Cruises In August Research Articles

A sensitive flow-batch system for on board determination of ultra-trace ammonium in seawater: Method development and shipboard application

Combining fluorescence detection with flow analysis and solid phase extraction (SPE), a highly sensitive and automatic flow system for measurement of ultra-trace ammonium in open ocean water was established. Determination was based on fluorescence detection of a typical product of o-phthaldialdehyde and ammonium. In this study, the fluorescence reaction product could be efficiently extracted onto an SPE cartridge (HLB, hydrophilic–lipophilic balance). The extracted fluorescence compounds were rapidly eluted with ethanol and directed into a flow cell for fluorescence detection. Compared with the common used fluorescence method, the proposed one offered the benefits of improved sensitivity, reduced reagent consumption, negligible salinity effect and lower cost. Experimental parameters were optimized using a univariate experimental design. Calibration curves, ranging from 1.67 to 300nM, were obtained with different reaction times. The recoveries were between 89.5 and 96.5%, and the detection limits in land-based and shipboard laboratories were 0.7 and 1.2nM, respectively. The relative standard deviation was 3.5% (n=5) for an aged seawater sample spiked with 20nM ammonium. Compared with the analytical results obtained using the indophenol blue method coupled to a long-path liquid waveguide capillary cell, the proposed method showed good agreement. The method had been applied on board during a South China Sea cruise in August 2012. A vertical profile of ammonium in the South East Asia Time-Series (SEATS, 18° N, 116° E) station was produced. The distribution of ammonium in the surface seawater of the Qiongdong upwelling in South China Sea is also presented.

Surpact: A SMOS Surface Wave Rider for Air-Sea Interaction

A new small wave rider called Surpact was developed for air-sea investigations. It was designed to attach to a drifter or a mooring and to float upon the surface waves in order to measure sea state and atmospheric sea level pressure as well as temperature and salinity at a small fixed depth from the surface. Wind speed is derived from Surpact sea state measurements, and the data are calibrated with co-located Special Sensor Microwave Imager Sounder (SSMIS) wind retrievals during a four-month deployment in the North Atlantic subtropics. Individual 15-minute wind estimates present a root mean square difference on the order of 15% with the SSMIS wind retrievals for wind speeds less than 12 m s-1. The wind retrievals might lag the actual wind changes for moderate to strong winds by an hour. This article discusses the accuracy of these wind retrievals based on in situ data collected during the Strasse cruise in August and September 2012. Temperature and salinity data are also examined. The authors find, under some sunny conditions, radiative warming of the temperature probe reduces the accuracy of some of the daytime temperature data and also affects corresponding salinity estimates. Nonetheless, small realistic daily cycles of near-surface salinity (0.01 psu amplitude) were observed. Also, examples of wind time series collected during salinity drops caused by rainfall during late 2012 in the North Atlantic subtropics indicate no intensification of wind during these rain events.

Discovery of a new hydrothermal vent based on an underwater, high-resolution geophysical survey

A new hydrothermal vent site in the Southern Mariana Trough has been discovered using acoustic and magnetic surveys conducted by the Japan Agency for Marine-Earth Science and Technology's (JAMSTEC) autonomous underwater vehicle (AUV), Urashima. The high-resolution magnetic survey, part of a near-bottom geophysical mapping around a previously known hydrothermal vent site, the Pika site, during the YK09-08 cruise in June–July 2009, found that a clear magnetization low extends ∼500m north from the Pika site. Acoustic signals, suggesting hydrothermal plumes, and 10m-scale chimney-like topographic highs were detected within this low magnetization zone by a 120kHz side-scan sonar and a 400kHz multibeam echo sounder. In order to confirm the seafloor sources of the geophysical signals, seafloor observations were carried out using the deep-sea manned submersible Shinkai 6500 during the YK 10-10 cruise in August 2010. This discovered a new hydrothermal vent site (12°55.30′N, 143°38.89′E; at a depth of 2922m), which we have named the Urashima site. This hydrothermal vent site covers an area of approximately 300m×300m and consists of black and clear smoker chimneys, brownish-colored shimmering chimneys, and inactive chimneys. All of the fluids sampled from the Urashima and Pika sites have chlorinity greater than local ambient seawater, suggesting subseafloor phase separation or leaching from rocks in the hydrothermal reaction zone. End-member compositions of the Urashima and Pika fluids suggest that fluids from two different sources feed the two sites, even though they are located on the same knoll and separated by only ∼500m. We demonstrate that investigations on hydrothermal vent sites located in close proximity to one another can provide important insights into subseafloor hydrothermal fluid flow, and also that, while such hydrothermal sites are difficult to detect by conventional plume survey methods, high-resolution underwater geophysical surveys provide an effective means.

