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[Aim] / Natural disaster risk reduction (DRR) is becoming a more important function of protected area (PAs) for current and future global warming. However, biodiversity conservation and DRR have been handled separately and their interrelationship has not been explicitly addressed. This is mainly because, due of prevailing strategies and criteria for PA placement, a large proportion of PAs are currently located far from human-occupied areas, and habitats in human-occupied areas have been largely ignored as potential sites for conservation despite their high biodiversity. If intensely developed lowland areas with high flooding risk overlap with important sites for biodiversity conservation, it would be reasonable to try to harmonize biodiversity conservation and human development in human-inhabited lowland areas. Here, we examined whether extant PAs can conserve macroinvertebrate and freshwater fish biodiversity and whether human-inhabited lowland flood risk management sites might be suitable to designate as freshwater protected areas (FPAs). / [Location] / Across Japan. / [Methods] / We examined whether extant PAs can conserve macroinvertebrate and freshwater fish biodiversity and analysed the relationship between candidate sites for new FPAs and flood disaster risk and land use intensity at a national scale across Japan based on distribution data for 131 freshwater fish species and 1395 macroinvertebrate species. / [Results] / We found that extant PAs overlapped with approximately 30% of conservation-priority grid cells (1 km^2) for both taxa. Particularly for red-listed species, only one species of freshwater fish and three species of macroinvertebrate achieved the representation target within extant PAs. Moreover, more than 40% of candidate conservation-priority grid cells were located in flood risk and human-occupied areas for both taxa. / [Main conclusions] / Floodplain conservation provides suitable habitat for many freshwater organisms and helps control floodwaters, so establishing new FPAs in areas with high flood risk could be a win-win strategy for conserving freshwater biodiversity and enhancing ecosystem-based DRR (eco-DRR).

Climate change is causing frequent and large floods, creating a need for information regarding the impact of severe flood disturbances on stream invertebrates. We briefly describe the response of invertebrate assemblages to an extreme flood event in 2018 in the western Ehime Prefecture of Japan. We compared invertebrate data collected in past regional-scale surveys with those gathered by revisiting 27 study sites after the flood and examined the relationship between catchment characteristics and the invertebrate response across the study area. Heavy rainfall was recorded in the catchment of each study site during the flood (range 565–1081 mm). Stream invertebrates may be eliminated by the historical flood, although the degree was small compared with that in previous reports on the effects of severe flood disturbances (abundance − 19.1%, taxon richness − 9.0%), likely owing to the absence of severe bed disturbance. Our results imply that high primary productivity, possibly caused by low elevations and the development of farms, accelerated the recovery of invertebrates after the disturbance. They also suggest that assembling pre-disturbance data is the key to understanding the impact of extreme floods on stream invertebrates and managing stream ecosystems during climate change.

Microbes play a critical role in plant litter decomposition and influence the fate of carbon in rivers and riparian zones. When decomposing low-nutrient plant litter, microbes acquire nitrogen (N) and phosphorus (P) from the environment (i.e., nutrient immobilization), and this process is potentially sensitive to nutrient loading and changing climate. Nonetheless, environmental controls on immobilization are poorly understood because rates are also influenced by plant litter chemistry, which is coupled to the same environmental factors. Here we used a standardized, low-nutrient organic matter substrate (cotton strips) to quantify nutrient immobilization at 100 paired stream and riparian sites representing 11 biomes worldwide. Immobilization rates varied by three orders of magnitude, were greater in rivers than riparian zones, and were strongly correlated to decomposition rates. In rivers, P immobilization rates were controlled by surface water phosphate concentrations, but N immobilization rates were not related to inorganic N. The N:P of immobilized nutrients was tightly constrained to a molar ratio of 10:1 despite wide variation in surface water N:P. Immobilization rates were temperature-dependent in riparian zones but not related to temperature in rivers. However, in rivers nutrient supply ultimately controlled whether microbes could achieve the maximum expected decomposition rate at a given temperature. Collectively, we demonstrated that exogenous nutrient supply and immobilization are critical control points for decomposition of organic matter. Key Points • Nitrogen (N) and phosphorus (P) immobilization was measured on organic matter (cotton) in 100 rivers and riparian zones representing 11 biomes • Elevated temperature in riparian zones and phosphate in rivers increased immobilization, and consequently accelerated decomposition • N and P immobilization was strongly linked by microbial stoichiometry despite widely varied surface-water nutrient ratios Plain Language Summary Bacteria and fungi contribute to the breakdown of leaf litter in rivers and floodplains. To break down leaf litter, these microbes need the nutrients nitrogen and phosphorus (P), and microbes can get nutrients either from the leaf litter itself or from the environment. Most leaf litter has low nutrient content and microbes must rely on the environment to supply nutrients. We studied microbial nutrient uptake from the environment during litter breakdown to determine whether it varies predictably across the globe and how it is influenced by changing climate and nutrient pollution. In 100 rivers and floodplains in 11 of Earth's major biomes we placed small strips of cotton as stand-ins for leaf litter. Nutrient uptake was consistently greater on cotton strips that were submerged in the river compared to cotton on the floodplain. For microbes in the river, nutrient uptake was faster in instances where there was more P in the water. For microbes in the floodplain, nutrient uptake was faster where temperatures were warmer. Faster nutrient uptake by microbes was linked with faster cotton breakdown in rivers and floodplains. Our study shows that climate change and nutrient pollution can alter the activity of microbes in rivers and floodplains.

