ALBERT

Description: A study of the diet of Sepia officinalis and S. elegans in the Ria de Vigo has shown that crustaceans are the most abundant prey in both species, followed by fish. Changes in the food composition of both species occur with growth. The type of prey eaten by the two sexes of these species is very similar. The possibility of trophic competition between juveniles of S. qficinalis and S. elegans is discussed.

Description: Natural communities are constantly changing due to a variety of interacting external processes and the temporal occurrence and intensity of these processes can have important implications for the diversity and structure of marine sessile assemblages. In this study, we investigated the effects of temporal variation in a disturbance regime, as well as the specific timing of events within different regimes, on the composition and diversity of marine subtidal fouling assemblages. We did this in a multi-factorial experiment using artificial settlement tiles deployed at two sites on the North East coast of England. We found that although there were significant effects of disturbances on the composition of assemblages, there were no effects of either the variation in the disturbance regime or the specific timing of events on the diversity or assemblage composition at either site. In contrast to recent implications we conclude that in marine fouling assemblages, the variability in disturbance regimes (as a driving force) is unimportant, while disturbance itself is an important force for structuring robust ecosystems.

Description: Archived scales and otoliths constitute a unique source of DNA that potentially enables extension of the temporal scale of genetic studies of fish populations by decades and even centuries. We review recent insights into fish population and conservation genetics obtained using analysis of DNA from archived samples. This involves both new knowledge about demographic parameters and population structure in wild populations and insights into consequences of anthropogenic pressure resulting from over-harvesting, habitat degradation and stocking. We show that the latter category of studies have led to significant changes of management practices. Ongoing improvement of genetic methods will undoubtedly further expand the ability to utilize historical DNA samples. We envisage that temporal comparisons of large numbers of coding genes will lead to novel insights into selective responses of fish populations to anthropogenic challenges, particularly fisheries-induced selection and global warming. However, both acquisition and storage of historical DNA samples can be hurdles to temporal genetic analyses, while degradation and low copy number in historical DNA samples render genetic data from such sources prone to technical artefacts. We summarize recommendations for storage of samples and DNA extraction and provide checklists for validation of genotyping results. Finally, we stress that validation procedures also involve documentation of the time and population of origin of historical samples, and the inferences drawn should account for the technical and statistical uncertainties associated with historical DNA analysis.

Description: Intra‐plate volcanism in western Europe shows statistically significant episodicity during the Quaternary period. By comparing the known ages for eruptions in France and Germany, which are compiled here, with a composite oxygen isotope record, we have investigated the link between this episodic volcanism and the climate record over the last two million years. We show that increased volcanism between 415–400 ka and 17–5 ka correlates with warming phases at the end of the last Weichselian (Devensian) and earlier Elsterian (Anglian) glacial stages. The three significant caldera explosions in the eastern Eifel, Germany, are all associated with warming phases at the onset of interglacials. The growth and decay of nearby ice sheets suggest that surface changes in continental mass distribution during glacial Milankovich cycles could provide a mechanism for this correlation by means of the distal effects of flexural loading on the lithosphere.

Description: An analysis of mass (M) and standard length (LS) data for larval, juvenile and adult sprat (Sprattus sprattus; Clupeidae) revealed marked changes in the allometric scaling factor (b in inline image). For sprat 〈44 mm LS, b was 5·0, whereas in larger juveniles and adults, b was c. 3·4 indicating a relatively protracted metamorphic period for this species.

Description: To investigate and disentangle the role of major histocompatibility complex (MHC)‐based ‘good genes' and ‘compatible genes' in mate choice, three‐spined sticklebacks Gasterosteus aculeatus with specific MHC IIB genotypes were allowed to reproduce in an outdoor enclosure system. Here, fish were protected from predators but encountered their natural parasites. Mate choice for an intermediate genetic distance between parental MHC genotypes was observed, which would result in intermediate diversity in the offspring, but no mate choice based on good genes was found under the current semi‐natural conditions. Investigation of immunological variables revealed that the less‐specific innate immune system was more active in individuals with a genetically more divergent MHC allele repertoire. This suggests the need to compensate for an MHC‐diminished T‐cell repertoire and potentially explains the observed mate choice for intermediate MHC genetic distance. The present findings support a general pattern of mate choice for intermediate MHC diversity (i.e. compatible genes). In addition, the potentially dynamic role of MHC good genes in mate choice under different parasite pressures is discussed in the light of present and previous results.

Description: Individual behaviour of Atlantic cod Gadus morhua in the presence of hypoxic water was measured in situ in the vertically stratified Bornholm Basin of the Baltic Sea. Considering all recaptured individuals, the use of hypoxic habitat was comparable to data derived by traditional survey data, but some G. morhua had migrated towards the centre of the c.100 m deep basin and spent about a third of their time at oxygen saturation 〈50%, possibly to forage on zoobenthos. Maximal residence time per visit in such hypoxic water was limited to a few hours, allowing for the digestion of consumed prey items in waters with sufficient dissolved oxygen.

Description: The seasonal growth trajectories of wild Atlantic salmon Salmo salar juveniles by age group within the Margaree River, Canada, are described. Circuli counts from scales were used to infer growth rates at different ages and these were used to predict the proportions of age 2‐ and 3‐year old smolts from different portions of the watershed. In the wild Atlantic salmon juveniles from the Margaree River, there was no bimodality in fork length frequencies and no 1 year old smolts were produced. Water temperature differences during the growing season were insufficient to explain the differences in growth rates and size at age among the sites sampled. There was a positive association between the growth rate in the first year and the subsequent age at smoltification. In the Margaree River, differences in tributary specific growth rates and size at age were expected to produce important differences in the relative ages at smoltification.

