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1.
Laboratory studies on the coprecipitation of phosphate with calcium carbonate in the Salton Sea, California 总被引:4,自引:0,他引:4
The Salton Sea is a hypereutrophic, saline lake in the desert of southern California. Like many lakes, the primary productivity
of the Sea is limited by phosphorus. However, unlike most lakes, the release of P from the sediments is not controlled by
the reductive dissolution of Fe(III)-oxide minerals. Most of the iron in the sediments of the Salton Sea is present as Fe(II)-sulfides
and silicates. Rather, the sediments are dominated by calcite which is actively precipitating due to alkalinity production
via sulfate reduction reactions. We hypothesized that calcite could be an important sink for phosphorus released from the
decomposing organic matter. In this work we evaluated the potential for phosphate to coprecipitate with calcite formed in
simulated Salton Sea sediment pore water. At calcite precipitation levels and P concentrations typical for the Salton Sea
pore water, coprecipitation of P removed 82–100% of the dissolved phosphorus. The amount of P incorporated into the calcite
was independent of temperature. The results of this work indicate that the internal loading of P within the Salton Sea is
being controlled by calcite precipitation. Management of external P loading should have an immediate impact on reducing algae
blooms in the Salton Sea.
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
2.
The Salton Sea is a hypersaline lake located in southeastern California. Concerns over the ecological impacts of sediment
quality and potential human exposure to dust emissions from exposed lakebed sediments resulting from anticipated shrinking
of shoreline led to a study of pesticide distribution and transport within the Salton Sea Basin, California, in 2001–2002.
Three sampling stations—upriver, river mouth, and offshore—were established along each of the three major rivers that discharge
into the Salton Sea. Large-volume water samples were collected for analysis of pesticides in water and suspended sediments
at the nine sampling stations. Samples of the bottom sediment were also collected at each site for pesticide analysis. Sampling
occurred in October 2001, March–April 2002, and October 2002, coinciding with the regional fall and spring peaks in pesticide
use in the heavily agricultural watershed. Fourteen current-use pesticides were detected in water and the majority of dissolved
concentrations ranged from the limits of detection to 151 ng/l. Diazinon, EPTC and malathion were detected at much higher
concentrations (940–3,830 ng/l) at the New and Alamo River upriver and near-shore stations. Concentrations of carbaryl, dacthal,
diazinon, and EPTC were higher in the two fall sampling periods, whereas concentrations of atrazine, carbofuran, and trifluralin
were higher during the spring, which matched seasonal use patterns of these pesticides. Current-use pesticides were also detected
on suspended and bed sediments in concentrations ranging from detection limits to 106 ng/g. Chlorpyrifos, dacthal, EPTC, trifluralin,
and DDE were the most frequently detected pesticides on sediments from all three rivers. The number of detections and concentrations
of suspended sediment-associated pesticides were often similar for the river upriver and near-shore sites, consistent with
downstream transport of pesticides via suspended sediment. While detectable suspended sediment pesticide concentrations were
more sporadic than detected aqueous concentrations, seasonal trends were similar to those for dissolved concentrations. Generally,
the pesticides detected on suspended sediments were the same as those on the bed sediments, and concentrations were similar,
especially at the Alamo River upriver site. With a few exceptions, pesticides were not detected in suspended or bed sediments
from the off-shore sites. The partitioning of pesticides between water and sediment was not predictable from solely the physical–chemical
properties of individual pesticide compounds, but appear to be a complicated function of the quantity of pesticide applied
in the watershed, residence time of sediments in the water, and compound solubility and hydrophobicity. Sediment concentrations
of most pesticides were found to be 100–1,000 times lower than the low-effects levels determined in human health risk assessment
studies. However, maximum concentrations of chlorpyrifos on suspended sediments were approximately half the low-effects level,
suggesting the need for further sediment characterization of lake sediments proximate to riverine inputs.
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
3.