Sediment quality assessment using Gmelinoides fasciatus and Monoporeia affinis (Amphipoda, Gammaridea) in the northeastern Baltic Sea

Crustaceans in the order Amphipoda are sensitive organisms for the assessment of sediment quality. In this work we performed 10-day toxicity tests on muddy sediments collected from a total of 29 sites in the Gulf of Finland, the Gulf of Riga and the Gulf of Bothnia (northeastern Baltic Sea) using Baltic Sea species such as the native amphipod Monoporeia affinis (Bousfield, 1989) and the invasive amphipod Gmelinoides fasciatus (Stebbing, 1899), and also compared these results with those of bioassays carried out using the standard test species, laboratory-cultivated amphipod Hyalella azteca (Saussure, 1858). The sediment samples (three cm of the upper layer) were collected by a GEMAX Dual Corer during the R/V “Aranda” cruises in August and September of 2009 and 2010. Toxicity of sediments in bioassays with M. affinis and G. fasciatus gave varied results depending on the amphipod species used. The lowest quality of sediments determined using M. affinis was recorded at sites located in the offshore and deepwater areas (60-100 m depths) of the Gulf of Finland characterized by hypoxic/anoxic conditions. Toxicity testing applying G. fasciatus showed that sediments at >50% of the study sites in the Gulf of Finland and in the Gulf of Riga can be assessed as highly contaminated. Males of G. fasciatus were significantly more sensitive to potential contamination in sediments than females. The lower survival of males under contaminant stress may result in a skewed sex ratio in natural populations and in a decline of reproduction success. The survival rate of G. fasciatus in the toxicity tests correlated positively with the Shannon diversity index (calculated for macrozoobenthos at the study sites), weight losses on ignition (%) in sediments, and it also showed a negative relation with the bottom water oxygen content (mg/l). The results suggest that G. fasciatus is the more sensitive species of the three amphipods tested and can be used as a indicator of sediment quality in the Baltic Sea and other water bodies.

Distribution characteristics of transparent exopolymer particles in the Pearl River estuary, China

Distribution of Transparent Exopolymer Particles (TEP) in the Pearl River estuary, China, was investigated during two cruises in August 2009 and January 2010. TEPcolor concentrations were 521.5–1727.4 μg Xeq.L−1 (μg Gum Xanthan equivalent liter−1) in August 2009 and 88.7–1586.9 μg Xeq.L−1 in January 2010, respectively. The size of TEP generally increased in the seaward along the longitudinal section with the dominant size of 2–40 μm during the cruises. Experimental work suggested that both concentration and size of TEP increased with Ca2+ concentration (from 0.8 mmol L−1 to 10 mmol L−1). In the field study, Ca2+ concentration had a positive correlation with TEPcolor concentration in the surface layer with salinity <16. Decrease of TEP concentration seaward from intermediary salinity was partly due to dilution of seawater as well as enhanced aggregation and sedimentation of TEP via increasing divalent cation concentration. TEP concentration and turbidity maximum coexisted at the tip of salt wedge in the bottom layer during the wet season, and positive correlation between TEP and turbidity was observed in the winter. Relationships between TEP and turbidity suggested the important contribution of TEP aggregation to flocculation and sedimentation of particles in estuaries. Different pattern of TEP during two cruises can be attributed to physical process (i.e., mixing type) in estuaries. These findings indicated that formation and distribution of TEP were largely influenced by interaction between physical and biogeochemical processes in the Pearl River estuary. A conceptual model for TEP formation and distribution in the Pearl River estuary was developed.

