Distribution patterns of micro- and meso-zooplankton communities in sea ice regions of Lützow-Holm Bay, East Antarctica

In the Southern Ocean, zooplankton research has focused on krill and macro-zooplankton despite the high densities of micro- and meso-zooplankton. We investigated their community structure in relation to different sea ice conditions around Japan’s Syowa Station in Lützow-Holm Bay, in the summers of 2011 and 2012. Zooplankton samples were collected using vertical hauls (0–150 m), with a closing net of 100-μm mesh size. The results of cluster analysis showed that the communities in this region were separated into fast ice, pack ice, and open ocean fauna. The fast ice fauna had lower zooplankton abundance (393.8–958.9 inds. m^?3) and was dominated by cyclopoid copepods of Oncaea spp. (54.9–74.8 %) and Oithona similis (6.6–19.9 %). Deep-water calanoid copepods were also found at the fast ice stations. Pack ice and open ocean fauna had higher zooplankton abundance (943.6–2,639.8 inds. m^?3) and were characterized by a high density of foraminiferans in both years (6.6–61.9 %). Their test size distribution indicated that these organisms were possibly released from melting sea ice. The pteropod Limacina spp. was a major contributor to total abundance of zooplankton in the open ocean zone in 2012 (26.4 %). The physical and/or biological changes between 2 years may affect the abundance and distribution of the dominant zooplankton taxa such as cyclopoid copepods, foraminiferans, and pteropods. Information on the relationships between the different species associated with sea ice will help to infer the possible future impacts of climate change on the sea ice regions.     

Distribution and abundance of Indo‐Pacific humpback dolphins in Leizhou Bay,China

Abstract

The Indo‐Pacific humpback dolphin (Sousa chinensis) is under severe threat in Chinese waters. Only four small populations of this dolphin are known to survive in the East China Sea and South China Sea. We conducted exploratory surveys from June to September 2005, and found a population of humpback dolphins in Leizhou Bay. Thirty‐eight individuals were identified and catalogued, of which 26 were photographed and re‐identified on more than one occasion, and nine were sighted on five or more occasions each. Our preliminary estimate of the size of the Leizhou population is about 237 individuals, second only to the Pearl River estuary population. We suggest that Leizhou Bay has the potential to serve as a “humpback dolphin sanctuary” in Chinese waters.     

Parameterization of surface irradiance and primary production in Århus Bay,SW Kattegat,Baltic Sea

The aims of the present study were to develop a parameterization of a one-year-long observed PAR time-series, apply the PAR parameterization in a primary production relation, and compare calculated and observed time-series of primary production. The PAR parameterization was applied in the generally used relation for the primary production (P _d): P _d = a(BI ₀ Z ₀) + b with observed photic depth (Z ₀) and Chl-a concentrations (B). It was tested whether the PAR parameterization in combination with this simple relation for primary production was able to describe the actual measured primary production. The study is based on a one year long time-series of PAR, CTD-casts (n = 45), and primary production measurements (n = 24) from Århus Bay (56°09′ N; 10°20′ E), south west Kattegat. Results showed a high and positive correlation between observed and calculated primary production in the bay, as based on the present PAR parameterization combined with the simple primary production relation. The developed PAR parameterization, which calculates total daily surface irradiance per day (M photons m^?2 d^?1), can be applied in any ecological application taking into account that it was developed for the latitude of 56° N.     

Distribution and production ofChironomus salinarius (Diptera: Chironomidae) in a shallow coastal lagoon in the Bay of Cádiz

The abundance, generation time and production ofChironomus salinarius larvae in a lagoon fish-pond system in the Bay of Cádiz were studied by taking monthly samples at 3 sites during 1991 and 1992. Numerical abundance and biomass of larvae showed considerable spatial, seasonal and interannual variation (ANCOVAs,P<0.001). The maximum mean annual density was 7048 larvae m^–2, and corresponded to a biomass of 3.08 g dry weight (DW) m^–2. It was recorded at the site with the lowest rate of water renewal. Seasonal patterns were similar at all sites, with main annual peaks of abundance and biomass in autumn-early winter. Chironomid density was positively related to the biomass of benthic macroalgae (P<0.001). The population studied was multivoltine with a probable average of five generations per year, with overlapping cohorts and a predominance of third- and fourth-instar larvae. Estimates of annual production ranged between 72.2 g DW m^–2 yr^–1 at the site with the lowest rate of water renewal in 1991 and 0.1 g DW m^–2 yr^–1 at the site with the highest rate of water renewal in 1992. Mean annual production and the production/biomass ratio for the system was estimated to be 16.8 g DW m^–2 yr^–1 and 12.7, respectively. Possible factors leading to the observed density fluctuations are discussed, as well as possible sources of error in production estimates.     

