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1.
M. J. Dagg T. S. Bianchi G. A. Breed W. -J. Cai S. Duan H. Liu B. A. McKee R. T. Powell C. M. Stewart 《Estuaries and Coasts》2005,28(5):664-674
During June 2003, a period of mid level discharge (17,400 m−3 s−1), a parcel of water in the lower Mississippi River was sampled every 2 h during its 4-d transit from river km 362 near Baton
Rouge to km 0 at Head of Passes, Louisiana, United States. Properties measured at the surface during each of the 48 stations
were temperature, salinity, dissolved organic carbon (DOC), total dissolved nitrogen, dissolved macronutrients (NO3+NO2, PO4, Si(OH)4), chlorophylla (chla; three size fractions: < 5 μm, 5–20 μm, and > 20 μm) pigment composition by HPLC, total suspended matter (TSM), particulate
organic carbon (POC), and particulate nitrogen (PN). Air-water CO2 flux was calculated from surface water dissolved inorganic carbon and pH. During the 4 d transit, large particles appeared
to be settling out of the surface water. Concentrations of chla containing particles > 20 μm declined 37%, TSM declined 43%, POC declined 42% and PN declined 57%. Concentrations of the
smaller chla containing particles did not change suggesting only large particulate materials were settling. There was no measurable loss
of dissolved NO3, PO4, or Si(OH)4, consistent with the observation that chla did not increase during the 4-d transit. DOC declined slightly (3%). These data indicate there was little autotrophic or
heterotrophic activity in the lower Mississippi River at this time, but the system was slightly net heterotrophic. 相似文献
2.
P. V. Bhaskar Evonne Cardozo Asha Giriyan Anita Garg Narayan B. Bhosle 《Estuaries and Coasts》2000,23(5):722-734
Data on hydrography, nutrients, suspended particles, and sedimented particles were collected at weekly intervals from November to May during 1995 to 1997 at a station in the coastal waters of Dona Paula Bay, India. Suspended and sedimented particles were analyzed for total suspended matter (SPM), total sedimented particulate matter (TPM), particulate organic carbon (POC), particulate organic nitrogen (PON), chlorophylla (chla), and diatom abundance. Variations in hydrography and nutrients influenced the quantity and composition of sedimented particles. The TPM, POC, PON, and chla fluxes showed small-scale seasonal variations and were higher in the summer (February to May) than in the winter (November to January). Resuspension of carbon accounted for approximately 25% of the gross POC and was highest in April 1997 (45%). The mean net POC flux was 197±90 mg C m−2 d−1 and accounts for 4.6% of the TPM. The average C∶N (w∶w) ratio of the sedimented material was 13.2±6.6. The POC:chla ratio was relatively higher in the sedimented material as compared to the suspended material. The particulate carbon reaching the bottom sediment was 39% of the primary production. The low organic carbon concentration (approximately 0.1% of dry sediment) in the sediments implies that about 98% of the sedimented carbon was either consumed at the sedimentwater interface or resuspended/advected before it was finally buried into the sediments. 相似文献
3.