Salton Sea, California, like many other lakes, has become eutrophic because of excessive nutrient loading, primarily phosphorus
(P). A Total Maximum Daily Load (TMDL) is being prepared for P to reduce the input of P to the Sea. In order to better understand
how P-load reductions should affect the average annual water quality of this terminal saline lake, three different eutrophication
programs (BATHTUB, WiLMS, and the Seepage Lake Model) were applied. After verifying that specific empirical models within
these programs were applicable to this saline lake, each model was calibrated using water-quality and nutrient-loading data
for 1999 and then used to simulate the effects of specific P-load reductions. Model simulations indicate that a 50% decrease
in external P loading would decrease near-surface total phosphorus concentrations (TP) by 25–50%. Application of other empirical
models demonstrated that this decrease in loading should decrease near-surface chlorophyll a concentrations (Chl a) by 17–63% and increase Secchi depths (SD) by 38–97%. The wide range in estimated responses in Chl a and SD were primarily caused by uncertainty in how non-algal turbidity would respond to P-load reductions. If only the models
most applicable to the Salton Sea are considered, a 70–90% P-load reduction is required for the Sea to be classified as moderately
eutrophic (trophic state index of 55). These models simulate steady-state conditions in the Sea; therefore, it is difficult
to ascertain how long it would take for the simulated changes to occur after load reductions.
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
4.
Kurt A. Schwabe Peter W. Schuhmann Kenneth A. Baerenklau Nermin Nergis 《Hydrobiologia》2008,604(1):181-195
This article, both theoretical and methodological in nature, argues the potential merits of using a net benefits’ framework
as a tool to aid policy makers in their efforts to compare Salton Sea restoration alternatives and inform the public as to
the potential magnitude and distribution of trade-offs associated with each alternative. A net benefits’ approach can provide
a more accurate comparison and evaluation of the potential net returns from public spending on Salton Sea restoration than
what would be provided under the suggested criteria of current legislative mandates. Furthermore, a net benefits’ framework
provides a more lucid and systematic accounting framework by which to enumerate the full array of benefits and costs of each
alternative for policy analysis. Finally, net benefits’ analysis serves to add transparency to the decision-making process
so that the public gains an understanding of how its scarce resources, including both financial and natural capital, are being
appropriated. Additionally, we illustrate and emphasize the importance of estimating the non-market values associated with
many of the ecosystem services provided by the Salton Sea and describe the major techniques that do so.
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
5.
The Salton Sea (Sea) is a eutrophic to hypereutrophic lake characterized by high nutrient concentrations, low water clarity,
and high biological productivity. Based on dissolved phosphorus (P) and nitrogen (N) concentrations and N:P ratios, P is typically
the limiting nutrient in the Sea and, therefore, should be the primary nutrient of concern when considering management efforts.
Flows in the major tributaries to the Sea have been measured since 1965, whereas total P (TP) concentrations were only measured
intermittently by various agencies since 1968. These data were used to estimate annual P loading from 1965 to 2002. Annual
loads have increased steadily from ∼940,000 kg around 1968 to ∼1,450,000 kg in 2002 (∼55% increase), primarily a result of
increased TP concentrations and loads in the New River. Although the eutrophic condition of the Salton Sea is of great concern,
only limited nutrient data are available for the Sea. It is difficult to determine whether the eutrophic state of the Sea
has degraded or possibly even improved slightly in response to the change in P loading because of variability in the data
and changes in the sampling and analytical methodologies.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
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
6.
The Salton Sea is one of the few saline, inland lakes in the world with a population of barnacles, Balanus amphitrite. It is also one of California’s most impaired water bodies due to excessive nutrient loading which leads to phytoplankton
blooms and low dissolved oxygen. Currently, B. amphitrite growth is limited due to lack of hard substrate in and around the Sea. We have hypothesized that artificial substrate could
support the growth of B. amphitrite and their filter-feeding would lead to improved water quality. Periodic harvesting of the barnacles would result in the permanent
removal of nitrogen and phosphorus from the Sea. A 44-day in-situ experiment was carried out in the Salton Sea to assess the
rate of barnacle growth and phosphorus and nitrogen sequestration on burlap sheets suspended vertically from a floating line.