Similar species that overlap in sympatry may diverge in characters related to resource use as a result of evolution or phenotypic plasticity. Dolly Varden charr (Salvelinus malma) and whitespotted charr (S. leucomaenis) overlap along streams in Hokkaido, Japan, and compete by interference for invertebrate drift-foraging positions. Previous research has shown that as drift declines during summer, Dolly Varden shift foraging modes to capture benthic prey, a behaviour facilitated by their subterminal jaw morphology. We compare body and jaw morphology of Dolly Varden in sympatry vs. allopatry in two locations to test for character displacement. Statistical analysis showed significant divergence in characters related to foraging, which was correlated with variation in individual charr diets. Dolly Varden in sympatry had shorter heads and lower jaws than in allopatry, and even within sites charr with these characteristics fed less on drifting terrestrial invertebrates but more on benthic aquatic invertebrates. Those in allopatry had longer heads and lower jaws, and fed more on terrestrial invertebrates. The close proximity of sites in one stream suggests that Dolly Varden may display phenotypic plasticity similar to other charr, allowing rapid responses in morphology to the presence of competitors. These morphological shifts probably help them maintain positive fitness when competing with whitespotted charr in Hokkaido streams.

Networks of direct and indirect biotic interactions underpin the complex dynamics and stability of ecological systems, yet experimental and theoretical studies often yield conflicting evidence regarding the direction (positive or negative) or magnitude of these interactions. We revisited pioneering data sets collected at the deciduous forested Horonai Stream and conducted ecosystem-level syntheses to demonstrate that the direction of direct and indirect interactions can change depending on the timescale of observation. Prior experimental studies showed that terrestrial prey that enter the stream from the adjacent forest caused positive indirect effects on aquatic invertebrates during summer by diverting fish consumption. Seasonal and annual estimates of secondary production and organic matter flows along food web pathways demonstrate that this seasonal input of terrestrial invertebrate prey increases production of certain fish species, reversing the indirect effect on aquatic invertebrates from positive at the seasonal timescale to negative at the annual timescale. Even though terrestrial invertebrate prey contributed 54% of the annual organic matter flux to fishes, primarily during summer, fish still consumed 98% of the aquatic invertebrate annual production, leading to top-down control that is not revealed in short-term experiments and demonstrating that aquatic prey may be a limiting resource for fishes. Changes in the direction or magnitude of interactions may be a key factor creating nonlinear or stabilizing feedbacks in complex systems, and these dynamics can be revealed by merging experimental and comparative approaches at different scales.