Does root glutamine synthetase control plant biomass production in Lotus japonicus L.?

To investigate the contribution of root cytosolic glutamine synthetase (GS) activity in plant biomass production, two different approaches were conducted using the model legume Lotus japonicus. In the first series of experiments, it was found that overexpressing GS activity in roots of transgenic plants leads to a decrease in plant biomass production. Using ¹⁵N labelling it was shown that this decrease is likely to be due to a lower nitrate uptake accompanied by a redistribution to the shoots of the newly absorbed nitrogen which cannot be reduced due to the lack of nitrate reductase activity in this organ. In the second series of experiments, the relationship between plant growth and root GS activity was analysed using a series of recombinant inbred lines issued from the crossing of two different Lotus ecotypes, Gifu and Funakura. It was confirmed that a negative relationship exists between root GS expression and plant biomass production in both the two parental lines and their progeny. Statistical analysis allowed it to be estimated that at least 13% of plant growth variation can be accounted for by variation in GS activity. Received: 24 September 1998 / Accepted: 14 April 1999     

The partitioning of carbohydrates and the biomass of leaves in Populus tremula L . canopy

 This study was aimed at making a quantitative evaluation of the biomass, carbohydrates and mineral nutrients partitioning in the canopy of aspen (Populus tremula L.) growing in a forest stand. Tree canopy biomass was divided into ten equal horizontal layers and the material for the study was sampled from all canopy layers. The results indicated that the specific leaf mass and the dry matter content increased but the area of leaves decreased toward the top of the canopy. The content of the non-structural carbohydrates depended largely on the position of the leaves in the canopy and the N, P and K contents in the leaves, reaching a maximum in the upper canopy layers better exposed to light. Regression analysis showed a linear relationship between the leaf mass per area and the percentage of dry matter on the one hand and the content of carbohydrates, N, P and K in the canopy on the other. Received: 11 March 1997 / Accepted: 16 June 1997     

The feeding ecology of Rüppell's Parrot,Poicephalus rueppellii,in the Waterberg,Namibia

Rüppell's Parrot, Poicephalus rueppellii, inhabits a markedly seasonal environment in Namibia and feed on plant seeds that respond to that seasonality. Although Rüppell's Parrots were seen feeding at 37 plant species they showed clear preferences. The diet was dominated by seeds, but also included other fruit, flowers (especially nectar), leaves, arthropods and bark. The arthropods were the larvae of lepidoptera, coleoptera and hemiptera, and spiders. Feeding was observed on 19 plant species during a year period and the proportion of observations/species/month was determined. Terminalia prunioides, Albizia anthelmintica and Acacia er/o/oba represent preferred foods and provided most of the diet at particular times of the year. The fruiting periods of most plants were highly seasonal and the parrots changed diet frequently; however, T. prunioides holds its pods all year round and was used more than any other species. Monthly diet was also analysed by food type. Seeds formed the greatest part of the diet from December to August, but flowers and insects formed a major part of the diet prior to the onset of the rains. In particular, A. anthelmintica provided nectar and harboured insects when there was very little other food available. It may be critically important in the east of this parrot's distribution where the winter-fruiting Faidherbia albida is not found. For two species there Was some evidence that soft, slightly unripe drupes were preferred over riper, harder fruits. Rüppell's Parrot is omnivorous but mostly a seed predator. It survives in a highly seasonal environment by exploiting a wide range of food items.     

