Does Change in an Adriatic ­Hydromedusan Fauna Indicate an Early Phase of Marine Ecosystem Destruction?

Abstract. One of the most critical problems in human efforts to combat consequences of pollution is the proper identification of the initial phases of ecosystem disturbance. Investigation of hydrographic conditions and medusan species composition in the Northern Adriatic region from 1992 to 1997 showed persistence of hypoxic conditions and low numbers of meroplanktonic hydromedusae. The changes observed in the hydromedusan fauna demonstrate one aspect of the long-term consequences of oxygen deficiencies in marine ecosystems: decreased biodiversity. We suggest that the species composition of meroplanktonic hydromedusae may be a useful indicator of the early phase of such changes.     

Study of coastal water zone ecosystem health in Zhejiang Province based on remote sensing data and GIS

The coastal ecosystem health assessment is a field of increasing importance. In this paper, a preliminary assessment of ecosystem health in Zhejiang coastal water zone was made, mainly based on remote sensing data and GIS technique. Its spatial and quantitative evaluation was facilitated by the progress of remote sensing and GIS technique development. Firstly, human activities, hydrology and ecosystem problems in the study area were discussed and analyzed. Secondly, from 4 aspects of human stress, physical, chemical and biological responses to anthropogenic activities and natural stress, several indicators such as water transparency (Secchi Disk Depth, SDD), suspended substance concentration, dissolved inorganic nitrogen, active phosphate, chlorophyll, harmful algae bloom, as well as distribution of sewage, sea lanes and port were employed. Thirdly, the Analytic Hierarchical Process was used for indicator weight calculation, and the ecosystem health criteria were established according to the integrative analysis of national water quality criteria, similar coastal ecosystem health research in other places or data inherent properties. The results indicated that from 2005 to 2007 the coastal water ecosystem health value in Zhejiang Province was unhealthy and needs ecological restoration by human intervention.     

台风过程对广西红树林净生态系统碳交换的影响研究

为研究台风过程对广西红树林净生态系统碳交换的影响,利用北海红树林生态观测试验站涡度相关系统观测的红树林碳通量和气象观测数据,分析台风"韦帕"登陆前后红树林净生态系统碳交换变化特征及其与气象因子的响应关系.结果表明:(1)红树林净生态系统碳交换碳汇峰值在台风登陆前递增并达到极值,台风登陆时碳汇峰值迅速降低,而在台风登陆后...     

Plankton origin of particulate dimethylsulfoniopropionate in a Mediterranean oligotrophic coastal and shallow ecosystem

We report here dimethylsulfide (DMS) and dimethylsulfoniopropionate (DMSP) levels as a function of plankton communities and abiotic factors over a 12-month cycle in the Mediterranean oligotrophic coastal and shallow ecosystem of Niel Bay (N.W. Mediterranean Sea, France). Total particulate DMSP (DMSP_p) and DMS concentrations were highly seasonal, peaking during a spring (April) bloom at 8.9 nM and 73.9 nM, respectively. Significant positive correlations were found between total DMSP_p concentration and the abundance or biomass of the dinoflagellate Prorocentrum compressum (Spearman's rank correlation test: r = 0.704; p = 0.011). Similarly, DMS concentrations peaked during the development of blooms of P. compressum and Gymnodinium sp. There seemed to be a positive relationship between the chlorophyll a to pheopigment ratio and DMS concentrations, suggesting that DMS was released during phytoplankton growth. High DMS levels recorded in the shallow Niel Bay may also result from the activity of benthic macroalgae, and/or macrophytes such as Posidonia spp., or the resuspension of sulfur species accumulating in sediments. The fractionation of particulate DMSP into three size classes (>90 μm, 5–90 μm and 0.2–5 μm) revealed that 5–90 μm DMSP-containing particles made the greatest contribution to the total DMSP_p pool (annual mean contribution = 62%), with a maximal contribution in April (96%). This size class consisted mainly of dinoflagellates (annual mean contribution = 68%), with P. compressum and Gymnodinium sp. the predominant species, together accounting for up to 44% of the phytoplankton present. The positive correlation between DMSP concentration in the 5–90 μm size class and the abundance of P. compressum (Spearman's rank correlation test: r = 0.648; p = 0.023) suggests that this phytoplankton species would be the major DMSP producer in Niel Bay. The DMSP collected in the >90 μm fraction was principally associated with zooplankton organisms, dominated by copepods (nauplii and copepodites). DMSP_>90, not due to a specific zooplankton production, resulted from the phytoplankton cells ingested during grazing. The concomitant peaks of DMS concentration and zooplankton abundance suggest that zooplankton may play a role in releasing DMSP and/or DMS through sloppy feeding.     

Long-term effects of reduced nutrient inputs to the North Sea

The OSPAR Commission has identified a set of Ecological Quality Objectives (EcoQOs) to assess eutrophication in the North Sea. In order to assess the long-term effects of different river nutrient reduction scenarios in terms of these EcoQOs, a 3-dimensional coupled physical–chemical–biological model, NORWECOM, has been used. The model results show that there is a decreasing response gradient from near-shore to offshore, where the largest effects are identified along the Dutch coast, and that the full potential of a reduction is seen after 2–3 years. The EcoQOs on winter nutrients and chlorophyll are achieved for most areas. Oxygen concentrations displace no or very low response to the modelled nutrient reductions. The study also shows that the ecological quality is controlled to a large extent by winds and ocean circulation.     

