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151.
Predicting the distribution of Inherent Optical Properties (IOPs) in the water column requires predicting the physical, chemical, biological, and optical interactions in a common framework that facilitates feedback responses. This work focuses on the development of ecological and optical interaction equations embedded in a 2D hindcast model of the shallow water optical properties on the West Florida Shelf (WFS) during late summer/fall of 1998. This 2D simulation of the WFS includes one case with a Loop Current intrusion above the 40-m isobath and one with the Loop Current intrusion in addition to a periodic terrestrial nutrient supply below the 10-m isobath. The ecological and optical interaction equations are an expansion of a previously developed model for open ocean conditions (Bissett, W.P., Carder, K.L., Walsh, J.J., Dieterle, D.A., 1999a. Carbon cycling in the upper waters of the Sargasso Sea: II. Numerical simulation of apparent and inherent optical properties. Deep-Sea Research, Part I: Oceanographic Research Papers, 46 (2), 271–317; Bissett, W.P., Walsh, J.J., Dieterle, D.A., Carder, K.L., 1999b. Carbon cycling in the upperwaters of the Sargasso Sea: I. Numerical simulation of differential carbon and nitrogen fluxes. Deep-Sea Research, Part I: Oceanographic Research Papers, 46 (2), 205–269). The expansion includes an increase in the number of elemental pools to include silica, phosphorus, and iron, an increase in the number of phytoplankton functional groups, and a redevelopment of the Dissolved Organic Matter (DOM) and Colored Dissolved Organic Matter (CDOM) interaction equations. It was determined from this simulation that while the Loop Current alone was able to predict the water column conditions present during the summer, the Loop Current alone was not enough to simulate the magnitude of optical constituents present in the fall of 1998 when compared to satellite imagery. Simulating terrestrial inorganic and organic nutrients and CDOM pulses coinciding with significant meteorological events and high freshwater pulses released from the major rivers feeding the WFS were required to accurately predict the distribution and scale of the inherent optical properties at the surface during the fall months. Modeling the in situ light field for phytoplankton growth and community competition requires addressing the CDOM optical constituent explicitly. The majority of the annually modeled CDOM on WFS was created via in situ production; however, it was also rapidly removed via advection and photochemical destruction. A pulse of terrestrial nutrient and organic color was required to simulate the dramatic changes in surface color seen in satellite imagery on the WFS. The dynamics of the biogeochemical portion of the simulation demonstrate the importance of nonstoichiometric supplies of terrestrial nutrients on the WFS to the prediction of nutrient and CDOM fluxes.  相似文献   
152.
This study compares intracellular Cd content (Cd:C) of cultured marine phytoplankton grown under various Fe levels, with estimated particulate Cd:P ratios derived from regression slopes of Cd versus PO43− relationships from a global dataset. A 66-fold difference in Cd:C ratios was observed among the seven species grown under identical Fe concentrations, with oceanic diatoms having the highest Cd quotas and prymesiophytes the lowest. Interestingly, all species significantly increased their Cd:C ratios under Fe-limitation (on average 2-fold). The global data set also showed that the mean estimated Cd:P ratio of surface water particulates in HNLC (high nutrient low chlorophyll) regions were approximately 2-fold higher than non-HNLC regions. A sequence of events are proposed to explain high Cd:P ratios in HNLC waters. First, the seasonal relief from Fe-limitation in HNLC regions leads to blooms of large chain forming diatoms with high intrinsic Cd:P ratios. These large blooms may, in theory, deplete surface water CO2 and Zn concentrations, which ultimately, would result in increased Cd uptake. Eventually these blooms will run out of Fe, which has been shown to further increase intercellular Cd via growth biodilution and increased Cd uptake through non-specific Fe(II) transporters. Ultimately, Fe-limited diatoms with enhanced Cd quotas will sink out of surface waters leading to pronounced regional differences in Cd:P ratios between HNLC and non-HNLC waters in the global ocean.  相似文献   
153.
As a result of the stagnation of commercial fishery landings, aquaculture activities are expected to increase over the next decades to match the growing demand for marine protein. Overall, it is expected that the aquaculture sector could reduce some of the fishing pressure applied to wild stocks. However, this development is likely to be limited by the availability of key aquaculture inputs, specifically fishmeal and fish oil products (FMFOP). Aquaculture provided 60 % (fish meal) and 80 % (fish oil) of the world total consumption of these products in 2007. FMFOP are generally derived from small pelagic fish species, but can also be derived from other sources. Identifying the origin of FMFOP is crucial to understanding the effects of this new pressure on marine social-ecological systems. Two factors are of particular importance in the reduction sector transforming wild fish into fishmeal or fish oil: the two “conversion ratios” (i.e. the ratio between the quantity of wild fish harvested and the resulting quantity of FMFOP, and the ratio between the quantity of FMFOP and aquaculture production), and the type of raw material used by the reduction sector. Based on trade and production databases from FAO and the International Fishmeal and Fish oil Organisation (IFFO), this paper proposes an approach to identify the origin of FMFOP. It shows that whereas different countries use different pelagic resources to produce FMFOP, other countries use non-pelagic sources, and some countries use pelagic resources for human consumption.  相似文献   
154.
介形类壳体中Sr/Ca及Mg/Ca比值的ICP-AES测定   总被引:1,自引:0,他引:1  
朱育新  吉磊  王苏民 《湖泊科学》1996,8(2):179-183
沉积物中介形类壳体的Sr/Ca和Mg/Ca比值可用于湖泊古盐度和古温度的重建。本文从双通道顺序扫描式ICP-AES的特点出发,对μg级介形类样品中的低含量元素Sr和Mg选择最灵敏谱线和最佳通道,对各项条件进行最优化。Sr和Mg的检测限分别为1.1μg/L和1.4μg/L。本文以此法准确测定了介形类样品中Sr/Ca比值和Mg/Ca比值,回收率实验结果令人满意。  相似文献   
155.
