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1.
Thomas Nielsen 《Journal of experimental marine biology and ecology》2003,293(1):73-88
Rhizophora apiculata leaf litter decomposition and the influence of this process on phosphorus (P) dynamics were studied in mangrove and sand flat sediments at the Bangrong mangrove forest, Phuket, Thailand. The remaining P in the mangrove leaf litter increased with time of decomposition to 174% and 220% of the initial amount in the litter in sand flat and mangrove sediment, respectively, although about 50% of the dry weight had been lost. The incorporation of P into the litter was probably associated with humic acids and metal bridging, especially caused by iron (Fe), which also accumulated in considerable amounts in the litter (5-10 times initial concentration). The addition of leaves to the sediment caused increased concentrations of dissolved reactive phosphate (DRP) in the porewater, especially in sand flat sediment. The DRP probably originated from Fe-bound P in the sediment, because decomposition of buried leaf litter caused increased respiration and reduced the redox potential (Eh) in the sediments. Binding of P to refractory organic material and oxidized Fe at the sediment-water interface explains the low release of DRP from the sediment. This mechanism also explains the generally low DRP concentration in the mangrove porewater, the low nutrient content of the R. apiculata leaves, but also the higher total sediment P concentration of the mangrove sediment as compared to sediments outside the mangrove. Both the low release rates for DRP from the sediment and the accumulation of P associated with leaf litter decomposition tend to preserve P in the sediments. 相似文献
2.
Jack J. Middelburg Joop Nieuwenhuize Frederik J. Slim Boaz Ohowa 《Biogeochemistry》1996,34(3):133-155
The biogeochemistry of mangrove sediments was investigated in several mangrove forest communities in Gazi Bay, a coastal lagoon in Kenya, Africa. Carbon dioxide fluxes, sediment median grain sizes, sedimentary organic carbon, nitrogen and phosphorus contents and pore-water characteristics (ammonium, nitrate, sulfate and chloride) could be related to forest type. Mangrove sediments have pH values that range from 3.5 to 8.3 due to the limited buffer capacity of these sediments and intense acidifying processes such as aerobic degradation of organic matter, oxidation of reduced components, ammonium uptake by roots and root respiration. The mangrove sediments are nitrogen-rich compared to mangrove litter, as a result of microbial nitrogen retention, uptake and fixation, and import of nitrogen-rich material. It appears that mangrove sediments in Gazi Bay act as a nutrient and carbon sink rather than as a source for adjacent seagrass and reef ecosystems. 相似文献
3.
We analyzed 144 composite sediment samples to appraise the seasonal variation in select major nutrients in the bed sediments
of Keoladeo National Park (KNP), Bharatpur, a subtropical monsoonal wetland system in India, from September 2003 to July 2005.
Total organic carbon (TOC, %) and total nitrogen (TN, %) in the sediments were in the range of 0.61–14.01 and 0.26–0.68, respectively.
The total available phosphorus (TAP, %) and total available sulphur (TAS, %) ranged from 0.001 to 0.034 and from 0.001 to
0.012, respectively. While C:N ratio was within a narrow range (1.38–13.56), C:P ratios varied widely (18.81–5995.83). Similar
wide variations were seen in C:S ratio (352.2–3929.5) as well as N:P ratio (9.34–56.6). All the parameters except TAS showed
depth-wise declines along the sediment profile. In contrast, the pH gradually increased along the depth. Most of the parameters
significantly varied across months and sediment layers. A positive correlation (Two-tailed, P < 0.05) existed between TOC and all the nutrients and their ratios except TAP and N:P. TAP was positively correlated with
electrical conductivity (EC) and water soluble substances (WSS), suggesting the contribution of phosphate to the dissolved
salts. During certain months elements such as P were comparatively low in concentration, in spite of input through agricultural
runoff and large scale bird droppings, probably due to its higher uptake by macrophytes growing luxuriantly in the wetland.
Organic materials appear to decay at a faster rate during the drier periods as indicated by the fall in TOC and the rise in
TN. Principal Component Analysis (PCA) shows that three components contributed to 68.9% of the total variance. The first component
that accounted for 26.4% of the total variance reflects the importance of total organic carbon in wetland sediments and the
ratio of carbon to other nutrients. The second one accounting for 23.7% of the variance correlated with water soluble substances
(EC, WSS and TAS). The third component accounting for 18.7% of the variance reflects the influence of two major nutrients,
nitrogen and phosphorus, in sediments those affect the biogeochemical processes in wetlands. Thus, the three PCA components
can be characterized as ‘sediment organic carbon and its ratios with other elements’, ‘WSS, TAS’ and ‘the limiting nutrients
such as N and P’, respectively. 相似文献
4.
