The mucilage phenomenon in the northern Adriatic Sea. A critical review of the present scientific hypotheses

In the summers of 1988, 1989, and 1991 large quantities of sticky mucilaginous masses occurred in the Adriatic Sea, particularly in its northern part. The mucilage phenomenon has been studied by scientists during past events, but the previous scientific reports back to the thirties of this century. Great efforts have been made since 1988 to understand the nature of the phenomenon. Although remarkable scientific results have been achieved, many questions related to such a complex phenomenon have remained open. In this paper results and hypotheses related to the chemical and biological composition, causes, triggering mechanisms, and responsible organisms for the mucilage phenomenon are briefly reviewed. Finally, some suggestions for future researches are proposed.     

Human health implications associated with mucilage in the northern Adriatic Sea

Mucilage in the northern Adriatic Sea is well known for its negative impact not only on the ecology of the affected area and on fishing activities but on tourism as well. The microhabitat mucilage creates in the sea can provide favourable conditions for the growth and/or survival of some environmental microorganisms that include human opportunistic pathogens. It also seems to favour the selective development of some marine toxic algae. Finally, mucilage can concentrate chemical contaminants from surrounding waters, hence increasing their bioaccumulation in seafoods. This paper examines the possible direct and indirect effects on human health of mucilage and other forms of marine aggregates.     

Significance of bacteria in the mucilage phenomenon in the northern Adriatic Sea

Episodes of massive mucilage formation in the northern Adriatic Sea have been recorded for over a century but their cause is still a matter of conjecture and debate. It is generally thought that mucilage forms due to copious polysaccharide exudation by phosphorus limited algae. In this paper we develop the thesis that bacteria play major roles in mucilage formation. We argue that mucilage is largely produced as a consequence of bacteria-organic matter interactions and bacterial capsular polysaccharide synthesis. Ectohydrolytic enzymes of bacteria are critical in producing long-lived polysaccharides. Further, bacteria cause efficient P regeneration, particularly intensely in microscale features e.g. phycospheres, detritus and aggregates. Bacteria thus help sustain high rates of primary production despite vanishingly low levels of phosphorus in the bulk phase seawater. We integrate these roles of bacteria into a conceptual model which emphasizes microscale interactions of microbes within a seawater gel matrix as the basis for a mechanistic understanding of the accumulation of long-lived polysaccharide to form mucilage.     

Structure/function/activity relationships in marine snow. Current understanding and suggested research thrusts

Marine snow and marine snow components contribute to the mucilage phenomenon in the northern Adriatic Sea. Of special relevance is the matrix material, composed of extracellular polymeric substances, which are packaged into fibrils of colloidal dimensions. These 0.005 micron diameter fibrils are physical units of mucilage which can be visualized by transmission electron microscopy (TEM). They form polymer bridges between the various biotic and mineral components of marine snow, creating three-dimensional networks which affect floc porosity, density and settling behaviour. Recent observations of the matrix by TEM reveal complex fibril-delimited channels and capillary systems which partially traverse marine snow flocs and which are postulated to play roles in anomalous settling. Considering the marine snow floc as a microecosystem, the relationships between ultrastructure, chemistry and environmental properties are being explored. On the assumption that colloidal matrix materials, including those released into the bulk water, might provide advance information on anomalous floc behaviour, two new methods are recommended for monitoring the northern Adriatic Sea. One is a technique for chemical quantification of colloidal organic carbon. The other uses TEM, applied to water fractions derived from cascade ultracentrifugation, to estimate fibril quantities as a proportion of colloidal organic carbon.     

Interaction between specific hydrological and microbial activity leading to extensive mucilage formation in the northern Adriatic Sea

The massive formation of marine snow and the senescent stage of it, the mucilage, is a phenomenon largely restricted to the Adriatic Sea. In this contribution the major environmental factors potentially leading to the formation of this mucilage are discussed. It is proposed that the specific hydrological conditions in combination with severe phosphorus depletion lead to excessive formation of colloidal organic matter by phytoplankton. This colloidal organic matter coagulates to marine snow due to the low-turbulence regimes prevailing in the water column. Subsequently, this marine snow is colonized by bacteria which, in turn, produce and release copious amounts of capsular polymers into the matrix of marine snow. It is speculated that a significant fraction of the later stages of marine snow (mucilage) consists of bacterial-derived organic matter which has been shown to be semi-labile to refractory for further bacterial utilization. The marine snow matrix acts as efficient adsorption site and allows the bacteria to utilize scavenged molecules from the ambient water. Thus it is proposed that the matrix ages without significant biotic degradation.     