Modelling future conditions in the degraded semi-arid estuary of Australia's largest river using ecosystem states

Over the last ten years, there has been a major decline in the condition of the Coorong, the estuary for Australia's largest river system, the River Murray. This decline is due to prolonged drought combined with past management of the Murray-Darling Basin. In order to successfully manage the estuary in the future, predictions are needed to evaluate the effect of possible management actions on the Coorong ecosystem under a variety of climatic scenarios. The alternative stable state concept can be extended to non-equilibrium systems, allowing for modelling of condition. Rather than constraining the definition of alternative states to those that are stable, we identify a suite of ecosystem states that occur naturally, but also include those that arise during the decline of the system. Eight distinct states were defined, with thresholds between them based on a combination of environmental characteristics associated with co-occurring biota. Threshold values for environmental characteristics define the transition rules between states. Mapping these states allows us to characterise the condition of the estuary in both space and time. The distribution of these states, and the diversity of states supported can be used to create an ecosystem condition index. By calculating the value of the index over time, the trajectory of ecosystem condition merges, and predictions can be made about future condition, should the current situation continue. This trajectory modelling can then form a baseline against which to evaluate possible management actions under a variety of climatic scenarios to identify those most likely to improve the condition of the Coorong.     

Exergy,ecosystem functioning and efficiency in a coastal lagoon: The role of auxiliary energy

Exergy, as the sum of energy and information contained in a given system due to living organisms, can act as a quality indicator of ecosystems. Here, we investigated the exergy of Marsala Lagoon (Mediterranean Sea), along with microbial (prokaryotic and heterotrophic nanobenthos) biomass, prokaryotic heterotrophic production and extracellular enzymatic activities, and the biochemical composition of sediment organic matter. The aim of the study was to assess the role of auxiliary energy (e.g. hydrodynamic stress) in the ecosystem functioning and efficiency of a ‘detritus sink’ lagoon. Samples were collected at sites characterized by contrasting hydrodynamic and trophic conditions. Exergy transfer through the benthic microbial loop was influenced by two main factors: (1) organic matter bioavailability; and (2) hydrodynamic forcing. At both sites, the values of total exergy were higher in summer than in winter, and the specific exergy decreased from winter to autumn, along with increasing auxiliary energy. Our data indicate that in coastal ‘detritus sink’ systems, auxiliary energy sources can have a crucial role in exergy transfer and ecosystem functioning through modifying the efficiency of transfer to higher trophic levels of the refractory organic detritus, which is otherwise lost by burial in the sediment. As coastal lagoons are often intensively modified by human activities, we conclude that maintenance of the natural hydrodynamic regimes is a key factor in the preservation of the functioning of lagoon ecosystems and of their provision of goods and services to humans.     

乐清湾生态系统脆弱性研究

随着海洋经济的开发与发展,海洋生态环境被破坏的问题日益突出,生态系统变得越来越脆弱.从浙江典型海湾乐清湾入手,分析了乐清湾生态系统脆弱性形成的机制,即自然和人为多种复杂动力因素形成的相互耦合作用下导致生态系统出现了脆弱性,其脆弱性可分为固有脆弱性和特殊脆弱性两类.固有脆弱性主要由陆海动力作用形成的,包括径流、气温、降水、波浪、潮流等环境因素.特殊脆弱性由人类开发活动作用形成的,主要包括海岸工程、滩涂围垦、水产养殖、污染等非环境因素.综合以上原因,指出了乐清湾生态系统处于亚健康状态,并已接近不健康边缘,生态系统极其脆弱,虽然生态系统的主要服务功能尚能发挥,但已不能满足海洋功能区划的要求,严重影响到海洋经济的可持续发展.乐清湾生态系统脆弱性具体表现在以下几个方面:(1) 水体受无机氮和活性磷酸盐污染严重,富营养化程度显著,氮磷比失衡,春季全湾水质为劣四类,夏季76%的海域水质为四类或劣四类;(2) 海湾自然水域实际面积缩小近四分之一,纳潮量相应减少了近5.79%;(3) 生物多样性降低,总生物量和物种数逐年下降,海洋食物链已经遭到严重破坏,生物群落结构发生明显改变;(4) 养殖区沉积物质量下降,在水动力作用下易造成"二次污染";(5) 周边的渔业经济下滑,捕捞鱼类个体偏小,且低值鱼类较多.最后对乐清湾生态系统脆弱性修复提出了对策和建议,主要应落实海洋环境目标管理责任制、加强入海污染物控制、运用生态学原理和技术防治海水养殖污染、利用大型海藻修复水域富营养化以及建立海洋生态环境监测预报和执法管理体系,使海洋生态系统重新进入良性循环,为海洋资源可持续利用提供发展空间.