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The short term impacts of fishing pressure were compared with the variability induced by environmental drivers on quantitative benthic community impact indicators. The different pressures were evaluated through comparative multifactor statistical analyses of their effects on macrofauna indicators in a Baltic Sea area with high natural disturbance. The area is exposed to a wide range of fishing intensities from long term non-fished areas to seasonal and annually frequently fished areas. Such evaluations are important for comparing the influence and short term variability of impact indicators from both demersal fisheries and the environment, including benthic community biodiversity (species richness), density (abundance in number of individuals), biomass, and average individual mean weight, with high spatio-temporal resolution. Environmental drivers include near bottom water current speed, salinity, temperature, and dissolved oxygen concentration, considering habitat specific and seasonal conditions. Demersal fishing-induced impacts were evident for all indicators. The highest fishing impacts were estimated in soft muddy and sandy habitats and in the second quarter of the year for all indicators, considering complex interactions. All environmental drivers, especially, current speed, had significant impacts on all indicators. The significant influences and short term variability caused by environmental drivers were of the same or larger order of magnitude as fishing impacts. Consequently, the short term influence of environmental drivers and seasonal differences in fishing pressure need to be considered when using quantitative benthic fishing impact indicators and identifying areas that are more or less resilient to fishing in relation to short- and long-term fisheries management plans.

De danske stenrev har i over 100 år været udnyttet som en ressource for marine anlægsarbejder og revenes tangskove blev siden alvorligt påvirket af eutrofiering. Udviklingen,med tab af hårdbundshabitater og ringe naturkvalitet på dem der er tilbage, er nu ved at vende. Vandmiljøet viser positive forbedringer, genopretning af enkelte stenrev er gennemført og nye genopretningsprojekter er i støbeskeen.Denne undersøgelse er en af de få, der er gennemført på danske rev, som beskriver artsspecifikke biomasser af flora of fauna samt individantal af fritlevende dyr. Undersøgelserne er gennemført på Hatter Barn i Samsø Bælt og udgjorde en delmængde i det større RevFisk projekt, hvis overordnede formål var at beskrive stenrevs betydning som habitat for fisk.To relativt afgrænsede og dybdemæssigt forskellige kortlagte revstrukturer blev undersøgt på Hatter Barn, hvor dybden er henholdsvis 6-13m og 13-21m. De kvantitative undersøgelser af makroalger og bunddyr blev udført med en dykkerbetjent ”undervandsstøvsuger”. Der blev indsamlet og oparbejdet 12 prøver fra hver revstruktur, hvor dem fra det dybe rev blev opdelt i to grupper. Vi fandt samlede biomasser på 619,6g (± 397,6 g) askefri tørvægt/m2 på sten på det lavvandede plateau, 74,2g (± 26,9 g) på det dybere rev med en stejl skråning og kun 13,7g (± 2,0 g) på stenene neden for stenskråningen. Der varbetydelig forskel i artssammensætning og dominansforhold på de forskellige dybder.Vi fandt signifikante positive sammenhænge mellem den samlede algevegetations biomasse og den samlede faunabiomasse og antal individer af mobile dyr. Sammenhængene var endnu tydeligere mellem rødalgebiomassen og fauna biomasser og antal mobile dyr og rødalgerne var yderligere positivt korreleret med biomasse og antal individer af krebsdyr. På baggrund af de fundne faunabiomasser og undersøgelser af maveindhold i fisk fanget på revet blev fødebiomasser og fødeproduktion for torsk og havkarusser estimeret for de to revstrukturer på Hatter Barn.

For 2 years, a baseline investigation was carried out to collect reference information of the present environmental status in the Fehmarn Belt and adjacent area. The temporal and spatial variability of phytoplankton was monitored by a combination of monitoring buoys, pigment analysis and fast screening microscopy. The overall phytoplankton succession in the Fehmarn Belt area was found to be influenced primarily by the seasonal changes, where various diatoms dominated the spring and autumn blooms and flagellates like Chrysochromulina sp., Dictyocha speculum and various dinoflagellates were occasionally abundant in late spring and summer. The phytoplankton groups were remarkably uniform horizontally in the investigation area while large differences in both biomasses and composition of individual phytoplankton groups were seen vertically in the water column, especially in the summer periods, in which the two-layer exchange flow between the North Sea and the Baltic Sea is showing a particularly strong stratification in the Fehmarn Belt. The chlorophyll a concentrations ranged continuously from 1 to 3 μg/L at the three permanent buoy stations during the 2 years of monitoring, except for the spring and autumn blooms where chlorophyll a increased up to 18 μg/L in the spring of 2010 and up to 8 μg/L in the autumn of 2009. Recurrent blooms of filamentous cyanobacteria are common during the summer period in the Baltic Sea and adjacent areas, but excessive blooms of cyanobacteria did not occur in 2009 and 2010 in the Fehmarn Belt area. The combination of the HPLC pigment analysis method and monitoring buoys continuously measuring fluorescence at selected stations with fast screening of samples in the microscope proved advantageous for obtaining information on both the phytoplankton succession and dynamic and, at the same time, getting information on duration and intensity of the blooms as well as specific information on the dominant species present both temporally and spatially in the large Fehmarn Belt area.

