Population biology of hyperbenthic crustaceans in a cold water environment (Conception Bay,Newfoundland). I.<Emphasis Type="Italic"> Mysis mixta</Emphasis> (Mysidacea)

Seasonal population dynamics of Mysis mixta Lilljeborg were studied from December 1998 to November 2000 at a 240 m deep site in Conception Bay, Newfoundland. At this depth, temperature was <0°C and salinity between 32.0 and 34.0 psu year-round. The spring phytoplankton bloom began in early or late March and reached a maximum in late April to mid-May. M. mixta exhibited a highly synchronised life cycle, with spawning and mating occurring in October to November, embryos brooded for ~5 months, and juveniles released during spring bloom sedimentation in April and May. Females were semelparous and died at age 2.5 years, following release of juveniles in spring, whereas the majority of mature males died at age 2 years, following mating in November. The biennial life cycle of this population resulted in the presence of two cohorts in the hyperbenthos at any given time. Variation in density and biomass was low among cohorts but high within cohorts, the latter probably due to the high motility of mysids. Densities in 1999 and 2000 were 242±379 and 544±987 ind. per 100 m³ (mean±SD), respectively. Although growth rates were similar between years, rates measured from changes in dry mass differed both seasonally and among life-history stages (range from –4 to 7 mg month^–1). Annual secondary production was estimated at 29–73 mg C m^–2 in 1999 and 53–205 mg C m^–2 in 2000. The annual P/B ratios were 1.62 and 1.19 in 1999 and 2000, respectively.Communicated by J.P. Grassle, New Brunswick     

Growth and grazing loss rates in single-celledPhaeocystis sp. (Prymnesiophyceae)

Growth and grazing loss rates of naturalPhaeocystis sp. single cells were measured using a seawater dilution technique. Measurements were performed during an intensePhaeocystis sp. bloom in the North Sea between 19 April and 5 May 1988. Experimental results yielded rapid carbon turnover rates. Population growth rates varied from 0.033 to 0.098 h^–1, grazing loss rates from 0.037 to 0.174 h^–1. From measured growth rates, average doubling rages of 1.3 doublings d^–1 were calculated. The growth rates would have resulted in maximum carbon production rates of 146 mg C m^–3 d^–1. Grazing rates increased in the course of the bloom and exceeded growth rates at the end. Grazing loss was caused primarily by microzooplankton feeding. Ciliates and heterotrophic dinoflagellates were identified as the major potential consumers of single cells ofPhaeocystis sp. at the beginning of the bloom. The grazing impact of larger microzooplankton species appeared to increase during the progressing bloom.     

Interannual variability in the spring phytoplankton bloom in Auke Bay,Alaska

Data on phytoplankton primary production, biomass, and species composition were collected during a 5 yr (1985–1989) study of Auke Bay, Alaska. The data were used to examine the interannual differences in the timing, duration, and magnitude of the spring phytoplankton blooms during each year and to relate these differences to interannual variations in weather patterns. Within any given year, a pre-bloom phase was characterized by low available light, low rates of primary production, low biomass, and predominantly small (<10µm) diatoms. During the primary bloom, integrated production rates rose to 4 to 4.5 g C m^–2 d^–1, and integrated biomass levels reached 415 to 972 mg chlorophyll m^–2. Primary blooms were usually dominated by large diatoms (Thalassiosira spp.), and in a single year (1989) byChaetoceros spp. The primary blooms terminated upon nutrient depletion in the euphotic zone. Secondary blooms, triggered by nutrient resupply from below, occurred sporadically after the primary bloom and accounted for 4 to 31% of total spring production. The date of initiation and the duration of the primary bloom varied little from year to year (standard deviation 3 and 5 d, respectively). Seasonal production rates and biomass levels varied interannually by a factor of 2 to 3. In contrast, intra-annual variations of more than an order of magnitude, especially in biomass, occurred over periods as short as 10 d. These large variations over short time periods indicate the importance of synchronous timing between spring blooms and the production of larval fish and shellfish, which depend on an appropriate and adequate food supply for growth and survival. Parameters describing primary production (e.g. peak daily production, mean daily production, and total production during the primary bloom and the entire season) exhibited little interannual variation (coefficient of variation, CV = 10 to 19%), but a large degree of intra-annual variation (CV = 77 to 116%). Similarly, interannual variations in biomass (peak chlorophyll, mean chlorophyll) were also lower (CV = 20 to 33%) than intra-annual variations (CV = 85 to 120%).     