Using both the photosynthetically active chlorophylla (chla) content of the organic carbon fraction of suspended particulate matter (chla/POC) and the percentage of photosynthetically, active chla in fluorometrically measured chla plus pheophytina (% chla), we determined that under specified hydrodynamic conditions, neap-spring tidal differentiation in particle dynamics could
be observed in the Columbia River estuary. During summer time neap tides, when river discharge was moderate, bottom chla/POC remained relatively unchanged from riverine chla/POC over the full 0–30 psu salinity range, suggesting a benign trapping environment. During summertime spring tides, bottom
chla/POC decreased at mid range salinities indicating resuspension of chla-poor POC during flood-ebb transitions. Bottom % chla during neap tides tended to average higher than that during spring tides, suggesting that neap particles were more recently
hydrodynamically trapped than those on the spring tides. Such differentiation supported the possibility of operation of a
particle conveyor belt process, a process in which low-amplitude neap tides favor selective particle trapping in estuarine
turbidity maxima (ETM)., while high-amplitude spring tides favor particle resuspension from the ETM. Untrapped river-derived
particles at the surface would continue through the estuary to the coastal ocean on the neap tide; during spring tide some
particles eroded from the ETM would combine with unsettled riverine particles in transit toward the ocean. Because in tensified
biogeochemical activity is associated with ETM, these neap-spring differences may be critical to maintenance and renewal of
populations and processes in the estuary. Very high river discharge (15, 000 m3 s−1) tended to overwhelm neap-spring differences, and significant oceanic input during very low river discharge (5,000 m3 s−1) tended to do the same in the estuarine channel most exposed to ocean input. During heavy springtime phytoplankton blooms,
development of a thick bottom fluff layer rich in chla also appeared to negate neapspring differentiation because spring tides apparently acted to resuspend the same rich bottom
material that was laid down during neap tides. When photosynthetic assimilation numbers [μgC (μgchl,a)−1h−1] were measured across, the full salinity range, no neap-spring differences and no river discharge effects occurred, indicating
that within our suite of measurements the compositional distinction of suspended particulate material was mainly a function
of chla/POC, and to a lesser extent % chla. Even though these measurements suggest the existence of a conveyor belt process, proof of actual operation of this phenomenon
requires scalar flux measurements of chla properties in and out of the ETM on both neap and spring tides. 相似文献
4.
SeaWiFS ocean color measurements were used to investigate interannual, monthly, and weekly variations in chlorophylla (chla) on the Louisiana shelf and to assess relationships with river discharge, nitrate load, and hypoxia. During the study period
(2000–2003), interannual changes in shelf-wide chla concentrations averaged over January–July ranged from +57% to −33% of the 4-yr average, in accord with freshwater discharge
changes of +20% to −29% and nitrate load changes of +20% to −35% from the Mississippi and Atchafalaya Rivers. Chla variations were largest on the shelf between the Mississippi and Atchafalaya Deltas. Within this region, which corresponds
spatially to the area of most frequent hypoxia, lowest January–July mean chla concentrations (5.5 mg m−3 over 7,000 km2) occurred during 2000, the year of lowest freshwater discharge (16,136 m3 s−1) and nitrate load (55,738 MT N d−1) onto the shelf. Highest January–July mean chla concentrations (13 mg m−3 over 7,000 km2) were measured in 2002, when freshwater discharge (27,440 m3s−1) and nitrate load (101,761 MT N d−1) were highest and second highest, respectively. Positive correlations (R2=0.4–0.5) were found between chla and both fresh water and nitrate loads with 0 to 1 month lags, with the strongest relationships just west of the Mississippi
Delta. In 2001, unusually clear skies allowed the identification of distinct spring and summer chla blooms west of the Mississippi Delta 4–5 wk after peaks in river discharge. East of the delta, the chla concentrations peaked in June and July, following the seasonal reversal in the coastal current. A clear linkage was not detected
between satellite-measured chla and hypoxia during the 4-yr period, based on a time series of bottom oxygen concentrations at one station within the area
of most frequent hypoxia. Clear relationships are confounded by the interaction of physical processes (wind stress effects)
with the seasonal cycle of nutrient-enhanced productivity and are influenced by the prior year's nitrate load and carbon accumulation
at the seabed. 相似文献
5.
Analysis of 6 yr of monthly water quality data was performed on three distinct zones of Florida Bay: the eastern bay, central bay, and western bay. Each zone was analyzed for trends at intra-annual (seasonal), interannual (oscillation), and long-term (monotonic) scales. the variables TON, TOC, temperature, and TN∶TP ratio had seasonal maxima in the summer rainy season; APA and Chla, indicators of the size and activity of the microplankton tended to have maxima in the fall. In contrast, NO3 −, NO2 −, NH4 +, turbidity, and DOsat, were highest in the winter dry season. There were large changes in some of the water quality variables of Florida Bay over the study period. Salinity and TP concentrations declined baywide while turbidity increased dramatically. Salinity declined in the eastern, central, and western Florida Bay by 13.6‰, 11.6‰, and 5.6‰, respectively. Some of the decrease in the eastern bay could be accounted for by increased freshwater flows from the Everglades. In contrast to most other estuarine systems, increased runoff may have been partially responsible for the decrease in TP concentrations as input concentrations were 0.3–0.5 μM. Turbidity in the eastern bay increased twofold from 1991 to 1996, while in the central and western bays it increased by factors of 20 and 4, respectively. Chla concentrations were particularly dynamic and spatially heterogeneous. In the eastern bay, which makes up roughly half of the surface area of Florida Bay, Chla declined by 0.9 μg l−1 (63%). The hydrographically isolated central bay zone underwent a fivefold increase in phytoplankton biomass from 1989 to 1994, then rapidly declined to previous levels by 1996. In western Florida Bay there was a significant increase in Chla, yet median concentrations of Chla in the water column remained modest (∼2 μg l−1) by most estuarine standards. Only in the central bay did the DIN pool increase substantially (threefold to sixfold). Notably, these changes in turbidity and phytoplankton biomass occurred after the poorly-understood seagrass die-off in 1987. It is likely the death and decomposition of large amounts of seagrass biomass can at least partially explain some of the changes in water quality of Florida Bay, but the connections are temporally disjoint and the process indirect and not well understood. 相似文献
6.
