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Seasonal variation in size structure and production of autotrophic plankton community in eutrophied, low-light environment: A focus on Mesodinium rubrum

Labucis Atis, Labuce Astra, Jurgensone Iveta, Barda Ieva, Andersone Ingrida, Ikauniece Anda

Oceanologia

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2023

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Vol. 65 (2)

398--409

EN

Temporal variations in the primary production of the size-fractionated autotrophic plankton community were studied in coastal-estuarine waters of the eutrophic Gulf of Riga, Baltic Sea. The community was net-autotrophic during spring and summer and net-heterotrophic during autumn. The results of the present study clearly demonstrate strong covariation between net primary production (NPP) and <56 µm fractionated community biomass, particularly small-sized (16–33 µm) Mesodinium rubrum, implying that the majority of NPP stems from the lower end of the size spectrum. A pronounced size distribution shift was observed within the M. rubrum population. Large-sized (length ≥34 µm) M. rubrum was the most abundant in the first half of the productive season (until week 24), whereas small-sized M. rubrum dominated during the stratified period.

2

The Chlorophyll-a Response of Phytoplankton to Ratio N/P in Different Coastal Waters

Maslukah Lilik, Handoyo Gentur, Wulandari Sri Yulina, Sihite Catherine Berliana, Sarjito

Ecological Engineering & Environmental Technology

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2023

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Vol. 24, iss. 9

121--129

EN

Phytoplankton growth is influenced by the presence of nutrients N (nitrogen) and P (phosphor). Each region has a specific N/P ratio, due to the influence of anthropogenic inputs. This study aimed to assess the response of phytoplankton chlorophyll-a (Chl-a) biomass due to differences in N/P ratio by the influence of river flow in the north coast of Java; Jobokuto Bay (Jepara), the coastal waters of Semarang and the front of the Cisadane river. N-nutrients were analyzed in the form of N-NO3 (nitrate), and N-NH4+ (ammonium ions), and orthophosphate ions (P-PO42-). Nutrient analysis was spectrometric, using the reduction methods (nitrate), ammonium (indophenolblue), and phosphate (molybdenum-blue). Test for site differences using Kruskall-Wallis, followed by a posthoc test. The results showed that Semarang waters had a lower N/P (Stoichiometric) ratio than Jepara and Cisadane, which can be used to predict that P nutrient input is higher than N. This high P input impacts microalgal development (chlorophyll-a). In addition, we also found Semarang waters to have higher speciation of inorganic N in the form of ammonium, which is one of the drivers of eutrophication in these waters. The use of a ratio of N/P is very important in estimating the eutrophication process and can be used to estimate the dominance of nutrients entering the water due to anthropogenic activities in the upstream area.

3

Seasonal Driven Mechanism of the Surface Chlorophyll-A Distribution along the Western Coast of Sumatra

Sari Qurnia Wulan, Siswanto Eko, Utari Putri Adia, Saputra Okta Fajar, Lestiana Hilda, Holidi, Subiyanto, Yuniarti, Iskandar Iskhaq

Journal of Ecological Engineering

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2022

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Vol. 23, nr 11

254--260

EN

The chlorophyll-a (chl) abundances on the Fisheries Management Area of Indonesia Republic (WPP-RI 572), as fishery resources over the western coast of Sumatera (WSC) and Sunda Strait, were examined in this study. The extensive investigation on the mechanism ocean dynamics on chl variability along WSC was observed by using remotely sensed data on the surface. The spatial analysis was conducted using the Moderate Resolution Imaging Spectroradiometer (MODIS) Aqua Ocean colour data for a period of January 2003 to December 2015. On seasonal time scale, the surface chlorophyll-a (schl) concentration in the southern tip of Sumatra is higher than the schl in the northern tip of Sumatra. The obtained results showed that the schl concentration in the southern tip of Sumatra increases (decreases) during the southeast (northwest) monsoons. Interestingly, its interactions with the southeast monsoon wind result in intensified coastal upwelling along the monsoon trough in July – August. It triggered a large bloom of the schl concentration from the upwelling region of southern tip Sumatra. Moreover, the schl in the center region followed the peak of the equatorial wind during the period transition in the Indian Ocean which is controlling the dynamics ocean such as upwelling event. Meanwhile, the opposite situation of the schl concentration observed low along the western coast of Sumatra during the northwest monsoon. At the same time, strong upwelling observed at the northern tip of Sumatra was associated with intense cooling on the sea surface temperature. It triggered a large bloom of high schl water from the upwelling region of northern Sumatra Island.

