A MSFD complementary approach for the assessment of pressures, knowledge and data gaps in Southern European Seas : the PERSEUS experience

PERSEUS project aims to identify the most relevant pressures exerted on the ecosystems of the Southern European Seas (SES), highlighting knowledge and data gaps that endanger the achievement of SES Good Environmental Status (GES) as mandated by the Marine Strategy Framework Directive (MSFD). A complementary approach has been adopted, by a meta-analysis of existing literature on pressure/impact/knowledge gaps summarized in tables related to the MSFD descriptors, discriminating open waters from coastal areas. A comparative assessment of the Initial Assessments (IAs) for five SES countries has been also independently performed. The comparison between meta-analysis results and IAs shows similarities for coastal areas only. Major knowledge gaps have been detected for the biodiversity, marine food web, marine litter and underwater noise descriptors. The meta-analysis also allowed the identification of additional research themes targeting research topics that are requested to the achievement of GES. 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license.peer-reviewe

Reproductive biology of Trachurus mediterraneus (Carangidae): a detailed study for the Marmara - Black Sea stock

The reproductive biology of Mediterranean horse mackerel Trachurus mediterraneus was investigated in the Sea of Marmara over a one-year period. Duration and timing of the spawning season, gonad histology, oocyte development and size at sexual maturity were determined. The presence of all stages of oocytes without any distinct size hiatus indicated that oocyte development of Mediterranean horse mackerel is asynchronous with indeterminate fecundity. Spawning starts in May, peaks in July-August and ends in September. Sizes at 50% maturity were found to be 12.2 and 12.5 cm (total length) for females and males, respectively. Mean batch fecundity was calculated as 10136 +/- 703 eggs. Our results on the size at sexual maturity and batch fecundity for the Sea of Marmara differed significantly from published results from the Mediterranean Sea. We ascribe these differences to different stock structures in these seas. Our results form the basis for future reproductive biology studies on the under-studied Marmara-Black Sea stock

Spawning Frequency of Trachurus mediterraneus (Carangidae) in The Sea of Marmara

In this study the spawning frequency of Trachurus mediterraneus was estimated for the first time in the Mediterranean basin. The presence of the late-migratory nucleus stage oocytes and post ovulatory follicles (POFs) in the same ovaries were observed continuously during the sampling period. The daily percentage of spawning females with ovaries containing: late migratory nucleus (MN) stage, POFs (present up to 12-24h from the spawning event) was calculated as 11.7% and 18.6% respectively. The average percentage of females presenting one of the two different states was 15.3% which indicated that Mediterranean horse mackerel had high spawning rates in the Sea of Marmara. Our results indicated that T. mediterraneus is a multiple spawner and females spawn approximately every 6.6 days, therefore 20 times in the spawning period May-August 2009

Seasonal distribution of Trachurus mediterraneus (Steindachner, 1868) in the Golden Horn Estuary, Istanbul

Seasonal changes in the distribution of an important commercial and recreational fish species, Trachurus mediterraneus (Steindachner, 1868), from the family Carangidae were investigated in the Golden Horn Estuary of Istanbul. Environmental conditions were also considered to evaluate distributional patterns in the region. Sampled fish size ranged between 7.5 and 20.1 cm in total length and 3.4 and 86.2 g in total weight during the sampling period. Adult individuals (> 12.5 cm) preferred not to be in the estuary during the summer period, while only immature adults were found with a 7.5-12.5 cm total length size range from May to August 2009. It was observed that on a regional basis this species was only found at the entrance of the Golden Horn. Environmental parameters such as surface temperature, salinity, and dissolved oxygen values did not display significant correlations with its distribution throughout the study period. However, chlorophyll a and Secchi disk values displayed significant negative correlations with the distribution of immature adults in the Golden Horn

Ichthyoplankton community of the Dardanelles Strait, Turkey

An ichthyoplankton survey was conducted between March 2012 and February 2013 along the Anatolian coast of the Dardanelles Strait, with the aim of describing the species composition and temporal variation of fish eggs and larvae. For this purpose, monthly samples were collected at three sites using a WP-2 plankton net equipped with 500 mu m mesh during a one-year period. Biodiversity indices were calculated to understand differences in biodiversity. A total of 50 teleost fish species belonging to 25 families and 7 orders were identified. The highest species richness of fish eggs was recorded in spring, whereas the highest species richness of fish larvae in spring and summer. On the other hand, species richness of fish eggs and larvae were at a minimum in the fall. The most dominant species recorded in the Dardanelles were Sprattus sprattus as fish eggs and Engraulis encrasicolus as fish larvae. The relatively lower abundance of eggs and lack of earlier egg phases indicate that Engraulis encrasicolus does not spawn in the Dardanelles Strait, and the spawned eggs develop while drifting from the spawning grounds in the Marmara Sea to the sampling area