Vertical hydrological connectivity between the surface stream and benthic and hyporheic zones plays a key ecological role in the biodiversity of lotic ecosystems because it allows surface and benthic organisms to use the hyporheic zone as a seasonal habitat and refuge. Use of the hyporheic zone by surface/benthic organisms has been well studied in invertebrates, but little is known about the importance of this connectivity for fishes. We investigated streambed surface and hyporheic densities (5–10, 15–20 and 20–25 cm below the streambed surface) of a stream fish, Cobitis shikokuensis, over a 20-month period in the Shigenobu River, southwestern Japan, to test the hypothesis that it uses the hyporheic zone for spawning and overwintering. In total, 1,804 individuals (13–58 mm total length) were captured from 33 streambed surface samplings and 102 individuals (10–46 mm total length) were present in 1,147 samples of 57 hyporheic samplings. Population densities in both zones peaked in late summer–early autumn due to the recruitment of age 0+ fish and a female with eggs was found in the hyporheic zone during the reproductive season. Both 0+ and older fish were absent from the streambed surface during winter, and fish densities were also lower in the hyporheic zone at this time. However, the vertical distribution of the fish tended to be skewed towards the deeper hyporheic layers from autumn to spring. These findings indicate that C. shikokuensis vertically migrates between the streambed surface and the hyporheic zone for spawning, rearing and overwintering, suggesting that the integrity of vertical hydrological connectivity in lotic systems is crucial for certain fish species.

Conventional morphology-based identification is commonly used for routine assessment of freshwater ecosystems. However, cost and time efficient techniques such as high-throughput sequencing (HTS) based approaches may resolve the constraints encountered in conducting morphology-based surveys. Here, we characterized stream macroinvertebrate species diversity and community composition via metabarcoding and morphological analysis from environmental samples collected from the Shigenobu River Basin in Ehime Prefecture, Japan. We compared diversity metrics and assessed both approaches’ ability to evaluate the relationship between macroinvertebrate community and environmental variables. In total, we morphologically identified 45 taxa (3 families, six subfamilies, 31 genera, and five species) from 8,276 collected individuals from ten study sites. We detected 44 species by metabarcoding, with 35 species collapsed into 11 groups matching the morphologically identified taxa. A significant positive correlation between logged depth (number of HTS reads) and abundance of morphological taxa was observed, which implied that quantitative data could be used for subsequent analyses. We recovered a considerably high rate of relative abundance detection of the morphologically identified samples. Recovery of samples by incidence or presence/absence count were considerably low, with a high rate of false-negative detection specifically for species with scarce representation in the community sample. Given the low taxonomic resolution of the morphological assignment in this study, we report that metabarcoding does not reflect the majority of the species naturally occurring in our site, which could further be proven by performing refined morphological assessment of the samples. However, abundance-based detection proved to be efficient with 92% of the individuals correctly demonstrated. We conclude that DNA metabarcoding provides a practical and cost-effective approach especially for rapid biological monitoring of freshwater macroinvertebrate communities, but further improvements in the detection of scarce samples should be considered to increase the sensitivity of detecting most, if not all, of the species present in the environment.

In lotic systems, the hyporheic zone has been suggested as a potential refuge for aquatic organisms during disturbances (hyporheic refuge hypothesis). However, the supporting evidence is unclear, especially regarding the survival of hyporheic refugees and their contribution to the recovery of post-disturbance populations. Moreover, few studies have focused on the importance of the hyporheic refuge for aquatic vertebrates such as fish. In this study, we present evidence that the hyporheic zone acts as a refuge for a small benthic fish (Cobitis shikokuensis) following surface drying in an intermittent river. We examined its survival during and recolonization after dry periods by direct hyporheic sampling and mark-and-recapture surveys. When the streambed dried, hyporheic sampling was conducted 58 times across 33 locations in the intermittent reach and 31 individuals of C. shikokuensis were captured from extracted hyporheic water. Mark-and-recapture surveys revealed that recolonizers after re-wetting included C. shikokuensis individuals that had survived dry periods in the hyporheic refuge. The condition factor of C. shikokuensis significantly declined after dry periods, suggesting that most recolonizers suffered from physiological stress, probably within the hyporheic refuge. These results clearly support the long-debated, hyporheic refuge hypothesis, and provide a striking example of the critical role of the hyporheic zone in population maintenance of lotic organisms.

Our objective was to evaluate the effects of dam construction on the substrate and stream invertebrate assemblages below dams. Few studies have directly measured both substrate characteristics and stream invertebrate assemblages in stream reaches above and below dams. We measured a range of habitat characteristics and collected samples of stream invertebrates in the reaches above and below a series of water storage dams in three river systems. The invertebrate assemblages in the reaches downstream of the storage dams were significantly different from those in the upstream reaches. The downstream sites were grouped in the domain in which the values for the second axis of the non-metric multidimensional scaling (NMS) were high. This difference was associated with changes in the characteristics of the substrate below the dams. Stone embeddedness and the frequency of stone movement were higher in the upstream reaches than in the downstream reaches (two-way ANOVAs). Stone embeddedness and stone movement were also negatively correlated with the NMS axis 2. Our results suggest that the condition of the substrate is an important determinant of the invertebrate assemblages up and downstream of dams. Given this, we believe that it is important to measure substrate characteristics when evaluating the effect of storage dams on stream ecosystems.

