water column was stratified due to melt water, and the phytoplankton dominated by flagellates and a small amount of diatoms, but with higher biomass and primary production. The copepod community was dominated by Calanus spp. and was more progressed in terms of developmental stage composition in the south. The biochemical lipid finger printing in the food chain phytoplankton-mesozooplankton-juvenile planktivorous snail fish (Liparis spp.) confirmed the qualitative composition of the phytoplankton, and revealed that the mesozooplankton >400 m in body size contained lipids originating from a non-diatom diet in the south, whereas it showed mesozooplankton lipids originating from a diatom diet in the north. The C16:1 (n-7)/C16:0 ratio increased from 0.63 to 3 for mesozooplankton along the transect, indicating feeding based on diatoms in the north. This ratio was reflected in Liparis spp. along the transect. The condition of the juvenile snail fish was generally good (high b exponent) along the entire transect based on the relationship: total fatty acids (mg) = 0.0008 x standard length (mm)²³⁵. However, the relationship triacylglycerol:cholesterol was much higher north of Disko Bay, indicating a much better condition and thereby potential starvation tolerance and survival in the north. We conclude that the plankton structure along the south-north transect reflected the yearly succession in phytoplankton with respect to tracer lipids and that juvenile Liparis spp. were in a better condition when foraging on wax ester-rich mesozooplankton, which in turn developed ontogenetically during a diatom-based spring bloom in the north.      

Polychaete distribution on the southwestern Atlantic continental shelf

Diversity and distribution of polychaetes on the southeastern Brazilian Shelf (SBS) adjacent to the city of Santos were studied. The study area is situated in the vicinity of Santos Bay with its estuarine complex and other small rivers along the coast. A total of 16,274 specimens belonging to 214 polychaete species were found at 21 sampling stations during two different periods. Two communities occur along the shelf and were related firstly to sediment characteristics. Prionospio dayi (Spionidae) was dominant in the inner shelf community that was characterized by well-sorted, very fine sand. The outer shelf community was found in muddy sediments with high organic matter content and was dominated by subsurface deposit feeders, like Petersenaspis capillata (Sternaspidae) and Leitoscoloplos kerguelensis (Orbiniidae), and by large carnivores such as Aglaophamus sp. (Nephtyidae) and Sigambra sp. (Pilargidae). A transition zone of mixed sediments presenting high diversity and richness was found between these communities. The characteristics of bottom water and food quality in the sediment were important to divide the inner shelf into two sub-areas. Nearshore sampling stations (A group) were more influenced by freshwater input, mainly during summer. This influence is not conspicuous at stations close to 30?m depth (B group). However the effect of South Atlantic Central Water mass (SACW) intrusion on the benthic system was observed on the inner shelf – B group during the summer. The summer intrusion of SACW onto the inner shelf may explain the higher quality of organic matter that resulted in an increase in polychaete abundance and richness.     

The distribution of vascular plant species and guilds in space and time along a desert gradient

Abstract. We studied distribution patterns of vascular plant species and environmental variables for three years along a permanent transect traversing a closed-drainage watershed in the northern Chihuahuan Desert of south-central New Mexico, USA. The transect extended for 2.7 km from a basin floor playa (1310 m elevation, fine-textured soil), across a piedmont slope, and onto the base of a granitic mountain (1410 m elevation, coarse-textured soil). The gradients in elevation and soils across our transect, along with variable seasonal rainfall, downslope redistribution of water and organic matter, and soil texture-related variation in infiltration, water holding capacity, and moisture release characteristics, interact to generate a complex spatial and temporal gradient of available soil water and nitrogen. We grouped plant species into guilds according to growth form and photo synthetic pathway type. These guilds are spatially and temporally differentiated along the transect such that particular groups utilize particular seasonal phases or spatial regions of the gradient. We identified six distinct plant communities along the transect. C₄ perennial grasses dominated the mesic/high nitrogen portion of the gradient, which occurred at the highest (upper piedmont grassland, dominated by Bouteloua eriopoda) and lowest (playa, dominated by Panicum obtusum) elevations along the transect. C₃ shrubs were dominant in the xeric/low nitrogen portion of the gradient located near the middle of the transect (bajada shrubland, dominated by Larrea tridentata). C₃ shrubs also dominated a narrow zone of vegetation located adjacent to the playa (playa fringe, dominated by Prosopisglandulosa). C₄ perennial grasses, C₃ subshrubs, and C₃ and C₄ perennial forbs and annuals were co-dominant in the intermediate locations along the gradient, which occurred below (mixed basin slopes) and above (lower piedmont grassland) the bajada shrubland. Life-form distribution patterns at the small scale of our study reflect some of the patterning that occurs at larger scales in response to climate gradients. The distributions of some species and guilds along the transect are apparently modified by competitive interactions.     

