Water temperatures followed the expected annual dynamics with winter 2012 minima (16.68 ± 0.24°C) and summer maxima (29.19 ± 0.16°C). No spatial variation in water temperature could be detected. Salinity exhibited seasonal fluctuations and reached maximum values (38.22 ± 0.26 PSU; 38.30 ± 0.59 PSU) in winter and autumn 2012, respectively, whereas the lowest values (27.73 ± 3.64 PSU) were measured in spring. Lowest

values were observed at stations 1 and 2 due click here to the freshwater discharged. Minimum pH value (8.11) was recorded in winter 2012, 2013, while the highest value (8.40) was measured in autumn. The harbour’s water was always well-oxygenated and reached maximum values in spring (17.04 ± 3.23 mg l−1) and minimum values in summer (9.44 ± 3.16 mg l−1). The concentration of DIN, SRP, and RS varied widely and showed excess nutrient during autumn and high concentrations in summer with an apparent excess of SRP. Seasonal and spatial variation of nutrient concentrations showed that highest values of DIN were observed in summer (41.50 ± 10.13 μM) and lowest registered UK-371804 in spring (5.52 ± 5.20 μM). Stations 1, 9 and 10 usually presented peaks of DIN. Nitrate was the most dominant nitrogen form in winter and summer 2012 (55.89%; 52.97%, respectively) with maximum values observed at stations 1, 9 and 10. Ammonium was the dominant

nitrogen form in spring and winter 2013 (57.40; 83.20%, respectively) with maximum values registered at stations 1, 7 and 9. Nitrite was the dominant during autumn (69.22%) with maximum values recorded at stations

6, 7 and 8. The highest SRP concentrations were measured in summer (5.93 ± 2.07 μM) and lowest in spring (0.85 ± 0.47 μM). Station 6 reached maximum values, 9.75 μM in summer and 9.60 μM in autumn. Highest values of RS were observed during summer (28.95 ± 14.13 μM) with maximum values at stations 1 and 2. The DIN/SRP ratio changed both seasonally and spatially. In general, DIN/SRP were lower than the algal N/P (Redfield ratio) throughout DOK2 most of the harbour stations, increasing to >16:1 only at station 1 (summer and autumn) and stations 9 and 10 (summer). Low DIN:SRP ratios (<5) during spring and winter 2013 suggested that nitrogen could be the principal limiting nutrient. The RS/SRP ratio underwent more complex seasonal changes. Except in winter 2012, the ratio RS/SRP was <16:1 all the year round. Higher ratios were observed in winter 2012, suggesting less demand for RS relative to SRP. This is consistent with high proportions of Si-requiring diatoms in the phytoplankton community during spring-winter 2013 and primarily non-siliceous forms in spring. From the analysed data, a visible change in phytoplankton community with regard to numerical abundance and species composition was evident among stations and in the seasonal cycle.