Description: Speciation and the maintenance of recently diverged species has been subject of intense research in evolutionary biology for decades. Although the concept of ecological speciation has been accepted, its mechanisms and genetic bases are still under investigation. Here, we present a mechanism for speciation that is orchestrated and strengthened by parasite communities acting on polymorphic genes of the immune system. In vertebrates, these genes have a pleiotropic role with regard to parasite resistance and mate choice. In contrasting niches, parasite communities differ and thus the pools of alleles of the adapted major histocompatibility complex (MHC) also differ between niches. Mate choice for the best‐adapted MHC genotype will favour local adaptations and will accelerate separation of both populations: thus immune genes act as pleiotropic speciation genes –‘magic traits’. This mechanism should operate not only in sympatric populations but also under allopatry or parapatry. Each individual has a small subset of the many MHC alleles present in the population. If all individuals could have all MHC alleles from the pool, MHC‐based adaptation is neither necessary nor possible. However, the typically small optimal individual number of MHC loci thus enables MHC‐based speciation. Furthermore, we propose a new mechanism selecting against species hybrids. Hybrids are expected to have super‐optimal individual MHC diversity and should therefore suffer more from parasites in all habitats.

Description: Human activities have differentially altered biogeochemical cycling at local, regional and global scales. We propose that a stoichiometric approach, examining the fluxes of multiple elements and the ratio between them, may be a useful tool for better understanding human effects on ecosystem processes and services. The different scale of impacts of the elements carbon, nitrogen and phosphorus and the different nature of their biogeochemical cycles, imply a large variation of their stoichiometric ratios in space and time and thus divergent impacts on biota. In this paper, we examine the effects of anthropogenic perturbations on nutrient ratios in ecosystems in two examples and one case study. Altered stoichiometry in agricultural systems (example 1) can affect not only crop yield and quality but also the interactions between plants and their pollinators, pests and pathogens. Human activities have also altered stoichiometry in coastal ecosystems (example 2). Increased N loading has especially lead to increased N:P and reduced Si:N ratios, with detrimental effects on ecosystem services derived from coastal pelagic food webs, such as fish yield and water quality. The terrestrial–aquatic linkage in stoichiometric alterations is illustrated with a case study, the Mississippi River watershed, where anthropogenic activities have caused stoichiometric changes that have propagated through the watershed into the northern Gulf of Mexico. Coupled with altered stoichiometric nutrient inputs are the inherent differences in variation and sensitivity of different ecosystems to anthropogenic disturbance. Furthermore, the connections among the components of a watershed may result in downstream cascades of disrupted functioning. Applying a multiple element perspective to understanding and addressing societal needs is a new direction for both ecological stoichiometry and sustainability.

Description: Frequent collections were made of the marine planktonic copepod Temora longicornis and a series of measurements made to determine the level of nitrogen excretion in this copepod. An algal diet consisting of the marine diatoms Skeletonema and Thalassiosira labelled with 14C was provided in the laboratory. Both excreted ammonia nitrogen and amino nitrogen were measured, as was the total nitrogen in the copepods. The copepods were kept for a maximum of one day and excretion measured one hour after feeding. Oxygen consumption was measured as an indicator of metabolic rate and as a basis for calculations of the O:N ratio and estimations of the efficiency of nitrogen utilisation.

Description: Uptake data of seven sugars (mono- and disaccharides) were used to calculate DOC-turnover and microbial biomass production. The sugars investigated in this study represent 1-2% of the DOC and up to30 % of the free dissolved carbohydrates. The uptake measurements were not based on a kinetic approach. Uniformly labelled 14C-carbohydrates were added to the samples, the concentrations reaching maximally 10% of the corresponding natural substrate concentration. Taking the natural substrate concentration into account, it is possible to calculate the actual uptake rates, turnover times and microbial C-production. An investigation in the Kiel Fjord during 1978/79 shows turnover times for glucose between 1.7 and 600 hours. The microbial biomass production varies between 0.01 and 10 μg C l-1 h-1, i.e. 0.2 - 83% of the primary production. The ratio between incorporation and gross uptake is between 0.62 and 0.95, which supports the assumption that free dissolved carbohydrates are biochemically wellutilized substrates. The relation to exudates is discussed.

Description: In vitro and in situ several macrobenthic species were found to show highest uptake rates of amino acids at low temperatures of 0°-10° C. The rates decreased at a higher temperature of 15° C which favoured the activity and the development of microorganisms. However, the significance of competitive microorganisms was less striking in the in situ experiments than under laboratory conditions. Phenylalanine was most readily taken up although "aufwuchs" of Fucus serratus and Gammarus sp. was found to show primary uptake of aspartic acid. Arthropods were also able to take up dissolved amino acids but in much lower quantities than molluscs and polychaetes. Dissolved amino acids in the water column hardly penetrated the sediment if this was covered by a layer of detritus.

Description: The primary production, quantity and molecular weight distribution of DOC released by phytoplankton, and the subsequent utilization and transformation of these compounds by bacteria in an estuary was studied. High primary production rate and DOC release was observed. The amount and composition of DOC released by phytoplankton aried with time and changing algal population. Low molecular weight products with MW less than 500, fraction with MW 10000 - 30000, and high molecular weightcompounds greater than 300000 dominated in the algal DOC. Bacteria utilized a significant portion of released DOC. The role of bacteria in the transformation of released DOC by algae is discussed.

Description: Field manipulative cage experiments were performed on an unvegetated shallow water mudflat in the eutrophicated inner Oslo fjord. Exclosure and enclosure cages each covering an area of 0.6 m2, were maintained on the mudflat to protect infauna from epibenthic macropredators in general and for exposing the infauna to different densities of the common goby, Pomatoschistus microps, a common predator in the area. Predation effects were determined by comparing faunal composition and abundance inside and outside the cages after 2 1/2 months. Irrespective of the number of gobies in the cages only minor differences in faunal composition and abundance were found between cage and control. lt is therefore concluded that epibenthic macropredators in general and P. microps in particular do not crop infauna to an extent sufficient to alter faunal composition and to reduce abundance discernibly.

Description: During the Second German Antarctic Expedition 24 stations were visited from Januarv to February 1978 between Bellinghausen Sea and South Georgia. Samples were taken for the determination of phytoplankton composition and biomass as well as for protozooplankton biomass. Primary productivity was measured as 14C-uptake for different size classes of the phytoplankton population (〈 20, 20-100 and 100-300 μm). Remarkable was the distribution of biomass and primary production within the different phytoplankton size classes. At nearly all stations the major part of the, biomass consisted of nanoplankton forms smaller than 20 μm which were responsible for about 90 % of the production. These tiny organisms were either diatoms (centric or pennate forms), μ-flagellates or dinoflagellates, thus representing the main phytoplankton groups. Protozooplankton cells were found at all stations, their biomass averaged about 16% of the phytoplanktion biomass. The obvious importance of nanoplankton forms as a food supplier for the krill (Euphausia superba) as well as the importance of protozooplankton as a food source and a food competitor for the krill during the Australian autumn are discussed.

