Average Chlorophyll-a Concentration Research Articles

Analysis of Chlorophyll-a Variability in the Eastern Indonesian Waters Using Sentinel-3 OLCI from 2020-2021

The Eastern Indonesian waters are significant in influencing the global climate system and oceanic connectivity. However, the Indonesian Through Flow (ITF) facilitates the movement of waters from the Pacific Ocean to the Indian Ocean. This flow vertically mixes water masses in the Eastern regions, leading to the concentration of phytoplankton. In addition, the distribution of phytoplankton, indicative of chlorophyll-a concentration, is influenced by upwelling and downwelling phenomena. Chlorophyll-a, responsible for capturing carbon and producing oxygen in marine ecosystems, is important in regulating climate change. Moreover, oceanographic conditions play a significant role in the dispersion of chlorophyll-a concentration. Therefore, this study adopted ocean colour remote sensing technology to assess chlorophyll-a distribution. Monthly ocean colour data was collected by the multi-temporal Sentinel-3 Ocean and Land Colour Instrument (OLCI). The analysis output included chlorophyll-a concentration associated with currents and the El Nino Southern Oscillation (ENSO). Data processing using the Case-2 Regional Coast Colour (C2RCC) processor resulted in an average chlorophyll-a concentration in the Eastern Indonesian waters ranging from 0.16 to 0.52. The results showed higher chlorophyll-a levels during the southeast monsoon (July to September) and lower levels during the northwest monsoon (January to March).

Gross pelagic primary production in the Ems-Dollard estuary

Anthropogenic changes to estuaries, usually highly productive systems, may result in increased turbidity levels, suppress pelagic primary production and negatively affect ecosystem functions. The Ems-Dollard estuary, enclosed between the Netherlands and Germany, is such an estuary with a long history of human induced changes. From the mid-19th century until 1992, discharges of potato starch and straw-board industry waste water, with high contents of organic matter, negatively affected oxygen concentrations and increased nutrient levels of the system. The growing awareness of the deteriorating effects of these discharges on the ecosystem invoked a large research program, BOEDE, between 1976 and 1980. The aim of the current paper was to establish the recent gross pelagic primary production, to compare the results with the late seventies data and to relate possible changes to environmental variables such as suspended matter and nutrients. To this end, six stations from the North Sea into the inner area of the Dollard were visited 39 times in 2012–2013. During each sampling cruise, a so-called PocketBox, containing a number of sensors, provided a high spatial data resolution between stations. At each station, samples were collected for carbon fixation incubations using 14C. Average chlorophyll-a concentrations as reported in this study were lower compared to 1978–1980 for the seaward stations, and higher for the most inward station in 2012 and almost similar in 2013. Light attenuation coefficients in the outer areas were lower in 2012–2013 (1.22 m−1) compared to the values reported in the period 1976–1980 (1.59 m−1), indicating somewhat less turbid conditions. For the two other stations, light attenuation coefficients in the present study were similar to the late seventies' values, for the station near the entrance of the Ems River in the Ems-Dollard area, the coefficient was substantially higher. Pelagic primary production in the 2012–2013 period was about 120 g C m−2 y−1, mainly determined by the most seaward areas. The largest differences in gross primary production in the current study compared to the 1976–1980 period were found at the seaward stations where production in the late seventies was about 60% higher. In the Dollard-area, production hardly changed since the late seventies, but also stations near the Ems-river entrance into the Ems-Dollard area showed a clear decrease. Changes at the inward stations are to be contributed to an increased turbidity; the decrease at the outer areas to a decreased nutrient level, especially dissolved phosphorus and silicate, but possibly also nitrogen.

