Impact of seasonality on the nutrient concentrations in Gautami-Godavari Estuarine Mangrove Complex, Andhra Pradesh, India

• Published in: Marine pollution bulletin 2018-04, Vol.129 (1), p.329-335
• Main Authors: Rao, Karuna, Priya, Namrata, Ramanathan, AL
• Format: Article
• Language: English
• Subjects: Aquatic ecosystems; Brackishwater environment; Dissolved nutrients; Dry season; Environmental Monitoring - methods; Estuaries; Estuarine dynamics; Estuarine environments; Eutrophication; Groundwater; Groundwater - chemistry; Groundwater discharge; India; Mangrove swamps; Mangroves; Marine ecology; Mineral nutrients; Mixing model; Nitrates; Nitrogen - analysis; Nitrogen removal; Nutrient concentrations; Nutrient ratio; Nutrients; Oxidoreductions; Phosphates; Phosphorus; Phosphorus - analysis; Rainy season; Removal; River discharge; River flow; Rivers; Rivers - chemistry; Seasonal variations; Seasonality; Seasons; Silica; Silicon dioxide; Spatiotemporal variation; Water discharge; Wet season; Wetlands
• ISSN: 0025-326X; 1879-3363
• DOI: 10.1016/j.marpolbul.2018.02.052

Spatiotemporal variations of dissolved nutrients were studied along Gautami-Godavari mangrove ecosystem to delineate their sources and fate. Average values of nitrate (NO3−), dissolved silica (DSi) and phosphate (PO43−) is 2.09 mg/l, 12.7 mg/l and 0.16 mg/l in wet season and 0.47 mg/l, 6.96 mg/l and 0.29 mg/l in dry season respectively. In wet season river discharge has significant influence on NO3− and DSi. In dry season, NO3− and PO43− are controlled by groundwater discharge, benthic exchange and various in situ processes owing to sediment redox condition. Mixing model shows net addition of phosphate in Coringa mangroves (95%) and Lower estuary (13%) and net removal of nitrate (24.79%) in Coringa mangrove and in estuary (58.9%). Thus present mangrove acts as net source for phosphate and net sink for nitrate and DSi. Nutrient ratio shows seasonal switching between potential Phosphorus and Nitrogen limitation in wet and dry season respectively. •River discharge is found to be the primary source of nitrate and dissolved silica in wet season.•In dry season, many sources like organic matter remineralization, benthic flux, groundwater etc. supply nutrients.•The contribution of groundwater should be considered which is generally neglected in estimating the nutrient budget.•Seasonal switching is observed between potential Phosphorus and Nitrogen limitation in the wet and dry season respectively.•The present mangrove acts as the net source for phosphate and net sink for nitrate and dissolved silica.