Distribution and abundance of choanoflagellates (Acanthoecidae) in the coastal cold ocean of Newfoundland, Canada

Water samples from six bays were taken over a 5-year period (1988 to 1992) to determine the distribution and abundance of loricate choanoflagellates in coastal Newfoundland, and to assess the impact that these organisms might have on this cold ocean food web. Scanning electron microscopy was used to study the morphology of these flagellates, allowing us to identify 11 species of loricate choanoflagellates. Parvicorbicula socialis (Meunier) Deflandre was the most abundant species (80 × 10³ cells l⁻¹), particularly during the spring diatom bloom. Single-cell species, such as Bicosta spini fera (Throndsen) Leadbeater and Calliacantha natans (Grontved) Leadbeater, were found more commonly after the spring diatom bloom in the summer months. Many of the single-cell choanoflagellates were attached to bacteria-rich microaggregates and debris in the water column and in unpoisoned sediment traps. The P. socialis cell flux was calculated to be 5.3 × 10⁶ cells m⁻² d⁻¹ in late May sediment traps. P. socialis in the upper 100 m of the water column was removing 0.3% of the standing crop of bacteria each day (April/May), and the equivalent of 7.4% of the daily bacterial production over the water column. Diel studies of P. socialis in Conception Bay suggest that the sharp decline in population numbers observed in midnight samples may be related to the high number of grazing zooplankton observed during the same period. Pelagic tunicate and zooplankton fecal pellets were found to contain large numbers of choanoflagellate costae, thus providing a direct link from the microbial loop to the macrozooplankton. Received: 17 March 1997 / Accepted: 9 May 1997     

Estimating carbon flux to pelagic grazers in the ice-edge zone of the eastern Bering Sea

Zooplankton ingestion of phytoplankton carbon in the iceedge zone of the Eastern Bering Sea was measured using a deck incubation approach in 1982. Using further samples collected in 1983, the plant cell carbon to cell volume ratio was estimated at 0.0604 pg m^–3 from an experimentally determined particulate carbon to seston volume relationship. The application of this conversion to the results of experimental incubations of natural plant stocks with net-caught zooplankton produced ingestion rates of 68.8 and 10.26 mg C g^–1 grazer d^–1 for copepods and euphausiids, respectively. Extrapolating these rates to in situ zooplankton biomass at the edge of the seasonal ice pack yielded carbon flux rates through the zooplankton community ranging between 6.5 and 32.8 mg C m^–2 d^–1. This consumption amounted to less than 2% of the daily phytoplankton production in the ice-edge zone.     

Effect of algal bloom deposition on sediment respiration and fluxes

Using sediment cores collected in November 1989 from Aarhus Bight, Denmark, the fluxes of O₂, CO₂ (total CO₂), NH ₄ ⁺ , NO ₃ ^– +NO ₂ ^– and DON (dissolved organic nitrogen) across the sediment-water interface were followed for 20 d in an experimental continous flow system. On day 7, phytoplankton was added to the sediment surface, to see the result of simulated algal bloom sedimentation. Benthic O₂ consumption and CO₂ efflux, 38 to 41 mmol O₂ m^-2 d^-1 and 25 to 30 mmol CO₂ m^-2 d^-1, respectively, immediately increased by 39% and 100% after the algal addition, but gradually declined to the orginal level. Fluxes of NH ₄ ⁺ (1.0 to 1.2 mmol m^-2 d^-1) and DON (0.3 to 0.9 mmol m^-2 d^-1) increased due to the organic substrate addition. NH ₄ ⁺ and NO ₃ ^– flux changed direction, becoming an efflux and influx, respectively, for a few days and a large amount of DON (max. rate 4.0 mmol m^-2 d^-1) was immediately produced either by bacterial hydrolytic activity or from autolysis of the algae. DON was the most significant nitrogen component in pore water and in terms of N-flux from sediment. A temporary stimulation of anaerobic respiration processes (sulfate reduction and denitrification) and a decrease in nitrification were indicated. After the effect of the organic addition had declined, the fluxes gradually reverted to the original rates. The halflife of the added algal material, of which 20 to 30% was very labile, was estimated to be 2 to 3 wk.     

