NOPR Collection:

Modeling of accumulation areas of cohesive sediments entering the southeastern Black Sea from Degirmendere River

Thu, 01 Feb 2024 00:00:00 GMT

Title: Modeling of accumulation areas of cohesive sediments entering the southeastern Black Sea from Degirmendere River Authors: Yazir, Devran Abstract: Modeling transport, accumulation, and deposition areas of sediments are essential for assessing risks to coastal areas and the environment. In this study, the advection-dispersion and accumulation areas of cohesive sediments entering the Black Sea from Degirmendere Basin, the largest river basin on the Southeastern Black Sea coast, were modeled using the POMSED module, which is a submodule of The Princeton Ocean Model (POM). The fate of cohesive sediments in the marine environment has been predicted by different parameters, such as the change in the amount of cohesive sediment entering the Southeastern Black Sea, the dominant surface circulation, the effect of the wind pattern, and the anticyclonic cycle. In the high-flow seasons, the sediment drift velocity is also high. For large sediment drift velocity, cohesive sediments accumulate heavily in coastal areas east of the study area. It has been determined that high sediment drift velocity is the most influential parameter in determining the accumulation areas of cohesive sediments. In the low-flow seasons, the sediment drift velocity is also small. For small sediment drift velocity, cohesive sediments accumulate at the river's mouth under the influence of the predominant wind. This study will constitute the basis for coastal interventions to be carried out in the Southeastern Black Sea, port cleaning study plans, and risk assessment studies for areas where fishermen's shelters are located. Page(s): 53-64

Molecular phylogeny reconstruction and biogeographic pattern of Rays (Elasmobranchii: Myliobatiformes) from Indian coastal waters

Thu, 01 Feb 2024 00:00:00 GMT

Title: Molecular phylogeny reconstruction and biogeographic pattern of Rays (Elasmobranchii: Myliobatiformes) from Indian coastal waters Authors: Kumar, Amit; Prakash, S Abstract: In the present study, the phylogenetic relationship among Myliobatiformes was reconstructed from the Indian waters based on the cytochrome c oxidase subunit I (COXI) gene. Overall, 307 sequences (18 collected from Mandapam fish landing centres, Tamil Nadu, and 289 from the previous literatures) from 34 species of Myliobatiformes were clustered under two major phylogenetic clades. The families Mobulidae, Rhinopteridae, Plesiobatidae, and Gymuridae were monophyletic, while the families Myliobatidae and Dasyatidae were polyphyletic. Further, the genera Aetomylaeus (Myliobatidae) and Pateobatis (Dasyatidae) show polyphyly by showing deep genetic divergence in the phylogenetic tree. Based on the phylogenetic tree analysis, Himanutra uarnak appears to be H. tutul in the Indian waters. Similarly, Neotrygon indica should be consistently used instead of N. kuhlii, as Indian specimens forms a distinct subclade within N. kuhlii species complex. In this study, it is also observed that several entries in the NCBI GenBank are erroneous; thus, an updation of data is recommended based on the present study. The biogeographic patterns revealed H. tutul, Maculabatis gerrardi, Brevitrygon imbricata, and Gymnura poecilura from the Indian coast form a separate haplotype compared to other geographical areas (Indo-west Pacific). In addition, G. poecilura and B. imbricata were genetically divergent between east and west coast populations of India, indicating a possibility of cryptic species. Page(s): 65-78

A comparative investigation of physicochemical and biological variables of Aerial & Port Blair Bays, Andaman Islands with focus on the anthropogenic influence

Thu, 01 Feb 2024 00:00:00 GMT

Title: A comparative investigation of physicochemical and biological variables of Aerial & Port Blair Bays, Andaman Islands with focus on the anthropogenic influence Authors: Sahu, B K; Goswami, P; Begum, M; Jha, D K; Vinithkumar, N V; Dharani, G Abstract: Major anthropogenic activities surround the Port Blair Bay, while Aerial Bay remains as a pristine environment. A field study was carried out during the south-west monsoon season (July – August, 2011) in the two bays to compare the physico-chemical parameters and their effect on phytoplankton community structure. Among the physico-chemical parameters, water temperature (p < 0.01, n = 18), DO (p < 0.01, n = 18) and TP (p < 0.05, n = 18) showed significant variation between the Bays. Salinity and Redfield ratio (N:P) was lower in Aerial Bay as compared to Port Blair Bay; while the Si:N ratio was higher in the Aerial Bay. The average chlorophyll-a concentration as well as species richness was found to be higher in the Port Blair Bay as compared to the Aerial Bay. The highest phytoplankton density and centric diatom abundance were observed in Port Blair Bay. In Aerial Bay, the centric diatoms like Dactyliosolen fragilissimus (44.5 %) and Guinardia flaccida (7.1 %) dominated, while in the Port Blair Bay, the centric diatom Skeletonema costatum (25.0 %) and a pennate diatom Nitzschia closterium (24.3 %) dominated the phytoplankton. The phytoplankton community was influenced by the nutrients from the tidal mud flats and rain-fed rivulets in the Aerial Bay; while, in the Port Blair Bay, the phytoplankton abundance was influenced by nutrients from land runoff, inundated areas and anthropogenic sources. Page(s): 79-90

Sediment organic matter content drives bivalve density in tropical oligotrophic seagrass ecosystem

Thu, 01 Feb 2024 00:00:00 GMT

Title: Sediment organic matter content drives bivalve density in tropical oligotrophic seagrass ecosystem Authors: Mishra, A K; Farooq, S H Abstract: Seagrass ecosystems are storehouses of both autochthonous and allochthonous organic matter due to their presence at the land and sea interface. This organic matter acts as a food source and plays an important role in biodiversity assemblages within seagrass ecosystems. The present study assessed the density of the bivalve (Cardita calyculata) along a gradient of sediment Organic Matter (OM %) in the mono-specific seagrass meadows of Thalassia hemprichii to those in adjacent bare sediments in the Andaman and Nicobar Islands (ANI) of India. The present study also assessed the correlation between sediment OM with Cardita's density and seagrass morphometric traits. C. calyculata density was 2-fold higher in T. hemprichii meadows (647.7±27.0 ind. m-2) than in the bare sediment (306±14.3 ind. m-2). Bivalve abundance correlated positively with OM in the seagrass meadows but showed no correlation in the unvegetated areas. The root branching of seagrass was higher, leading to increased C. calyculata density, suggesting a strong correlation of seagrass meadows with bivalves in nutrient-rich environments. The correlations between C. calyculata density and various plant traits were positive. Our study suggests that in the oligotrophic coastal ecosystems of the ANI, the positive influence of sediment OM of seagrass meadows on C. calyculata density is significant. Further studies looking at various interactions between seagrass and C. calyculata are essential to establish the precise interrelationship between seagrass and the biodiversity of associated faunal assemblages. Page(s): 91-100