Cycle of Potential Fishing Area of WPP-NRI 711 Year 2011-2020

This study discussed the cycle of potential fishing areas in WPP-NRI 711 based on the distribution of Sea Surface Temperature (SST) and distribution of chlorophyll-a concentration using MODIS Aqua satellite imagery. The distribution of Potential Fishing Areas (PFA) was determined based on the distribution of the thermal front which was processed using MGET (Marine Geospatial Ecology Tools) and chlorophyll-a. Determination of fluctuations and the emergence period of PFA for 10 years (2011-2020) is carried out using wavelets. The results showed that the average SST in WPP-NRI 711 was 29 °C. The highest average SST is 31 °C in May of the Transitional I Season, and the lowest average temperature is 27.9 °C in February of the West Monsoon Season. The average chlorophyll-a concentration was 0.6 mg/m3, the highest average chlorophyll-a concentration was 0.76 mg/m3 in December West Monsoon Season, and the lowest average was 0.53 mg/m3 in October Transitional II Season. The average PFA distribution area is 1.111 km2, the highest average area is 1.324 km2 in the West Monsoon Season, then the lowest area is 924 km2 in the Transitional II Season. Based on global spectrum and wavelet analysis, it is known that the period of the appearance of PFA is 3-6 months or Seasonal. then in the Northern Region segment of WPP-NRI 711, covering the Natuna Sea, the appearance of PFA is strongly influenced by Seasonal current movements. Meanwhile in the southern part, including the Karimata Strait, the emergence of PFA is strongly influenced by river runoff and changing Seasons.

Analysis of Microalgae Growth Based on Availability of Nutrients in Freshwater

Microalgae have the potential to developed into medicinal products, wastewater treatment, food and energy products. Indonesia is a tropical country has the potential to produce microalgae. The growth of microalgae was influenced by several factors, the main factors is nutrition. This study aims to produce a pattern of mathematical relationships between microalgae growth and nutrient availability of the Laut Tawar Lake. Data collection was carried out for 30 days with a frequency of 7 days at 7 stations. Furthermore, the analysis was carried out to obtain concentration values of nitrate, phosphate and chlorophyll-a. Nitrate concentrations during the study ranged from 310-430 µg/L. The lowest average nitrate concentration was found at Station 4, which was 330 ± 34.64 µg/L and the highest was found at Station 3, which was 396.67 ± 41.63 µg/L. Phosphate concentrations during the study ranged from 18 – 22 µg/L. The highest phosphate concentrations were found at Station 1 and Station 6, which were 20.67 ± 0.58 µg/L and 20.67 ± 1.53 µg/L, and the lowest were found at Station 3, which were 19.00 ± 1.00 µg/L. The concentration of chlorophyll-a ranges from 5 – 12 µg/L. The highest average concentration of chlorophyll-a was obtained at Station 6, which was 10.00 ± 1.00 µg/L and the lowest was found at Station 3, which was 7.00 ± 2.00 µg/L. In conclusion, increasing nitrate in the Lake Laut Tawar did not increase microalgae biomass, microalgae species in that habitat were influenced by nutrient phosphate.

Spatial and temporal variations of dissolved CO2, CH4 and N2O in Lakes Edward and George (East Africa)

We report dissolved CO2, CH4 and N2O concentrations in two large East African lakes, Edward (surface area 2,325 km2, average depth of 37 m) and George (surface area 273 km2, average depth of 2 m). Lake George showed modest seasonal and spatial variations, and lower partial pressure of CO2 (pCO2) (26 ± 16 ppm, mean ± standard deviation), CH4 (234 ± 208 nmol/L) and N2O saturation levels (%N2O) (80 ± 9 %) than Lake Edward (404 ± 145 ppm, 357 ± 483 nmol/L, 139 ± 222 %). Surface waters in both lakes were over-saturated in CH4, and Lake George was under-saturated in CO2 while Lake Edward was slightly over-saturated in CO2. This difference was related to higher phytoplankton biomass in Lake George than Lake Edward, with average chlorophyll-a concentrations of 177 ± 125 and 18 ± 25 µg/L, respectively. Permanent high cyanobacterial biomass in Lake George led to uniform dissolved CO2, CH4 and N2O concentrations. In surface waters of Lake Edward, spatial variations of pCO2, CH4 and N2O were related to bottom depth, and locally (in particular in Katwe Bay) also related to the inputs of water from Lake George via the Kazinga Channel, a 40-km natural channel connecting the lakes. Short-term mixing events related to storms increased CO2, CH4 and N2O content in surface waters, in particular for CH4 and N2O. This indicates that mixing events in response to storms can create ‘hot moments’ for CH4 and N2O emissions to the atmosphere in tropical lakes, given the weaker vertical density gradients compared to higher latitude systems.

