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1.
Haimanti Biswas Mitali Dey Dipnarayan Ganguly Tarun K. De Sandip Ghosh Tapan K. Jana 《Estuaries and Coasts》2010,33(2):395-398
Inter-annual variations of phytoplankton abundance and community organization were observed over a two-decade period along
with the ancillary parameters at the land–ocean boundary associated with the Sundarban mangrove forest (21°32′ and 22°40′
N and 88°05′ and 89° E), along the NE Coast of the Bay of Bengal. The number of definable Bacillariophyceae species exceeded Dinophyceae taxa, and the total number of bloom-forming species declined from a maximum of ten in 2000 and a minimum of two in 2007.
Blooms of the diatom Coscinodiscus radiatus were common in 2000 and 2007. Tide cycles and the onset of the monsoon season played important roles in diurnal and seasonal
variability of phytoplankton. Phytoplankton biovolume showed seasonality, with the highest levels during post-monsoon periods
and lowest levels during the monsoon period. Phytoplankton abundance was correlated to rainfall patterns, which may be altered
by long-term changes in climate. 相似文献
2.
The Skidaway River estuary, GA (USA), a tidally dominated subtropical system surrounded by extensive Spartina salt marshes, is experiencing steady increases in nutrients, chlorophyll, and particulate matter and decline in dissolved
oxygen, associated with cultural eutrophication. A long-term study is documenting changes in these parameters: previous papers
Verity (Estuaries 25:944–960, 2002a, Estuaries 25:961–975, b) reported on hydrography, nutrients, chlorophyll, and particulate matter during 1986–1996; plankton community responses are
reported here. Phytoplankton, bacteria, heterotrophic nanoplankton and dinoflagellates, ciliates, and copepods exhibited strong
seasonal cycles in abundance driven by temperature and resource availability, typically with summer maxima and winter minima.
However, cultural eutrophication coincided with altered planktonic food webs as autotrophic and heterotrophic communities
responded to increasing concentrations and changing ratios of inorganic and organic nutrients, potential prey, and predators.
Small (<8 μm) photosynthetic nanoplankton increased in absolute concentration and also relative to larger cells. In contrast,
diatoms did not show consistent increases in abundance, despite significant long-term increases in ambient silicate concentrations.
Mean annual bacteria concentrations approximately doubled, and eukaryotic organisms in the microbial food web (heterotrophic
and mixotrophic flagellates, dinoflagellates, ciliates, and metazoan zooplankton) also increased. All plankton groups except
copepods showed trends of increasing annual amplitudes between seasonal high and low values, with higher peak concentrations
each year. These observations suggest that the eutrophication signal was gradually becoming uncoupled from regulatory mechanisms.
Theory and evidence from other more impacted waters suggest that, if these patterns continue, changes in the structure and
function of higher trophic levels will ensue. 相似文献
3.
Adriana Zingone Laurent Dubroca Daniele Iudicone Francesca Margiotta Federico Corato Maurizio Ribera d’Alcalà Vincenzo Saggiomo Diana Sarno 《Estuaries and Coasts》2010,33(2):342-361
The climatology and interannual variability of winter phytoplankton was analyzed at the Long Term Ecological Research Station
MareChiara (LTER-MC, Gulf of Naples, Mediterranean Sea) using data collected from 1985 to 2006. Background winter chlorophyll
values (0.2–0.5 μg chl a dm−3) were associated with the dominance of flagellates, dinoflagellates, and coccolithophores. Winter biomass increases (<5.47 μg
chl a dm−3) were often recorded until 2000, generally in association with low-salinity surface waters (37.3–37.9). These blooms were
most often caused by colonial diatoms such as Chaetoceros spp., Thalassiosira spp., and Leptocylindrus danicus. In recent years, we observed more modest and sporadic winter biomass increases, mainly caused by small flagellates and small
non-colonial diatoms. The resulting negative chl a trend over the time series was associated with positive surface salinity and negative nutrient trends. Physical and meteorological
conditions apparently exert a strict control on winter blooms, hence significant changes in winter productivity can be foreseen
under different climatic scenarios. 相似文献
4.
