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1.
The Relationship between Phytoplankton Diversity and Community Function in a Coastal Lagoon 总被引:3,自引:0,他引:3
The decrease of biodiversity related to the phenomena of global climate change is stimulating the scientific community towards
a better understanding of the relationships between biodiversity and ecosystem functioning. In ecosystems where marked biodiversity
changes occur at seasonal time scales, it is easier to relate them with ecosystem functioning. The objective of this work
is to analyse the relationship between phytoplankton diversity and primary production in St. André coastal lagoon – SW Portugal.
This lagoon is artificially opened to the sea every year in early spring, exhibiting a shift from a marine dominated to a
low salinity ecosystem in winter. Data on salinity, temperature, nutrients, phytoplankton species composition, chlorophyll
a (Chl a) concentration and primary production were analysed over a year. Modelling studies based on production-irradiance curves
were also conducted. A total of 19 taxa were identified among diatoms, dinoflagellates and euglenophyceans, the less abundant
group. Lowest diversities (Shannon–Wiener index) were observed just before the opening to the sea. Results show a negative
correlation (p<0.05) between diversity and chlorophyll a (Chl a) concentration (0.2–40.3 mg Chl a m−3). Higher Chl a values corresponded to periods when the community was dominated by the dinoflagellate Prorocentrum minimum (>90% of cell abundance) and production was maximal (up to 234.8 mg C m−3 h−1). Maximal photosynthetic rates (Pmax) (2.0–22.5 mg C mg Chl a−1 h−1) were higher under lower Chl a concentrations. The results of this work suggest that decreases in diversity are associated with increases in biomass and
production, whereas increases correspond to opposite trends. It is suggested that these trends, contrary to those observed
in terrestrial and in some benthic ecosystems, may be a result of low habitat diversity in the water column and resulting
competitive pressure. The occurrence of the highest photosynthetic rates when Chl a is low, under some of the highest diversities, suggests a more efficient use of irradiance under low biomass–high diversity
conditions. Results suggest that this increased efficiency is not explained by potential reductions in nutrient limitation
and intraspecific competition under lower biomasses and may be a result of niche complementarity. 相似文献
2.
Chlorophyll a (Chl a) seasonality was investigated in four shallow eutrophic lakes located in north-central British Columbia (western Canada).
Chlorophyll a concentration maxima in all four lakes occurred during the late summer/early autumn when near-surface total phosphorus ([Tot-P])
and total dissolved P concentrations, pH, and water temperature were highest. Mass balance and inferential analyses showed
that bloom-triggering P loads came mostly from within-lake sources, but that mechanisms controlling internal loading in Charlie
and Tabor (lakes having hypolimnetic oxygen deficits during summer) were fundamentally different than those in Nulki and Tachick
(isothermal, well oxygenated lakes). Although the timing and intensity of major blooms were associated with late summer/early
autumn P loads, average summer [Chl a] were predicted well by previously developed models based solely on spring overturn [Tot-P]. Instantaneous within-lake [Chl
a] were best predicted by models incorporating both surface [Tot-P] and temperature (r
2 = 0.57–0.70). Moreover, [Tot-P] and temperature combined accounted for 57% of among-lake variations in instantaneous [Chl
a]: log [Chl a] = 0.038 (°C) + 0.006 ([Tot-P]) + 0.203 (P < 0.001), where [Chl a] and [Tot-P] are in μg l−1. Positive associations between instantaneous [Chl a] and temperature support climate change models that forecast changes in phytoplankton productivity even if nutrient loading
rates remain constant.
Handling editor: D. Hamilton 相似文献
3.
