Photoadaptation of an ice algal community in thin sea ice,Saroma-Ko Lagoon,Hokkaido, Japan

We investigated the shade adaptation of a seasonally well-developed ice algal community in thin sea ice at Saroma-Ko Lagoon, Hokkaido, Japan on 3–4 March 2006 and 4–5 March 2007, by examining photosynthetic pigment concentrations, the chlorophyll a-specific light-absorption coefficient (a _ph *), and the light-saturation index (E _k ). The high proportions of photosynthetic pigments, including chlorophyll a, fucoxanthin, and chlorophyll c, and the low values of a _ph *₍₄₄₀₎ and a _ph *₍₆₇₅₎ suggested that the lagoon’s ice algal community was shade-adapted. The high ratio of E _k to total photosynthetically active radiation (PAR) in the ice algal habitat suggested that the degree of shade adaptation is weak. Scaling of E _k to total PAR could be extended to studies of the degree of photoadaptive succession of ice algal communities in the Northern Hemisphere. The degree of shade adaptation of ice algal communities in the Northern Hemisphere might be related to ice thickness, regardless of latitude.     

Nitrogen uptake in the infiltration community, an ice algal community in Antarctic pack-ice

An infiltration community was the dominating ice algal community in pack-ice off Queen Maud Land, Southern Ocean, in January 1993. The community was dominated by autotrophic processes, and the most common species were the prymnesiophyte Phaeocystis antarctica and the diatoms Chaetoceros neglectus and Fragilariopsis cylindrus. The concentration of chlorophyll a was 1.3–47.9 μg l⁻¹, and the inner part of the community was nitrate depleted. Uptake rates of nitrate, nitrite, ammonium, urea and amino acids were measured using ¹⁵N. Nitrate was the major nitrogen source for ice algal growth (67 ± 6% nitrate uptake). It is suggested that % nitrate uptake in the infiltration community decreases during the growth season, from 92% during spring (literature data) to 67% during summer. Scalar irradiance in the infiltration community was high and variable. It reached ca. 2000 μmol m⁻² s⁻¹ at some locations, and nitrate uptake rate was potentially photoinhibited at irradiances >500 μmol m⁻² s⁻¹. Nitrate uptake rate in an average infiltration community (0.6 m of snow cover) was lowered by 13% over a 2-week period due to photoinhibition. Received: 16 December 1996 / Accepted: 5 January 1998     

Relationships between bird community and habitat structure in shelterbelts of Hokkaido,Japan

Summary The relationship between the bird community and habitat structure in wind shelterbelts of Ishikari district was examined.Breeding birds were classified into nesting guilds (hole, canopy, and bush) and also into foraging guilds (outside, canopy, and bush) Both density and species richness in the outside-foraging guild were positively related to forest age variables. On the other hand, bird density in all three nesting guilds and the other two foraging guilds (canopy and bush) was correlated with the vegetation cover of their nesting or foraging sites, and species richness was positively correlated with tree species complexity variables.Bird species diversity (BSD) was closely related to tree species complexity, but not to foliage height diversity (FHD) within woods. However, if woods were re-classified into two groups such as natural and artificial and these were separately analysed, the correlation between BSD and FHD was significant.From these results, it is concluded that both FHD and tree species complexity should be considered together in order to predict BSD within forests. A new index is proposed for this purpose, and its usefulness discussed.     

Diadinoxanthin cycle of the bottom ice algal community during spring in McMurdo Sound,Antarctica

Using the ice algal community growing at the bottom of the annual sea ice in McMurdo Sound Antarctica, the response of the photoprotective diadinoxanthin (DD)-cycle to exposure to light was investigated. Changes in pigment concentration were detected using high-performance liquid chromatography. A light mixing simulator (LMS) was developed and used to simulate the pigment response to mixing in the upper water column. No DD-cycle was detected under the sea ice under natural light conditions. The DD-cycle was activated after exposure to surface natural light conditions and artificial light conditions. The first-order kinetic rates of the DD-cycle under constant artificial irradiance, natural irradiance and simulations with the LMS were found to be similar to other studies suggesting that ice algae do not vary the rate of deepoxidation depending on light history. Simulations under natural light using the LMS demonstrated that the response of the DD-cycle to static incubations and when subject to vertical mixing was not similar, and that static incubations overestimate DD-cycle activity over the long term. Algae in a simulated vertically mixed environment were able to increase the pool of xanthophyll pigments compared to static conditions where the pool remained the same or decreased. The recovery of DD in the dark or under low light was found to be significantly faster than in temperate algal communities. These results suggest that ice algae at the sea ice bottom can activate the photoprotective DD-cycle to regulate excess thermal energy. Unlike temperate species of diatoms, ice algae can rapidly reconstruct the pigment pool under low light or in the dark and is likely a particular adaptation to the unique light environment in Antarctica.     