Søren Laurentius Nielsen Kaj Sand-Jensen Jens Borum Ole Geertz-Hansen 《Estuaries and Coasts》2002,25(5):930-937
We present a comparative analysis of 1400 data series of water chemistry (particularly nitrogen and phosphorus concentrations), phytoplankton biomass as chlorophylla (chla) concentrations, concentrations of suspended matter and Secchi depth transparency collected from the mid-1980s to the mid-1990s from 162 stations in 27 Danish fjords and coastal waters. The results demonstrate that Danish coastal waters were heavily eutrophied and had high particle concentrations and turbid waters. Median values were 5.1 μg chla 1−1, 10.0 mg DW 1−1 of suspended particles, and Secchi depth of 3.6 m. Chlorophyll concentration was strongly linked to the total-nitrogen concentration. The strength of this relationship increased from spring to summer as the concentration of total nitrogen declined. During summer, total nitrogen concentrations accounted for about 60% of the variability in chlorophyll concentrations among the different coastal systems. The relationship between chlorophyll and total phosphorus was more consistant over the year and correlations were much weaker than encountered for total nitrogen. Secchi depth could be predicted with good precision from measurements of chlorophyll and suspended matter. In a multiple stepwise regression model with In-transformed values the two variables accounted for most of the variability in water transparency for the different seasons and the period March–October as a whole (c. 80%). We were able to demonstrate a significant relationship between total nitrogen and Secchi depth, with important implications for management purposes. 相似文献
7.
Hans J. Rick Silke Rick Urban Tillmann Uwe Brockmann Uwe Gärtner Claus Dürselen Jürgen Sündermann 《Estuaries and Coasts》2006,29(1):4-23
Within the KUSTOS program (Coastal Mass and Energy Fluxes-the Land-Sea Transition in the Southeastern North Sea) 28 to 36
German Bight stations were seasonally surveyed (summer 1994, spring 1995, winter 1995–1996) for light conditions, dissolved
inorganic nutrient concentrations, chlorophylla (chla), and photosynthesis versus light intensity (P:E) parameters. Combining P:E curve characteristics with irradiance, attenuation,
and chlorophyll data resulted in seasonal estimates of the spatial distribution of total primary production. These data were
used for an annual estimate of the total primary production in the Bight. In winter 1996 the water throughout the German Bight
was well mixed. Dissolved inorganic nutrient concentrations were relatively high (nitrogen [DIN], soluble reactive phosphorus
[SRP], and silicate [Si]: 23, 1, and 10 μM, respectively). Chla levels generally were low (< 2 μg l−1) with higher concentrations (4–16 μg l−1) in North Frisian coastal waters. Phytoplankton was limited by light. Total primary production averaged 0.2 g C m−2 d−1. Two surveys in April and May 1995 captured the buildup of a strong seasonal thermo-cline accompained by the development
of a typical spring diatom bloom. High nutrient levels in the mixed layer during the first survey (DIN, SRP, and Si: 46, 0.45,
and 11 μM, respectively) decreased towards the second survey (DIN, SRP, and Si: 30.5, 0.12, and 1.5 μM, respectively) and
average nutrient ratios shifted further towards highly imbalanced values (DIN:SRP: 136 in survey 1, 580 in survey 2; DIN:Si:
13.5 in survey 1, 96 in survey 2). Chla ranged from 2 to 16 μg l−1 for the first survey and rose to 12–50 μg l−1 in the second survey. Phytoplankton in nearshore areas continued to be light limited during the second survey, while data
from the stratified regions in the open German Bight indicates SRP and Si limitation. Total primary production ranged from
4.0 to 6.3 g C m−2 d−1. During summer 1994 a strong thermal stratification was present in the German Bight proper and shallow coastal areas showed
unusually warm (up to 22°C), mixed waters. Chla concentrations ranged from 2 to 18 μg l−1. P:E characteristics were relatively high despite the low nutrient regime (DIN, SRP, and Si: 2, 0.2, and 1.5 μM, respectively),
resulting in overall high total primary production values with an average of 7.7 g C m−2 d−1. Based on the seasonal primary production estimates of the described surveys a budget calculation yielded a total annual
production of 430 g C m−2 yr−1 for the German Bight. 相似文献
8.
