Evolutionary implications of swimming behaviour in meiobenthic copepods

Body morphology is said to be the all important factor in determining swimming prowess in copepods. Fusion and differentiation of the body (tagmosis) is coupled with advance into the pelagic realm of the Gymnoplea and is thought, by the provision of a rigid thoracic tagma, to promote swimming efficiency. Thus pelagic copepods are believed to be secondarily derived from bottom dwelling predecessors. Experimental evidence is presented to show that the majority of bottom dwelling harpacticoid families, including the most primitive and the most advanced, have representatives that undergo active sustained swimming movements. Such a widespread occurrence is indicative of a conservative evolutionary trait. This primitive behaviour is linked to precopulatory association which takes place necessarily in the water column; it is a feature retained by representatives of all copepod orders. The implication of cephalic appendage vibration (feeding currents) is the essential feature in the swimming success of the Gymnoplea; planktonic efficiency in these is suggested to have evolved coincident with, rather than because of increased tagmosis.     

Diel and seasonal vertical distribution of meiobenthic copepods in muddy sediments of a eutrophic lagoon (fish ponds of Arcachon Bay)

The vertical distribution of meiobenthic copepods was investigated within muddy sediments of a eutrophic lagoon (fish ponds of Arcachon Bay, France). The aim of the study was to determine if in muddy sediments, as previously established in sandy sediments, meiobenthic copepods migrate vertically according to the seasons or diel periods. Two experimental approaches were used, viz: a three-season comparison was made of the diel vertical distribution of the harpacticoid Canuella perplexa T. & A. Scott (1893) and secondly the depth distribution of a meiobenthic copepod assemblage was followed for a 24 h period, in shallow water subtidal locations. The harpacticoid C. perplexa vertically migrated through the top three centimeters of the sediment, showing diel and seasonal variations in depth distribution. The differential vertical distributions shown by the dominant meiobenthic populations suggest that emergence into the water column may mainly concern surface dwelling copepods. The physical and biological factors affecting seasonal and diel changes in the copepod assemblage of the fish ponds are discussed.     

Site-to-site variability in abundance of meiobenthic copepods along a tidal gradient over 24 hours

As part of a larger study on the effects of juvenile fish predation on meiobenthic copepods, we collected meiofauna every two hours for 24 hours at three muddy sites along a transect through vegetated marsh, to unvegetated intertidal to unvegetated subtidal habitats. The vegetated marsh (Spartina alterniflora) site harbored significantly more copepods over the combined sampling period than the other two sites. Some species were distributed along the entire transect, but several species were much more abundant at one site than the others. For example, Microarthridion littorale was most abundant at the intertidal site, and Enhydrosoma propinquum was most abundant at the unvegetated sites. The most abundant subtidal species included Pseudobradya pulchella and Paronychocamptus wilsoni. Three species were most abundant in the vegetated marsh (Stenhelia (D.) bifidia, Nannopus palustris, and Diarthrodes aegidius). Maximum total copepod abundance occurred during the daytime low tide at all three sites. Of the four species more abundant in the light than at night, three were subtidal. Most of the time there were no detectable differences between high and low tide abundances, suggesting that there was little exchange of individuals between habitats as tidal levels changed. Without samples from additional transects or the ability to obtain samples for all possible combinations of light and tide levels, we could not detect significant interactions between these two environmental factors. Based upon the species composition of copepods in the gut contents of motile fish predators, the existence of distinct copepod species assemblages at sites along the transect may allow inferences about where fish had fed.Contribution No. 695 from the Bell W. Baruch Institute for Marine Biology and Coastal Research, University of South Carolina.     

Harpacticoid copepods associated with the seagrass Halophila ovalis in the Ashtamudi Estuary,south-west coast of India

A temporal study of harpacticoid copepod populations associated with the seagrass Halophila ovalis was undertaken in the Ashtamudi Estuary, south-west coast of India. A total of 19 species representing 8 families was recorded in this assemblage. Harpacticoids formed 7.52% of the total phytal meiofauna. At the species level, harpacticoids exhibit parallel assemblages with phytal zones, found in other localities.     

