Freshwater and nutrient discharges by rivers were analysed in the northeastern Adriatic continental shelf from 1998 to 2008, in order to assess their role in the biogeochemistry of this coastal zone, ...as well as their potential future changes due to the effects of climate variability and anthropogenic pressure. River water loads (up to 6.05 km3 yr−1) and transport of nutrients (up to 13,200 t N yr−1 for TN, 86 t P yr−1 for TP and 12,400 t Si yr−1 for Si(OH)4) were high from 1998 to 2002, but they decreased by over 70% during the driest years 2003, 2005, 2006 and 2007. The precipitation in the surrounding continental region (average of 1371 mm yr−1) is the major forcing that regulates the runoff in this area, with peaks in early spring and autumn that are associated respectively to negative phases of Mediterranean Oscillation index and positive phases of West Mediterranean Oscillation index. This finding, together with the minor contribution of snowmelt in early spring (up to 3.2·10−5 kg m−2 s−1), indicates that the dynamics of the natural water cycle still overtake in this coastal zone the effects of anthropogenic usage of continental waters.
During the last four decades, the northeastern Adriatic continental shelf has been subjected to an increasing pressure due to a high river transport of nitrogen and, currently, only a deep phosphorus deficiency in total (TN/TP = 49–405) and inorganic (DIN/PO4 = 37–418) river nutrient pools prevents its severe eutrophication. By contrast, the decrease of river loads of nutrients from 2003 to 2007 indicates that recurrent water crisis might significantly lower the trophic level in this coastal zone in the future. In this perspective, other allochthonous sources of nutrients, like sewage loads, atmospheric deposition and benthic fluxes might become more important for their balance, with possible implications on the structure of this ecosystem.
► Runoff in the Gulf of Trieste is mainly regulated by the precipitation, that varies as a result of climatic oscillations. ► Runoff and nutrient transport by rivers has strongly decreased in the northeastern Adriatic in the period 2003-2007. ► The Gulf of Trieste is subjected to overloads of nitrogen and silicon with respect to phosphorus. ► A deep phosphorus deficiency prevents the severe eutrophication of this coastal zone. ► Repetitive shortages of continental waters might lower the trophic level of this coastal environment in the future.
Parameters relevant to the study of eutrophication processes in the northeastern Adriatic (NEA) during the period 2000–2009 were analysed and compared with a previous period (1972–1999). The data ...used in this study were collected at two stations in the coastal zone up to 13 NM off Rovinj (western Istria). The more recent period was characterised by a strong reduction of the Po River flow rate and different circulation regime with the more frequent inflow of high salinity and oligotrophic water from the central Adriatic. Change in the circulation was evidenced by lower frequencies of the Istrian Coastal Countercurrent (ICCC) as compared to the Eastern Adriatic Current (EAC) after 2000, particularly in spring. As a consequence, a marked increase in surface salinity and decrease in orthophosphate and chlorophyll a concentrations at two stations in the period 2000–2009 occurred. In contrast, during late winter and in spring of the more recent period, dissolved inorganic nitrogen (DIN) concentrations were higher, despite the lower freshwater discharge and increased inflows on nutrient-poorer water. This DIN increase was very probably due to an enhanced reduction of orthophosphate concentration after 2000, limiting further the phytoplankton growth, resulting in a more marked accumulation of unused DIN. The obtained results showed that the eutrophication pressure was markedly reduced in the NEA during 2000–2009 in respect to the previous period.
In this study, an investigation of a new thunderstorm intensity index (TSII) derived from lightning data is performed, along with its relationship to rain, wind, hail and waterspouts as well as ...instability indices (CAPE, LI, KI, and DLS). The study area is located in the northeastern Adriatic and includes various terrain types in a relatively small area (coastal, flatlands, hills and valleys, and mountain regions). The investigated period covers 11 years (2008–2018). The mathematical algorithm standing behind the TSII is based on the well-established methodology of lightning jump, allowing us to recognize areas where intensification in thunderstorms occurred. Our results suggest that these areas (with a positive TSII) experience significantly higher rain intensities and have higher total amounts of precipitation compared with areas where thunderstorms did not generate a TSII. Moreover, 76% of thunderstorm hail cases were associated with the presence of a TSII within a 15 km distance. The maximum reported wind speed also has higher values on a day with a TSII. Out of 27 waterspout events associated with lightning, 77% were related to a TSII. Due to the good spatial (3 km × 3 km) and high temporal (2 min) resolution of lightning data, the TSII can recognize even a local and short-lived intense system that is often misread by radars and satellites due to their inferior temporal resolution. The TSII is designed to be used as a climatological and diagnostic variable that could serve in lieu of more established data sources (e.g., station measurements and observations, radar imagery, etc.) if they are unavailable.
Detailed mapping of coastline in Vinodol Channel and adjacent bays in the Kvarner area (Northern Adriatic Sea) revealed the existence of well expressed submerged notches ranging in their elevation ...from 45 to 115 cm below mean sea level. Noticeable difference in the height of these presumably coeval tidal notches is attributed to neotectonic movements since the Roman times. The difference of ∼
0.1 m on opposite parts of Vinodol Channel is in accordance with the presumed thrusting tectonics in the adjacent Vinodol Valley. The deeper position of coeval tidal notches in Bakar Bay (the drowned part of Vinodol Valley) indicates it is the tectonically most active zone. Investigation of tidal notches in this case complements information from the solid rock geology and measurements of recent tectonic movements revealed by GPS positioning. Moreover, it indicates the potential of detailed mapping of tidal notches for neotectonic research in some coastal areas.