Seasonal fluctuations of DIN/DIP and DON/DOP ratio in the northern Adriatic Sea

Within the frame of PRISMA 1 "Biogeochemical cycles" research project (April 1995-January 1996) the quantities and the compartments of dissolved nitrogen and phosphorus have been studied in the northern Adriatic basin, considering also the organic pools. The research aimed to provide a better understanding of nutrient availability and to investigate the possible factors which promote the phenomenon of mucilage formation. For this purpose, the availability and the ratios between dissolved nitrogen and phosphorus considering both inorganic and organic fractions have been studied in relation to variations of river outflow and of biological activities. The results obtained reveal the large importance of organic nitrogen (annual average 16 microM) and phosphorus (annual average 0.13 microM) in contributing to the total nutrient availability (annual average total dissolved nitrogen: 29 microM and phosphorus: 0.18 microM) and the pronounced seasonal variability mainly ascribable to biological processes of uptake and remineralization. Furthermore, beside the well documented unbalanced ratio between inorganic nitrogen and phosphorus, the results obtained point out, for the first time, the unbalance also in the organic compartment (ratio between organic nitrogen and phosphorus ranges between 50 and 530), whose consequences might be important in relation to the phenomenon of mucilage formation.     

Marine radioecology and waste management in the Adriatic

This paper gives a review of marine radioecology research in the Adriatic area carried out by the Radiation Protection Unit of the Institute for Medical Research and Occupational Health. Measurements of radioactivity in the Adriatic started in 1963 as a part of an extended monitoring programme of radioactivity in Croatian environment. The main sources of radioactive contamination of the Adriatic Sea are the fallout from past nuclear weapon testing conducted in the atmosphere and the Chernobyl accident. In 2005, the activity concentrations of fission radionuclides were detectable at very low levels in all environmental samples collected on the Adriatic. The 90Sr data obtained from long-term monitoring were used to estimate the upper limit of the Adriatic seawater turnover time, which turned out to be (3.4 +/- 0.4) years. Detailed knowledge about seawater circulation, including the turnover time is essential for planning an overall communal and other wastewater management on the Adriatic coast. The paper concludes with the prospects for future marine radioecological investigations.     

The Renaissance of Plant Mucilage in Health Promotion and Industrial Applications: A Review

Plant mucilage is a renewable and cost-effective source of plant-based compounds that are biologically active, biodegradable, biocompatible, nontoxic, and environmentally friendly. Until recently, plant mucilage has been of interest mostly for technological purposes. This review examined both its traditional uses and potential modern applications in a new generation of health-promoting foods, as well as in cosmetics and biomaterials. We explored the nutritional, phytochemical, and pharmacological richness of plant mucilage, with a particular focus on its biological activity. We also highlighted areas where more research is needed in order to understand the full commercial potential of plant mucilage.     

Replacing Emulsifier in a Prebiotic Ice Cream: Physical and Chemical Evaluation and Acceptance

Consumers are very interested in the development of new food products, which presents sensorial, nutritional, and physicochemical quality. Thus, this study aimed to evaluate the addition of chia seed mucilage as an emulsifier substitute on the physical and chemical characteristics and on acceptance of chocolate-flavored prebiotic ice cream (with inulin). The ice creams had good physicochemical characteristics: The sample with the lowest mucilage content (0.6 g/100 g) showed higher resistance to melting, however, showed less overrun. Ice creams with higher concentrations of mucilage (1.2 or 1.8 g/100 g) had higher overrun. All ice creams had scores between 6 and 7 in the evaluated attributes, indicating that consumers liked slightly to moderately. The fatty acid composition of the mucilage was predominantly polyunsaturated fatty acids. It can be concluded that it is possible to develop prebiotic ice cream with chia seed mucilage as an emulsifier that have appropriate chemical composition and acceptance.     

鞋用胶水和溶剂毒性防范措施初探

目的了解福建省使用的鞋用胶水和溶剂的毒性状况。方法１９９７～１９９８年间，对福建省境内规模较大的制鞋企业常用的鞋用胶水和溶剂共４５份样品进行毒性检测鉴定。结果各样品的主要成份为丁酮、甲苯、汽油等，其急性毒性分级均为低毒。结论提出如下毒性防范措施：大力推广无苯胶、加强生产车间内通风排毒措施、对进入我省市场的无苯胶和各类溶剂加大监督力度、开展作业场所的定期监测和作业人员的职业性健康检查等。     

不同成分鞋胶的急性吸入毒性实验研究

目的：为观察不同成分鞋胶对小白鼠的急性毒性作用。方法：选择分别含甲苯与丁酮、甲苯及酯类的鞋胶,通过急性吸入毒性实验的方法,观察不同成分鞋胶对小白鼠的半数致死浓度（ＬＣ５０）及毒性作用表现。结果：含甲苯与丁酮的鞋胶其ＬＣ５０最低,只含酯类的鞋胶ＬＣ５０最高;雌性小白鼠的ＬＣ５０小于雄性小白鼠;同种成分的鞋胶环境温度高时ＬＣ５０低;含甲苯与丁酮的鞋胶小白鼠染毒后产生的症状多、恢复时间长,病理可见肝肺出血点。结论：含甲苯的鞋胶对人体毒性大,应在鞋业中禁用含三苯的胶水。     