4

Land Cover Changes and Impacts of Massive Siltation on the Mangrove Segara Anakan Lagoon System, Cilacap Indonesia

Ardli Erwin Riyanto, Yuwono Edy, Purwanto Anang Dwi

Journal of Ecological Engineering

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2022

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Vol. 23, nr 7

29--41

EN

Changing coastal zones in Indonesia, such as coral reefs, seagrass, and mangroves, have an impact on tropical ecosystems. Excessive exploitation and sedimentation, in particular, have threatened the mangrove at Segara Anakan Cilacap. In order to evaluate temporal land cover changes and the impact of high siltation on the Segara Anakan lagoon system in Cilacap, Indonesia, a research was conducted. The land cover data from SPOT 4 was available in 2008, and the Sentinel-2A data was available in 2019. The Normalized Difference Vegetation Index (NDVI) was used to enhance the Macro Class with supervised classification utilizing Maximum Likelihood techniques. Mangroves and water bodies declined between 2009 and 2019, whereas settlements and farmland areas increased, according to this study. In the western part of Segara Anakan, extensive siltation altered the biomass, structure, and composition of mangrove vegetation. At high sedimented habitats, Acanthus and Derris dominate, followed by Nypa. The changes in land cover and land use had an impact on socioeconomic factors. Decreases in water bodies and mangrove areas, as well as an increase in farmland, were significantly linked to a shift in society’s livelihoods from fishermen to farmers. The destruction of mangrove habitats in the Segara Anakan has been accelerated by anthropogenic activity and population pressure. Because this sensitive environment is constantly threatened by anthropogenic activity and climate change, effective management of the Segara Anakan Lagoon mangrove ecosystem is important for its long-term viability.

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Changing of Soil Properties under Drought and Saline Water Intrusion Conditions in Different Land-Use Patterns – A Case Study in the Ben Tre Province, Vietnam

Loi Le Tan, Minh Vo Quang, Duy Nguyen Ngoc

Journal of Ecological Engineering

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2022

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Vol. 23, nr 8

112--118

EN

The study aimed to assess the change of soil properties of land use patterns affecting drought and saline intrusion in the Ben Tre province during 2019–2020. Soil samples were taken, and the data on land use patterns of Rice, bare soil, Shrimp, and Coconut in three horizons were at 0–20 cm, 20–60 cm, and 60–100 cm. The analysis of soil pH, EC, organic matter, and bulk density was conducted to assess the changes in soil properties. The results showed that soil pH, EC, and salinity had to be slightly increased in 2020, but soil organic matter and bulk density were not changed. Therefore, the Ben Tre province’s drought and saline intrusion conditions had a negligible impact in general evaluation. However, it is necessary to perform more other studies to clarify the effects of drought and salinity.

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Satellite estimates of the long-term trend in phytoplankton size classes in the coastal waters of north-western Bay of Bengal

Miranda Joereen, Lotliker Aneesh Anandrao, Baliarsingh Sanjiba Kumar, Jena Amit Kumar, Samanta Alakes, Sahu Kali Charan, Kumar Tummala Srinivasa

Oceanologia

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2021

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No. 63 (1)

40--50

EN

The study presents long-term variability in satellite retrieved phytoplankton size classes (PSC) at two coastal sites, off Gopalpur and Visakhapatnam, in the north-western Bay of Bengal. The abundance-based models by Brewin et al. (2010) (B10) and Sahay et al. (2017) (S17), for retrieval of PSC (micro, nano, and picophytoplankton), from satellite data, were validated. Both the models performed well in the retrieval of nano and microphytoplankton. However, B10 performed poorly in retrieving picophytoplankton. The statistical analysis indicated better performance of the S17 model and hence was applied to Moderate Resolution Imaging Spectroradiometer onboard Aqua satellite (MODISA) data to understand the temporal (at monthly climatology) and spatial variability (from nearshore to offshore). The spatial distribution indicated nearshore dominance of micro and offshore dominance of picophytoplankton. In nearshore waters off Gopalpur, microphytoplankton dominated throughout the year except for months of south-west monsoon (June and July) where the dominance of picophytoplankton was observed. All PSC exhibited similar distribution at an annual scale with a primary peak during pre-monsoon (March and April) and a secondary peak during post-monsoon (September-November). However, microphytoplankton concentration during post-monsoon was higher off Gopalpur in comparison to Visakhapatnam. The higher microphytoplankton concentration during pre-monsoon was attributed to recurrent phytoplankton blooms. Whereas, post-monsoon increment could be attributed to enhanced phytoplankton growth by availing nutrients sourced from monsoonal precipitation induced terrigenous influx. The outcome of the present study recommends the use of the S17 model for satellite retrieval of PSC from the north-western Bay of Bengal.