Experimental assessment of trophic impacts from a network model of a seagrass ecosystem: Direct and indirect effects of gulf flounder, spot and pinfish on benthic polychaetes

Trophic cascades are predicted to occur when the abundance of predators is increased, directly reducing the abundance of the intermediate prey and indirectly increasing the abundance of the prey at the base of a food web. Mixed trophic impact analysis of a network model developed for Apalachee Bay, near St. Marks, FL, USA predicted such a trophic cascade, in that increased abundance of juvenile gulf flounder Paralichthys albigutta (x¯ = 149 mm SL, effective trophic level 3.9) should have a negative impact on juvenile spot Leiostomus xanthurus (x¯ = 30 mm SL, effective trophic level 2.9) and a positive impact on benthic polychaetes (effective trophic levels 2.3 for deposit feeders and 3.0 for predatory polychaetes) in Halodule wrightii seagrass beds. We tested the predictions of the mixed trophic impact analysis by manipulating the abundance of the high trophic-level species (juvenile gulf flounder) in a cage-exclusion study in the North River, near Harkers Island, NC, USA. We compared the polychaete communities in St. Marks, FL and Harkers Island, NC, and showed that they are 51% similar (Jaccard's Index) at the family level, with the same eight dominant families (Nereidae, Capitellidae, Syllidae, Spionidae, Cirratulidae, Terebellidae, Sabellidae, and Maldanidae) present in both locations. We used 24 open-bottom cages to enclose the benthos and its seagrass-associated animal communities. We manipulated each cage by assigning it to one of the following treatments: (1) inclusion of fishes in upper and intermediate trophic levels (1 juvenile gulf flounder and 10 juvenile spot, the flounder + spot treatment); (2) inclusion of the intermediate predator (10 juvenile spot with no gulf flounder, the spot-only treatment); and (3) no fish added (unmanipulated controls). Core samples taken within the cages provided pre- and post-experimental measures of polychaete density and biomass, and the difference in density and biomass were used as response variables. At the end of the experiment, we collected, weighed, and analyzed the gut contents of all juvenile spot present in the cages. Juvenile pinfish (Lagodon rhomboides, x¯ = 30 mm SL) were present at the end of the study, having arrived as larvae or being trapped during cage set-up, and these fish were also examined, because they also eat polychaetes and their natural densities exceeded our introduced spot densities. Significant differences among treatments were detected for the polychaete family Terebellidae for both the change in density and biomass (pre-experiment − post-experiment). Densities of the Terebellidae changed in the direction predicted by the network model's impact analysis, declining in the cages with spot added compared with the control cages. Analyses of the other response variables (post-experiment spot and pinfish densities and biomass, difference between pre- and post-experiment polychaete densities and biomass for other families, and post-experiment spot and pinfish stomach content biomass) showed no significant differences among treatments. Several variables (Nereidae densities, pinfish densities and biomass, and pinfish stomach content biomass) varied between cages with low and high seagrass cover (significant blocking effect, P < 0.001). Nereidae densities declined significantly in cages with high (73%) rather than with low coverage (31% cover) of seagrass. Pinfish density and biomass were significantly greater in the high seagrass cages at the end of the experiments (P < 0.001), suggesting that dense seagrass attracted them. We conclude that the high density of pinfish in dense seagrass was responsible for the decline in density of the Nereidae. The direct effect of intermediate predators (pinfish feeding on polychaete prey) can be influenced by preferential recruitment of fishes to structurally complex habitats. The direction of change of indirect effects, but not the magnitude, in multi-trophic-level food webs can be predicted by the mixed trophic impact analysis of network models. However, these indirect effects are likely to be small in magnitude relative to direct effects and may be difficult to detect experimentally, especially in low-power experimental caging studies with natural fluctuations in recruitment rates of competitor species.     

