Mesozooplankton structure in the northern White Sea in July 2008

The mesozooplankton of the northern White Sea and Mezen Bay was investigated at nine stations in July 2008 using a Juday net (168 μm mesh size). A total of 39 taxa (species and higher taxa) were found in the samples. Average abundance, biomass, and diversity (Shannon index) were (±SE) 120,793 ± 70,439 ind. m⁻², 443 ± 216 mg DW m⁻², and 1.41 ± 0.11, respectively. Copepods were most numerous. Overall, herbivores dominated primarily Cirripedia nauplii and Pseudocalanus minutus. Significant correlations were observed among mean temperature, salinity, and mean mesozooplankton abundance and biomass. Our data suggest that salinity and intensive local currents could be the main factors responsible for the distribution of mesozooplankton in the northern White Sea. The average mesozooplankton biomass was higher than in previous studies, indicating a possible climatic impact on the mesozooplankton community.     

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.     

Distribution of microphytobenthic biomass in Martel Inlet,King George Island (Antarctica)

The spatial and temporal variation of microphytobenthic biomass in the nearshore zone of Martel Inlet (King George Island, Antarctica) was estimated at several sites and depths (10–60 m), during three summer periods (1996/1997, 1997/1998, 2004/2005). The mean values were inversely related to the bathymetric gradient: higher ones at 10–20 m depth (136.2 ± 112.5 mg Chl a m⁻², 261.7 ± 455.9 mg Phaeo m⁻²), intermediate at 20–30 m (55.6 ± 39.5 mg Chl a m⁻², 108.8 ± 73.0 mg Phaeo m⁻²) and lower ones at 40–60 m (22.7 ± 23.7 mg Chl a m⁻², 58.3 ± 38.9 mg Phaeo m⁻²). There was also a reduction in the Chl a/Phaeo ratio with depth, from 3.2 ± 3.2 (10–20 m) to 0.7 ± 1.0 (40–60 m), showing a higher contribution of senescent phytoplankton and/or macroalgae debris at the deeper sites and the limited light flux reaching the bottom. Horizontal differences found in the biomass throughout the inlet could not be clearly related to hydrodynamics or proximity to glaciers, but with sediment characteristics. An inter-summer variation was observed: the first summer presented the highest microphytobenthic biomass apparently related to more hydrodynamic conditions, which causes the deposition of allochthonous material.     

Mesozooplankton community in the Bay of Bengal (India): spatial variability during the summer monsoon

This study addresses the spatial variability in mesozooplankton biomass and composition in the Central and Western Bay of Bengal (India) during the summer monsoon season of 2001. Perennially warmer sea surface temperatures (>28°C), stratified top layer (sea surface salinity, 28–33 psu), high turbidity, and low nutrient concentrations due to weak/null upwelling and light limitation make the Bay of Bengal a region of low primary productivity. Despite this, mesozooplankton biomass values, i.e. 2.9–104 mg C m⁻³ in the Central Bay and 1.3–31 mg C m⁻³ in the Western Bay, observed in the mixed layer (2–51 m) during the summer monsoon were in the same range as reported from the more productive Arabian Sea. Mesozooplankton biomass was five times and density 18 times greater at stations with signatures of cold-core eddies, causing a higher spatial heterogeneity in zooplankton distribution. Among the 27 taxonomic groups recorded during the season, Copepoda was the most abundant group in all samples followed by Chaetognatha. The dominant order of Copepoda, Calanoida, was represented by 132 species in a total of 163 species recorded. Oncaea venusta was the key copepod species in the Bay. In the Central Bay, the predominant copepod species were carnivorous/omnivorous vis-a-vis mostly herbivores in the Western Bay. Pleuromamma indica increased to its maximum abundance at 18°N in the Central Bay, coinciding with the lowest dissolved oxygen concentrations. The Central Bay had higher mesozooplankton biomass, copepod species richness and diversity than in the Western Bay. Although zooplankton biomass and densities were greater at the eddy stations, correlation between zooplankton and chl a was not statistically significant. It appears that the grazer mesozooplankton rapidly utilize the enhanced phytoplankton production in cold-core eddies.     

