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Benthic macrophytes from 19 sites within the Marano‐Grado Lagoon were sampled in July 2007 in order to update the available information on the flora and vegetation and to assess the Ecological Status (ES) within the European Water Framework Directive (WFD). Data on macrophytes were analysed using two phytobenthic indices (EEI and R‐MaQI) recently set up to evaluate the ecological status of transitional environments in the Mediterranean eco‐region. Notwithstanding the extension (c. 160 km2) that places this lagoon as the second largest Italian transitional environment, ecological studies are relatively few. The present research revealed a relatively poor flora, mainly characterized by the dominance of low‐diversity settlements of Ulvaceae. Moreover, the absence of intensive aquaculture activities and commercial big harbours, which account for the new species introductions recorded in other lagoons, limits the presence of non‐autochthonous species. The comparison with previous data ( Curiel et al. 1998 ) highlighted the reduction of macrophyte coverage and biomass, especially Ulvaceae stands, and an increase in species richness. In particular, there was evidence of a worsening of the area north of the Grado bridge. This area, which in the past was colonized by widespread angiosperm coverage, at present is almost lacking in vegetation. According to these observations, by applying both the phytobenthic indices available in the literature for the transitional environments, the Marano‐Grado Lagoon showed a ‘Good–High’ quality in the central part of the basin and near the lagoon inlets and a ‘Poor–Bad’ quality in the northern and southern areas. The evaluation of some physico‐chemical parameters, coupled with the distribution of the angiosperms, also allowed a first delineation of the main lagoon water bodies. 相似文献
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One hundred and twenty-four fishing areas were identified and georeferenced according to fishermen's traditional ecological knowledge. Nearly 80% of the designations of the fishing areas were known by fishermen only and are registered for the first time. Fishermen identify fishing areas according to depth, wooden logs used to anchor fixed nets, gradation of water transparency, and traditional use of certain areas. This study reveals the richness of knowledge held by fishermen, it illustrates their solid straight relationship with the natural environment where they live, and shows the potential uses of TEK for fisheries management. 相似文献
66.
The Manzala Lagoon in Egypt's Nile Delta has become a sediment sink of reduced area and depth, with increased contaminant
levels. Loss of much-needed fresh to brackish water reserves and decreased fish catches have serious ramifications. Herein,
maps of temporal and regional sediment distributions in Manzala incorporate petrological and statistical analyses of 200 surficial
and short core samples. These provide baseline information needed to help implement protection measures for this vital wetland.
Four periods are considered: 1920s, 1940s, ∼1965, and 1990. Important depositional changes between 1940s and ∼1965 resulted
from anthropogenic effects on this quasi-closed lagoon system, including industrial buildup, wetland conversion to agricultural
land, and irrigation waterway development. Further modification from ∼1965 to 1990 is associated with closure of the Aswan
High Dam, continued construction of waterways that discharge waste water into lagoon margins, and marine incursion into the
northern lagoon. If current practices continue, the lagoon could be reduced to about one-third of its present area by 2050
AD.
Received: 2 October 1997 · Accepted: 13 January 1998 相似文献
67.
