Abstract
The analysis of nutrient concentrations in surface sediments is a reliable tool for assessing the trophic status of a water body. Nitrogen and phosphorus concentrations are strongly related to the sediment characteristics but are mainly driven by anthropogenic impacts. The results of the determination of total nitrogen and total inorganic and organic phosphorus in surface sediments of the lagoons and ponds of the northwestern Adriatic Sea (Marano-Grado, Venice, Po Delta, Comacchio Valleys, Pialassa della Baiona) show the merit of this approach. Indeed, when previous data are available, the ratio between the actual and background values can provide useful information on the trophic changes that have occurred in the most recent times, and the results can also explain the conditions present in less studied environments. In this context, numerous studies performed in the Venice lagoon since the second half of the 20th century during different environmental scenarios provide mean concentration ranges and propose the main causes of changes. The results of single datasets available for the other lagoons fall into scenarios that occurred in the Venice lagoon. At present, the most eutrophic basins are Pialassa della Baiona, the Po Delta lagoons and ponds and the Comacchio valleys due to industrial effluents, fish farming and clam harvesting, respectively, whereas the Venice lagoon is now experiencing environmental recovery.
Highlights
This paper aimed to integrate the knowledge on the nitrogen and phosphorus concentrations in the transitional water systems (TWSs) of the northern Adriatic Sea with particular reference to the Venice lagoon, of which a high number of data is available
The mean values of the dry density, the percentages of the fine fraction7and concentrations of nutrients in the surface sediments of the single and total TWSs are reported in Figure 2 and Table S1 (Supplementary Material)
The highest density was recorded in the Venice lagoon (0.96 g dwt cm−3), whereas Pialassa della Baiona and the Comacchio valleys showed the lowest values
Summary
In transitional water systems (TWSs; lagoons, ponds, deltas, estuaries, fjords), nutrient concentrations in surface sediments are key parameters strictly related to changes of anthropogenic impacts [1,2,3], mostly eutrophication [3,4,5,6,7,8], river inputs [9,10,11] and clam harvesting [12,13,14,15,16]. Since the Second World War, the rapid increases in industrial activities, agriculture, urban centers and tourism have profoundly altered the trophic conditions of the TWS [4,5], and sediments have proved to be an excellent litmus paper of the changes taking place. They accumulate nutrients [17,18] and pollutants [19,20,21], above all, during the death of primary producers and the settlement of suspended particles [22,23]. The same impacts, especially the increase in trophy with abnormal development of macroalgae nuisance, affected other TWSs both in Italy and in many other countries worldwide [5,6]
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