Dennis Trolle Guangwei Zhu David Hamilton Liancong Luo Chris McBride Lu Zhang 《Hydrobiologia》2009,627(1):31-44
Distinct horizontal water column concentration gradients of nutrients and chlorophyll a (Chl a) occur within large, shallow, eutrophic Lake Taihu, China. Concentrations are high in the north, where some of the major
polluted tributaries enter the lake, and relatively low in the south, where macrophytes generally are abundant. It is not
clear, however, whether these water column concentration gradients are similarly reflected in spatial heterogeneity of nutrient
concentrations within the bottom sediments. The main objective of this study was therefore to test if horizontal and vertical
variations in the phosphorus and nitrogen content in bottom sediments of Lake Taihu are significantly related to (1) horizontal
variations in overlying water column nutrient concentrations and (2) other sediment geochemical constituents. We measured
the concentration of total phosphorus (TP) and total nitrogen (TN) in surficial sediments (0–2 cm) and TP, TN and Chl a concentrations in water column samples, collected from 32 sites in 2005. In 2006 sediment, TP, TN, carbon, iron and manganese
concentrations were measured vertically at 2 cm intervals, extending to a depth of approximately 20 cm, at an additional eight
sites. Linear correlation analysis revealed that surficial sediment TP concentrations across the 32 stations were related
significantly, though weakly, to annual mean water column concentrations of TP, TN as well as Chl a. Correlations of surficial sediment TN with water column variables were, however, not significant (P > 0.05). Amongst the geochemical variables tested, the vertical variability of sediment TP concentrations was most strongly
related to sediment manganese and carbon concentrations. A multiple stepwise linear regression revealed that the combination
of sediment manganese and carbon concentrations explained 91% of the horizontal variability in sediment TP concentrations
and 65% of the vertical variability.
Handling editor: Luigi Naselli-Flores 相似文献
4.
Heike Link Philippe Archambault Tobias Tamelander Paul E. Renaud Dieter Piepenburg 《Polar Biology》2011,34(12):2025-2038
Seasonal dynamics in the activity of Arctic shelf benthos have been the subject of few local studies, and the pronounced among-site
variability characterizing their results makes it difficult to upscale and generalize their conclusions. In a regional study
encompassing five sites at 100–595 m water depth in the southeastern Beaufort Sea, we found that total pigment concentrations
in surficial sediments, used as proxies of general food supply to the benthos, rose significantly after the transition from
ice-covered conditions in spring (March–June 2008) to open-water conditions in summer (June–August 2008), whereas sediment
Chl a concentrations, typical markers of fresh food input, did not. Macrobenthic biomass (including agglutinated foraminifera >500 μm)
varied significantly among sites (1.2–6.4 g C m−2 in spring, 1.1–12.6 g C m−2 in summer), whereas a general spring-to-summer increase was not detected. Benthic carbon remineralisation also ranged significantly
among sites (11.9–33.2 mg C m−2 day−1 in spring, 11.6–44.4 mg C m−2 day−1 in summer) and did in addition exhibit a general significant increase from spring-to-summer. Multiple regression analysis
suggests that in both spring and summer, sediment Chl a concentration is the prime determinant of benthic carbon remineralisation, but other factors have a significant secondary
influence, such as foraminiferan biomass (negative in both seasons), water depth (in spring) and infaunal biomass (in summer).
Our findings indicate the importance of the combined and dynamic effects of food supply and benthic community patterns on
the carbon remineralisation of the polar shelf benthos in seasonally ice-covered seas. 相似文献
5.
Rodrigo S. P. de Skowronski Paula F. Gheller Sandra Bromberg Carlos J. David Mônica A. V. Petti Thaïs N. Corbisier 《Polar Biology》2009,32(6):839-851
The spatial and temporal variation of microphytobenthic biomass in the nearshore zone of Martel Inlet (King George Island,
Antarctica) was estimated at several sites and depths (10–60 m), during three summer periods (1996/1997, 1997/1998, 2004/2005).
The mean values were inversely related to the bathymetric gradient: higher ones at 10–20 m depth (136.2 ± 112.5 mg Chl a m−2, 261.7 ± 455.9 mg Phaeo m−2), intermediate at 20–30 m (55.6 ± 39.5 mg Chl a m−2, 108.8 ± 73.0 mg Phaeo m−2) and lower ones at 40–60 m (22.7 ± 23.7 mg Chl a m−2, 58.3 ± 38.9 mg Phaeo m−2). There was also a reduction in the Chl a/Phaeo ratio with depth, from 3.2 ± 3.2 (10–20 m) to 0.7 ± 1.0 (40–60 m), showing a higher contribution of senescent phytoplankton
and/or macroalgae debris at the deeper sites and the limited light flux reaching the bottom. Horizontal differences found
in the biomass throughout the inlet could not be clearly related to hydrodynamics or proximity to glaciers, but with sediment
characteristics. An inter-summer variation was observed: the first summer presented the highest microphytobenthic biomass
apparently related to more hydrodynamic conditions, which causes the deposition of allochthonous material. 相似文献
6.