Distribution and factors influencing on structure of reef fish communities in Nha Trang Bay Marine Protected Area, South-Central Vietnam

Visual censuses of coral reef fishes in Nha Trang Bay Marine Protected Area (MPA) were conducted during September–October 2005. Nha Trang Bay MPA is relatively rich in reef fishes compared to other areas in Vietnam and the Pacific Ocean outside the ‘Coral Triangle,’ consistent with its biogeographic location in the western South China Sea. A total of 266 species of 40 families of coral reef fishes formed five distinct assemblages. Spatial variations in distribution and structure of the assemblages were associated with eight significant biological and physical variables which were cover of living hard corals, encrusting corals, branching corals, Acropora, Millepora, Montipora, depth and distance from the coast of the mainland. The six factors in front are likely related to provision of shelter and nutrition, while the distance factor is likely to represent a gradient in disturbance and impacts from various mainland sources including sedimentation and pollution discharge from nearby rivers. Local species richness ranged from 35 to 70 species 500 m⁻² (mean: 51 ± 2 SE) for reef flat stations and from 23 to 68 species 500 m⁻² (mean: 48 ± 4 SE) for reef slope stations. Total species richness at each site averaged 76 species (±4 SE), ranging from 56 to 110 species, dominated by wrasses, damselfishes, butterflyfishes, parrotfishes, surgeonfishes, groupers and goatfishes. Density of total fishes at each station ranged from 348 to 1,444 individuals 500 m⁻² (mean: 722 ± 302 SE) for the reef flat stations and from 252 to 929 individuals 500 m⁻² (mean: 536 ± 215.7 SE) for the reef slope stations. Overall mean density at each site averaged 628.9 (±238.4 SE) individuals 500 m⁻². The highly protected sites supported higher mean density of fishes per site (ranged: 904.5–1,213 individuals 500 m⁻² for Hon Mun and 1,167.5 individuals 500 m⁻² for Hon Cau) compared to other sites (<800 individuals 500 m⁻²). Of the families included in the census, densities were dominated throughout the MPA by damselfishes and wrasses. Many target species, particularly groupers, snappers and emperors, were rare or absent and the low abundance of big fishes was consistent with over-harvesting. Similarly a low density of butterfly fishes and angelfishes is likely related to the supply for marine aquaria in Vietnam and overseas. This study provides an important baseline against which the success of present and future MPA management initiatives may be assessed.     

Phytoplankton and sea ice algal biomass and physiology during the transition between winter and spring (McMurdo Sound, Antarctica)

The phytoplankton and sea ice algal communities at the end of winter in McMurdo Sound were dominated by Fragilariopsis sublineata, with Thalassiosira antarctica, Melosira adele, Pinnularia quadreata, Entomoneis kjellmannii and heterotrophic dinoflagellates also present. Sea ice algal biomass at the end of winter was very low, only 0.050 ± 0.019 mg chla m⁻² in 2007 and 0.234 ± 0.036 mg chla m⁻² in 2008, but this increased to 0.377 ± 0.078 mg chla m⁻² by early October in 2007 and to 1.07 ± 0.192 by late September in 2008. Under ice phytoplankton biomass remained consistently below 0.1 μg chla l⁻¹ throughout the measuring period in both years. The photosynthetic parameters Fv/Fm, rETRmax and α document microalgal communities that are mostly healthy and well adapted to their low light under ice environment. Our results also suggest that species such as Fragilariopsis sublineata are well adapted to deal with low winter light levels but are unlikely to survive an increase in irradiance, whereas other taxa, such as Thalassiosira antarctica, will do better in a higher light environment.     

Structure and grazing impact of the mesozooplankton community during late summer 1994 near South Georgia, Antarctica

Mesozooplankton abundance, community structure and grazing impact were determined during late austral summer (February/March) 1994 at eight oceanic stations near South Georgia using samples collected with a Bongo and WP-2 nets in the upper 200-m and 100-m layer, respectively. The zooplankton abundance was generally dominated by copepodite stages C3–C5 of six copepod species: Rhincalanus gigas, Calanus simillimus, Calanoides acutus, Metridia spp., Clausocalanus laticeps and Ctenocalanus vanus. Most copepods had large lipid sacs. All copepods accounted for 41–98% of total zooplankton abundance. Juvenile euphausiids were the second most important component contributing between 1 and 20% of total abundance. Pteropods, mainly Limacina inflata, were important members of the pelagic community at two sites, accounting for 44 and 53% of total abundance. Average mesozooplankton biomass in the upper 200 m was 8.0 g dry weight m⁻², ranging from 4.3 to 11.5 g dry weight m⁻². With the exception of Calanussimillimus, gut pigment contents and feeding activity of copepod species were low, suggesting that some species, after having stored large lipid reserves, had probably started undergoing developmental arrest. Daily mesozooplankton grazing impact, measured using in situ gut fluorescence techniques and in vitro incubations, varied widely from <1 to 8% (mean 3.5%) of phytoplankton standing stock, and from 5 to 102% (mean 36%) of primary production. The highest grazing impact was found northeast of the island co-incident with the lowest phytoplankton biomass and primary production levels. Received: 30 October 1996 / Accepted: 23 February 1997     