Dinoflagellate Cysts in Coastal Sediments as Indicators of Eutrophication: A Case of Gwangyang Bay,South Sea of Korea 总被引:1,自引:0,他引:1
Diatom densities in the surface water and dinoflagellate cysts in bottom sediments of Gwangyang Bay were studied to determine
changes in the phytoplankton community structure in response to anthropogenic eutrophication and to assess the use of dinoflagellate
cysts as indicators of coastal eutrophication. Our results show that, in nutrient-enriched environments, diatoms are particularly
benefited from the nutrients supplied and, as a consequence, heterotrophic dinoflagellates that feed on the diatoms can be
more abundant than autotrophic dinoflagellates. In short-core sediment records, a marked shift in autotrophic–heterotrophic
dinoflagellate cyst compositions occurred at a depth of approximately 9–10 cm corresponding to the timing of the 1970s industrialization
around Gwangyang Bay. This tentatively indicates that diatom and dinoflagellate communities here have undergone a considerable
change mainly due to increased nutrient loadings from both domestic sewage effluent and industrial pollution. Our study suggests
a possible potential use of dinoflagellate cysts in providing retrospective information on the long-term effects of coastal
eutrophication. 相似文献
5.
P V BHASKAR RAJDEEP ROY MANGESH GAUNS D M SHENOY V D RAO S MOCHEMADKAR 《Journal of Earth System Science》2011,120(6):1145-1154
An unusual phytoplankton bloom dominated by unidentified green coloured spherical algal cells (∼5μm diameter) and dinoflagellates
(Heterocapsa, Scripsiella and Gymnodinium) was encountered along the coast of Goa, India during 27 and 29 January, 2005. Pigment analysis was carried out using both
fluorometric and HPLC methods. Seawater samples collected from various depths within the intense bloom area showed high concentrations
of Chl a (up to 106 mg m − 3) associated with low bacterial production (0.31 to 0.52 mg C m − 3 h − 1) and mesozooplankton biomass (0.03 ml m − 3). Pigment analyses of the seawater samples were done using HPLC detected marker pigments corresponding to prasinophytes,
dinoflagellates and diatoms. Chlorophyll b (36–56%) followed by peridinin (15–30%), prasinoxanthin (11–17%) and fucoxanthin (7–15%) were the major diagnostic pigments
while pigments of cryptophytes and cyanobacteria including alloxanthin and zeaxanthin formed <10%. Although microscopic analysis
indicated a decline in the bloom, pheaophytin concentrations in the water column measured by both techniques were very low,
presumably due to fast recycling and/or settling rate. The unique composition of the bloom and its probable causes are discussed
in this paper. 相似文献
6.
Phytoplankton seasonal and interannual variability in the Guadiana upper estuary was analyzed during 1996–2005, a period that
encompassed a climatic controlled reduction in river flow that was superimposed on the construction of a dam. Phytoplankton
seasonal patterns revealed an alternation between a persistent light limitation and episodic nutrient limitation. Phytoplankton
succession, with early spring diatom blooms and summer–early fall cyanobacterial blooms, was apparently driven by changes
in nutrients, water temperature, and turbulence, clearly demonstrating the role of river flow and climate variability. Light
intensity in the mixed layer was a prevalent driver of phytoplankton interannual variability, and the increased turbidity
caused by the Alqueva dam construction was linked to pronounced decreases in chlorophyll a concentration, particularly at the start and end of the phytoplankton growing period. Decreases in annual maximum and average
abundances of diatoms, green algae, and cyanobacteria were also detected. Furthermore, chlorophyll a decreases after dam filling and a decrease in turbidity may point to a shift from light limitation towards a more nutrient-limited
mode in the near future. 相似文献
7.