The contribution of size-fractionated plankton to biomass and primary production of phytoplankton in saline–alkaline ponds

Primary productivity, biomass and chlorophyll-a of size fractionated phytoplankton (<0.22 m, <3 m, <8 m, <10 m, <40 m, <64 m, <112 m and <200 m) were estimated in 6 ponds and 5 experimental enclosures. The results showed that the planktonic algae less than 10 m are important in the biomass and production of phytoplankton in saline–alkaline ponds. The production of size fractionated phytoplankton corresponding to <112 m, <10 m and <3 m in saline–alkaline ponds were 10.5 ± 6.6 , 8.6 ± 5.4 and 0.33 ± 0.1 mgC l^–1 d^–1, respectively. Mean community respiration rate was 1.80 ± 0.73, 1.69 ± 0.90 and 1.38 ± 1.12 mgC l^–1 d^–1, respectively. The average production of phytoplankton corresponding to micro- (10–112 m), nano- (3–10 m) and pico- (<3 m) were 1.61, 8.30 and 0.33 mgC l^–1 d^–1, respectively. The ratio of those to the total phytoplankton production was 15%, 79% and 3%, respectively. The mean respiration rate of the different size groups was 0.11, 0.31 and 1.38 mgC l^–1 d^–1; the ratio of those to total respiration of phytoplankton was 6%, 17% and 77%, respectively. The production of size-fractionated phytoplankton corresponding to <200 m, <10 m and <3 m in enclosures was 2.19 ± 1.63, 2.08 ± 1.75 and 0.22 ± 0.08 mgC l^–1 d^-1, respectively. Mean community respiration rates were 1.25 ± 1.55, 1.17 ± 1.42 and 0.47 ± 0.32 mgC l^–1 d^–1, respectively. The average production of phytoplankton corresponding to micro- (10–200 m), nano- (3–10 m) and pico- (<3 m) plankton was 0.11, 1.86 and 0.22 mgC l^–1 d^–1, respectively. The ratio of those to the total production of phytoplankton was 5%, 85% and 10%, respectively. The mean respiration rate of different size groups were 0.08, 0.72 and 0.46 mgC l^–1 d^–1, the ratio of those to total respiration of phytoplankton was 6%, 57% and 37%, respectively. The concentrations of chlorophyll-a of the phytoplankton in the corresponding size of micro- (10–112 m), nano- (3–10 m) and pico- (<3 m) plankton in the experimental ponds were 19.3, 98.2 and 11. 9 g l^–1, respectively. The ratio of those to the total chlorophyll-a was 15%, 76% and 9%, respectively. The concentrations of chlorophyll-a of phytoplankton micro- (10–200 m), nano- (3–10 m) and pico- (<3 m) plankton in enclosures were 1.7, 34.3 and 3.0 g l^–1, respectively. The ratio of those to the total chlorophyll-a was 4%, 88% and 8%, respectively.     

Foraging behavior of Adélie penguins during incubation period in Lützow-Holm Bay

The diving behavior of Adélie penguins Pygoscelis adeliae was investigated using time–depth recorders during the incubation period in the fast sea-ice area of Lützow-Holm Bay, Antarctica. Dive profiles and activity/time allocation suggested that penguins were obligated to walk on the fast-ice for 90–100 km until a polynya, which they used as an access to the pack-ice zone. Dive depth did not differ between males and females, though males’ dive duration was longer than that of females. Dive depth was slightly shallower and dive duration was shorter during the incubation than during the chick-rearing phase. Birds dove throughout the day, although less frequently around midnight, and there was no clear diel change in dive depth. This daily dive pattern during incubation period was similar to that previously observed during the chick-rearing period in a fast sea-ice area, but differed from that observed in sea-ice-free area. Variations in diving behavior resulted from different environmental conditions, such as foraging area with different sea-ice condition, as well as from different life history strategies.     

Distribution and Density of Seals in Pil'tun Bay (Northeastern Sakhalin) in the Summer–Autumn Period

The results of seal counts performed during the summer–autumn period of the years 1999–2001 in Pil'tun Bay from onboard Zodiak motor boats and Mi-8 and Mi-8MTV helicopters have been analyzed. The information is presented on the density of seals in the bay. The heterogeneous distribution pattern of seals in the bay and the presence of intermittent migrations provide favorable conditions for foraging in young animals.     