Description: A study on the macroplankton community in Kosterfjorden, Western Sweden, is used to introduce a term called Index of population energy-flow, lpef. This term is defined as the ratio between the energy flow (consumption) through a specific population and the flow through the whole trophic level to which the species belongs. For simplicity, the study is restricted to 6 herbivorous and omnivorous species and 7 carnivorous species. Values for the production, respiration, and excretion are calculated from published data and are presented as means for each of the four seasons. On an annual basis between 8 and 52 % of the assimilated energy is bound in production, between 30 and 85% is used in respiration, and between 6 and 32% is excreted. the estimated grazing pressure of the 6 herbivorous/omnivorous species is relatively low compared with the estimated primary production, especially during spring and summer, indicating that most of the primary production goes directly to the benthic community. The copepod Calanus finmarchicus has the highest index of population energy-flow among herbivorous/omnivorous species with an annual mean of 87% and seasonal maximum in autumn (lpef = 96%). The copepod Metridia longa is most important in spring (lpef = 16%) and the three euphausiid species in summer (lpef = 4-5%). Among carnivores the copepod Chiridius armatus has the highest annual mean value (lpef = 43%) with seasonal maximum in spring (lpef = 65%). Small chaetognaths are most important in autumn (lpef = 18%) and the polychaete Tomopteris helgolandica and the trachymedusa Aglantha digitale in winter (lpef = 33 % and 17%, respectively).

Description: Results obtained from short-term (8 h to 24 h intervals) measurements of physical, chemical and biological properties of the 70 m water column from an anchor station in the Bornholm Sea over a 10-day period are presented and discussed. Phytoplankton biomass concentration and production rates indicated that the spring bloom was in progress in this period. The onset of the spring bloom occurred prior to the advent of thermal stratification. Peak growth rates, accompanied by nutrient depletion and biomass accumulation in surface layers, were concomitant with calm weather and a cloudless sky after which a part of the population was observed to sink out of the water column unimpeded by the permanent halocline. Maximum sinking rates of the dominant species, Skeletonema costatum, ranged between 30 to 50 m per day during this event. The development of the spring bloom apparently takes place in a series of events during which periods of low production alternate with periods of high production and rapid sedimentation of parts of the population.

Description: Every fourth hour in 24 h periods measurements were made of temperature, salinity, plant nutrients, incident radiation at three m depth, sub-surface light extinction, chlorophyll a, phaeophytin, particulate carbon and nitrogen, cell counts, zooplankton dry weight biomass, in situ primary production (14C), incubator carbon assimilation (14C), heterotrophic activity (14C glucose assimilation), and horizontal variation in chlorophyll a over one nautical mile. The marked variations in all parameters were probably generated by the combined effects of wind-driven circulation of water masses in the fjord and phytoplankton patches. This study stresses the presence of spatial and temporal changes in fjords, and that data conducted from one or few stations should be interpreted with care.

Description: Aspects of the inter-relationship of krill Sound Scattering Layers (SSLs) and fish were examined in Ullsfjorden and Øksfjorden, northern Norway from 2 - 8 February 1980. Diel changes in the depth distribution and biomass of krill (Euphausiacea) were compared with the depth distribution and abundance of gadoid fish using a pelagic capelin trawl, 38 and 120 kHz echosounders, and a digital echointegrator. Krill underwent vertical migrations from the surface at night to the fjord bottom at mid-day. A significant power curve relationship was found when catches of krill in the pelagic trawl (l·trawl h-1) were compared with volume backscattering (dB m-3) at 120 kHz, indicating that krill biomass can be reliably estimated using acoustic techniques. Krill were the dominant food item of fish caught with the pelagic trawl in the SSLs. Fish were nevertheless rare in these krill SSLs; the majority congregated under them, probably feeding extensively at their periphery. Interactions between krill and pelagic feeding gadoids in north Norwegian fjords are examined.

Description: The early summer dynamics of major zooplankton populations in Helgoland Bight are discussed on the basis of the GILLBRICHT extension of LIEBIG's law of the minimum. On the basis of monofactorial control of population dynamics, copepod decline in June is caused by predation of Pleurobrachia pileus, phytoplankton never being at levels which would starve copepods. Copepod recovery is correlated with the control of Pleurobrachia pileus by Beroe gracilis, an exclusive predator on this tentaculate ctenophore. By controlling copepods before they can seriously deteriorate the phytoplankton standing stock, high phytoplankton summer levels are possible which characterize the rich ecosystem of Helgoland Bight.

Description: The behaviour and distribution of Palaemon debilis Dana was studied in mangrove lagoons along the east coast of Sinai. Food intake and growth of this prawn were measured in the laboratory and compared with the related Atlantic species Palaemon elegans Rathke, occuring in a saltwater fishpond at Elat. Daily food intake was similar in both species and correlated with their metabolic weight. By feeding groups of prawns different rations of prawnmeat during fourteen days the daily maintenance ration was estimated as approximately 14 percent of the metabolic dry weight while the net food conversion was estimated as 0.4. The role of Palaemon debilis in the mangrove toodweb is discussed.

Description: In situ enrichment bioassays were performed during the summers of 1978 and 1979 in the Falsterbo Channel, south Baltic Sea. Phosphorus and/or nitrogen was added daily for up to two weeks to 200 l polyethylene bags with unfiltered surface water. Additions of nitrogen or nitrogen plus phosphorus invariably increased the biomass and 14C fixation of phytoplankton. Phosphorus additions had no such effects. Phytoplankton species which reacted most strongly to the enrichment were Aphanothece sp., Nodularia spumigena, Skeletonema costatum, Nitzschia closterium, Chaetoceros wighami and Oocystis sp. The mean C/Chl a quotient was around 70 for chlorophyll a values below 6 mg· m-3 but decreased to about 30 for chlorophyll a values above 10.

