Copepod Diel Vertical Distribution in the Open Southern Adriatic Sea (NE Mediterranean) under Two Different Environmental Conditions

Abstract

Diel vertical migration of the copepod the community was investigated in the open South Adriatic, in June 2020 and February 2021, under two very different hydrographical conditions. The influence of a winter wind-induced mixing event on copepod vertical migration at the species level was determined for the first time and compared to the situation in June when pronounced thermal stratification was observed. The samples were collected during a 24 h cycle in four depth layers from the surface down to 300 m depth, using a Nansen opening–closing net with 250-µm mesh size. In winter, the bulk of the copepod population remained in the epipelagic zone (0–100 m) over the entire 24 h cycle, with calanoids remaining the dominant group. An increasing trend of copepod standing stocks from midnight to early morning in the surface layer found in June is in agreement with previous records of copepod day–night variations in the Mediterranean Sea. Day–night differences in diversity and the number of taxa of the epipelagic area were more pronounced in June, confirming the higher intensity of diel vertical migration in summer. Although the epipelagic community was composed of numerous weak diel vertical migrant species, for the majority of investigated copepod taxa, migration patterns differed between the environmentally contrasting seasons. A multivariate non-metric analysis showed that the copepod community was strongly affected by temperature, thus exhibiting a clear seasonal structure.

Resolution changes relationships: Optimizing sampling design using small scale zooplankton data

“…The physical oceanography of the Celtic Sea and Western Approaches, a seasonally stratified area, is well documented (Pingree et al, 1976;Pingree, 1980;Southward et al, 2004;Smyth et al, 2015). Stratification is known to influence plankton abundances (Fransz et al, 1984;Hure et al, 2022) but the absence of vertical data in this study does not allow for discussion of stratification or its influence on copepod abundance.…”

Coastal Eukaryotic Plankton Diversity of the Southern Adriatic as Revealed by Metabarcoding

“…Diversity 2024, 16,293 13 of 20 on morphological identification [28,29]. Most of the copepod genera recorded by metabarcoding are known as common species of the Adriatic, living mainly in coastal and surface waters (Paracalanus, Clausocalanus, Calanus, Calocalanus, Acartia, Centropages, Oithona and Euterpina), but some were characterised as very rare copepods for the Adriatic (Pachos, Neocalanus) in previous studies [25][26][27]. In addition to free-living (pelagic or benthic) copepods, the Southern Adriatic dataset also enabled the identification of some marine invertebrate parasites/symbionts (Pseudanthessius) [78].…”

“…For the Southern Adriatic, previous plankton research in this area also included mainly zooplankton and phytoplankton studies on certain representative groups. Zooplankton studies focused on copepods [25][26][27][28][29], tintinnids [30][31][32] and gelatinous invertebrates [33][34][35][36][37], while phytoplankton studies mainly characterised diatoms [38][39][40]. Moreover, the studies were predominantly based on traditional methods of taxa identification.…”