In headwater streams, conifer plantation forestry may affect stream communities through the quantity and quality of basal resources (allochthonous litter). We compared (1) the seasonal patterns of litter input from the riparian canopy, (2) those for the abundance of benthic and drifting litter in streams, and (3) the density of litter-associated invertebrates among streams bordered by deciduous broadleaved forest, a plantation of Japanese cedar (Cryptomeria japonica), and a clear-cut site, to extract the characteristics of conifer-plantation streams in terms of litter dynamics and benthic invertebrates. The results illustrate differences in litter input and in-stream processes between the broadleaved and plantation sites, although the total annual inputs from canopy were similar. In the broadleaved site, high litter storage was limited to winter, probably because pulsed inputs of litter in autumn were retained on the streambed but rapidly processed. In contrast, litter input was more constant at the plantation site, and litter was stored throughout the year. Although the litter-patch-specific density of total invertebrates was similar between the broadleaved and plantation sites, estimates of the reach-scale, habitat-weighted density considering differences in the coverage area of litter patches revealed considerable differences. Although the habitat-weighted density of total invertebrates was lower at the plantation site than at the broadleaved site in winter, it was noticeably higher at the plantation site in summer, owing to the seasonal stability of benthic litter abundance. Our results emphasized the importance of considering the spatiotemporal availability of benthic litter when assessing the effects of conifer plantations on stream ecosystems.

Summary 1. The light : nutrient hypothesis (LNH) proposes that herbivore growth rates are maximised at intermediate light-to-nutrient ratios. A reduction to light intensity (i.e. decreased light-to-nutrient ratio) should lead to reduced food availability for herbivores while excessive light intensity in oligotrophic environments (i.e. increased light-to-nutrient ratios) should increase the C : N and C : P ratios of producers. However, this hypothesis has not yet been supported by studies on stream ecosystems. 2. We tested the LNH by experimental application of controlled natural gradients in light intensity to oligotrophic laboratory channels that included periphyton and the freshwater snail Gyraulus chinensis. 3. The results in this oligotrophic environment indicate that light regulated the flow of matter between trophic levels and grazer reproduction by controlling C : P ratios of the producers.

We examined habitat factors related to the distribution and abundance of the spinous loach Cobitis shikokuensis, an endangered benthic fish, in the Shigenobu River system, southwestern Japan. In the study river, the spinous loach was distributed widely along the main stem, from headwater to near the mouth, whereas it was rarely found in tributary streams. Classification tree analysis showed that the presence/absence of spinous loach was explained by a combination of percent pebble and length of river fragment between artificial barriers. Spinous loach incidence was high in sites with abundant pebble (>27.7%), but low in sites with short river fragment (≤0.97 km) even if pebbles were abundant. A regression tree model for loach density retained only percent pebble as a single best predictor, with sites with higher percent pebble (>40.4%) having higher density. These results suggest that substrate condition is an important factor determining the distribution and abundance of spinous loach and also that habitat fragmentation by artificial barriers has great potential to threaten the spinous loach population in this river. Considering the highly fragmented situation of the study river and prevention of upstream migration by barriers, we conclude that maintenance of suitable habitats in upper reaches has high priority for conservation of the spinous loach.

Relationships between weight (W; dry weight) and length (L; head capsule width, total body length or head carapace length) were examined in 31 Japanese freshwater macroinvertebrate taxa, using the form W = aL b . The relationships were expressed as data of the lowest taxonomic level and data of higher taxonomic levels. The length–weight relationships obtained in this study were similar to those obtained in North America and Europe at the lowest taxonomic level, whereas they could be different from those obtained in North America and Europe at the higher taxonomic levels. We suggest that researchers should make their own regressions for a target taxon or use the regression for the same taxon as possible lower taxonomic level in the local area.