Differential metabolism of dimethylsulfoniopropionate and acrylate in saline and brackish intertidal sediments

In anoxic Spartina altemiflora—dominated sediments along a naturally occuring salinity gradient (the Cooper River estuary, South Carolina, U.S.A.), dimethylsulfoniopropionate (DMSP) was metabolized to dimethyl sulfide (DMS) and acrylate by sediment microbes. The rate of DMSP degradation and acrylate mineralization by sediment microbes was similar at all sites along this 25-km transect. However, sediments amended with acrylate (or DMSP) showed significantly higher rates of N₂ fixation (measured as acetylene reduction activity) (ARA) in the saline sediments downstream than brackish sediments. These results are consistent with the fact that acrylate stimulated the rates of both denitrification and CO₂ production in the saline sediments at the mouth of the river more than tenfold over rates in brackish sediments. Enrichment experiments indicate that microbes capable of using DMSP or acrylate were not present in upstream sediments despite the fact that microbial biomass, percent organic matter, and both glucose-stimulated ARA and denitrification were highest upstream. It appears that acrylate utilizing, N₂ fixing, and denitrifying populations are insignificant in the lower salinity sediments of the estuary. These results may reflect the availability of DMSP, which averaged 10.3 nmol g wet wt^–1 of saline sediments and levels less than our detection limit (1 m) in brackish sediments. Correspondence to: D.C. Yoch.     

Quantitative distribution of meiobenthos and the structure of the free-living nematode community of the mangrove intertidal zone in Nha Trang bay (Vietnam) in the South China Sea

Meiobenthic studies were performed in an intertidal area in the Be River estuary (Nha Trang Bay, Vietnam). The study area is an area of riverine-type mangroves that have been heavily damaged by human impacts, including timber cutting and waste. Three biotopes are situated in the middle intertidal zone: a fringe of Rhizophora stylosa, a bush area composed of Avicennia aff. alba behind it, and muddy sand with fiddler crabs (Uca spp.), which is free of mangrove plants. Three replicate samples of meiobenthos were collected in each biotope and each sample was subdivided into two layers: 0–1 and 1–4 cm. The abundance of metazoan meiobenthos varied from 735 specimens/10 cm² in the Uca spp. biotope to 244 specimens/10 cm² beneath the Rhizophora trees. Six taxonomic groups of high rank were found among the meiofauna: Nematoda, Copepoda (Harpacticoida), Oligochaeta, Turbellaria, Kinorhyncha, and Foraminifera (Allogromiida). The spatial variability of meiobenthos and its key taxa was estimated and the spatial distribution patterns of free-living nematode species were described. About 90% of the total meiobenthos inhabited the upper 0–1 cm of the sediments. Nematodes constituted 90–95% of all meiobenthic organisms in the samples. A total of 48 species of free-living nematodes were found in the investigated mangrove intertidal area. In terms of species composition and set of dominants, the nematode community is comprised of three local assemblages: one of them inhabits the uppermost centimeter in the Uca and Avicennia biocenoses; the second assemblage occupies the upper sediment layer in the Rhizophora stand; a less abundant but specific assemblage of several nematode species occurs in the subsurface sediments at all three sites.     