Polychlorinated biphenyls (PCBs) in the marine environment, particularly in the Mediterranean

Polychlorinated biphenyls (PCBs) possess a low water solubility, a high n-octanol/water partition coefficient, and a high persistence, particularly those which are highly chlorinated. Because of these properties they are bioaccumulated in many organisms in the environment. PCBs are still manufactured industrially and used in the Mediterranean countries (e.g., Italy, Spain, and France). Production figures for these countries and for the FRG, the United Kingdom, and the United States between 1973 and 1979 are given. The concentrations of PCBs in marine air, water, sediments, microplankton , algae, mussels, fish, and other marine organisms including seabirds from the Mediterranean area are reviewed and compared with PCB concentrations in marine samples from non-Mediterranean regions. Levels of PCBs in seawater are highest in the western and central Mediterranean. The data for mussels and fish give a clear indication that the PCB levels are higher in the Northwest and the Tyrrhenian Sea than in the eastern Mediterranean. The FDA in June 1979 set 2 mg/kg as the temporary maximum concentration for PCBs in fish and shellfish. The PCB residues in some fish from the northwestern Mediterranean and Tyrrhenian Sea and in some mussels from the Adriatic Sea are higher than this limit. The amount of PCBs ingested via food by the Mediterranean population is unknown.     

Metal Content and Toxicity of Produced Formation Water (PFW): Study of the Possible Effects of the Discharge on Marine Environment

A preliminary chemical and ecotoxicological assessment was performed on the produced formation water (PFW) and superficial sediment around a gas platform (Fratello Cluster), located in the Adriatic Sea (Italy), in order to evaluate the effects of PFW discharged from the installation. The ecotoxicological bioassays, with the marine bacterium Vibrio fischeri and the sea urchin Paracentrotus lividus, were associated with chemical data to estimate the possible effects on living organisms. PFW collected on the platform was toxic, but no significant effect was recorded on marine sediment. Only the sediment station nearest to the discharge point showed higher values of some contaminants (zinc and arsenic) in comparison to other sites and only some stations showed low toxicity.     

Impact of “ecological” post-harvest processing on the volatile fraction of coffee beans: I. Green coffee

Green coffees produced by three variants of the wet process and a new “ecological” process were characterised for their aroma using combined headspace solid-phase microextraction/gas chromatography–mass spectroscopy (HS-SPME/GC–MS) and headspace solid-phase microextraction/gas chromatography–olfactometry (HS-SPME/GC–O). The effect of each post-harvest processing operation on the volatile fraction of the coffee produced was studied, particularly the effect of reducing the amount of water used in the process. The comparison of the green coffees from the different treatments revealed the importance of mucilage removal in distinguishing between the samples, and showed the merits of microbial mucilage removal in water to obtain coffees with a better aroma quality. These latter coffees were in fact characterised by pleasant and fruity aromatic notes, whereas those obtained after mechanical mucilage removal used in the ecological process were characterised by volatile compounds with an unpleasant note.     

盐酸曲马多胶浆剂在腹部吸脂术中的应用

目的应用盐酸曲马多胶浆剂镇痛以减少腹部吸脂术中利多卡因用量的探讨。方法采用两种局部麻醉方式，对腹部吸脂术患者进行利多卡因用量的比较。对照组7例，采用常规灌注液分区麻醉，利多卡因浓度0．05％；观察组8例，采用我们白行研制的盐酸曲马多胶浆剂，采取直肠给药方式，灌注均一次完成，灌注液利多卡因浓度为0．01％。结果两组患者主观感觉麻醉效果均满意。但对照组利多卡因用量范围37．5～41．7mg／kg，灌注液用量范围75．0～83．3ml／kg；而观察组利多卡因用量范围10．9～12．5mg／kg，灌注液用量范围109．0～125．0ml／kg。由吸出液静置后颜色判断，观察组比对照组出血量明显减少。结论在腹部吸脂术中，应用盐酸曲马多胶浆剂直肠给药镇痛，可以大大减少利多卡因用量，从而增加灌注量和提高手术安全性。     

利多卡因胶浆配伍米索前列醇用于人工流产的临床疗效观察

目的:探讨利多卡因胶浆配伍米索前列醇用于人工流产的临床疗效。方法:将要求人工流产的孕妇360例随机分为三组:A组:术前1 h舌下含服米索前列醇0.2 mg,利多卡因胶浆5 m l注入宫腔;B组:术前利多卡因胶浆5 m l注入宫腔;C组:术前1 h舌下含服米索前列醇0.2 mg,阴道后穹窿放置米索前列醇0.2 mg。结果:A组在扩张宫颈、缓解扩宫时疼痛、减少术中出血量方面优于B组和C组,在缓解吸宫时疼痛、预防人工流产综合反应方面优于C组。经统计学分析,有显著性差异。结论:利多卡因胶浆配伍米索前列醇应用于人工流产是一种安全、经济、简便、有效的方法,值得临床推广和应用。     