In this paper we present sedimentological, geochemical, mineralogical and 14C Accelerator Mass Spectrometry (AMS) dating data of a 21.0‐m core obtained from Alikes Lagoon, Zakynthos Island. It is the first time that sedimentological and geochemical data are presented, up to 21‐m depth, from an Holocene coastal lagoon environment of the Ionia Sea, western Greece. The sedimentological properties and the geochemical composition of sediments were studied for the time period between 8540 years bp to present. Samples were analysed for their particle size, calcium carbonate and total organic carbon (TOC) content. Moreover, bulk sample chemical analyses for major and trace elements were carried out, as well as bulk, oriented mineralogical analyses for the clay fraction (<2 µm) were determined by powder X‐Ray diffraction. The grain size characteristics, statistical parameters and TOC, for the Holocene analysed samples, suggest a coastal environment (restricted‐shallow) with reduced salinity such as a tidal flat and/or particularly marsh in a lagoon margin. Sediment characteristics as well as trace element records may contain additional new palaeoclimate information that provide important new constraint on sediment depositional environment and Holocene climate. Stratigraphic variation of geochemical indices, such as Rb/Ti, Cs/Ti, Eu/Eu*, Th/Ti, La/Ti, Ta/Ti, Yb/Ti and Y/Ti, for the sediments with ages from 8540 to 7210 years bp , remain relatively constant indicating that the provenance of the Alikes Lagoon remained similar throughout the mid Holocene. However, geochemical indices in sediments with ages from 7110 years bp to present, indicate the transition from a warm and wet climate in the middle Holocene to a relatively cold climatic conditions in modern times. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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Stefano Covelli Andrea EmiliAlessandro Acquavita Ne?a Koron Jadran Faganeli 《Continental Shelf Research》2011,31(16):1777-1789
Previous research recognized most of the Northern Adriatic coastal lagoon environments as contaminated by mercury (Hg) from multiple anthropogenic sources. Among them, the Pialassa Baiona (P.B.) Lagoon, located near the city of Ravenna (Italy), received between 100 and 200 tons of Hg, generated by an acetaldehyde factory in the period 1957-1977. Further east, the Grado Lagoon has been mainly affected by a long-term Hg input from the Idrija mine (western Slovenia) through the Isonzo River since the 16th century. Hg cycling at the sediment-water interface (SWI) of the two lagoons was investigated and compared by means of an in situ benthic chamber, estimating diffusive Hg and Methyl-Hg fluxes in the summer season. Major chemical features in porewaters (Fe, Mn, H2S, dissolved inorganic (DIC) and organic carbon (DOC), nutrients) and in the solid phase (Corg, N and S) were also explored to understand the general biogeochemical conditions of the system in response to benthic respiration. The daily integrated flux for the methylated Hg form was extremely low in P.B. Lagoon, accounting for only 7% of the corresponding flux calculated for the Grado Lagoon. Despite a higher sedimentary Hg content in the P.B. Lagoon (14.4-79.0 μg g−1) compared to the Grado Lagoon (10.7-12.5 μg g−1), the in situ fluxes of Hg in the two experimental sites appeared similar. A selective sequential extraction procedure was applied to the solid phase, showing that the stable crystalline mineral phase cinnabar (HgS) is the predominant Hg fraction (about 50%) in the Grado Lagoon surface sediments. Conversely, Hg mobilization and sequestration in the P.B. Lagoon is related to the extremely anoxic redox conditions of the system where the intense sulfate reduction, by the release of sulfur and the formation of sulfides, limits the metal recycling at the SWI and its availability for methylation processes. Thus, the environmental conditions at the SWI in the P.B. Lagoon seem to represent a natural “barrier” for the potential risk of Hg transfer to the aquatic trophic chain. 相似文献
70.
环境饵料丰度的季节变化对筼筜湖3种大型底栖动物食性的影响——来自稳定同位素的证据 总被引：4，自引：1，他引：3
测定了不同时期筼筜湖3种大型底栖动物(沙筛贝Mytilopsis sallei、日本大螯蜚Grandidierella japonica和腺带刺沙蚕Neanthes japonica)及其潜在食源的稳定同位素组成(δ13C和δ15 N),研究环境饵料丰度的季节变化对筼筜湖3种大型底栖动物食性的影响。结果显示,筼筜湖悬浮颗粒有机物(Particulate organic matter∶POM)的δ13C和δ15 N存在明显的季节变化。3月,受到输入筼筜湖的西海域海水大量陆源有机碎屑以及湖区周围的生活污水以及餐饮业输入的影响,筼筜湖POM的δ13 C和δ15 N明显贫化;而在9月,POM中δ13 C和δ15 N明显富集的内源性浮游植物的贡献增加。沙筛贝是典型的底栖滤食者,主要以POM为食,但它比POM富集的δ13 C值(3月和9月二者之间的Δδ13 C分别为2.9‰和1.6‰)表明它还摄入其他δ13 C相对富集的食物来源:石莼来源的有机碎屑可能是3月份沙筛贝δ13C富集的原因,而9月份则是由于再悬浮的底栖微藻对沙筛贝食源的贡献引起的。食碎屑的腺带刺沙蚕和日本大螯蜚在3月以石莼及其表面的附生生物为食,而9月份底栖微藻和浮游植物来源的POM是它们食源的主要贡献者。本研究的结果显示,筼筜湖3种大型底栖动物的δ15 N都出现明显的季节变化(Δδ15 N介于2.2‰~4.3‰),这是由于它们食源稳定同位素的季节性波动及其食性的季节变化引起的,而消费者食性的季节性变化则受到不同时期环境食物可利用性的影响。 相似文献