European seas are encountering an upsurge in competing marine activities and infrastructures. Traditional exploitation such as fisheries, tourism, transportation, and oil production are accompanied by new sustainable economic activities such as offshore windfarms, aquaculture, and tidal and wave energy. One proposed solution to overcome possible competing claims at sea lies in combining these economic activities as part of Multi-Use Platforms at Sea (MUPS). MUPS can be understood as areas at sea, designated for a combination of activities, either completely integrated in a platform or in shared marine space. MUPS can potentially benefit from each other in terms of infrastructure, maintenance, etc. Developing MUPS in the marine environment demands adequate governance. In this article, we investigate four European sites to find out how governance arrangements may facilitate or complicate MUPs. In particular, we apply a framework specifying policy, economic, social, technical, environmental, and legal (PESTEL) factors to explore governance arrangements in four case study sites in different sea basins around Europe ( the Mediterranean Sea, the Atlantic Ocean, the North Sea, and the Baltic Sea). The article concludes with policy recommendations on a governance regime for facilitating the development of MUPS in the future.

In the shallow micro-tidal cove Kertinge Nor, Denmark, a series of field campaigns were conducted from April 1995 to September 1996. During these campaigns, the effect of benthic grazing on phytoplankton concentrations was studied using a dual approach. In the first approach, the density, size distribution and in situ growth of 3 dominant benthic grazers were determined to assess grazing potential and its realisation. In the second approach, the realised grazing potential was estimated from the decline in area-specific chlorophyll a (chl a) concentrations after breakdown of stratification. Forcing functions were monitored continuously during the field campaigns using meteorological data, current meters, temperature loggers and CTD point measurements. In addition, measurements from a local monitoring program in Kertinge Nor were included in the data analysis. Stratification of the water column in the cove was mainly governed by wind speed and solar radiation and occurred 50 to 75% of the time. The potential grazing pressure of the benthic suspension feeders varied but was always greater than that required to graze the entire volume of the cove per day. Using both approaches, it was estimated that realised grazing was ~50% of the potential. The lack of realisation of the grazing potential could be attributed to a lack of mixing of the water column, which resulted in strong vertical gradients in concentrations of chl a. The primary mode of decoupling between benthic suspension feeders and phytoplankton was the stratification of the water column, which created refuges for the phytoplankton.

The eutrophication status of the entire Baltic Sea is classified using a multi-metric indicator- based assessment tool. A total of 189 areas are assessed using indicators where information on reference conditions (RefCon), and acceptable devi- ation (AcDev) from reference condition could be combined with national monitoring data from the period 2001-2006. Most areas (176) are classified as 'affected by eutrophication' and only two open water areas and 11 coastal areas are classified as 'unaf- fected by eutrophication'. The classification is made by application of the recently developed HELCOM Eutrophication Assessment Tool (HEAT), which is described in this paper. The use of harmonized

Viden om stenrev (Naturtypen 1170) og deres betydning for gyde- og opvækstområder for fisk er i dag sparsom. Der er ikke tidligere gennemført undersøgelser, der har dokumenteret, hvordan et stenrevs størrelse, struktur og placering spiller ind på dets betydning som gyde- og opvækstområde for fisk. Det er derfor i dag ikke muligt kvantitativt at redegøre for stenrevs betydning for fiskeressourcerne eller udarbejde målrettede natur-genopretningsplaner for stenrev med det formål at genskabe gyde- og opvækstområder for fisk. Det vil Projektet RevFisk forsøge at råde bod på.Centrale spørgsmål i projektet er: Hvilke fiskearter findes på revet? Hvornår er fiskene der? Hvilke fisk er nøglearter på revet? Hvad er faunaudbuddet? Hvad spiser nøglefiskearterne? Hvor stor del af fiskenes føde stammer fra stenrevet? Hvad er rovfiskenes adfærd og opholdstider på stenrev? Er der inter- og intraspecifik konkurrence mellem nøglefiskearterne? Hvor hurtigt vokser fiskene? Hvad er spredningsvejene for fisk til og fra et givent stenrev? Hvordan forvaltes stenrev nationalt og internationalt?Målet med projektet er at opbygge viden om marine stenrevs biologiske funktion for fisk og deres betydning som gyde og opvækstområde. Viden indsamlet i løbet af projektet vil implementeres til at udvikle forvaltningsværktøjer, der dels kan anvendes ved etablering af nye samt reetablerede stenrev og dels til at forvalte eksisterende stenrev.Der vil udvikles modelværktøjer, der kvantificerer stenrevs betydning for fisk som funktion af stenrevets tilstand, størrelse og dybdeplacering. Stenrevs betydning som donor til det omkringliggende område belyses igennem driftsanalyser af spredningsveje. Denne vidensopbygning vil blive brugt til at udvikle guidelines i forhold til design, form og placering ved naturgenopretning af stenrev.