Role of deep sponge grounds in the Mediterranean Sea: a case study in southern Italy

The Mediterranean spongofauna is relatively well-known for habitats shallower than 100 m, but, differently from oceanic basins, information upon diversity and functional role of sponge grounds inhabiting deep environments is much more fragmentary. Aims of this article are to characterize through ROV image analysis the population structure of the sponge assemblages found in two deep habitats of the Mediterranean Sea and to test their structuring role, mainly focusing on the demosponges Pachastrella monilifera Schmidt, 1868 and Poecillastra compressa (Bowerbank, 1866). In both study sites, the two target sponge species constitute a mixed assemblage. In the Amendolara Bank (Ionian Sea), where P. compressa is the most abundant species, sponges extend on a peculiar tabular bedrock between 120 and 180 m depth with an average total abundance of 7.3 ± 1.1 specimens m⁻² (approximately 230 gWW m⁻² of biomass). In contrast, the deeper assemblage of Bari Canyon (average total abundance 10.0 ± 0.7 specimens m⁻², approximately 315 gWW m⁻² of biomass), located in the southwestern Adriatic Sea between 380 and 500 m depth, is dominated by P. monilifera mixed with living colonies of the scleractinian Madrepora oculata Linnaeus, 1758, the latter showing a total biomass comparable to that of sponges (386 gWW m⁻²). Due to their erect growth habit, these sponges contribute to create complex three-dimensional habitats in otherwise homogenous environments exposed to high sedimentation rates and attract numerous species of mobile invertebrates (mainly echinoderms) and fish. Sponges themselves may represent a secondary substrate for a specialized associated fauna, such zoanthids. As demonstrated in oceanic environments sponge beds support also in the Mediterranean Sea locally rich biodiversity levels. Sponges emerge also as important elements of benthic–pelagic coupling in these deep habitats. In fact, while exploiting the suspended organic matter, about 20% of the Bari sponge assemblage is also severely affected by cidarid sea urchin grazing, responsible to cause visible damages to the sponge tissues (an average of 12.1 ± 1.8 gWW of individual biomass removed by grazing). Hence, in deep-sea ecosystems, not only the coral habitats, but also the grounds of massive sponges represent important biodiversity reservoirs and contribute to the trophic recycling of organic matter.     

Recovery of Aboveground Plant Biomass and Productivity After Fire in Mesic and Dry Black Spruce Forests of Interior Alaska

Plant biomass accumulation and productivity are important determinants of ecosystem carbon (C) balance during post-fire succession. In boreal black spruce (Picea mariana) forests near Delta Junction, Alaska, we quantified aboveground plant biomass and net primary productivity (ANPP) for 4 years after a 1999 wildfire in a well-drained (dry) site, and also across a dry and a moderately well-drained (mesic) chronosequence of sites that varied in time since fire (2 to ∼116 years). Four years after fire, total biomass at the 1999 burn site had increased exponentially to 160 ± 21 g m⁻² (mean ± 1SE) and vascular ANPP had recovered to 138 ± 32 g m⁻² y⁻¹, which was not different than that of a nearby unburned stand (160 ± 48 g m⁻² y⁻¹) that had similar pre-fire stand structure and understory composition. Production in the young site was dominated by re-sprouting graminoids, whereas production in the unburned site was dominated by black spruce. On the dry and mesic chronosequences, total biomass pools, including overstory and understory vascular and non-vascular plants, and lichens, increased logarithmically (dry) or linearly (mesic) with increasing site age, reaching a maximum of 2469 ± 180 (dry) and 4008 ± 233 g m⁻² (mesic) in mature stands. Biomass differences were primarily due to higher tree density in the mesic sites because mass per tree was similar between sites. ANPP of vascular and non-vascular plants increased linearly over time in the mesic chronosequence to 335 ± 68 g m⁻² y⁻¹ in the mature site, but in the dry chronosequence it peaked at 410 ± 43 g m⁻² y⁻¹ in a 15-year-old stand dominated by deciduous trees and shrubs. Key factors regulating biomass accumulation and production in these ecosystems appear to be the abundance and composition of re-sprouting species early in succession, the abundance of deciduous trees and shrubs in intermediate aged stands, and the density of black spruce across all stand ages. A better understanding of the controls over these factors will help predict how changes in climate and fire regime will affect the carbon balance of Interior Alaska. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Mesozooplankton beneath the summer sea ice in McMurdo Sound,Antarctica: abundance,species composition,and DMSP content