Temporal variability in abundance and biomass of ciliates and copepods in the eutrophicated part of Kaštela Bay (Middle Adriatic Sea)

Seasonal variations in abundance and carbon biomass of ciliated protozoa and micrometazoa were studied from May 1998 to November 1999 in the eutrophicated area of Katela Bay (Middle Adriatic Sea). Ciliates showed peaks in spring and autumn, primarily due to changes in the abundance and biomass of tintinnines, which participated in total ciliate abundance and biomass with 40.48 and 60.02%, respectively. The highest tintinnine density was 4,278 ind. l^–1, while their average biomass varied from 0.611 to 26.557 gC l^–1 . Maximal average density and biomass of non-loricates were 1,430 ind. l^–1 and 3.925 gC l^–1, respectively. The micrometazoa community was dominated by copepod nauplii, especially during the summer and autumn. The copepod biomass ranged between 3.47 and 26.75 gC l^–1 . High abundance and biomass values of the investigated zooplankton groups point to an important role of these organisms in the secondary production in the Bay, indicating that they may be (1) a crucial factor in controlling the populations of nano-/pico-phytoplankton and heterotrophic nanoflagellates, and (2) a significant prey for larger micrometazoans.     

Biomass and primary production of Cladophora glomerata (L.) Kütz. in the Neva Estuary

The dynamics of the biomass, primary production, and P/B ratio of floating and attached forms of green filamentous alga Cladophora glomerata (L.) Kütz. was studied for the shallow water littoral area of the Neva Estuary in 2003–2006. The biomass of the floating algae constituted up to 70% of the total biomass, and the primary production reached up to 90% of the total for the depths of 0–1 m from the middle of July to the end of August.     

Changes in Adélie penguin breeding populations in Lützow-Holm Bay, Antarctica, in relation to sea-ice conditions

The Adélie penguin, Pygoscelis adeliae, an important component of the Antarctic marine ecosystem, is closely associated with sea ice. Using data collected by Japanese Antarctic Research Expeditions since the 1960s, we examined trends in breeding populations of this species around Lützow-Holm Bay. Ten colonies ranging in size from 10 to 2,500 individuals were counted along the Soya Coast. Populations fluctuated synchronously, and overall increased at most colonies, except for two: one located deep inside the bay and another where human disturbance was substantial. Populations tended to increase during, or after, periods of sparse sea ice in summer, a condition that occurred once every decade. An increase in population size also occurred 5 years after a winter of extensive sea ice and after a winter of especially reduced sea ice.     

Distribution and interspecific correlation of root biomass density in an arid Elaeagnus angustifolia–Achnatherum splendens community

Main objective of this study was to determine the interspecific relationships between two dominant species in terms of root distribution in a typical arid tree-herbage (Elaeagnus angustifolia–Achnatherum splendens) community at Xidatan, Pingluo County, Ningxia Autonomous Region, Northwest China. Eight concentric zones (namely, Z1–Z8) were set from the bases of E. angustifolia individuals to the open lands and five soil profiles were excavated in each zone. Each soil profile was divided into five layers at the depths of 0–10 cm, 10–30 cm, 30–60 cm, 60–100 cm and 100–150 cm. Roots were collected for each species, and soil water content (SWC) and soil bulk density (SBD) were measured for each layer. We found noteworthy roots layer separation in the sub-canopy zones (Z1–Z4). The soil layers with highest fine root biomass density (FRBD) of A. splendens was primarily in the 0–10 cm, which were significantly shallower than those of E. angustifolia; whereas in the inter-canopy zones (Z5–Z8), inconsistent separation, or even overlapping of highest-FRBD-layers emerged between the two dominant species. Correlation analyses showed that negative correlations of FRBD between the two species mainly occurred in those soil layers with relatively higher FRBD and lower SWC. In contrast, positive correlations corresponded with relatively lower FRBD and higher SWC.     