The introduction of invasive bivalves such as the zebra mussel (Dreissena polymorpha) can have profound effects on aquatic ecosystems, including decreases in phytoplankton biomass and changes in the taxonomic
composition of phytoplankton. Zebra mussel introductions have been associated with increased dominance of cyanobacteria, especiallyMicrocystis, but this change may depend on interacting physical, chemical, or biotic conditions. We used a 12-yr record in the Hudson
River to explore the relationship between phytoplankton composition and zebra mussel filtration. During this period (1993–2005),
the mean July–September filtration rate of the zebra mussel (ZMF) varied by 8-fold, and the mean biovolume of cyanobacteria,
which was dominated byMicrocystis, varied from 0 to 4.2 mm3 1−1 and comprised up to 52% of total phytoplankton biovolume. There was a tendency for high cyanobacterial biomass to be associated
with low rather than high ZMF. Neither the absolute nor the relative amounts of either total cyanobacteria orMicrocystis were significantly correlated to ZMF alone or in combination with total phosphorus or any other, physical or chemical parameters
that we measured. Cyanobacteria dominance and abundance were both strongly correlated to temperature, and over 80% of the
among year variance in cyanobacterial dominance could be explained by temperature in a linear model. Temperature in combination
with dissolved SiO3 explained 90% of the variation in cyanobacterial dominance. At higher temperatures and lower dissolved SiO3, cyanobacterial abundance increased, at the expense of diatoms that dominated at lower temperatures and a higher SiO3 years. The high explanatory value of temperature is surprising as the variation in temperature among years was relatively
low (24.0–26.8°C). The results suggest that event slightly increased temperatures could lead to higher biomass and dominance
of cyanobacteria in some aquatic systems. 相似文献
8.
Elizabeth Fejes Daniel Roelke George Gable James Heilman Kevin McInnes David Zuberer 《Estuaries and Coasts》2005,28(1):96-107
Carbon entering the food web originating from microalgal productivity may be as important to salt marsh consumers as carbon
originating from vascular plant production. The objective of this study was to further our understanding of the role played
by microalgae in salt marshes. We focused on microalgal productivity, community dynamics, and pelagic food web linkages. Across
three consecutive springs (2001–2003), we sampled the upper Nueces Delta in southeast Texas, United States; a shallow, turbid
system of ponds and elevated vegetated areas stressed by low freshwater inflow and salinities ranging from brackish (11) to
hypersaline (300). Despite high turbidity and low external nutrient loadings, microalgal productivity was on the order of
that reported for vascular plants. Primary productivity in surface waters ranged from 0 to 2.02 g C m−2 d−1 and was usually higher than primary productivity associated with the benthos, which ranged from 0 to 1.14 g C m−2 d−1. This was likely due to high amounts of wind-driven resuspended sediment limiting production at greater depths. Most of the
water column microalgal biovolume seemed to originate from the benthos and was comprised mostly of pennate diatoms. But true
phytoplankton taxa were also observed, which included cryptomonads, chlorophyhtes dinoflagellates, and cyanobacteria. Succession
from r-selected to K-selected taxa with the progression of spring, a common phenomena in aquatic systems, was not observed.
Codominance by both potentially edible and less edible taxa was found. This was likely due to decreased grazing pressure on
r-selected taxa as salinity conditions became unfavorable for grazers. In addition to a decoupled food web, reduced primary
and net productivity, community respiration, and microalgal and zooplankton population densities were all observed at extreme
salinities. Our findings suggest that a more accurate paradigm of salt marsh functioning within the landscape must account
for microalgal productivity as well as production by vascular plants. Because the value of microalgal productivity to higher
trophic levels is taxa specific, the factors that govern microalgal community structure and dynamics must also be accounted
for. In the case for the Nueces Delta, these factors included wind mixing and increasing salinities. 相似文献
9.
Clarisse Odebrecht Marli Bergesch Leonardo Rubi R?rig Paulo C. Abreu 《Estuaries and Coasts》2010,33(2):570-583
A long-term study (monthly sampling, 1992 to 2007) was conducted in the surf zone of Cassino Beach, Southern Brazil, in order
to detect possible natural and/or anthropogenic disturbances. Surface water temperature (6–29°C) was the only parameter with
predictable seasonal variation; salinity (14–38) was inversely related to rainfall (3.1–485.2 mm month−1) and low values followed extreme precipitation periods in 1997/1998 and 2002/2003 (El Ni?o years). Asterionellopsis glacialis and chlorophyll a presented high concentrations and peak frequency until 1998, when an intense mud deposition occurred with concomitant extreme
rainfall. It affected the surf zone and beach, changing the hydrology and dissolved inorganic nutrient availability. Six phytoplankton
species groups were recognized with distinct responses to this mud deposition. We conclude that large-scale climatic changes,
like El Ni?o Southern Oscillation, in conjunction with human activities significantly altered the phytoplankton ecology of
the highly dynamic Cassino Beach surf zone. 相似文献
10.