The Dutch Wadden Sea: a changed ecosystem 总被引:12,自引:4,他引:8
Since 1600 the surface area of the Dutch Wadden Sea decreased considerably by successive reclamations of saltmarshes. In 1932
the Zuiderzee (3200 km2) was closed off from the Wadden Sea causing in the remaining part an increase in tidal range and current velocities. In 1969
the Lauwerszee (91 km2) was closed off and turned into a freshwater lake as well. Man's use of the Wadden Sea changed simultaneously. Dredging in
harbours and shipping routes, and extraction of sand and shells became common practice. Extraction of sand increased manifold
between 1960 and 1985. These activities did contribute to the turbidity of the Wadden Sea water. Discharge of nitrogen and
phosphorus compounds into the western Wadden Sea increased also manifold since 1950, causing an increase in phytoplankton
production, duration of phytoplankton blooms, and intertidal macrozoobenthic biomass. Loads of metals and organochlorine contaminants
entering the Wadden Sea were hard to estimate.
Fisheries changed drastically since the 1930's. Fishing for ‘Zuiderzee’ herring came to an end shortly after closing off the
Zuiderzee. The anchovy fishery ceased in the 1960’, that for flounder in 1983. Undersized brown shrimps were fished until
1971. Selective shrimptrawls and sorting devices with flushing seawater were introduced to reduce mortality among young flatfish
and shrimps. Oysters became extinct in the 1960's due to over-exploitation of the natural beds. Production of mussels increased
more than ten times between 1950 and 1961 due to ‘culturing’, catches of cockles increased slowly between 1955 and 1984. Whelks
were fished until 1970.
The most important changes in the biotic system of the Wadden Sea, increased production of microalgae and intertidal macrozoobenthos,
can be attributed to increased nutrient loads. Eutrophication provided ample food supply for mussels which are harvested mainly
by man and eider duck, and may have caused also increased growth in juvenile plaice. Increased turbidity may have impaired
life conditions for adult dab, and have presented also recovery of sublittoral eelgrass beds after their disappearance in
the 1930's due to the ‘wasting disease’. Increased turbidity in the Wadden Sea is probably caused by closing off the Zuiderzee
(1932), a significant increase of dredge spoil disposal near Hoek van Holland between 1970 and 1983, and a more than 10-fold
increase of mussel culturing in the Wadden Sea since 1950. Stocks of several bird species breeding in the Wadden Sea area
suffered great losses in the early 1960's due to a pesticide accident. Most of the breeding populations have recovered. PCB's
caused a reproduction failure among harbour seals in the 1970's.
Since 1980 official Dutch policy aims at multiple use of the Wadden Sea, with emphasis on protection and restoration of the
natural environment. The 3rd Water Management Plan (1989) aims at a development of the Wadden Sea ecosystem towards the situation
of ca. 1930, i.e. without undoing present sea dikes and reclaimed polders. Management of the Dutch Wadden Sea will therefore
have to focus mainly on reduction of eutrophication, pollution and turbidity. Some management options are discussed. 相似文献
5.
Flux of organic carbon in a riverine mangrove wetland in the Florida Coastal Everglades 总被引:1,自引:1,他引:0
Melissa M. Romigh Stephen E. Davis III Victor H. Rivera-Monroy Robert R. Twilley 《Hydrobiologia》2006,569(1):505-516
Short-term (daily) and seasonal variations in concentration and flux of dissolved organic carbon (DOC) were examined over
15 tidal cycles in a riverine mangrove wetland along Shark River, Florida in 2003. Due to the influence of seasonal rainfall
and wind patterns on Shark River’s hydrology, samplings were made to include wet, dry and transitional (Norte) seasons. We
used a flume extending from a tidal creek to a basin forest to measure vertical (vegetated soil/water column) and horizontal
(mangrove forest/tidal creek) flux of DOC. We found significant (p < 0.05) variations in surface water temperature, salinity, conductivity, pH and mean concentration of DOC with season. Water
temperature and salinity followed seasonal patterns of air temperature and rainfall, while mean DOC concentration was highest
during the dry season (May), followed by the wet (October) and ‘Norte’ (December) seasons. This pattern of DOC concentration
may be due to a combination of litter production and inundation pattern of the wetland. In contrast to daily (between tides)
variation in DOC flux between the mangrove forest and tidal creek, daily variations of mean water quality were not significant.
