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1.
Tetsu Hirata 《Ecological Research》1991,6(1):101-111
From percentage covers of sessile organisms obtained over about 3 yr by suspending concrete plates at depths of 1.0, 2.5,
4.0 and 5.5 m in Nabeta Bay, Shimoda, Pacific coast of Japan, changes of five indices of community structure, i.e. number
of species (S), Shannon-Weaver diversity (H′), evenness (J′), McNaughton's dominance (MD) and Horn's similarity (HS), were investigated throughout succession. Colonization curves became
horizontal after reaching a maximum at 6 months after immersion at all depths. The number of species appeared to approach
equilibrium during the first year of immersion. In the period from 13 to 37 months after immersion, the five indices indicated
that communities at the upper two depths had stabilized structures within a limited range of variation, as represented by
low HS values, whereas those at the lower two depths had simplified structures, as indicated by low S orH′ values. Furthermore, the results of cluster analysis of samples at four depths indicated that 13 to 37-month communities
at the upper two depths had advanced, converged structures, whereas those at the lower depths had young, non-converged structures.
The stability of community structure observed at the upper two depths could be due to domination of two long-lived species,
the kelpEisenia bicyclis and the oysterCrassostrea nippona. On the other hand, the simplification of community structure at the lower two depths seems to be due to reduced domination
of these two species as a result of disturbances such as scouring by sand.
Contributions from the Shimoda Marine Research Center, No. 514. 相似文献
2.
To understand the characteristics of the ecosystem in Japanese lowland marsh, we investigated chlorophyll-a (Chl. a), photosynthesis and respiration of a phytoplankton community in a brownish-colored pond in Naka-ikemi marsh, Tsuruga, Fukui
Prefecture. Chl. a concentrations and volumetric gross primary production rates ranged between 1.3–57.0 μg Chl. a l−1 and 148–1619 μg C l−1 day−1 during the study period. Higher values of Chl. a and primary production rates were clearly observed from June to September, when the dominant algae were the phytoflagellates,
Peridinium (Dinophyceae) and Cryptomonas (Cryptophyceae), with swimming ability. The trophic status of the pond water of Naka-ikemi marsh was defined as being in
eutrophic condition based on the biomass and productivity of phytoplankton. However, depths of Z
1% showing the productive layer in this study site were relatively narrower than those observed in the hyper-eutrophic Lake
Suwa with frequent cyanobacterial water bloom. Factor-attenuating underwater light intensity in Naka-ikemi marsh was presumed
to be colored dissolved organic matter. Thus, not only phytoplankton primary production, but also allochthonous organic matter
supplied from the catchment area seems to be the dominant factor in the whole energy budget of the pond. In conclusion, we
regarded the pond ecosystem in Naka-ikemi marsh to be in a eutrophic–dystrophic condition. 相似文献
3.
Elina Leskinen 《Journal of applied phycology》1996,8(3):217-227
The effect of ammonium discharge from a food factory on the growth of attached microalgae was monitored north of the Hanko peninsula, on the southwestern coast of Finland. The impact of the discharge was studied at twelve localities, at four stages of seasonal succession. The microalgae were sampled from glass slides exposed at 0.4 m depth for two weeks. The variables measured for the microalgal growth were chlorophylla, primary production and total organic carbon (TOC). These were compared with planktonic chlorophylla and nutrient concentrations. The growth of attached microalgae displayed a consistent pattern of spatial distribution. Depending on season, TOC and primary production values were 7 to 70 times higher and chlorophylla values up to 1000 times higher close to the effluent outlet than in undisturbed areas of the archipelago. The microalgal samples near the discharge were characterized by low TOC/chlorophylla and TOC/primary production ratios. The temporal consistency of microalgal distribution illustrates the advantages of using attached algal assemblages in monitoring programmes. 相似文献
4.