Vishwas B. Khodse Narayan B. Bhosle V. V. Gopalkrishna 《Journal of Earth System Science》2009,118(2):147-156
Suspended particulate matter (SPM) of surface seawaters was collected during December 2003 to October 2004 at 10 stations
in the Bay of Bengal, and analyzed for particulate organic carbon (POC), total particulate nitrogen (TPN), total particulate
carbohydrate (TPCHO) and total particulate uronic acids (TPURA). The concentrations of POC, TPCHO and TPURA varied from 4.80
to 29.12, 0.85 to 4.24, 0.09 to 0.91 μM C, respectively. The TPCHO-C and TPURA-C accounted for 6.6–32.5% and 0.87–3.65% of
POC. The trends observed for the distribution of these compounds were generally similar to those recorded for the distribution
of chlorophyll a (Chl a). The C/N ratios varied from 3.2 to 22.3 with most of the values being < 10. This suggests that the organic matter was mostly
derived from phytoplankton and bacteria. Relatively low C/N ratios and high TPCHO yield imply that freshly derived organic
matter was present during SWM and FIM. Our data suggest that the quality and quantity of organic matter varied spatially and
seasonally. 相似文献
9.
Although marine lagoons are ubiquitous features along coastal margins, studies investigating the dynamics of metal, organic
matter, and nutrient concentrations in such systems are rare. Here we present a comprehensive examination of the temporal
and spatial gradients in dissolved trace metals (Ag, Cd, Cu, Mn, Pb), organic and inorganic nutrients (POC, PON, DOC, N03
−, NH4
+, H4SiO4, PO4
−3, and urea), and algal biomass in a lagoon estuary, Great South Bay (GSB), New York, USA. While this estuary has experienced
a series of environmental problems during recent decades (urbanization, loss of fisheries, harmful algal blooms), root causes
are largely unknown, in part because levels of bioactive substances, such as trace metals, have never been measured. Sampling
was undertaken within multiple estuarine, riverine, and groundwater sites during spring, summer, and fall. Trace metal tracers
(e.g., Ag, Mn) and statistical analyses were used to differentiate the influences of natural and anthropogenic processes on
the chemical composition of the lagoon. Our analyses revealed three clusters of biogeochemical constituents that behaved similarly
in GSB: constituents under strong biological control such as POC, PON, DOC and chlorophyll,a; elements indicative of benthic remobilization processes such as Mn, Cd, and Cu; and constituents strongly influence by anthropogenic
processes such as Ag, Pb, PO4
−3, NO3
−, and NH4
+. Although GSB is surrounded by a densely populated watershed (c. 1 million people), it does not appear to be significantly
contaminated by trace metals compared to other urban estuaries. Levels of DOC (up to 760 μM) in GSB were well correlated with
phytoplankton biomass and exceeded at least 98% of values reported in similar mid Atlantic estuaries at the same salinities.
These high levels of DOC are likely to be an important source of carbon export to the coastal ocean and likely promote mixotrophic
harmful algal blooms in this system. 相似文献
10.