Spatial and temporal variability in benthic processes along a mangrove-seagrass transect near the Bangrong Mangrove,Thailand

Benthic primary production and nutrient dynamics were examined along a transect in the Bangrong mangrove forest in Thailand. Six stations were established extending from a high-intertidal site within the mangrove forest to low-intertidal flats and seagrass beds in front of the mangrove forest. Benthic processes (O₂ and CO₂ fluxes) and nutrient dynamics (mineralization, sediment-water fluxes, pore water and sediment pools) were measured under light and dark conditions during wet and dry seasons over a 2-yr period. The sediments were mostly autotrophic, only the mangrove forest sites were net heterotrophic during the wet season. Maximum daily net primary production was found at the non-vegetated tidal flats (40–75 mmol O₂ m^-2d^-1), where light and nutrient availability were highest. The variation in benthic mineralization along the transect was minor (1.6–4.3 mmol CO₂ m^-2h^-1) and did not reflect the large changes inorganic matter content (organic carbon: 0.7–4.2% DW) and quality (C:N ratio varied from 25 to 100), suggesting that the mineralizable pool of organic matter was of similar magnitude at all sites. There was only minor seasonal variation in rates of mineralization. The net primary production showed more variation with lower rates in the mangrove forest (reduced with 74%) and higher rates at the tidal flats (increased with 172%) and in the seagrass beds (increased with 228%) during the wet season. The nutrient pools and fluxes across the sediment-water interface were generally low along the transect, and the sediments were efficient in retaining nitrogen in the nutrient limited mangrove/seagrass environment. Pools and fluxes of phosphorus were generally very low suggesting that benthic primary production was phosphorus limited along the transect. This revised version was published online in July 2006 with corrections to the Cover Date.     

Spatial and inter-annual variability of the macrobenthic communities within a coastal lagoon (Óbidos lagoon) and its relationship with environmental parameters

The present work aims to analyse spatial and inter-annual variability in the benthic environment within the Óbidos lagoon, assessing the relationships between environmental characteristics and macrobenthic distribution patterns. Sediment samples were collected in February 2001 and 2002 for the study of macrofauna and biogeochemical parameters (sediment grain size, organic matter, organic carbon, chlorophyll a, and phaeopigments). Comparing 2001 to 2002, a general increase in the number of species, diversity and equitability indices was observed throughout the study area. Likewise, there was an increase of phytopigments and organic matter contents in the upper sediment layer. Based on the macrobenthic community patterns and environmental variables three main areas could be distinguished in both years: an outer area near the inlet mostly influenced by the sea, with very depressed number of species and abundance, and dominated by Saccocirrus papillocercus, Lekanesphaera levii, Microphthalmus similis and Nephtys cirrosa; an intermediate area located in the central part of the lagoon characterized by sandy sediment and low organic carbon, and colonized by a high diverse community with Hydrobia ulvae, Cerastoderma edule and Abra ovata as the most characteristic species; and the innermost area of the lagoon with muddy enriched sediments dominated by Heteromastus filiformis, oligochaetes, Scrobicularia plana, Cyathura carinata, Corophium acherusicum, phoronids, insect larvae and Corbula gibba. Deposit-feeders were dominant in the muddy sediments from the inner area, where suspension-feeders were also abundant. Carnivores were associated with clean sandy sediments from the inlet area and herbivores were more abundant within the central area.     