Spatial patterns and feeding of meiobenthic harpacticoid copepods in relation to resident microbial flora

Distributional and feeding relationships of harpacticoid copepods and their microbial prey were examined in a tidal channel at Great Sippewissett Marsh. A horizontal zonation of photosynthetic microorganisms was composed of: 1) a diatom area; 2) a purple sulfur bacterial (Thiocapsa sp.) area; and 3) a clear area. Four species of harpacticoid copepods were associated with given areas. Leptocaris brevicornis occurred in very high densities in the diatom area but in relatively low densities in other areas. Mesochra lilljeborgi occurred in significantly higher densities in the purple and clear areas.Feeding experiments, using resident microbial flora labelled with NaH¹⁴CO₃ and ³H-thymidine, were conducted to determine which foods are 1) ingested but simply pass through the gut and 2) ingested, and retained. These experiments indicated that L. brevicornis ingested diatoms and the heterotrophs associated with the diatoms, but only retained the heterotrophic portion. Microscopic examination indicated that diatoms were passed out intact in feces. Oscillatoria sp. (cyanobacterium) was not ingested. Mesochra lilljeborgi ingested Spirulina sp. (cyanobacterium), Thiocapsa sp., and the heterotrophs associated with Thiocapsa but only retained the Thiocapsa label.These data for harpacticoids suggest that spatial distributions of meiofauna may be closely coupled with microbial food organisms which they consume. Also, that while several microbial foods may be ingested, only certain microbes are digested and assimilated as a food resource, further indicating the complexity of feeding relationships among the meiofauna.     

Spatial scale and meiobenthic copepod recolonisation: testing the effect of disturbance size in a seagrass habitat

A central problem in relating disturbance to community structure lies in determining how community structure is affected by the size of disturbance events. In soft-bottom habitats, recovery rate and patterns of macrobenthic community are usually affected by the spatial scale of disturbance. Thus far, no studies have explicitly addressed these issues for meiobenthic copepods. To test the effects of the size of hypoxia/anoxia disturbance on the recovery of meiobenthic copepod communities in a vegetated (Ruppia cirrhosa) sediment, a field experiment was set up in Valle Smarlacca, a brackish lagoon on the northern Adriatic coast of Italy. Plots of three different sizes—small (40×40 cm), medium (80×80 cm) and large (160×160 cm)—were exposed to experimentally induced hypoxia/anoxia for 5 days. Control plots of 40×40 cm were added, for comparison with ambient abundance. Recolonisation and community recovery were then observed for 12 days, with samplings on days 0, 1, 3, 5, 7, 9 and 12. Sampling was designed to focus on the distance from source pools of colonists. The induced anoxia had a severe impact on the copepods, but the impact of the disturbance was independent of plot size. Copepod abundance increased linearly over time, and no differences in recolonisation rate among the differently sized plots were observed. Recolonisation comprised two phases: until day 3, abundances were low and very similar in all plot sizes; from day 5 onwards, abundances of the dominant species (which were the same in control and disturbed plots) increased, and a more diversified pattern among disturbance sizes was observed. Multivariate analyses showed a gradual response of community structure to disturbance size: copepod assemblages in small plots attained the same structure of the control plots at day 5, while for larger-sized plots this occurred later and was observed on the following sampling date. However, clear differences among the three disturbance sizes were never detected. Variability in community structure seemed to respond more to the overall impact of disturbance than to the size of the disturbed area. In the seagrass meadows of the Valle Smarlacca, several factors seem to influence the structural organisation of meiobenthic copepod communities during recolonisation processes. Among others, the recovery of the vegetated habitat to suitable conditions seems to play a much more relevant role than the size of the disturbed patches.     

A pedal corer for the quantitative sampling of sediments and benthic organisms in submerged areas accessible on foot

This paper presents a new device to collect quantitative samples of sediment and benthic organisms. The device is specially designed for sampling with the advantages of box-corer or Eckman dredges in submerged areas that are accessible on foot. The pedal corer is a simple, lightweight, user-friendly device that does not disturb the sediment structure and provides easy access to the sample contained inside the core. With this device, sampling in shallow water zones that are constantly submerged is made easy and sampling time is extended in intertidal zones. Handling editor: J. Saros     

The role of phototrophic sulfur bacteria as food for meiobenthic harpacticoid copepods inhabiting eutrophic coastal lagoons

