The Mechanism Controlling Plant Nutrient Concentrations in the Northern Adriatic Sea

Long-term data series (1971–2015) of physical and biogeochemical parameters were analyzed in order to assess trends and variability of oceanographic conditions in the northern Adriatic Sea (NAS), a mid-latitude shallow continental shelf strongly impacted by river discharges, human activities and climate changes. Interpolation maps and statistical models were applied to investigate seasonal and spatial variability, as well as decadal trends of temperature, salinity, chlorophyll-a and nutrients. This analysis shows that sea surface temperature increased by +0.36% year−1 over four decades. Annual mean flow of the Po River markedly changed due to the occurrence of periods of persistent drought, whereas the frequency of flow rates higher than 3000 m3 s−1 decreased between 2006 and 2015. Moreover, we observed a long-term decrease in surface phosphate concentrations in Po River water (−1.34% year−1) and in seawater (in summer −2.56% year−1) coupled, however, to a significant increase in nitrate concentration in seawater (+3.80% year−1) in almost all seasons. These changes indicate that the nutrient concentrations in the NAS have been largely modulated, in the last forty years, by the evolution of environmental management practices and of the runoff. This implies that further alteration of the marine environment must be expected as a consequence of the climate changes.

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Spatial and seasonal variability of fractionated phytoplankton biomass and primary production in the frontal region of the Northern Adriatic Sea

Mediterranean Marine Science ◽

10.12681/mms.189 ◽

2005 ◽

Vol 6 (1) ◽

pp. 5 ◽

Cited By ~ 1

Author(s):

M.R. VADRUCCI ◽

G. CATALANO ◽

A. BASSET

Keyword(s):

Primary Production ◽

Phytoplankton Biomass ◽

Adriatic Sea ◽

Size Structure ◽

Nutrient Concentrations ◽

Northern Adriatic Sea ◽

Northern Adriatic ◽

Frontal System ◽

Dissolved Phosphorus ◽

Point Total

Spatial and seasonal patterns of variation of fractionated phytoplankton biomass and primary production and their relationships with nutrient concentrations were analyzed along an inshore - offshore gradient and in relation to the presence of a frontal system in the Northern Adriatic Sea. Sampling was carried out in winter and summer during four oceanographic cruises (June 1996 and 1997, February 1997 and 1998) as part of the PRISMA II project. Water samples for determining nutrient concentrations, phytoplankton biomass (as Chla) and primary production (as 14 C assimilation) were collected at five optical depths. Sampling stations were located along 2 or 4 parallel transects arranged perpendicularly to the shoreline and the frontal system. The transects were located at such a distance from the coast that the frontal system crossed them at their halfway point. Total dissolved nitrogen (TDN) and total dissolved phosphorus concentrations (TDP) were 12.41 ± 3 .95 mM and 0.146 ± 0 .070 mM, respectively. The values in the two seasonal periods were similar, decreasing along the inshore-offshore gradient. Values for phytoplankton biomass and primary productionwere higher in the winter than the summer cruises, and decreased, in both seasonal periods, along the inshore / offshore gradient. Moreover, in both seasonal periods, picophytoplankton dominated both biomass and productivity, (56% and 44%, respectively) at stations beyond the frontal system, while microphytoplankton was more important at stations inside it (44% and 44%, respectively). Total phytoplankton biomass and primary production were directly related to nutrient concentrations. Regarding size classes, significant patterns of variation with nutrients were observed particularly for biomass. The results indicate that the size structure and function of phytoplankton guilds seem to be mediated by nutrient inflow, as well as by competitive interaction among size fractions.

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Trends of Nitrogen and Phosphorus in Surface Sediments of the Lagoons of the Northern Adriatic Sea as a Study Case

Water ◽

10.3390/w13202914 ◽

2021 ◽

Vol 13 (20) ◽

pp. 2914

Author(s):

Adriano Sfriso ◽

Alessandro Buosi ◽

Yari Tomio ◽

Abdul-Salam Juhmani ◽

Michele Mistri ◽

...

Keyword(s):

Surface Sediments ◽

Adriatic Sea ◽

Organic Phosphorus ◽

Anthropogenic Impacts ◽

Venice Lagoon ◽

Nutrient Concentrations ◽

Nitrogen And Phosphorus ◽

Northern Adriatic Sea ◽

Northern Adriatic ◽

Po Delta

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.

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