Sedimentation of particulate matter during a phytoplankton spring bloom in relation to the hydrographical regime

Data presented and discussed here were collected continuously during April/May 1975 in the Bornholm Basin of the Baltic Sea. Sedimentation rates of particulate matter were recorded with 5 multisample sediment traps from different depths in the water column at 2 positions 170 km apart. Current meter data collected during the same period and depths indicated that the positions remained hydrographically distinct during the investigation. Particulate matter from the euphotic zone including diatom cells formed the bulk of the material collected by all traps. This flux of organic particles to the bottom was unimpeded by the strong density stratification present in the water column. The upper traps always collected less material than lower ones. This paradox has been ascribed to diminishing current speeds with depth, concomitant with an increase in sinking rates of phytoplankton and phytodetritus. Both factors influence the sampling efficiency of sediment traps, which are thought to have underestimated actual sedimentation rates here. A time lag of 2 to 3 weeks in bloom development seemed responsible for the characteristic differences between the two positions. The phase of major sedimentation at one position covered about 18 days, and a distinct sequence in the composition of the material collected by the 6 glasses of each trap indicated phases of a progressively deteriorating phytoplankton population in the water column contributing the particulate material. A total of 6.2 g C m^-2 in 34 days was recorded at this station. Apart from a trap situated in an oxygen deficient layer which collected 0.44 g C m^-2 of zooplankton corpses, zooplankton mortality was overestimated by the traps. Large-scale sedimencation of fresh organic matter produced by the spring bloom is probably a regular feature in areas with low over-wintering zooplankton populations and, as such, possibly has a direct stimulatory effect on growth and reproduction of the benthos.Contribution No. 185 of the Joint Research Programme 95, Kiel University.     

Species-specific sedimentation and sinking velocities of diatoms

Sedimentation rates were determined for various diatom species, and both average and maximum sinking velocities of sedimenting diatoms were calculated during a spring bloom investigation in the central Baltic Sea in 1986. Up to 25 and 50% of theChaetoceros spp. andThalassiosira levanderi populations, respectively, sedimented daily. Daily sedimentation rates of other diatoms, dinoflagellates andMesodinium rubrum, however, were less than 1% of their respective standing stocks. TheT. levanderi population was divided into two subpopulations: while one was sinking, the second was actively dividing (recognizable by paired-cell stages) with a specific growth rate of >0.2 to 0.3 d^–1. These paired cells were never found in sediment trap samples. The average sinking velocity ofChaetoceros spp. was 15 to 30 m d^–1; that ofT. levanderi was higher. The maximum sinking velocity of cells was at least 70 m d^–1. According to these observations, the formation of aggregates (which enhances sinking velocity), and their sedimentation, represent a highly selective process. This indicates that diatom aggregates do not act as roving filters, sweeping the water clear while sinking.     

Annual abundance and biomass of aloricate ciliates in tropical neritic waters off Kingston,Jamaica

The daily abundance of aloricate ciliates at Lime Cay, Jamaica, a shallow neritic site, ranged from 29 to 118 × 10⁶ m^–2 (0.97 to 3.93 × 10⁶ m^–3) between November 1985 and November 1986. Biomass was converted to kilojoules (1 kcal=4.1855 kJ) assuming 42% carbon, 20.15 kJ (g dry wt)^–1, and 20% cell shrinkage. Biomass ranged from 0.40 to 3.00 kJ m^–2 (13.3 to 100 J m^–3; 0.28 to 2.08µg C l^–1) with an annual mean of 1.11 kJ m^–2 (36.8 J m^–3; 0.764µg C l^–1). Nanociliates (<20µm equivalent spherical diameter, ESD) dominated abundance, but microciliates (> 20µm ESD) dominated biomass.Strombidium, Strobilidium, Tontonia andLaboea species were conspicuous taxa. Annual production estimates of the aloricate assemblage, based on literature growth rates, ranged from 404 kJ m^–2 yr^–1 (37 J m^–3 d^–1) to 1614 kJ m^–2 yr^–1 (147 J m^–3 d^–1). A compromise estimate of 689 kJ m^–2 yr^–1 (i.e., 63 J m^–3 d^–1) is comparable to other estimates from tropical and subtropical regions. A model of annual energy flow through 11 planktonic compartments suggests the total ciliate assemblage (aloricates and tintinnines) to be as productive as metazoan herbivores and metazoan carnivores.     