The spring development of phytoplankton in Lake Erken: species composition,biomass, primary production and nutrient conditions — a review

Relative abundance and within-lake distributions of three fishes, northern redbelly dace (Phoxinus eos), finescale dace (Phoxinus neogaeus), and central mudminnow (Umbra limi), were examined using minnow traps in Tuesday Lake, a small bog lake in the Upper Peninsula, Michigan. For these species, catches in minnow traps placed at the perimeter of the lake were 21 to 52 times higher than catches in midlake traps. Variance: mean ratios of perimeter trap catches indicated that both dace species were highly aggregated while the distribution of mudminnows was less aggregated or random. Over an 11 day period during which all fish caught were removed from the lake, catch per unit effort (CPUE) of both dace species declined in response to fish removal. In contrast, CPUE for mudminnows was low initially, increased to an asymptote and then declined only in the last 5 days of the fish removal. The patterns of CPUE for mudminnows indicated that mudminnow trapability and/or activity was reduced in the presence of high densities of dace. The low abundance of dace in traps with many mudminnows suggested mudminnows avoided traps already containing dace. Throughout the removal period, CPUE provided an accurate index of dace abundance, whereas this was true for mudmnnows only after dace populations had been reduced drastically. Therefore, in any use of minnow traps to estimate populations, both spatial distributions and relative species abundance of small fishes must be taken into account.     

Distribution and dynamics of bacterioplankton production in a polymictic tropical lake (Lago Xolotlán,Nicaragua)

From 1988 to 1993 we assessed the variability of bacterioplankton production and biomass in Lake Xolotlán (L. Managua), Nicaragua via [3H]thymidine incorporation into DNA and cell counting. Bacterial production ranged from 3 to 8 μg C l-1 h-1, and since production was equal throughout the water column, areal production was high (≈ 600–1200 mg C m-2 d-1). Bacterial abundance in Lake Managua was extremely high, 7–30 × 109 cells l-1. Thus, specific rates of bacterial production were low. There was a strong correlation between production and number and the specific rate of bacterial production was constant. Comparable measurements of production via [3H]leucine incorporation into proteins indicated that bacteria were experiencing ‘balanced growth’. We conclude that bacterioplankton in Lake Xolotlán had reached its carrying capacity and a significant correlation between bacterial production and concentration of phaeophytin implied that dead or dying algae was the limiting substrate for bacterioplankton. The majority of bacterial number and most of bacterial production (up to 75%) were associated with particles in the >3-μm fraction, probably lysing algal cells to which bacterioplankton were ‘attached’. Grazing on bacterioplankton must be low and bacteria should be a ‘sink’ for organic matter in Lake Xolotlán. This revised version was published online in July 2006 with corrections to the Cover Date.     

Spatial distributions and population dynamics of two salp species, Ihlea racovitzai and Salpa thompsoni, in the waters north of Lützow-Holm Bay (East Antarctica) during austral summers of 2005 and 2006

Information on the sequences of generations and reproductive states of salps in the Southern Ocean is essential for an improved understanding of salp population growth, although changes in distribution patterns of two species of salps, Salpa thompsoni and Ihlea racovitzai, in the Southern Ocean have the potential to alter the Southern Ocean ecosystem. We used stratified, quantitative sampling from the surface to 2,000 m depth with an RMT 8 net in January of 2005 and 2006 to determine the distribution and population structure of salps in the north of Lützow-Holm Bay, East Antarctica. Ihlea racovitzai occurred in both 2005 and 2006, but S. thompsoni was found only in 2005. Ihlea racovitzai occurred abundantly along the ice edge where Antarctic Winter Water was well developed, whereas S. thompsoni was more abundant at northern stations affected by warm Modified Circumpolar Deep Water. Small solitary stages of I. racovitzai dominated in 2005, but they had declined significantly by 2006. The S. thompsoni population was composed of small immature aggregates and mature solitary stages, suggesting that the solitary stages were reproducing. We did not find mature aggregate and immature solitary stages in the present study and thus suggested that S. thompsoni was unable to complete its life cycle in the north of Lützow-Holm Bay because of failure of sexual reproduction in the aggregate stage. The S. thompsoni population was therefore probably transported to our study area by advection.     

