Net photosynthetic rate and leaf life span were measured in six submerged plants, Potamogeton crispus L., P. malaianus Miq., Cabomba caroliniana A. Gray, Hydrilla verticillata (L. f.) Royle, Egeria densa Planch., and Elodea nuttallii (Planch.) St. John, growing in a nutrient-rich experimental pond. A negative correlation between net photosynthetic rate and leaf life span is observed among submerged and floating-leaved plant species as well as for trees among diverse terrestrial ecosystems. Differences in net photosynthetic rate and leaf life span of the submerged plants should be related to differences in the light condition of habitats and life history strategy.
Primary productivity of epiphytic and planktonic algae and their biogeochemical characteristics in five shallow littoral reed zones showing a different trophic character in Lake Biwa were investigated. Concentrations of nutrients and dissolved organic matter varied widely horizontally, locally and seasonally in the reed zones. It seems that the reed zone has a heterogeneous environment. The photosynthetic rates of epiphytic and planktonic algae were, respectively, 0.2 to 5.7 mg C surface shoot area m-2 hr-1 and 4 to 70 mg C m-3 hr-1. The areal primary productivity of epiphytic algae was estimated as 0.3 to 9.7 mg C m-2 hr-1 in summer and 0.4 to 3.1 mg C m-2 hr-1 in winter from the shoot density of Phragmites and the water depth in each reed zone. The productivity of phytoplankton, on the other hand, was 3 to 56 mgC m-2 hr-1 in summer and 1 to 12 mgC m-2 hr-1 in winter. The contribution of epiphytic algae to total primary productivity averaged 15 %, although the assimilation number was much lower than that of phytoplankton. The present study indicates that epiphytic algae are one of the significant primary producers in reed zone.
Quantitative observations on the seasonal changes in leaf life span, leaf. area and leaf mass of a floating-leaved aquatic macrophyte, Brasenia schreberi J. F. Gmel., were carried out from 1986 to 1988 in an irrigation pond in Matsue, Shimane Prefecture, Japan, using a non-destructive leaf-marking method. During those three years, the seasonal maximum leaf area index, seasonal maximum leaf mass, and annual net production changed considerably ; 0.90-1.36, 52.5-80.5g dry weight m-2 and 154.9-243.5 g dry weight m-2 yr-1, respectively.In contrast, the annual mean life span, turnover of leaves in number, and the annual net production to seasonal maximum biomass ratio (P/Bmax ratio) were relatively constant around the values of 25-28 d, 6.0-6.3 and 2.95-3.25 yr-1, respectively. While the net production (P<0.05) and leaf mass (P<0.005) of leaves had a significant linear relation to cumulative sunshine duration from 1 May to late September, there was no significant correlation between cumulative temperature and annual net production and leaf mass. Present result suggests that sunshine duration during the growing season is crucial for the leaf production of B. schreberi.
Gas emission rates from the submerged soil surface in Zizania latifolia-planted pots were higher than those from unvegetated pots and increased with increasing biomass. The oxygen supply from the atmosphere through the plants to the soil had presumably activated nitrate production by nitrification in oxic soils, and the nitrate had accelerated denitrification in adjacent anoxic soils. In contrast to the results for Z. latifolia, gas emission rates from soil in Phragmites australis-planted pots were lower than those from unvegetated pots. Gas generated in soils could be carried to the atmosphere through the ventilation pathway in the plant body rather than through the soil by diffusion and via the overlying water as air bubbles.
The characteristics of taxis in Peridinium bipes were examined using an experimental tank and a coupled microscope-CCD camera system. The vegetative cells exhibited negative geotaxis, since they swam upward irrespective of upward or downward irradiance. This behavior appeared to be the main factor in controlling the vertical migration of this species. The negative geotaxis was inferred to be caused by the distance between the center of gravity and the geometric center of the cell. We also estimated the geotactic and phototactic vertical swimming velocity of P. bipes and simulated the vertical migration of a P. bipes community with a numerical model. The model accurately reproduced the observed vertical migration pattern of the P. bipes community at irradiances over the range of 0 to 80.5μmol quanta m-2 sec-1. This model, in combination with a hydrodynamic model and a water quality model, will play a useful role in elucidating the appearance of freshwater red tides caused by P. bipes.
The males, females, larvae and larval cases of Goerodes albicornis (BANKS, 1906) n. comb. and Goerodes kasugaersis (TANI, 1971) n. comb. are described. Male, larva and larval case of G. albicornis and female, larva and larval case of G. kasugaensis are described for the first time. Goerodes nukabiraensis (KOBAYASHI, 1964) is synonymized with G. speculifer (MATSUMURA, 1907). The males, females, larvae and larval cases of Goerodes iriomotensis n. sp. are described from Iriomote Island, in the southernmost part of Japan. They had been erroneously recorded under the name of G. arcuatus HWANG, 1957.