The summer Phaeocystis antarctica bloom increases under-ice phytoplankton biomass in McMurdo Sound, Antarctica. The magnitude of mesozooplankton grazing on this bloom is unknown, and determines whether this production is available to the pelagic food web. We measured mesozooplankton abundance and body content of dimethylsulfoniopropionate (DMSP) during the McMurdo Sound austral summer (2006 and 2006–2007). Abundance varied from 20 to 4,500 ind. m⁻³ (biomass 0.02–274.0 mg C m⁻³), with peaks in mid-December and late-January/February. Abundance was higher but total zooplankton biomass lower in our study compared to previous reports. Copepods and the pteropod Limacina helicina dominated the zooplankton in both abundance and biomass. DMSP was detected in all zooplankton groups, with highest concentrations in copepod nauplii and L. helicina (95 and 54 nmol mg⁻¹ body C, respectively). Experiments suggested that L. helicina obtains DMSP by directly grazing on P. antarctica, which often accumulates to high biomass under the summer sea ice in McMurdo Sound.     

Effects of dilution stress on the functioning of a saline Mediterranean stream

The effects of seasonality and dilution stress on the functioning of Rambla Salada, a hypersaline Mediterranean stream in SE Spain, were evaluated. The stream is subject to diffuse freshwater inputs from the drainage of intensively irrigated agriculture in the catchment and periodic losses of water through an irrigation channel. Metabolic rates and the biomass of primary producers and consumers were estimated over a 2-year period. During the first year several dilution events occurred, while during the second year the salinity recovery reached predisturbance levels. Functional indicators were compared in the disturbance and recovery salinity periods. Primary production and respiration rates in the Rambla Salada ranged between 0.07–21.05 and 0.19–17.39 g O₂ m⁻² day⁻¹, respectively. The mean values for these variables were 7.35 and 5.48 g O₂ m⁻² day⁻¹, respectively. Mean net daily metabolism rate was 1.87 ± 0.52 g O₂ m⁻² day⁻¹ and mean production/respiration ratio was 2.48 ± 1.1, reflecting autotrophic metabolism. The metabolic rates showed the typical seasonal pattern of Mediterranean open canopy streams. Therefore, gross primary production (GPP) and ecosystem respiration (ER) registered maximum values in summer, intermediate values in spring and autumn and minimum values in winter. The metabolic rates and biomass of consumers were greater in the disturbance period than in the recovery period. However, they did not show significant differences between periods due to their important dependence on seasonal cycle. Seasonality accounted for much of the temporal variability in GPP and ER (76% and 83% in the multiregression models, respectively). Light availability seems to be the most important factor for GPP and ER in the Rambla Salada. Autotrophic biomass responded more to variations in discharge and conductivity than to seasonal variations. In fact, it was severely affected by freshwater inputs after which the epipelic biomass decreased significantly and Cladophora glomerata proliferated rapidly. Epipelic algal biomass was the most sensitive parameter to dilution disturbance. Handling editor: Luigi Naselli-Flores     

Phytoplankton biomass,P-I relationships and primary production in the Weddell Sea,Antarctica, during the austral autumn