VARIABILITY ANALYSIS OF CHLOROPHYLL-A DISTRIBUTION ON THE COAST OF SOUTHWEST ACEH USING AQUA MODIS IMAGE

Chlorophyll-a has an important role in determining the trophic status and estimation of the fertility level of water. The aim of this study was to analyze the variability of the concentration of chlorophyll-a on the coast of Southwest Aceh. This study uses remote sensing technology using Aqua MODIS imagery, the image used is an annual Level 3 Standard Mapped Image (SMI) chlorophyll-a image with a period of 7 years from 2015 to 2021 and has a spatial resolution of 4 km. The image is processed using software, namely SeaDAS and ArcMap. The results of this study showed that the distribution of the highest annual chlorophyll-a concentration was in 2019 at 0.29 – 2.27 mg/m3, and the lowest chlorophyll-a concentration was found in 2020 ranging from 0.29 – 1.02 mg/m3. The average concentration of chlorophyll-a in Southwest Aceh waters for 7 years (2015-2021) shows a low chlorophyll-a concentration ranging from 0.29 to 1.22 mg/m3 and belongs to oligotrophic and mesotrophic waters

Hydrodynamics and water quality impacts of large-scale reclamation projects in the Pearl River Estuary

The mechanism that underlies the evolution of the seasonal environment and the effects of reclamation projects in the Pearl River Estuary (PRE) were studied by modeling the hydrodynamics, suspended sediment, and water quality. Due to the seasonal variation of the freshwater discharge, the residual currents in the estuary are generally larger during the summer than during the winter. Reclamation projects significantly affect the residual current fields and decrease tidal prisms across the PRE, resulting in the variation of water exchange and material transport process. During the summer, waters high in chlorophyll-a move downstream, with increased seaward residual currents, and they more widely range from the middle estuary to the estuarine mouth than during the winter; moreover, the chlorophyll-a value peaks in these areas. Reclamation projects significantly promote the expansion of waters high in chlorophyll-a towards the estuarine mouth. The distribution of suspended sediment, nitrate, ammonium, and silicate also obviously varies with altered water exchange and chlorophyll-a distribution. Average chlorophyll-a, suspended sediment, and silicate concentrations in the whole computational domain increase by 12.71%, 15.19%, and 1.91%, respectively, while the growth of algae consumes a large amount of nitrate and ammonium.

Mapping potential fishing zones based on sea surface temperature and Chlorophyll-A in the Waters of Aceh Besar, Indonesia

Utilization of potential fishery and marine resources is still not maximally used by fishermen. Sea surface temperatures and the spread of chlorophyll-a through remote sensing systems can be used as potential fishing zones. This study aims to determine potential fishing zones using geographic information systems through the distribution of sea surface temperatures and the value of chlorophyll-a concentrations in Aceh Besar waters which is expected to improve the sustainability of fishing efforts. This research was conducted in January-December 2019 using geographic information system by extracting from Aqua-MODIS satellite image with resolution of 4 km and sea surface temperature overlay method with chlorophyll-a concentration. The results found the highest sea surface temperature value was in April at 31.62°C and the lowest temperature was in December at 28.45°C. The highest average chlorophyll-a concentration in Aceh Besar waters was 1.53 mg/m3 in December and the lowest concentration of chlorophyll-a in June and September was 0.20 mg/m3. Suspected potential fishing zones during January to December 2019 were found as many as 62 potential fishing zones, namely in the Western, Northwest and Eastern waters of Aceh Besar. The most zones are in December as many as eight zones, namely in the Western, Northwest and East parts of Aceh Besar waters and the least found in July as many as one zone that is in the Western part of Aceh Besar waters. When compared to fishing operations areas, the potential fishing zone is in the western part of Aceh Besar waters.