渇水にともなう瀬切れの発生は河川の連続性を遮断し, 河川生態系に影響を及ぼすことが危惧されている. 本研究では, 人間の影響で瀬切れが拡大・長期化している愛媛県重信川で, 河川環境および河川性底生動物の流程に沿った変化を調査し, 瀬切れが底生動物に及ぼす影響を解明することを目的とした. その結果, 瀬切れは水質には影響を及ぼしたが, 底生動物に及ぼす影響は明瞭には見られなかった. また, 下流域の人間による土地利用が河川の水質を改変し, 底生動物の流程に沿った変化に強い影響を及ぼすことが示された.

瀬切れによる河川の連続性の遮断は, 河川生物の流程に沿った移動を阻害し, それらの群集構造を改変すると予想される. そこで本研究は, 人為的な要因により発生している瀬切れ区間の上流-下流間で, 河川生物群集の比較を行い, 瀬切れが河川生物の空間的分布に及ぼす影響を明らかにすることを目的とした. この結果, 瀬切れが魚類の分布に及ぼす影響は明瞭ではなかった. 一方, 底生動物の分類群の一部は瀬切れによる影響を受けている可能性があることが示唆された. しかし, 底生動物に関しては, 瀬切れの発生に関わらず, 生息場所環境が群集構造を決定している可能性が考えられた.

We conducted a field experiment to reveal the effects of frequent streambed disturbance on the diversity of stream invertebrates in a local habitat patch in a Japanese stream. We used wire mesh baskets as experimental substrata and manipulated five levels of disturbance frequency (every 2, 4, 8, 16 or 32 days) in order to describe the pattern of the diversity of the stream invertebrates under different disturbance frequency and to explore possible factors generating the pattern. The total abundance and taxon richness recovered during 8-day and 2-day periods between each experimental disturbance, respectively, indicating that the stream invertebrates were highly resilient to disturbance due to their high mobility. The evenness of the invertebrate community was high in streambed patches with frequent disturbance. Patterns of the absolute abundance among the different disturbance frequency treatments differed substantially among nine common taxa. The absolute abundance of the most common taxon, Chironominae, was low in streambed patches where the disturbance frequency was high and intermediate, suggesting their low colonizing ability owing to their low mobility, compared with other common taxa. These results suggested that the diversity, in terms of evenness, of stream invertebrates in a local habitat patch is maintained by frequent streambed disturbance when the most common taxon has low colonizing ability. Our study demonstrated that differences in colonizing ability, caused by different mobilities, among community members may have a prominent importance when investigating the relationships between disturbance frequency and the diversity of organisms that have high mobility and actively colonize an opened patch.

A field experiment was conducted using ceramic plates as experimental substrates to describe the colonizing pattern of a stream invertebrate community after disturbance, and to ascertain the importance of colonizing ability for succession in a Japanese stream. We employed the simultaneous removal design in which plates were periodically set in place (1, 2, 4, 8, 16 and 32 days before sampling) and all plates were sampled on the last day of the experiment, to diminish the influence of seasonal change in stream invertebrates. Total abundance and taxon richness reached a plateau after 4‐ 16 days of colonization. In contrast, the relative abundance of six common taxa and community structure changed throughout the 32 days of colonization. Differences in the colonizing ability of the stream invertebrates were evident. Taxa with high mobility, such as the mayflies Baetis thermicus , Paraleptophlebia japonica , Cinygmula sp. and Drunella sachalinensis , colonized faster than those with low mobility (e.g. the caddisfly species Brachycentrus americanus and the chironomid midge Diamesinae spp.). The abundance of the most common taxon, Baetis , decreased at late stages of colonization, possibly because of low periphyton biomass. Consequently, we concluded that a difference in colonization ability among taxa is an important factor causing succession in stream invertebrate communities in local habitats.

1. The effects of substratum stability on the diversity of stream invertebrates were assessed at two spatial scales in a Japanese stream during baseflow, from May to June 1998. Deposition and erosion were examined separately as distinct elements of substratum stability by a newly developed method using small steel pins. Stream invertebrates were sampled after 28 days of measurement of substratum stability. We also measured physical environmental variables, current velocity and depth, and food resource parameters including periphyton and particulate organic matter (POM) standing crops. 2. At the scale of the habitat patch, the effects of substratum stability on invertebrates were overwhelmed by those of POM standing crop. Moreover, higher taxon richness at high abundance may simply result from a higher likelihood of more taxa being included in samples. Therefore, this small scale revealed no role for substratum stability in explaining spatial pattern of community diversity. 3. At the reach scale (n=10), taxon richness and evenness peaked at an intermediate level of deposition, whereas invertebrate abundance did not show any significant relationship. This result, and the pattern of relative abundance of common taxa, implies that the diversity of stream invertebrates was determined by subtle substratum movements and by the habitat preference of each taxon. 4. The difference in the determinant of community parameters between the habitat patch and the reach affirm the importance of a cross-scale analysis to choose an appropriate spatial scale for investigating the community structure of stream invertebrates. Prominent effects of substratum stability, particularly the deposition of substratum particles, during baseflow suggest that subtle and constant movement of small substratum particles can contribute to determine the diversity of stream invertebrates.