Description: Energy flow and material cycling in aquatic environments can be conceptualized in terms of food webs, linking various taxonomic or functional biological compartments and their physical environment. Interpretation of empirical data and finally a functional understanding of the system studied requires a high degree of abstraction and aggregation. The complexity and variability of environmental systems, the scarcity of appropriate observations and experiments, and the lack of a weil established theoretical background make it difficult to test any possible conceptualization, or hypothesis, describing a given system. A formal approach to hypothesis testing, based on numerical simulation, which explicitly considers the above constraints, is proposed. Based on a data set from the North Sea, a series of hypotheses on the structural relations and the dynamic function of the pelagic food web is formulated in terms of numerical models. Hypotheses of various degrees of aggregation and abstraction are tested by comparing singular statements (predictions) deduced from the proposed hypotheses (the models) with the observations. The basic processes of primary production, consumption, and remineralization, driven by light, temperature, and advection/diffusion, are described in systems models ranging in complexity from two compartments to many compartments and species groups. With each of the proposed models, a yearly cycle of the systems behavior is si mulated. The comparative analysis of the response of each of the models allows conclusions to be drawn on the adequacy of the alternative hypotheses. This analysis also allows one to reject inadequate constructs, and provides some guidance on how to improve a certain hypothesis, even in the presence of a high degree of uncertainty.

Description: Phagocytosis as a means of heterotrophic nutrition in dinoflagellates, mainly in nonthecate forms devoid of photosynthetic pigments, is described on the basis of a year of observations at two fixed stations and other records from the natural habitat. The phagocytosed inclusions in the cell cytoplasm may show the remnants of the prey organisms in various stages of digestion as distinct from food vacuoles which are normal products of cell metabolism. Most of the larger phagotrophic dinoflagellates, such as Noctiluca miliaris, Polykrikos kofoidii and Gyrodinium spp., were recorded chiefly at the Secchi disk depth in the preserved samples. Among the more fragile nonthecates which were recorded and observed, mainly in live samples, many specimens showed phagotrophic inclusions. The role of these holozoic dinoflagellates in the pelagic ecosystem is discussed.

Description: The kinetics of phytoplankton extracellular release and the compositlon of these photoassimilated products that are excreted are not weil understood, especially in natural populations in which algal excretion and bacterial utilization occur simultaneously. Photoassimilated extracellular products represent an important input of DOC in aquatic ecosystems, a considerable fraction of which is taken up by heterotrophic bacteria. Experiments have shown that extracellular products are assimilated and respired with high efficiency in marine environments. Heterotrophie bacteria seem to play an active role in the regulation and transformation of phytoplankton extracellular products into particulate matter in the marine photic zone.

Description: The ISIS in situ incubator was used to evaluate the dynamics of a phytoplankton bloom in the Kattegat in late October 1979. The nutrient status of the water column indicated a typical fall regenerative situation with relatively high concentrations of ammonium and phosphate and only low concentrations of nitrate. The photic zone was well mixed during the bloom due to preceding rough weather. Clear, sunny and calm conditions prevailed the day prior to and during the bloom. Primary production was measured at four depths and amounted to 90.4 mg C m-2 h-1 integrated from the surface to 12 m. The highest fixation rate occurred at 1 m depth and was 16.4 mg C m-3 h-1. The productivity index was 3.7 mg C (mg chlorophyll a)-1 h-1 at 1 m and 5.3 mg C (mg chlorophyll a)-1 h-1 at 4 m depth. The light response relationship showed light saturation at about 3.8·1023 quanta m-2 h-1. It is concluded that primary production during this experiment was controlled by a combination of excess light energy and temperature but not by nutrient limitation.

Description: Three large plastic enclosures (3-4 m3) were anchored in the outer harbour of Helgoland (German Bight) and filled with natural seawater which was filtered free of algae. The enclosed water bodies were enriched with inorganic nutrients and inoculated with the diatom Thalassiosira rotula. During the growth of the algae diurnal changes in concentration of dissolved free amino acids (DFAA) occurred. The periodic concentration changes of individual amino acids with a low carbon to nitrogen ratio showed significant interrelationships with the partly synchronous devisions of the diatoms. From the exponential to the stationary phase the carbon to nitrogen ratio of DFAA shifted to higher values pointing at an adaptation of the organisms to the decreasing inorganic nitrogen source. During the bloom amino acids relatively rich in nitrogen were mainly excreted but by the end of the growth amino acids with a higher carbon content predominated. At phases of high photosynthetic activity the organisms probably reduced the high osmotic pressure by exudation of DFAA.

Description: Phenotypes, distribution and behaviour of Mesodinium rubrum (Lohmann) were studied in the stagnant basin lnre Verkviken (salinity about 6‰) on Åland, SW Finland. The organism varied in lenght from 15 to about 50 μm. The number of cirri varied greatly (33-85) and so did the number of chloroplasts (a few to more than 50). Surface maxima (red water) coinciding with chlorophyll a and productivity maxima were observed in October. Living specimens rich in starch were, however, also found down at 17 m in almost oxygen-free water. The swimming speed of Mesodinium rubrum can momentarily exceed 5000 μm s-1. Thus the organism has the potential to migrate vertically and take up nutrients from appreciable depths. The organism is highly phototactic and it is easily concentrated in a light gradient. The photosynthetic rate of enriched samples (artificial red water) was much higher than that of the original water samples. The role of Mesodinium rubrum in the food web is discussed.

Description: The micro-organisms which colonise kelp debris incubated in seawater show a clear succession. The media are first colonised by bacterial cocci and rods which are subsequently replaced by grazing flagellates and ciliates, as weil as amoebae and choanoflagellates in the later stages of the microheterotrophic succession. The biomass of grazing protozoa is generally 10% of that of the bacteria and estimates of consumption of bacteria by microflagellates of 10 μm3 body volume suggest that a mean value of 39 x the body weight may be consumed per day. lt is suggested that filter- and deposit-feeding organisms utilising degrading plant material are likely to use bacteria rather than protozoa as a principal food resource. Estimates of the rate of turnover of sediments and of the water column near to kelp beds support the belief that for optimal utilisation by consumer organisms detritus is recycled at a rate which is slow enough to promote the development of a bacterial population but which is too fast for protzoa to reduce the bacterial population by grazing.