Long-Term and Seasonal Changes in Nutrients,Phytoplankton Biomass,and Dissolved Oxygen in Deep Bay,Hong Kong 总被引:1,自引:0,他引:1
Jie Xu Kedong Yin Joseph H. W. Lee Hongbin Liu Alvin Y. T. Ho Xiangcheng Yuan Paul J. Harrison 《Estuaries and Coasts》2010,33(2):399-416
Deep Bay is a semienclosed bay that receives sewage from Shenzhen, a fast-growing city in China. NH4 is the main N component of the sewage (>50% of total N) in the inner bay, and a twofold increase in NH4 and PO4 concentrations is attributed to increased sewage loading over the 21-year period (1986–2006). During this time series, the
maximum annual average NH4 and PO4 concentrations exceeded 500 and 39 μM, respectively. The inner bay (Stns DM1 and DM2) has a long residence time and very
high nutrient loads and yet much lower phytoplankton biomass (chlorophyll (Chl) <10 μg L−1 except for Jan, July, and Aug) and few severe long-term hypoxic events (dissolved oxygen (DO) generally >2 mg L−1) than expected. Because it is shallow (~2 m), phytoplankton growth is likely limited by light due to mixing and suspended
sediments, as well as by ammonium toxicity, and biomass accumulation is reduced by grazing, which may reduce the occurrence
of hypoxia. Since nutrients were not limiting in the inner bay, the significant long-term increase in Chl a (0.52–0.57 μg L−1 year−1) was attributed to climatic effects in which the significant increase in rainfall (11 mm year−1) decreased salinity, increased stratification, and improved water stability. The outer bay (DM3 to DM5) has a high flushing
rate (0.2 day−1), is deeper (3 to 5 m), and has summer stratification, yet there are few large algal blooms and hypoxic events since dilution
by the Pearl River discharge in summer, and the invasion of coastal water in winter is likely greater than the phytoplankton
growth rate. A significant long-term increase in NO3 (0.45–0.94 μM year−1) occurred in the outer bay, but no increasing trend was observed for SiO4 or PO4, and these long-term trends in NO3, PO4, and SiO4 in the outer bay agreed with those long-term trends in the Pearl River discharge. Dissolved inorganic nitrogen (DIN) has
approximately doubled from 35–62 to 68–107 μM in the outer bay during the last two decades, and consequently DIN to PO4 molar ratios have also increased over twofold since there was no change in PO4. The rapid increase in salinity and DO and the decrease in nutrients and suspended solids from the inner to the outer bay
suggest that the sewage effluent from the inner bay is rapidly diluted and appears to have a limited effect on the phytoplankton
of the adjacent waters beyond Deep Bay. Therefore, physical processes play a key role in reducing the risk of algal blooms
and hypoxic events in Deep Bay. 相似文献
11.
Seasonal changes in the abundance and composition of plant pigments in particulate organic carbon in the lower Mississippi and Pearl Rivers 总被引:1,自引:0,他引:1
Plant pigments in particulate organic carbon were examined in the lower Mississippi and Pearl Rivers (U.S.), along with physical
variables and nutrients to study seasonal changes in the abundance and composition of phytoplankton. Water samples were collected
monthly from September 2001 to August 2003 in the lower Mississippi River (MR; no samples were taken in February 2002) and
from August 2001 to July 2003 in the Pearl River (PR). High concentrations of total suspended solids (TSS), nutrients, and
chlorophylla (chla; dominated by diatoms) were observed in the lower MR. The smaller blackwater PR was characterized by lower nutrients and
chla, higher ultraviolet absorbance, and a phytoplankton biomass dominated by chlorophytes. Chla concentrations in the lower MR was high in summer low-flow periods and also during interims of winter and spring, and did
not couple with physical variables and nutrients, likely due to a combination of in situ production and inputs from reservoirs,
navigation locks and oxbow lakes in the upper MR and Missouri River. Chla concentrations in the PR was only high in summer low-flow periods and were controlled by temperature and concentrations of
chromophoric dissolved organic matter 9CDOM). The high, diatom-dominated phytoplankton biomass in the lower MR was likely
the result of decreasing TSS (increased damming in the watershed) and increasing nutrients (enhanced agricultural runoff)
over the past few decades. Lower phytoplankton biomass (dominated by chlorophytes) in the PR was likely linked with intense
shading by CDOM and lower availability of nutrient inputs. An increase in the relative importance of phytoplankton biomass
in large turbid rivers, such as the MR, could have significant effects on the age and lability of riverine organic matter
entering the ocean, the stoichiometric balance of nutrients delivered to coastal margins, and the sequestration of atmospheric
CO2 in these dynamic regions. 相似文献
12.