When evaluating forest functions and their responses to climate change, it is important to clarify carbon dynamics in forested basins. Carbon fluxes in litter fall, throughfall, soil solution, groundwater and stream water were determined from November 1997 to October 1998 for a forest stream ecosystem in a cool-temperate forested basin in the Tomakomai Experimental Forest, Hokkaido University, northern Japan. The annual carbon input to the stream by litter fall was 0.23 gC m -2 year -1 , with the greatest flux in the autumn. Owing to biological decomposition of litter in the stream, the carbon concentration in stream particulate organic matter (>0.45 μm) decreased as particle size decreased. The upstream carbon flux was 1-9 gC m - year - and the annual carbon output in stream water was 7.6 gC m 2 year -1 , mainly as dissolved inorganic carbon (DIC), resulting in net carbon output in stream water of 5.7 gC m -2 year -1 . The mean dissolved organic carbon (DOC) concentration in soil solution was higher than that in throughfall and stream water. The estimated annual carbon flux from soil in deep (about 1.5 m) soil solution was 4.4 gC m -2 year -1 . About 40% of DOC in soil solution was decomposed and converted to DIC in groundwater. These results indicate that carbon dynamics in the forest stream were affected strongly by decomposition of organic matter in the soil-groundwater-stream continuum and by the hydraulic conditions, which are characterized by a large pool of groundwater and high soil permeability.

Spawning redd superimposition of introduced, spring-spawning rainbow trout,Oncorhynchus mykiss, on native, fall-spawning Dolly varden,Salvelinus malma, and white-spotted charr,S. leucomaenis, were examined in a small stream in Hokkaido, Japan. The stream reaches in which Dolly Varden and white-sported charr redds were observed in fall 1997 greatly overlapped with the reaches in which rainbow trout redds were recorded in spring 1998. Spawning microhabitats were also similar between trout and the two charr species. Thirteen and 3% of Dolly Varden and white-spotted charr redds, respectively, were superimposed by rainbow trout redds. The eggs or alevins in the disturbed charr redds were potentially damaged because charrs were not likely to have emerged from the redds before the superimposition occurred. In sufficiently great abundance, introduced rainbow trout may negatively impact native charr populations by dislodging the latter’s spawning redds.

During exercise blood pressure fluctuates from minute to minute and does not rise linearly with time. Blood pressure responses were evaluated during exercise by a logistic function curve. Thirty-nine hypertensive patients underwent exercise testing with an ergometer, employing a multistage method (25 watts increment, every 3 min). We plotted the exercise duration on the X-coordinate and systolic blood pressure on the Y-coordinate and blood pressure was assumed to form a logistic curve for exercise duration. The relationship of systolic blood pressure vs. exercise duration was better fitted into a logistic function curve than a linear regression model. The logistic curve was defined by lower plateau, upper plateau, SPX (the X-coordinate at the shift point) and df (SPX), the maximal slope at the shift point. The effects of aging, gender and physical training were then analyzed on the curve. Aging did not affect lower plateau, upper plateau and SPX but augmented df (SPX), indicating greater blood pressure responses in older subjects during exercise. In females the curve was shifted to the left compared to males (SPX: 4.9 vs. 8.3 min, P < 0.05) without changes in plateaux and df (SPX), indicating greater blood pressure responses than males. Physical training for 3 weeks decreased the lower plateau from 157 to 144 mmHg (P < 0.05) and shifted the curve to the right (SPX: 7.1 vs. 8.6 min, P < 0.05), indicating unchanged blood pressure responses after training because of the opposite effects by decreases in the lower plateau vs. the curve shift to the right. In conclusion, blood pressure during exercise is better delineated by a logistic function curve than a linear regression model. The biological or physiological significance of df (SPX) is not clear at present and needs further investigations.