Comprehensive modelling and cost-benefit optimization for joint regulation of algae in urban water system

Algal blooms in urban water system is an international concern, which especially in China, have become a major obstacle to the urban water environment improvement since the preliminary achievements were made in the treatment of black and odorous water bodies. The complex blooming mechanisms require a joint regulation plan. This study established a framework that consisted of three steps, i.e., simulation, optimization, and verification, to build an optimal joint regulation plan. By taking the urban river network in Suzhou Pingjiang Xincheng as a case study, the cost-benefits of six alternative regulation measures were assessed using an algal bloom mechanism model and the discounted cash flow model based on 70 regulation scenarios. The joint regulation plan was optimized using the marginal-cost-based greedy strategy on the basis of the cost-benefits of different measures. The optimized joint plans, which were verified to be global optima, were more cost-effective than the designed regulation scenarios, and reduced the average chlorophyll-a concentrations by 55.3%–60.1% compared with the status quo. Applying the optimized cost allocation ratios of each measure to adjust the existing regulation scheme of another similar case verified that the optimization results had great generalizability.

Trend and dynamic of chlorophyll-a concentration over the Arabian Gulf A long-term study using MODIS data (2004 – 2019)

Chlorophyll-a concentration in water is an indicator of phytoplankton density, which in turn is crucial, as it represents the base of the ecological life in seas and oceans. Any increase or decrease in the number of phytoplankton may contribute to disruption to the ecological cycle in the seawater. The density of phytoplankton is also an important indicator of water quality. Traditionally, water samples are collected in the field and analysed in the laboratory to find the density of phytoplankton in a specified amount of water. Recently, remote sensing has led to the development of advanced and remote methods to detect phytoplankton density, chiefly by extracting near-surface chlorophyll-a concentrations. In this study, MODIS (Aqua) Level 3 data (64 images) were used to extract average chlorophyll-a concentration at time points from 2004 to 2019 (over 16 years) for the Arabian Gulf, where the Level 2 (11 images) data were used to determine the accuracy of the estimated values via MODIS (Aqua) using field data taken from the waters of the State of Kuwait (25 points). The results showed good accuracy for MODIS (RMSE = ± 1.066), and it also shows that the temporal seasonal averages change in a annual-cycles, and that the trend decreased from 2004 to 2019, by about 0.7 mg/m−3

Assessment of some key indicators of the ecological status of an African freshwater lagoon (Lagoon Aghien, Ivory Coast).

The supply of drinking water is a vital challenge for the people who live on the African continent, as this continent is experiencing strong demographic growth and therefore increasing water demands. To meet these needs, surface water resources are becoming increasingly mobilized because underground resources are not always available or have already been overexploited. This situation is the case in the region of Abidjan in the Ivory Coast, where the drinking water deficit is a growing problem and it is therefore necessary to mobilize new water resources to ensure the supply of drinking water. Among the potential resources, local managers have identified a freshwater lagoon, Lagoon Aghien, That is in close proximity to the city of Abidjan. With the aim of enhancing knowledge on the ecological functioning of the lagoon and contributing to the assessment of its ability to provide drinking water, several physical and chemical parameters of the water and the phytoplankton community of the lagoon were monitored for 17 months (December 2016-April 2018) at six sampling stations. Our findings show that the lagoon is eutrophic, as evidenced by the high concentrations of total phosphorus (>140 μg L-1), nitrogen (1.36 mg L-1) and average chlorophyll-a (26 to 167 μg L-1) concentrations. The phytoplankton community in the lagoon is dominated by genera typical of eutrophic environments including mixotrophic genera such as Peridinium and by cyanobacteria such as Cylindrospermopsis/Raphidiopsis, Microcystis and Dolichospermum that can potentially produce cyanotoxins. The two rainfall peaks that occur in June and October appeared to be major events in terms of nutrient flows entering the lagoon, and the dynamics of these flows are complex. Significant differences were also found in the nutrient concentrations and to a lesser extent in the phytoplankton communities among the different stations, especially during the rainfall peaks. Overall, these results reveal that the quality of the lagoon’s water is already severely degraded, and this degradation could increase in future years due to increasing urbanization in the watershed. These results therefore raise questions about the potential use of the lagoon as a source of drinking water if measures are not taken very quickly to protect this lagoon from increasing eutrophication and other pollution sources.

