Ergün Taşkın

Increasing anthropogenic pressures and nutrient inputs threaten the ecological status of coastal ecosystems along the Aegean coast of Türkiye. This study evaluated coastal water quality and trophic conditions using physicochemical parameters, nutrient concentrations, chlorophyll-a, national eutrophication criteria, the Trophic Index (TRIX), and multivariate statistical analyses across 25 coastal stations monitored during 2022–2023. While basic physicochemical variables showed limited spatial variability, nutrient concentrations, chlorophyll-a, and TRIX values exhibited pronounced spatial differences among stations (p < 0.05), identifying Bostanlı (Inner İzmir Bay) as the principal eutrophication hotspot. Principal Component Analysis (PCA) revealed two dominant environmental gradients: a Nutrient Enrichment Gradient associated with total phosphorus (TP), ammonium, nitrite, and nitrate nitrogen (32.6% of total variance), and a Hydrographic–Thermal Gradient associated with salinity, conductivity, total dissolved solids, temperature, and dissolved oxygen (30.4%). Hierarchical and k-means clustering analyses further distinguished environmentally coherent coastal sectors and confirmed the clear separation of Bostanlı from the remaining sampling stations. The close agreement among nutrient distributions, chlorophyll-a concentrations, TRIX values, and multivariate analyses indicates that localized anthropogenic nutrient enrichment, rather than basin-scale hydrographic variability, drives trophic differentiation along the coast. These findings demonstrate the value of integrated monitoring approaches combining physicochemical, trophic, and multivariate indicators for identifying eutrophication hotspots and supporting ecosystem-based management in Mediterranean coastal ecosystems.

Sensitive benthic macroflora are widely recognized as valuable indicators of ecological quality in coastal ecosystems. This study investigated their diversity and spatial distribution along the Aegean coast of Türkiye and evaluated their relationships with physicochemical variables, nutrient concentrations, and anthropogenic pressures quantified using the Macroalgae-Land Uses Simplified Index (MA-LUSI). A total of 25 coastal stations were surveyed during spring, summer, and autumn 2022, and 91 sensitive taxa were recorded, including 30 brown algae, 52 coralligenous red algae, four green algae, and five seagrasses. Clustered heatmaps based on Bray–Curtis dissimilarity were used to evaluate spatial patterns in community composition using presence–absence and percentage coverage data, whereas Canonical Correspondence Analysis (CCA) was applied to examine the relationships between sensitive phytobenthic communities and environmental variables. The presence–absence heatmap clearly distinguished İzmir-Bostanlı from the remaining stations because of its markedly lower sensitive taxon richness and distinct taxonomic composition. The percentage coverage heatmap also revealed considerable spatial variation among stations, reflecting differences in the abundance and distribution of sensitive habitat-forming taxa. CCA demonstrated clear relationships between sensitive phytobenthic communities and local environmental gradients, with several southern and central Aegean stations being closely associated with sensitive habitat-forming taxa. MA-LUSI values ranged from 0.94 at Gökçeada to 11.25 at İzmir-Bostanlı, indicating pronounced spatial differences in anthropogenic pressure. Overall, the findings demonstrate that sensitive benthic macroflora provide reliable indicators of environmental quality and highlight their importance for the ecological assessment, long-term monitoring, and conservation of coastal ecosystems along the Aegean coast of Türkiye. By identifying areas of ecological degradation, this study also provides a scientific basis for prioritizing conservation and restoration actions in coastal areas exposed to high anthropogenic pressure.

This study assessed the ecological status of the Aegean Sea coasts of Türkiye using the destructive Ecological Evaluation Index continuous (EEI-c) and non-destructive Benthic Ecological Assessment Rapid Index (BEARI) macroalgal indices within the framework of coastal ecological monitoring. A total of 25 coastal stations were investigated and macroalgal taxa were classified into sensitive Ecological Status Group I (ESG I) and Benthic Ecological Group I (BEG I) and tolerant–opportunistic Ecological Status Group II (ESG II) and Benthic Ecological Group II (BEG II), according to their ecological characteristics. Ecological quality status (EQS) was evaluated using EEI-c and BEARI, while Bray–Curtis similarity analysis and Principal Component Analysis (PCA) were applied to examine spatial patterns and relationships with environmental variables. The EEI-c assessment classified 19 stations as “high” and five stations as “good”, whereas only İzmir-Bostanlı exhibited “bad” ecological status. According to BEARI, five stations were classified as “high”, 17 as “good”, and Çandarlı, Güllük, and İzmir-Bostanlı as “moderate”, “poor”, and “bad”, respectively. A significant relationship was detected between EEI-c and BEARI values (R² = 0.71). In addition, Macroalgae-Land Use Simplified Index (MA-LUSI) values were negatively correlated with both EEI-c and BEARI, indicating the sensitivity of macroalgal indices to anthropogenic pressures. Overall, the results demonstrate that macroalgae-based indices provide reliable tools for ecological assessment and support multi-metric approaches in coastal monitoring programs. This study provides one of the first comparative evaluations of destructive (EEI-c) and non-destructive (BEARI) macroalgal indices in relation to MA-LUSI pressure assessment along the Turkish Aegean coasts.