Biological characteristics of euphausiids preyed upon by Adélie penguins in relation to sea-ice conditions in Lützow-Holm Bay,Antarctica

We examined the biological characteristics of euphausiids found in the stomachs of Adélie penguins in relation to sea-ice conditions in Lützow-Holm Bay over three seasons. Euphausiids, especially Euphausia superba, proved to be a staple food for Adélie penguins irrespective of the ice condition. Body length and maturity-stage compositions of euphausiids were different among seasons, probably reflecting sea-ice condition in summer. The mean body length decreased and maturity regressed during each season in E. superba, which was partly attributable to the selective feeding on large, mature female krill by Adélie penguins. The 1995/1996 year class of E. superba, which was spawned when the sea ice was most developed, was strong and conspicuous in the 1996/1997 and 1997/1998 seasons. This vigor indicates that sea ice provided females with good spawning conditions and larvae with good growth and survival rates.     

More plant biomass results in more offspring production in annuals,or does it?

Competitive ability in plants has been previously measured almost exclusively in terms of traits related to growth (biomass) or plant size. In this study, however, we used a multi‐species competition experiment with six annuals to measure relative competitive ability in terms of reproductive output, i.e. the number of offspring produced for the next generation. Under greenhouse conditions, plants of each species were started in pots from germinating seeds and were grown singly (free of competition) and at high density in both monocultures and in mixtures with all study species. Several traits traditionally regarded as determinants of competitive ability in plants were recorded for each species grown singly, including: seed mass, germination time, early growth rate and potential plant size (biomass and height). Under competition, several traits were recorded as indicators of relative performance in both monocultures and mixtures, including: biomass of survivors, total number of survivors, number of reproductive survivors, and reproductive output (total seed production) of the survivors. As expected, species that grew to a larger biomass in isolation had higher seed production in isolation. However, none of the traditional plant growth/size‐related traits, measured either in isolation or under competition, could predict between species variation in reproductive output under competition in either monocultures or mixtures. In mixtures, 97% of this variation in reproductive output could be explained by between‐species variation in the number of reproductive survivors. The results indicate that traits measured on plants grown singly may be poor predictors of reproductive output under competition, and that species’ rank order of competitive ability in terms of the biomass of survivors may bear no relationship to their rank order in terms of the number of offspring produced by these survivors. This has important implications for the interpretation of mechanisms of species coexistence and community assembly within vegetation.     

Assessing fine-root biomass and production in a Scots pine stand – comparison of soil core and root ingrowth core methods

Soil core and root ingrowth core methods for assessing fine-root (< 2 mm) biomass and production were compared in a 38-year-old Scots pine (Pinus sylvestris L) stand in eastern Finland. 140 soil cores and 114 ingrowth cores were taken from two mineral soil layers (0–10 cm and 10–30 cm) during 1985–1988. Seasonal changes in root biomass (including both Scots pine and understorey roots) and necromass were used for calculating fine-root production. The Scots pine fine-root biomass averaged annually 143 g/m² and 217 g/m² in the upper mineral soil layer, and 118 g/m² and 66 g/m² in the lower layer of soil cores and ingrowth cores, respectively. The fine-root necromass averaged annually 601 g/m² and 311 g/m² in the upper mineral soil layer, and 196 g/m² and 159 g/m² in the lower layer of soil cores and ingrowth cores, respectively. The annual fine-root production in a Scots pine stand in the 30 cm thick mineral soil layer, varied between 370–1630 g/m² in soil cores and between 210 – 490 g/m² in ingrowth cores during three years. The annual production calculated for Scots pine fine roots, varied between 330–950 g/m² in soil cores and between 110 – 610 g/m² in ingrowth cores. The horizontal and vertical variation in fine-root biomass was smaller in soil cores than in ingrowth cores. Roots in soil cores were in the natural dynamic state, while the roots in the ingrowth cores were still expanding both horizontally and vertically. The annual production of fine-root biomass in the Scots pine stand was less in root ingrowth cores than in soil cores. During the third year, the fine-root biomass production of Scots pine, when calculated by the ingrowth core method, was similar to that calculated by the soil core method. Both techniques have sources of error. In this research the sampling interval in the soil core method was 6–8 weeks, and thus root growth and death between sampling dates could not be accurately estimated. In the ingrowth core method, fine roots were still growing into the mesh bags. In Finnish conditions, after more than three growing seasons, roots in the ingrowth cores can be compared with those in the surrounding soil. The soil core method can be used for studying both the annual and seasonal biomass variations. For estimation of production, sampling should be done at short intervals. The ingrowth core method is more suitable for estimating the potential of annual fine-root production between different site types.