Seasonal variability of phytoplankton fluorescence in relation to the Straits of Messina (Sicily) tidal upwelling

Abstract

Abstract. In the Straits of Messina, large gradients of tidal displacements, as well as the topographic constrictions, determine the upwelling of deeper waters in the surface layer. This work describes the seasonal variability in the surface distribution of phytoplankton biomass depending on the upwelling phenomena. Temperature, salinity, nitrates and phytoplankton fluorescence were measured in 1994 and 1995 by continuous underway surface real-time measurements onboard dedicated research boats. Each survey was performed following the dynamic phases of flooding and ebbing tides. Tidal currents are essentially southward during high tide and northward during low tide.During the low water slack tide, large spatial gradients of physical-chemical and biological parameters were found, while at the high water slack tide, a diffused phytoplankton fluorescence was observed only in autumn due to a seasonal thermocline. Salinity, nitrate and chlorophyll-a fluorescence data revealed a significant positive intercorrelation, whereas they were inversely correlated with temperature. Generally, the upwelling distribution was limited to narrow zones during winter, while in summer it was found in the middle of the Straits and in the southern zones. During spring in the southern zone of the Straits, the maximum chlorophyll-a fluorescence was detected (May 1995, 0.32 µg-Chla l −1 ); in summer, when back and forth tidal movements between the Tyrrhenian and the Ionian seas intensify, decreased values were observed throughout the study area.The data set obtained through continuous and repeatable samplings has allowed the study of different time-space scales in the Straits of Messina, a very strong and dynamic environment.The Straits system could be compared to an "intermittent pump" which, during the different seasons, initially enriches itself and subsequently provides nutrients to the surrounding basins.

Composition and dynamics of biostimulated indigenous oil-degrading microbial consortia from the Irish, North and Mediterranean Seas: a mesocosm study

“…The Menai Straits is affected by much less hydrocarbon pollution, as shipping activity is generally very low. Average sea surface water temperatures range from winter minimum temperatures of 3–5 °C and summer maximum temperatures of 17 °C for the Helgoland and Bangor sites and between 15 and 27 °C at the Messina site (El Hag & Fogg, ; Wiltshire & Manly, ; Azzaro et al ., ).…”

“…Prior studies of all three sites have shown spring blooms of phytoplankton in April/May for Helgoland and Messina (Gillbrich, ; Azzaro et al ., ) and in May/June for Bangor (Rodrigues & Williams, ). Concentrations of nutrients such as nitrate, phosphate and ammonium are subject to strong annual variations, which are only documented for the Helgoland site (Wiltshire et al ., ).…”

The role of the Strait of Gibraltar in shaping the genetic structure of the Mediterranean Grenadier, Coryphaenoides mediterraneus, between the Atlantic and Mediterranean Sea

“…Furthermore, local strong and periodical upwelling processes, (e.g. [ 18 ]), bring deep-water to surface layers which may also facilitate the transport of egg/larvae between the two Mediterranean basins [ 107 ]. The exchange of only a limited number of migrant across the Strait of Sicily and/or Messina may be enough to prevent genetic differentiation between the Western and Eastern Mediterranean populations.…”

“…The Strait of Sicily is located between the island of Sicily and Tunisia and has approximately 360–430 m depth. The strait of Messina, located between the eastern tip of Sicily Island and mainland Italy, is a very narrow sill shallower than the strait of Sicily (3.1 km wide and approximately 80 m deep at the narrowest part [ 18 ]). Concerning oceanographic processes, the Almeria-Oran front (AOF) found between Spain and Algeria is one of the most studied dynamic systems acting as a barrier to gene flow in the Mediterranean (reviewed by [ 12 ]).…”

How can operational oceanography products contribute to the European Marine Strategy Framework Directive? The Italian case

“…We also cite for completeness that the Strait of Messina (between Sicily and Italy, see Figure 1) is also affected by tide-induced upwelling (Hopkins et al 1984;Bignami & Salusti 1990;Androsov et al 1993) that is not detectable by means of wind records, and that this phenomenon is to be considered just as important as wind-induced upwelling, e.g. in the biological sense (Azzaro & Decembrini 2007).…”