A biological Indian Ocean Dipole event in 2019

The 2019 positive Indian Ocean Dipole (IOD) event in the boreal autumn was the most serious IOD event of the century with reports of significant sea surface temperature (SST) changes in the east and west equatorial Indian Ocean. Observations of the Visible Infrared Imaging Radiometer Suite (VIIRS) onboard the Suomi National Polar-orbiting Partnership (SNPP) between 2012 and 2020 are used to study the significant biological dipole response that occurred in the equatorial Indian Ocean following the 2019 positive IOD event. For the first time, we propose, identify, characterize, and quantify the biological IOD. The 2019 positive IOD event led to anomalous biological activity in both the east IOD zone and west IOD zone. The average chlorophyll-a (Chl-a) concentration reached over ~ 0.5 mg m−3 in 2019 in comparison to the climatology Chl-a of ~ 0.3 mg m−3 in the east IOD zone. In the west IOD zone, the biological activity was significantly depressed. The depressed Chl-a lasted until May 2020. The anomalous ocean biological activity in the east IOD zone was attributed to the advection of the higher-nutrient surface water due to enhanced upwelling. On the other hand, the dampened ocean biological activity in the west IOD zone was attributed to the stronger convergence of the surface waters than that in a normal year.

Cyanobacterial Biomass Produced in the Wastewater of the Dairy Industry and Its Evaluation in Anaerobic Co-Digestion with Cattle Manure for Enhanced Methane Production

The unique perspective that microalgae biomass presents for bioenergy production is currently being strongly considered. This type of biomass production involves large amounts of nutrients, due to nitrogen and phosphorous fertilizers, which impose production limitations. A viable alternative to fertilizers is wastewater, rich in essential nutrients (carbon, nitrogen, phosphorus, potassium). Therefore, Arthrospira platensis was cultivated in 150 mL photobioreactors with 70% (v/v) with the wastewater from a dairy industry, under a regime of light:dark cycles (12 h:12 h), with an irradiance of 140 μmol m−2 s−1 photon. The discontinuous cultures were inoculated with an average concentration of chlorophyll-a of 13.19 ± 0.19 mg L−1. High biomass productivity was achieved in the cultures with wastewater from the dairy industry (1.1 ± 0.02 g L−1 d−1). This biomass was subjected to thermal and physical treatments, to be used in co-digestion with cattle manure. Co-digestion was carried out in a mesophilic regime (35 °C) with a C: N ratio of 19:1, reaching a high methane yield of 482.54 ± 8.27 mL of CH4 g−1 volatile solids (VS), compared with control (cattle manure). The results demonstrate the effectiveness of the use of cyanobacterial biomass grown in wastewater to obtain bioenergy.

Spatial-Temporal Variability of Chlorophyll-a Concentration in Cenderawasih Bay and Surrounding Waters

Chlorophyll-a is one of the parameters determining the primary productivity of water. In the fisheries sector, information on chlorophyll-a concentration in marine waters is very important for the prediction of fishing grounds. This study aims to analyze the variability of chlorophyll-a concentrations in Cenderawasih Bay and the surrounding waters, both spatial and temporal variability. Data from the Aqua-MODIS Level 3 monthly composite period from January to December 2019 was used to determine the concentration of chlorophyll-a. Time-series data are used to determine fluctuations of chlorophyll-a concentrations, while interpolation with the kriging method is used to determine the spatial distribution of chlorophyll-a. The analysis showed that the monthly average value of chlorophyll-a concentration in the study area ranged from 0.1988 – 0.3415 mg.m-3. The average value of chlorophyll-a concentration increases from March to June and then decreases in July or August. The highest average chlorophyll-a concentration was in March and the lowest in January. The maximum chlorophyll-a concentration in April and the minimum in August, which is around 9.1089 mg.m-3 and 0.0975 mg.m-3, respectively. The concentration of chlorophyll-a in Cenderawasih Bay and its surrounding waters is dominated by a low concentration, which ranges 0.1482 – 0.3158 mg.m-3. Generally, the variability of chlorophyll-a concentrations in the study area is influenced by seasons. The average chlorophyll-a concentration is high in the Transition I (West-east) and East seasons and will decrease in Transition II (East-West) until the West season. Spatially, chlorophyll-a concentrations in coastal areas are higher than in offshore waters. High chlorophyll-a concentrations are found around the border between Nabire Regency and Waropen Regency. The amount of run-off flow that supplies nutrients from the mainland greatly affects the high concentration of chlorophyll-a in the coastal area.