Burlap panels were collected weekly and the barnacles analyzed for Ca, total-P, inorganic-P, total-N, total-C, CaCO3, and organic matter content. After 44 days of growth, the barnacle mats weighed 7.4 kg m−2 on a dry weight basis, with 80% of the mass as shell material. The nutrient sequestration was 9.4 g P m−2 and 100 g N m−2. Approximately half of the P was inorganic and appears to be coprecipitated with the calcium carbonate shell material. Results
indicate that harvesting barnacles grown on artificial substrate in the Salton Sea would not be an effective method for removing
N or P from the lake because of the relative proportions of shell material and organic material.
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
7.
Geochemistry of iron in the Salton Sea,California 总被引:1,自引:0,他引:1
The Salton Sea is a large, saline, closed-basin lake in southern California. The Sea receives agricultural runoff and, to
a lesser extent, municipal wastewater that is high in nutrients, salt, and suspended solids. High sulfate concentrations (4×
higher than that of the ocean), coupled with warm temperatures and low-redox potentials present during much of the year, result
in extensive sulfate reduction and hydrogen sulfide production. Hydrogen sulfide formation may have a dramatic effect on the
iron (Fe) geochemistry in the Sea. We hypothesized that the Fe(II)-sulfide minerals should dominate the iron mineralogy of
the sediments, and plans to increase hypolimnetic aeration would increase the amount of Fe(III)-oxides, which are strong adsorbers
of phosphate. Sequential chemical extractions were used to differentiate iron mineralogy in the lake sediments and suspended
solids from the tributary rivers. Iron in the river-borne suspended solids was mainly associated with structural iron within
silicate clays (70%) and ferric oxides (30%). The iron in the bottom sediments of the lake was associated with silicate minerals
(71% of the total iron in the sediments), framboidal pyrite (10%), greigite (11%), and amorphous FeS (5%). The ferric oxide
fraction was <4% of the total iron in these anaerobic sediments. The morphological characteristics of the framboidal pyrite
as determined using SEM suggest that it formed within the water column and experiences some changes in local redox conditions,
probably associated with alternating summer anoxia and the well-mixed and generally well-aerated conditions found during the
winter. The prevalence of Fe(II)-sulfide minerals in the sediments and the lack of Fe(III)-oxide minerals suggest that the
classic model of P-retention by Fe(III)-oxides would not be operating in this lake, at least during anoxic summer conditions.
Aeration of the hypolimnion could affect the internal loading of P by changing the relative amounts of Fe(II)-sulfides and
Fe(III)-oxides at the sediment/water interface.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
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
8.
Ammonium perchlorate, a component of rocket fuel, entered Lake Mead through drainage and shallow groundwater in the Las Vegas
Valley, Nevada, and is now found in the lower Colorado River from Lake Mead to the international boundary with Mexico. Perchlorate
is a threat to human health through reduction of thyroid hormone production. Perchlorate has been found in water throughout
the lower Colorado system and in crops in the California’s Imperial Valley, as well as in several other states, but it has
not previously been included in investigations of the Salton Sea. Because perchlorate behaves conservatively in the Colorado
River, it was postulated that it could be accumulating at high levels along with other salts in the Salton Sea. Results show
that perchlorate is not accumulating in the Sea, although it is present in tributaries to the Sea at levels similar to those
found in the Colorado River. Bacterial reduction of perchlorate is the most likely explanation for the observed results.
The U.S. Government’s right to retain a non-exclusive, royalty-free license in and to any copyright is acknowledged.
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
9.
In order to examine the transport of contaminants associated with river-derived suspended particles in the Salton Sea, California,
large volume water samples were collected in transects established along the three major rivers emptying into the Salton Sea
in fall 2001. Rivers in this area carry significant aqueous and particulate contaminant loads derived from irrigation water
associated with the extensive agricultural activity, as well as wastewater from small and large municipalities. A variety
of inorganic constituents, including trace metals, nutrients, and organic carbon were analyzed on suspended material isolated
from water samples collected at upriver, near-shore, and off-shore sites established on the Alamo, New, and Whitewater rivers.