Conjoined Twinning Incidences in Trachurus mediterraneus (Steindachner, 1868) Eggs in Southern Marmara Sea

Conjoined twinning is a rarely existed gross malformation in natural conditions. The term refers to the two individuals united at any part of their bodies. The extraordinary incidences of conjoined twinning cases may reflect important problems on the marine environment. Therefore, the purposes of this study were to report the incidences of Trachurus mediterraneus conjoined twins in Bandirma Bay, Southern Marmara Sea and to discuss the possible causes of them to derive new research questions. Four polyembryonic individuals were collected from three stations of Bandirma Bay Ichthyoplankton Survey in June 2012. The anomalous individuals were observed at the stations, St-9, 10 and 13 (Critical Stations). St-9 was at about 20m depth contour between Karsiyaka town and Dalyan village in western coasts of bay. St-10 and 13 was off Yenice village at about 10 and 30m depth contours respectively in the eastern coasts of the bay. The surface temperature, salinity, dissolved oxygen and pH of critical stations were seemed to be normal. Therefore the pollution was considered as the most possible reason of these incidences

Evidences for influence of a heterotrophic dinoflagellate (Noctiluca scintillans) on zooplankton community structure in a highly stratified basin

Variations in mesozooplankton diversity, community structure, and species assemblage related to environmental variability have been discussed regarding the Sea of Marmara, with particular attention to regulation by the holozoic dinoflagellate Noctiluca scintillans. Temperature stands alone as the most important factor affecting species succession and community structure while Noctiluca significantly influences zooplankton abundance and diversity, and appears as the prevailing factor for non-temperature dependent patterns in the zooplankton community. Competition between Marmara zooplankton and Noctiluca for the same food resources could be an important factor, considering the high production of the species when compared to herbivorous and omnivorous zooplankters. Meanwhile, chlorophyll a recorded throughout the study period indicated a sufficient food supply that could promote continuous mesozooplankton production in the region. Therefore top-down regulation of the zooplankton community by Noctiluca may gain importance. Noctiluca differed from other r-strategists mainly by its high competitive ability, year round occurrence, and large cell size. Therefore, zooplankton could not compete with Noctiluca in the long-term and Noctiluca found an opportunity to increase its abundance before the settlement of distinct summer or winter communities. Enhanced abundance, year-round occurrence, and high condition of Noctiluca population indicated that optimum conditions had been achieved for explosive development of the species in the Sea of Marmara. Increasing dominance of Noctiluca in the Sea of Marmara points out that the species could have a stronger affect on zooplankton in the following years and interrupt trophic pathways by reducing fodder zooplankton biomass. (c) 2005 Published by Elsevier Ltd

Conjoined Twinning Incidences in Trachurus mediterraneus (Steindachner, 1868) Eggs in Southern Marmara Sea

Conjoined twinning is a rarely existed gross malformation in natural conditions. The term refers to the two individuals united at any part of their bodies. The extraordinary incidences of conjoined twinning cases may reflect important problems on the marine environment. Therefore, the purposes of this study were to report the incidences of Trachurus mediterraneus conjoined twins in Bandirma Bay, Southern Marmara Sea and to discuss the possible causes of them to derive new research questions. Four polyembryonic individuals were collected from three stations of Bandirma Bay Ichthyoplankton Survey in June 2012. The anomalous individuals were observed at the stations, St-9, 10 and 13 (Critical Stations). St-9 was at about 20m depth contour between Karsiyaka town and Dalyan village in western coasts of bay. St-10 and 13 was off Yenice village at about 10 and 30m depth contours respectively in the eastern coasts of the bay. The surface temperature, salinity, dissolved oxygen and pH of critical stations were seemed to be normal. Therefore the pollution was considered as the most possible reason of these incidences

Benthic community structure of the Bosphorus and surrounding area

Spatial and temporal distribution of benthic communities around the Strait of Istanbul (Bosphorus) and the effect of lower layer discharge on these communities have been evaluated during studies between February-December 1999. Mytilus galloprovincialis was the dominant species with fasies at the Black Sea station that is not affected by the strait lower layer current system. On the other hand, another Black Sea station, influenced by the strait lower layer currents, has a similar biota to the strait stations. Species richness and diversity is highest in the strait than other areas. The dominant species is Maera grossimana. However, the station located at the Black Sea exit of the strait has a different biota, and various groups/species appeared to be dominant. Melinna palmata is the dominant species at the Sea of Marmara during the study period. Low dissolved oxygen values of lower layer and soft substratum of sediment resulted in wide distribution of Melinna palmata, adapted to these conditions. The closer stations to the strait in the Sea of Marmara have higher diversity as a result of hydrodynamic processes. On the other hand, coastal stations with low currents and inputs have lower index values, showing the negative effect of discharges and pollution