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首页> 外文学位 >Nitrogen cycling on coral reefs: A stable isotopic investigation of nutrient dynamics within the Florida Keys coral reef tract.
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Nitrogen cycling on coral reefs: A stable isotopic investigation of nutrient dynamics within the Florida Keys coral reef tract.

机译：氮在珊瑚礁上的循环：对佛罗里达礁岛珊瑚礁内养分动态的稳定同位素研究。

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This dissertation serves as a comprehensive, natural-abundance analysis of the present-day spatial and temporal dynamics and trophic linkages of nitrogen from within the Florida Keys National Marine Sanctuary (FKNMS). This work was accomplished by documenting the delta15N of particulate organic matter (POM), several genera of aquatic vegetation and herbivorous fish, as well as dissolved water column nitrogen. Seasonal and spatial variations in delta15N were assessed, trophic level variations among reef constituents were quantified, and relative contributions of both natural and anthropogenic nitrogen into the reef tract were determined.; The measured mean delta15N of POM (+3.64‰), aquatic vegetation (Dictyota = +2.39‰; Thalassia = +1.91‰; Rhizophora mangle = +1.46‰; Halimeda = +1.62‰; sponges = +4.13‰; turf algae = +2.67‰), herbivorous fish (+4.92‰ to +8.47‰), as well as the delta 15N and delta18O of nitrate (+4.40‰ and +20.36‰, respectively) suggest that the primary nutrient sources directly impacting the reef are from natural sources, principally N2 fixation, and not anthropogenic wastes. Clear trophic linkages, without evidence of disturbances from anthropogenic wastes, are apparent in this study; herbivorous fishes show distinct +3 to +4‰ enrichments over their food source. The presence of anthropogenic wastes was detected in the delta15N and delta 18O of nitrate from Key Largo canal waters (+10.09‰, however, sewage derived nutrients did not exist in any measurable or detectable amount outside the canals. Additionally, an assessment of the total yearly nitrogen contributions to the FKNMS was conducted, demonstrating that N2 fixation was the largest contributor of nitrogen to the ecosystem, delivering approximately 43% of all nitrogen. Anthropogenic wastes, however, contributed only ∼8% to the total nitrogen budget, far less than biotic (non-human) wastes (13%), upwelling (10%), and gyre waters from the Gulf of Mexico (9%).; For the first time, a long term, spatially diverse investigation has presented a more complete depiction of delta15N composition of various reef components found in the FKNMS, critical and imperative for accurately assessing nutrient pressures on coral reefs. As such, the data presented in this study do not support the theory that continuous anthropogenic nutrient loading from nearshore populations is the sole cause of reef decline in the FKNMS.
机译：本文是对佛罗里达州国家海洋保护区（FKNMS）内当今氮的时空动态和营养联系的综合，自然丰度分析。通过记录δ15N的颗粒有机物（POM），几种水生植物和草食性鱼类以及溶解的水柱氮来完成这项工作。评估了delta15N的季节和空间变化，定量了礁石成分之间的营养水平变化，并确定了自然氮和人为氮对礁石的相对贡献。测得的POM的平均delta15N（+ 3.64‰），水生植被（Dictyota = + 2.39‰; Thalassia = + 1.91‰; Rhizophora mangle = + 1.46‰; Halimeda = + 1.62‰;海绵= + 4.13‰;草皮藻= + 2.67‰），草食鱼（+ 4.92‰至+ 8.47‰）以及硝酸盐的15N和delta18O（分别为+ 4.40‰和+ 20.36‰）表明直接影响礁石的主要营养来源是天然的来源，主要是固氮，而不是人为浪费。在这项研究中，明显的营养联系很明显，没有人为废物造成干扰的证据。食草鱼类在其食物来源上显示出明显的+3至+ 4‰丰富度。在拉哥岛主要运河水域的硝酸盐的δ15N和δ18O中检测到人为废物的存在（+ 10.09‰，但是，运河外没有任何可测量或可检测到的污水来源养分，此外，还对总量进行了评估每年对FKNMS进行的氮贡献量都表明，固氮是生态系统中氮的最大贡献者，约占总氮的43％，而人为浪费仅占总氮预算的8％左右，远低于来自墨西哥湾的生物（非人类）废物（13％），上升流（10％）和回旋水（9％）；首次，长期的，空间上不同的调查提出了更完整的描述FKNMS中发现的各种礁石成分的δ15N组成，对于准确评估珊瑚礁上的营养压力至关重要且至关重要，因此，本研究提供的数据不支持FKNMS中来自近岸种群的不连续的人为营养负荷是珊瑚礁下降的唯一原因。

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