An 11-month observation of dissolved and particulate organic matter, chlorophyll a(Chl a), C18 Sep-Pak extractable hydrophobic dissolved organic matter (hDOM) fraction and associated dissolved trace metals (Cd,
Cu, V, Co, Ni, Mo, U) was performed in the Lot–Garonne River system. This system includes the Riou Mort, the Lot River and
the downstream reaches of the Garonne River and represents the fluvial transport path of trace metals between the major point
source of polymetallic pollution, located in the Riou Mort watershed and the Gironde estuary. Spatial and temporal variations
of dissolved and particulate organic carbon and Chl areflect the presence of different types of organic matter and their relation with the hDOM fraction. Maximum Chl a/POC ratios (up to 0.03), indicate intense phytoplankton production from March to May. In the Lot River (Temple), DOC and
POC concentrations were clearly higher and mean Chl a concentration (2.8 mg g−1) was about three times higher than those of the other sites. High Chl a/POC ratios suggest high phytoplankton activity with maxima in spring and late summer. In the Riou Mort River, very high POC
concentrations of up to 40 (mean: 20) occurred, whereas Chl a concentrations were relatively low indicating low phytoplankton activity. High, strongly variable DOC and POC concentrations
suggest important natural (Carboniferous soils, forests) or anthropogenic (e.g., former coal mines, waste areas, agriculture,
sewage) carbon sources within the small Riou Mort watershed. Despite high DOC concentrations in the Riou Mort River, hDOM
metal fractions were generally lower than those at the other sites. The general order of decreasing binding strength between
metals and the organic hydrophobic phase (Cu, U > Co, Ni > V, Mo > Cd) at all four sites was in good agreement with the Irving–William
series of transition element affinity towards organic ligands. Accordingly, the role of the hydrophobic phase in dissolved
Cd transport appeared to be negligible, whereas the hDOM–Cu fraction strongly contributed to dissolved Cu transport. 相似文献
13.
Peter G. Verity 《Estuaries and Coasts》2002,25(5):944-960
The Skidaway River estuary is a tidally-dominated subtropical estuary in the southeastern USA surrounded by extensiveSpartina salt marshes. Weekly smapling at high and low tide began in 1986 for hydrography, nutrients, chlorophylla, particulate matter, and microbial and plankton biomass and composition; hydrographic and nutrient data during 1986–1996
are reported here. Salinity varied inversely with river discharge and exhibited variability at all time scales but with no
long-term trend. Water temperature typically ranged over 25°C and was without apparent long-term frend. Seasonal cycles in
concentrations of NO3, NH4, PO4, Si(OH)4, and DON were observed, with annual maxima generally occurring in late summer. Superimposed on seasonal cycles, all five
nutrients exhibited steady increases in minimum, mean, and maximum concentrations; mean concentrations increased c. 50–150%
during the decade. Nutrient concentrations were highly correlated with water temperature over the ten-year period, but weakly
related to salinity and discharge. Nutrients were strongly correlated with one another, and the relative ratios among inorganic
nutrients showed little long-term trend. Correlations among temperature and nutrient concentrations exhibited considerable
inter-annual variability. Major spikes in organic and inorganic nutrient concentrations coincided with significant rainfall
events; concentrations increased hyperbolically with rainfall. Although pristine compared to more heavily impacted waterways
primarily outside the region, residential development and population density have been increasing rapidly during the past
15–20 years. Land use is apparently altering nutrient loading over the long-term (months-years), and superimposed on this
are stochastic meteorological events that accelerate these changes over the short term (days-weeks). 相似文献
14.