Phytoplankton communities of the Barents Sea frontal zone during the early spring period

In April 2018, complex studies of phytoplankton communities were carried out in the northwestern Barents Sea in the region of the Polar Front (74.8°-76.2° N) in a layer of 0-50 m. The region under study encompassed surface Arctic water and Atlantic water of the Fram branch (which conditionally corresponds to the Arctic water mass) divided from the Atlantic water mass by the Polar Front. Phytoplankton community on both sides of the front were represented by early spring complex, 90% of biomass was formed by diatoms (Achnanthes taeniata, Nitzschia grunowii, Thalassiosira antarctica). In water of Atlantic origin Phaeocystis pouchetii were found among the dominants. However, the level of development of microplankton was significantly higher in water from the Arctic Basin. The highest chlorophyll-a concentrations referred to surface Arctic water (3.13±0.43 mg/m3) and Atlantic Fram water (2.04±0.29 mg/m3). The concentration of chlorophyll-a at the stations performed in the Atlantic water mass was an order of magnitude lower - 0.50±0.26 mg/m3. Thus, during the early-spring period, the Polar Front is a powerful boundary that limits exclusively the level of development and quantitative indicators of the early spring microphytoplankton complex. The front line separates the more productive Arctic water, with average chlorophyll-a concentrations of 2-3 mg/m3, from the Atlantic water, in which concentrations of this pigment are an order of magnitude lower.

Seasonal forecast method of cyanobacterial bloom intensity in eutrophic Lake Taihu, China

在太湖、巢湖、滇池、洱海、三峡水库等我国重要湖泊和水库，蓝藻水华时常发生但年际之间藻情往往有较大差异，给蓝藻水华的防控物资及人员投入、湖库水源地水质安全保障带来较大的挑战，亟待探索周年尺度的蓝藻水华强度预测方法.本文收集了太湖连续15年的蓝藻水华情势观测数据和同步的气象、水文数据用于构建蓝藻水华预测模型，提出了利用遥感反演的蓝藻水华面积（A_BL）及人工观测的水体浮游植物叶绿素a浓度（[Chl.a]_LB）共同表征的蓝藻水华强度指标（BI）.分析了太湖年尺度的BI值与环境条件的关系，提出了基于年初能够掌握的气象、水文、营养盐等综合环境指标进行年度BI预测的统计模型.结果表明，太湖年度BI值与冬季及初春（12—3月）日均水温（WT_12-3）、冬春季有效积温（AT_12-3）、前一年降雨总量（RF_YB）等环境因子呈显著正相关，与冬季及初春的水体总氮（TN_12-3）、溶解性总氮（DTN_12-3）、总磷（TP_12-3）及溶解性总磷（DTP_12-3）不存在统计上的显著相关关系.此外，本研究开展了基于上述因子（BI为因变量，其余环境因子为自变量）的多元（或一元）回归分析，并遴选出最优模型.总体而言，最优模型的模拟计算结果与实测浓度具有较高的一致性，因此本研究得出的模型对太湖蓝藻水华年际强度预测具有较高精度.本研究对太湖等富营养化湖库蓝藻水华的中长期预测具有指导意义.;Many important lakes and reservoirs of China, including Lake Taihu, Lake Chaohu, Lake Dianchi, Lake Erhai and Three Gorges Reservoir, were plagued with cyanobacterial blooms. However, the intensity of the blooms in these freshwaters varied significantly in different years, which exhibited significant challenges to the blooms collection organizations and drinking water plants, leading to the urgent need to cyanobacteria blooms prediction model based on annual dataset. Therefore, the long-term (15 years) observation data and meteorological and hydrological datasets of Lake Taihu were collected for the prediction of algal blooms. In current study, cyanobacterial bloom intensity index (BI) were proposed with the consideration of yearly average blooms area interpret by high frequency remote sensing images and whole lake average chlorophyll-a concentration. Furthermore, environmental factors, such as water temperature, rainfall, water level, nitrogen and phosphorus concentrations were used as the crucial factors to predict BI. Our results showed that average water temperature in winter and early spring, as well as the rainfall of the former year were significant positive factors of the yearly BI value in Lake Taihu. While the nutrient-related factors in early spring had no significant relationships with BI. In addition, a multiple (or univariate) regression analysis based on the above factors (BI was the dependent variable and the remaining environmental factors were the independent variables) were performed in this study, and the optimal model was selected. In general, the predicted results of the selected optimal model had a high consistency with the measured concentrations, thus the model obtained in this study had relatively high accuracy for predicting the interannual intensity of cyanobacteria blooms in Taihu Lake. This study may serve reliably for the medium- and long-term prediction of cyanobacteria blooms in Lake Taihu, and other eutrophic lakes.