Description: During spring and in summer the digestive enzymes trypsin and amylase of copepodids and adults of Calanus finmarchicus and C. helgolandicus were studied in a Swedish fjord in relation to various parameters of particulate matter. Regulation mechanisms of digestive enzymes varied with stage of development and physiological condition. In the stages studied three types of regulation were found: In copepodid stages Cl/II trypsin remained constant at a rather high activity irrespective of variations in amylase activity; in CIII-CV and males trypsin and amylase were strongly correlated; in females both enzymes varied independently of each other. Digestive enzymes of CV, females and males of the overwintering generation, were generally very low and did not correlate with any of the food parameters. The digestive enzyme activities were compared with concentrations of chlorophyll a, particulate carbon, nitrogen and carbohydrates at different depths. Amylase of stages CI-CV and adult males and trypsin of CIII-CV and males correlated significantly with carbohydrate concentrations. On the other hand amylase of adult females gave significant correlations with chlorophyll a and carbon. It is suggested that this difference between females and the other stages indicates different food selection.

Description: Copepods are an important link in the marine food web, and, in particular, serve as food for fish larvae. Schizopera elatensis, a marine harpacticoid copepod, was reared in the laboratory, and the effect of various environmental factors, i.e., diet, temperature, salinity and height of water column on its growth was determined. Schizopera elatensis multiplies at a wide range of salinities, 10‰ to 70‰, and temperatures, from at least 18° C to an upper limit of 36° C, with an optimum of 25° C, and grows in high densities (300-400 individuals per ml): the lower the water column, the higher the density. The prospective use of S. elatensis as a live food organism in mariculture is discussed.

Description: 14C and 3H methylamine, ammonium analogues, were used to study the competitive NH4+ uptake by cultured and natural phytoplankton and bacteria populations. The tracer experiments, performed by liquid scintillation techniques and microautoradiography, give evidence of competitive NH4+ uptake by bacteria and phytoplankton in oligotrophic and mesotrophic waters of the Baltic Sea. In eutrophic waters the uptake of the ammonium analogue was low especially for bacteria. Decreasing light intensity increased the methylamine uptake by bacteria compared to phytoplankton. Bacteria, competing with phytoplankton for dissolved ammonia in oligotrophic Baltic water, apparently do not play an important role in nitrogen remineralization. The significance of other decomposers is discussed.

Description: The main studies on phytoplankton ecology carried out in Kiel Bight during the last decades are briefly reviewed. Special emphasis is laid on the hydrographical structure of this transitional area between the Baltic Sea and the North Sea, as it strongly affects the seasonal cycle of phytoplankton standing stock and species succession through vertical stratification and advection processes. Both these hydrographical features prevail during the growth period of phytoplankton and are responsible for large variations in population density and nutrient supply. The seasonal species succession is also influenced by advection. The annual primary production figure of about 150 g C·m-2 approaches the upper limit of values recorded for other parts of the western and southern Baltic. Total irradiation appears to exert the strongest influence on the seasonal cycle of primary production as long as water temperatures are low, giving way in summer to temperature as the determining factor for the production rate.

Description: The fucoid/barnacle system on a moderately exposed shore on the Isle of Man is briefly defined and described. Patella were either continually removed or excluded by fences in various parts of the mosaics on this shore. This tested the influence of their grazing on the different communities. The sequences and rates of algal colonization of the different experimental areas are compared. Diatoms and/or small filamentous algae, followed by larger greens and then Fucus sporelings formed the usual pattern of colonization. Patella grazing has greatest effect in the mid-region of this shore; but it decreases higher and lower down, and on verticals and amongst dense old barnacles.

Description: The population density and standing stock (wet-, dry-, and organic biomass) of copepods, euphausiids, chaetognaths, and total zooplankton were studied from March 1976 to February 1977. Seasonal changes in population density and standing stock were examined with regard to hydrography and phytoplankton standing crop (chlorophyll a) and primary production (14C). The data have been further analysed with respect to the trophic position of the component zooplankters and to the production cycle in Norwegian arctic fjords.

Description: Thioploca constitutes a great portion of the benthic biomass off the Chile-Peru coast. This organism is eaten by the higher organisms and constitutes a major input of organic carbon in the food chain in this region. Thioploca has been an enigma ever since its discovery in 1907 and the prefix "thio" in the genus name has led investigators to believe that hydrogen sulfide is the energy source necessary to synthesize Thioploca biomass. The results of this investigation indicate that methane is the energy and carbon source for the organism. The organism does not use radioactive labeled acetate, glucose, mixture of amino acids, thymine or bicarbonate as demontrated by autoradiography. Since the energy and carbon source is methane, it indicates that Thioploca is a methylotroph. Methane in this area is generated by microbial activity in reduced sediments and from seepage from coal seams that run under the seafloor. Methane, through Thioploca, represents a major new mechanism, other than photosynthesis, to add cellular carbon to the ecosystem oft the Chile-Peru area. Because methane is the energy and carbon source, Thioploca's taxonomic position as weil as its evolutionary position should be re-assessed.

Description: Microbial biomass, concentrations and enzymatic decomposition rates of proteins and carbohydrates were analysed during spring 1980 from a 10 m sediment station in the Kiel Bight. During March, a considerable increase in total organic matter, proteins and carbohydrates was observed, followed by a decrease during April. The accumulation of organic matter in the sediment could be traced back to the breakdown of the algal spring bloom. Activity rates of (α-amylase, ß-D-glucosidase and proteolytic enzymes paralleled the variation pattern in concentrations of carbohydrates and proteins. During the decomposition processes, a drastic shift in the protein to carbohydrate ratio was observed. The dominating part of the enzymes involved in the decomposition of organic material obviously arose from autolysis of the algae cells themselves. After an initial depression, microbial biomass increased, obviously due to the availability of suitable substrates for microbial growth following the decomposition processes.