Laboratory experiments were undertaken using Amonardia normani and Schizopera cf. compacta, two meiobenthic harpacticoid copepods commonly found in coastal lagoons. The first experiments were designed to determine if the phototrophic sulfur bacteria Chromatium gracile can be ingested by these copepods and at what concentrations. Egestion rate was used as an index of feeding rate. The response of the egestion rate, expressed in numbers of faecal pellets produced by copepod per day, as a function of bacterial concentration followed the functional model. A. normani attained constant feeding rates from the bacterial concentration of 1 × 10⁷ cells ml^–1 (5 µg C ml^–1) onwards, S. cf. compacta attained constant feeding rates from 2.6 × 10⁷ cells ml^–1 (13 µg C ml^–1) onwards. The faecal pellet volume changed significantly (p<0.05) between food concentrations for A. normani but not for S. cf. compacta (p>0.05). In order to investigate the effect of the phototrophic bacterial diet on the population dynamics of A. normani three groups of nauplii were maintained at 2 × 10⁷ cells ml^–1 and observed every day. The mortality of these nauplii was very high compared to those maintained on a diatom diet (Nitzschia constricta); only in one of the groups did some copepodites develop but no adults were ever observed. Adults fed on bacteria did not have different (p>0.05) survival rates compared to those fed on diatoms, nevertheless, the number of nauplii produced was significantly less (p<0.05) on the bacterial diet. These results lead us to suggest that although the phototrophic sulfur bacteria (Chromatium gracile) can be ingested by both copepod species it cannot sustain the full development of the A. normani population. Thus, a bloom of phototrophic sulfur bacteria does not seem to be a favourable situation for opportunistic benthic copepods to colonize eutrophic coastal lagoons after a dystrophic crisis.     

The integral structure of a benthic infaunal assemblage

It has been suggested that the scaling relationships of many features of the physical environment and biological traits are fractal-like, but for the marine benthic infauna certain aspects of the environment clearly are not. These include temporal features such as the cycles of annual climate, primary production and tides, and also some spatial features such as sediment granulometry and the size of the primary producers that constitute the food supply. We explicitly addressed these issues by determining the degree to which infaunal assemblage structure (diversity, species composition, spatial pattern) varies with mesh size, sample size and sample dispersion within an apparently homogeneous area of coarse intertidal sand in the Isles of Scilly, UK. Samples were extracted using a standard range of 5 mesh sizes (63, 125, 250, 500, 1000 μm), with the sample areas and distances between samples scaled to the mesh size. All metazoans were identified to species level. Diversity and species composition did not show a gradual and even degree of change over the size range. Instead, they showed a dramatic stepwise change between the 250 and 500 μm mesh size samples, being relatively constant in the < 500 and > 500 μm categories, with diversity higher in the former. Higher proportions of species in the < 500 μm categories had values of an index of dispersion significantly different to 1 than among species in the > 500 μm categories. This suggests a fractal structure within but not between the < 500 and > 500 μm body size categories. The implications of this for rapid diversity assessment by extrapolation between size classes are discussed. Although the interplay between 3 and 2 dimensional processes in what is a essentially a 2-D study may account for some of the observations, comparative studies suggest that these patterns do not simply correspond to the physical scaling of habitat complexity, and they must therefore relate to some more universal scaling relationships that are not fractal-like. We suggest that the important relationships are those between body size and various biological characteristics such as feeding behaviour, reproductive mode and life history as they are affected by the spatial and temporal structure of the environment.     

Effects of a macroalgal mat (Ulva lactuca) on estuarine sand flat copepods: an experimental study

The effects of a macroalgal mat (Ulva lactuca) on intertidal sand flat copepods were studied in Jamaica Bay, NY. In 1999, Ulva was removed from paired quadrats in the algal mat. Density and species richness were estimated from sediment cores over seven biweekly periods and compared with Ulva-removal quadrats and with an unvegetated reference site. In a separate analysis at the same site, species composition and density of all copepods within the algal mat were determined from replicated quadrat samples over seven dates. Emergence traps were deployed in all treatments in 1999 to quantify copepod movements from sediments into the water column during flooding tide. Dissolved oxygen (DO) was continuously monitored over several 96-h periods in and above the algal mat. In 2000, three biomass levels of Ulva (0, 100, 200 g DW per m²) were added to paired quadrats in the unvegetated zone. Density and species richness were estimated over eight time periods. Ulva removal resulted in significant increases in density and species richness, but levels remained lower than at the unvegetated site. Likewise, addition of Ulva biomass produced significant declines in copepod density. However, the differences between low- and high-Ulva-addition treatments were insignificant. Increases in phytal copepods after Ulva addition did not compensate for losses of epibenthic and infaunal species. The overall effect of the Ulva mat was a net loss of copepod density, including the loss of nearly all infaunal species. Anoxia in sediments and within the algal mat are correlated with declines in infaunal species and with escape by some infaunal species from the sediment into the water column.     