High‐resolution estimates of net community production and air‐sea CO2 flux in the northeast Pacific

Rates of net community production (NCP) and air‐sea CO2 flux in the Northeast Pacific subarctic, transition zone and subtropical regions (22°N–50°N, 145°W–152°W) were determined on a cruise in August–September 2008 by continuous measurement of surface values of the ratio of dissolved oxygen to argon (O2/Ar) and the partial pressure of CO2 (pCO2). These estimates were compared with simultaneous measurements of sea surface temperature (SST), chlorophyll‐a (chl‐a), flow cytometry, and discrete surface nutrient concentrations. NCP and CO2 influx were greatest in the subarctic (45°N–50°N, 25.8 ± 4.6 and 4.1 ± 0.9 mmol C m−2 d−1) and northern transition zone (40°N–45°N, 17.1 ± 4.4 and 2.1 ± 0.5 mmol C m−2 d−1), with mean NCP ∼6–8× greater than mean CO2 invasion (error estimates reflect 1 σ confidence intervals). Contrastingly, the southern transition zone (32°N–40°N) and subtropics (22°N–32°N) had lower mean NCP (5.4 ± 1.8 and 8.1 ± 2.1 mmol C m−2 d−1, respectively) and mean CO2 efflux (3.0 ± 0.5 and 0.1 ± 0.0 mmol C m−2 d−1, respectively). In the subarctic and transition zone, NCP was highly correlated with surface chl‐a and CO2 influx, indicating strong coupling between the biological pump and CO2 uptake. Meridional trends in our NCP estimates in the transition zone and subtropics were similar to those for integrated summertime NCP along the cruise track determined using an upper ocean climatological carbon budget.

Large scale northward expansion of warm water species Skeletonema tropicum (Bacillariophyceae) in China seas

S keletonema tropicum is regarded as a species with an affinity to warm waters and it has never been reported in seas where temperatures drop below 11°C in winter. Previous studies in China reported that S. tropicum was restricted to subtropical and warm temperate seas (East and South China Seas), but the species was recently found during August cruises of 2009 and 2010 in Jiaozhou Bay, Yellow Sea, located several hundred kilometers to the north. Here, winter water temperatures often drop below 5°C. Identification of S. tropicum was confirmed under light and scanning electronic microscopes and maximum cell abundance in Jiaozhou Bay was estimated as 1.73×104 cell/L. This record of S. tropicum in Jiaozhou Bay represents a significant northward expansion in the geographic range of the species. Ship ballast water was identified as a possible carrier of S. tropicum from southern places along Chinese coastline, and in addition, thermal pollution from local power stations and seawater desalination plants may provide suitable conditions for species over-wintering.

Absorption and fluorescence of dissolved organic matter in submarine hydrothermal vents off NE Taiwan

The role of hydrothermal vents as either a source or a sink for chromophoric and fluorescent dissolved organic matter (CDOM and FDOM) in the oceans is unknown, since DOM absorption and fluorescence have not been reported for submarine hydrothermal vents. Water samples were collected from two shallow submarine hydrothermal vents off NE Taiwan, the white vent and the yellow vent, during two cruises in August, 2010. Absorption and excitation-emission-matrix fluorescence spectroscopy were used to characterize the optical properties of DOM from such extremely special environments. The absorption coefficients at wavelength 300 nm ( a 300) were much higher at the white vent mouth and 1 m below it (2.52 ± 0.88 m -1) than in the background (0.34 ± 0.12 m -1). This indicated that the white vent was a source of CDOM for seawater. Three fluorescent components were identified using parallel factor analysis: humic-like C1, tyrosine-like C3, and C2 as a combination of tryptophan-like and marine humic-like components. Both C1 and C3 (but not C2) had their highest fluorescence intensity at the white vent mouth and 1 m below it, suggesting the role of the vent as a source for both humic-like and tyrosine-like DOM. Samples from the yellow vent mouth also had a higher a 300 than the ambient seawater in our first cruise, but had fluorescence intensities of C(1–3) similar to the ambient seawater. Overall, the low humification index (HIX: 1.40 ± 0.30) and the high autochthonous index (BIX: 1.27 ± 0.63) indicated that the DOM likely had low humic contents and was mainly autochthonous of biological or bacterial origin in the study area. A biplot of HIX and BIX showed that DOM from the hydrothermal vents had a characteristic similar to terrestrial cave and spring waters, but was distinct from isolated humics.