Natural radionuclides in seafood from the central Adriatic Sea (Italy)

Activity concentrations of 21?Po, 21?Pb, and ??K were measured in different samples of marine organisms from the central Adriatic Sea. The marine organisms were purchased from the local consumer market during all four seasons of the year to evaluate the spatial and temporal distribution of the natural radioactivity. The concentration trend is the following: ??K > 21?Po > 21?Pb. ??K concentration ranged between 54.9 and 235.9 Bq kg?1 fresh weight, and the arithmetic mean of Pb concentration for all samples is <0.7 Bq kg?1 fresh weight. Po activity concentration ranged between 0.3 and 44.6 Bq kg?1 fresh weight; its arithmetic mean was 5.7 ± 7.2 Bq kg?1 fresh weight. Among the pelagic species, anchovy displayed the highest polonium concentration. The data obtained depend upon the type of marine organism and the period of sampling. Committed effective dose due to 21?Po ingestion from marine food for individuals in the two different population groups was calculated to be 95.9 and 466.4 μSv y?1, respectively.     

Aliphatic and Polycyclic Aromatic Hydrocarbons in Gulf of Trieste Sediments (Northern Adriatic): Potential Impacts of Maritime Traffic

The Gulf of Trieste (northern Adriatic) is one of the most urbanized and industrialized areas in the northern Adriatic, with intense maritime traffic experienced at multiple ports. The impact of maritime traffic on contamination by hydrocarbons in this area was assessed. Concentrations of hydrocarbons were higher near the expected contamination sources and still elevated in the adjacent offshore areas. Aliphatic hydrocarbons were mainly of petrogenic origin, with some contribution of biogenic origin. A continuous contamination by aliphatic hydrocarbons and degradation processes were hypothesized. Concentrations of total polycyclic aromatic hydrocarbons (PAH) were generally greater near the contamination sources. Compared to the prevailing pyrolytic origin, the petrogenic PAH origin seemed to be less important, but not negligible. Results revealed that intensive maritime traffic is a probable source of contamination by hydrocarbons in the investigated area, which is largely limited to areas near the contamination sources.     

Impact of “ecological” post-harvest processing on coffee aroma: II. Roasted coffee

The purpose of this study was to determine how water and microbial stages in post-harvest processing affect the volatile content of coffee. Following our aroma analysis carried out on green coffees, we turned our attention to roasted coffees. Coffees produced by three variants of the wet method, and by an ecological process, were compared after roasting. Three degrees of roasting were applied to gain a clearer picture of the differences in roasted coffee aromas by means of a volatile compound analysis. Changes in the post-harvest process actually led to aroma differences in roasted coffees, and with light roasting it was possible to more effectively distinguish between the four treatments based on aroma criteria. Coffee produced by the traditional wet method, with microbial stages, had a better aroma quality than coffee produced by the ecological method, which was purely mechanical. Moreover, in the microbial method, mucilage removal under water gave coffees with more fruity, floral and caramel notes, whereas dry mucilage removal gave more neutral coffees. These results confirmed the importance of microbial mucilage removal under water and tallied with the results of our previous study on green coffee. This work provides coffee producers and roasters with an insight into the volatile composition of roasted coffee depending on the post-harvest process used and degree of roasting applied.     

Distribution of hydrogen, oxygen and carbon isotopes in the atmosphere of Croatia and Slovenia

Monitoring of isotope distribution in the atmosphere included isotopes 2H, 3H and 18O in precipitation, and 13C and 14C in atmospheric CO2. This paper presents the results of atmospheric monitoring over Croatia and Slovenia overt the last few years. Monthly precipitations in Zagreb and Ljubljana had been collected since 1976 and 1981, respectively. Between 2000 and 2003 monitoring also included seven stations along the Adriatic coast. Tritium activity in precipitation shows seasonal variations that were most pronounced inland (at the continental stations Zagreb and Ljubljana) and were the smallest in the south Adriatic (Komiza and Dubrovnik). Mean annual tritium activity decreases from the north to the south Adriatic coast. Seasonal variations in delta2H and delta18O in precipitation follow the temperature variations at the sampling stations. Atmospheric CO2 was collected in Zagreb and Plitvice as a composite monthly sample. Both delta14C and delta13C showed seasonal variations. The mean annual 14C activities in Zagreb had been decreasing after the peak reached in the 1960s, and for the last three years the mean 14C activity (delta14C) remained about 30 per thousand.