Environmental variations in a semi-enclosed embayment (Amvrakikos Gulf, Greece) – reconstructions based on benthic foraminifera abundance and lipid biomarker pattern

Abstract

The evolution of environmental changes during the last decades and the impact on the living biomass in the western part of Amvrakikos Gulf was investigated using abundances and species distributions of benthic foraminifera and lipid biomarker concentrations. These proxies indicated that the gulf has markedly changed due to eutrophication. Eutrophication has led to a higher productivity, a higher bacterial biomass, shifts towards opportunistic and tolerant benthic foraminifera species (e.g. <i>Bulimina elongata</i>, <i>Nonionella turgida</i>, <i>Textularia agglutinans</i>, <i>Ammonia tepida</i>) and a lower benthic species density. Close to the Preveza Strait (connection between the gulf and the Ionian Sea), the benthic assemblages were more diversified under more oxygenated conditions. Sea grass meadows largely contributed to the organic matter at this sampling site. The occurrence of isorenieratane, chlorobactane and lycopane supported by oxygen monitoring data indicated that anoxic (and partly euxinic) conditions prevailed seasonally throughout the western part of the gulf with more severe oxygen depletion towards the east. Increased surface water temperatures have led to a higher stratification, which reduced oxygen resupply to bottom waters. Altogether, these developments led to mass mortality events and ecosystem decline in Amvrakikos Gulf

Assessing the distribution of sedimentary C40 carotenoids through time

“…Planktonic okenone and chlorobactene in marine systems have only been documented in small, semienclosed fjords and gulfs (Fig. A; Smittenberg et al ., ; Naeher et al ., ). These restricted coastal environments are not directly comparable to the ancient systems that paleoenvironmental studies strive to reconstruct.…”

Anthropogenically induced environmental changes in the northeastern Adriatic Sea in the last 500 years (Panzano Bay, Gulf of Trieste)

“…The impact here started nearly 500 years ago with the onset of mercury mining in the hinterland of the bay (Singh and Turner 2009;Covelli et al, 2012), enhanced in the 20th century with intensifying agriculture and mariculture (Aleffi et al, 2006;Rampazzo et al, 2013;Finch et al, 2014), and has continued until present times with increasing port and industrial activities (thermoelectric plant) of the city of Monfalcone (Notar et al, 2001;Pozo et al, 2009).…”

Sympatric occurrence of two Azadinium poporum ribotypes in the Eastern Mediterranean Sea

“…The Amvrakikos Gulf is a large (405 km 2 ), semi-enclosed embayment, located in Western Greece. It is connected to the open Ionian Sea through a narrow, elongated channel, the Preveza Straits, which is approximately 6 km long, 0.8 to 2.5 km wide and 20 m deep (Naeher et al, 2012). The mean depth of the gulf is 26 m, while the maximum depth of 63 m has been recorded in its eastern part (Kehayias and Aposporis, 2014).…”