However, within-tide variation of DOC flux, dissolved oxygen content and salinity was observed. This indicated that the length
of inundation and water source (freshwater vs. saltwater) variation across tidal cycles influenced water quality and DOC flux
in the water column. Net DOC export was measured in October and December, suggesting the mangrove forest was a source of DOC
to the adjacent tidal creek during these periods. Net annual export of DOC from the fringe mangrove to both the tidal creek
and basin mangrove forest was 56 g C m−2 year−1. The seasonal pattern in our flux results indicates that DOC flux from this mangrove forest may be governed by both freshwater
discharge and tidal range. 相似文献
6.
Holmer M. Andersen F.Ø. Holmboe N. Kristensen E. Thongtham N. 《Wetlands Ecology and Management》2001,9(2):141-158
Benthic primary production and nutrient dynamics were examined along a transect in the Bangrong mangrove forest in Thailand.
Six stations were established extending from a high-intertidal site within the mangrove forest to low-intertidal flats and
seagrass beds in front of the mangrove forest. Benthic processes (O2 and CO2 fluxes) and nutrient dynamics (mineralization, sediment-water fluxes, pore water and sediment pools) were measured under
light and dark conditions during wet and dry seasons over a 2-yr period. The sediments were mostly autotrophic, only the mangrove
forest sites were net heterotrophic during the wet season. Maximum daily net primary production was found at the non-vegetated
tidal flats (40–75 mmol O2 m-2d-1), where light and nutrient availability were highest. The variation in benthic mineralization along the transect was minor
(1.6–4.3 mmol CO2 m-2h-1) and did not reflect the large changes inorganic matter content (organic carbon: 0.7–4.2% DW) and quality (C:N ratio varied
from 25 to 100), suggesting that the mineralizable pool of organic matter was of similar magnitude at all sites. There was
only minor seasonal variation in rates of mineralization. The net primary production showed more variation with lower rates
in the mangrove forest (reduced with 74%) and higher rates at the tidal flats (increased with 172%) and in the seagrass beds
(increased with 228%) during the wet season. The nutrient pools and fluxes across the sediment-water interface were generally
low along the transect, and the sediments were efficient in retaining nitrogen in the nutrient limited mangrove/seagrass environment.
Pools and fluxes of phosphorus were generally very low suggesting that benthic primary production was phosphorus limited along
the transect.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
7.
J. I. Saiz F. J. García M. E. Manjón-Cabeza J. Parapar A. Peña-Cantero T. Saucède J. S. Troncoso A. Ramos 《Polar Biology》2008,31(6):735-743
The structure and spatial distribution of the macrofauna community of the Bellingshausen Sea in the western sector of Antarctica
was studied during the ‘BENTART–06’ oceanographic expedition. This is one of the least explored Antarctic seas. A total of
20 box cores were sampled at 11 stations ranging from 157 to 3,304 m depth, using an USNEL-type box corer (BC) dredge. Representatives
of 25 higher taxa of invertebrates were collected. Deeper sampling sites were less rich in taxa (4–7 taxa), whereas the figures
were higher at shallower sites (up to 17 taxa). Faunal density on the sea bottom revealed a horizontal spatial gradient from
the western sites with extremely low figures (90 indiv./m2) towards the eastern ones with the highest figures (1,360 indiv./m2) close to the Antarctic Peninsula. Several abiotic factors (depth, redox, organic matter, carbonates and particle size of
surficial sediments) were measured simultaneously on the sea floor to characterise the substrate preferences of the fauna.
Positive correlations were found between the faunal distribution and a combination of depth, redox values, and organic matter
content of sediments. This indicates decreasing availability of food in the deeper bottoms of the Bellingshausen Sea with
a prevalence of depauperated bottoms dominated almost exclusively by a foraminiferans community. 相似文献
8.
Concentrations of sediment organic nitrogen, dissolved inorganic nitrogen (ammonium, nitrite and nitrate), and dissolved organic
nitrogen (DON) in sediments were measured at two sites in a eutrophic estuarine lagoon. One is a shallow aerobic site where
macrobenthos are abundant and the other is a deep anaerobic site devoid of macrobenthos. Four species of macrobenthos (Bivalvia:
Corbicula japonica, Annelida: Notomastus sp., Neanthes japonica and Oligochaeta sp.) were found in 8 sandy sediment cores
collected at a shallow site in three succcessive summers. DON (170–1500 μg atom N l-1) was the major constituent of dissolved
nitrogen with 10 times greater concentration than ammonium (55–180 μg atom N l-1) and 1000 times greater than nitrate (0.14–5.9
μg atom N l-1) and nitrite (0.21–1.4 μg atom N l-1). The ammonium content in anaerobic muddy sediments at the deep site (210–350
μg atom N l-1) was higher than in aerobic sandy sediments, whereas DON was higher in aerobic sediments than anaerobic sediments
(90–240 μg atom N l-1). In aerobic sediments, depth profiles of DIN were nearly constant whereas DON was mostly highest at
the surface. On the other hand, the increase of DON and ammonium was observed where macrobenthos was found. The occurrence
of macrobenthos and high content of DON and ammonium content in the layers of sediment may suggest the influence of macrobenthos
in the partitioning of nitrogen species through their motion and excretion.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
9.