Photophysiology and albedo-changing potential of the ice algal community on the surface of the Greenland ice sheet

Darkening of parts of the Greenland ice sheet surface during the summer months leads to reduced albedo and increased melting. Here we show that heavily pigmented, actively photosynthesising microalgae and cyanobacteria are present on the bare ice. We demonstrate the widespread abundance of green algae in the Zygnematophyceae on the ice sheet surface in Southwest Greenland. Photophysiological measurements (variable chlorophyll fluorescence) indicate that the ice algae likely use screening mechanisms to downregulate photosynthesis when exposed to high intensities of visible and ultraviolet radiation, rather than non-photochemical quenching or cell movement. Using imaging microspectrophotometry, we demonstrate that intact cells and filaments absorb light with characteristic spectral profiles across ultraviolet and visible wavelengths, whereas inorganic dust particles typical for these areas display little absorption. Our results indicate that the phototrophic community growing directly on the bare ice, through their photophysiology, most likely have an important role in changing albedo, and subsequently may impact melt rates on the ice sheet.     

Population dynamics of potentially harmful algal blooms in Bizerte Lagoon,Tunisia

The population dynamics of potentially harmful phytoplankton in the semi-closed, coastal Bizerte Lagoon, Tunisia, in the south-western Mediterranean, were examined from November 2007 to February 2009 at six sampling stations, three situated in areas of mussel and oyster farming. The harmful species monitored included the potential producers of amnesic shellfish poisoning (Pseudo-nitzschia spp.), paralytic shellfish poisoning (Alexandrium spp.), diarrheic shellfish poisoning (Dinophysis spp. and Prorocentrum spp.), ichthyotoxins (Cochlodinium polykrikoides, Akashiwo sanguinea and Karenia mikimotoi), yessotoxins (Gonyaulax spinifera) and the discolouration of water (Neoceratium lineatum and Protoperidinium sp.). These were numerically dominated by potentially toxic species of the diatom genus Pseudo-nitzschia, which were present year-round at all stations. Prorocentrum spp., Dinophysis spp. and Neoceratium lineatum were the most abundant and recurrent harmful dinoflagellates, exhibiting their highest densities at the shellfish farming stations. Alexandrium spp. bloomed only on one occasion, reaching its highest densities at a shellfish farming station. Canonical correspondence analyses revealed significant relationships between the harmful phytoplankton species monitored and the environmental conditions. The widespread distribution of harmful phytoplankton in Bizerte Lagoon, with the permanent presence of Pseudo-nitzschia spp. and the high frequency of dinoflagellate blooms in the shellfish areas, suggests a potential risk of shellfish poisoning events in the region.     

A physical study on the thermal ice ridge in a closed deep lake: Lake Kuttara, Hokkaido, Japan

An ice-ridge line more than 2,000 m long was discovered in a closed, deep lake—Lake Kuttara, Hokkaido, Japan—in the ice-covered season of 1995. To clarify when and how the ice-ridge line built up, meteorology and ice and water temperatures were monitored, and the density, thermal conductivity, and thickness of the covered ice were measured from January through March 1995. The covered ice on 4 and 5 March 1995, which corresponded to the period with the thickest lake ice, consisted of snow ice 0.05- to 0.07-m thick and candle ice 0.18- to 0.21-m thick. Numerical simulations for the ice thickness and temperature were carried out using a one-dimensional, unsteady, three-layer model. The simulated results, which were reasonable to the observations, indicate that due to the ice contraction and expansion, the ice-ridge line started to construct on 2 February and was completed the next day.     

Interrelation between plankton and benthos in the littoral algal community of Lake Yunoko,Central Japan

To ascertain the floristic interaction between phytoplankton and benthos in the littoral, the composition of each community was investigated and the effect of the substrata on the benthic communities was also examined.The main component of the benthic algal population wasFragilaria pinnata followed byF. pinnata var.lancettula. Although the dominant species of the plankton in the upper layers were similar to those in the limnetic, and those immediately above the bottom contained species of benthic origin, the similarity index of C implied high similarity between these two plankton layers. This index was developed by Morishita (1959) to measure the degree of overlap of component species between two communities. The value of C distributes from 0 to 1. The closer the value approaches 1, the more the communities are similar.For the dominant species, a significant difference was observed between the phytoplankton and benthic communities and in addition, C values indicated low overall similarity in the composition of the communities. These results suggest that there is little interrelation between phytoplankton and benthos even in the shallow littoral zone.     