Periphyton biomass,potential production and respiration in a shallow lake during winter and spring 总被引:1,自引:0,他引:1
Abundance, depth distribution, potential productivity and respiration of periphyton on short-time (1 month) and long-time
incubated strips were followed monthly during the winter–spring (January–May) transition in a shallow eutrophic lake. A taxonomic
shift occurred from dominance of diatoms under ice to chlorophyte dominance in spring communities on the long-time incubated
strips, while diatoms dominated until May on the short-time incubated strips. Periphyton biomass accrual was low during the
ice-covered winter months (November–January: 4 mg chl a m−2 month−1), but increased to a maximum of 112 mg chl a m−2 month−1 immediately after ice-out in February. During February–April, the biomass remained constant before declining in May. Periphyton
on long-time incubated strips was equally distributed in the water column in winter (January–February), but was higher near
the water surface in spring (March–May). Periphyton did not change with depth on the short-time incubated strips. The potential
production to respiration ratio (P/R) was negatively correlated with periphyton biomass. Throughout the study, P/R was <1
for the short-time incubated periphyton, while this was only the case in March–April for the long-time incubations. This study
showed a high productive capacity of winter periphyton, resulting in accumulation of a relatively high periphytic biomass
early in the season. A massive periphyton density in eutrophic lakes already in winter–spring may potentially delay or prevent
the establishment and re-occurrence of submerged macrophytes in the early oligotrophication phase following a reduction of
the external nutrient loading.
Handling editor: Luigi Naselli-Flores 相似文献
7.
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
8.
M. G. Cano M. A. Casco L. C. Solari M. E. Mac Donagh N. A. Gabellone M. C. Claps 《Hydrobiologia》2008,614(1):33-45
Biomass assessments of algae in wetlands usually include only the phytoplankton community without considering the contribution
of other algal associations to total algal biomass. This omission prevents an accurate evaluation of the phytoplankton community
as an integral part of the total ecosystem. In the present work, the biomass contributions (expressed as chlorophyll-a content per m2 of lake) of phytoplankton, epiphyton on both submerged and emergent macrophytes, and epipelon were measured in Lacombe Lake,
Argentina, for the purpose of (1) establishing the relative importance of the phytoplankton and (2) evaluating the entire
contribution of algal biomass within the context of the Goldsborough & Robinson conceptual model. Our sampling was carried
out monthly for a year in sites representative of different conditions with respect to water depth and type of macrophytes.
Physicochemical analyses of water were performed following standard methods. Plankton was collected in a five-level profile
at deeper stations and in subsurface samples at the shallow one. Samples of sediment obtained with corers were collected for
epipelon sampling and segments of plants were cut at different levels, so as to obtain the epiphytes by scraping. Pigment
was extracted with aqueous acetone and calculations were made by means of the Lorenzen equation. According to the Goldsborough
& Robinson model, a Lake State developed here during the winter (phytoplankton maxima: 150 mg chlorophyll-a per m2). Then, through the subsequent growth of the submerged macrophytes, an Open State was observed, characterized by a maximum
epiphyton biomass (at 3,502 mg chlorophyll-a per m2) along with lower levels of phytoplankton biomass. The epiphytic algae on the emergent macrophytes were always present but
attained only relatively low biomass values (maximum: 120 mg of chlorophyll-a per m2 in February). The epipelon biomass varied between 50 and 252 mg chlorophyll-a per m2, registering a considerable contribution of settled algae from the water column (phytoplankton). This study contributes to
our knowledge of wetland dynamics through its assessment of the rapid changes in the relative contributions of both planktonic
and attached algae to the total algal biomass within the context of specific environmental factors.
Guest editors: U. M. Azeiteiro, I. Jenkinson & M. J. Pereira
Plankton Studies 相似文献
9.