An investigation into the changing phytoplankton biomass and total water column production during autumn sea ice formation in the eastern Weddell Sea, Antarctica showed reduced biomass concentrations and extremely low daily primary production. Mean chlorophyll-a concentration for the entire study period was extremely low, 0.15±0.01 mg.m⁻³ with a maximum of 0.35 mg.m⁻³ found along the first transect to the east of the grid. Areas of low biomass were identified as those either associated with heavy grazing or with deep mixing and corresponding low light levels. In most cases phytoplankton in the <20-μm size classes dominated. Integrated biomass to 100 m ranged from 7.1 to 28.0 mg.m⁻² and correlated positively with surface chlorophyll-a concentrations. Mean P^Bmax (photosynthetic capacity) and α^B (initial slope of the photosynthesis-irradiance curve) were 1.25±0.19 mgC. mgChla ⁻¹.h⁻¹ and 0.042±0.009 mgC.mgChla ⁻¹.h⁻¹.(μmol.m⁻².s⁻¹)⁻¹ respectively. The mean index of photoadaptation,I _k, was 32.2±4.0 μmol.m⁻².s⁻¹ and photoinhibition was found in all cases. Primary production was integrated to the critical depth (Z _cr) at each production station and ranged from 15.6 to 41.5 mgC.m⁻².d⁻¹. It appears that, other than grazing intensity, the relationship between the critical depth and the mixing depth (Z _mix) is an important factor as, ultimately, light availability due both to the late season and growing sea ice cover severely limits production during the austral autumn.     

Reproduction,population dynamics and production of <Emphasis Type="Italic">Nereis falsa</Emphasis> (Nereididae: Polychaeta) on the rocky coast of El Kala National Park,Algeria

The polychaete Nereis falsa Quatrefages, 1866 is present in the area of El Kala National Park on the East coast of Algeria. Field investigations were carried out from January to December 2007 to characterize the populations’ reproductive cycle, secondary production and dynamics. Reproduction followed the atokous type, and spawning occured from mid-June to the end of August/early September when sea temperature was highest (20–23°C). The diameter of mature oocytes was approximately 180 μm. Mean lifespan was estimated to about one year. In 2007, the mean density was 11.27 ind. m⁻² with a minimum of 7.83 ind. m⁻² in April and a maximum of 14.5 ind. m⁻² in February. The mean annual biomass was 1.36 g m⁻² (fresh weight) with a minimum of 0.86 g m⁻² in December and a maximum of 2.00 g m⁻² in June. The population consisted of two cohorts distinguishable from size frequency distributions. One cohort corresponded to the recruitment of 2006 and the other appeared during the study period in September 2007. The annual production of N. falsa was 1.45 g m⁻² year⁻¹, and the production/biomass ratio was 1.07 year⁻¹.     

Biomass, carbonate standing stock and production of the mediterranean coralCladocora caespitosa (L.)

Summary The Mediterranean coralCladocora caespitosa often occurs in large beds, i.e. populations of hemispherical clonies with stock densities varying between 1.9 and 4 coloneis ·m⁻². Laboratory measurements of volume, skeleton weight, surface and number of corallites per colony, coupled with mean annual growth rates evaluated through sclerochronology, allowed for the estimation of biomass, skeleton bulk density, calcimass (carbonate standing stock) and secondary production (both organic and inorganic) of twoC. caespitosa beds at 4 and 9 m depth. The mean colony biomass varied between 0.73 and 0.99 kg dw ·m⁻², corresponding to a calcimass between 2 and 5 kg CaCO₃·m⁻². Organic secondary production was 215.5–305.4 g dw of polyps ·m⁻²·y⁻¹, while the potential (mineral) production was 1.1–1.7 kg CaCO₃·m⁻²·y⁻¹, for the year 1996–1997. These values show thatC. caespitosa is one of the major carbonate producers within the Mediterranean and one of the major epibenthic species originating stable carbonate frameworks both in recent and past times.     