The sea-ice algal community of seasonal pack ice in the southwestern Kara Sea in late winter

The composition and abundance of ice algae have been studied in a 64-cm core of seasonal pack ice taken in the southwestern Kara Sea in February 1996. The cell numbers, biomass and taxonomic diversity of the ice microalgal assemblages were rather low, and there was a predominance of diatoms. The comparison of its composition with that of the pelagic microalgal community demonstrated a great difference between them. The ecological function of the seasonal ice habitat as a depository for seeding material of the early-spring pelagic diatom is suggested. Accepted: 7 August 2000     

A new species of Haborophocoena, an Early Pliocene phocoenid cetacean from Hokkaido, Japan

A new species of phocoenid cetacean Haborophocoena , collected from the Early Pliocene Embetsu Formation, in the close vicinity to the site where the holotype of the type species of the genus Haborophocoena was retrieved, improves our knowledge of the anatomy of this cetacean. The new species, represented by a skull, lacking distal half of the rostrum, ear bones, and teeth, is significantly smaller than, but morphologically similar to, the type species Haborophocoena toyoshimai Ichishima and Kimura 2005 . This new record of Haborophocoena confirms the veracity of the genus Haborophocoena as a biological entity, contributes to understanding the interspecific variation, and suggests that the genus diversified in the northwestern Pacific of early Pliocene time. The adult-like degree of ossification in this small skull precludes it from being a juvenile of Haborophocoena toyoshimai . Autapomorphies of Haborophocoena minutus include narrow premaxilla on the dorsal surface of the rostrum, the anterior position of the premaxillary foramen, and a distinct ridge dividing a fossa on the lateral face of the base of the zygomatic process into the dorsal and the ventral halves, the zygomatic process rectangular in lateral profile, and its small size, which is the most compelling feature, making it a distinct species.     

Photoprotective response of xanthophyll pigments during phytoplankton blooms in Sagami Bay, Japan

The relationship between the xanthophyll pool [diadinoxanthinplus diatoxanthin normalized to chlorophyll (Chl) a] and irradiancewas examined during phytoplankton blooms in Sagami Bay fromthe end of April to July 2000. In the case of Chl a concentrations>2 mg m^-3, a linear correlation was found between the xanthophyllpool and irradiance of the previous day. On the other hand,for Chl a concentrations <2 mg m^-3, the xanthophyll poolremained low and was independent of irradiance of the previousday. The results may indicate that photoprotection by xanthophyllpigments assists the development of phytoplankton blooms underhigh-irradiance conditions.     

Biofilm, ice recrystallization inhibition and freeze-thaw protection in an epiphyte community

Microbial communities found on the surface of overwintering plants may be exposed to low temperatures as well as multiple freeze-thaw events. To explore the adaptive mechanisms of these epiphytes, with the objective of identifying products for freeze-protection, enrichment libraries were made from frost-exposed leaves. Of 15 identified bacteria from 60 individual clones, approximately half had ice-association activities, with the great majority showing high freeze-thaw resistance. Isolates with ice nucleation activity and ice recrystallization inhibition activity were recovered. Of the latter, two (Erwinia billingiae J10, and Sphingobacterium kitahiroshimense Y2) showed culture and electron microscopic evidence of motility and/or biofilm production. Mass spectrometric characterization of the E. billingiae extracellular polymeric substance (EPS) identified the major proteins as 35 kDa outer membrane protein A and F, supporting its biofilm character. The addition of the EPS preparation increased the freeze-thaw survival of the more susceptible bacteria 1000-10000 times, and protection was at least partially dependent on the protein component.     

Response of microbial community structure to natural and accelerated hydrarch successions in the boreal wetlands in northern Hokkaido, Japan

We estimated the effect of invading Sasa vegetation and accelerated terrestrialization on the microbial community structure in Sarobetsu-genya wetland (SGW) and Nakanominedaira wetland (NW) (original vegetation, Sphagnum). All examined peat-pore water samples were acidic. Electrical conductivity significantly differed between SGW and NW. Nonmetric multidimensional scaling (NMDS) and analysis of similarity based on denaturing gradient gel electrophoresis (DGGE) band patterns revealed differences in the bacterial community structure between the Sasa and Sphagnum vegetations at a depth of 10 cm in NW. In contrast, the bacterial NMDS profiles at all depths differed between the 2 wetlands rather than between the 2 vegetations. The archaeal community structure significantly differed between the wetlands at depths of 30 and 50 cm. The bacterial diversity index derived from the DGGE profiles significantly differed between the wetlands at all depths. The archaeal diversity index significantly differed between the wetlands at a depth of 50 cm. Sasa invasion affected the microbial community structure in the rhizosphere, up to a depth of 10 cm; this effect differed with the terrestrialization speed. These results suggest that in peat bogs subjected to artificially accelerated terrestrialization, the microbial community changes before the occurrence of the natural hydrarch ecological succession involving ground vegetation.     