Trends in numbers of the Critically Endangered Chinese Crested Tern Thalasseus bernsteini and sympatrically nesting Greater Crested Tern T. bergii in the Matsu Archipelago, Taiwan

SummaryThe Chinese Crested TernThalasseus bernsteini(CCT) is likely the most critically endangered seabird species in Asia. The Matsu, Penghu, Jiushan, and Wuzhishan Archipelagos along the China coastline, plus Yeonggwang County in South Korea, are the five areas where this species is currently confirmed to breed. According to census and historical data collected in the Matsu Archipelago from 2004 to 2017, there was an average of 10 ± 4 adult CCT individuals at the Matsu Islands Tern Refuge (MITR) during the breeding season. CCT nested only in association with Greater Crested TernsT. bergii(GCT) among seven protected islands in the MITR, and the numbers of observed breeding individuals of the two species were positively correlated (r = 0.59,P< 0.001). We used generalized linear models to examine the effects of chlorophyll-a concentrations in surrounding marine habitats, typhoon frequency, and in-season shifts in colony location on inter-annual variation in numbers of breeding individuals and productivity (chick:adult ratios) of both CCT and GCT at the MITR from 2004 to 2017. Average chlorophyll-a concentrations during July-August obtained from the MODIS satellite were positively correlated with the annual maximum number of GCT at the MITR, but not that of CCT. In addition, we found that nest abandonment events during early incubation at the mixed-species colonies were associated with in-season shifts in colony location and delayed nesting chronology, thereby extending nesting into the peak typhoon season during July and August. The effects of in-season colony shifts on nesting chronology and the additive effects of typhoons caused a significant decline in CCT breeding success during the study period. We propose more rigorous monitoring to ascertain the root causes of in-season colony shifts of terns and then determine possible solutions. Additionally, creating educational programmes to increase public awareness towards seabird conservation could prove beneficial.

Mapping of trophic states based on nutrients concentration and phytoplankton abundance in Jatibarang Reservoir