Seasonal variability in air‐sea fluxes of CO2 in a river‐influenced coastal margin

Recent studies in the northern Gulf of Mexico and elsewhere have demonstrated that enhanced biological production in large river plumes may contribute to a net surface influx of atmospheric CO2. However, large rivers also deliver significant amounts of terrestrial carbon into continental margin waters; hence, the potential for large and variable signals in carbon flux exist in these regions. Here, we used a combination of satellite and ship‐based observations to examine variability in surface pCO2 and air‐sea flux of carbon dioxide in relation to variations in river discharge and seasonal environmental conditions. Underway surface pCO2 showed large seasonal differences based on observations acquired during cruises in August 2004, October 2005, and April 2006. Strong cross‐shelf gradients in pCO2 were observed during August 2004 and April 2006, influenced by river outflow. Uniformly high values observed during October 2005 likely reflected the disturbed nature of the system after two major storm events (hurricanes Katrina and Rita). Satellite‐derived assessments of pCO2 were used in conjunction with estimates of wind fields to produce regional maps of surface water pCO2 and air‐sea fluxes. The region was a net sink for atmospheric CO2 in August 2004 (−0.96 to −1.2 mmol C m−2 d−1) and net source during October 2005 and April 2006 (1.0 to 5.4 mmol C m−2 d−1). Uncertainties in flux estimates, particularly for low salinity waters in April 2006, highlighted the need for more extensive in situ observations. Our results illustrate the utility of satellite approaches for providing regional assessments of coastal carbon budgets.

Summer mesozooplankton distribution near Novaya Zemlya (eastern Barents Sea)

Regional variations in mesozooplankton composition, abundance and biomass were studied during a cruise in August 2006 near Novaya Zemlya Archipelago (eastern Barents Sea) using Juday net hauls from the bottom (or 100 m depth) to the surface. A comparison with multiannual literature values revealed that the mean temperature and salinity in the south and centre of the study area were similar to typical values, while temperature in the north was significantly higher. A total of 36 species and higher taxa were identified. Mesozooplankton abundance and biomass varied from 47 to 851 ind m−3 and from 5 to 74 mg dry weight m−3, respectively. Copepods dominated the mesozooplankton community, reaching 73–98% and 61–97% of the total abundance and biomass. Calanus finmarchicus and Oithona similis were the most abundant species at all stations. The biodiversities (Shannon indices) of the mesozooplankton community varied between stations from 1.10 to 2.46 (estimated from species abundances) and from 0.19 to 1.92 (estimated from species biomasses), averaging 1.93 ± 0.127 and 1.34 ± 0.151, respectively. Three groups at the 48% level of dissimilarity of species abundance were delineated by cluster analyses. The clusters differed significantly with respect to temperature and salinity. The total mesozooplankton abundance and biomass as well as quantitative parameters of most common taxa scaled negatively with temperature.