Nicholas B. Handler Adina Paytan Christopher P. Higgins Richard G. Luthy Alexandria B. Boehm 《Estuaries and Coasts》2006,29(5):860-870
To elucidate relationships between land cover and water quality along the central California coast, we collected monthly samples
from 14 coastal waterway outlets representing various degrees of human development. Sites were distributed between three salinity
categories, freshwater, estuarine, and marine, to better understand land cover-water quality relationships across a range
of coastal aquatic ecosystems. Samples were analyzed for fecal indicator bacteria (FIB), dissolved nutrients, stable nitrogen
isotopes in particulate organic matter, and chlorophylla (chla). Sediment samples from 11 sites were analyzed for the concentration of the anthropogenic organic contaminant perfluorooctane
sulfonate and its precursors (ΣPFOS). While the data indicated impairment by nutrient, microbial, and organic contaminants
at both agricultural and urban sites, the percentage of agricultural land cover was the most robust indicator of impairment,
showing significant correlations (p<0.05) to FIB, nutrient, chla, and ΣPFOS levels. FIB densities were strongly influenced by salinity and were highest at sites dominated by agriculture
and urbanization. Nutrient levels and chla correlated to both agricultural and urban land use metrics as well. Positive correlations among FIB, nutrients, chla, and ΣPFOS suggest a synergy between microbial, nutrient, and organic pollution. The results emphasize the importance of
land management in protecting coastal water bodies and human health, and identify nutrient, microbial, and organic pollution
as prevalent problems in coastal California water bodies. 相似文献
15.
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
16.
Particulate organic carbon (POC) was measured for 77 water samples collected over a 3000 m water column along 88° E in the
central Bay of Bengal. The POC values varied from 80 to 895 μg per litre at the surface and 171 to 261 μg per litre at 2000
m. The POC decreased with increasing water depth at all the stations. Deep water concentrations of POC were higher than those
reported from other oceanic waters. Distribution of POC was not influenced by water masses. The POC was not significantly
correlated with chlorophylla. 相似文献
17.
Paleoproterozoic carbonaceous shales in the Tim-Yastrebovskii ancient rift, which underwent zonal metamorphism at 350–550°C,
contain REE mineralization of silicates (allanite, thorite, and Ce-P huttonite) fluorcarbonates (bastnaesite and synchysite),
phosphates (monazite and xenotime), and REE-bearing apatite. The reason for the wide occurrence of bastnaesite and other REE
minerals is relatively high REE concentrations in the sulfide-bearing carbonaceous shales, with these elements accumulated
in the organic matter in the course of diagenesis. Reaction textures with REE-bearing chlorite, bastnaesite, and allanite
suggest that REE-bearing chlorite and bastnaesite provided REE for the forming of higher temperature allanite and monazite.
This is corroborated by the REE patterns of the monazite, allanite, and bastnaesite, which are almost identical and are characterized
by the strong predominance of LREE. The replacements of REE minerals during metamorphism at 350–550°C took place via a number
successive transitions: (1) Mnz → Aln, Chl
REE → Bst, Chl
REE → Aln, Bst → Aln and (2) Bst → Mnz and Ap
LREE → Mnz. These replacements can be accounted for by prograde metamorphic reactions. 相似文献
18.
Seasonal phosphate (Pi) uptake kinetics were determined using chambers encompassing the water column, sediment and the entire
system (water column + sediment + seagrass/epiphyte) in Florida Bay (FB) during 2003–2006 and on the Little Bahama Bank (LBB)
during a cruise June, 2004. Pi uptake was a linear function of concentration at low Pi levels (< 2 μmo11-1). Applying the Pi system rate constant (Sp) from western (177 ±50 x 10-6 m s-1) and eastern (272 ±66 x 10-6 m s-1) bay sites, and using Pi measured during the study (0.02 to 0.177 μmol Pi 1-1), we calculated a Pi uptake rate of 0.30 to 2.62 mmol Pi m-2 d-1 for western and 0.47 to 4.16 mmol Pi m-2 d-1 for eastern bay sites which includes phytoplankton uptake (0.455 m height). During non-bloom conditions, phytoplankton dominated
Pi uptake in the east (46%) and both phytoplankton and the seagrass-epiphyte consortium in the west (32 and 52%, respectively),
with a smaller contribution by the sediment (15–20%). On LBB interior sites, the water column always dominated (≽94%) Pi uptake
with a higher Sp (573-881 x 10-6 m s-1) than FB. During cyanobacterial blooms in FB (chla 17 μg 1-1), the water column dominated Pi uptake (100%) and Sp was the highest (>2,800 x 10-6 m s-1) measured. Phytoplankton accounted for 88% of this sequestered Pi with only 12% in the acid extractable fraction, likely
as calcium bound and/or adsorbed P, and only 1% attributable to small heterotrophs. When chl α levels declined (2 μg I-1) Pi uptake was still dominated by phytoplankton (77%), the acid extractable pool increased (18%) and the heterotrophic community
became more important (22%). In carbonate-dominated seagrass systems, Pi is primarily taken up by the water column biota and
is subsequently remineralized/hydrolyzed in the water column or settles to the benthos where it becomes available to benthic
primary producers. 相似文献
19.