Seasonal meteorological events of high wind energy are important in the export of organic carbon from Biscayne Bay, Florida, by altering circulation and tidal flushing patterns coincident with increased resuspension. The accumulation of detrital organic carbon in the bay during productive summer months with light south-east breezes is reversed by the onset of the winter season and associated weekly cold fronts with sustained 15 knot northerly winds. The reversal of Biscayne Bay circulation patterns and increased discharge at Caesar's Creek result in an outwelling of dissolved organic carbon and particulate organic carbon. Southward advection at the seaward extremes of exchange channels prevents reintroduction of exported organic carbon by tidal currents.  相似文献   
156.
The last 42,000 years of hydrological history of Lake Frome, a large playa located in the arid part of northern South Australia, which is hypersaline and most often dry today, is reconstructed using a combination of ostracod assemblages, other microfossil remains, and the trace elemental composition of the selected halobiont ostracod species of Diacypris and Reticypris.The Mg/Ca and Sr/Ca of ostracod valves from 2 cores relate to significant hydrological changes that affected the lake over time. The reconstruction of the Sr/Ca of the lake’s waters, based on the Sr/Ca of ostracod shells, shows that when the lake fills the waters originate mostly from runoff, not from hypersaline waters located below the lake or the surrounding aquifers. The Last Glacial Maximum saw gypsum deflation from the lake.Prior to 25K yBP, Frome had a stable hydrological regime, permanent water and low salinities, with occasional freshwater conditions between 42 and 33K yBP. From 25 to 20.3K yBP, salinities fluctuated and ephemeral conditions operated. After that, until ∼14.8K yBP, a brine pool was located below the lake and was therefore under a different hydrological regime. Between 13 and 11.2K yBP, wet conditions occurred, but such conditions were not seen again during the Holocene.  相似文献   
157.
Abundant ostracode valves (Cyprinotus cingalensis) and caryopses of Urochloa paspaloides, a terrestrial grass, were well preserved in the lacustrine sediments of the Cattle Pond on Dongdao Island, South China Sea. Oxygen and carbon isotopes, and elements (Ca, Mg) were analyzed on ostracode valves and plant caryopses in this study. The δ18Oostracode and δ13Costracode exhibited a positive and statistically significant correlation, and showed a decreasing trend toward the top of sediment sequence with some fluctuations, indicating a gradual increase in effective moisture. The Mg/Ca ratios in the ostracode shells, generally used as a proxy for salinity changes in lake water, showed a trend toward lower values in the upper samples, reflecting a gradual decrease of salinity in the lake. The δ13Corg values in the plant caryopses of the upper 14 cm of sediment have lower values than those in the bottom sediments, suggesting less water and salinity stress. These results indicate increasing effective moisture and rainfall intensity over the past ∼1,100 years on Dongdao Island.  相似文献   
158.
A 911-m-long sediment core from Lake Biwa, Japan, provides a record of organic matter delivery and accumulation in this large lake during a succession of tectonic and climatic changes dating back to the latest Pliocene. Sediments deposited since 430 ky are profundal; older sediments vary in setting between shallow-water and fluviodeltaic conditions, with occasional deep-water intervals. C/N ratios identify algal production as the dominant source of organic matter throughout the core, although the proportion of land-derived contributions episodically increases in the fluviodeltaic and shallow-water sediments. Rates of organic matter delivery and burial in lake sediments change in response to glacial-interglacial climate changes over the past 430 ky. Sediments deposited during interglacial intervals have organic carbon mass accumulation rates up to 9 times greater than those from glacial intervals, reflecting interglacial climates that were wetter than glacial climates. Algal production of organic matter increased during interglacial times because of greater wash-in of soil nutrients, and organic matter preservation was enhanced because of faster sedimentation rates.  相似文献   
159.
本文简述了铜岩山矿床地质概况,分析了矿区内蚀变带和主要矿体特征,综合研究本矿区剥蚀程度地球化学判别指标。利用累乘晕比值方法,建立5组累乘元素比值公式,求得各组剥蚀系数,以显示矿区内矿体矿化序列和剥蚀程度。发现本矿区内高温成矿元素分布在矿体上方,中低温成矿元素聚集在矿体下部之矿化反序列现象。  相似文献   
160.
Sequential P extraction was combined with electron microscop and X-ray spectroscopy to characterise various P species and to study their transformation in settling seston and in recent sediment. During early diagenesis most of the particulate P formed in the water was redissolved. No net transformation into species that would resist dissolution was observed.It was shown that
•  the phosphorus (P) content and the P flux of settling particles varied seasonally over one order of magnitude
•  particles became enriched with reductant soluble P (BD-P) while settling through the hypolimnion
•  changes in BD-P were highly significantly correlated with changes in reductant soluble iron (BD-Fe)
•  bacteria oxidising Fe and Mn seemed to be mainly responsible for this increase in P concentration
•  other fractions including organic P did not change during sedimentation
•  most of the organic P and of the Fe bound P and 70% of TP was released from the sediment during early diagenesis
•  the sediment surface did not act as a trap for P migrating upwards from deeper sediment layers
•  CaCO3 sedimentation contributed little to P sedimentation but significantly to the permanent burial of P.
  相似文献   
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