Evelyn Lawrenz James L. Pinckney Melissa L. Ranhofer Hugh L. MacIntyre Tammi L. Richardson 《Estuaries and Coasts》2010,33(5):1186-1201
We investigated spatial and temporal relationships between spectral irradiance and phytoplankton community composition in
the blackwater-influenced estuary Winyah Bay, South Carolina. Upstream, high concentrations of chromophoric dissolved organic
matter (CDOM) absorbed blue wavelengths, resulting in a predominantly red light field. Green light prevailed downstream near
the lower-CDOM coastal ocean, and phytoplankton community composition was distinct from upstream and mid-estuarine communities.
Diatoms were abundant throughout the estuary in January, August, and October, cryptophytes dominated in July, and chlorophytes
were abundant in December 2006. Only diatoms and chlorophytes showed significant covariation with the spectral attenuation
coefficient (k(λ)): Chlorophytes showed positive relationships with k(442) (blue light) while diatoms were negatively correlated with k(442) and k(490) (violet to blue). Phytoplankton community composition in Winyah Bay appears to be driven by strong horizontal flow rather
than gradients in spectral irradiance, but results indicate that water color is likely to play a greater role in blackwater-influenced
estuaries with longer residence times. 相似文献
11.
Peter A. Thompson 《Estuaries and Coasts》1998,21(4):801-817
During 1995 the phytoplankton in the Swan River were intensively sampled to assess biomass and species composition. Continuous measurements of fluorescence, salinity, and temperature were made weekly during 40 km sampling trips along the estuary and used to map the seasonal progression of the algal biomass. Weekly measurements of primary production were made and used to model net primary production from the vertical distribution of biomass, irradiance, and phytoplankton species composition. Potential nutrient limitation was assessed with “all but one” nutrient bioassays. The results indicate a complex mixture of potentially limiting factors, which vary in time and space. Although the data sequence is short, it suggests a annual succession pattern of diatoms, chlorophytes, diatoms, and finally dinoflagellates and cryptophytes in late summer-autumn. Peak seasonal biomass was observed during January to April. Mean annual chlorophylla biomass was greatest in upstream stations (5–9), where estimates of net primary production rates averaged 1.55 g C m?2 d?1 and gross primary production was 800–1000 g C m?2 yr?1. Potential nutrient limitation was most severe from November to May, although not during January 1995. Based on bioassay results, during the period of greatest potential for nutrient limitation, nitrogen was 15 to 30 times more limiting to biomass development than phosphate. Runoff due to consistent rainfall during winter eventually breaks down stratification and flushes the estuary with low-salinity, nutrient-rich water, producing, a light-limited, nutrient-rich aquatic ecosystem. Timing and magnitude of physical forcing events, mainly rainfall, appear critical in determining the susceptibility of this ecosystem to summer and autumn algal blooms. 相似文献
12.
Iveta Jurgensone Jacob Carstensen Anda Ikauniece Baiba Kalveka 《Estuaries and Coasts》2011,34(6):1205-1219
Trends in phytoplankton monitoring data (1976–2008) from the Gulf of Riga were investigated and linked to environmental factors.
Annual means of spring phytoplankton biomass correlated to phosphorus input from land and shifts between diatoms and dinoflagellates
were attributed to potential Si limitation and time of sampling relative to the spring phytoplankton succession. The summer
phytoplankton biomass, which more than doubled over the study period, was related to the abundance of summer copepods that
similarly declined. Cyanobacterial blooms proliferated in summer and the proportion of diatoms similarly declined when the
winter–spring inorganic N/P ratio was low. The chlorophyte proportion in summer increased over the study period, and this
was linked to increasing temperatures favoring their higher growth rates. The dinoflagellate proportion appeared to decrease
with temperatures above a threshold of 15.5°C. Although nutrient inputs and their ratios are important factors for the phytoplankton
community, this study suggests that climate change and overfishing could be equally important. 相似文献
13.