Characterization of phosphorus fractions in the sediments of a tropical intertidal mangrove ecosystem 总被引:2,自引:0,他引:2
Solid phases of phosphorus fractions in the surface and core sediments were studied to understand the biogeochemical cycling
and bioavailability of phosphorus in the Pichavaram intertidal mangrove sediments of India. Total P in surface and core sediments
ranged between 451–552 and 459–736 μg g−1 respectively and Fe bound P was the dominant fraction. Low levels of Fe bound P in the mangrove zone than the two estuarine
zones may be because of high salinity inhibition of phosphate adsorption onto the Fe-oxides/hydroxides. Post-depositional
reorganization of P was observed in surface sediments, converting organic P and Fe bound P into the authigenic P. High levels
of organic P in the mangrove zone is primarily due to intensive cycling and degradation of organic matter and adsorption of
phosphate on the organic molecules. The burial rates and regeneration efficiency of P in the intertidal mangrove ecosystem
ranged from 5.41 to 7.27 μmol P cm−2 year−1 and 0.122 to 0.233 μmol P cm−2 year−1, respectively. High burial efficiency (≈99%) of P proves the earlier observation of limiting nature of P for the biological
productivity. Further, bioavailable P (exchangeable P + Fe bound P + organic P) constituted a considerable proportion of sedimentary
P pool of which an average accounted for 55 and 50% in surface and core sediments respectively. The results indicate that
significant amount of P is locked in sediments in the form of authigenic P and detrital P which makes P as a limiting nutrient
for the biological productivity. 相似文献
10.
Geochemical partitioning and bioavailability of copper to aquatic plants in an artificial oxide-organic sediment 总被引:2,自引:0,他引:2
This study investigated the effects of competition between binding substrates (organic matter and iron oxide) and between
metals (cadmium and copper), on the partitioning of sedimentary copper and its subsequent bioavailability to an aquatic plant.
Organic matter and a synthesized iron oxide, ferrihydrite, were added singly and in combination to a series of sand sediments,
which were then dosed with environmentally realistic concentrations of cadmium and copper and planted with rice,Oryza sativa.
Organic matter controlled copper partitioning and bioavailability, whereas the synthetic ferrihydrite bound negligible amounts
of either metal, even in the absence of organic matter. As organic matter concentrations increased, operationally-defined
leachable copper decreased, organic-associated copper increased and the survival of rice plants improved in an approximately
linear fashion. At a nominal starting copper concentration of 5.8 μg g dry wt−1, plant survival after four weeks averaged 0–8% in sediments without organic matter, 25% in a sediment containing 0.18% organic
matter and 58% in a sediment containing 0.36% organic matter. These results suggest that organic-associated forms of copper
are unavailable to plants, and that the operational definition of ‘leachable’ copper (extracted with dilute ammonium acetate)
adequately represents the species of copper that is (are) available to plants. Our study using a well-characterized artificial
sediment supports the copper fractionation patterns and correlations between copper partitioning and bioavailability reported
from the heterogeneous, poorly characterized sediments of natural lake and river sediments. 相似文献
11.
Functional Exoenzymes as Indicators of Metabolically Active Bacteria in 124,000-Year-Old Sapropel Layers of the Eastern Mediterranean Sea 总被引:1,自引:1,他引:0
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Hydrolytic exoenzymes as indicators of metabolically active bacteria were investigated in four consecutive sapropel layers collected from bathyal sediments of the eastern Mediterranean Sea. For comparison, the organic carbon-poor layers between the sapropels, sediment from the anoxic Urania basin, and sediments of intertidal mud flats of the German Wadden Sea were also analyzed. The sapropel layers contained up to 1.5 · 108 bacterial cells cm−3, whereas cell numbers in the intermediate layers were lower by a factor of 10. In sapropels, the determination of exoenzyme activity with fluorescently labeled substrate analogues was impaired by the strong adsorption of up to 97% of the enzymatically liberated fluorophores (4-methylumbelliferone [MUF] and 7-amino-4-methylcoumarin [MCA]) to the sediment particles. Because all established methods for the extraction of adsorbed fluorophores proved to be inadequate for sapropel sediments, we introduce a correction method which is based on the measurement of equilibrium adsorption isotherms for both compounds. Using this new approach, high activities of aminopeptidase and alkaline phosphatase were detected even in a 124,000-year-old sapropel layer, whereas the activity of β-glucosidase was low in all layers. So far, it had been assumed that the organic matter which constitutes the sapropels is highly refractory. The high potential activities of bacterial exoenzymes indicate that bacteria in Mediterranean sapropels are metabolically active and utilize part of the subfossil kerogen. Since a high adsorption capacity was determined not only for the low-molecular-weight compounds MUF and MCA but also for DNA, the extraordinarily strong adsorption of structurally different substrates to the sapropel matrix appears to be the major reason for the long-term preservation of biodegradable carbon in this environment. 相似文献
12.
