Fish Assemblage Diversity of Dharla River, Bangladesh, With Relation to Environmental Variables: A Multivariate Analysis

River Research and Applications, Journal Year: 2025, Volume and Issue: unknown

Published: March 24, 2025

ABSTRACT The Dharla River is a significant freshwater system that runs through Bangladesh, India, and Bhutan, eventually meeting the Brahmaputra harboring numerous fish species. study aimed to investigate assemblage structures of in relation seasons environmental variables. Monthly data on assemblages variables were collected from five sites along between July 2022 June 2023. One‐way ANOVA was conducted at 5% significance level assess seasonal fluctuations variables, abundance, diversity indices. Various multivariate analyses, including canonical correspondence analysis (CCA), principal component (PCA), NMDS plot, used examine relationships species abundances, their variations. Furthermore, similarity (ANOSIM) percentage (SIMPER) applied evaluate communities throughout identify key cause diversity. parameters showed distinct differences during monsoon (July–October) compared pre‐monsoon (March–June) post‐monsoon (November–February). Seventy‐nine reported selected over 12 months, representing eight orders, 25 families, 57 genera. Fish abundance peaked season, while lowest number observed pre‐monsoon. ANOSIM revealed statistically variation ( p < 0.05) across seasons. Additionally, SIMPER indicated an average dissimilarity 43.35% among three seasons, with two Esomus danricus Cirrhinus reba ) contributing most this dissimilarity. Based samples all found be divided into groups. indices, Shannon‐Weaver H ), Pielou's evenness e Margalef richness D exhibited variations ranging 3.53 4.05, 0.60 0.82, 9.31 10.66, respectively. identified temperature, pH, nitrite, dissolved oxygen positively correlated structure River. This provides baseline information relationship which crucial for sustainable management conservation important trans‐boundary Rivers like other open‐water fishery resources Bangladesh.

Language: Английский

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High‐frequency dynamics of bottom dissolved oxygen in temperate shelf seas: The joint role of tidal mixing and sediment oxygen demand

Limnology and Oceanography, Journal Year: 2024, Volume and Issue: unknown

Published: Nov. 15, 2024

Abstract Dissolved oxygen (DO) in the bottom layer is essential for benthic organisms, and its temporal variations are widely concerned. However, previous studies have primarily focused on long‐term of DO, leaving high‐frequency (HF) dynamics inadequately understood. This study addresses this gap by utilizing two seafloor monitoring systems that provide 3‐year‐long HF records a typical temperate shelf sea, Bohai Sea, China. During stratified period each year, DO exhibits notable fluctuations superimposed seasonal cycle. These signals originate from tide‐induced vertical mixing, showing peaks at various tidal frequencies. Notably, significant shallow‐water observed due to frequency doubling semi‐diurnal diurnal currents. Moreover, demonstrates strongly asymmetric responses mixing time scales. To be specific, increases with intensity process being exceptionally rapid under conditions weak mixing. The underlying cause asymmetry markedly stronger gradient near seabed sediment demand. A process‐oriented biological model successfully reproduced observational features, further supporting our theoretical inference. findings highlight joint role demand modulating seas, underscoring their significance refined prediction future.

Language: Английский

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Geography, Trajectories, and Controls of Coastal Water Quality: More Rapid Improvement in the Shallow Zone of the Chesapeake Bay

Environmental Science & Technology, Journal Year: 2024, Volume and Issue: 59(1), P. 553 - 564

Published: Dec. 26, 2024

Many coastal ecosystems have suffered from cultural eutrophication and dead zones. In the Chesapeake Bay, water quality degradation is manifested in low dissolved oxygen, poor clarity, decreased submerged aquatic vegetation acreage. This research combines long-term monitoring data, science-based assessment methods, novel data analysis approaches (i.e., machine learning) toward understanding geography, trajectories, controls of which provides an example for management complex ecosystems. Results showed that attainment standards has improved both deep zone shallow since 1985, but more rapidly. addition, trajectory been affected by mainly external drivers nutrient reductions) and, to a lesser extent, internal temperature stratification). Reductions loads would improve attainment, whereas warming stratification decrease attainment. Furthermore, scenario analyses demonstrated importance managing nitrogen phosphorus loads. Overall, different trajectories controls, emphasizing geographical targeting with actions.

Language: Английский

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Ecological indicators of water quality and marshland impact area (MARia) index of Ligawasan Marsh: a critically important wetland in the Southern Mindanao, Philippines

Discover Environment, Journal Year: 2024, Volume and Issue: 2(1)

Published: Oct. 5, 2024

Abstract Wetland ecosystems are vital for both biodiversity and communities that depend on them. The Ligawasan Marsh in the southern part of Philippines is one most threatened wetlands country. Apart from increasing anthropogenic development, have faced warfare-driven threats hindered research conservation efforts area many decades. Our study first to investigate patterns physicochemical parameters, land use cover, relationship between change marshland environmental status. We also developed Marshland Impact Area (MARia) index assess potential impact contributions surrounding towns. found a strong negative correlation dissolved oxygen (DO) indicators pollution such as biochemical demand (BOD), chemical (COD), heavy metals. Interestingly, we observed elevated levels phosphate mercury at all sampling sites Marsh. landscape-level modelling showed these associated with expanding croplands urbanisation marsh. contribution cropland towns varied significantly, suggesting importance implementing local policies reduce impacts. With current yet remaims limited knowledge beyond safe Marsh, it crucial implement collaborative science-based governance integrate initiatives priorities global targets, Kunming-Montreal Global Biodiversity Framework, comprehensive sustainable approach conservation.

Language: Английский

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