In a detailed analysis of oxygen saturation in a shallow Danish estuary it was possible to separate the effect of meteorological forcings (i.e. wind and solar radiation) and nutrient loads on oxygen depletion in bottom water. Regression analysis showed that oxygen saturation tied to nitrogen load rather than to phosphorus load. During summer periods of stratification the oxygen saturation could be attributed to the time elapsed after the onset of stratification and the accumulated nitrogen loading 10 month prior to measurement. Using a 10-year meteorological database and an empirical model it was calculated that a 25% reduction in nitrogen loading would reduce the number of days with severe oxygen depletion (i.e.

This chapter deals with climate-related changes in the marine ecosystem of the Baltic Sea. The Baltic Sea is often described as one of the world’s largest brackish water bodies. It has a unique combination of oceanographic, climatic, and geographic features. Most important in this context is: the sea is a nearly enclosed area having a water residence time of 30 years, due to restricted water exchange through the Danish Straits. It is situated in northern Europe and has, therefore, some arctic characteristics and a pronounced seasonality. It is affected alternately by continental and marine climatic effects. It has a catchment area approximately four times larger than the sea itself, while it is as the same time very shallow, with an average depth of only 56 m, having thus a relatively small water body. Seasonal vertical mixing of the water reaches a depth of 30–50 m and contributes to resuspension of nutrients and pollutants. In deeper parts, a permanent halocline appears, below which anoxia is common and interrupted only by major inflows of North Sea water.

Colacium vesiculosum, a common epizoic freshwater euglenoid occasionally was found in the Western Baltic infesting planktonic copepods. Its occurrence coincided with low salinity, high temperature and large biomass of cope pods in the area. Infestation was most pronounced on Acartia sp. living in the upper part of the water column, but decreased in Centropages hamatus, Temora longicornis and Pseudocalanus elongatus (in that order), probably reflecting the vertical migrational behaviour of these copepods. Survival and egg production in the copepods were not affected by Colacium infestation, and as its biomass only amounted to 1.5% of phytoplankton biomass, it is concluded that C. vesiculosum only plays a minor role in the area.

Many of the sediments in our coastal environments are contaminated with various metals. The highes Iconcenlralionsofconlaminanls are found in harb ours, where anlifouling painls and industrial activities are the main sources. In the past years there has been a strong focus on TBT that is known to be highly toxic and to affect the hormonal balance of many animals. Almost all substitutes for TBT are based on Cu-complexes. Copper is known to form strong complexes with natural organic matter and the total Cu-concentration in sediments is found to correlate with the concentration of organic matter (see Fig. 8.1).

Resumé:Effekten af 101 tokomponentblandinger og 20 trekomponentblandinger bestående af 22 forskellige pesticider blev undersøgt i 7 forskellige testsystemer. Effekterne af blandingerne blev sammenholdt med pesticidernes virkningsmekanismer/virkemåder med henblik på at undersøge, om det med baggrund i denne viden var muligt prediktere, hvorvidt blandingerne ville udvise additivitet, antagonisme eller synergisme. Endvidere blev undersøgt i hvor vid udstrækning resultaterne fra et testsystem kunne overføres til andre testsystemer. Hovedparten af blandingerne virkede additivt, og der blev generelt fundet en god overensstemmelse imellem terrestriske og akvatiske planter samt Microtox testen og dafnier.

Regulating mechanisms of phytoplankton growth rate and biomass were studied during two periods in March and June in a shallow (< 5 m), semi-enclosed basin in the Roskilde Fjord, Denmark. Phytoplankton community net growth rate (i.e. phytoplankton growth rate - pelagic grazing rate) was quantified by following changes in chlorophyll-a concentrations in unfiltered water enclosed in 10 liter transparent bags deployed at different depths in the water column. During spring, at high nutrient concentrations phytoplankton community growth rate was positive at photon flux densities above 0.2 mol m-2 d-1 and community growth approached 0.4 d-1 at ca. 3 mol m-2 d-1 (≈ surface light). During summer, the minimum photon flux density required for positive community growth rate was 2-4 mol m 2 d1, while maximum community growth rate at ca. 15 mol m-2 d-1 varied between 0.1 and 0.6 d-1 according to the availability of inorganic nitrogen. Phytoplankton biomass in the water column increased during periods of densit...