Phytoplankton production patterns in Massachusetts Bay and the absence of the 1998 winter–spring bloom

The seasonal productivity cycle and factors controlling annual variation in the timing and magnitude of the winter–spring bloom were examined for several locations (range: 42°20.35′–42°26.63′N; 70°44.19′–70°56.52′W) in Boston Harbor and Massachusetts Bay, USA, from 1995 to 1999, and compared with earlier published data (1992–1994). Primary productivity (mg C m⁻² day⁻¹) in Massachusetts Bay from 1995 to 1999 was generally characterized by a well-developed winter–spring bloom of several weeks duration, high but variable production during the summer, and a prominent fall bloom. The bulk of production (mg C m⁻³ day⁻¹) typically occurred in the upper 15 m of the water column. At a nearby Boston Harbor station a gradual pattern of increasing areal production from winter through summer was more typical, with the bulk of production restricted to the upper 5 m. Annual productivity in Massachusetts Bay and Boston Harbor ranged from a low of 160 g C m⁻² year⁻¹ to a high of 787 g C m⁻² year⁻¹ from 1992 to 1999. Mean annual productivity was higher (mean=525 g C m⁻² year⁻¹) and more variable near the harbor entrance than in western Massachusetts Bay. At the harbor station productivity varied more than 3.5-fold (CV=40%) over an 8 year sampling period. Average annual productivity (305–419 g C m⁻² year⁻¹) and variability around the means (CV=25–27%) were lower at both the outer nearfield and central nearfield regions of Massachusetts Bay. Annual productivity in 1998 was unusually low at all three sites (<220 g C m⁻² year⁻¹) due to the absence of a winter–spring phytoplankton bloom. Potential factors influencing the occurrence of a spring bloom were investigated. Incident irradiance during the winter–spring period was not significantly different (P > 0.05) among years (1995–1999). The mean photic depth during the bloom period was significantly deeper (P < 0.05) in 1998, signifying greater light availability with depth. Nutrients were also in abundance during the winter–spring of 1998 with stratified conditions not observed until May. In general, the magnitude of the winter–spring bloom in Massachusetts Bay from 1995 to 1999 was significantly correlated with winter water temperature (r ²=0.78) and zooplankton abundance (r ²=0.74) over the bloom period (typically February–April). The absence of the 1998 bloom was associated with higher than average water temperature and elevated levels of zooplankton abundance just prior to, and during, the peak winter–spring bloom period. Received: 3 July 2000 / Accepted: 6 December 2000     

Mass encystment of a planktonic oligotrich ciliate

Sediment traps were deployed in a 60 m water column near the Eddystone Lighthouse on the south west coast of England for one year from March 1984. In April, the traps collected the cysts of a planktonic ciliate with a flux of almost 35 000 m^-2 d^-1. The cysts were attributed to a planktonic oligotrich [provisionally identified as Strombidium crassulum (Leegard) Kahl], which was common in the water at the time. Identification was achieved through the discovery of the incipient formation of the cysts in preserved water samples and by the similarity of the morphology of the cysts with that of other oligotrichid ciliates. Attempts to prove the relationship by incubation have so far failed. The production of the cysts followed the main spring bloom of diatoms and coincided with a small bloom of autotrophic oligotrichs. In the traps, the total number and percentage of cysts with contents decreased rapidly after the encystment event. However, potentially viable cysts were still recorded in the plankton eleven months later, with minimum fluxes of 200 cysts m^-2 d^-1. Resuspension of bottom sediments by tides and storms ensured that a large population of cysts was always present in the water column during the winter, awaiting the right conditions to stimulate excystment and the initiation of a new motile population.     

Egg production and feeding by copepods prior to the spring bloom of phytoplankton in Fram Strait,Greenland Sea

