Melek Isinibilir

Biodiversity of the northern Aegean Sea and southern part of the Sea of Marmara, Turkey

Two marine areas (the northern Aegean Sea and southern part of the Sea of Marmara, Turkey) which have different trophic and hydrodynamic characteristics were compared regarding diversities of bacteria, phytoplankton, zooplankton, benthos, fish and cetaceans. During the study period (2006–2007), a total of 27 taxa of aerobic heterotrophic mesophilic bacteria including ten bacterial classes were reported for the first time from both seas. A total of 103 taxa from seven algal classes were determined. Copepod species in the northern Aegean Sea and southern part of the Sea of Marmara were recorded as 44 and 27, respectively. A total of 523 underwater photographs were taken at ten stations and the benthic organism diversity were examined for the first time using the photo-quadrat technique. A total of 72 fish belonging to 36 families, were determined. During the study, a total of 1548 nautical miles of survey effort were conducted for cetacean observation. Living individuals of the Stenella coeruleoalba (striped dolphin) were recorded for the first time. This study is intended to be the first detailed description of the diversity of bacteria, phytoplankton, zooplankton, benthos, fish and cetaceans and comparison of two different marine environments in order to put forth the situation of the ecosystem as it is today.

Decreased levels of the invasive ctenophore Mnemiopsis in the Marmara Sea in 2001

Mnemiopsis leidyi, an endemic ctenophore of the western Atlantic, was first reported in the Marmara Sea in summer 1992, at an average abundance of 27 ind. m−3. We investigated its abundance and distribution together with that of the mesozooplankton (most species are prey organisms of M. leidyi) at eight stations during August 2001, in order to evaluate recent population developments with regard to the impact of its predator, Beroe cf ovata. The abundance of M. leidyi was found to be quite low (range 0.5–8.8 ind. m−3, average 1.62 ind. m−3) compared to 1992. B. cf ovata was, although at very low abundance (0.1–1.1 ind. m−3), only present at stations where M. leidyi occurred. The zooplankton abundance was higher during our investigation than in previous years, which should at least partly be due to a decreased predation impact by M. leidyi.

Population dynamics and morphological variability of Calanus euxinus in the Black and Marmara Seas

Temporal and spatial changes in abundance, prosome length, oil sac volume, molting patterns and morphometric parameters were studied in Calanus euxinus from the Black and Marmara Seas. In the south‐western part of the Black Sea and deep shelf zone near Sinop the abundance of C. euxinus was high during the whole studied period (2000–2005), with a maximum 23,400 ind m−2 in March 2004. In the Marmara Sea near the Prince Islands in the deep zone the mean annual abundance of C. euxinus was 47 times lower than in the deep zone of the Black Sea (during 2000–2007). However, this parameter reached a significant magnitude of 12,264 ind m−2 in spring in Izmit Bay. During the warm season, C. euxinus are rare in the Marmara Sea. The high temperature and salinity accelerate development in this species; therefore, preadults and adults possess reduced prosome length and oil sac volume. In the cold period in the Marmara Sea the size and lipid content in late copepodite stages increase, especially in Izmit Bay. Similar size of eggs, prosome length of early copepodite stages in the Black and Marmara Seas indicate that the C. euxinus population in the Marmara Sea originates from the individuals penetrating from the Black Sea through the Bosphorus.

Competitive advantage of the invasive copepod Oithona davisae over the indigenous copepod Oithona nana in the Marmara Sea and Golden Horn Estuary