Characteristics of settling matter and its role in nutrient cycles in a deep oligotrophic lake 总被引:1,自引:1,他引:0
The settling flux of seston (dry weight, DW), chlorophyll a (Chl a), particulate organic carbon (POC), particulate organic nitrogen (PON), and particulate phosphorus (PP) was measured monthly in 1981–1983 at 10 different depths in Lake Chuzenji, Japan; an oligotrophic lake with a maximum depth of 163 m. The Ti concentration in entrapped matter was used to separate the sedimentation flux into allochthonous and autochthonous components. Inflow loads of dissolved nutrients (DN: 4.5, DP: 0.48 g m-2a-1) were almost sufficient to supply the autochthonous fluxes at 30 m (PON: 2.9, PP: 0.51 g m-2a-1 ), and this flux of POC (26.6 g m-2a -1) was about one-third of primary production (84 g C M-2a-1). Sedimentation of particulate matter was the main path of losing nutrients from lake water, explaining more than 80% removal of inflow loads (TN, TP). Decomposition rates during sedimentation which were calculated from the vertical difference in the autochthonous flux agreed very closely with the results obtained by laboratory experiments of a 100-day incubation (content ratios from field observations were: POC 0.67, PON 0.65, PP 0.85; and from laboratory experiments they were: POC 0.68, PON 0.70, PP 0.94). These decomposition rates and those near the sediment interface were used to explain dissolved oxygen depletion and nitrate increase in the hypolimnion during stratification. The average sinking velocities were 1.82m d-1 for seston and 1.16 m d-1 for Chl a at 30m, they were influenced by Chl a content of seston. 相似文献
5.
Tetsu Hirata 《Ecological Research》1992,7(1):31-42
Successional changes of sessile organisms over about 3 years on concrete plates immersed at depths of 1.0, 2.5, 4.0 and 5.5
m in Nabeta Bay, Shimoda, Pacific coast of Japan, were investigated from their species composition, percentage cover, and
the structure, metabolism, biomass and maturity of the community for the purpose of verifying the hypothesis of succession
by Margalef (1968) and Odum (1969). The process of succession was divided into five stages from a cluster analysis based on
Horn's (1966) similarity in community structure. The five stages were characterized from dominant, species and 18 community
attributes in terms of structure, metabolism, biomass and maturity. With the advance of stages, two large-sized, long-lived
species, the kelpEisenia bicyclis and the oysterCrassostrea nippona, dominated; 18 community attributes showed a directional succession ending in a constant community structure, low community
metabolism, accumulation of community biomass except chlorophylla and an enhanced degree of community maturity. This directionality in succession of community attributes was valid for the
prediction of Margalef and Odum, despite a tendency for estimated daily energy budget to be more heterotrophic in such an
open system. From these results, it was suggested that the definition of succession by Odum (1969) should be interpreted as
the regularity in shift of dominant species, not individual species, and as the control of system by feedback mechanism developing
with succession rather than community-controlled mechanism. 相似文献
6.
Bronwyn E. Keatley Marianne S. V. Douglas Jules M. Blais Mark L. Mallory John P. Smol 《Hydrobiologia》2009,621(1):191-205
Relationships between key phytoplankton attributes including Chl a-specific light absorption, pigment composition and concentration, photosynthesis, primary production and community structure
were studied in two open shallow nutrient-poor coastal systems receiving similar amounts of sewage water. Both systems were
significantly nitrogen limited. However, differences in wastewater treatment (primary vs secondary) and sewage dilution (50%)
between the two systems caused a greater difference between systems than locally around the outflows. For both systems, water
at the outlet had significantly lower water transparency caused by a 20% higher absorption by coloured dissolved organic matter.
Nutrient concentrations were also elevated, gradually decreasing with distance north (governing current) of the outflows,
causing higher abundance of nano-sized phytoplankton, higher content of carotenoid pigments, 20–50% higher Chl a-specific absorption coefficients and higher photosynthetic capacity. Although maximum rates of Chl a-normalised photosynthesis were strongly related to nitrate availability, no effects were found on the derived areal primary
production or algal biomass suggesting that photosynthetic and optical parameters are more sensitive indicators of nutrient
enrichment than biomass or productivity.