Thin phytoplankton layer formation at eddies, filaments, and fronts in a coastal upwelling zone

Abstract On two cruises in August and September 2003 (hereafter cruises 2 and 3) during wind relaxations and transitions to upwelling conditions, thin layers of phytoplankton were observed in or a few meters below the stratified transition layer at the mixed layer base and in regions of sheared flow on the flanks of eddies, filaments, and fronts near Monterey Bay, California. On an earlier cruise in August (cruise 1), no thin layers were found after a prolonged wind relaxation. Chlorophyll concentrations and shear were both an order of magnitude less than on cruises 2 and 3. Our vertical profiles were made using a fluorometer mounted on a conductivity–temperature–depth package, which was lowered from the ship as slowly as 0.25 m s - 1 every 10 km on five ∼ 80 -km cross-shore transects. Remotely sensed sea-surface temperature, chlorophyll, and currents are required to understand the temporal and spatial evolution of the circulation and to interpret the quasi-synoptic in situ data. Decorrelation scales are ∼ 20 km from lagged temperature and salinity covariances. Objectively mapped sections of the in situ data indicate the waters containing thin layers were recently upwelled at either the Point Sur or Point Ano Nuevo upwelling centers. Spatially limited distributions of phytoplankton at the coastal upwelling centers ( ∼ 40 km alongshore, 20 km cross-shore, and 30 m thick) were transformed into thin layers by current shear and isolated from wind-driven vertical mixing by the stratification maximum of the transition layer. Vertically sheared horizontal currents on the flanks of the eddies, filaments, and fronts horizontally stretched and vertically thinned phytoplankton distributions. These thin, elongated structures were then observed as thin layers of phytoplankton in vertical fluorescence profiles at four stations on cruise 2 and eight stations on cruise 3. Light winds during relaxations did not mix away these thin layers. On cruise 2, thin layers were found at eddies at the inshore and offshore ends of a 100-km-long filament, while broader subsurface chlorophyll maxima were found along the filament. This result suggests that higher-resolution sampling along and across a filament may find thin layers forming and dissipating along its length. On cruise 3, thin layers were found at three adjacent stations across an upwelling front and may have extended continuously for > 20 km , but neither species composition nor bio-optical data are available to confirm this conjecture. The thin layers were 1–5 m thick in the vertical at full width half maximum and had peak fluorescence values from 7 – 30 mg m - 3 . (Bottle chlorophyll samples showed fluorometer chlorophyll readings may have been 1.3 – 1.5 × too large, but the scatter in this relation was considerable especially at the larger fluorescence values detected in thin layers.) While sheared currents thinned an initially thick subsurface chlorophyll maximum into thin layers, the peak values in these thin layers exceeded concentrations in the upwelled source waters and were unexplained by our data.

On being a pathologist: how does one plan a career, or does one?

My decision to go to medical school, made in 1949 when I was 12 years old, resulted from an interest in photography and a series of illnesses with numerous x-rays. Thus, I decided to become a radiologist. Getting into medical school was not an easy task when only 10% of the medical school classes had to be women according to the National Health Act of 1948. Since I was at a small boarding school, my ambition meant my father forcing the school to recruit a senior master from nearby Tonbridge boys' school to teach me physics and chemistry. I also benefited from vacation chemistry tutoring at King's College, Newcastle upon Tyne, UK. By the time I was interviewed in 1955 at Durham University Medical School in Newcastle upon Tyne, now Newcastle University Medical School, I had forgotten my real reason for becoming a doctor, but I was accepted dependent on passing 4 “A-levels.” On a Mediterranean cruise in August, I learned that I had passed the 4 subjects and would enter the “second year” of medical school that October. In those days there were ostensibly no grades, but later I found out that I had only passed my chemistry by 1 mark (pass was 40/100) and physics by 5. Botany and zoology were easy passes. The next hurdle was “Second M.B.” after 15 months of anatomy, physiology, and biochemistry. Approximately 10% of the class would be eliminated by this examination. Pathology, Public Health, Pharmacology, and Introduction to Clinical Medicine began during our “third year.” Pathology

PCO2 and carbon fluxes across sea-air interface in the Changjiang Estuary and Hangzhou Bay

