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81.
Identifying nutrient sources, primarily nitrogen (N) and phosphorus (P), sufficient to support high biomass blooms of the red tide dinoflagellate, Karenia brevis, has remained problematic. The West Florida Shelf is oligotrophic, yet populations >106 cells L−1 frequently occur and blooms can persist for months. Here we examine the magnitude and variety of sources for N and P that are available to support blooms. Annual average in situ or background concentrations of inorganic N in the region where blooms occur range 0.02–0.2 μM while inorganic P ranges 0.025–0.24 μM. Such concentrations would be sufficient to support the growth of populations up to ∼3×104 cells L−1 with at least a 1 d turnover rate. Organic N concentrations average 1–2 orders of magnitude greater than inorganic N, 8–14 μM while organic P concentrations average 0.2–0.5 μM. Concentrations of organic N are sufficient to support blooms >105 cells L−1 but the extent to which this complex mixture of N species is utilizable is unknown. Other sources of nutrients included in our analysis are aerial deposition, estuarine flux, benthic flux, zooplankton excretion, N2-fixation, and subsequent release of organic and inorganic N by Trichodesmium spp., and release of N and P from dead and decaying fish killed by the blooms. Inputs based on atmospheric deposition, benthic flux, and N2-fixation, were minor contributors to the flux required to support growth of populations >2.6×104 cells L−1. N and P from decaying fish could theoretically maintain populations at moderate concentrations but insufficient data on the flux and subsequent mixing rates does not allow us to calculate average values. Zooplankton excretion rates, based on measured zooplankton population estimates and excretion rates could also supply all of the N and P required to support populations of 105 and 106 cells L−1, respectively, but excretion is considered as “regenerated” nutrient input and can only maintain biomass rather than contribute to “new” biomass. The combined estuarine flux from Tampa Bay, Charlotte Harbor, and the Caloosahatchee River can supply a varying, but at times significant level of N and P to meet growth and photosynthesis requirements for populations of approximately 105 cells L−1 or below. Estimates of remineralization of dead fish could supply a significant proportion of bloom maintenance requirements but the rate of supply must still be determined. Overall, a combination of sources is required to maintain populations >106 cells L−1.  相似文献   
82.
Nutrient distributions observed at some depths along the continental shelf from 27°05′S (Brazil) to 39°31′S (Argentina) in winter, 2003 and summer, 2004 related to salinity and dissolved oxygen (mL L−1) and saturation (%) data showed remarkable influences of fresh water discharge over the coastal region and in front of the La Plata estuary. In the southern portion of the study area different processes were verified. Upwelling processes caused by ocean dynamics typical of shelf break areas, eddies related to surface dynamics and regeneration processes confirmed by the increase of nutrients and the decrease of dissolved and saturation oxygen data were verified. High silicate concentrations in the surface waters were identified related to low salinities (minimum of 21.22 in winter and 21.96 in summer), confirming the importance of freshwater inputs in this region, especially in winter. Silicate concentration range showed values between 0.00 and 83.52 μM during winter and from 0.00 to 41.16 μM during summer. Phosphate concentrations worked as a secondary trace of terrestrial input and their values varied from 0.00 to 3.30 μM in winter and from 0.03 to 2.26 μM in summer; however, in shallow waters, phosphate indicated more clearly the fresh water influence. The most important information given by nitrate concentrations was the presence of water from SACW upwelling that represents a new source of nutrients for marine primary production. Nitrate maximum values reached 41.96 μM in winter and 33.10 μM in summer. At a depth ∼800 m, high nitrate, phosphate and silicate concentrations were related to Malvinas Current Waters, Subantarctic Shallow Waters and Antarctic Atlantic Intermediate Waters (AAIW). Dissolved oxygen varied from 3.41 to 7.06 mL L−1 in winter and from 2.65 to 6.85 mL L−1 in summer. The percentage of dissolved oxygen saturation in the waters showed values between 48% and 113% in winter and from 46% to135% in summer. The most important primary production was verified in the summer, and situations of undersaturation were mainly observed below 50 m depth and at some points near the coast. The anti-correlation between nutrients and dissolved oxygen which showed evident undersaturation also revealed important potential sites of remineralization processes. The nutrient behaviours showed some aspects of the processes that occur over the Southwestern South Atlantic continental shelf and in their land–sea interfaces between Mar del Plata and Itajaí.  相似文献   
83.
北黄海浮游植物营养盐限制的初步研究   总被引:29,自引:4,他引:25  
王勇  焦念志 《海洋与湖沼》1999,30(5):512-518
于1997年11月,在北黄海采用现场实验的方法,研究营养盐对浮游植的的上行效应。将浮物植的分为3个粒级:网采浮游植物(netphytophlankton,简称net,20-200μm)微型浮植物(nanophytoplankton,简称nano-,2-20μm)和超微型浮游植物(picophytoplankton,简称pico-,〈2μm)实验期间pico-味绿素a的生物量占整个浮的群总叶绿素a生  相似文献   
84.