Handling editor: Tasman Peter Crowe 相似文献
7.
The production parameters of the deep-water periphyton were investigated on the Macclesfield Bank (South China Sea) at depths down to 240 m. At 70–90 m depths the substrate is composed of the remains of dead corals and fragments of porous calcareous material overgrown with red coralline and articulated thalline algae Halimeda sp. At 220–240 m depths the substrate consists of rhodolites, which are individual unattached nodules encrusted mainly with red calcareous coralline algae Lithophyllum sp., Porolithon sp. and red lamellar alga Hypoglossum sp. At all depths the substrate is pierced with green filiform algae Ostreobium sp. and covered with benthic diatom algae. The zooperiphyton in the studied area is comprised of bryozoans, sponges, foraminifers and drilling mollusks. Respiration (R) and the gross (Pg) and net (Pn) primary production of the deepwater periphyton community were determined using the oxygen technique (polarographic electrode) at values of photosynthetically active radiation (PAR) close to natural levels. At 70–90 m depths the Pg of the photoperiphyton was 23.3 mg O2/(m2 h), and the Pn of the community had negative values due to respiration of phytoand mainly zooperiphyton and bacteria. At 220–240 m depths, where less than 0.001% of the surface PAR penetrates, the Pg of the phytoperiphyton decreased to 9.6 mg O2/(m2 h), and the R of the community was 25.9 mg O2/(m2 h). A high efficiency of light energy utilization by the phytoperiphyton was found. The apparent quantum yield (Fa) for algae collected at 70–90 m depths was close to the maximum level of 0.097. The values of Fn that we obtained for 220–240 m depths and calculated from identical data [27], were much higher than theoretical values, which cannot be explained based on modern views on the mechanisms of photosynthesis. Possible sources of errors are discussed. It is proposed that we observed additional evolution of oxygen as the result of H2O2 degradation. 相似文献
8.
ABSTRACT
We tested whether pelagic light and nutrient availability, metabolism, organic pools and CO2-supersaturation were related to lake size and surrounding forest cover in late summer–autumn measurements among 64 small
(0.02–20 ha), shallow seepage lakes located in nutrient-rich, calcareous moraine soils in North Zealand, Denmark. We found
a strong implicit scaling to lake size as light availability increased significantly with lake size while nutrient availability,
phytoplankton biomass and dissolved organic matter declined. Forest lakes had significantly stronger net heterotrophic traits
than open lakes as higher values were observed for light attenuation above and in the water, dissolved organic matter, pelagic
community respiration (R) relative to maximum gross primary production (R/GPP) and CO2-supersaturation. Total-phosphorus was the main predictor of phytoplankton biomass (Chl) despite a much weaker relationship
than observed in previous studies of larger lakes. Maximum gross primary production increased with algal biomass and decreased
with dissolved organic matter, whereas community respiration increased with dissolved organic matter and particularly with
gross primary production. These results suggest that exogenous organic matter supplements primary production as an energy
source to heterotrophs in these small lakes, and particularly so in forest lakes experiencing substantial shading from the
forest and dissolved humic material. This suggestion is supported by 20–30-fold CO2 supersaturation in the surface water of the smallest forest lakes and more than sixfold supersaturation in 75% of all measurements
making these lakes among the most supersaturated temperate lakes examined so far. 相似文献
9.
V. I. Kolmakov O. V. Anishchenko E. A. Ivanova M. I. Gladyshev N. N. Sushchik 《Journal of applied phycology》2008,20(3):289-297
Periphyton (epilithon) gross primary production (GPP) was estimated using the DCMU-fluorescence method in the Yenisei River.
In the unshaded littoral zone, chlorophyll a concentration (Chl a) and GPP value varied from 0.83 to 973.74 mg m−2and 2–304,425 O2 m−2 day−1 (0.64–95 133 mg C m−2 day−1), respectively. Positive significant correlation (r = 0.8) between daily GPP and periphyton Chl a was found. Average ratio GPP:Chl a for periphyton was 36.36 mg C mg Chl a m−2 day−1. The obtained GPP values for the Yenisei River have a high significant correlation with values predicted by a conventional
empirical model for stream periphyton. We concluded that the DCMU-fluorescence method can be successfully used for measuring
of gross primary production of stream phytoperiphyton at least as another useful tool for such studies. 相似文献
10.