Simultaneous nutrients and carbon removal during pretreated swine slurry degradation in a tubular biofilm photobioreactor

The biodegradation potential of an innovative enclosed tubular biofilm photobioreactor inoculated with a Chlorella sorokiniana strain and an acclimated activated sludge consortium was evaluated under continuous illumination and increasing pretreated (centrifuged) swine slurry loading rates. This photobioreactor configuration provided simultaneous and efficient carbon, nitrogen, and phosphorous treatment in a single-stage process at sustained nitrogen and phosphorous removals efficiencies ranging from 94% to 100% and 70–90%, respectively. Maximum total organic carbon (TOC), NH₄ ⁺, and PO₄ ³⁻ removal rates of 80 ± 5 g C m_r ⁻³ day⁻¹, 89 ± 5 g N m_r ⁻³ day⁻¹, and 13 ± 3 g P m_r ⁻³ day⁻¹, respectively, were recorded at the highest swine slurry loadings (TOC of 1,247 ± 62 mg L⁻¹, N–NH₄ ⁺ of 656 ± 37 mg L⁻¹, P–PO₄ ³⁺ of 117 ± 19 mg L⁻¹, and 7 days of hydraulic retention time). The unusual substrates diffusional pathways established within the phototrophic biofilm (photosynthetic O₂ and TOC/NH₄ ⁺ diffusing from opposite sides of the biofilm) allowed both the occurrence of a simultaneous denitrification/nitrification process at the highest swine slurry loading rate and the protection of microalgae from any potential inhibitory effect mediated by the combination of high pH and high NH₃ concentrations. In addition, this biofilm-based photobioreactor supported efficient biomass retention (>92% of the biomass generated during the pretreated swine slurry biodegradation).     

Exposure to indoor fungi in different working environments: A comparative study

In this study an attempt was made to evaluate the qualitative and quantitative fungal burden (load) in five different working environments of South Assam (India) and the possible risks of indoor fungi to employees and stored products. Fungal concentrations in different working environments were studied using a Burkard personal petriplate sampler. The survey was done in five different working environments for one year. A total of 76 fungal types were recorded in the indoor air of South Assam during the survey period. The maximum fungal concentration (5,437.6 ± 145.3 CFU m⁻³ air) was recorded in the indoor air of medical wards, followed by the paper-processing industry (3,871.7 ± 93.4 CFU m⁻³ air). However the lowest concentration was observed in the indoor air of a bakery (1,796.8 ± 54.4 CFU m⁻³ air). The most dominant fungal genera were Aspergillus (34.2%) followed by Penicillium (17.8%), Geotrichum (7.0%) and the most dominant fungal species were Aspergillus fumigatus (2,650.4 CFU m⁻³ air) followed by Aspergillus flavus (1,388.2 CFU m⁻³ air), Geotrichum candidum (1,280.3 CFU m⁻³ air), Aspergillus niger (783.3 CFU m⁻³ air), and Penicillium aurantiovirens (774.0 CFU m⁻³ air). The fungal species viz., Aspergillus fumigatus, Penicillium aurantiovirens, Aspergillus flavus, Aspergillus niger, Geotrichum candidum, and Penicillium thomii, which were recorded well above threshold levels, may lead to adverse health hazards to indoor workers. Setting occupational exposure limits for indoor fungal spores as reference values is obligatory for prevention and control of adverse effects of indoor fungal exposure.     

Drift-ice and under-ice water communities in the Gulf of Bothnia (Baltic Sea)

The algal, protozoan and metazoan communities within different drift-ice types (newly formed, pancake and rafted ice) and in under-ice water were studied in the Gulf of Bothnia in March 2006. In ice, diatoms together with unidentified flagellates dominated the algal biomass (226 ± 154 μg ww l⁻¹) and rotifers the metazoan and protozoan biomass (32 ± 25 μg ww l⁻¹). The under-ice water communities were dominated by flagellates and ciliates, which resulted in lower biomasses (97 ± 25 and 21 ± 14 μg ww l⁻¹, respectively). The under-ice water and newly formed ice separated from all other samples to their own cluster in hierarchical cluster analysis. The most important discriminating factors, according to discriminant analysis, were chlorophyll-a, phosphate and silicate. The under-ice water/newly formed ice cluster was characterized by high nutrient and low chlorophyll-a values, while the opposite held true for the ice cluster. Increasing trends in chlorophyll-a concentration and biomass were observed with increasing ice thickness. Within the thick ice columns (>40 cm), the highest chlorophyll-a concentrations (6.6–22.2 μg l⁻¹) were in the bottom layers indicating photoacclimation of the sympagic community. The ice algal biomass showed additional peaks in the centric diatom-dominated surface layers coinciding with the highest photosynthetic efficiencies [0.019–0.032 μg C (μg Chl-a ⁻¹ h⁻¹) (μE m⁻² s⁻¹)⁻¹] and maximum photosynthetic capacities [0.43-1.29 μg C (μg Chl-a ⁻¹ h⁻¹)]. Rafting and snow-ice formation, determined from thin sections and stable oxygen isotopic composition, strongly influenced the physical, chemical and biological properties of the ice. Snow-ice formation provided the surface layers with nutrients and possibly habitable space, which seemed to have favored centric diatoms in our study.     

