Optical closure in marine waters from in situ inherent optical property measurements.

Optical closure using radiative transfer simulations can be used to determine the consistency of in situ measurements of inherent optical properties (IOPs) and radiometry. Three scattering corrections are applied to in situ absorption and attenuation profile data for a range of coastal and oceanic waters, but are found to have only very limited impact on subsequent closure attempts for these stations. Best-fit regressions on log-transformed measured and modelled downwards irradiance, Ed, and upwards radiance, Lu, profiles have median slopes between 0.92 - 1.24, revealing a tendency to underestimate Ed and Lu with depth. This is only partly explained by non-inclusion of fluorescence emission from CDOM and chlorophyll in the simulations. There are several stations where multiple volume scattering function related data processing steps perform poorly which suggests the potential existence of unresolved features in the modelling of the angular distribution of scattered photons. General optical closure therefore remains problematic, even though there are many cases in the data set where the match between measured and modelled radiometric data is within 25% RMS%E. These results are significant for applications that rely on optical closure e.g. assimilating ocean colour data into coupled physical-ecosystem models.

Microplastic pollution levels in the surface water and sediment of Orontes basin: Urgent risk for endangered species.

Freshwater environments are a significant source of microplastics in the oceans, but, little is known about the distribution of microplastics in rivers and lakes. This study was undertaken to investigate the abundance and composition of microplastics (MPs) in the surface water and sediment of Karasu Creek, Gölbasi Lake and Orontes River which are critical habitats for many endangered species. The mean microplastic abundance in the surface water and sediment of the Orontes Basin was determined to be 3.2 ± 4.0 MPs/L and 456 ± 318 MPs/kg, respectively. Due to the similar socioeconomic status and anthropogenic activities in the vicinity of stations, there wasn't any temporal variation in the microplastic abundance depending on stations. However, microplastic abundance in the surface water was drastically increased during flood periods. A correlation between microplastic abundance in the surface water and sediment was not detected due to insufficient data representing the hydrodynamic properties of the study area. Morphologically, fiber MPs were dominant (89 %), followed by fragments (9 %). The majority of the extracted MPs were <1 mm. This led to an increase in the number of individuals and species likely to be negatively affected by MPs. In terms of color, majority of the MPs were black (44 %) followed by blue (21 %), red (18 %), transparent and white (9 %). Results obtained in this study proved the ubiquity and dominance of the microplastics in both surface water and sediment. Therefore, the findings clearly show a remarkable ecological risk and indicate the need for mitigation strategies in the Orontes Basin ecosystem. This study provided critical data for local and national authorities to take necessary precautions to manage microplastic pollution in the Orontes Basin. However, more comprehensive understanding of the long-term impacts of pollution from MPs on endemic species is crucial for effective conservation strategies.