Hyperspectral discrimination of coral reef benthic communities in the western Caribbean

Determining a subset of wavelengths that best discriminates reef benthic habitats and their associated communities is essential for the development of remote sensing techniques to monitor them. This study measured spectral reflectance from 17 species of western Caribbean reef biota including coral, algae, seagrasses, and sediments, as well as healthy and diseased coral. It sought to extend the spectral library of reef-associated species found in the literature and to test the spectral discrimination of a hierarchy of habitats, community groups, and species. We compared results from hyperspectral reflectance and derivative datasets to those simulated for the three visible multispectral wavebands of the IKONOS sensor. The best discriminating subset of wavelengths was identified by multivariate stepwise selection procedure (discriminant function analysis). Best discrimination at all levels was obtained using the derivative dataset based on 6–15 non-contiguous wavebands depending on the level of the classification, followed by the hyperspectral reflectance dataset which was based on as few as 2–4 non-contiguous wavebands. IKONOS wavebands performed worst. The best discriminating subset of wavelengths in the three classification resolutions, and particularly those of the medium resolution, was in agreement with those identified by Hochberg and Atkinson (2003) and Hochberg et al. (2003) for reef communities worldwide. At all levels of classification, reflectance wavebands selected by the analysis were similar to those reported in recent studies carried out elsewhere, confirming their applicability in different biogeographical regions. However the greater accuracies achieved using the derivative datasets suggests that hyperspectral data is required for the most accurate classification of reef biotic systems.     

Colonisation and bioerosion of experimental substrates by benthic foraminiferans from euphotic to aphotic depths (Kosterfjord, SW Sweden)

In the cold-temperate setting of the Swedish Kosterfjord area, experimental carbonate and PVC substrates were deployed for a 6, 12 and 24-month duration along a transect from euphotic to aphotic depths in order to study bioerosion and carbonate accretion patterns. Among the organisms that contribute to the latter by secreting calcareous skeletons, epibenthic foraminiferans represent a major component, both in terms of diversity (a dozen species) as well as in the number of individuals (exceeding 50,000 individuals per m² at certain depths). The by far dominating species were found to be Cibicides lobatulus and the agglutinating Lituotuba lituiformis, along with smaller numbers of Planorbulina mediterranensis, Tholosina vesicularis and Nubecularia lucifuga. The foraminiferal distribution exhibits a pronounced abundance maximum in shallow waters at 7 and especially 15 m and a maximum in diversity at 15-50 m water depth. Some of the foraminiferans encountered, such as Cibicides lobatulus and the rare Gypsina vesicularis, were found to contribute also to the bioerosion of the calcareous substrates by etching shallow attachment scars. These prominent traces witness the former presence of benthic foraminiferans on fossil to Recent hardgrounds, inferring a potential applicability as an in situ proxy where tests are not preserved. Estimated minimum carbonate production rates for the dominant Cibicides lobatulus reach a maximum of 0.326 g/m²/year with the highest rates occurring at 7 to 30 m water depth. Carbonate production rates are up to two magnitudes higher on the PVC (0-0.326 g/m²/year) than on the carbonate substrates (0-0.010 g/m²/year) and are considerably higher than estimates previously reported from the western Baltic.     

The behavioural responses and tolerance of freshwater benthic cyclopoid copepods to hypoxia and anoxia

The response of four benthic cyclopoid copepods,Acanthocyclops viridis (Megacyclops viridis) (Jurine, 1820),Macrocyclops albidus (Jurine),Eucyclops agilis (Koch, Sars) (Eucyclops serrulatus) (Fischer, 1851) andParacyclops fimbriatus (Fischer), to hypoxia and anoxia was investigated. All of these species died within six hours when confronted by totally anoxic conditions, but all survived four days at oxygen saturation levels as low as 25%. Males succumbed to the effects of anoxia more rapidly than the larger females of each species, and larger species survived for shorter periods than smaller species. In artificially stratified columns, where the lower layer was anoxic, all four species displayed an upward migratory response towards oxygenated conditions. Where the artificial hypolimnion was hypoxic, however, the migratory response was not observed. The results suggest that some benthic copepods cope with seasonal anoxia in eutrophic stratified lakes by migration rather than the various physiological adaptations shown by planktonic and semi-planktonic species.     