Lateglacial and early Holocene climatic fluctuations recorded in the diatom flora of Xiaolongwan maar lake,NE China 总被引:1,自引:0,他引:1
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Qiang Gao Patrick Rioual Guoqiang Chu 《Boreas: An International Journal of Quaternary Research》2016,45(1):61-75
A palaeolimnological study of the annually laminated sediment sequence of Lake Xiaolongwan, a small maar lake in northeastern China, revealed distinct diatom responses to Lateglacial and early Holocene climate change between c. 19 700 and c. 10 700 a BP. In addition to analyses of diatom assemblage composition and of the biovolume accumulation rate of planktonic diatoms, geochemical (total nitrogen, total organic carbon) and physical (varve type and thickness) indicators were used to assess past environmental change. The diatom assemblages reveal a complex interplay between direct climate effects on the seasonal lake conditions (timing of ice cover break‐up, water column mixing and thermal stratification), catchment‐mediated effects on the concentrations of nutrients and dissolved organic carbon and, possibly, biotic interactions between the different algal groups present in the phytoplankton of Lake Xiaolongwan (diatoms, Chrysophyceae and Dinophyceae). The most remarkable changes in the aquatic system were: (i) a sharp increase in Asterionella formosa and the collapse of Handmannia balatonis at c. 14 780 a BP, corresponding with the onset of the Bølling – Allerød interstadial; (ii) a sharp rise in Stephanodiscus minutulus at c. 12 840 a BP, marking the start of the Younger Dryas event and (iii) when the lake phytoplankton became dominated by Dinophyceae instead of diatoms at c. 11 170 a BP, after the Pre‐Boreal oscillation. Two diatom assemblage zones characterize the Younger Dryas at Lake Xiaolongwan, suggesting a bipartite division of this stadial event as in several records from eastern Asia and Europe. The quasi‐synchronicity of these events with the oscillations described in the North Atlantic realm demonstrates that during the Lateglacial, North Atlantic dynamics at centennial and millennial time scales had a strong control upon the climate in northeastern China. 相似文献
14.
We provide an introduction and a foreword to the Special Issue “Phytoplankton Time Series in Estuaries and Coastal Ecosystems”.
This issue includes long-term investigations (10–40 years) of 22 coastal ecosystems and a comparative analysis of chlorophyll
a from 84 time series. The results and conclusions provided by these studies help to illuminate the disparities and similarities
in long-term phytoplankton dynamics among a wide range of coastal systems and provide insight into the major driving factors
responsible for short- and long-term trends in phytoplankton communities. 相似文献
15.
Many Gulf of Mexico estuaries have low ratios of water volume to bottom surface area, and benthic processes in these systems
likely have a major influence on system structure and function. The purpose of this study was to determine the spatiotemporal
distribution of biomass and community composition of subtidal benthic microalgal (BMA) communities in Galveston Bay, TX, USA,
compare BMA community composition and biomass to phytoplankton in overlying waters, and estimate the potential contribution
of BMA to the trophodynamics in this shallow, turbid, subtropical estuary. The estimates of BMA biomass (mean = 4.21 mg Chl
a m−2) for Galveston Bay were within the range of the reported values for similar Gulf of Mexico estuaries. BMA biomass in the
central part of the bay was essentially homogeneous, whereas biomass at the seaward and upper bay ends of the transect were
significantly lower. Peridinin, fucoxanthin, and alloxanthin were the three carotenoids with the highest concentrations, with
fucoxanthin having the highest mean concentration (1.82 mg m−2). The seaward and landward ends of the transect differed from the central region of the bay with respect to the relative
abundances of chlorophytes, cyanobacteria, and photosynthetic bacteria. Benthic microalgal community composition also showed
a gradual shift over time due to changes in the relative abundances of photosynthetic bacteria, cryptophytes, dinoflagellates,
and cyanobacteria. Major changes in community composition occurred in the spring months (March to April). On an areal basis,
BMA biomass in Galveston Bay occurred at minor concentrations (16.5%) relative to phytoplankton. Furthermore, the concentrations
of carotenoid pigments for phytoplankton and BMA (fucoxanthin, alloxanthin, and zeaxanthin) were correlated (r = 0.48 to 0.61), suggesting a close linkage between microalgae in the water column and sediments. The contribution of BMA
to the primary productivity of the deeper waters (>2 m) of Galveston Bay is probably very small in comparison to shallower
waters along the bay margins. The significant similarities in the community composition of phytoplankton and BMA illustrate
the potential importance of deposition and resuspension processes in this turbid, shallow estuary. 相似文献
16.