Primary production of phytoplankton and secondary production of a daphnid and a chaoborid were studied in a small eutrophic
pond. The gross primary production of phytoplankton was 290 gC m−2 per 9 months during April–December. Regression analysis showed that the gross primary production was related to the incident
solar radiation and the chlorophylla concentration and not to either total phosphorus or total inorganic nitrogen concentration. The mean chlorophylla concentration (14.2 mg m−3), however, was about half the expected value upon phosphorus loading of this pond. The mean zooplankton biomass was 1.60
g dry weight m−2, of whichDaphnia rosea and cyclopoid copepods amounted to 0.69 g dry weight m−2 and 0.61 g dry weight m−2, respectively. The production ofD. rosea was high during May–July and October and the level for the whole 9 months was 22.6 g dry weight m−2.Chaoborus flavicans produced 10 complete and one incomplete cohorts per year. Two consecutive cohorts overlapped during the growing season. The
maximum density, the mean biomass, and the production were 19,100 m−2, 0.81 g dry weight m−2, and 11.7 g dry weight m−2yr−1, respectively. As no fish was present in this pond, the emerging biomass amounted to 69% of larval production. The production
ofC. flavicans larvae was high in comparison with zooplankton production during August–September, when the larvae possibly fed not only
on zooplankton but also algae. 相似文献
11.
Egg production of a brackish water calanoid copepod Acartia
bifilosa was measured in the laboratory in different chlorophyll
(Chl) a concentrations (0-24 mgr;
l-1) and temperatures 4-24C), and the cephalothorax length and carbon content
of females were determined. Egg production was positively correlated both
with Chl a concentration and with temperature; highest
egg production was obtained with 14-20 g Chl
a l-1 and at 13-18°C.
There was also a significant positive correlation between egg production
and female length-specific carbon content (g C
m-1). However, no correlation was observed
between egg production and cephalothorax length of females. Female carbon
content changed during the 3 day experiments; carbon content was positively
related to Chl a concentration and negatively related
to temperature. We conclude that food availability (Chl
a concentration), rather than temperature, limits the
egg production of A.bifilosa in the present study area
in the northern Baltic Sea. Further, both food concentration and
temperature affect egg production not only through the direct effect on the
numbers of eggs produced per female, but also through their effect on
female carbon content.
相似文献
12.
Investigation was made of the primary productivity of Lake Yunoko. The concentrations of PO4-P and NH3-N were highest in summer. The total amount of chlorophylla in the entire water column varied from 45 mg/m2 to 405 mg/m2 during the year with the maximum values occurring in late spring and in December. These values are very high compared with
those reported for other lakes in the same district. The standing crop of phytoplankton as organic carbon was approximately
50∼70% of the total particulate organic carbon in the lake with values as high as 80∼90% being obtained in the spring and
autumn. The rate of phytosynthesis under saturated light conditions was 3.7 mg C/mg chla/hr in the case of phytoplankton of the sun type and 1.2∼1.6 mg C/mg chla/hr in those of the shade type. The daily gross primary production in the lake varied from a low of 134 mg C/m2 to a high of 1,003 mg C/m2 during the year, the mean value being 372 mg C/m2. The total amount of daily microbial respiration varied from 177 mg C/m2 in winter to 1,476 mg C/m2 in summer. Thus, the daily balance of production and consumption of organic matter in the lake itself was concluded to be
negative. The main factor contributing to the rectification of this imbalance of material budget seems to be the leaf litter
coming from the forest surrounding the lake. In conclusion, Lake Yunoko is a very productive and at the same time, fairly
heterotrophic lake.
Special Project Research supported by the Ministry of Education on Dynamic State of Biosphere. This study was carried out
as part of JIBP-PF. 相似文献
13.
