Phytoplankton temporal dynamics in the coastal waters of the north-eastern Adriatic Sea (Mediterranean Sea) from 2010 to 2017

Abstract

Phytoplankton community structure was analysed from 2010 to 2017 at C1-LTER, the coastal Long-Term Ecological Research station located in the Gulf of Trieste, which is the northernmost part of the Mediterranean Sea. Phytoplankton abundance and relevant oceanographic parameters were measured monthly in order to describe the seasonal cycle and interannual variability of the main phytoplankton taxa (diatoms, dinoflagellates, coccolithophores and flagellates) and to analyse their relationship with environmental conditions. Overall, phytoplankton abundances showed a marked seasonal cycle characterised by a bloom in spring, with the peak in May. During the summer, phytoplankton abundances gradually decreased until September, then slightly increased again in October and reached their minima in winter. In general, the phytoplankton community was dominated by flagellates (generally <10 µm) and diatoms co-occurring in the spring bloom. In this period, diatoms were also represented by nano-sized species, gradually replaced by larger species in summer and autumn. Phytoplankton assemblages differed significantly between seasons (Pseudo-F = 9.59; p < 0.01) and temperature and salinity were the best predictor variables explaining the distribution of the multivariate data cloud. At the interannual scale, a strong decrease of the late-winter bloom was observed in recent years with the spring bloom being the main phytoplankton increase of the year.

Phytoplankton Dynamics in the Middle Adriatic Estuary, with a Focus on the Potentially Toxic Genus Pseudo-nitzschia

“…This was not in accordance with the results of Cetinić et al [4], who found the spring characterised by the highest phytoplankton abundance. In the Northern Adriatic, the spring peak was dominated by nanoflagellates and small diatoms, and a second slight increase in autumn was dominated by nanoflagellates, larger diatoms, and coccolithophores, as observed by Cerino et al [29].…”

First Restoration Experiment for Gongolaria barbata in Slovenian Coastal Waters. What Can Go Wrong?

“…The two sites in the Gulf of Trieste do not differ significantly in terms of substrata and exposure to winds and currents, since both can be defined as "rocky shallow moderately exposed" [56]. However, the Miramare MPA is located in an area that is subject to high nutrient availability in the spring and autumn periods due to riverine discharges, especially from the Isonzo River [76], while the Piran site is influenced mainly by smaller rivers [77]. Thus, we can assume that it is less eutrophic in general, even if nutrient data are not collected from such shallow waters, but at a distance of 1.3 km from the coast [77].…”

Ostracod Fauna: Eyewitness to Fifty Years of Anthropic Impact in the Gulf of Trieste. A Potential Key to the Future Evolution of Urban Ecosystems

“…In the northern Adriatic ecosystems and the GoT area, a review of numerous long term studies on river discharg, oceanographic features, plankton, fish and benthic compartments, collected since the 1970s revealed significant changes in mechanisms and trophic structures [53,73]. In detail, a gradual increase in eutrophication phenomena, characterized by significant hypoxic events at the bottom, was recorded during the 1970s until the mid-1980s [74,75,76], followed by a reversal of the trend, particularly marked in the 2000s [66,77]. This trend was attributed to a combination of the reduction in anthropogenic impact, mainly due to a substantial decrease of the phosphorus loads, and of climatic modifications, resulting in the decline in atmospheric precipitations and, consequently, of runoff [78,79].…”