Copepod communities off Franz Josef Land (northern Barents Sea) in late summer of 2006 and 2007

Copepods are considered to be the main component of the Arctic marine zooplankton. We examined the copepod distribution and diversity off Franz Josef Land (northern Barents Sea) in August 2006 and 2007. A total of 18 and 14 copepod taxa were identified from the sampling layers (100–0 m or bottom–0 m) in 2006 and in 2007, respectively. There were no significant differences in the total copepod abundance between the years (means ± SE: 118,503 ± 24,115 individuals m⁻² in 2006 vs. 113,932 ± 28,564 individuals m⁻² in 2007). However, the copepod biomass in 2006 (4,518 ± 1,091 mg C m⁻²) exceeded clearly the value in 2007 (1,253 ± 217 mg C m⁻²). The copepod community showed low species richness and diversity in both years (Simpson index D: 0.34 and 0.38, respectively). Biomass of the large and small copepod species strongly decreased from 2006 to 2007. The total abundance of copepods was negatively correlated with water temperature in 2006 and positively correlated with salinity in 2007. The patchiness in copepod distribution was associated with local hydrography and temperature conditions.     

Cultivation of the green alga, Codium fragile (Suringar) Hariot, by artificial seed production in Korea

Codium fragile (Suringar) Hariot is an edible green alga farmed in Korea using seed stock produced from regeneration of isolated utricles and medullary filaments. Experiments were conducted to reveal the optimal conditions for nursery culture and out-growing of C. fragile. Sampling and measurement of underwater irradiance were carried out at farms cultivating C. fragile at Wando, on the southwestern coast of Korea, from October 2004 to August 2005. Growth of erect thalli and underwater irradiance were measured over a range of depths for three culture stages. During the nursery cultivation stage (Stage I), growth rate was greatest at 0.5 m depth (0.055 ± 0.032 mm day⁻¹), where the average midday irradiance over 60 days was 924 ± 32 μmol photons m⁻² s⁻¹. During the pre-main cultivation stage (Stage II), the greatest growth rate occurred at a depth of 2 m (0.113 ± 0.003 mm day⁻¹) with an average irradiance of 248 ± 116 μmol photons m⁻² s⁻¹. For the main cultivation stage (Stage III) of the alga, thalli achieved the greatest increase in biomass at 1 m depth (7.2 ± 1.0 kg fresh wt m⁻¹). These results suggest that optimal growth at each cultivation stages of C. fragile could be controlled by depth of cultivation rope.     

Ecological filtering by a dominant herb selects for shade tolerance in the tree seedling community of coastal dune forest

The regeneration niche is commonly partitioned along a gradient from shade-tolerant to shade-intolerant species to explain plant community assembly in forests. We examined the shade tolerance of tree seedlings in a subtropical coastal forest to determine whether the ecological filtering effect of a dominant, synchronously monocarpic herb (Isoglossa woodii) selects for species at either end of the light response continuum during the herb’s vegetative and reproductive phases. Photosynthetic characteristics of seedlings of 20 common tree species and the herb were measured. Seedlings were grown in the greenhouse at 12–14% irradiance, and their light compensation points measured using an open-flow gas exchange system. The light compensation points for the tree species were low, falling within a narrow range from 2.1 ± 0.8 μmol m⁻² s⁻¹ in Celtis africana to 6.4 ± 0.7 μmol m⁻² s⁻¹ in Allophylus natalensis, indicating general shade tolerance, consistent with a high and narrow range of apparent quantum yield among species (0.078 ± 0.002 mol CO₂ mol⁻¹ photon). Rates of dark respiration were significantly lower in a generalist pioneer species (Acacia karroo) than in a forest pioneer (C. africana), or in late successional phase forest species. We argue that the general shade tolerance, and phenotypic clustering of shade tolerance, in many tree species from several families in this system, is a result of ecological filtering by the prevailing low light levels beneath the I. woodii understorey, which excludes most light-demanding species from the seedling community.