In an upper shallow reach of the Ishite River, the stream water is completely diverted at a weir except under flood conditions, and is regenerated below the weir by groundwater. A 13-year monthly survey was undertaken 2.4 km below the weir between 10 : 00 and 14 : 00 from 1985 to 1997. The difference between observed DO minus saturated DO concentrations (ΔDO), not DO itself, correlated positively with pH among 110 samples under baseflow conditions (r=0.585, P<0.001). A diel survey also showed the parallel change in ΔDO and pH. Four surveys at 10 : 00 and 22 : 00 near the weir showed that ΔDO and pH were little changed between day and night. They increased at 2.4 km below the weir, especially in the daytime. ΔDO and pH seemed to increase all day long by an exchange of oxygen and carbon dioxide between the stream and the air, and additionally by photosynthesis in the daytime. An additional eight surveys at 22 : 00 2.4 km below the weir showed that ΔDO in the nighttime distributed within a narrow range having a mean of -1.26 mg l-1. The surplus ΔDO above this mean in the daytime is available as an index of photosynthesis in the stream. A recent 4-year monthly observation of biofilms on the stream bed containing algae and measurements of photons in the stream water showed that ΔDO was controlled by both the number of photons and the amount of biofilms.
This third in a series of checklists of Japanese Trichoptera deals with 1 species of Limnocentropodidae, 2 species (1 genus) of Phryganopsychidae, 15 species (6 genera) of Phryganeidae, 15 species (3 genera) of Brachycentridae and 20 species (4 genera) of Apataniidae. We recogneized Apatania momoyaensis KOBAYASHI and Moropsyche higoana KOBAYASHI as valid names from original descriptions. In Phryganeidae, we suggest three taxonomic problems: 1) the larva of an unnamed 'species' of Agrypnia is not identifiable as species ; 2) the description of Oligotricha kawamurai (IWATA) was based only on the larval stage and is insufficient for specific identification ; 3) it should be confirmed whether Neuronia maxima (IWATA) is a junior synonym of Eubasilissa regina (MCLACHLAN) or that of Semblis melaleuca (MCLACHLAN). In Brachycentridae, five taxonomic problems remain : 1) since Brachycentrus japonicus (IWATA) and three 'species' of Brachycentrus or Micrasema separated with tentative alphabetic designations were described only from larval specimens, the associations of their larval and adult stages should be established ; 2) description of Eobrachycentrus oharensis (IWATA) described only larva, which is insufficient for species identification ; 3) the description of Eobrachycentrus kitayamanus (TSUDA) is insufficient to confirm the species ; 4) a 'species' of Micrasema with a tentative alphabetic designation recorded from Honshu has not yet been provided a specific name, although male genitalia were illustrated ; 5) a few 'species' of Micrasema recorded from Honshu are not identifiable as species ; 6) some undescribed species have been collected in Japan. In Apataniidae, two taxonomic problems remain : 1) the larvae of two 'species' of Apatania and Moropsyche with tentative alphabetic designations and two unnamed 'species' of Apatania are not identifiable as species ; 2) many undescribed species have been collected in Japan.
The first record of depth-time profiles for some physicochemical and biological parameters of Lake Bishamon-numa based on periodic observations during the ice-free season of 1996 are reported. Throughout the observed period, the thermocline was either absent or very weak. In accordance with this structure of water temperature, the dissolved oxygen was distributed uniformly in the water column at above a 90 % saturation level. The average and standard deviation of transparency was 5.1 ± 1.1 m. On the assumption that the trophogenic zone is from the surface to a depth of twice the transparency, the whole water body of the east basin in which the sampling station is located, constitutes the trophogenic zone. pH was fairly constant from July to December with an average and standard deviation of 6.2±0.1. Compared with past data, the pH of Lake Bishamon-numa has changed greatly within a relatively short time period in the past and has lately stabilized around pH 6. The concentrations of Na, K, Mg, and Ca were in the order of m mol 1-1, while those of Fe and Mn were of umol 1-1. Ranked in descending order of concentrations, they are Na, Ca, Mg, K, Mn and Fe. The annual maximum of Chl. a was 1.5 μg 1-1 in May. Though there were slight maxima and minima, the Chl. a concentration was below 1μg 1-1 in most seasons and averaged 0.51μg 1-1. This Chl. a level corresponds to those of other oligotrophic lakes. Nanophytoplankton ranging from 2 to 20 μm predominated, and macrophytoplankton greater than 20 μm were relatively scarce.
We analyzed esterase isozymes of larvae described as Hydropsychodes sp. HA (CHINO, 1975) and adults of Cheumatopsyche galloisi (MATSUMURA, 1931). The esterase patterns of the larvae were coincident with those of the adults and different from those of other Cheumatopsyche species from Honshu. Thus, we confirmed the larvae of C. galloisi as Hydropsychodes sp. HA. This simple method provides a useful tool to associate the larval and adult stages of Trichoptera.
We compared benthic insect assemblages among three reaches with different riparian conditions (forest, transitional, and grassland) in a small stream flowing through forest to grassland in northern Hokkaido, Japan. Total density was significantly higher in the transitional and the grassland reaches than in the forest reach in both summer and fall. The number of taxa was significantly higher in the transitional and the grassland reaches than in the forest reach in summer. The density of shredders was significantly higher in the forest and the transitional reaches than in the grassland reach in fall. On the other hand, the density of collector-gatherers, collector-filterers, and predators were significantly higher in the transitional and the grassland reaches than in the forest reach in both summer and fall. The distribution of benthic assemblage types classified by a cluster analysis also corresponded to the three riparian types.