The sub-ice fauna of the Laptev Sea and the adjacent Arctic Ocean in summer 1995

The sub-ice habitat and fauna in the Laptev Sea and the adjacent Arctic Ocean were investigated during the “Polarstern” cruise ARK XI/1 in summer 1995. At the ice-water interface a thin thermo- and halocline developed at many stations due to melting processes. In the lower centi- to decimetres of the ice, an accumulation of organic matter was found (particulate organic carbon: 1.9 mg l⁻¹, chl a: 3.3 μg l⁻¹) that may have provided a food source for the fauna. The water layer directly beneath the ice was inhabited by high numbers of various nauplii (130–23911 ind. m⁻³), and two ecological groups, the pelagic sub-ice fauna that originates from the surface water plankton, and the sympagic sub-ice fauna that migrates into this boundary layer from the ice interior. The pelagic fauna dominated the sub-ice community both in terms of species number and abundance. Both groups mainly comprised small copepods (e.g. Oithona similis, Oncaea borealis, Pseudocalanus spp., Halectinosoma spp., Tisbe spp.), but foraminifers and pteropods, for example, also occurred regularly. Diversity was generally low. Factors influencing the composition and abundance of the sub-ice fauna were most likely water depth, salinity and sea-ice sediments. Accepted: 6 July 1998     

Binding of phosphate in sediment accumulation areas of the eastern Gulf of Finland,Baltic Sea

The relationships between P and components binding P were studied by analysing the concentrations of N, P, Fe, Mn, Ca and Al in sediments and pore water along the estuarine transect of the River Neva in August 1995. The high sediment organic matter concentration resulted in low surface redox potential and high pore-water o-P concentration, whereas the abundance of amphipods resulted in high surface redox potentials and low pore-water o-P concentration. However, despite the variation in sediment organic matter and the abundance of amphipods, very reduced conditions and slightly variable concentrations of Tot-P (0.7–1.1 mg g^–1 DW) were observed in the 10–15 cm sediment depth along the estuarine gradient, indicating that the pools of mobile P were largely depleted within the depth of 0–15 cm. Multiple regression analysis demonstrated that organic matter and Tot-Fe concentration of the sediment were closely related to the variation in Tot-P concentration of the sediments (r ² = 0.817, n=32). In addition, the high total Fe:P ratio suggested that there is enough Fe to bind P in sediments along the estuarine gradient. However, low Fe_diss concentrations in the pore water of reduced sediment (redox-potential <–50 mV) indicated efficient precipitation of FeS (FeS and FeS₂), incapable to efficiently bind P. Consequently, the low Fe_diss:o-P ratio (< 1) recorded in pore water in late summer implied that Fe³⁺ oxides formed by diffusing Fe_diss in the oxic zone of the sediments were insufficient to bind the diffusing o-P completely. The measured high o-P concentrations in the near-bottom water are consistent with this conclusion. However, there was enough Fe_diss in pore water to form Fe³⁺ oxides to bind upwards diffusing P in the oxic sediment layer of the innermost Neva estuary and the areas bioturbated by abundant amphipods.     

Ordination of some littoral benthic communities in Bear Lake,Utah-Idaho

Summary Bottom invertebrate communities were compared along the western shoreline of a large oligotrophic lake (Bear Lake, Utah-Idaho). A technique of community ordination was used for the comparisons. Ordination indicated that differences among stations were associated with local differences in bottom type. The bottom type was apparently influenced by isolation from lake currents, nutrient additions, and increased amounts of fine sediments and organic matter. The amount of silt+clay was the most important sediment factor affecting the invertebrate communities. Most communities were dominated by a small species of larval chironomid, Tanytarsus.     

Organic matter composition in coastal sediments at Terra Nova Bay (Ross Sea) during summer 1995

We illustrate the spatial and vertical distribution of sediment phytopigments and organic matter biochemical composition at Terra Nova Bay (Ross Sea) during summer 1995. Coastal sediments displayed high phytopigments concentrations associated with huge amounts of labile organic matter largely dominated by proteins. This result was opposite to previous observations in the same area. Such comparison suggested that whilst organic matter quantity in the sediments depended upon the vertical input from the water column, temporal changes in its biochemical composition were related to benthic processes. As considerably high concentrations of biopolymeric organic carbon were found even at 6-cm depth and according to the “loss type” functioning of the coastal waters of the Ross Sea, we stress the summer time occurrence in coastal sediments of an important organic matter burial. Accepted: 24 October 1999