Reproductively activeCalanus hyperboreus (Krøyer) andC. glacialis Jaschnov were captured in the upper 100 m of Fram Strait (77° to 79°N) in late winter 1987. There was no evidence of a phytoplankton bloom; chlorophylla concentrations were uniformly low (<0.1 mg m^–3), and nitrate concentrations were uniformly high (>11.3 mg-at m^–3). Gut-fullness measurements indicated that females were ingesting very little. The maturation state of gonads of bothC. hyperboreus andC. glacialis indicated that 75% of females were in a ripe condition consistent with observed egg laying. The lipid content of females laying eggs was reduced in both species compared to that of females not laying eggs. InC. hyperboreus the reduction was 39% and inC. glacialis it was 44%. All the evidence suggests that bothC. hyperboreus andC. glacialis were laying eggs in late winter by using lipids stored previously; they were not relying on ambient concentrations of phytoplankton. The daily rate of egg laying byC. glacialis using lipids in late winter exceeded the rate reported for summer when ambient food supplies have been shown to be necessary. It is suggested that individuals, spawned well in advance of the spring bloom of phytoplankton, may comprise a major portion of the annual recruitment to the entire population ofC. glacialis in this area, and that their life cycle can be completed within 1 yr. NeitherMetridia longa (Lubbock) norC. finmarchicus (Gunnerus) laid eggs during this study.     

Plankton of the fladen ground during FLEX 76 II. Population dynamics and production of Thysanoessa inermis (Crustacea: Euphausiacea)

Samples taken in the northern North Sea with the Continuous Plankton Recorder (CPR), the Undulating Oceanographic Recorder (UOR) and the Longhurst-Hardy Plankton Recorder (LHPR) during the Fladen Ground Experiment in 1976 (FLEX 76) are used to describe the vertical distribution and population dynamics of Thysanoessa inermis (Krøyer) and to provide estimates of the production and carbon budget of the population from 19th March to 3 June 1976. Spawning occurred in late April and early May, in near synchronisation with the start of the spring bloom of phytoplankton. Eggs, nauplii and calyptopes reached maximum abundance in succession, and furciliae were numerous when sampling ceased in early June. Adults increased in length from a mean of 12.1 mm in mid-March to 17.5 mm in early June and the estimated production was 2.40 mg m^-3 over the 74 d period. Total carbon ingested by the population of T. inermis was estimated to be 10 mg C m^-2 d^-1 in the upper 100m which was only 1.5% of the daily primary production of 0.68 gC m^-2 measured over the FLEX period 26 March to 4 June 1976. The grazing by T. inermis on the phytoplankton population was assumed to have little effect on the control and depletion of the spring phytoplankton bloom during FLEX 77.JOSDAP Contribution No. 50     

Effect of monsoonal climate on sulfate reduction in coastal sediments of the central Great Barrier Reef lagoon

Rates of sulfate reduction were measured during the spring dry and summer wet seasons of 1992 in shallow coastal sediments of the central Great Barrier Reef lagoon. In the dry season, sulfate reduction rates, integrated to 18–20 cm depth, ranged from 23.8 to 30.8 mmol S m^-2 d^-1. In the wet season, heavy monsoonal rains and wind-induced waves caused severe disturbance of sediments leading to less anoxic conditions, and to a 2- to 3-fold decline in rates of sulfate reduction (10.2 to 12.8 mmol S m^-2 d^-1). The percentage of reduced ³⁵S recovered as acid-volatile sulfide (% AVS_red) ranged from 15.8 to 44.9% in spring, and was significantly reduced at each station in summer (range 14.5 to 31.4%). An analysis of variance indicated that seasonality accounted for 31.5% of the total variance in total rates of sulfate reduction, with only 7.5% of the variance accounted for by depth into the sediment; there were no station differences. In both seasons, there were no clear patterns in the proportion of radiolabel incorporated into the AVS and chromium-reducible sulfur (CRS) pools with depth into the sediment. These results are contrary to the seasonal patterns and pathways of sulfate reduction in temperate coastal sediments.     