Jatibarang Reservoir is one of the Indonesian Reservoirs, which used for human activities such as tourism and agriculture. These activities will provide input of organic matter and nutrients into the water. These materials will impact water quality and eutrophication process. Eutrophication is the water enrichment by nutrients, especially nitrogen and phosphorus which can promote the growth of phytoplankton. Some indicators of eutrophication are increasing nutrients, trophic states, and change of phytoplankton composition. The relationship between water quality and phytoplankton community can be used as an indicator of trophic states in Jatibarang Reservoir. The aim of this study was to analyze the effect of nutrients concentration and phytoplankton abundance to the trophic states and mapping trophic states based on nutrients concentration and phytoplankton in Jatibarang Reservoir. This study was conducted in June and July 2017 at 9 stations around Jatibarang Reservoir. The results showed that average concentration of nitrate, phosphate, and chlorophyll-a in Jatibarang Reservoir was 0.69 mg/L, 0.27 mg/L, and 1.66 mg/m3, respectively. The phytoplankton abundance ranged 16-62,200 cells/L, consists of 21 genera of four classes, i.e. Chlorophyceae, Cyanophyceae, Bacillariophyceae, and Dinophyceae. Cyanophyceae was a dominant phytoplankton group based on the composition of abundance (>80%). High nutrient concentrations and phytoplankton dominated by Anabaena (Cyanophyceae) which indicated that the waters in Jatibarang Reservoir were eutrophic.

Multi-sensor satellite and in situ monitoring of phytoplankton development in a eutrophic-mesotrophic lake

Phytoplankton indicated by its photosynthetic pigment chlorophyll-a is an important pointer on lake ecology and a regularly monitored parameter within the European Water Framework Directive. Along with eutrophication and global warming cyanobacteria gain increasing importance concerning human health aspects. Optical remote sensing may support both the monitoring of horizontal distribution of phytoplankton and cyanobacteria at the lake surface and the reduction of spatial uncertainties associated with limited water sample analyses. Temporal and spatial resolution of using only one satellite sensor, however, may constrain its information value. To discuss the advantages of a multi-sensor approach the sensor-independent, physically based model MIP (Modular Inversion and Processing System) was applied at Lake Kummerow, Germany, and lake surface chlorophyll-a was derived from 33 images of five different sensors (MODIS-Terra, MODIS-Aqua, Landsat 8, Landsat 7 and Sentinel-2A). Remotely sensed lake average chlorophyll-a concentration showed a reasonable development and varied between 2.3±0.4 and 35.8±2.0mg·m−3 from July to October 2015. Match-ups between in situ and satellite chlorophyll-a revealed varying performances of Landsat 8 (RMSE: 3.6 and 19.7mg·m−3), Landsat 7 (RMSE: 6.2mg·m−3), Sentinel-2A (RMSE: 5.1mg·m−3) and MODIS (RMSE: 12.8mg·m−3), whereas an in situ data uncertainty of 48% needs to be respected. The temporal development of an index on harmful algal blooms corresponded well with the cyanobacteria biomass development during summer months. Satellite chlorophyll-a maps allowed to follow spatial patterns of chlorophyll-a distribution during a phytoplankton bloom event. Wind conditions mainly explained spatial patterns. Integrating satellite chlorophyll-a into trophic state assessment resulted in different trophic classes. Our study endorsed a combined use of satellite and in situ chlorophyll-a data to alleviate weaknesses of both approaches and to better characterise and understand phytoplankton development in lakes.

Variasi Musiman Hubungan Antara Parameter Oceanografi Dengan Hasil Tangkapan Ikan Tongkol Berdasarkan Data Harian Di Selat Bali

Mackerel fish that classified pelagic fish and an export commodity in Indonesia. Distribution of mackerel fish are foundn all Indonesian waters, one of them in the Bali Strait. Distribution of mackerel fish influenced by oceanographic condition such as sea surface temperature (SST) and chlorophyll-a concentration. SST and chlorophyll-a concentrations are environmental parameters that can provide information on fishing ground. The purpose of this research is explained the temporal fluctuation and relationship between SST and chlorophyll-a concentration with mackerel fish had been catch in Bali Strait waters during 2011-2016. Data were analyzed using simple correlation analysis with 95% confidence interval. Temporally, the highest average SST occurred during the transition season I (March-May) and the lowest in the east season (June-August). The highest average chlorophyll-a concentration occurs in the east season and the lowest in the west season (December-February). The highest catch of mackerel fish occurred during transitional season II (September-November) and lowest in west season. The association between SST and chlorophyll-a concentration on mackerel fish catch showed low correlation with significant relationship, whereas concentration between SST and chlorophyll-a concentration strong with significant correlation