Concentration patterns showed expected trends, with river-borne metals becoming diluted by organic-rich algal particles of
lacustrine origin in off-shore stations. More soluble metals, such as cadmium, copper, and zinc showed a more even distribution
between sites in the rivers and off-shore in the lake basin. General distributional trends of trace elements between particulate
and aqueous forms were discerned by combining metal concentration data for particulates from this study with historical aqueous
metals data. Highly insoluble trace metals, such as iron and aluminum, occurred almost entirely in the particulate phase,
while major cations and approximately 95% of selenium were transported in the soluble phase. Evidence for greater reducing
conditions in the New compared to the Alamo River was provided by the greater proportion of reduced (soluble) manganese in
the New River. Evidence of bioconcentration of selenium and arsenic within the lake by algae was provided by calculating “enrichment”
concentration ratios from metal concentrations on the algal-derived particulate samples and the off-shore sites.
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
Roy A. Schroeder—Retired. 相似文献
10.
Eu Gene Chung S. Geoffrey Schladow Joaquim Perez-Losada Dale M. Robertson 《Hydrobiologia》2008,604(1):57-75
A linked hydrodynamic and water quality model was developed and applied to the Salton Sea. The hydrodynamic component is based
on the one-dimensional numerical model, DLM. The water quality model is based on a new conceptual model for nutrient cycling
in the Sea, and simulates temperature, total suspended sediment concentration, nutrient concentrations, including and DO concentration and chlorophyll a concentration as functions of depth and time. Existing water temperature data from 1997 were used to verify that the model
could accurately represent the onset and breakup of thermal stratification. 1999 is the only year with a near-complete dataset
for water quality variables for the Salton Sea. The linked hydrodynamic and water quality model was run for 1999, and by adjustment
of rate coefficients and other water quality parameters, a good match with the data was obtained. In this article, the model
is fully described and the model results for reductions in external phosphorus load on chlorophyll a distribution are presented.
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
11.
Brandon K. Swan James M. Watts Kristen M. Reifel Stuart H. Hurlbert 《Hydrobiologia》2007,576(1):111-125
The Salton Sea currently suffers from several well-documented water quality problems associated with high nutrient loading.
However, the importance of phosphorus regeneration from sediments has not been established. Sediment phosphorus regeneration
rates may be affected by benthic macroinvertebrate activity (e.g. bioturbation and excretion). The polychaete Neanthes
succinea (Frey and Leuckart) is the dominant benthic macroinvertebrate in the Salton Sea. It is widely distributed during periods
of mixing (winter and spring), and inhabits only shallow water areas following development of anoxia in summer. The contribution
of N. succinea to sediment phosphorus regeneration was investigated using laboratory incubations of cores under lake temperatures and dissolved
oxygen concentrations typical of the Salton Sea. Regeneration rates of soluble reactive phosphorus (SRP) were lowest (−0.23–1.03
mg P m−2 day−1) under saturated oxygen conditions, and highest (1.23–4.67 mg P m−2 day−1) under reduced oxygen levels. N. succinea most likely stimulated phosphorus regeneration under reduced oxygen levels via increased burrow ventilation rates. Phosphorus
excretion rates by N. succinea were 60–70% more rapid under reduced oxygen levels than under saturated or hypoxic conditions. SRP accounted for 71–80% of
the dissolved phosphorus excreted under all conditions. Whole-lake SRP regeneration rates predicted from N. succinea biomass densities are highest in early spring, when the lake is mixing frequently and mid-lake phytoplankton populations
are maximal. Thus, any additional phosphorus regenerated from the sediments at that time has potential for contributing to
the overall production of the lake.
Guest Editor: John M. Melack
Saline Water and their Biota 相似文献
12.
Nitrogen and phosphor compounds in bottom sediments: mechanisms of accumulation,transformation and release 总被引:7,自引:1,他引:7
M. V. Martinova 《Hydrobiologia》1993,252(1):1-22
This paper is an overview of Russian literature dealing with the accumulation, the transformations and the release of phosphate
and nitrogen compounds in a great number of Russian lakes and reservoirs. A considerable data bank has been analysed. Special
attention is given to the relations of N- and P-accumulation with the input and transformation of organic carbon, as well
as to the release mechanisms, often in relation to eutrophication of the lakes and reservoirs.