We review various aspects of the structure and functioning of Danish estuaries from data collected by the National Monitoring Program and from information in published sources. We present data on the physical, chemical, and biological characteristics of estuaries in Denmark, we evaluate the functioning of these systems as filters and transformers of nutrients and we evaluate the outlook for Danish estuaries in the future. Danish estuarine systems are for the most part shallow (

The retention efficiency of 13 species of suspension feeding bivalves has been determined by analysing the particle size distribution in the inhalant and exhalant water currents using a Coulter electronic particle counter. The bivalves were held in aquaria under conditions very similar to their natural environment. It is shown that 11 species, Cardium echinatum, Cardium edule, Modiolus modiolus, Mytilus edulis, Musculus niger, Cultellus pellucidus, Arctica islandica, Ostera edulis, Hiatella striata, Mya arenaria and Venerupis pullastra, which all possess eu-latero-frontal cirri completely retain particles above 1 μm. Particles down to 1 /Lm were in most cases efficiently retained. The retention efficiency in Pecten opercularis and Pecten septemradiatus both lacking the eu-latero-frontal ciliary tract decreases below 7 μm and reaches only 20 % at 1 μm.

Mussels (Mytilus edulis) transferred in net bags from clean to chronically mercury polluted water readily accumulated mercury during an exposure period of three months. Growth of the transplanted mussels had a “diluting” effect on the mercury concentration, but the absolute weight of mercury uptake increased throughout the entire period, though there was a tendency for decreased efficiency of the removal of mercury per liter of water filtered by the mussels. Mussels were also translocated from polluted to clean (laboratory) water to depurate mercury. The biological half-lives of mercury was 293 d for M. edulis from the chronically polluted area in contrast to only 53 d for mussels from a temporary massive mercury polluted area near a chemical deposit. In both cases about 75% of the total mercury in the mussels was inorganic, and it is suggested that both inorganic and organic mercury species were immobilized in mussels from the long-term mercury polluted area, whereas the immobilization capacity was exceeded in the short-term mercury exposed mussels near the chemical deposit. Very slow elimination of mercury was observed in the deposit-feeding bivalve Macoma balthica from the chronically polluted area, and about 6% of the total mercury was methyl-+phenyl-mercury. This is more than three times lower than found in M. edulis from the same collecting site. A pronounced difference in the mercury speciation (i.e., total mercury, total organic mercury, methyl-mercury and phenyl-mercury) in M. edulis from the two mercury polluted areas is thought to reflect the different character of the mercury pollution in the two areas.

Mytilus edulis (average length 3.7 em) were fed mixtures of algae (10000 Phaeodactylum tricornutum cells · ml-1) and natural silt (0 to 55 mg · l-1), and the effects of silt concentration on filtration behaviour, food uptake and carbon budget were studied. Particle clearance averaged 66 ml · min-1 at 3.5 mg silt · l-1, and decreased at higher and lower concentrations. Increasing amounts of material were retained by the gills with increasing silt concentration, but an increasing proportion of this was rejected as pseudofaeces. Pseudofaeces was produced at silt concentrations above 1 mg · l-1, and the amount produced increased lineally with the amount of material retained (regression line: pseudofaeces produced (mg · min-1) = 0.98 x material retained (mg · min-1) - 0.057; r = 0.98). Dry matter ingestion increased with increasing concentration of silt. (Regression line: ingestion rate (μg · min-1) = 4.36 x In concentration (mg · l-1) + 31.98; r = 0.52). The mussels were able to select between algae ...

The influence of suspended, natural silt (0 to 20 mg l-1) in addition to unicellular algal cells (Phaeodactylum tricornutum) (o to 20.000 cells ml-1) on clearance, growth and energetics in Mytilus edulis has been studied. Clearance increased by 32 to 43% by the addition of 5 mg silt l-1 as compared to clearance in a pure algal suspension. Ingestion and growth rate increased with algal concentration, and growth rate was further increased by 30 to 70% by the addition of 5 mg silt l-1. A growth rate comparable to maximum natural growth rates was reached only at the highest algal concentration in the presence of 5 mg siltl-1. Assimilation efficiency of P. tricornutum decreased from 77% at 5,000 cells ml-1 to 52% at 20,000 cells ml-1. In the experiments with silt added, some 20 to 30% of the assimilated organic matter originated from the suspended bottom material. Net growth efficiency increased with growth rate at a decelerating rate, approaching a maximum of about 70%. It is concluded that suspended bottom material, which is always present in M. edulis' natural habitats, serves as an additional food source, and that M. edulis depends on suspended bottom material to exploit fully its clearance potential, and to reach the maximum growth rates observed in nature.