Dalila Serpa Manuela Falcão Pedro Duarte Luís Cancela da Fonseca Carlos Vale 《Biogeochemistry》2007,82(3):291-304
During an annual cycle, overlying water and sediment cores were collected simultaneously at three sites (Tavira, Culatra and
Ramalhete) of Ria Formosa’s intertidal muddy and subtidal sandy sediments to determine ammonium, nitrates plus nitrites and
phosphate. Organic carbon, nitrogen and phosphorus were also determined in superficial sediments. Ammonium and phosphate dissolved
in porewater were positively correlated with temperature (P < 0.01) in muddy and sandy sediments, while the nitrogen-oxidized forms had a negative correlation (P < 0.02) in muddy sediments probably because mineralization and nitrification/denitrification processes vary seasonally. Porewater
ammonium profiles evidenced a peak in the top-most muddy sediment (380 μM) suggesting higher mineralization rate when oxygen
is more available, while maximum phosphate concentration (113 μM) occurred in the sub-oxic layer probably due to phosphorus
desorption under reduced conditions. In organically poor subtidal sandy sediments, nutrient porewater concentrations were
always lower than in intertidal muddy sediments, ranging annually from 20 μM to 100 μM for ammonium and from 0.05 μM to 16 μM
for phosphate. Nutrient diffusive fluxes predicted by a mathematical model were higher during summer, in both muddy (104 nmol cm−2 d−1––NH4+; 8 nmol cm−2 d−1––HPO4−2) and sandy sediments (26 nmol cm−2 d−1––NH4+; 1 nmol cm−2 d−1––HPO4−2), while during lower temperature periods these fluxes were 3–4 times lower. Based on simulated nutrient effluxes, the estimated
annual amount of ammonium and phosphate exported from intertidal areas was three times higher than that released from subtidal
areas (22 ton year−1––NH4+; 2 ton year−1––HPO4−2), emphasizing the importance of tidal flats to maintain the high productivity of the lagoon. Global warming scenarios simulated
with the model, revealed that an increase in lagoon water temperature only produces significant variations (P < 0.05) for NH4+ in porewater and consequent diffusive fluxes, what will probably affect the system productivity due to a N/P ratio unbalance. 相似文献
13.
Land reclamation as a cause of fine-grained sediment depletion in backbarrier tidal flats (Southern North Sea) 总被引:4,自引:0,他引:4
Grain size distribution patterns along the East Frisian coast (German Wadden Sea) were evafuated with the aim of identifying
potential effects of man-made structures (e.g. dikes) on the textural composition and sediment budget of the area. It was found that the distribution of various grain size
fractions and settling velocities revealed a well-defined cross-shore energy gradient. Adjacent to the mainland dike the sediment
is dominated by the 3.0–3.5 phi sand fraction (>70% by weight). In comparison to the sedimentary sequences normally observed
in unobstructed backbarrier depositional environments, the sediments along the land-ward margin are in this case conspicuously
depleted in grain sizes <3.5 phi, the corresponding size fractions contributing <20% by weight. This suggests that the dike
interrupts the normal energy gradient, thereby inhibiting the deposition of sediments with settling velocities <0.5 cm s−1. This interpretation is confirmed when comparing individual cross-shore transects. The shorter the transect between the barrier
island shore and the dike, the greater the fine sediment depletion. Since many faunal assemblages are grain-size specific,
it is further suggested that the backbarrier ecosystem must have undergone significant modifications as a result of the substantial
reduction in mud flats since the onset of dike construction some 1000 years BP. It is predicted that in the wake of the persisting
and possibly accelerating sealevel rise this process of fine sediment depletion will continue and also affect progressively
coarser sediments. 相似文献
14.