It is shown that the major input of organic matter into the sediments comes from autochthonous material, and is usually >
70 %. The relative importance of phytoplankton and macrophytes as sources of organic matter is discussed; it appears that
trophic state, depth and other factors may have a large influence on this ratio. In shallow eutrophic lakes macrophytes may
be the source of organic matter, which source can amount to 1.5–2.5 times that of phytoplankton.
It is also shown that the C/N ratio is not a good indicator of the source of the organic matter, because their C/N ratios
often are not very different. The decomposition rate of organic matter was analysed; it depends on trophic state and other
factors.
Sediment N accumulation is mostly (> 90%) in organic form, and depends on nitrogen and organic matter inputs coming from phytoplankton
or macrophytes. A correlation coefficient of 0.9–0.95 was found in 176 lakes. In 113 lakes the N accumulation was 0.11 x C
accumulation, with C/N ratios between 7.4 and 12.9. Ammonification was rather constant in different groups of lakes; values
were often about 20–25 mg m−2 d−1. The presence of the different forms of nitrogen in interstitial water and in adsorbed forms is discussed. The N in interstitial
water is usually in the form of NH3.
Sediment P-accumulation is usually in inorganic form and is related to primary production. Three different groups of sediments
could be distinguished with C/P ratios of 31–100, of 101–350 and > 350. In hard water lakes P sedimentation was found to be
0.3–0.5 times that in soft water lakes with comparable primary production. The relative occurrence of apatite, non-apatite
and residual P in sediments was calculated. In the interstitial water the P concentration appeared to be controlled by the
input and decomposition of organic matter. The concentration of phosphate dissolved in the interstitial water of the top 2
cm layer is often 10–100 times lower than that of the dissolved N. The concentrations of interstitial phosphate are from a
few μgl−1 up to 15 mgl−1, but the higher concentrations occur only rarely. Different types of vertical profiles of P compounds in the sediments were
shown to be related with the presence of an oxidised zone, the presence of clay etc. Autochthonous apatite and non-apatite
phosphates are more mobile than the allochthonous ones and are in equilibrium with interstitial phosphate. Accumulation of
autochthonous apatite in sediments is controlled by decomposition of organic matter and accumulation of carbonates. 相似文献
13.
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
14.
Meiofauna distribution and mesoscale variability in two sites of the Ross Sea (Antarctica) with contrasting food supply 总被引:5,自引:0,他引:5
Meiofauna abundance, biomass and community structure were investigated in two comparable deep sites of the Ross Sea (Antarctica)
characterized by different trophic and sediment characteristics. Site B (567 m depth, dominated by muddy sediments) and site
C (439 m depth, characterized by the presence of calcareous debris and coarse sand) were located at increasing distance from
the polynyas and were subject to different inputs of organic material to the seabed. Total meiofauna abundance ranged from
192.0 to 1191.2 ind. 10 cm−2, and total biomass varied between 9.5 and 50.3 μgC 10 cm−2. Meiofauna densities from the Ross Sea are, on average, 2–7 times lower than those reported from other similar deep polar
regions and displayed significant differences between the sites. Nematodes dominated the samples at both sites, but their
relative significance changed between the sites (80% at site B and 56% at site C), followed by copepods (1.6% and 35% at sites
B and C, respectively). Meiofauna composition at site B appeared similar to that reported for deep-sea antarctic or temperate
sediments, whereas the composition at site C was similar to that of coastal areas. On a macroscale, the different inputs of
utilizable organic material at the two sites were reflected in meiofaunal distribution patterns, indicating that meiofaunal
communities from the Ross Sea are dependent on particulate organic matter fluxes from the photic layer and are coupled to
pelagic phenomena. Very low microscale variations (i.e. between replicates) in meiofauna density contrasted with large mesoscale
variability, which was related to the concentration of the main food indicators (phytopigments, proteins, carbohydrates and
lipids).
Accepted: 18 February 1999 相似文献
15.
