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

2005 ◽  
Vol 6 (1) ◽  
pp. 5 ◽  
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.

Reconstructing the baseline population structure of the exploited bivalve Arca noae in the Northern Adriatic Sea

2021 ◽  
Author(s):  
Saskia Macharia ◽  
Rafał Nawrot ◽  
Michaela Berensmeier ◽  
Ivo Gallmetzer ◽  
Alexandra Haselmair ◽  
...  
Keyword(s):  
Adriatic Sea ◽  
Size Structure ◽  
Anthropogenic Impacts ◽  
Natural State ◽  
Published Data ◽  
Northern Adriatic Sea ◽  
Important Species ◽  
Northern Adriatic ◽  
Shell Bed ◽  
The Impact

<p>The Northern Adriatic Sea is one of the most impacted ecosystems worldwide with a long history of anthropogenic impacts, ranging from overfishing and bottom trawling to eutrophication, deoxygenation and pollution. The impact of these multiple pressures on populations of economically important species is often difficult to evaluate due to paucity of long-term monitoring data. The edible bivalve Noah’s Ark shell (<em>Arca noae </em>L.) was intensively harvested in the eastern Adriatic Sea until 1949-1950 when it suffered a catastrophic population collapse due to unknown agents. The assessment of its subsequent recovery is hindered by the lack of data on the population size structure prior to that event. To reconstruct the natural baseline state of populations of <em>A. noae</em> before the onset of extensive harvesting, we studied fossil assemblages from two 1.5-m-long sediment cores collected in the southern Gulf of Trieste (off Piran, Slovenia), both recording the last ~9,500 years.</p><p>The abundance and shell length of <em>A. noae</em> remained low in the lower part of the cores but increased strongly within the oyster-<em>Arca</em> shell bed corresponding to maximum flooding and early highstand sea-level phases (6,500-1,000 years ago). In contrasts, the top 8 cm of the core (the late highstand phase), marked by high concentration of pollutants and organic enrichment, contained only few and small (< 10 mm) <em>A. noae</em> shells. Moreover, no living individuals were found in grab samples taken from the two stations suggesting that the dense populations of <em>A. noae, </em><span>persisting </span><span>there</span> <span>for</span><span> several thousand years, </span>were locally extirpated in the 20<sup>th</sup> century. To evaluate population recovery in other parts of the NE Adriatic, we compared the size distribution of<em> </em>fossil<em> </em><em>A. noae</em> from the shell bed interval to the previously published data on living populations of this species sampled<em> </em>along Istrian peninsula between 1966 and 1978. Both fossil and extant populations were characterized by similar <span>median </span><span>size, </span><span>modal size </span><span>class and</span><span> proportion of </span><span>specimens > 50 mm </span><span>(minimal legal landing size). </span><span>These results suggest that within few </span><span>decades</span><span> after the </span><span>1949-1950 </span><span>mass mortality event </span><span>the size structure of populations </span><span>of</span> <span><em>A. noae</em></span> <span>have largely returned to their earlier, natural state.</span><span> The recovery was </span><span>spatially variable, however, as attested by</span><span> the decline of</span> <span><em>A. noae</em></span> <span>populations </span><span>due to loss of </span><span>suitable shell-bed habitat</span><span>s</span><span> in</span><span> the two </span><span>studied</span><span> station</span><span>s</span><span> off Piran.</span></p>

scholarly journals Seasonal and Interannual Trends of Oceanographic Parameters over 40 Years in the Northern Adriatic Sea in Relation to Nutrient Loadings Using the EMODnet Chemistry Data Portal

Water ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 2280 ◽  
Author(s):  
Federica Grilli ◽  
Stefano Accoroni ◽  
Francesco Acri ◽  
Fabrizio Bernardi Aubry ◽  
Caterina Bergami ◽  
...  
Keyword(s):  
Climate Changes ◽  
Management Practices ◽  
Adriatic Sea ◽  
Nutrient Concentrations ◽  
Data Series ◽  
Mean Flow ◽  
Northern Adriatic Sea ◽  
Po River ◽  
Northern Adriatic

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.

Stratigraphic changes in shell size of a turritellid gastropod in the Holocene fossil record of the Po prodelta (Northern Adriatic Sea)

2021 ◽  
Author(s):  
Angela Scheidl ◽  
Michaela Berensmeier ◽  
Rafal Nawrot ◽  
Paolo G. Albano ◽  
Adam Tomašových ◽  
...  
Keyword(s):  
Water Depth ◽  
Similar Pattern ◽  
Adriatic Sea ◽  
Size Structure ◽  
Shell Height ◽  
Sediment Cores ◽  
Northern Adriatic Sea ◽  
Shell Size ◽  
Northern Adriatic ◽  
Lower Abundance

<div> <p>Over the last century, the northern Adriatic Sea has faced multiple ecological threats such as hypoxic events, eutrophication, pollution by heavy metals and plastics, and bottom trawling. These impacts were associated with major changes in the composition of benthic communities, particularly a decline in the abundance of <em>Turritellinella tricarinata</em> (= <em>Turritella communis</em>), the dominant gastropod species in the previously widespread <em>Turritella</em>-biocenosis of the northern Adriatic muddy bottoms. In this study, we reconstruct changes in abundance and size structure of <em>T. tricarinata</em> populations over the last 6000 years to better understand the drivers responsible for its recent decline and to provide a historical baseline for assessing potential recovery.</p> <p>We studied sediment cores from two locations in the western Northern Adriatic Sea: (1) distal zones of Po prodelta based on a 3-meter-long gravity core collected at 31 m water depth comprising a condensed record of the last ~9,100 years, (2) proximal zones of Po prodelta based on five 1.5-meter-long piston cores taken at 21 m water depth in the Po prodelta, which capture the last 100-150 years. Core chronologies are based on radiocarbon-calibrated amino-acid racemization analyses of bivalve shells.</p> <p>We analysed changes in the abundance and shell height of <em>T. tricarinata</em> in each increment of the cores. In total, 600 specimens have been measured. All stations show a similar pattern in shell abundance: a climax in the early 20<sup>th</sup> century and a strong decrease in the late 20<sup>th</sup> century.</p> <p>The proximal records of Po prodelta show a negative correlation between abundance and median shell size, with larger size and lower abundance in the late the 20<sup>th</sup> century, a period characterized by recurrent severe hypoxic events. The 3-meter-long offshore core contains on average smaller specimens, but reflects a similar pattern: the number of larger specimens (>10 mm) and median shell sizes increase slightly towards the core top while total abundance declines. This trend towards larger shell size and lower abundance may reflect the complex effect of nutrient enrichment in a highly disturbed environment. During the last century <em>Turritella communis</em> might experience higher growth rates and lower predation but simultaneously reduced recruitment due to hypoxia and pollution.</p> </div>

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

Water ◽  
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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