Posidonia oceanica meadows represent one of the most valuable coastal ecosystems in the Mediterranean Sea due to their biodiversity support, sediment stabilization, and long-term carbon sequestration capacity. However, conservation planning often relies on present-day ecological status indicators without incorporating temporal persistence and carbon lock-in potential, which are fundamental to long-term ecosystem resilience. This study introduces the National Posidonia oceanica Priority Index (NPOI), a standardized and operational decision-support model developed for Eastern Mediterranean coastal management. The index integrates four equally weighted components: (A) spatial continuity and area, (Y) temporal persistence derived from lepidochronological age structure, (C) carbon lock-in potential based on matte thickness, and (P) anthropogenic pressure. Anthropogenic pressure is quantified through a six-component weighted model reflecting mechanistic impact pathways. Each component is scored on a 1–5 scale using transparent and repeatable criteria. The index does not assess legal protection eligibility, as all Posidonia oceanica meadows are protected habitats; rather, it quantifies conservation priority and restoration urgency. The methodological framework, scoring protocols, and management interpretation are presented in detail to ensure reproducibility and policy applicability. Application to three Eastern Mediterranean meadows yielded NPOI values ranging from 2.05 to 2.46 (mean ± SD: 2.19 ± 0.23), consistently classifying all sites as restoration-priority systems.

Evaluating the bathymetric distribution of phytobenthic communities is essential for understanding the factors affecting habitat heterogeneity along a depth gradient. In the present study, we investigated the composition and vertical zonation patterns of phytobenthic communities across different bottom types (rocky and sedimentary) along the Turkish Aegean coasts. Dominant habitat types were identified in 175 depths and classified into 18 categories (Posidonia oceanica, Cymodocea nodosa, Halophila stipulacea, Halopteris spp., Stypopodium schimperi, Ericaria crinita, coralligenous, coralligenous/Mesophyllum spp., Jania spp./Halopteris spp., Ulva spp., rocky, rocky-turf, sandy, sandy-Caulerpa taxifolia var. distichophylla, sandy-Gongolaria montagnei var. compressa, silt, muddy, slime). Among the study sites, P. oceanica meadows (41%) were the dominant habitat in 70 depths, followed by sandy (30%), and rocky bottoms (11%). Total coverage of P. oceanica meadows was recorded as 28%, 80%, 76%, and 56% at 5 m, 10 m, 15 m, and 20 m depths, respectively. Seagrass meadows have started to be replaced by sandy bottoms at 30 m (52%) and 40 m (72%). Considering the bathymetrical divergence in phytobenthic community composition and abundance particularly in urban sites, reflected the influence of intense anthropogenic stressors. Here, non-destructive and cost-effective visual sampling technique based on in situ observations of phytobenthic community assemblages, proved to be an effective approach for the assessment of subtidal habitats.

This preprint has been withdrawn at the request of the authors due to significant data inaccuracies that affect the scientific validity of the conclusions.

The study aimed to synthesize Stypopodium schimperi -derived carbon dots (SSCDs) and SSCD-loaded alginate beads (A-SSCDs) via a hydrothermal synthesis method and to investigate their adsorption capacity toward Hg(II), Sn(IV), Zn(II), Cr(VI), and Pb(II). The selective behavior of SSCDs and A-SSCDs against the determined heavy metals was determined using fluorescence quenching and ICP-OES (Inductively Coupled Plasma-Optical Emission Spectrometry) respectively. Characterization of synthesized SSCDs, A-SSCDs and adsorption studies were carried out by field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HR-TEM), Fourier transform infrared (FTIR), UV–Vis spectroscopy, fluorescence spectroscopy and thermogravimetric analysis (TGA). HR-TEM revealed that the carbon dots were spherical with diameters of approximately 10–15 nm. A-SSCD beads exhibited a broad amorphous halo (2θ≈20–30°), typical of disordered carbon structures, which provides a high density of binding sites. Carbon dot incorporation improved the thermal resistance of the alginate beads, indicating stronger structural integrity. Both SSCDs and A-SSCDs demonstrated the highest selectivity toward Cr(VI). A-SSCD beads achieved a maximum experimental adsorption capacity of 132.14 mg g⁻ ¹ at an initial Cr(VI) concentration of 250 mg L⁻ ¹ and a theoretical Langmuir monolayer capacity of 181.82 mg g⁻ ¹ (R ² = 0.986). The use of the invasive brown alga S. schimperi as a carbon source offers a sustainable and cost-effective route for water purification, converting ecologically problematic biomass into a value-added adsorbent. The synthesized carbon dot–alginate composite provides a green, low-cost, and efficient material for Cr(VI) removal from aqueous environments, combining biomass valorization with advanced nanomaterial design. Graphical Abstract