The Salton Sea, a hypersaline lake located in Southern California, is a major habitat for migratory waterfowl, including endangered species, recently threatened by selenium toxicity. Selenium is both an essential micronutrient and a contaminant and its speciation and cycling are driven by microbial activity. In the absence of oxygen, microorganisms can couple the oxidation of organic matter with the reduction of soluble selenate and selenite to elemental selenium. In order to better understand and quantify selenium cycling and selenium transfer between water and underlying sediments in the Salton Sea, we measured the maximum potential selenate reduction rates (R max) and selenate adsorption isotherms in sediments collected from seven littoral locations in July 2011. We also measured salinity, organic carbon, nitrogen, and elemental selenium content and the abundance of selenate-reducing prokaryotes at each site. Our results showed a high potential for selenate reduction and limited selenate adsorption in all studied sites. Maximum potential selenate reduction rates were affected by sediment Corg content. We showed that selenate reduction potential of Salton Sea sediments far outweighs current dissolved inputs to the lake. Selenate reduction is thus a likely driver for selenium removal from the lake’s water and selenate retention in littoral sediments of the Salton Sea. 相似文献
16.
The Salton Sea is a highly eutrophic, hypersaline terminal lake that receives inflows primarily from agricultural drainages
in the Imperial and Coachella valleys. Impending reductions in water inflow at Salton Sea may concentrate existing contaminants
which have been a concern for many years, and result in higher exposure to birds. Thus, waterbird eggs were collected and
analyzed in 2004 and compared with residue concentrations from earlier years; these data provide a base for future comparisons.
Eggs from four waterbird species (black-crowned night-heron [Nycticorax nycticorax], great egret [Ardea alba], black-necked stilt [Himantopus mexicanus], and American avocet [Recurvirostra Americana]) were collected. Eggs were analyzed for organochlorine pesticides, polychlorinated biphenyls (PCBs), metals, and trace elements,
with current results compared to those reported for eggs collected from the same species and others during 1985–1993. The
two contaminants of primary concern were p,p′-DDE (DDE) and selenium. DDE concentrations in night-heron and great egret eggs collected from the northwest corner of Salton
Sea (Whitewater River delta) decreased 91 and 95%, respectively, by 2004, with a concomitant increase in eggshell thickness
for both species. Decreases in bird egg DDE levels paralleled those in tissues of tilapia (Oreochromis mossambicus × O. urolepis), an important prey species for herons and egrets. Despite most nests of night-herons and great egrets failing in 2004 due
to predation, predicted reproductive effects based on DDE concentrations in eggs were low or negligible for these species.
The 2004 DDE findings were in dramatic contrast to those in the past decade, and included an 81% decrease in black-necked
stilt eggs, although concentrations were lower historically than those reported in night-herons and egrets. Selenium concentrations
in black-necked stilt eggs from the southeast corner of Salton Sea (Davis Road) were similar in 1993 and 2004, with 4.5–7.6%
of the clutches estimated to be selenium impaired during both time periods. Because of present selenium concentrations and
future reduced water inflow, the stilt population is of special concern. Between 1992 and 1993 and 2004 selenium in night-heron
and great egret eggs from the Whitewater River delta at the north end of the Sea decreased by 81 and 55%, respectively. None
of the night-heron or egret eggs collected in 2004 contained selenium concentrations above the lowest reported effect concentration
(6.0 μg/g dw). Reasons for selenium decreases in night-heron and egret eggs are unknown. Other contaminants evaluated in 2004
were all below known effect concentrations. However, in spite of generally low contaminant levels in 2004, the nesting populations
of night-herons and great egrets at Salton Sea were greatly reduced from earlier years and snowy egrets (Egretta thula) were not found nesting. Other factors that include predation, reduced water level, diminished roost and nest sites, increased
salinity, eutrophication, and reduced fish populations can certainly influence avian populations. Future monitoring, to validate
predicted responses by birds, other organisms, and contaminant loadings associated with reduced water inflows, together with
adaptive management should be the operational framework at the Salton Sea.
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
17.