To clarify characteristics of the patients in whom exercise training lowers blood pressure and to elucidate the mechanisms by which exercise training lowers blood pressure, we evaluated 24-h blood pressure, glomerular filtration rate (GFR), renal blood flow (RBF), filtration fraction (FF), plasma renin activity (PRA), plasma aldosterone concentration (PAC), plasma norepinephrine concentration (PNE), and incremental area of insulin/glucose (sigmaI/sigmaG) during 75 g oral glucose tolerance test, and assessed arterial baroreceptor function (BSI) before and after a 3-week exercise training program (four 6-min sessions daily at 75% VO2 max). Patients were classified as responders (n = 15) if they showed statistically significant reduction in the multiple comparison of 24-h mean arterial pressure (MAP), or as nonresponders (n = 15) if they did not. Although there were no significant differences between responders and nonresponders in age, weight, MAP, GFR, RBF, RPF, FF, PNE, sigmaI/sigmaG, or BSI before exercise, renal vascular resistance (RVR; P.05), PRA (P.05), and PAC (P.05) were significantly higher in responders than in nonresponders. The fractional excretion of sodium (FENa) (P.05) were significantly lower in responders than in nonresponders. After exercise training, FF (P.01), RVR (P.05), PNE (P.05) PRA (P.01), and sigmaI/sigmaG (P.05) decreased significantly only in responders. The decrease in MAP significantly correlated with the reductions in FF (r = 0.46, P.05), PNE (r = 0.52, P.01) and RVR (r = 0.40, P.05). Thus, in patients who have higher RVR and PRA, exercise training lowered blood pressure in parallel to a reduction in RVR associated with decreases in sympathetic tone and improvement of insulin resistance. Our results suggest that exercise-induced changes in renal hemodynamics may contribute to the reduction in blood pressure in these patients.

Objective In hypertensive subjects, exercise training is a therapeutic modality that not only lowers blood pressure but also corrects metabolic abnormality, such as hyperinsulinemia. Insulin causes sympatho-excitation via the modification of baroreflex, norepinephrine release, or central sympathetic outflow. However, the link between neural and metabolic changes by exercise training in hypertensive patients remains unknown. The aim of this study was to examine whether or not the blood pressure lowering effect of exercise training is associated with the improvement of insulin sensitivity in conjunction with the inhibition of sympathetic tone in hypertensive patients. Methods We evaluated plasma insulin levels, arterial baroreflex function and humoral parameters before and after exercise training. Twenty-nine patients with essential hypertension under hospitalization participated in the study. Before and after three weeks of exercise training (75% max VO2, 6 min, q.i.d.), 24-hour blood pressure recordings, arterial baroreflex function testing and 75 g glucose tolerance tests were conducted. Area under the curve of insulin (∑ insulin) to glucose load was calculated as an index of hyperinsulinemia. Results Three weeks of exercise training decreased the 24-hour mean arterial pressure, heart rate and ∑ insulin, and improved baroreflex function. There was a significant correlation between the reduction of arterial pressure and the change in ∑ insulin. Furthermore, the reduction of ∑ insulin was correlated with the improvement of baroreflex function and with the decrease in heart rate. Conclusions Exercise training lowered the arterial pressure, with parallel changes in heart rate, baroreflex function and insulin resistance. The correction of sympathetic overactivity was closely associated with the amelioration of hyperinsulinemia. Our results suggest that the improvement of neuro-metabolic factors may be involved in the depressor effect caused by exercise training.(Internal Medicine 39: 1013-1019, 2000)

本研究は愛媛県重信川で侵入が確認されている外来性底生動物2種（サカマキガイおよびフロリダマミズヨコエビ）について，近年の分布状況を把握するとともに，流量減少に対する耐性を明らかにすることを目的とした．経年的な流程分布調査により，両種ともに汚濁が進行した重信川本流の中下流部に多く生息することが明らかになった．さらに，フロリダマミズヨコエビは近年分布域を上流側に拡大していることが分かった．流量低下の進行にともない実施した短期的な調査により，フロリダマミズヨコエビは一般的な底生動物と同様に流量低下により個体数が減少することが示された．一方，サカマキガイの相対密度が流量減少に伴って上昇したことから，同種は流量減少に対する耐性が高く，流量減少により侵入が助長される可能性があると考えられた．