This study examined whetherMercenaria mercenaria (L.) (quahog) growth is influenced by variability in phytoplantkon community composition in the waters of Long Island, New York. Field studies conducted during 1999 and 2000 compared juvenile quahog growth and phytoplankton assemblages between West Sayville (WS), an embayment in Great South Bay along Long Island’s south shore where quahog landings have recently declined, and Oyster Bay (OB), an embayment on Long Island’s north shore where quahog landings are still high. Quahogs grew better at OB than WS during both study years. Centric diatoms were typically the dominant phytoplankton species at OB, and pennate diatoms and dinoflagellates characterized WS. At WS, the phytoplankton community consisted of heterotrophic dinoflagellates during a brown tide in 2000 and pennate diatoms afterward. Nanoflagellates were abundant (105–106 cells ml?1) at WS throughout the summer of 2000. Multiple regression analysis revealed a significant effect of site and temperature on individual clam biomass during both years, but brown tide was only significant during 2000. Biomass comparisons of dominant phytoplantkon taxa with laboratory physiology studies showed that 0B, with its abundance of centric diatoms, likely represented a more nutritional diet for quahogs than pennate diatoms, which were abundant at WS. Small flagellates, which were common at WS, may also have been important for sustaining growth during some months. Variability in plankton assemblages between OB and WS likely represented two distinct, diets that were critical influences on clam growth. 相似文献
17.
Wim J. Kimmerer Nissa Ferm Mary Helen Nicolini Carolina Peñalva 《Estuaries and Coasts》2005,28(4):541-550
Egg production of planktonic copepods, is commonly measured as a proxy for secondary production in population dynamics studies
and for quantifying food limitation. Although limitation of copepod egg production by food quantity or quality is common in
natural waters, it appears less common or severe in estuaries where food concentrations are often high. San Francisco Estuary,
California, has unusually low concentrations of chlorophyll compared to other estuaries. We measured egg production rates
of three species ofAcartia, with dominate the zooplankton biomass at salinity above 15 psu, on 36 occasions during 1999–2002. Egg production was determined
by incubating up to 40 freshly collected individual copepods for 24 h in 140 ml of ambient water. Egg production was less
than 10 eggs female−1 d−1 most of the year, but as high as 52 eggs female−1 d−1 during month-long spring phytoplankton blooms. Egg production was a saturating function of total chlorophyll concentration
with a mean of 30 eggs female−1 d−1 above a chlorophyll concentration of 12±6 mg chl m−3. We take chlorophyll to be a proxy for total food ofAcartia, known to feed on microzooplankton as well as phytoplankton. These findings, together with long-term records of chlorophyll,
concentration and earlier studies of abundance of nauplius larvae in the estuary, imply chronic food limitation ofAcartia species, with sufficient food for maximum egg production <10% of the time over the last 25 yr. These results may show the
most extreme example of food limitation of copepod reproduction in any temperate estuary. They further support the idea that
estuaries may provide suitable habitat forAcartia species by virtue of other factors than high food concentration. 相似文献
18.
Sylvia Bonilla Daniel Conde Luis Aubriot María del Carmen Pérez 《Estuaries and Coasts》2005,28(6):884-895
A survey was carried out to investigate the relationship of phytoplankton biovolume, structure, and species life strategies
with major abiotic factors in a subtropical choked coastal lagoon (34°33′S, 54°22′W) naturally connecting with the Atlantic
Ocean several times a year. Marine and limnetic influence areas were sampled on a monthly basis during two periods, one of
low rainfall and high conductivity (August 1996 to February 1998) and a second period with the opposite tendency (December
1998 to March 2000). Photosynthetically active radiation availability was high and reached the bottom (>1% of the incident
light), while dissolved inorganic nitrogen (0.6–18.4 μM), soluble reactive phosphorus (<0.3–2.7 μM), and reactive silica (5–386
μM) were highly variable. Life strategies were identified in the phytoplankton as a function of morphology. C-strategists,
invasive planktonic and epipelic species of small size, and R-strategists, mixing-dependent species of medium size, characterized
this permanently mixed system. High frequency of exchange with the ocean prevented high biomass accumulation. Phytoplankton
biomass was lower in the second period of high rainfall (2.3 and 1.1 mm3 1−1 for period 1 and 2 respectively). A canonical correspondence analysis showed that conductivity, nitrogen, phosphorus, and
silica were the main environmental variables explaining phytoplankton species composition patterns. During the first period,
Bacillariophyceae (mostly pennate species) and the potentially toxicPrococentrum minimum were dominant; during the second period a higher contribution of flagellates (Cryptophyceae, Euglenophyceae, Prasinophyceae,
and flagellates <7 μm) was found. Differences of phytoplankton biomass, main taxonomic groups, and strategies were found between
periods but not between limnic and marine areas, suggesting that hydrological dynamic is more relevant than seasonal and spatial
differences. 相似文献
19.