Effect of Vallisneria americana (L.) on community structure and ecosystem function in lake mesocosms 总被引:1,自引:1,他引:0
Cathleen Wigand John Wehr Karin Limburg Bernadette Gorham Sean Longergan Stuart Findlay 《Hydrobiologia》2000,418(1):137-146
Submerged aquatic vegetation is known as a key structural component and regulator in ecosystems. In this mesocosm study, we examine community- and system-level responses to the presence of Vallisneria americana (L), a deep-rooted macrophyte. Phytoplankton, bacteria and filamentous algal biomasses were significantly lowered in the presence of V. americana. In addition, mesocosms with macrophytes had significantly reduced porewater phosphate and iron, water column dissolved organic carbon and total suspended solids, but elevated sediment redox. All mesocosms were net autotrophic (gross primary production/respiration >1). Compared to the macrophyte treatments, the control mesocosms had lower diel net primary production (NPP) midway through the experiment (d 16), but at the end of the experiment (d 36), the controls had the higher values, presumably due to increased filamentous algae. NPP and NPP/R were constant in the macrophyte treatments, whereas NPP/R increased significantly from middle to end of the experiment in the controls. We show that community and system-level responses to the presence of V. americana have significant consequences on system structure and function. 相似文献
14.
Respiration in the Light and Bacterio-Phytoplankton Coupling in a Coastal Environment 总被引:1,自引:0,他引:1
In pelagic ecosystems, the principal source of organic matter is via autotrophic production and the primary sink is through
heterotrophic respiration. One would therefore anticipate that there is some degree of linkage between these two compartments.
Recent work has shown that respiration in the light is higher than dark respiration. Consequently, many of the methods used
to determine respiration and production are biased as they require the assumption that light and dark respiration rates are
equivalent. We show here that, in a coastal ecosystem, under visible light exposure, respiration in the light is related to
gross production. More than 60% of the variation of respiration in the light, measured at 1 to 40 μg L−1 of chlorophyll a (Chla), could be explained by the variations of gross production. Secondly, the relative contribution of bacterial respiration
to community respiration in the light represented up to 79% at low Chla (1 μg L−1) and was negatively correlated with Chla concentration. Although bacterial production and bacterial respiration were both enhanced in the light, bacterial respiration
in the light was more stimulated than bacterial production, which resulted in a decrease in bacterial growth efficiency during
light exposure. These results show that the impact of light on the functioning of the microbial loop needs to be taken into
account for a better understanding of the oceanic carbon cycle. 相似文献
15.
Luiz C. CotoviczJr. Bastiaan A. Knoppers Nilva Brandini Dominique Poirier Suzan J. Costa Santos Renato C. Cordeiro Gwenaël Abril 《Biogeochemistry》2018,137(1-2):1-14
We investigate the carbon dynamics in Guanabara Bay, an eutrophic tropical coastal embayment surrounded by the megacity of Rio de Janeiro (southeast coast of Brazil). Nine sampling campaigns were conducted for dissolved, particulate and total organic carbon (DOC, POC and TOC), dissolved inorganic carbon (DIC), partial pressure of CO2 (pCO2), chlorophyll a (Chl a), pheo-pigments and ancillary parameters. Highest DOC, POC and Chl a concentrations were found in confined-shallow regions of the bay during the summer period with strong pCO2 undersaturation, and DOC reached 82 mg L?1, POC 152 mg L?1, and Chl a 800 μg L?1. Spatially and temporally, POC and DOC concentrations varied positively with total pigments, and negatively with DIC. Strong linear correlations between these parameters indicate that the production of TOC translates to an equivalent uptake in DIC, with 85% of the POC and about 50% of the DOC being of phytoplanktonic origin. Despite the shallow depths of the bay, surface waters were enriched in POC and DOC relative to bottom waters in periods of high thermohaline stratification. The seasonal accumulation of phytoplankton-derived TOC in the surface waters reached about 105 g C m?2 year?1, representing between 8 and 40% of the net primary production. The calculated turnover time of organic carbon was 117 and 34 days during winter and summer, respectively. Our results indicate that eutrophication of coastal bays in the tropics can generate large stocks of planktonic biomass and detrital organic carbon which are permanently being produced and partially degraded and buried in sediments. 相似文献
16.