Trends in the spatial distribution of chlorophylla (chla) and colloidal and total carbohydrates on the Molenplaat tidal flat in the Westerschelde estuary, Netherlands, reflected spatial differences in physical properties of the sediment. Results from a Spearman Rank Order Correlation indicated that many of the physical and biological measures covaried. Multiple regression analyses describing the relationship between colloidal carbohydrates and sediment properties resulted in several highly significant equations, although in all cases chla was able to predict colloidal carbohydrate content. Relationships between sediment surface chla and colloidal carbohydrate, and sediment erodibility (i.e., critical erosion threshold, Ucrit, and mass of sediment eroded at a velocity of 30 cm s?1) determined in annular flume experiments were examined. Overall sediment erodibility was lowest (i.e., high thresholds, low mass eroded) for the siltiest sediments in June 1996 when chla and colloidal carbohydrates were high (56.9 μg gDW?1 and 320.6 μg gluc.equ. gDW?1, respectively), and greatest (i.e., low thresholds, high mass eroded) at the sandier sediments in September 1996, when chla and colloidal carbohydrates were low (1.0 μg gDW?1 and 5.7 μg gluc.equ. gDW?1, respectively). When sediments were grouped according to relative silt content, the most significant relationships were found in muddy sand with a finegrained fraction (<63 μm) of 25–50%. Thresholds of erosion increased, while mass of sediment eroded decreased, with increasing chla and colloidal carbohydrate. A similar trend was observed for the sand-muddy sand (63 μm 10–25%). In the sand (63 μm 0–10%), there were no relationships for Ucrit, whereas mass eroded appeared to increase with increasing chla and colloidal carbohydrate. The increased carbohydrate may stick sand grains together, altering the nature of erosion from rolling grains to clumps of resuspension. 相似文献
20.
We investigated whether climate change results in long-term changes in phytoplankton biomass and phenology in a turbid eutrophic
coastal plain estuary. Changes in annual mean chlorophyll a (chla) concentrations were studied for the period 1978–2006 in the eutrophic and turbid macro-tidal Western Scheldt estuary. Three
stations were investigated: WS1, at the mouth of the estuary; station WS6, halfway up the estuary; and station WS11, near
the Dutch–Belgian border near the upstream end of the estuary. No significant long-term changes in yearly averaged chla concentrations were observed in WS1 and WS6, but in WS11 the phytoplankton biomass decreased considerably. This is most likely
due to an increase in grazing pressure as a result of an improvement in the dissolved oxygen concentrations. Spectral analyses
revealed a possible periodicity of 7 years in the mean chla which was related to periodicity in river discharge. We also observed strong phenological responses in the timing of the
spring/summer bloom which were related to a well-documented increase in the temperature in the estuary. The fulcrum, the center
of gravity or the day at which 50% of the cumulative chla was reached during the year, advanced by 1–2 days/year. A similar trend was observed for the month in which the maximum bloom
was observed, with the exception of station WS1. All stations showed an earlier initiation of the bloom, whereas the day at
which the phytoplankton bloom was terminated also moved forward in time excepted for WS11. As a result, the bloom length decreased
at station WS1, remained the same at station WS6, and increased at WS11. This complicated pattern in bloom phenology demonstrates
the complex nature of ecosystem functioning in estuaries. 相似文献