Zooplankton biomass in the ice-covered Weddell Sea,Antarctica

Zooplankton was sampled by a Rectangular Midwater Trawl (RMT 1 + 8) in Weddell Sea surface waters (0 to 300 m) between 66 and 78°S during austral summer (February – March 1983). Sixty-nine taxa including different developmental stages were considered and divided into 16 size classes between <1 and >39.5 mm length. Biomass was determined by taxon and size class for three different meso- and macroplankton communities in the oceanic region, on the northeastern shelf and on the southern shelf of the Weddell Sea. The highest biomass of 11.2 mg DW m^–3 (3.4 g DW m^–2) was found in the northeastern shelf community (70 to 74°S), where juvenile and adultEuphausia crystallorophias accounted for 3.7 mg DW m^–3 (1.1 g DW m^–2). Although not quantitatively sampled, early copepodite stages (CI to CIII) ofCalanoides acutus andCalanus propinquus ranked second with 2.7 mg DW m^–3 (0.8 g DW m^–2). Biomass in the northeastern shelf community was concentrated in the size ranges 1 to 4 mm and 19.5 to 39.5 mm. The oceanic community of the central Weddell Sea was dominated by copepods smaller than 5 mm, which made up half of the total oceanic biomass. The tunicateSalpa thompsoni (7.0 to 8.5 mm) was the dominant single species with 1.6 mg DW m^–3 (0.5 g DW m^–2). Euphausiids, mainly juvenile and adult krillEuphausia superba, comprised 1.2 mg DW m^–3 (0.4 g DW m^–2). Total standing stock in the oceanic community was 9.4 mg DWm^–3 (2.8 g DW m^–2). Lowest biomass values were found in the southern shelf community (south of 75°S) with 4.0 mg DW m^–3 (1.2 g DW m^–2), concentrated in the 1 to 4 mm and 14.5 to 34.5 mm size classes. Abundant species were the pteropodLimacina helicina (1 to 2 mm; 0.7 mg DW m^–3; 0.2 g DW m^–2) andE. crystallorophias (24.5 to 39.5 mm; 0.9 mg DW m^–3; 0.3 g DW m^–2). The data reveal that it is essential to distinguish among subsystems in the Southern Ocean. This leads to a better understanding of the structure and function of those pelagic food webs which represent alternatives to the paradigmatic krill-centered system.     

Behavior and growth ofMercenaria mercenaria during simulated storm events

Experiments were conducted in April–August 1989 on juvenileMercenaria mercenaria (L.) in an oscillatory water tunnel to simulate resuspension of bottom sediments by waves and to determine the effects of shortterm storm events on particle ingestion, pseudofeces production, and shell growth. Juveniles (mean length = 19.2 mm) were subjected to identical concentrations of algae in both low-flow, gentle waves (maximum velocity = 7 cm s^–1) and high-velocity storm waves (maximum velocity = 22 cm s^–1). Suspended sediment levels reached 193 mg 1^–1 at 1 cm above the bed during storms. Shell growth decreased by a maximum of 38% during the storm when levels of phytoplankton were high (average cell concentration = 43 × 10⁶ cells 1^–1), and by 18% when phytoplankton levels were low (av cell conc = 6 × 10⁶ cells 1^–1). Orientation of clam siphons was not related to flow direction. Significantly more pseudofeces were produced when the clams were subjected to increased sediment resuspension under waves, and in troughs of sand ripples. The size of sediment grains ingested did not vary significantly among the flow treatments. The decrease in shell growth during storms may be due to a reduction in filtration rate coupled with a decrease in net energy gained from filtration due to costs of pseudofeces production. The magnitude of the decrease seems to be related to concentration of algae, water temperature, age of clams and sediment transport mode (bed load or suspended load). Thus, the interpretation of growth increments must be made in the context of these environmental variables.     

Benthic response to sedimentation of a spring phytoplankton bloom: Process and budget

The response of benthos to sedimentation of the spring phytoplankton bloom in the Kiel Bight (Western Baltic Sea) is described in terms of biomass (ATP) and activity (heat production and ETS-activity). Input of the bloom (11.5 g C m^-2) over a period from March 25 to April 19, 1980 to the sediment surface was in the form of cells and fresh phytodetritus as indicated by low C/N ratios (7) and high energy charge values (0.78). Benthic microbial activity was immediately stimulated by this input as heat production doubled and the activity of ETS tripled over winter values within 12 d in the absence of a significant increase in ambient temperature. A comparison of the two activity parameters suggests that anaerobic metabolism is more important during the winter (February and March) than after input of the bloom. Meiofauna was not able to take part in the first activity outburst. Benthic ATP-biomass (excluding macrofauna) doubled in late April due to microbial production, and doubled again in early May when meiofauna started reproductive activity. For macrofauna a general statement was not possible, although the sediment surface feeder Macoma baltica commenced a build up of glycogen and lipid resources immediately following bloom input whereas Nephtys ciliata, feeding on sediment and small macrofauna, showed a less pronounced and delayed effect from this input. An energy budget based on heat production measurements was calculated. A daily heat loss of the benthic community of 21.7 KJ m^-2 d^-1 (35.5 KJ m^-2 d^-1) was found, when a depth of 3 cm sediment (5 cm) was assumed. Heat production of macrofauna contributed less than 5% of this activity. The input of the bloom was burned within 21 (13) d. Preliminary estimations for an annual budget suggest that the vertical transport of particulate organic matter via sedimentation can only explain 25% (15%) of the benthic activity in the shallow water ecosystem of the Kiel Bight. This indicates the presence of other sources of organic carbon such as benthic primary production or other transport processes providing carbon to the sediments.Publication No. 384 of the Joint Research Program of Kiel University (Sonderforschungsbereich 95)     