Haimanti Biswas Mitali Dey Dipnarayan Ganguly Tarun K. De Sandip Ghosh Tapan K. Jana 《Estuaries and Coasts》2010,33(2):384-394
Inter-annual variations of phytoplankton abundance and community organization were observed over a two-decade period along with the ancillary parameters at the land–ocean boundary associated with the Sundarban mangrove forest (21°32′ and 22°40′ N and 88°05′ and 89° E), along the NE Coast of the Bay of Bengal. The number of definable Bacillariophyceae species exceeded Dinophyceae taxa, and the total number of bloom-forming species declined from a maximum of ten in 2000 and a minimum of two in 2007. Blooms of the diatom Coscinodiscus radiatus were common in 2000 and 2007. Tide cycles and the onset of the monsoon season played important roles in diurnal and seasonal variability of phytoplankton. Phytoplankton biovolume showed seasonality, with the highest levels during post-monsoon periods and lowest levels during the monsoon period. Phytoplankton abundance was correlated to rainfall patterns, which may be altered by long-term changes in climate. 相似文献
20.
Yukinori Tani Fumiko Nara Yuko Soma Mitsuyuki Soma Nobuyasu Itoh Genki Inoue Matsumoto Atsushi Tanaka Takayoshi Kawai 《Quaternary International》2009,205(1-2):126
Past changes in phytoplankton assemblages in Lake Baikal over the last 4.5 Ma, both in population and composition, are inferred from the downcore profiles of the relatively stable chlorophyll derivatives steryl esters of pyropheophorbides a and b (steryl chlorine esters; SCEs) in the 0–200 m section of the BDP-98 drill core, supplemented by the data on biogenic silica (BSi) and total organic carbon (TOC) contents. SCEs-a and -b dominate among sedimentary chlorophyll derivatives in the BDP-98 sediments except for the upper few meters, indicating their high stability during diagenetic alteration of sediments. The depth (age) profiles of SCEs-a are consistent with BSi and TOC profiles and are interpreted as reflecting primary productivity of the lake in the past. Baikal proxies reveal close correlation with marine oxygen isotope records (MIS stratigraphy). These observations confirm that climate change in the northern hemisphere has been a primary factor controlling the total phytoplankton productivity in Lake Baikal during the last several million years.Among SCEs-a, C30 (dinostanol)-SCE-a, a marker of dinoflagellates was identified by GC–MS analysis. SCE-b, a marker of green algae, was identified by its UV–vis spectrum. The ratio of C30-SCE-a to total SCEs-a (TSCEs-a) was higher during 4.5–4.2 and 1.7–1.3 Ma, suggesting that dinoflagellates proliferated preferentially in those periods. The early Pleistocene maximum of this ratio corresponds to the broad minimum of diatom abundance previously suggested to have recorded a prolonged regional cooling. An abrupt increase in the SCE-b/TSCEs-a ratio was observed at 2.5–2.6 Ma, indicating that green algae containing chlorophyll b have proliferated in Lake Baikal during this period. This interval has also been suggested to contain evidence for a significant regional cooling based on minima of diatom abundance and BSi in sediments. The depth profile of C27Δ5 (cholesterol)-SCE-a relative to TSCEs-a showed a trend similar to that of BSi, suggesting that C27Δ5-SCE-a/TSCEs-a ratio is a potential marker of diatoms in Lake Baikal.Certain mismatches between the Lake Baikal profiles of biological indicators and the marine oxygen isotope records, as well as the slight temporal offsets between different Lake Baikal biological marker signals suggest that the regional component of climatic and/or lacustrine environmental changes also have played a role in determining the composition of the Lake Baikal Plio-Pleistocene phytoplankton assemblage. 相似文献