Hydrolytic exoenzymes as indicators of metabolically active bacteria were investigated in four consecutive sapropel layers collected from bathyal sediments of the eastern Mediterranean Sea. For comparison, the organic carbon-poor layers between the sapropels, sediment from the anoxic Urania basin, and sediments of intertidal mud flats of the German Wadden Sea were also analyzed. The sapropel layers contained up to 1.5. 10(8) bacterial cells cm(-3), whereas cell numbers in the intermediate layers were lower by a factor of 10. In sapropels, the determination of exoenzyme activity with fluorescently labeled substrate analogues was impaired by the strong adsorption of up to 97% of the enzymatically liberated fluorophores (4-methylumbelliferone [MUF] and 7-amino-4-methylcoumarin [MCA]) to the sediment particles. Because all established methods for the extraction of adsorbed fluorophores proved to be inadequate for sapropel sediments, we introduce a correction method which is based on the measurement of equilibrium adsorption isotherms for both compounds. Using this new approach, high activities of aminopeptidase and alkaline phosphatase were detected even in a 124,000-year-old sapropel layer, whereas the activity of beta-glucosidase was low in all layers. So far, it had been assumed that the organic matter which constitutes the sapropels is highly refractory. The high potential activities of bacterial exoenzymes indicate that bacteria in Mediterranean sapropels are metabolically active and utilize part of the subfossil kerogen. Since a high adsorption capacity was determined not only for the low-molecular-weight compounds MUF and MCA but also for DNA, the extraordinarily strong adsorption of structurally different substrates to the sapropel matrix appears to be the major reason for the long-term preservation of biodegradable carbon in this environment. 相似文献
15.
The Salton Sea is the largest lake, on a surface area basis, in California (939 km2). Although saline (>44 g/l) and shallow (mean depth approximately 9.7 m), it provides valuable habitat for a number of endangered
species. The distribution of sediments and their properties within the Salton Sea are thought to have significant influence
on benthic ecology and water quality. Sediment properties and their distribution were quantified and compared with predicted
distributions using several sediment distribution models. Sediment samples (n = 90) were collected using a regular staggered-start sampling grid and analyzed for water content, organic carbon (C), calcium
carbonate, total nitrogen (N), total phosphorus (P), organic phosphorus, and other properties. Water content, total N, and
total and organic P concentrations were all highly correlated with organic C content. The organic C concentration showed a
non-linear increase with depth, with low organic C contents (typically 1–2%) present in sediments found in depths up to 9 m,
followed by a strong increase in organic C at greater depths (to about 12% at 15 m depth). The models of Hakanson, Rowan et al.,
Blais and Kalff, and Carper and Bachmann yielded very different predicted critical depths for accumulation (10.5–22.8 m) and
areas of accumulation (0–49.5%). Hakanson’s dynamic ratio model more reasonably reproduced the observed zone of elevated organic
C concentrations in the Salton Sea than either exposure- or slope-based equations. Wave theory calculations suggest that strong
winds occurring less than 1% of the time are sufficient to minimize accumulation of organic matter in sediments that lie at
depths less than 9 m in this system.
Guest editor: S. H. Hurlbert
The Salton Sea Centennial Symposium. Proceedings of a Symposium Celebrating a Century of Symbiosis Among Agriculture, Wildlife
and People, 1905–2005, held in San Diego, California, USA, March 2005 相似文献
16.
Pore water and solid phase distributions of C, N, P and Si in sediments of the Arctic Ocean (Svalbard area) have been investigated.
Concentrations of organic carbon (Corg) in the solid phase of the sediment varied from 1.3 to 2.8% (mean 1.9%), with highest concentrations found at shallow stations
south/southwest of Svalbard. Relatively low concentrations were obtained at the deeper stations north/northeast of Svalbard.
