Abstract
Dissolved oxygen (DO) is a key element for the survival of marine organisms and is a supporting element in the current Water Framework Directive (WFD). DO deficiency is a common event that occurs in coastal environments such as estuaries and lagoons, but a long-term DO database that helps detect daily and seasonal oscillations is difficult to obtain with commonly used sampling and analytical procedures. In this work, a network of multi-parametric probes was deployed in the Marano and Grado Lagoon (northern Adriatic Sea, Italy) in order to obtain a dataset from the continuous monitoring of DO and complementary parameters. DO showed a high degree of variability both in terms of spatial and seasonal distribution and was dependent on solar radiation and water temperature. During the summer and in areas characterised by scarce water renewal, DO was below the threshold set as the minimum requirement for aquatic life, thus some water bodies (WBs) were classified as moderate sensu WFD. The inputs of freshwater discharge from inland and marine waters during tides are, however, able to well oxygenate most of the lagoon. These results will be useful in supporting the management and protection of this vulnerable environment.
Highlights
Accepted: 1 February 2022Lagoons are ecotones between marine and terrestrial environments and are globally widespread, covering variable surfaces ranging from 0.01 to more than 10,000 km2
Surface water temperature showed a high degree of variability ranging from the minimum of 3.0 ◦ C measured in December 2013 (M1) to the maximum of 33.5 ◦ C in June
The results showed that the highest content of Dissolved oxygen (DO) occurs in the early afternoon when the photosynthetic process has enriched the water with produced oxygen, whereas the breathing process prevails during the night and the DO is mostly consumed, reaching the lowest values in the early hours of the day
Summary
Lagoons are ecotones between marine and terrestrial environments and are globally widespread, covering variable surfaces ranging from 0.01 to more than 10,000 km. Lagoons are ecotones between marine and terrestrial environments and are globally widespread, covering variable surfaces ranging from 0.01 to more than 10,000 km2 They represent approximately 5.3% of the European coastline [1] and the Mediterranean Sea basin comprises approximately 600 lagoons. The goal of the WFD was to reach “good ecological status” for all European surface water bodies by 2015 (this deadline can be postponed by 2027 if certain exemptions are invoked), by taking into account biological, chemical and morphological conditions. The physico-chemical parameters such as transparency, temperature, salinity, dissolved oxygen and nutrient concentration are used to support the Published: 4 February 2022
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