Partial pressure of CO(2) (pCO(2)) was investigated in the Changjiang (Yangtze River) Estuary, Hangzhou Bay and their adjacent areas during a cruise in August 2004, China. The data show that pCO(2) in surface waters of the studied area was higher than that in the atmosphere with only exception of a patch east of Zhoushan Archipelago. The pCO(2) varied from 168 to 2 264 mu atm, which fell in the low range compared with those of other estuaries in the world. The calculated sea-air CO(2) fluxes decreased offshore and varied from -10.0 to 88.1 mmol m(-2) d(-1) in average of 24.4 +/- 16.5 mmol m(-2) d(-1). Although the area studied was estimated only 2 x 10(4) km(2), it emitted (5.9 +/- 4.0) x 10(3) tons of carbon to the atmosphere every day. The estuaries and their plumes must be further studied for better understanding the role of coastal seas playing in the global oceanic carbon cycle.

Hydrography and flow in the Lucky Strike segment of the Mid-Atlantic Ridge

The Lucky Strike segment between 37 and 38N on the Mid-Atlantic Ridge is the focus of the international MoMAR program to monitor seafloor-spreading processes. During the GRAVILUCK cruise in August 2006, hydrographic, velocity and light-scattering data were collected in the rift valley at Lucky Strike in order to investigate the regional dynamics and to provide background information for the monitoring effort. The survey observations reveal a remarkably simple dynamical setting dominated by persistent northward flow transporting ≈0.2 Sv of water along the rift valley. Approximately half of this transport must upwell within a deep basin that occupies the northern half of the segment. In the comparatively shallow segment center, the along-valley transport takes place in two parallel, hydraulically controlled overflows on both sides of an active volcano that rises from the rift-valley floor. Within the better sampled of these overflows instantaneous velocities recorded during the survey were northward more than 95% of the time and occasionally exceeded 20 cm s-1. Similar to other laterally confined overflows in the deep ocean, the cross-sill density gradients are characterized by a lower layer with streamwise decreasing densities and an upper layer where the densities increase along the path of the flow. This vertical density-gradient dipole is the signature of the buoyancy flux associated with high levels of diapycnal mixing near the sill. Overall, the hydrography and dynamics in the rift valley of the Lucky Strike segment are highly reminiscent of many ridge-flank canyons in the western South Atlantic, where mean along-axial advection of density is balanced by vigorous diapycnal mixing. There is circumstantial evidence from historic hydrographic data suggesting that northward flow below ≈1800m in the rift valley in the MoMAR region is persistent on time scales of years to decades and that it extends more than 200 km to the south. During GRAVILUCK the northward flow at Lucky Strike extended well above 1600m, where two previous one year-long current meters had recorded southward mean flows near the Lucky Strike hydrothermal vent field. While interannual variability can potentially account for this difference, the data also allow for the possibility of a cyclonic re-circulation around an isolated topographic peak east of the vent field, resulting in the southward mean flows observed there. In addition to the light-scattering anomalies associated with plumes rising from the Lucky Strike vent field near the segment center, the GRAVILUCK data also show clear evidence for a separate hydrothermal particle plume emanating from a not-yet-discovered vent field in the southern half of the segment, probably near 2000m.

Harmonic analysis of suspended particulate matter in the Menai Strait (UK)

An application of harmonic analysis is presented to estimate M2 and M4 tidal constituents of various suspended particulate matter (SPM) fractions in a marine ecosystem. The data were collected on two cruises in August and September 2004. In both sets of data there appeared to be clearly identifiable advection (i.e. semidiurnal increases in concentrations), resuspension (i.e. quarterdiurnal increases in concentrations), and flocculation (e.g. increases in median diameter at slack waters) signals. In most cases, the simulations on M2 and M4 components (estimated using harmonic analysis) explained a considerable proportion of variance (typical r 2 is 0.4–0.65). However, some of the variables examined (e.g. median diameter in deeper layers) could not be modelled satisfactorily using the method chosen. In August, the amplitude of the M4 component was invariably lower than of the M2 component, thus indicating that advection signal dominated the overall dynamics observed. In September, however, this pattern was reversed for small and medium-sized particle diameters, thus indicating that resuspension for this fractions was prevalent. Another remarkable difference between the two data sets is the considerable difference between the estimated advection phases, which were, in general (and variable depending on the specific fraction), approximately 8 and 5 h after LW in August and September, respectively. These differences might have been partly related to the differences in the exact sampling locations, seasonal changes between the two cruises, local processes in the Menai Strait, and/or preceding meteorological conditions. The results are discussed in terms of their importance for the Menai Strait biota.