Atomic carbon to nitrogen ratios in the surface sediment ranged from below 8 to above 10. For some stations, high C/N ratios
together with high concentrations of Corg suggest that sedimentary organic matter is mainly of terrigenous origin and not from overall biological activity in the water
column. Organic matter reactivity (defined as the total sediment oxygen consumption rate normalized to the organic carbon
content of the surface sediment) correlated with water depth at all investigated stations. However, the stations could be
divided into two separate groups with different reactivity characteristics, representing the two most dominant hydrographic
regimes: the region west of Svalbard mainly influenced by the West Spitsbergen Current, and the area east of Svalbard where
Arctic polar water set the environmental conditions. Decreasing sediment reactivity with water depth was confirmed by the
partitioning between organic and inorganic carbon of the surface sediment. The ratio between organic and inorganic carbon
at the sediment-water interface decreased exponentially with water depth: from indefinite values at shallow stations in the
central Barents Sea, to approximately 1 at deep stations north of Svalbard. At stations east of Svalbard there was an inverse
linear correlation between the organic matter reactivity (as defined above) and concentration of dissolved organic carbon
(DOC) in the pore water. The more reactive the sediment, the less DOC existed in the pore water and the more total carbonate
(Ct or ΣCO2) was present. This observation suggests that DOC produced in reactive sediments is easily metabolizable to CO2. Sediment accumulation rates of opaline silica ranged from 0.35 to 5.7 μmol SiO2 m−2d−1 (mean 1.3 μmol SiO2 m−2d−1), i.e. almost 300 times lower than rates previously reported for the Ross Sea, Antarctica. Concentrations of ammonium and
nitrate in the pore water at the sediment-water interface were related to organic matter input and water depth. In shallow
regions with highly reactive organic matter, a pool of ammonium was present in the pore water, while nitrate conoentrations
were low. In areas where less reactive organic matter was deposited at the sediment surface, the deeper zone of nitrification
caused a build-up of nitrate in the pore water while ammonium was almost depleted. Nitrate penetrated from 1.8 to ≥ 5.8 cm
into the investigated sediments. Significantly higher concentrations of “total” dissolved nitrogen (defined as the sum of
NO3, NO2, NH4 and urea) in sediment pore water were found west compared to east of Svalbard. The differences in organic matter reactivity,
as well as in pore water distribution patterns of “total” dissolved nitrogen between the two areas, probably reflect hydrographic
factors (such as ice coverage and production/import of particulate organic material) related to the dominant water mass (Atlantic
or Arctic Polar) in each of the two areas.
The data presented were collected during the European “Polarstern” Study (Arctic EPOS) sponsored by the European Science Foundation 相似文献
17.
Luitgard Schwendenmann Rainer Riecke Rubén J. Lara 《Wetlands Ecology and Management》2006,14(5):463-475
Although water in mangrove sediments influences nutrient cycling in both, mangrove forest and estuary, little information
exists on seasonal and vertical distribution of dissolved organic and inorganic compounds in the sediment column. We studied
the influence of sediment texture and chemistry, permeability (K), tides, and rainfall on dissolved organic carbon (DOC) and nitrogen (DON), dissolved inorganic phosphate (DIP) and salinity
in creek and sediment waters of a mangrove in Pará, Brazil. Water samples were taken from boreholes and piezometers in the
mangrove forest and from an adjacent tidal creek at neap and spring tides, during the dry and rainy season. Forest sediment
was analysed for carbon (C), nitrogen (N), salinity and permeability. Clay, C and N decreased with depth. Sediment permeability
(K) was lowest (<0.1 m day−1) in the upper, clay-rich and crab-burrow-free mud layer. In the deeper, fine sand strata, K ranged from 0.7 to 1.8 m day−1. Tidal range in the creek was 3.5 and 5.5 m for neap and spring tides, respectively. Salinity, DOC, DON and DIP in creek
water were inversely related to tidal height. Piezometer data revealed significant water level changes in deeper, sandy sediment
layer, which followed, time-lagged, the tidal fluctuations. In contrast, tide did not affect the water level in the upper
sediment due to low permeability. Compared with creek water, sediment water was enriched in DOC, DON and DIP because of organic
matter input and mineralization. In deeper layers, solute concentration was most likely affected by sorption processes (DOC
and DIP) and reduction reactions (DIP). During the rainy season, DOC and DON in creek and sediment water were higher than
in the dry season. DIP appeared invariant to seasonal changes. In the rainy season, salt flushing from surface sediments resulted
in higher salinities at intermediate sediment depths, while in the deeper layers salinity was lower due to exchange with water
from the tidal creek. 相似文献
18.