A filter feeding bivalve, represented by the mussel Mytilus edulis, is modelled as a pump, consisting of the bands of lateral cilia along the gdl filaments, and a system of afferent and efferent canals. The relation between pump pressure a H p and pumping rate V was approached through studies of the relations between system resistances and V. The most important resistances distinguished were the frictional resistance m the canal system n H l , the exit loss 'H,,, and the back pressure a H l 2 , imposed on the pump as a means to study the performance characteristics of the gill system. Removal of the laterofrontal cini from the flow path by treatment with serotonin did not measurably affect the frictional resistance, but the cirri presumably constituted a flow-rate-independent resistance nH1, , arising from their beating against the flow. Thus, in steady state, a H p = A H , + AH,, + L H , ~ -t &H1,. A H , and AH,, were linear functions of V, whereas AH,, was a quadratic function of V. At values of V up to the maximum flow rates, n H , and AH,, dominated the system resistance, and the pump characteristic was therefore approximately linear. The interfilament canals and the exhalant siphon presumably constitute the major resistances, in an optimally pumping 'standard' 35 mm mussel, thus constituting head losses of about 0.4 mm and 0.5 mm H,O, respectively. aHi1 amounted to S0.4 mm H 2 0 . The operating point at zero back pressure was estimated at about 1.4 mm H,O. Removal of the laterofrontal cirri from the flow path drastically decreased the efficiency with which S 6 pm algal particles were retained by the gills, but it had no or little effect on the retention of 14 urn particles, supporting previous lndlcations that the laterofrontal cirri do not act as sieves of the through current, but rather as modulators in the process of particle retention. Power output of the 35 mm mussel at zero back pressure was 14 pW, only slightly lower than the maximum of 15 pW. The work done by the pump constituted about 1.5 % of the total aerobic metabolic rate of the mussel.

Data on fecundity and egg mortality of neritic copepods were collected in various seasons, areas and under various hydrographical conditions. On a seasonal basis variations in fecundity (F) were related to temperature rather than to the abundance of phytoplankton (P). However, a strong correlation between F and P was evident when water column stability varied horisontally or temporally (i.e. at a tidal front or subsequent to a storm). Estimated specific egg-mortalities were variable and occasionally very severe, up to 9.1 d-1, implying that down to 10-4% of the eggs survive to hatching. The implications for phenology and distribution of copepods are discussed.

In a short-term (162 h) accumulation experiment with mussels Mytilus edulis exposed to 100 ppb Cd and fed algal cells (Phaeodactylum tricornutum) in 1986, it was found that uptake via food played an insignificant role compared to direct uptake from ambient water (19‰ S). From measurements of the filtration rate and Cd uptake rate, it was estimated that the fraction of Cd taken up per liter of water filtered was about 0.15%. The initial uptake of Cd was linear with time and about three times higher in fed than in starved mussels. From the measured uptake of Cd in starved mussels collected in 1982 and exposed to 10, 100 and 200 ppb in long-term experiments (up to 242 d), it was found that the Cd Accumulation rate was not linear with time, and that the Cd uptake was not directly proportional with the exposure concentration. Values as high as 100 to 1 300 ppm Cd (dry wt of soft parts) were measured. It was found that the Cd elimination rate was not directly proportional with the Cd body burden in long-term exposed mussels, thus indicating that a certain fraction of Cd may have been immobilized to metallothioneins.

Behavioural effects of marine sediment contaminated with pesticides (6000 ppm parathion, 200 ppm methyl parathion, 200 ppm malathion) were studied in a number of marine organisms in laboratory tests and in situ . The burrowing behaviour in Macoma baltica, Cerastoderma edule, Abra alba, Nereis diversicolor and Scoloplos armiger was impaired in the contaminated sediment compared to control. The impairment was most pronounced in the laboratory tests, where almost no burrowing occured. In a very simple laboratory set-up, highly significant avoidance of the contaminated sediment was demonstrated for Crangon crangon and Solea solea , but not for Carcinus meanas and Pomatoschistus minutus . The validity of both behavioural tests was supported by in situ observations and investigations on the distribution of the species. It is concluded that both tests are useful tools in the assessment of the impact of contaminated sediments.

During a spring phytoplankton bloom in the Kattegat and Skagerrak area (Denmark) comparisons were made of the natural feeding rates obtained by four different methods of seven species of planktonic copepods. Measurements of gut contents (gut fluorescence) of freshly caught copepods were converted into estimates of in situ algal grazing rates by means of independently estimated gut turnover times, and were compared with chlorophyll and particle-volume grazing rates of animals sampled simultaneously and incubated in water from the collection depth. In addition, egg-production rates of adult females were measured during incubation, and converted to crude estimates of ingestion rate by assuming 33% gross production efficiency. The four methods yielded similar grazing rates with the gut fluorescence method generally yielding the highest and the egg-production method the lowest estimates. The methodological problems of the different methods are discussed, and it is concluded that they all approach representative (although minimum) estimates of in situ feeding rates.

Correlations between rates of ventilation and oxygen consumption in filter feeders are usually interpreted in terms of causal relations, but authors disagree on whether ventilation is regulated to meet respiratory needs or whether oxygen consumption reflects energetic costs of water transport. It seems, however, that neither causality applies, the correlations being determined by physical characteristics of the ventilatory systems. The ventilatory currents both in a tube dwelling worm, Urechis caupo, and in bivalves, such as Mytilus edulis, are laminar, and oxygen in the water is available to the animals solely by diffusion. Various estimates of the diffusive boundary layer 6, developing at the interface between the ventilatory current and the body surface of U. caupo and mantle cavity in M. edulis, were in good agreement. The estimates of 6 amounted to about 0.1 mm, or a small fraction of the thickness of the ventilatory current, indicating that the larger part of the dissolved oxygen in the current is unavailable to the animals. At low rates of ventilation oxygen uptake is governed by the condition of diffusion in the ambient water. Oxygen consumption increases steeply with increasing ventilation until threshold levels are reached, and processes within the body become limiting for the rate of oxygen consumption. Oxygen consumption approaches independency of ventilation at ventilatory rates amounting to only one-fifth or less of the rates of the undisturbedly filtering animal. Regulation of respiration by means of ventilatory regulation thus seems incompatible with filter feeding in habitats that require high rates of water processing. The energetic costs of ventilation are insignificant. Presumably, in most habitats, water processing at low costs is a prerequisite for a life based on filter feeding.