Phosphorus inputs unmask negative effects of ultraviolet radiation on algae in a high mountain lake 总被引:2,自引:0,他引:2
P. CARRILLO J. A. DELGADO-MOLINA† J. M. MEDINA-SÁNCHEZ† F. J. BULLEJOS† M. VILLAR-ARGAIZ† 《Global Change Biology》2008,14(2):423-439
Ultraviolet solar radiation (UVR) and atmospheric nutrient loads to pristine ecosystems are global climate change phenomena that simultaneously affect aquatic organisms in ways not easily predicted by single factor studies. Plankton in a high mountain lake was exposed in situ to increasing phosphorus (P) concentrations (mimicking atmospheric pulses) in absence or presence of UVR in order to identify their interactive effect on functional [primary production, organic carbon (C) release (EOC), and percentage of C released (%EOC)], growth rate, structural–physiological (algal biomass, sestonic C, P content, chlorophyll a (Chl a), and Chl a : C ratio, P cell quota, cell‐specific Chl a), and stoichiometric (autotroph C : P ratio) traits. The availability of P after the pulse determined the intensity of responses by primary producers to UVR stress. All structural–physiological and functional variables significantly increased by up to two orders of magnitude in response to P enrichment. UV radiation, over a long‐term scale, exerted significant deleterious effects on most structural–physiological variables when inorganic P was added at high levels (≥30 μg P L?1). The subsequent unexpected negative synergistic UVR × P effect on algal development did not support our initial hypothesis that P input might buffer the harmful UVR effect. UVR exerted a weak negative effect on primary production but strongly enhanced the absolute and percentage excretion of C (up to 60%), mechanism responsible of a significant reduction in autotroph C : P ratios. We propose that low sestonic C : P ratios are the outcome of an adaptive strategy of algae in environments with high UVR exposure and extreme nutrient limitation and have important implications for C flux through grazing vs. microbial food webs in oligotrophic systems. 相似文献
17.
A comparison of periphyton community structural and functional responses to heavy metals 总被引:2,自引:2,他引:0
This study evaluates the effectiveness of community production and respiration measurements as monitoring tools for environmental impact evaluations and compares these data to community structural data.In Prickly Pear Creek, Montana, production and respiration rates were determined for periphyton communities in control, impact and recovery reaches using colonized granite substrates and sealed plexiglas chambers. Values for gross primary productivity (GPP), community respiration (CR24), ash-free dry mass (AFDM) and chlorophyll a content (Chla) were obtained for each granite slab. Of these, AFDM, Chla and CR24 were statistically significant among sites (P0.01). Although mean values for GPP appeared to differ among reaches, statistical differences could not be inferred because of large variances associated with this measure. These data indicate that inherent variability may limit the use of community function measures in routine environmental monitoring. However, production/respiration methods provide valuable data about emergent properties of aquatic communities that cannot be derived from routine population censuses. 相似文献
18.
Research on aquatic ecosystems has shown the presence of diel (24 hour) variations of chlorophylla. In order to investigate this phenomenon in the Great Lakes, an IFYGL program was set up in which 8 cruises were made roughly monthly between April and October 1972. Two Lake Ontario Stations were chosen, one inshore near Oshawa, Ontario and the other mid-lake. Chlorophylla samples were taken approximately every two hours at depths of 1, 5 and 1o m at the inshore station and 1, 10 and 20 m at the mid-lake station.Chlorophylla concentrations at the 1 m depth were reduced during periods of high light intensities, but this phenomenon was observed only during the late June and July cruises at the near-shore station. Apparently, during most cruises, light intensities were too low to produce this effect. Coefficients of variation of chlorophylla concentrations as great as too% occurred at the deeper sampling depth during periods when the thermocline was well developed. This variability was associated with a thermocline motion in which the fixed depths sampled moved from the epilimnion into the thermocline or the hypolimnion and back again over the sampling period. When the lake was not thermally stratified, variability of chlorophylla concentrations was also observed with coefficients of variations between 20–3o%. Horizontal advection by currents, vertical turbulence, and presence of Langmuir cells were possible mechanisms causing such chlorophylla variability.In light of these observations, caution must be used in interpreting spatial and temporal distributions of chlorophylla in lakes. Special care must be taken when sampling at depths near the thermocline due to movements that take place. For this reason, water samples taken from the epilimnion during periods of thermal stratification are recommended as opposed to fixed depth or integrated samples which could be affected by thermocline movements.This study was undertaken as part of the International Field Year for the Great Lakes, a joint Canadian-U.S. contribution to the International Hydrological Decade Program 相似文献
19.