Closing the larval loop: linking larval ecology to the population dynamics of marine benthic invertebrates

The majority of marine benthic invertebrates exhibit a complex life cycle that includes separate planktonic larval, and bottom-dwelling juvenile and adult phases. To understand and predict changes in the spatial and temporal distributions, abundances, population growth rate, and population structure of a species with such a complex life cycle, it is necessary to understand the relative importance of the physical, chemical and biological properties and processes that affect individuals within both the planktonic and benthic phases. To accomplish this goal, it is necessary to study both phases within a common, quantitative framework defined in terms of some common currency. This can be done efficiently through construction and evaluation of a population dynamics model that describes the complete life cycle.

Two forms that such a model might assume are reviewed: a stage-based, population matrix model, and a model that specifies discrete stages of the population, on the bottom and in the water column, in terms of simultaneous differential equations that may be solved in both space and time. Terms to be incorporated in each type of model can be formulated to describe the critical properties and processes that can affect populations within each stage of the life cycle. For both types of model it is shown how this might be accomplished using an idealized balanomorph barnacle as an example species. The critical properties and processes that affect the planktonic and benthic phases are reviewed. For larvae, these include benthic adult fecundity and fertilization success, growth and larval stage duration, mortality, larval behavior, dispersal by currents and turbulence, and larval settlement. It is possible to predict or estimate empirically all of the key terms that should be built into the larval and benthic components of the model. Thus, the challenge of formulating and evaluating a full life cycle model is achievable. Development and evaluation of such a model will be challenging because of the diverse processes which must be considered, and because of the disparities in the spatial and temporal scales appropriate to the benthic and planktonic larval phases. In evaluating model predictions it is critical that sampling schemes be matched to the spatial and temporal scales of model resolution.     

Low natural repopulation of marginal coral communities under the influence of upwelling

The study of coral repopulation in marginal communities may provide a useful analog for understanding the dynamics of coral reefs subjected to deleterious environmental changes. Repopulation of scleractinian reef corals may strongly impact the community structure on tropical reefs; however, the extent of this process on coral communities influenced by upwelling is unknown, especially in the Caribbean. In this study, the potential for natural repopulation of coral communities subjected to wind-driven upwelling was evaluated at three sites on the island of Cubagua, Venezuela. Coral spawning behavior was recorded and both larval settlement and juvenile abundance were estimated. Upwelling did not appear to affect coral spawning behavior, since at this locality spawning occurred at dates and times similar to those reported for well-developed reefs in the Caribbean. Also, juveniles produced by brooding corals were six times more abundant than those of broadcasting species, similar to patterns on other Caribbean reefs that are not under the influence of upwelling. By contrast, mean larval settlement (4 settlers m⁻²) and juvenile abundance (0.1 juveniles m⁻²) in Cubagua were both lower than those elsewhere in the Caribbean and on Pacific reefs. Thus, the potential for repopulation of these marginal communities seems lower than for well-developed coral reefs in other regions. These results suggest that more fully developed coral reefs also may have reduced repopulation potential, as they become influenced by suboptimal environmental conditions. Handling editor: I. Nagelkerken     

Differentiation of benthic marine primary producers using stable isotopes and fatty acids: Implications to food web studies

