The presence of the Indo-Pacific symbiont-bearing foraminifer Amphistegina lobifera in Greek coastal ecosystems (Aegean Sea, Eastern Mediterranean)

During the last decades, hundreds of species of Indo-Pacific origin from the Red Sea have traversed the Suez Canal and settled in the Eastern Mediterranean. Nowadays, Amphistegina lobifera Larsen, is known to be a successful immigrant that is widely distributed in the coastal ecosystems of the Eastern Mediterranean Sea. Amphistegina is the most common epiphytic, symbiont- bearing large foraminifer. In this study we provide additional data on the presence of this species in the coastal ecosystems of Aegean Sea, Greece. The high relative abundance of A. lobifera is the result of very successful adaptation of this species to local conditions and suggests that it has become a significant part of the epiphytic foraminiferal fauna

Alien foraminifers from Greek coastal areas (Aegean Sea, Eastern Mediterranean)

The present study provides additional data on the distributional range of six alien foraminiferal species in living assemblages from Greek coastal areas (Aegean Sea, Eastern Mediterranean). Amphistegina lobiferaLARSEN 1976, Sorites orbiculus (FORSK L 1775) and Coscinospira hemprichii EHRENBERG 1839 are well established in Greek coastal areas, whereas Triloculina fichteliana D'ORBIGNY 1839, Planogypsina acervalis (BRADY 1884) and Cymbaloporetta plana (CUSHMAN 1924), are recorded for the first time in this paper. The occurrence of these species in a number of sites in the Aegean Sea establishes their presence in the Eastern Mediterranean

Hazardous explosive eruptions of a recharging multi-cyclic island arc caldera

Caldera-forming eruptions of silicic volcanic systems are among the most devastating events on Earth. By contrast, post-collapse volcanic activity initiating new caldera cycles is generally considered less hazardous. Formed after Santorini’s latest caldera-forming eruption of ~1600 bce, the Kameni Volcano in the southern Aegean Sea enables the eruptive evolution of a recharging multi-cyclic caldera to be reconstructed. Santorini’s eruptive record has been documented by onshore products and historical descriptions of mainly effusive eruptions dating back to 197 bce. Here we combine high-resolution seismic reflection data with cored lithologies from International Ocean Discovery Program Expedition 398 at four sites to determine the submarine architecture and volcanic history of intra-caldera deposits from Kameni. Our shore-crossing analysis reveals the deposits of a submarine explosive eruption that produced up to 3.1 km3 of pumice and ash, which we relate to a historical eruption in 726 ce. The estimated volcanic explosivity index of magnitude 5 exceeds previously considered worst-case eruptive scenarios for Santorini. Our finding that the Santorini caldera is capable of producing large explosive eruptions at an early stage in the caldera cycle implies an elevated hazard potential for the eastern Mediterranean region, and potentially for other recharging silicic calderas

Alien foraminifers from Greek coastal areas (Aegean Sea, Eastern Mediterranean)

The present study provides additional data on the distributional range of six alien foraminiferal species in living assemblages from Greek coastal areas (Aegean Sea, Eastern Mediterranean). Amphistegina lobifera LARSEN 1976, Sorites orbiculus (FORSKÅL 1775) and Coscinospira hemprichii EHRENBERG 1839 are well established in Greek coastal areas, whereas Triloculina fichteliana D'ORBIGNY 1839, Planogypsina acervalis (BRADY 1884) and Cymbaloporetta plana (CUSHMAN 1924), are recorded for the first time in this paper. The occurrence of these species in a number of sites in the Aegean Sea establishes their presence in the Eastern Mediterranean

Live and dead benthic foraminiferal assemblages from coastal environments of the Aegean Sea (Greece): Distribution and diversity

Benthic foraminiferal composition assemblages and their temporal changes, ecological indices and foraminiferal densities are used to compare three coastal environments with different physicogeographical features in the Aegean Sea (coastal environment of Avdira-Vistonikos Gulf and Kitros-Thermaikos Gulf and open lagoonal environment of Vravron-South Evoikos Gulf). Three main foraminiferal assemblages have been recognized: a) "Assemblage A" high degree of similarity between living and dead foraminiferal species, dominated by Ammonia beccarii, Elphidium spp. and relatively abundant and diverse miliolids, b) "Assemblage B1" intermediate degree of similarity between live and dead assemblages, characterized by highly-abundant and well-diversified foraminiferal assemblages including the algal symbiont bearing Peneroplis pertusus together with Ammonia tepida and several small epiphytic rotaliids and miliolids, and c) "Assemblage B2" absence of living individuals, strongly dominated by the opportunistic species A. tepida. Our results suggest a good comparison between living and dead assemblages from different coastal environments in the Aegean Sea, however the prevailing environmental conditions (vegetation cover, hydrodynamics, fresh water influx) have a strong impact on the taphonomic processes. © 2015 Published by Elsevier Masson SAS

Observations on the life cycle of the symbiont-bearing foraminifer Amphistegina lobifera Larsen, an invasive species in coastal ecosystems of the aegean sea (Greece, E. Mediterranean)