Description: Data from a series of laboratory and field predation experiments using fish and decapod predators from seagrass beds in the Indian River, Florida, USA, indicated that the density of many of the taxonomic groups of seagrass-associated macrobenthos were related in a negative exponential manner to the total density of decapod crustaceans present. Significant regressions were observed in the laboratory and the field experiments for the Amphipoda, Gastropoda, Bivalvia, Polychaeta, Sipunculida, and Tanaidacea, whereas the lsopoda and Nemertinea showed no such relationships. These data emphasize the fact that simplification of intermediate trophic levels in trophic models is unwarranted and may result in failure to recognize important regulatory pathways for seagrass community structure.

Description: Both Podon leuckarti and Evadne nordmanni play a predominant role in the plankton community of Kiel Fjord in summer. Increase and decrease of the populations were recorded through short-term sampling from May to the beginning of July. Abundance in relation to temperature and salinity, body size, number of embryos per female and the occurrence of permanent eggs were investigated. Podon leuckarti reached its peak at the end of May, two weeks earlier than Evadne normanni; the maximum abundance was 6500 individuals · m-3 and 8900 individuals · m-3 respectively. The rapid increase of both populations is characterized by an exponential growth phase. The estimated doubling time ranged from 0.5 to 4.3 days. With increasing temperature, body size and number of embryos per female decreased. An inspection of the stomach content showed that both species apparently had fed mainly on phytoplankton.

Description: From June 1975 to June 1976 the zooplankton and phytoplankton content of the Lister Ley (northern wadden sea of Sylt, German Bight) was measured. The dominant group of the zooplankton were the calanoid copepods with the main genus Acartia. Three species of Acartia were found during the period of investigation. Acartia tonsa could be found in large numbers only in spring 76. Acartia c/ausi and Acartia discaudata showed several peaks from June 75 to October 75. Three of these populations were produced by larval development in the research area; the time span of each generation was 5 to 5 1/2 weeks. In many cases there were correlations between the increase of Acartia nauplii and blooms of distinct phytoplankton species. A bloom of Phaeocystis pouchetii had a negative effect on the copepod populations. When drifting through the northern wadden sea of Sylt, Acartia clausi formed larger populations than in the north Frisian coastal water. In Acartia tonsa there was a marked decrease in population density within the wadden sea area.

Description: The importance of bacteria in the feeding of marine bivalves has been demonstrated by several authors. Some examples of good growth of molluscs were noted on a bacterial diet only. But, while the intense filtration of bacteria by molluscs has been observed, the exact role of bacteria in the nutrition of bivalves was not completely known. The filtered particles were sometimes eliminated as pseudofaeces, without any intestinal transit. On the other hand, live cells could also pass through the gut without being degested. To study in detail the fate of bacterial cells distributed as food to young bivalves, we used a new method which combines histology and scanning electron microscopy. This made it possible to observe, on serial histological sections of whole animals, the gut content and the condition of the ingested cells at the different levels of the intestinal tract. The ingestion and digestion by young mussels (Mytilus edulis) of some marine bacterial strains belonging to different taxonomic groups were studied by this method. Thus, partially digested bacterial cells were observed in the stomach, when the hind gut contained undamaged cells, three hours after food distribution. The results obtained for all the strains we tested are presented and discussed in this paper.

Description: Grab samples were taken at seven stations (10-58 m) in the Hanö bay in July-August during the period 1970-78. A high percentage, 26 - 60 %, of surviving adults (females) were found. At stations shallower than 38 m increasing population densities of Oiastylis rathkei were found until 1975 after which they decreased again. The population increase was found to be positively correlated to high water temperature during the previous winter. At 43 m depth the population changes were numerically small. Variations in the oxygen regime in the Bornholm basin caused the population changes at 58 m depth.

Description: Scientists of the Institut für Meereskunde at the University of Kiel have for several years been involved in investigations into the role of carbon heterotrophic microorganisms in the food web of the western Baltic. The aim of this work is to obtain information on the transformation of organic material from the primary producers to bacteria and from these to zooplankton and zoobenthos during the annual cycle. The release of phytoplankton exudates was investigated by use of tracer methods and by the uptake of this material by bacteria. lt could be shown that in the Kiel Bight area approximately 15- 30 % of the yearly primary production was transformed to bacterial biomass. In relation to the phytoplankton development the bacteria population exhibits seasonal changes. The growth of aufwuchs was studied and also the sedimentation of algal detritus. During sedimentation a rather high amount of the easily degradable material is remineralized. The remineralization processes are strongly affected by temperature. Laboratory experiments showed that 35 % of the phytoplankton material was remineralized at 20 °C and 3 % at 5 °C per day. The bacterial aufwuchs is a valuable subtrate for grazing organisms like ciliates and rotifers. These processes continue after sedimentation of the detritus and stimulate bacterial activity in the uppermost zone of the ground. The amount of bacterial biomass production influences the development of the meiofauna. In shallow coastal waters microphytobenthos can provide most of the primary carbon production from which about 50 % were transferred to bacterial biomass.

Description: Many benthic ciliates are known to feed upon bacteria in the marine environment. These may in turn be utilized as food by harpacticoid copepods which graze upon them. Simple non-tracer feeding experiments were carried out in the laboratory with various representatives of these organisms. The growth rates of the ciliate Uronema sp. with different species of bacteria as food, including oil-degrading bacteria, were compared. Results of feeding experiments with the harpacticoid copepod Tisbe holothuriae fed on Uronema sp. show an uptake rate of 12-192 ciliates copepod-1 h-1. The ecological implications are discussed.

Description: The Dead Sea is a highly dynamic ecosystem in which two types of biological changes can be observed: a long-range process of adaptation and selection towards higher salt tolerance as a result of the increase of the salinity and changes in salt composition with relative increase in magnesium, and seasonal changes due to variations in temperature and salinity (winter floods). As microorganisms live in the Dead Sea at the upper limit of their salt tolerance a small decrease in salinity causes a strong increase in microbial growth and activity. This explains the heavy bloom of Dunaliella and halobacteria observed in summer 1980.