A two-dimensional biomarker approach, using stable isotopes (δ¹³C, δ¹⁵N) and fatty acids, was used to evaluate differences both amongst and within benthic primary producer types (seagrass, fleshy red algae, calcareous red algae, brown algae, and seagrass periphyton) that are typical of the nearshore, temperate Australian region. The primary source of variance (as examined by permutational ANOVA) for all biomarkers examined was amongst primary producer types, as opposed to amongst species within type. δ¹³C showed a clear separation (Monte Carlo p < 0.05) between seagrass (range of means = −10.1 to −14.0‰) and macroalgae (−14.6 to −25.2‰), but could not differentiate amongst the algal types examined. Similarly, distinct δ¹⁵N signatures (p < 0.05) were found only for seagrass (range of means = 3.6-4.1‰) versus calcareous red algae (4.6-5.5‰), with all other types overlapping in their mean δ¹⁵N values. In contrast, multivariate analysis of fatty acid data (using Canonical Analysis of Principal coordinates; CAP) distinguished not only between seagrass and macroalgae, but also between red and brown algae (and to a limited extent between the calcareous and fleshy red algal types). The principal unsaturated fatty acids in the samples were C₂₀ polyunsaturates (found primarily in the macroalgae and periphyton), and C₁₈ mono- and polyunsaturates, with high proportions of 18:2n-6 and 18:3n-3 typical of the seagrasses. The C₁₈ monounsaturate 18:1n-7 was one of the most diagnostic compounds for the red algae examined, being present in very low amounts in seagrass and virtually absent in the brown algae. Conversely, brown algae were high in 18:4n-3, with 20:4n-3 particularly diagnostic of the kelp Ecklonia radiata. In contrast to stable isotopes, fatty acids helped distinguish different algal groups, thereby providing support that a two-dimensional approach using stable isotopes and fatty acids is likely to provide the most useful tool to distinguish primary producers in food web structure.     

Experimental evidence of predation by juvenile flounder, Platichthys flesus, on a shallow water meiobenthic community

In the northern Baltic Sea juvenile flounder, Platichthys flesus, occur in high abundances on shallow sandy bottoms in late summer and autumn. They feed mainly on meiofauna and the ontogenetic switch to macrofaunal sized food occurs at a larger size here than in other areas, exemplifying the high relative importance of meiofauna. Consequently, juvenile P. flesus in the Baltic feed for a longer period on meiofauna, and could thus be expected to have a stronger predation effect on the meiofaunal assemblages. In this study the predation effects of juvenile P. flesus on meiofaunal abundances and community structure were studied using microcosms that were sampled repeatedly over a 3-week period. Significant differences between treatment and control were found for the total number of taxa, for abundances of harpacticoids, copepod nauplii and ostracods. The nematode community was not affected, but one genus, Axonolaimus, was negatively affected by predation. The predation affected meiofaunal community structure as the major taxon diversity was significantly reduced. The results suggest that the meiofauna on shallow sandy bottoms may be structured by juvenile P. flesus, and the combined predation pressure of juvenile flounder and other epibenthic predators in the area might be considerable. Microcosms are effective in testing natural predation, especially on meiofaunal communities, but field experiments should be conducted to account for the physical characteristics of the area studied.     

A review of current proteomics technologies with a survey on their widespread use in reproductive biology investigations

Proteomics is very much a technology-driven field. The ambition is to identify, quantify and to assess the state of posttranslational modification and interaction partners for every protein in the cell. The proteome is in a state of flux and is thus extremely complex. Analysis of the proteome is exacerbated by the huge dynamic concentration range of proteins in the cellular environment. The impact that mass spectrometry-based proteomics has had on the field of biology has heavily depended on dramatic improvements in mass spectrometry that have been made in recent years. We examined 1541 reports indexed in PubMed relating to proteomics and reproduction to identify trends in the field and to make some broad observations for future work. To set the scene, in the first part of the report, we give a comprehensive overview of proteomics and associated techniques and technologies (such as separations and mass spectrometry). The second part examines the field in light of these techniques and suggests some opportunities for application of these tools in the area of reproduction.     

Experimental investigations of 211Am accumulation by macrophytes of the Yenisei River

Experiments were carried out in which 241Am was added to water samples containing macrophytes of the Yenisei River, and the radionuclide absorption rates and concentration factors were determined for the plants. It has been shown that the water moss (Fontinalis antipyretica) has a higher capacity to accumulate 241Am than the Canadian pondweed (Elodea canadensis) does. The laboratory experiments revealed that the capacity of dead biomass of the Canadian pondweed to accumulate 241Am is twice higher than that of living biomass. In contrast, no significant increase in 241Am accumulation by dead biomass of the water moss has been recorded. The transuranic element 241Am was firmly fixed by the plant biomass and was not released into water in the course of long-duration experiments.