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首页> 外文期刊>Ocean & coastal management >Food web of a subtropical tidal flat, Atlantic Southwestern: Temporal and spatial variability of the primary organic sources
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Food web of a subtropical tidal flat, Atlantic Southwestern: Temporal and spatial variability of the primary organic sources

机译：大西洋西南部亚热带潮滩的食物网：主要有机源的时空变化

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摘要

Trophodynamic parameters have been used as input data for trophic models and are used as indicators to support ecosystem management decisions. To understand the ecosystems' trophic structure and functioning, it is important to identify the major primary carbon sources within a food web. This study aimed to investigate the spatial and temporal variability in isotopic composition of the basal sources of the food web of the Araçá Bay (23°49′S; 45°24′W) ecosystem. This site is a sheltered tidal flat and presents a sharp seasonal change in water temperature and salinity. Samples of 15 basal sources were analysed for δ13C (n = 187) and δ15N (n = 180) values and also for the C:N ratio, in January–March (austral summer) and June–July (austral winter) 2013, in the continental, intertidal (mangrove patches and soft and rocky bottoms) and sublittoral regions. The isotope values and C:N ratios were, in general, in the range of those available in previously published studies. C3and C4plants, green macroalgae and surface sediment organic matter (SSOM) did not present significant changes in the δ13C and δ15N values with time. For suspended particulate matter (SPM), microphytobenthos (MPB) and turf-forming algae, δ13C values were higher in the summer than in the winter; also in the summer, red macroalgae showed higher δ15N values. Spatial variability was investigated for SPM, SSOM and MPB. δ13C values were significantly higher for SSOM and MPB in the intertidal region than in the sublittoral but for SPM there was no difference among regions. Values of δ15N were higher for MPB in the intertidal region than in the sublittoral, and were higher for SPM in the sublittoral region than in the intertidal and continental regions. The δ13C associated to C:N values of SSOM indicated a coupling of the marine sublittoral region and the land organic matter of an adjacent island and the SPM δ15N variability pointed out a continental land-sea connection. Some mechanisms could explain the isotopic temporal and spatial shifts and sources of organic C in the study area: the seasonality of hydrodynamics and of phytoplankton size structures and biomass; the steady low concentration of nitrate and the episodic ammonia inputs; terrestrial runoff. Our results can contribute to the construction and understanding of a trophic model of the Araçá Bay ecosystem, and also for its management, considering the seasonal hydrodynamics, the coupling of marine sublittoral region in the São Sebastião channel and terrestrial organic matter from São Sebastião Island, as well as the continental land-sea connection. We suggest a monitoring program based on SPM, bottom detritus andUlva fasciata, important primary organic sources for the Araçá Bay food web.
机译：营养动力学参数已用作营养模型的输入数据，并用作支持生态系统管理决策的指标。要了解生态系统的营养结构和功能，重要的是确定食物网中的主要主要碳源。这项研究旨在调查阿拉卡湾（23°49′S； 45°24′W）生态系统食物网基础资源同位素组成的时空变化。该地点是一个有遮盖的潮汐带，并且在水温和盐度方面表现出明显的季节性变化。在2013年1月至3月（夏季）和6月至7月（冬季），分析了15个基础源的δ13C（n（= 187）和δ15N（n = 180）值以及C：N比。大陆，潮间带（红树林斑块和柔软多岩石的底部）和沿海沿岸地区。同位素值和C：N比值​​通常在以前发表的研究中可用的范围内。 C3和C4植物，绿色大型藻类和表层沉积物有机物（SSOM）的δ13C和δ15N值不随时间变化。对于悬浮颗粒物（SPM），微植物底栖动物（MPB）和草皮形成藻类，夏季的δ13C值高于冬季的δ13C值。同样在夏季，红色大型藻类显示出更高的δ15N值。研究了SPM，SSOM和MPB的空间变异性。潮间带SSOM和MPB的δ13C值显着高于潮间带以下，但对于SPM，各区域之间没有差异。潮间带MPB的δ15N值高于潮间带，潮间带SPM的δ15N值高于潮间带和大陆区。与SSOM的C：N值相关的δ13C表示海洋沿海沿岸区域与相邻岛屿的陆地有机物之间的耦合，而SPMδ15N的变化性则表明了陆海陆相联系。一些机制可以解释研究区内有机碳的同位素时空变化和来源：水动力的季节性以及浮游植物大小结构和生物量的季节性；硝酸盐浓度稳定且间歇性氨输入较低；地面径流。考虑到季节性水动力，SãoSebastião河道的海洋沿岸区域与SãoSebastião岛的陆地有机物的耦合，我们的结果可有助于建立和理解Araçá湾生态系统的营养模型，以及对其进行管理。以及大陆海陆连接。我们建议基于SPM，底部碎屑和Ulva fasciata（阿拉斯加湾食物网的重要主要有机资源）的监测程序。

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