1. Oligotrophic Lake Waikaremoana, New Zealand, is used for hydroelectric power generation and the lake levels are manipulated within an operating range of 3 m. There was concern that rapidly changing water levels adversely affected the littoral zone by decreasing light availability in two ways: local turbidity caused by shoreline erosion at low water levels; and decreased light penetration to the deep littoral zone caused by high water levels in summer. 2. The littoral zone was dominated by native aquatic plants with vascular species to 6 m and a characean meadow below this to 16 m. The biomass and heights of the communities in the depth zone 0–6 m were reduced at a site exposed to wave action relative to those at a sheltered site. However, the community structure below 6 m was similar at exposed and sheltered sites. The lower boundary of the littoral zone was sharply delimited at 16 m and this bottom boundary remained constant throughout the year despite large seasonal changes in solar radiation and the 3 m variation in lake level. 3. There was evidence that the deep-water community consisting of Chara corallina had adapted physiologically to low-light conditions. Net light saturated photosynthesis (CO2 exchange) per unit chlorophyll a (Chl a) was reduced to 1.7 μg C (μg Chl a)?1 h?1 at the lower boundary, half of that recorded at 5 m. The concentration of Chi a per gram of biomass (dry weight), was considerably greater at the lower boundary than higher in the profile [c. 7 mg Chl a (g dry wt)?1 at 16 m vs. 4 mg Chl a (g dry wt)?1 at 5 m]. Chl b also increased with depth and there was no change in the ratio of Chl a and Chl b with increasing depth. The saturation light intensity (Ik) of the community at the lower boundary was only 78 μmol photons m?2 s?1. Photosynthetic parameters (Ik and α) as well as the Chl a content remained relatively constant throughout the seasonal and short-term changes in radiation. 4. The photosynthetic characteristics of the littoral community were therefore not greatly affected by the lake level change caused by the present hydroelectric operations. However, the sharpness of the lower boundary and its extreme shade characteristics imply that the deep-water community would be sensitive to any further changes in underwater light availability. 相似文献
20.
为了解演替中期和后期优势树种对冬季不同光强的适应性,对在全光照(100%自然光强)和低光照(30%自然光强)下生长的演替中期优势种木荷(Schima superba)、锥栗(Castanopsis chinensis)和黧蒴(Castanopsis fissa)及演替后期优势种华润楠(Machilus chinensis)、黄果厚壳桂(Cryptocarya coninna)和厚壳桂(Cryptocarya chinensis)的生理生化响应进行了研究。结果表明,与全光照相比,低光照下演替中期优势树种幼叶的非光化学猝灭(NPQ)、类胡萝卜素与叶绿素的比值(Car/Chl)和花色素苷含量下降,细胞质膜渗透率增加;而演替后期优势树种幼叶的花色素苷含量增加、细胞质膜渗透率降低,且受光抑制的程度低(Fv/Fm高)。此外,除总抗氧化能力外,演替中期优势树种幼叶的花色素苷含量、NPQ和Car/Chl均显著低于演替后期优势种。因此,演替后期优势树种可以通过灵活多样的光保护策略来提高对冬季强光环境的适应能力,而演替中期优势种在光保护策略的多样性及光保护能力上均弱于演替后期优势种。 相似文献