As a result, there is no secondary data for phytoplankton sink rate as well as carbon flux in Bangladesh. Chlorophyll-a, sink rate and carbon flux have been estimated in the three selected stations located in the northeastern Bay of Bengal. This research has been carried out in the coastal area of some oceans, even most of the coastal part of the Bay of Bengal.
Observing seasonal variations in the sinking rate of chlorophyll-a and phytoplankton from large groups of phytoplankton. Understanding carbon flux variation associated with phytoplankton sinking rates at three stations on the northeast coast of Bangladesh. Until now, the most acceptable method for determining the sinking rate of phytoplankton was introduced under the name SETCOL method.
From changes in the vertical distribution of biomass, this system produced both sink rate and rise rate values (Bienfang, 1981). There is no study related to phytoplankton sink rate and carbon sink in the northeastern Bay of Bengal, so primary data is missing.
CHAPTER THREE
MATERIALS AND METHODS
Research extends
- Water collection for SETCOL and parameter testing
- Analysis of bio chemical parameters
- Total Suspended Solid (TSS)
- Nitrite-nitrogen (NO 2 -N)
- Phosphate-Phosphorus (PO 4 -P)
- Chlorophyll-a measurement
- Phytoplankton sinking rate measurement
- Total carbon estimation in each cell and in a specific depth
Thus, water had to be collected from 3 depths of the water column, so the sample was collected by a Nansen water sample bottle using a rented boat. Samples were taken from the surface, at 5 meters and 10 meters depth from 3 points of a specific station, keeping a distance of at least 10 meters from one to the other to avoid similarity. Then the filtered residue was collected in a bottle, after which the sample was preserved by adding 3-4 drops of 10% formalin previously prepared and taken to the laboratory.
Three replicates were done to increase accuracy and sample was collected in two seasons (monsoon and winter) from 3 respected stations. The filter paper was first dried in the oven and placed in the desiccator (at least 30 min at both stages). Oven-dried filter paper was then weighed. Sinking rates of particles were determined using a homogeneous sample method called SETCOL (Bienfang 1981). To determine phytoplankton sink rate, the average chl-a of 3 chambers of the SETCOL bottle was first calculated.
The net was then hauled to the surface and concentrated sample was taken and preserved with 5% buffered formalin. A 1 mL sample was taken in the S-R cell and left undisturbed for 15 min to allow plankton to settle. In the S-R cell, a 1 mL sample was taken and left undisturbed for 15 min to allow the plankton to settle.
During this research, carbon flux was estimated by multiplying sink rate and total carbon from phytoplankton according to Guo et al.
CHAPTER FOUR RESULTS
Physico-chemical parameters
- Temperature
- Water pH
Two-way ANOVA showed that the differences in water pH among the 3 stations and 2 seasons were significant (p<0.05). Two-way ANOVA showed that differences in water salinity among the 3 stations and 2 seasons were significant (p<0.05). The highest TDS value was observed at 30.6 g/L during winter at Teknaf station in the surface layer and the lowest TDS value was 2.8 g/L during monsoon at Patenga at a depth of 5 meters.
A two-way ANOVA results showed that variations in TDS between 3 stations and 2 seasons were significant (p<0.05). Two-way ANOVA results showed that variations in TDS between 3 stations and 2 seasons were significant (p<0.05). The highest concentration of NO2-N in Bashbaria station during monsoon and the value was 3.07 µg/liter and lowest value was 0.24 µg/liter in winter in the same station.
A two-way ANOVA results showed that variations in nitrite-nitrogen (NO2-N) between 3 stations and 2 seasons were significant (p<0.05). The highest value was 1.65 µg/litre at Teknaf station in winter at a depth of 10 meters and the lowest value was 0.32 µg/litre during monsoon in the same station. Two-way ANOVA results showed that variations in phosphate-phosphorus (PO4-P) between 2 seasons were significant (p<0.05).
The results of two-way ANOVA showed that the differences in silicate silicon (SiO3-Si) among the 3 stations and 2 seasons were significant (p<0.05). The lowest chl-a value was 0.12 µg/liter at a depth of 10 meters during monsoon at Bashbaria station, which is considered a less productive region. The results of two-way ANOVA showed that the differences in chlorophyll-a between 3 stations and 2 seasons and depth were significant (p<0.05).
The highest sinking rate was observed as 3.1728 m day-1 at Atenga during winter at 5 meters depth and the lowest value was 1.3368 m day-1 at Bashbaria during winter at 10 meters depth. The results of two-way ANOVA showed that the variations in phytoplankton sinking rate among the 3 stations and 2 seasons and depth were significant (p<0.05). The results of two-way ANOVA showed that the variations in total carbon among the 3 stations and 2 seasons were significant (p<0.05).
Carbon flux
Fig.19 : Some phytoplankton found during study period A) Cyclotell sp., B) Coscinodiscus sp., C) Lauderia sp., D) Cerataulina sp., E)Padiastrum sp., F) Amphora sp., G) Cylindrotheca sp. ., H) Dytilum sp., I) Melosira sp., J) Skeletonema sp., K) Thalassiothrix sp., L) Rhizosolenia sp. Fig.20: Mean and SD value comparison between two factors. (A) