Patrones espacio-temporales de clorofila en el Mediterráneo Noroccidental derivados del sensor MERIS

Abstract

SUMMARY: We address the major surface signatures of chlorophyll a in the Catalan Sea within the context of the dynamics of the north-western Mediterranean basin. Monthly composites from MERIS measurements and CHL products for Case 1 waters were analysed from June 2002 to June 2005. Composite images of variability were used to identify surface dynamics. The results showed that coastal and open sea waters were separated by a belt of low variability, a permanent oligotrophic belt that is noticeable with respect to the bloom conditions of the surrounding areas. The width of this Catalan Oligotrophic Belt (COB) located along the continental slope, varied between 17 and 30 km and became blurred in the southernmost area. The chlorophyll a temporal pattern over the shelf showed an almost steady increase from September to March. A similar behaviour but with lower concentrations was observed in oceanic waters. Both temporal patterns showed a disruption during January and/or February that coincided with the well known deep water formation event in the Gulf of Lions. In 2004, the convection was weaker and the offshore temporal trend was not disrupted; however, the opposite was observed in 2005. The spatial chlorophyll a distribution of oceanic waters presented a clear north-south decreasing trend, while the coastal distribution did not show any latitudinal patterns but rather peaks in the areas enriched by river runoff. The observed seasonality was similar to the one published from SeaWiFS data and slightly different from the seasonality shown by CZCS data. Nevertheless, we did not discard the possibility that some of the observed seasonal differences could be a true temporal shift in chlorophyll a production.Keywords: north-western Mediterranean, chlorophyll a, remote sensing, MERIS.RESUMEN: Patrones espacio-temporales de clorofila en el Mediterráneo Noroccidental derivados del sensor MERIS. -En este estudio se examinan los principales patrones en la distribución superficial de la clorofila a en el marco explicativo de la dinámica del Mediterráneo Noroccidental. Para identificar la dinámica en superficie se compusieron imágenes de variabilidad. Los resultados mostraron que entre las aguas costeras y oceánicas se diferenciaba un cinturón de baja variabilidad, permanentemente oligotrófico y visible cuando en las aguas circundantes se producía proliferación algal. La amplitud del Cinturón Oligotrófico del mar Catalán (COB), localizado a lo largo del talud continental, oscilaba entre 17 y 30 km, disipándose en la mitad sur. El patrón temporal de clorofila en la zona de plataforma mostró un claro aumento de septiembre a marzo. Un patrón similar se observó en la concentración superficial en aguas oceánicas. En ambas regiones se observó una interrupción del patrón temporal en enero y/o febrero, coincidiendo con el momento de formación de agua profunda del Golfo de León. En el 2004 el fenómeno de formación de agua profunda fue más débil y el patrón mensual en la región oceánica no sufrió ninguna interrupción, al contrario que en e...

Ecological information and water mass properties in the Mediterranean recorded by stable isotope ratios inPinna nobilisshells

“…In fact, calcification temperatures of specimen B16 show abnormally cold temperatures for that summer, which may indicate some growth disturbance after such a hot event or the event was too brief at 16 m to be captured by our monthly to submonthy sampling resolution. Specimen A16, however, shows a positive spike in the d 18 O SHELL values of winter [2004][2005] (Figure 7), which is coincident with the extremely dry and cold winter described by Font et al [2007] and Gordoa et al [2008]. Our measured temperatures for that winter do not show the presence of significantly colder waters than in previous winters at 16 m ( Figure 4 and Table 1).…”

“…The atypical dense waters penetrated down to 750 m in an uninterrupted cascading process lasting from late January to late March [Canals et al, 2006;Font et al, 2007]. This episode was reflected in the anomalously low values of chlorophyll a recorded for that winter, related to the increased vertical convection in the Catalan Basin and the reduced runoff of Ebro River [Gordoa et al, 2008].…”

Trophic Interactions of European Hake Merluccius merluccius (Linnaeus, 1758) in Benthic Communities off the Moroccan Mediterranean Coastline: Seasonal and Ontogenetic Shifts

“…In the Mediterranean Sea, the juvenile hake diet was investigated using stomach content analysis [14,15], while the feeding behavior of adult fshes was studied using carbon-nitrogen stable isotopes, stomach content analysis, and metabarcoding approach [16][17][18][19]. As reported by several authors [9,10,14,[20][21][22][23], M. merluccius feeds on a broad spectrum of prey including zooplankton, crustaceans, fsh, and cephalopods, shifting its feeding habits geographically from one prey to another according to prey abundance and availability in the environment, described as an opportunistic feeder. Anchovies (E. encrasicolus) and sardines (S. pilchardus) are reported to be the main important prey both in the north-western Mediterranean [15], Adriatic Sea [24], and Tyrrhenian Sea [17], with high variability in the abundance of these small pelagic fsh across subregions [10,23].…”

“…In fact, from an ecological point of view, M. merluccius occupies a high level in the marine trophic web with a fundamental role as a relevant top predator in the trophic ecology of mesopelagic communities, maintaining the equilibrium and sustainability of the ecosystem and regulating the abundance and diversity of other species within their food web through consistent predation, ensuring a favorable impact on biodiversity and helping to preserve its natural state [8][9][10]. Terefore, to support the sustainability of this resource, management strategies must rely on accurate information regarding ecological and biological aspects based on objective data obtained through scientifc studies of the populations subject to exploitation.…”

“…Te sample was analyzed according to fsh sizes and seasons, and qualitative/ quantitative feeding indices were calculated. Te trophic spectrum of Merluccius merluccius included 24 prey items in total, mainly belonging to Osteichthyes (12), Crustacea (10), Cephalopoda (1), and Polychaeta (1), suggesting a generalist behavior of this predator as in numerous regions of the Mediterranean Sea, with several species that occasionally occurs in its diet. In the Moroccan Mediterranean Sea, Osteichthyes proved to be the most important prey item (%IRI = 78.56) among the diferent zoological groups, followed by Crustacea (% IRI = 16.22).…”