Optical fractionation of chlorophyll and primary production for coastal waters of the Southern Ocean 总被引:1,自引:1,他引:0
Our objective was to quantify the potential variability in remotely sensed chlorophyll a (Chl a) and primary productivity in coastal waters of the Southern Ocean. From data collected throughout the springs/summers of
1991–1994, we calculated the proportion of water column Chl a and primary productivity within the upper optical attenuation length (K −1
par) and the satellite-weighted depth. The temporal variability was resolved every 2–3 days and was observed to be greater within
years than between years. Three-year averages (n=223) revealed that 10.2 ± 3.6% of total Chl a and 14.8 ± 6.5% of production occurred within satellite-weighted depth in predominantly Case I waters. The average values
were twice as high within K −1
par, 24.1 ± 8% of total Chl a and 34 ± 9% of production respectively. Masked in these long-term averages are very large changes occurring on short time
scales of seasonal blooms. We observed that the patterns of Chl a vertical distribution within blooms are also subject to taxonomic influence and dependent upon the physiological state of
the phytoplankton. Highest proportions of water column Chl a in the first optical depth were measured during the rapid onset of surface cryptophyte blooms each year, i.e. 50% within
K −1
par and 30% above the satellite-weighted depth. Lowest fractions, 6% and 2% of biomass within K −1
par and satellite-weighted depth respectively, were associated with peak bloom conditions independent of taxonomy. Our analyses
suggest that satellite-dependent models of Chl a and subsequent chlorophyll-dependent primary production will be challenging to develop for the near-shore Southern Ocean,
especially given the potentially high natural variability in the vertical distribution of Chl a driven by physical forcing, the photoadaptive abilities of polar phytoplankton, and taxonomic influences.
Accepted: 27 August 1999 相似文献
10.
Water and surficial sediment samples of Lake Chascomús and its tributaries were analyzed in order to relate changes in diatom
community structure to chemical variables. Over the course of 13 months of sampling, the lake exhibited major changes in water
level (1.15–1.98 m average depth), total dissolved solids (821–1972 mg l−1), silica (0.098–8.22 mg l−1), and total algal biomass (21.4–145.9 μg Chl a l−1). However, despite these large fluctuations, the diatom species composition was relatively stable. The dominant species in
the water column was always Synedra berolinensis (68.9%–90.1% total frustules), with Fragilaria construens and F. brevistriata as subdominants. In the sediments the latter two species dominated the frustule counts. These results indicate an unusual
floristic stability of this eutrophic ecosystem, with persistent dominance by broadly tolerant, generalist species.
Received: April 24, 2001 / Accepted: January 23, 2002 相似文献
11.
María Adela Casco María Elicia Mac Donagh María Gabriela Cano Lía Cristina Solari María Cristina Claps Nstor Adrin Gabellone 《International Review of Hydrobiology》2009,94(2):153-168
Annual changes in the algal density and concentrations of chlorophyll a, total phosphorus, and organic matter were analyzed in water and sediments at four sites characterized by the presence or absence of submerged and emergent macrophytes, during turbid‐ and clear‐water conditions to determine the contribution of the algal components of the plankton and the epipelon and to identify the most typical species in each community. Three states were recognized: one turbid and two clear, with different submerged macrophyte cover. The peaks of phytoplankton and epipelon occurred in the turbid phase, whereas the highest proportion of true epipelic algae in sediments was reached in the second clear phase. The Oscillatoriaceae dominated during the turbid phase in the water and throughout the entire year within the sediments. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
12.
Li-Chun Tseng Hans-Uwe Dahms Qing-Chao Chen Jiang-Shiou Hwang 《Helgoland Marine Research》2009,63(4):327-337
The South China Sea (SCS) is the world’s largest marginal sea being notable for vertical mixing at various scales resulting
in a sequence of chemical and biological dynamics in surface waters. We investigated the ingestion, gut content, evacuation
and clearance rates of copepods collected from six stations (including a South East Asia Time Series station) along a transect
line in the tropical of a SCS cruise during September 27, 1999 to October 2, 1999. The goal of the present study was to understand
the feeding ecology of copepods in the upper water layers (0–5 m) of the northern SCS during autumn. We measured the gut pigment
contents of 33 copepod species by the gut fluorescence method. The gut chlorophyll a values of most small size copepods (<1 mm) were lower than 1.00 ng Chl a individual−1. The highest gut pigment content was recorded in Scolecithrix danae (7.07 ng Chl a individual−1). The gut pigment contents of 33 copepod species (including 70 samples and 1,290 individuals) estimated is negatively correlated
with seawater temperature (Pearson correlation r = −0.292, P = 0.014) and is positively correlated with the chlorophyll a concentration of ambient waters (Pearson correlation r = 0.243, P = 0.043). Mean gut pigment content, ingestion and clearance rates (from 80 samples and 1,468 individuals) show that larger
copepods (>2 mm) had significantly higher values than medium sized copepods (1–2 mm) and smaller sized copepods. The present
study shows that the performance of feeding on phytoplankton was variable in different sized copepod groups, suggesting that
copepods obtained in the tropical area of the southeastern Taiwan Strait might be opportunistic feeders. 相似文献
13.