Description: Eutrophication by sewage effluent has led to the development of extensive mats of green algae over much of the former open mudlands of Langstone Harbour on the south coast of Britain. The presence of the mal reduces the biomass and diversity of the mud-dwelling infauna but a great increase in the number and biomass of epibenthic animals (primarily Hydrobia ulvae Pennant) produces a total biomass almost twice that of open mudlands. Although the common invertebrates are favoured prey for many estuarine birds these algal areas are avoided by the dense aggregation of waders and wildfowl.

Description: The ingestion rate and the resulting assimilation calculated by means of a law taking into account activities of the digestive enzymes (amylase and trypsin) on the carbohydrates and proteins ingested, are determined in two experiments on Artemia. They are fed the same species of phytoplankton (Tetraselmis suecica), at the same concentration but with two chemical compositions. In one experiment, the cells are rich in carbohydrates and poor in proteins, and in the second one they are poor in carbohydrates, rich in proteins. Different observed ingestion rates induce a balance in proteins, and a large difference in the carbohydrates ingested. When digestive enzymes are taken into account, the assimilated carbohydrates and proteins are similar (explaining the similitude of the growth rate observed). The assimilation yield study shows that digestive enzymes induce a better digestion of chemical compounds in low concentrations in the food. That could correspond to a regulation of assimilation as a function of requirements of Artemia. Requirements would be the first internal factor that regulates the nutritional behavior. So two processes are possible for Artemia to obtain the sufficient quantity of food: regulation of ingestion rate, probably depending also on olfactory mechanisms, and regulation of assimilation by the way of digestive enzymes. The importance of these processes is discussed as a function of environmental conditions.

Description: There are definite differences in the rate of utilisation of the components of the complex substrate represented by kelp debris. The primary photosynthate D-mannitol is used most rapidly, followed by sugars and finally alginates which comprise as much as 45% of the particulate debris. There are also seasonal differences in the efficiency of conversion of these components into bacterial biomass. During the summer months the gross conversion of carbon to bacterial biomass in the dissolved fraction of detritus is as high as 30% and may reach 66% when associated with particles ( = carbon: carbon conversion efficiency of 33%) whilst the value for the particulate fraction is approximately 11% . Because of the lower conversion efficiencies in the winter, annual conversion of carbon from kelp production to bacterial biomass through the first step in the decomposer food chain is approximately 14% but this value is as high as 22% in the summer months (= carbon: carbon conversion efficiency of 11%). The results suggest that annual bacterial production in the water column based solely on the degradation of kelp is approximately 11.5 g m-3 and could rise to as much as 18.1 g m-3 during the summer months. These values agree well with estimates of bacterial production based on the biomass of bacteria measured in the water column near to kelp beds.

Description: From April to September 1978 benthos and plankton samples were taken at three different sites in the Schlei fjord (German Baltic coast) with different salinity (ca. 15, 10 and below 5‰). Abundances of benthos and plankton taxa were compared with abundances of the taxa occurring in the guts of Pomatoschistus microps and P. minutus, caught at the same places at the same time. Main food were calanoids, oligochaetes and harpacticoids. Calculations showed that young gobies most probably regulate the population of harpacticoids to a large extent by grazing.

Description: In July 1978 several experiments with enclosed plankton communities were carried out in the Arkona Sea using 25l cylindrical bags made of 0.2 mm polyethylene film. These experiments concerned the response of phytoplankton to nutrient input. Phytoplankton biomass, primary production and chlorophyll content increased rapidly in enriched water, in contrast to the controls where changes were negligible. Nutrients were depleted to the same levels as in the controls after a few days. The μ-algae were the first to respond to nutrient input, followed later by diatoms and dinoflagellates. In the course of the experiments, however, the energy was stored to an increasing extent in the cyanophytes at the expense of other groups where energy content remained constant or decreased slightly.

Description: Feeding, digestion and assimilation are usually treated as separate aspects in studying the physioecology of copepods. A general model predicting the assimilation rate from ingestion rate, phytoplankton species compositon and digestive or physiological state of the animal is presented. The assumption is made that digestion is accompanied by a subsequent decrease in cell volume, which is equal to the assimilated part of the cell. In addition, a time delay between ingestion and the onset of digestion is assumed to describe the digestion properties of the algal cells. The model predicts a decrease in assimilation efficiency with increasing ration. The minimum gut passage time and the digestion rate seem to be the most important parameters for the production of copepods. These and other characteristics of the model are discussed in relation to available information.

Description: Primary productivity in Antarctic inshore coastal waters at Signy Island is high (2 g C · m-2 · day-1) compared with oceanic production (0.5 g C · m-2 · day-1). Seasonal changes in phytoplankton, inorganic nutrients, total viable bacterial populations, proteolytic bacteria, denitrifying bacteria and heterotrophic nitrogen fixing bacteria have been followed at 14 day intervals from January 1976 - March 1978. Phytoplankton productivity reached a maximum in early January and this corresponds with a marked decline in N03-N (32 μg at N · I-1 to 〈 51 μg at N · I-1) and PO4 3- · I-1 (2 μg at PO4 3- · I-1 to 0.65 μg at PO4 3- · I-1). After the collapse of the bloom, NH4 + levels reached a maximum and correlated with high populations (1.4 x 105 bacteria/g dry wt) of proteolytic bacteria in the sediment. A large proportion of the heterotrophs (67 %) posses functional phosphatases which may play a significant role in phosphorus regeneration.

Description: Results obtained from plankton sampling in the Schlei during spring over a couple of years are discussed with regard to the significance of predator-prey relations for the development of invertebrate plankton and larval fish populations. In spite of a large number of fish larvae growing up in this area in spring, a characteristic minimum in total biomass of the invertebrate plankton in June does not appear to be caused by predation. However, in years of high abundance of herring larvae, the size selective feeding at the estimated rates may be supposed to accelerate the decline of the copepod population, and thus to expand and intensify food limitation for the larvae in June.