Tom Moens Sandra Vanhove Ilse De Mesel Bea Kelemen Thierry Janssens Ann Dewicke Ann Vanreusel 《Polar Biology》2007,31(1):1-13
δ13C of nematode communities in 27 sites was analyzed, spanning a large depth range (from 130 to 2,021 m) in five Antarctic regions,
and compared to isotopic signatures of sediment organic matter. Sediment organic matter δ13C ranged from −24.4 to −21.9‰ without significant differences between regions, substrate types or depths. Nematode δ13C showed a larger range, from −34.6 to −19.3‰, and was more depleted than sediment organic matter typically by 1‰ and by up
to 3‰ in silty substrata. These, and the isotopically heavy meiofauna at some stations, suggest substantial selectivity of
some meiofauna for specific components of the sedimenting plankton. However, 13C-depletion in lipids and a potential contribution of chemoautotrophic carbon in the diet of the abundant genus Sabatieria may confound this interpretation. Carbon sources for Antarctic nematodes were also explored by means of an experiment in
which the fate of a fresh pulse of labile carbon to the benthos was followed. This organic carbon was remineralized at a rate
(11–20 mg C m−2 day−1) comparable to mineralization rates in continental slope sediments. There was no lag between sedimentation and mineralization;
uptake by nematodes, however, did show such a lag. Nematodes contributed negligibly to benthic carbon mineralization. 相似文献
18.
Insights into Young of the Year White Shark, Carcharodon carcharias, Behavior in the Southern California Bight 总被引:2,自引:0,他引:2
A young of the year female white shark, Carcharodon carcharias, was tagged with a pop-up satellite archival tag off Southern California in early June of 2000. The tag was recovered after
28 days, and records of temperature, depth and light intensity were extracted. Depth and temperature records indicate a number
of interesting behaviors, including a strong diurnal pattern. At night the shark remained in the top 50 m, often making shallow
repetitive vertical excursions. Most dives below the mixed layer were observed during the day, 91% of which occurred from
05:00 to 21:00 h, with depths extending to 240 m. Many of the dives exhibited secondary vertical movements that were consistent
with the shark swimming at the bottom (at depths from 9 to 165 m) where it was most likely foraging. The white shark experienced
dramatic and rapid changes in temperature, and demonstrated a considerable tolerance for cold waters. Temperatures ranged
from 9°C to 22°C, and although 89% of the total time was spent in waters 16–22°C, on some days the small shark spent as much
as 32% of the time in 12°C waters. The deep dives into cold waters separate the white sharks from mako sharks, which share
the California Bight nursery ground but appear to remain primarily in the mixed layer and thermocline. Movement information
(derived from light-based geolocation, bottom depths and sea surface temperatures) indicated that the white shark spent the
28 days in the Southern California Bight, possibly moving as far south as San Diego, California. While the abundance and diversity
of prey, warm water and separation from adults make this region an ideal nursery ground, the potential for interaction with
the local fisheries should be examined. 相似文献
19.
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
20.
B. Busalacchi P. Rinelli F. De Domenico A. Profeta F. Perdichizzi T. Bottari 《Hydrobiologia》2010,654(1):111-124
Monitoring and management of Mediterranean trawling requires a multispecies and ecosystem-based approach. Over the last 20
years studies on diversity and distribution of fish communities have been carried out by ecologists and applied to different
ecosystems. Until now, very little information has been available on the Southern Tyrrhenian Sea. The aim of this work is:
to analyse the structure of fish demersal assemblages, on a temporal (10 years) and spatial scale using a multivariate approach;
to analyse, across space and time, the pattern of biodiversity by means of univariate indices; to identify areas supporting
high values of diversity and evenness by a Geographical Information System (GIS) method. The analysis of 249 hauls from ten
trawl surveys carried out between depths of 30 and 750 m in the South Tyrrhenian Sea yielded a total of 164 fish species.
Multidimensional scaling ordination showed four groups distributed according to the depth gradient: a coastal group (0–100 m
depth), a group in the lower part of the continental shelf (101–200 m), an epibathyal group (201–500 m) and the last one derived
from hauls made in the middleslope (501–800 m). There were no differences, between years, protected and unprotected areas
and geographical sectors. The whole study area was characterised by diversity values which were quite heterogeneous. The persistence
index was generally low. Results could be useful from an ecological point of view and for the management of fishery activities. 相似文献