Copepod Community Structure in Pre- and Post- Winter Conditions in the Southern Adriatic Sea (NE Mediterranean)

Marijana Hure,Vedrana Kovačević,Rade Garić,Manuel Bensi,Mirna Batistić

doi:10.3390/jmse8080567

Abstract

Copepod communities were studied along an east-west transect in the oligotrophic Southern Adriatic Sea. This dynamic region is under the influence of various physical forces, including winter vertical convection, lateral exchanges between coastal and open sea waters, and ingression of water masses of different properties all of which occurred during the investigation periods. Depth-stratified samples were taken with a Nansen net (250 µm mesh size) in pre- and post-winter conditions in 2015/2016. In December, the coastal copepod community was limited over the western flank, while epipelagic waters of the open and eastern waters were characterized by high diversity, low abundances in the central area, and subsurface/upper mesopelagic copepod species. In April, higher abundances were recorded over the entire vertical profile with the surface coastal copepod community present through the entire transect. Higher abundances in the central area during the post-winter period are probably a consequence of late-winter/early spring blooms near the center of the Southern Adriatic. Mesopelagic fauna of both months was characterized by high abundances of Haloptilus longicornis, characteristic species of the eastern Mediterranean, whose larger presence was favored by the cyclonic phase of the North Ionian Gyre and a consequent strong Levantine Intermediate Water ingression.

Highlights

The Adriatic Sea is an elongated and relatively shallow basin, stretching south-eastward for 800 km from the highest Mediterranean latitude (45◦47 N) in the Eastern Mediterranean basin.The current regime of the whole Adriatic Sea is characterized by a basin wide cyclonic surface flow: On the eastern flank, the so called Eastern Adriatic Current (EAC) flows northward and brings warm and salty waters to the northernmost part of the Adriatic
In December, the coastal copepod community was limited over the western flank, while epipelagic waters of the open and eastern waters were characterized by high diversity, low abundances in the central area, and subsurface/upper mesopelagic copepod species
During investigated periods (December 2015, April 2016) physical forces such as winter vertical convection, lateral exchanges between coastal and open sea waters, and ingression of Levantine Intermediate Water (LIW) were able to regulate the spatial distribution of copepods in the SA

Summary

Introduction

The Adriatic Sea is an elongated and relatively shallow basin, stretching south-eastward for 800 km from the highest Mediterranean latitude (45◦47 N) in the Eastern Mediterranean basin.The current regime of the whole Adriatic Sea is characterized by a basin wide cyclonic surface flow: On the eastern flank, the so called Eastern Adriatic Current (EAC) flows northward and brings warm and salty waters to the northernmost part of the Adriatic. Instead, the Western Adriatic Current (WAC) flows south-eastward geostrophycally balanced along the Italian coast, transporting relatively cold and fresh water out of the Adriatic Sea [1,2,3,4,5], through the Strait of Otranto (~90 km wide and ~800 m deep), which is the communication channel between the Adriatic and the Ionian seas. The Southern Adriatic (SA, Figure 1) sub-basin represents the deepest part of the Adriatic, with a maximum depth of ~1200 m. It is characterized by the presence of a quasi-permanent cyclonic South Adriatic Gyre [3,8,9]. This process is able to regulate the salt and nutrients content of the entire basin [10]

Objectives

Methods

Results

Discussion

Conclusion