An automatic recording apparatus for measuring the filtration rate in suspension-feeding bivalves is described. The concentration of algae in the experimental medium is kept constant throughout each experiment by addition of Phaeodactylum tricornutum from a chemostat. Within the range of body size 5.7 to 283 mg (W=dry weight of tissues), the filtration rate (F=ml min-1) at 15°C in Mytilus edulis L. follows the allometric equation F=0.85 W 0.72. Within the concentrations 0.18 to 0.70 mg algal dry weight l-1, the filtration rate in mussels of 132 mg dry flesh weight ranges from 33.1 to 41.0 ml min-1. At 0.18 mg algal dry weight l-1 the mussels filter continuously for 20 h, with a high constant rate that presumably represents the water transport capacity under optimal laboratory conditions.

The influence of suspended bottom material (0–25 mg · l−1) in addition to algal cells (Phaeodactylum tricornutum) (0–500 µg dry org wt · l−1) on clearance, growth and energetics in Spisula subtruncata (da Costa) has been studied. Clearance and respiration rate were independent of concentrations of algae and suspended bottom material. Algal ingestion rate was proportional to algal concentration, and independent of the concentration of suspended bottom material. Growth rate increased with algal concentration, and was further increased by 10 to 110 % by the addition of suspended bottom material. The positive effect of suspended bottom material on growth is due to a higher efficiency of assimilation of the ingested algae and/or to the utilization of organic matter in the suspended bottom material. The efficiency of algal assimilation decreased from 76 % at a low (150 µg dry org wt · 1−1) to 33 % at a high (500 µg) algal concentration in specimens fed pure suspensions of algae. The water processing po...

Growth and oxygen consumption was measured in developing herring Clupea harengus (L.) embryos. By considering the variations in oxygen consumption with embryonic size and growth rate, an attempt was made to partition oxygen consumption between growth related and growth unrelated (i.e., “maintenance”) processes. The metabolic cost of growth was estimated as ≈ 150 ng O 2 · μg dry wt tissue formed −1 . This estimate compares favourably with the biochemical estimate of the costs of transport and net biosynthesis. The “maintenance” component was proportional to embryonic mass (77 ng O 2 · μg −1 · d −1 ). Over the entire embryonic period, growth processes were responsible for ≈ 25% of the cumulated oxygen consumption.

A new sampling system for quantitative zooplankton studies is described. It consists of a centrifugal pump and a plankton net combined in a single submersible unit. The performance of the net-pump was compared to vertical hauls with a 100-µm WP-2 net on two occasions characterized by large differences in zooplankton biomass. The filtration efficiency of the WP-2 net decreased steadily, due to clogging, from ca. 100% at the onset of sampling (25 m) to about 50% at the surface. Clogging in the net-pump was not observed even after prolonged sampling. In vertical hauls, the capacity of the net-pump (420 1 · min-1) was sufficient to catch even adult Calanus finmarckicus quantitatively. Used in the stationary mode at fixed depths, most adult C. finmar chicus escaped from the pump intake. The volume filtered by the net-pump was only a fraction of the volume filtered by the WP-2 net. However, the total variation (variation among samples + subsample error) was identical (May) or markedly lower (October) f...

A method for determining filtration rates in undisturbed suspension-feeding bivalves is described. Concentrations of particulate matter in the water collected in the inhalant (Ci) and exhalant (Ce) currents were estimated with an electronic particle counter. The clearance was calculated as \(Y = Fl(1 - \frac{{C_e }}{{C_i }})\), where Fl=flow rate through the tube collecting exhalant water. Only above critical levels of water flow (Fl) were clearances representative of filtration rates. At 10° to 13°C, the filtration rates (F, 1 h-1) within one or two orders of magnitude of dry weight (w, g), in Cardium echinatum L., C. edule L., Mytilus edulis L., Modiolus modiolus (L.) and Arctica islandica (L.) followed the allometric equations: 4.22w0.62, 11.60w0.70, 7.45w0.66, 6.00w0.75 and 5.55w0.62, respectively. Five species of bivalves [Spisula subtruncata (da Costa), Hiatella striata (Fleuriau), Cultellus pellucidus (Pennant), Mya arenaria L. and Venerupis pullastra (Montagu)] filtered with the same rates as individuals of Cardium echinatum and A. islandica of equivalent soft weight. In Pecten furtivus and P. opercularis filtration rates were about twice the rates measured in individuals of Mytilus edulis of comparable body weight. The gill area in M. edulis increases with size at the same rate as the filtration rate.