Description: The predatory role of juvenile and adult shore crabs, Carcinus maenas L., an tidal flats in the wadden sea near the North Sea island of Sylt has been evaluated with field enclosures. Early benthic stages (2-4 mm carapace width) prey heavily an microfauna (Nematoda, Turbellaria, Ostracoda) and particularly an juvenile macrofauna. When crabs grow up they gradually shift to larger prey and a bifurcation in prey selection occurs: males concentrate an molluscs while females feed preferentially an annelids. Annual consumption expressed as dry organic matter is estimated at 3.6 g·m 2 for O-group crabs and 1.3 g·m-2 for adult crabs. Carcinus maenas is expected to cause conspicious impact an zoobenthos in the wadden sea 1. by preying always an the most abundant species, 2. by increasing juvenile mortality of high-biomass macrofauna, 3. by being a predator of highly variable abundance between years.

Description: The diet of 34 demersal fishes from the continental shelf and top of the Atlantic slope is studied by analysis of digestive contents. All fishes from this area are stenophagous predators (7 ichthyophagous fishes, 1 concholophagous fish} or euryphagous predators (26 demersal fishes). The small motile benthic crustaceans (Mysidacea, Amphipoda, young Decapoda Natantia and Brachyurans) are the most important food for euryphagous fishes during the first years of their life near the sea floor. This special fauna, now called "suprabenthos", is not well sampled by traditional benthic gears. A new suprabenthic sledge is proposed for quantitative samplings of the motile freeswimming crustaceans.

Description: Pogonophores have no internal digestive system and must feed in some way through the skin. The evidence for uptake of DOM by small unitentaculate species is reviewed. Siboglinum ekmani can meet its metabolic needs by uptake of DOM from the mud in which it lives; the evidence for two other species of Siboglinum and for Sclerolinum brattstromi is less conclusive but they may also be able to obtain sufficient DOM in their particular habitats. Chemoautotrophy, obtaining energy from the oxidation of H2S, may be important to some of the large pogonophores.

Description: Mangrove swamps of Brazil, Florida, Mexico, Bermuda, Sinai and Papua New Guinea were investigated with respect to phycomycetes that degrade cellulose, chitin and keratin. Strains of Phlyctochytrium mangrovis Ulken, and species of Thraustochytrium, Schizochytrium and Ulkenia were isolated and kept in pure culture. Phycomycetes as nutrient for protozoans and invertebrates were observed.

Description: The results of this study show that chemoautrophic nitrification is the most important source ot nitrate in the brackish water of the Kiel Bight. The main nitrification potential is localized in the sediment. Nitrification activities were measured from January to March 1978 in a sand sediment from a beach station in the Kiel Fjord and in March and May 1979 in the sand sediment of the central Kiel Bight. The nitrification rates measured at the beach station lay between 0.9 x 10-3 μgat N/cm3 x h and 4.5 x 10-3 μgat N/cm3 x h and in the Kiel Bight between 1.9 x 10-2 μgat N/cm3 x h and 4.7 x 10-2 μgat N/cm3 x h.

Description: Some of the benthos studies carried out by working groups of the Institut für Meereskunde and the Joint Research Programme „lnteraction Sea - Sea Bottom" of Kiel University are briefly reviewed. As an introduction, main structural features of the large-scale pattern of macrozoobenthos of the Western Baltic are discussed in connection with the governing environmental factors (sediment type, temperature, salinity, discontinuity layer, seasonal O2-deficiency and H2S). Sedimentation of primary production and its fluctuations considerably affect benthic activity. In addition, locally reduced competition leads to high production rates, established from observations on population dynamics of single species. Trophic relations of important macroinvertebrates throw light on the position of the macrobenthos within the whole system. Experimental studies in situ and in the laboratory contribute to the analysis of processes involved in the functioning of the ecosystem and its subunits.

Description: In a Mediterranean seagrass ecosystem (Posidonia oceanica ) around Ischia (Gulf of Naples) an attempt was made to study the fate of Posidonia derived particulate matter in wrack beds around and within the seagrass stands, on the shore and in the water column. Changes in total soluble carbohydrate concentrations from green and brown parts within one leaf vary from 70.7 to 25.7 mg.g-1 dry weight. Minimum values of 0.2 mg.g-1 dry weight consisting mainly of saccharose are detected for brown wrack particles. All other components found in green leaf parts, e.g. fructose, glucose and myo-inositol probably leach rapidly into the water or are transported into the rhizome prior to the loss of the brown leaf region. Only in the rhizome the trisaccharide raffinose was detected in addition to the components found in the leaves. The importance of the brown leaf fraction as a substrate for microheterotrophs is indicated by bacterial densities up to 4 x 104 cells.mm-2. This is correlated with nitrogen and carbon values, showing a decreasing C/N ratio with decreasing particle size, but increasing O2 uptake with maximum values of 10 mg.g-1.h-1 for the particle size fraction of 0.1 - 1 mm. The role of the brown dead Posidonia derived leaf tractions as energy source for consumers is discussed and attempts are made to redefine the terms "debris" and „detritus".

Description: The paper examines the conventional notion of the food chain of the oceans in the light of field studies of microheterotrophic processes. In common with the earlier observations of POMEROY (1974), the conclusion is that the classical paradigm is not compatible with contemporary observations and appears to need extending in order to take them into account. The evidence would seem to point towards at least half of primary production passing through the planktonic microheterotrophs before it is mineralized. The possible routes of flow of organic material from the classical food chain (phytoplankton excretion, losses during grazing and zooplankton excretion) were examined in some detail. The conclusions were that the cumulative production of dissolved organic material from the above sources, estimated to amount to about 60% of primary production, are sufficient to sustain the anticipated rates of microheterotrophic activity. These considerations, by themelves, give no reason to seriously doubt the accuracy of contemporary measurements of primary production. It was calculated, given the present day estimates of microbial growth yields, that secondary production at the microbial level may be comparable to or greater than that of herbivorous zooplankton. When considering the sources of supply of organic material for the microheterotrophs, the events occurring prior to herbivore ingestion were found to be more important than those subsequent to ingestion. As a consequence, the overall accuracy of the estimates of the supply of organic material to the microheterotrophs was very much dependent upon the assessment of total phytoplankton exudation of organic material, i.e. the measured excretion plus that taken up by heterotrophic micro-organisms during the measurement period. The review also highlighted the need for a better understanding of the fate(s) of microbial production: to what extent it is utilized directly by metazoan hervibores as opposed to passing through a protozoan food chain.