南黄海营养盐的平面分布及横向输运   总被引:15,自引:3,他引:12  
黄海对我国是颇为重要的陆架海区,也是世界上最典型的半封闭性陆架浅海之一。它和所有陆架海区一样,是人类活动、经济开发最为集中的地带,也是陆地、海洋、大气各种过程相互作用较为激烈的地带。  相似文献   
85.
河口是连接陆地-海洋的一个关键区域,具有重要的生态系统服务价值。然而,随着经济快速发展,河口接纳了越来越多来自于流域等地的营养物质,导致河口生态系统的富营养化潜力大大增加。本研究利用沿海富营养化潜力指数(index of coastal eutrophication potential,ICEP)量化河流输入对九龙江河口所产生的影响,特别是对富营养化指标的年度和季节性变化动态进行了分析。结果表明,九龙江河口区溶解性无机氮(DIN)和溶解性无机磷(DIP)浓度年均值均呈波动性增长,自1980s以来九龙江河口营养负荷发生了较显著变化,1980s—2006年期间DIN通量平均值为3.967×103 t/a,而2006—2020年期间增加到2.924×104 t/a,增长了637.14%,其中最高值达8.279×104 t/a。两个时期DIP通量平均值分别为1.131×102和2.282×102 t/a,增长了101.87%,其中最高值达6.128×102 t/a...  相似文献   
86.
三江平原湿地植物群落P、K的积累、动态及其生物循环   总被引:9,自引:0,他引:9  
在三江平原湿地植物生长季节里,选择该区分布最广、面积最大且最具有代表性的毛果苔草(Carexlasioncarpa)-狭叶甜茅(Glyceria spiculosa)群落和小叶章(Deyeuxia angustifo-lia)群落为研究对象,逐月测定两类湿地群落生物量,并对植物样品分别用钼锑抗比色法和原子吸收法测定其P、K含量。在此基础上,探讨了两类湿地群落的P、K积累量及其生物循环特征。结果表明,三江平原不同的植物群落以及同一群落的不同器官,其P、K元素积累量不同,而且都有明显的季节变化。根是群落中P、K元素的最大贮存器官,其P、K积累量占总量的80%左右。湿地群落中K的吸收量、归还量、存留量、现存量和表土贮量都大于P的对应值,同时K的利用系数和循环系数均大于P,毛果苔草-狭叶甜茅群落K的吸收系数大于P,而小叶章群落K的吸收系数小于P。  相似文献   
87.
88.
波纹巴非蛤肉的食品化学特性及其在鱼糜制品中的应用   总被引:5,自引:0,他引:5  
对波纹巴非蛤肉进行的食品化学特性研究表明 :其贝肉的粗蛋白含量为 70 .6 % (干基 ) ;蛋白质营养价高 ,氨基酸价为 85(第 1限制氨基酸为 Trp) ,并富含 Glu(10 0 g样品中 2 .2 g;以下单位同 )、Asp(1.4 7g)等呈味氨基酸及提取物成分 ,Ca、Fe等无机质含量丰富。波纹巴非蛤肉以 30 %的比例添加到蛇鲻鱼糜中 ,可制得具有贝类风味 ,色泽、弹性良好的“花甲螺丸”  相似文献   
89.
Sustainable food systems face trade-offs between demands of low environmental pressures per unit area and requirements of increasing production. Organic farming has lower yields than conventional agriculture and requires the introduction of nitrogen (N) fixing legumes in crop rotations. Here we perform an integrated assessment of the feasibility of future food systems in terms of land and N availability and the potential for reducing greenhouse gas (GHG) emissions. Results show that switching to 100% organic farming without additional measures results in N deficiency. Dietary change towards a reduced share of animal products can aggravate N limitations, which can be overcome through the implementation of a combination of agroecological, circular economy and decarbonization strategies. These measures help to recycle and transfer N from grassland. A vegan diet from fully decarbonized conventional production performs similarly as the optimized organic scenario. Sustainable food systems hence require measures beyond the agricultural sector.  相似文献   
90.
During a semi-lunar tidal cycle from full moon till new moon, tide is characterized by the periodic change in spring and neap tide. Under the in situ conditions of light and temperature, the influence of a semi-lunar spring and neap tidal cycle on nutrient cycling in intertidal flat of the Yangtze estuary was simulated in the laboratory in July 2002. Lab experiments showed that NH4+ and PO43– were always released into overlying waters, while NO3 was directed into sediments in the permanently waterlogged systems, suggesting that the long-term waterlogged sediment acts as a significant source for NH4+ and PO43–, and a sink for NO3 in water columns. In contrast, reflooding of intertidal sediments after long-term desiccation promoted the considerable effluxes of NH4+, NO3 and PO43– into overlying waters, reflecting that the long-term exposed sediment is an important source for nutrients in overlying waters. In addition, the semi-lunar tidal cycle led to the intricate depth distribution patterns of nutrients in intertidal sediments. During long-term exposure, NH4+ in sediments was quickly transformed into NO2 and NO3, while organic P pool might be converted to slightly adsorbed and iron-bound P. Therefore, it is considered that the semi-lunar tidal circulation has the significant influence on the biogeochemical cycle of nutrients in intertidal systems.  相似文献   
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