Suspended particulate matter (SPM) in the North Sea-Baltic Sea transition: Distributions, inventories, and the autumn 2002 inflows

Geografisk Tidsskrift, Danish Journal of Geography 108(2):37–47, 2008 The present study describes the spatial distribution of suspended particulate matter (SPM) in the North Sea—Baltic Sea transition in autumn 2002 based on cruises in August, September, and October. The cruises comprised CTD and optical backscatter measurements supplemented with water sampling and determination of SPM concentrations. Each cruise covered 4 days whereby a close to synoptic SPM distribution was obtained in each of the 3 months. Supplementary cruises were carried out in February 2002 and November 2004. Results showed that surface water SPM concentrations varied around 2–4 g m−3 in the transition with no temporal variation during the autumn. In comparison, bottom water SPM concentrations varied around 4–6 g m−3 except at the Skagerrak/Kattegat boundary where concentrations reached up to 20–22 g m−3. Total SPM inventory, which comprises the Kattegat, the Belt Sea, and the western Baltic Sea, is in the range 2.06* 106- 3.53* 106 tons SPM of which 14 is organic material. Data from the Arkona Basin in the southwest Baltic Sea showed no indications of an enhanced SPM transport into the basin during the autumn 2002 inflows. It was estimated that about 0.18–0.36* 106 tons SPM were transported towards the Baltic Sea with the autumn 2002 inflows. Inflows to the Baltic Sea from the Kattegat are infrequent but it was estimated that a mass between 0.77–1.16* 106 tons of SPM was transported into the Baltic Sea at an average inflow.

Invasive ctenophore Mnemiopsis leidyi in Limfjorden (Denmark) in late summer 2007 - assessment of abundance and predation effects

Abstract The invasive ctenophore, Mnemiopsis leidyi , was recently observed for the first time in Danish waters where it was widely distributed during the summer of 2007. In certain areas, including Limfjorden, it exhibited mass occurrence. In this study, we assess the abundance of M. leidyi in Limfjorden in the late summer of 2007 and give a preliminary evaluation of the predation effects of this ctenophore. On two cruises in August and September, M. leidyi was found in every net sample from 9 locations in Limfjorden. The population densities were high, up to more than 800 individuals m -3 in the innermost part, but body lengths were small (5 to 15 mm). The bio-volumes were very high (100 and 300 ml m -3 ) in the central parts of Limfjorden and are even greater than those from the Black Sea, where the greatest mean bio-volume was about 184 ml m -3 in the autumn of 1989 when the zooplankton and fish stocks collapsed. The possible ecological consequences of the mass occurrence of this ctenophore are discussed. Key words: Ctenophora, comb jelly, alien species, jellyfish, zooplankton,

Non-conservative behaviour of molybdenum in coastal waters: Coupling geochemical, biological, and sedimentological processes