Reproduction, dispersal and settlement of the bathyal ophiuroid Ophiocten gracilis in the NE Atlantic Ocean

  Ophiocten gracilis is an ophiuroid found at bathyal depths in the North Atlantic Ocean. The adults show strong seasonal reproduction, with an ophiopluteus in the surface plankton. Settling postlarvae were collected in sediment traps moored at 1000 and 1400 m depth in the NE Atlantic during Julian Days 142 to 212 (May to July) in 1996. During this period, growth of postlarvae in the traps was linear and the diet consisted of phytodetritus and foraminifera. Experiments suggest that postlarvae sink at rates of up to 500 m d⁻¹, although this may well be slower in the natural environment. The high fecundity, seasonality and high population density resulted in high fertilization success, and many of the offspring were advected outside the normal adult range, where they were able to settle but did not survive to adulthood. Received: 8 October 1999 / Accepted: 8 May 2000     

Copepod nutritional condition and pelagic production during autumn in Kosterfjorden,western Sweden

The in situ grazing rate and nutritional condition of copepods were studied during October/November 1985, by analyzing gut fluorescence (feeding), body size and lipid composition (nutritional state), and electron transport system (ETS) activity (respiration rate) of copepods from surface-and deep-water in Kosterfjorden on the Swedish west coast. These parameters were related to the physical and biological environment, as defined by light, hydrography, autotrophic and bacterial production and seston in the water column. The results show a gradual build-up of the autumn phytoplankton bloom in the uppermost meters, with a peak in total autotrophic production in mid October of ca 550 mg C m^–2 d^–1, and a bacterial net production corresponding to 15% of this. Phytoplankton exudates made up, on average, 47% of the primary production and more than 50% of this was utilized by the bacteria. Copepods occurring in the surface-water exhibited grazing rates corresponding to between 11 and 18% of their body C d^–1 and potential growth rates of 0 to 9% d^–1. Copepod populations in the surface water were composed of individuals with higher average body-weight and lower lipid-proportion than those from the deep-water.Calanus finmarchicus in the deep-water showed characters indicating diapause condition, while this was not observed forAcartia clausi. Differences in lipid content and composition indicate thatC. finmarchicus, Pseudocalanus sp. andA. clausi represent three successive points on a scale of tolerance for fluctuations in the food environment. Adult femaleMetridia longa was the only one among seven species/stages of copepods in the deep-water ( 50 m depth) that contained phytoplankton pigments.Study performed through Tjärnö Marine Biological Laboratory, University of Göteborg, S-452 00 Strömstad, Sweden     

Analysis of phytoplankton pigments by HPLC before,during and after mass occurrence of the microflagellate Corymbellus aureus during the spring bloom in the open northern North Sea in 1983

Daily observations in April and May 1983 near a subsurface drifter launched in the Fladen Grounds area of the North Sea revealed that a large crop of the microflagellate Corymbellus aureus Green, producing up to 3 g C m^-2 d^-1, succeeded the diatoms dominating during the earlier phase of the spring bloom. The concentration of fucoxanthin was highest during the first half of May, while pigment fingerprints of high-performance liquid chromatograms of suspended matter sampled during the second half of May were dominated by 19-hexanoyloxyfucoxanthin, the main carotenoid of C. aureus (0.8x10^-9 mg cell^-1). This colonial Prymnesiophycean was described for the first time less than 10 years ago and has nerver been reported to be present in the North Sea. After 16 May the C. aureus population rapidly lost its growth potential, but the peak of the bloom in terms of cell number was found several days later (up to 9x10⁶ cells per dm³ on 19 May). The population then started to decline; senescence was associated with decreasing pigment contents of cells. The low growth rate of copepods registered during the second half of May was probably related to the poor quality of C. aureus as copepod food: the concentration of a phaeophorbide a typically found in copepod fecal pellets was highest during the diatom phase of the spring bloom preceding the C. aureus bloom.