Ingestion rate, gut clearance rate and gut content were measured in the laboratory in adult females of the planktonic copepod Centropages hamatus fed the centric diatom Ditylum brightwelli. Ingestion rate increased with algal concentration approaching a maximum rate equal to 85 % body C · d−1 at 15 °C. Within the temperature interval studied (1–15 °C), maximum ingestion rate increased with temperature with a Q10 of 3.9. Gut clearance rate was estimated by following the exponential decrease in the gut content of plant pigments (measured fluoremetrically) with time after feeding, and showed approximately the same temperature dependence (Q10 = 3.3) as ingestion rate. The relationship between gut content and algal concentration was described by an equation similar to that relating ingestion rate to algal concentration. Gut content multiplied with gut clearance rate, which can be considered an estimate of ingestion rate, yielded values similar to ingestion rates actually measured. This implies that in...

Accumulation rates of cadmium, the amount of food ingested and assimilated, the amount of oxygen consumed and changes in dry flesh weight have been measured in Mytilus edulis L. exposed to 0, 10 and 100 ppb cadmium for 17 d in aquaria with seawater flowing continously and at constant algal concentration. The accumulation rates were linear at 10 and 100 ppb, amounting to 0.58 and 8.89 ppm d-1, respectively. Body loads up to 150 ppm caused no effects on either clearance, ingestion, assimilation, respiration, or growth. High net growth efficiencies between 55–59% were obtained, indicating near optimal experimental conditions. It is suggested that the setup and experimental procedure provide an excellent tool in the study of accumulation and sublethal effects of environmental pollutants in suspension feeding bivalves.

Seasonal and diel variation in rate of algal grazing were estimated from measurements of gut content (plant pigments) and gut turnover in the copepods Centropages hamatus and Pseudocalanus sp. during spring (Januar–May) in the Oresund. Both species exhibited significant diel variation in gut content and ingestion rate at the three depths studied (5, 10 and 22 m), with the highest ingestion rates and gut contents during night. The variation was most pronounced in March, but almost insignificant in April. Since the copepods did not migrate vertically, the observed pattern is due to a variable feeding activity rather than caused by continuous feeding at varying food concentrations. We found a positive correlation between ambient algal concentration and algal ingestion rate and gut content for both species in weekly morning samples. The results indicated satiation of the ingestion rates at high algal concentrations. Maximum algal ingestion rates measured in the field were similar to maximum ingestion...

In safety assessments of underground radioactive waste repositories, understanding radionuclide fate in ecosystems is necessary to determine the impacts of potential releases. Here, the reliability of two mechanistic models (the compartmental K-model and the 3D dynamic D-model) in describing the fate of radionuclides released into a Baltic Sea bay is tested. Both are based on ecosystem models that simulate the cycling of organic matter (carbon). Radionuclide transfer is linked to adsorption and flows of carbon in food chains. Accumulation of Th-230, Cs-135, and Ni-59 in biological compartments was comparable between the models and site measurements despite differences in temporal resolution, biological state variables, and partition coefficients. Both models provided confidence limits for their modeled concentration ratios, an improvement over models that only estimate means. The D-model enables estimates at high spatio-temporal resolution. The K-model, being coarser but faster, allows estimates centuries ahead. Future developments could integrate the two models to take advantage of their respective strengths. Electronic supplementary material The online version of this article (doi:10.1007/s13280-013-0398-2) contains supplementary material, which is available to authorized users.

Partitioning of inorganic and organic mercury was studied in the cockles Cardium edule and C. glaucum sampled in a chronically polluted area in the Western Limfjord, Denmark. The proportion of organic mercury in the cockles was linearly correlated to age (and weight) but not to total mercury concentration in the cockles. In 2-, 3- and 4-year-old cockles organic mercury constituted c. 30%, 60%, and 90% of total mercury, respectively. The age correlated proportion of organic mercury is discussed in a food chain context.

The rapidly growing field of three-dimensional software modeling of the Earth holds promise for applications in the geospatial health sciences. Easy-to-use, intuitive virtual globe technologies such as Google Earth™ enable scientists around the world to share their data and research results in a visually attractive and readily understandable fashion without the need for highly sophisticated geographical information systems (GIS) or much technical assistance. This paper discusses the utility of the rapid and simultaneous visualization of how the agents of parasitic diseases are distributed, as well as that of their vectors and/or intermediate hosts together with other spatially-explicit information. The resulting better understanding of the epidemiology of infectious diseases, and the multidimensional environment in which they occur, are highlighted. In particular, the value of Google Earth™, and its web-based pendant Google Maps™, are reviewed from a public health view point, combining results from literature searches and experiences gained thus far from a multidisciplinary project aimed at optimizing schistosomiasis control and transmission surveillance in sub-Saharan Africa. Although the basic analytical capabilities of virtual globe applications are limited, we conclude that they have considerable potential in the support and promotion of the geospatial health sciences as a userfriendly, straightforward GIS tool for the improvement of data collation, visualization and exploration. The potential of these systems for data sharing and broad dissemination of scientific research and results is emphasized.