Non-conservative behaviour of dissolved Mo was observed during specific time periods in the water column of the Wadden Sea of NW Germany. In July 2005 dissolved Mo declined within 36 h from a level only slightly below seawater (82 nM) to a minimum value of 30 nM, whereas in August 2002 dissolved Mo revealed a tidal cyclicity with maximum values up to 158 nM at low tide. In contrast, cruises in August 2003 and 2004 displayed an almost conservative behaviour of Mo. The decrease in dissolved Mo during July 2005 and elevated values in August 2002 were accompanied by Mo enrichments on aggregates in the water column of the Wadden Sea. Along with Mo, dissolved Mn showed unusual concentration patterns in July 2005, with values distinctly below the common summer level (by a factor of five). A direct relation between the loss of Mo and scavenging by freshly formed MnO x phases could not be inferred from our data because both metals revealed inverse patterns. Parallel to decreasing dissolved Mo concentrations dissolved Mn showed an increasing trend while particulate Mn decreased. Such finding is compatible with the formation of oxygen-depleted zones in aggregates, which provide suitable conditions for the rapid fixation of Mo and parallel release of Mn by chemically and/or microbially mediated processes. Our assumption is supported by biological (e.g. number of aggregate-associated bacteria) and sedimentological (e.g. aggregate abundance and size) parameters. The production of organic components (e.g. TEP) during breakdown of an algae bloom in July 2005 led to the formation of larger Mo-enriched aggregates, thus depleting the water column in dissolved Mo. After deposition on and incorporation into sandy tidal flats these aggregates are rapidly decomposed by microbial activity. Pore water profiles document that during microbial decomposition of these aggregates, substantial amounts of Mo are released and may replenish and even enrich Mo in the open water column. We postulate a conceptual model for the observed non-conservative behaviour of Mo in coastal waters, which is based on the tight coupling of geochemical, biological, and sedimentological processes.

Diversity, structure and interactions of encrusting lithophyllic macrofaunal assemblages from Belgica Bank, East Greenland

Drop stones with lithophyllic macrofauna from Belgica Bank, Greenland Sea (79–81°N and 5–17°W) were collected during the Polarstern cruise in August 2000. The investigation focussed on species richness, diversity, abundance, and interactions of organisms colonizing rocks. On 101 stones collected by 10 dredges from nine sites, 113 taxa (58 genera, 38 families, 12 orders and 8 phyla) were recognized. Among the most abundant groups of organisms were foraminiferans, bryozoans and polychaetes, while the least abundant were anthozoans and ascidians. Abundance ranged from 1239 to 11,383 individuals m−2 of rock surface area. Bryozoans were the most species-rich group, while anthozoans and ascidians were represented by the least number of species. Colonization occurred at various topographical levels and was classified into two categories. Stones were classified as primary space and were colonized by erect membranous, erect flexible, erect rigid, and flat encrusting organisms. The second level of colonization by epibionts occurred on erect forms of organisms (e.g. erect bryozoans) and was classified as a secondary space. Species composition and abundance between faunal assemblages of primary and secondary space differed greatly. Colonization occurred only on the top of stones and was considered a special adaptation to avoid burial by sedimentation and to enhance food supply. Only 3% of recruits were involved in any competitive interactions. Competition was considered to be of minor importance in structuring lithophyllic assemblages.

Presence and regulation of alkaline phosphatase activity in eukaryotic phytoplankton from the coastal ocean: Implications for dissolved organic phosphorus remineralization

The biologically important constituents of the dissolved organic phosphorus (DOP) pool, their bioavailability, and their cycling in coastal systems are still poorly understood. Here we use the enzyme alkaline phosphatase as a metric of DOP bioavailability and track the activity of this enzyme in a coastal system. We observed alkaline phosphatase activity (APA) in the >0.2-μm size fraction of all surface samples tested during an Oregon coast cruise in August 2001. Although there was not a significant trend between APA and phosphate concentration in the data set as a whole, chlorophyll a-normalized APA was elevated at the station with the lowest dissolved inorganic phosphate (DIP) concentration. Activity was also elevated in nutrient-addition experiments in which nitrate amendments were Used to force community drawdown of DIP. These data are consistent with phosphate regulation of APA. A cell-specific APA assay revealed that the percentage of diatoms with APA mimicked the trend in the hydrolytic rate, but such a trend was not observed for the dinoflagellates. Further, the percentage of dinoflagellate cells with APA was routinely higher than the percentage of diatom cells with activity. In nutrient-addition experiments designed to evaluate the regulation of APA, diatom taxa expressed APA less frequently than dinoflagellates, but they displayed a tighter regulation of the activity by DIP than dinoflagellates. The variability observed in the presence and regulation of APA in these eukaryotic phytoplankton indicates that DOP bioavailability is a potential driver of phytoplankton nutrition and species composition in the coastal ocean.