Abstract Around 2010, the alien copepod Oithona davisae was introduced to the Marmara Sea and Golden Horn Estuary to live alongside the native species, Oithona nana. By October 2015, the population number, including nauplii, of the introduced species (213,600 ind m−3) was higher than that of the native species (54,900 ind m−3) and close to that of O. davisae in Sevastopol Bay of the Black Sea (342,000 ind m−3) where it appeared 14 years ago. A high percentage of O. davisae females with ovisacs (up to 30% of total female number) carrying up to 15.1 ± 2.1 eggs in the sac and the predominance of nauplii in the population (up to 95% of the total population number) indicate that this alien copepod has become a permanent component of the Marmara Sea and Golden Horn Estuary ecosystem. Our experiments showed that in comparison with widely euryhaline O. davisae, O. nana is a stenohaline species. It has a salinity tolerance in the range of 13–27 psu and, in spite of having a larger body, a lower body density (1.037  ±  0.007 g cm−3) and sinking speed. Carbon-specific respiration rates of both species were close (0.32–0.38 μL O2 μgC−1 day−1) and similar to that of O. davisae from the Black Sea during this period but the frequency and speed of routine jumps, and the maximum escape reaction speed (up to 23.3  ±  1.7 cm s−1) in O. davisae from the Marmara Sea were significantly higher. This indicates the higher adaptive potential of O. davisae in this situation compared to that of O. nana.

New records of jellyfish species in the Marmara Sea

Abstract This manuscript reports the first observations of three species of Hydrozoa (Podocorynoides minima, Koellikerina fasciculata and Gastroblasta raffaelei) and one species of Scyphozoa (Discomedusa lobata) in the Marmara Sea that were sampled in 2006–2011. Their possible introduction pathways, some ecological and distributional details are briefly discussed here.

Interpopulation dynamics between Acartia clausi (Copepoda) and Noctiluca scintillans (Dinoflagellata) in the Bosphorus area of the Black and the Marmara Seas

Abstract The dynamics of abundance and biomass of Noctiluca scintillans (Dinoflagellata) and Acartia clausi (Copepoda) in the Bosphorus area of the Black and Marmara Seas during 2005–2009 has been analyzed. Despite the fact that the more abundant Black Sea zooplankton community permanently enters the Marmara Sea, A. clausi and N. scintillans have formed independent populations in the northeast of the Marmara Sea. This may be confirmed on the one hand by the positive correlations between the numbers of A. clausi and N. scintillans individuals in the Marmara Sea near the Bosphorus Strait and near the Prince Islands and, on the other hand, by a lack of correlation between the abundance of these species in the Marmara Sea and in the Bosphorus area of the Black Sea. The abundance of N. scintillans was 6–10 times lower in the Black Sea near the Bosphorus Strait than that in the Marmara Sea. A high correlation (r = 0.84) between the abundance of N. scintillans and the number of dead A. clausi females near the Bosphorus Strait in the Marmara Sea suggests an important role of necrozooplankton in the development of the dinoflagellate.

First inventory of the shallow-water benthic hydrozoan assemblages of Gökçeada Island (northern Aegean Sea)

Abstract The hydroid fauna of the Mediterranean Sea is considered one of the best known in the world, but the hydrozoans of the Aegean Sea remain poorly studied, hindering efforts to identify alien and invasive species in the region. The spatial and seasonal composition of the shallow-water (0–20 m depth) benthic hydrozoan assemblage from Gökçeada Island was investigated in summer 2012 and winter 2013. Overall, 48 hydrozoan taxa were identified, and their presence and ecological features are discussed herein. Twelve species are recorded for the first time in the Aegean Sea, and the same number for the Turkish coasts. Differences in species composition were detected between the northern and southern coasts of Gökçeada by cluster, multidimensional scaling (MDS) and permutational multivariate analysis of variance (PERMANOVA) analysis, whereas seasonal and vertical distribution patterns were not statistically significant. Differences in species richness and composition between the northern and southern coasts may be explained by the distinct geomorphological aspects of the shores, providing a spatial heterogeneity in the availability of substrates for the hydroid colonies. Observed differences are attributable to the occurrence and/or abundance of common species such as Sertularella ellisii, Aglaophenia tubiformis, Clytia hemisphaerica, Clytia linearis, Eudendrium racemosum, Plumularia obliqua, Eudendrium capillare, Turritopsis dorhnii and Dynamena disticha, rather than to the presence of rare, exclusive species.