Abstract
The Southern Adriatic Sea is a dynamic region under the influence of diverse physical forces that modify sea water properties as well as plankton dynamics, abundance, and distribution in an intricate way. The most pronounced being: winter vertical convection, lateral exchanges between coastal and open sea waters, and the ingression of water masses of different properties into the Adriatic. We investigated the distribution and abundance of tintinnid species in this dynamic environment in pre- and post-winter conditions in 2015/2016. A strong ingression of the saline Levantine Intermediate Water, supported by the cyclonic mode of the North Ionian Gyre in 2015 and 2016, in December was associated with a high diversity of oceanic species. An unusual spatial distribution of neritic-estuarine species Codonellopsis schabi was observed in deeper layers along the analyzed transect, which emphasizes the strong influence of physical processes on deep water biology in the South Adriatic. A shift of population toward greater depths (mesopelagic) and modification of deep sea community structure was recorded in April as a consequence of the winter convection-driven sinking of tintinnids. Our findings indicate that tintinnid abundance and composition is heavily influenced by physical conditions and they are good indicators of the impact of physical forces, including climate changes, on marine environment.
Highlights
Tintinnid ciliates are a common component of planktonic communities and they are present in all of the world’s oceans [1,2]
Seasonal changes in the water column structure, in particular due to the winter vertical mixing, which happens in specific hydro-meteorological conditions with different strength in different years, as well as the ingression of different water masses into the Adriatic, can cause marked shifts in the occurrence and abundance of tintinnids in post winter periods. During both investigated periods physical forces created environmental conditions that were of crucial significance for the spatial and temporal distribution of tintinnid ciliates in the southern Adriatic
Two different types of tintinnid horizontal distribution could be defined in the two investigated periods
Summary
Tintinnid ciliates are a common component of planktonic communities and they are present in all of the world’s oceans [1,2]. Of planktonic food webs has focused significant attention on microbial populations, and tintinnids have been identified as ideal organisms for studying changes in the structure and composition of microzooplankton [8,9]. Their distribution is related to hydrographical conditions and they have been used as indicators of upwelling [2]. All of the investigations of tintinnid vertical distribution in the open southern Adriatic were done by using 53-μm zooplankton nets. Since 1990 there have been no investigations of vertical distribution of open sea tintinnids in the Adriatic Sea and
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