This paper reveals information and describes an updated review on eight non-indigenous marine species (NIS) detected in Fethiye-Göcek SEPA (Muğla, Türkiye). Cheilodipterus novemstriatus is observed with Dia-dema setosum that has been detected in large communities grazing intensively on algal canopies. In some si-tes, Synaptula reciprocans, Pterois miles and Torquigener flavimaculosus, mainly along the South Aegean and Mediterranean coasts, are recorded. Ganonema farinosum and Caulerpa taxifolia var. distichophylla and C. racemosa f. requienii with a significant spread towards the northern Aegean Sea, are documentated. Except for C. taxifolia var. distichophylla, the main vector of these bioinvasions, is the corridor (Suez Canal) and their origin is the Red Sea. Regarded as a main threat to the coastal biodiversity in the Mediterranean, NIS have been one of the main indicators of ecological status in accordance with the EU Marine Strategy Fra-mework Directive, 2017. Therefore, constructing regional datasets from the Turkish coasts, the current work will contribute to the implementations of MSFD, 2017 for the regulatory, conservative and management pur-poses.

Vascular angiosperms considered as architectures of homogeneity, dominate the composition, and ecosystem functioning in the Mediterranean Sea. Since the realisation of the factors influencing the ecological and evolutionary dynamics of seagrasses, is critical for the conservational purposes, we aimed to evaluate the ecological dynamics Posidonia oceanica meadows in Kızılada, Fethiye-Göcek Special Environmental Protected Area (Muğla, Türkiye) in this study. Considering growth dynamics of the plant, lepidochronological analysis using annual cycles of scale thickness, was conducted both on the orthotropic and the plagiotropic rhizomes. The upper limit of P. oceanica meadows, started from a depth of 18.7 m and ended at a depth of 29.7 m in the region. Development of the plagiotropic rhizomes of P. oceanica along a line from the upper limit to the lower limit depth, could be rarely seen in the Turkish coasts. Since the growth rates were different between orthotrophic and plagiotrophic rhizomes, the annual growth of the meadow on the line, was calculated by averaging the both of the rhizomes. Considering the results, the annual growth rate of P. oceanica decreased with depth and was determined to be minimum at the lower limit depth. The average rate of plagiotropic rhizome elongation, was recorded as 17.8 mm yr-1, while the average of orthotrophic rhizomes was recorded as 8.8 mm yr-1. Lepidochronological analyses verified that P. oceanica meadow was estimated to be approximately 2013 years old according to the average annual growth rate of the rhizomes.

Besides playing a crucial ecological role, certain types of algae have also become significant indicators of chemical pollutants. In this research, marine algae were examined to evaluate their suitability as biomonitoring instruments for detecting heavy metal pollution in coastal regions. The levels of cadmium (Cd), nickel (Ni), copper (Cu), lead (Pb), and zinc (Zn) were assessed in two types of green algae: Cladophora fracta and Chaetomorpha ligustica, which were both gathered from the same natural habitat. Samples were collected from the coast of Bostanlı, Izmir (Aegean Sea, Turkey) in August 2023. The collected samples were first subjected to morphological species identification. Inductively Coupled Plasma-Mass Spectro-metry (ICP-MS) analysis was used to measure the accumulated concentrations of heavy metals (Zn Ni, Cu, Pb, Cd) of the separated species. As a result of the analyses, it was determined that the accumulation of heavy metals was higher in Cladophora fracta compared to Chaetomorpha ligustica. Both species have particularly high accumulation potentials for Zn in their tissues. The heavy metal accumulation concentrations for both species are as follows, respectively: Zn > Ni > Cu > Pb > Cd.