Members of the family Amphisteginidae have been nearly ubiquitous contributors to shelf carbonate facies through most of the Cenozoic. The most prolific carbonate producer of modern representatives is Amphistegina lobifera Larsen, which is the largest and shallowest dwelling of the IndoPacific taxa. This epiphytic, symbiont-bearing foraminifer is also a remarkably successful invasive species in coastal ecosystems of the eastern Mediterranean, where its shell production is altering the composition of shoreline sediment. This paper reports a temporal study of an A. lobifera population collected monthly between June 2008-May 2009 in the Vravron/Attica coastal ecosystem of the south Evoikos Gulf (Aegean Sea), where winter temperatures can drop below previously reported minima for the species. Monthly variations in size, frequency distribution, and abundance indicate that this population reproduced primarily during the summer (July-September), when both asexual and sexual reproduction occurred simultaneously, suggesting a predominantly coeval, one-year life span for each generation. However, a modest increase in juveniles in January indicates some winter reproduction. Comparison of these findings with previous studies shows that a) tolerance of low winter temperatures, b) adaptation of the life cycle to strong seasonality, and c) the mixotrophic feeding strategy have allowed A. lobifera to proliferate in the exceptionally clear, low nutrient, coastal waters of the Mediterranean Sea. These attributes elucidate how previous Cenozoic populations of Amphistegina were able to rapidly expand their latitudinal ranges and invade shallow epeiric seas during episodes of climatic warming

Living benthic foraminifera as an environmental proxy in coastal ecosystems: A case study from the Aegean Sea (Greece, NE Mediterranean)

The species composition of the epiphytic benthic foraminiferal fauna was compared at two coastal locations in the Aegean Sea. Samples were collected during August 2001 and July 2003 along the southeastern coast of Andros Island at Korthi Gulf, where there are minimal anthropogenic activities, and at Kastro Gulf, with substantial anthropogenic influence. This study represents the first application of the FORAM Index (FI), which is a single-metric index for water quality originally developed for western Atlantic reef foraminiferal assemblages, to Mediterranean assemblages. Multivariate analyses distinguished three clusters of sample sites representing three foraminiferal assemblages. Samples dominated by the mixotrophic species, A. lobifera, were collected primarily from sites along the northern coasts of both gulfs. Characteristics of this assemblage, including relatively high dominance (D. = 0.27-0.51), lower Shannon-Wiener diversity (H'. = 1.3-2.1) and high FI (6.6-8.2), all reflect oligotrophic environmental conditions typical of pristine waters of the Aegean Sea. A. lobifera was typically the most common species in the second assemblage, though relative abundances of heterotrophic taxa were higher, resulting in somewhat higher diversity (H'. = 1.6-2.4) and lower dominance (D. = 0.14-0.36). These indices, as well as the FI range of 3.5-7.0 indicated somewhat more prevalent organic carbon resources but still relatively high water quality. This assemblage was found along the southern coast of Korthi Gulf and at more interior sites in northern Kastro Gulf. The third assemblage was dominated by smaller heterotrophic species, including notable proportions of the stress-tolerant taxa Ammonia spp. and Elphidium spp., and had few or no A. lobifera. Diversity (H'. = 1.4-2.0) and dominance (D. = 0.22-0.47) indices were similar to those for the first assemblage, but FI values were much lower (2.0-3.4). Samples characterized by this assemblage were collected only from the southern Kastro Gulf, in the vicinity of the primary sewage outfall. The results of this study document the sensitivity of benthic foraminiferal assemblages, and particularly A. lobifera populations, to sewage pollution in the Aegean Sea. These observations are consistent with studies from other biogeographic regions where the FORAM Index, which is based upon this genus and associated mixotrophic taxa, has been used as a water-quality indicator. This observation is particularly noteworthy because A. lobifera is an invasive species in the Mediterranean. © 2011 Elsevier B.V

Foraminiferal and ostracod ecological patterns in coastal environments of SE Andros Island (Middle Aegean Sea, Greece)

A comparative study of recent epiphytal ostracod and benthic foraminiferal populations was conducted in August 2001, at two gulfs (Korthi and Kastro) located at the southeastern part of Andros Island (middle Aegean Sea, Greece). Thirty samples (representing living macro-benthic algae and seagrasses) from both gulfs were studied and a total of 34 ostracod species and 60 benthic foraminiferal species were identified. In the gulf of Korthi both benthic foraminiferal and epiphytal ostracod assemblages were characterized by high abundances of Amphistegina lessonii and Xestoleberis spp., respectively, therefore the performed Q-mode cluster analysis verified the presence of a Normal Environment Biofacies (NE). Declined Environment (DE) and Stressed (SE) Environment Biofacies were recognized in the gulf of Kastro, an area more affected by anthropogenic activities. Several deformed foraminiferal specimens have been documented in the assemblages from both gulfs, but malformed tests are significantly increased in SE Biofacies of Kastro gulf. This study suggests that great accumulations of A. lessonii (35-60%) associated with high frequencies of Xestoleberis communis and/or Xestoleberis decipiens and high species diversities can be used as bioindicators of coastal health. © 2005 Elsevier SAS. All rights reserved