Tracking rates of ecotone migration due to salt-water encroachment using fossil mollusks in coastal South Florida 总被引:1,自引:1,他引:0
Evelyn E. Gaiser Angelikie Zafiris Pablo L. Ruiz Franco A. C. Tobias Michael S. Ross 《Hydrobiologia》2006,569(1):237-257
We determined the rate of migration of coastal vegetation zones in response to salt-water encroachment through paleoecological
analysis of mollusks in 36 sediment cores taken along transects perpendicular to the coast in a 5.5 km2 band of coastal wetlands in southeast Florida. Five vegetation zones, separated by distinct ecotones, included freshwater
swamp forest, freshwater marsh, and dwarf, transitional and fringing mangrove forest. Vegetation composition, soil depth and
organic matter content, porewater salinity and the contemporary mollusk community were determined at 226 sites to establish
the salinity preferences of the mollusk fauna. Calibration models allowed accurate inference of salinity and vegetation type
from fossil mollusk assemblages in chronologically calibrated sediments. Most sediments were shallow (20–130 cm) permitting
coarse-scale temporal inferences for three zones: an upper peat layer (zone 1) representing the last 30–70 years, a mixed
peat-marl layer (zone 2) representing the previous ca. 150–250 years and a basal section (zone 3) of ranging from 310 to 2990
YBP. Modern peat accretion rates averaged 3.1 mm yr−1 while subsurface marl accreted more slowly at 0.8 mm yr−1. Salinity and vegetation type for zone 1 show a steep gradient with freshwater communities being confined west of a north–south
drainage canal constructed in 1960. Inferences for zone 2 (pre-drainage) suggest that freshwater marshes and associated forest
units covered 90% of the area, with mangrove forests only present along the peripheral coastline. During the entire pre-drainage
history, salinity in the entire area was maintained below a mean of 2 ppt and only small pockets of mangroves were present;
currently, salinity averages 13.2 ppt and mangroves occupy 95% of the wetland. Over 3 km2 of freshwater wetland vegetation type have been lost from this basin due to salt-water encroachment, estimated from the mollusk-inferred
migration rate of freshwater vegetation of 3.1 m yr−1 for the last 70 years (compared to 0.14 m yr−1 for the pre-drainage period). This rapid rate of encroachment is driven by sea-level rise and freshwater diversion. Plans
for rehydrating these basins with freshwater will require high-magnitude re-diversion to counteract locally high rates of
sea-level rise. 相似文献
19.
Tidal variation of biological parameters was studied at three anchor stations in selected inlet channels of the northern German
Wadden Sea in May and July 1994. Concentrations of bacteria, chlorophyll a and suspended matter as well as primary and bacterial
production were assessed over a period of 25 h in the surface and in the bottom water. Diurnal variation in primary production
was found both under in situ light conditions and under constant illumination. Tidal turbulence caused the introduction of
detritus, bacteria and pigments from the sediment into the water column. The impact of sediment resuspension was most evident
in the bottom water, leading to tidally oscillating bacterial production rates which were high during high stream velocity
and low during the slack times. Estimations of the areal daily phytoplankton production and corresponding bacterial carbon
demands were unbalanced. Primary production accounted for only 25–45% of the total bacterial carbon requirement. This discrepancy
is due to the shallow euphotic depth in the Wadden Sea, allowing net primary production only in the upper 2–3 m of the water
column, while the relatively high levels of bacterial activity do not show a vertical decline. Assuming that the specific
biological activities in the water columns over the tidal flats are similar to those found in the inlet channels, it was found
that production processes dominate in shallow areas whereas decomposition processes dominate in the deep channels. Moreover,
the predominance of heterotrophic processes in the inlet channels means that additional organic carbon sources must contribute
to the heterotrophic metabolism in the deep parts of the Wadden Sea, and that the horizontal flux of material is important
in this turbid mesotidal ecosystem.
Received: 18 April 1998 / Accepted: 12 November 1998 相似文献
20.
In the geological research of the Holocene coastal deposits of The Netherlands, diatoms are used to reconstruct the sedimentary
facies, palaeo-tide levels and salinity gradients during the deposition of the sediments. In this paper, the results of diatom
research from 4 borings, taken from the early and middle Holocene deposits of central North Holland are presented. The oldest
marine influenced sediments in the area are the deposits of the ‘Velsen layer’, a clay layer rich in organic matter and deposited
about 8000–700014C years before present (BP) at a depth of 20–12 m below present mean sea-level. This clay layer was formed in a shallow, permanently
submerged environment with a limited tidal influence (lagoonal or pond-like conditions). The salinity changed from brackish/freshwater
to marine/brackish. The younger sandy and clayey sediments, formed about 7000–4500 BP at a depth of 16–3 m below present mean
sea-level, are classified as ‘tidal channel’ and ‘interchannel’ deposits. It is argued, on the base of both diatom and non-diatom
criteria, that the lower and middle parts of the interchannel deposits in the central area of the palaeo-tidal basin of North
Holland were formed in a subtidal environment. The upper part of the interchannel deposits and the deposits at the fringe
of the North Holland tidal basin were formed in the intertidal zone or, at the fringe of the basin, even in the supratidal
zone. The salinity in the North Holland tidal basin during the sedimentation of the tidal channel and interchannel deposits
was marine/brackish to marine. This study indicates that diatoms, besides their palaeoecological applications, have chronostratigraphical
significance (on a regional scale). The diatomsCymatosira belgica andActinoptychus splendens appear to be a useful (eco)stratigraphical marker in the Holocene coastal deposits of The Netherlands and Belgium. 相似文献