Production rates, abundance, chlorophyll a (Chl a) concentrations and pigment composition were measured for three size classes (<2 μm, 2–11 μm and >11 μm) of phytoplankton
from May to December 2000 in deep, mesotrophic, alpine lake Mondsee in Austria. The study focuses on differences among phytoplankton
size fractions characterised by their surface area to volume ratio ([mm2 l−1: mm3l−1]), pigment distribution patterns and photosynthetic rates. Particular attention was paid to autotrophic picophytoplankton
(APP, fraction <2 μm) since this size fraction differed significantly from the two larger size fractions. Among the three
fractions, APP showed the highest surface area to volume ratios and a high persistence in the pattern of lipophilic pigments
between temporarily and spatially successive samples (about 80% similarity of pigment composition between samples over seasons
and depths). The epilimnetic abundance of APP varied seasonally with an annual maximum of 180 × 103 cells ml−1 in June (at 4–9 m). The minimum (October at 12 m) was more than an order of magnitude lower (4.9 × 103 ml−1). APP peaked during autumn and contributed between 24% and 42% to the total area-integrated Chl a (10–23 mg m−2) and between 16% and 58% to total area-integrated production (5–64 mg m−2 h−1) throughout seasons. 相似文献
14.
The depth-related patterns in the benthic megafauna of the NE Weddell Sea shelf at the edge of the Fimbul Ice Shelf were investigated
at seven sites using towed camera platform photographs. Megafaunal density decreased with depth from 77,939 ha−1 at 245 m to 8,895 ha−1 at 510 m. While diversity was variable, with H′ ranging between 1.34 and 2.28, there were no depth related patterns. Multivariate analyses revealed two distinct assemblages;
a shallow assemblage with dense patches of suspension feeders in undisturbed areas and a deep assemblage where these were
not present. Disturbance from icebergs explained many observed patterns in faunal distribution. In shallow waters probable
effects of disturbance were observed as changes in successional stages; in deeper waters changes in habitat as a result of
past disturbance explained faunal distributions. In deeper areas ice ploughing created a mosaic landscape of fine and coarse
sediments. Total megafaunal density was highest in areas of coarse sediment (up to 2.9 higher than in finer sediment areas)
but diversity was highest in intermediate areas (H′ = 2.35). 相似文献
15.
16.
In order to evaluate hydrocarbon inputs to Crater Lake from anthropogenic and natural sources, samples of water, aerosol,
surface slick and sediment were collected and analyzed by gas chromatography-mass spectrometry (GC-MS) for determination of
their aliphatic and aromatic hydrocarbon concentrations and compositions. Results show that hydrocarbons originate from both
natural (terrestrial plant waxes and algae) and anthropogenic (petroleum use) sources and are entering the lake through direct
input and atmospheric transport. The concentrations of petroleum hydrocarbons range from low to undetectable. The distributions
and abundances of n-alkanes, polycyclic aromatic hydrocarbons (PAH) and unresolved complex mixture (UCM) from petroleum are similar for all surface
slick sampling sites. The estimated levels of PAH in surface slicks range from 7–9 ng/m2 which are low. Transport of petroleum-derived hydrocarbons from the lake surface has resulted in their presence in some sediments,
particularly near the boat operations mooring (total petroleum HC = 1440 μg/kg, dry wt. compared to naturally derived n-alkanes, 240 μg/kg, dry wt.). The presence of biomarkers such as the tricyclic terpanes, hopanes and steranes in shallow
sediments further confirms petroleum input from boat traffic. In the deep lake sediments, petroleum hydrocarbon concentrations
were very low (16 μg/kg, dry wt.). Very low concentrations of PAH were detected in shallow sediments (17–40 μg/kg at 5 m depth
near the boat operations) and deep sediments (3–15 μg/kg at 580 m depth). The individual PAH concentrations in sediments (μg/kg
or ppb range) are at least three orders of magnitude less than reported threshold effects levels (mg/kg or ppm range, test
amphipod Hyalella azteca). Therefore, no adverse effects are expected to occur in benthic biota exposed to these sediments. Boating activities are leaving a detectable level of petroleum in surface waters and lake sediments but these concentrations are very low. 相似文献
17.