This paper examines disposal of metals and the origin, characteristics, and distribution of sedimentary organic matter (SOM) in a Mediterranean karstic estuary in the north-eastern Adriatic. This ...environment offers a real-time, small model system for studies of geochemical processes in microtidal Mediterranean estuaries that are infilling with sediments and classified as river-dominated disequilibrium estuaries. The results have shown that the longitudinal distribution of heavy metals in sediments follows the sedimentation dynamics and deposition pattern of river-borne, clay mineral particles. The highest concentration of metals was found in the restricted upper part of the estuary, characterized by rapid deposition of clay particles and terrestrial sedimentary organic matter, and decreases toward the open sea. The vertical distribution of metals in sediment cores depends on the prevailing pH and Eh conditions. Significant increases of the concentrations of metals in the uppermost strata are the result of recent anthropogenic inputs. The share of the terrestrial component in SOM, estimated by N/C
org atomic ratios and δ
13C values, decreases with distance from the river mouth. The small vertical variation in δ
13C values of SOM indicates that a fast sedimentation rate overrides the diagenetically determined decomposition. The results obtained indicate that river-borne inorganic particles, natural terrigenous organic material, and anthropogenic metal loads are trapped in sediments of the estuarine system. Under the prevailing conditions, there is negligible transport towards the open sea.
CTD data were collected weekly during 20 cruises from May to September 2003 over a 19 station grid in a coastal region of the northeastern Adriatic Sea as part of the Adriatic Sea Integrated Coastal ...Areas and River Basin Management System Pilot Project (ADRICOSM). Relative geostrophic velocities indicated fine scale circulation patterns in the area consisting of two pronounced circulation cells, of cyclonic and anticyclonic character, and that were present in the area for most of the investigated period. These motions were induced primarily by spatial variations in the temperature field and may be strengthened during episodes of very strong northeasterly bora wind, when the investigated region is not heated (cooled) uniformly.
The variability of the sea surface temperature (SST) of the Gulf of Trieste (northeastern Adriatic Sea) is studied using satellite observations spanning 2000–2006. After interpolation and validation ...of the SST data with in situ observations near Trieste, the satellite data are used to compute various statistical estimates (7‐year, yearly and monthly means and empirical orthogonal functions modes). The main results obtained are: 1. The SST in the Gulf of Trieste is mostly variable at the seasonal scale, with temperature differences between summer and winter of ∼14 and ∼16°C in the northern and southern areas, respectively. The larger seasonal variations in the northern section are related to the Isonzo and Tagliamento river runoffs and to its shallower bathymetry. In the mean, the meridional SST difference between north and south is only ∼2°C. 2. Significant interannual variations are observed, with winter 2001 and summer 2003 showing the largest monthly anomalies (2–3°C). Most of the seasonal and interannual variations are related to variability in the local heat flux with a time lag of about 2 months. No robust long‐term cooling/warming trend is apparent in the observations. 3. The spatial structure of the SST in the Gulf is affected by the Isonzo and Tagliamento rivers (to the north), the warmer Adriatic water (to the south), the nonuniform warming in spring and wind induced mixing and cooling (to the east). The latter effect is mostly in the form of rapid temperature changes triggered by strong Bora events.
Fatty acids and pristane/heptadecane (Pr/C17) ratio were analysed in zooplankton samples collected with a sediment trap in the northeastern Adriatic Sea from April 1991 to June 1992 in 2 to 6 wk ...intervals. Saturated (SAT; 22 to 68% of total fatty acid mass fraction), monounsaturated (MONO; 20 to 39%), and polyunsaturated (PUFA; 6 to 49%) fatty acid proportions, total fatty acid mass fraction (2.3 to 46.5 mg g−1 dry wt), and Pr/C17 ratio (0.5 to 27) varied significantly during the investigated period. Unusually low fatty acid mass fractions (2.3 to 5.1 mg g−1 dry wt), PUFA proportions (6%), and Pr/C17 ratio (<1) measured in summer 1991 were ascribed to a drastic zooplankton starvation due to a mucilage event, a phenomenon that can occur periodically (every 10 to 50 yr) in the region. Low PUFA proportions (12%) were also measured in winter/early spring 1992, but the C14:0 and C16:1 proportions, and Pr/C17 ratio (9 to 27) exhibited their highest values of the investigated period. This indicated more favourable feeding conditions and significant phytoplankton contributions in the zooplankton diets than in summer 1991. The highest total mass fraction (12.2 to 46.5 mg g−1 dry wt) and PUFA proportions (30 to 49%) were observed during spring and autumn, when the food supply was probably sufficient and diverse. The oleic acid (C18:1n9) proportions (12 to 22%) in the northeastern Adriatic were higher than in other marine regions.
The issue of plastic pollution has dramatically intensified in the recent years. Our study investigates extensive plastic contamination of a sandy beach on a small Adriatic island. The beach was ...sampled on three occasions, in 2013, 2020 and 2022, using 1 m2 quadrats placed along the lower and upper strandlines, resulting in average litter concentrations of 385 ± 106, 1095 ± 522 and 129 ± 37 item m−2, respectively. The lower size limit of collected litter was 1 mm, thus including large microplastics. Plastic fragments (49–74 %) and plastic pellets (15 %–37 %) were predominant litter categories. The proportion of fragments is significantly higher during the tourist season with a more intensive cleaning regime (April–October), as opposed to the off-season (November–March). Fisheries and aquaculture litter was identified as a relevant source of pollution. More research is needed in the future into the microplastics smaller than 1 mm.
•Marine litter on an island beach in the Adriatic was assessed in January 2013, July 2020 and May 2022•The greatest average concentration of plastic litter was 1,095 ± 522 item m-2, recorded in 2020•Plastic fragments were the prevalent litter type, with proportions ranging from 49% to 74%.•Plastic pellets and ear sticks were also present in high concentrations•Aquaculture and fisheries litter were recognised as important sources of litter
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