Particle selection was studied in 10 species of suspension-feeding bivalves by comparing the proportion of algae in the pseudofaeces with that in the surrounding water. All species examined exhibited particle selection, but with different efficiencies. Spisula subtruncata was most efficient, followed, in decreasing order of efficiency, by Corbula gibba, Mytilus edulis (from Wadden Sea) , Acanthocardia echjnata, Aequipecten opercularis, Musculus niger, Crassostrea gigas, Mya arenaria, Cerastoderrna edule, Mytilus e d u l ~ s (from Qresund), and Arctjca ~s landica . Selection efficiency correlated with the size of the labial palps. Particles rejected as pseudofaeces were embedded in mucus, whereas ingested particles were always in free suspension in M. edulis. Apparently, then, different particles have different probabilities of being trapped in mucus, and thus rejected as pseudofaeces. The properties which determine this probability are unknown.

Projektets hovedformål er at undersøge stenrevs potentielle kvælstofeffekt med henblik på at kunne inddrage stenrev som et muligt supplerende virkemiddel i vandplanlægning. Projektet omfatter etablering og analyse af et pilotstenrev i Løgstør Bredning samt analyser af stenrevs kvælstofeffekt på eksisterende stenrev. Projektet vil endvidere bidrage til opfyldelse af mål om opnåelse af gunstig bevaringsstatus for Limfjordens rev. Et modelprojekt fra 2008 viste, at stenrev potentielt og under særlige betingelser kan medvirke til at mindske effekterne af kvælstoftilførsler til visse kystvande (DHI & DMU, 2008). I forbindelse med en efterfølgende screening af potentielt egnede lokaliteter har DHI skønnet, at der på landsplan findes 3-4 lokaliteter, hvor stenrev muligvis kan genetableres med henblik på en kvælstofeffekt (DHI & DCE, 2013). Løgstør Bredning i Limfjorden er et af disse områder. Den potentielle kvælstofeffekt er imidlertid ikke dokumenteret og kvantificeret. På denne baggrund gennemfører Limfjordsrådet i partnerskab med Miljø- og Fødevareministeriet et 5-årigt forsknings- og udviklingsprojekt i Løgstør Bredning, Limfjorden, som skal dokumentere stenrevs potentielle kvælstofeffekt og bidrag til at opnå god økologisk tilstand i samarbejde med Aarhus Universitet, DTU Aqua, DHI, GEUS og NIVA Danmark. Projektet omfatter målinger på eksisterende stenrev samt etableringen af et nyt stenrev og målinger herpå. Projektet vil bidrage til at genoprette naturtypen stenrev og dermed også bidrage til at forbedre Natura 2000 områdets bevaringsstatus. Projektets resultater skal indgå som tekniske anvisninger i forbindelse med virkemiddelkataloget for vandområdeplanerne 2021-2027. Der udarbejdes en samlet syntese af stenrevs potentielle kvælstofeffekt, herunder dokumentation af hvordan organismer på et stenrev reagerer på varierende lysforhold og lav iltkoncentration.

Kystnære stenrev på mindre end 10 m's dybde er alvorligt påvirket. Påvirkningen er sket ved et omfattende stenfiskeri, som gennem mere end en hundredårig periode har fjernet de større sten fra stenrevene og dermed ændret deres dybdeudbredelse og kan gøre det resterende rev ustabilt. Stenene er blevet brugt til udbygning af havne og andet entreprenørarbejde. DTU Aqua har interviewet gamle stenfiskere og fået tilgang til logbogsoplysninger og notater. Vi kan derfor give et detaljeret billede af, hvordan og hvor stenrevene er blevet fisket op. Disse historiske oplysninger vil blive sammenholdt med nye opmålinger af stenrev foretaget af DCE og GEUS. Stenrevenes nuværende status og biologisk funktion for makroalger, fauna og fisk og de sandsynlige effekter af det nu ophørte stenfiskeri vil blive diskuteret på baggrund af tidligere og igangværende forskningsprojekter og overvågningsprogrammer, der dokumenterer, at tætheden af makroalger, totale fauna biomasse og at fiskefaunaens artsdiversitet og biomasse er signifikant højere på stabile stenrev sammenlignet med den omkringliggende ralbund, og at stenrevets dybde er af afgørende betydning. Vi vil endvidere demonstrere, på baggrund af en højopløst hydrodynamisk model af et stenrev, at der kan etableres sammenhænge mellem foretrukne habitater og strømhastigheder, samt variationer i salt og temperatur. Sådanne sammenhænge kan anvendes til at målrette indsatsen ved evt. genetablering af stenrev.