Invertebrate community and stream substrate responses to woody debris removal from an ice storm-impacted stream system, NY USA

We assessed the influence of ice-storm-derived debris dams on aquatic macroinvertebrates and stream substrates in a high-gradient watershed in the eastern Adirondack Mountains of New York State. Using a modification of electrofishing techniques, invertebrates were collected once before (June 2000) and once after (June 2001) wood removal from the downstream reach in each of six pairs of reaches (second and third-order streams). Stream substrates were also mapped in 2000 and 2001 to evaluate shifts in dominant substrates within a reach following wood removal. The following metrics were used to compare the invertebrate communities before and after wood removal: genera similarity, Shannon–Weiner equitability, taxa richness, dominant taxon, percent dominance and functional feeding group relative abundance. The changes in removal reaches were evaluated relative to changes in upstream reference reaches using a Before-After Control-Impact (BACI) design and analysis. Stream substrates did not change significantly in response to wood removal, although a trend toward coarser substrates was observed following removal. Following wood removal, the relative proportion of grazers increased upstream and downstream from removed dams in all streams; however, comparisons of other metrics indicated no significant response to removal. Invertebrate responses to wood removal were lower than expected, perhaps due to the presence of abundant boulder-formed pools in this high gradient system. Electronic supplementary material Electronic supplementary material is available for this article at and accessible for authorised users.     

Multivariate geometry as an approach to algal community analysis

Multivariate analyses are put in the context of more usual approaches to phycological investigations. The intuitive common-sense involved in methods of ordination, classification and discrimination are emphasised by simple geometric accounts which avoid jargon and matrix algebra. Warnings are given that artifacts result from technique abuses by the naive or over-enthusiastic. An analysis of a simple periphyton data set is presented as an example of the approach. Suggestions are made as to situations in phycological investigations, where the techniques could be appropriate. The discipline is reprimanded for its neglect of the multivariate approach.     

日本北海道地区细石叶技术研究概述

细石叶技术是晚更新世晚期东北亚和西北美新的变革性剥坯技术和适应手段。北海道地区拥有丰富、多样的细石器遗存,相关材料最早可以追溯到距今约2.5万年前,持续了约1.2万年。以北海道具有明显技术复杂性和多样性特点的细石器为材料,学者们基于技术式"阅读"和拼合研究划分出一系列细石核工艺类型和剥坯技法;岛内以楔形细石核为代表的细石器工业传统在不断延续的同时,也表现出明显的阶段性变化,并在一定程度上显示出与气候环境变化较强的相关性。本文对北海道地区晚更新世末次盛冰期以来的气候、环境背景以及细石器的发现与研究历程进行介绍。在此基础上,厘清北海道细石核工艺类型的划分,并对细石器群的阶段性演变进行系统梳理,以期对我国相关研究有所裨益。     

The population dynamics of the voleClethrionomys rufocanus in Hokkaido, Japan

Population dynamics of the gray sided-vole,Clethrionomys rufocanus, in Hokkaido, Japan were described on the basis of 225 time series (being from 12 to 31 years long); 194 of the time series have a length of 23 years or longer. The time series were classified into 11 groups according to geographic proximity and topographic characteristics of the island of Hokkaido. Mean abundance varied among populations from 1.07 to 21.07 individuals per 150 trap-nights. The index of variability for population fluctuation (s-index) ranged from 0.204 to 0.629. Another index for population variability (amplitude on log-10 scale) ranged from 0.811 to 2.743. Mean abundance and variability of populations were higher in the more northern and eastern regions of the island. Most populations, except for the southernmost populations, exhibited significant direct density-dependence in population growth. Detection rate for delayed density-dependence varied among groups from 0% to 22.6%. Both direct and delayed density-dependence tended to be stronger in the more northern and eastern populations. The proportion of cyclic populations was higher in the northern-eastern areas than that in the southern-western areas. There was a clear gradient from the asynchronous populations in southwest, to the highly synchronized populations in the northeast.