Microphytobenthic oxygen production was studied in the Gulf of Fos (French Mediterranean coast) during 1991/1992 using transparent
and dark benthic chambers. Nine stations were chosen in depths ranging from 0.5 to 13 m, which represents more than 60% of
bottoms in the Gulf. Positive net microphytobenthic oxygen production was seasonally detected down to 13 m; the maximum value
attained was 60 mg O2 m−2 h−1 (0.7–0.8 g O2 m−2 d−1) in sediments at 0.5 m depth during spring and winter. Respiration rates were maximum in the sediments located at the mussel
farm (5 m), in the center of the Gulf, with 135 mg O2 m−2 h−1 in spring (3.2 g O2 m−2 d−1); in the other locations, it ranged from 3.3 to 58.2 mg O2 m−2 h−1 (0.08–1.4 g O2 m−2 d−1).
Compared to phytoplankton, microphytobenthos production was higher only in the bottoms < 1 m depth. In deeper bottom waters,
phytoplankton production could be absent due to light limitation, while microphytobenthos was still productive. Phytoplankton
production m−2 was generally higher than microphytobenthic production. Microphytobenthic biomass, higher than phytoplanktonic, varied from
27 to 379 mg Chl a m−2, the maximum in the mussel farm sediments, with the minimum in sandy shallow bottoms. Pigment analysis showed that microphytobenthos
consisted mainly of diatoms (Chl c and fucoxanthin) but other algal groups containing Chl b could become seasonally important. A Principal Component Analysis suggested that the main statistical factors explaining
the distribution of our observations may be interpreted in terms of enrichment in phaeopigments and light; the role of Chl
a appearing paradoxically as secondary in benthic production rates. Phaeopigments are mainly constituted by phaeophorbides,
which indicate grazing processes. The influence of the mussel farm on the oxygen balance is noticeable in the whole Gulf. 相似文献
18.
The study comprises a data set of CTD, optical properties—K
0(PAR), c
p, a(PAR), b(PAR)—and optical constituents—Chl a, SPM, CDOM—from 72 shelf and off-shelf stations in the Faroe Islands (62°N, 7°W) North East Atlantic, in early spring 2005.
Results showed that shelf waters surrounding the islands were cold and low saline, whereas off-shelf waters were warmer (~1°C)
and more saline (~0.05) PSU. A pronounced oceanographic front separated the two waters, and diffuse light attenuation K
0(PAR), beam attenuation c
p, Chl a, absorption a(PAR), and scattering coefficient b(PAR) were all significantly higher on the shelf. Analyses showed that off-shelf light attenuation K
0(PAR) was governed by Chl a, shown by a high (r
2 = 0.64) Chl a–K
0(PAR) correlation, whereas light attenuation on the shelf was governed by both Chl a, SPM, and CDOM in combination. A Chl a specific diffuse attenuation coefficient
K0* ( \textPAR ) K_{0}^{*} \left( {\text{PAR}} \right) of 0.056 (m2 mg−1 Chl a) and a Chl a specific beam attenuation (
c\textp* c_{\text{p}}^{*} ) of 0.27 (m2 mg−1 Chl a) coefficients were derived for the off-shelf. It is pointed out that Chl a is the single variable that changes over time as no rivers with high SPM and CDOM enter the shelf area. Data were obtained
in early spring, and Chl a concentrations were low ~0.5 mg Chl a m−3. Spring bloom Chl a are about 10 mg Chl a m−3 and estimations showed that shelf K
0(PAR) will increase about 5 times and beam attenuation about 10 times. The Faroe Islands shelf–off-shelf waters is a clear
example where physical conditions maintain some clear differences in optical properties and optical constituents. The complete
data set is enclosed. 相似文献
19.
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
20.
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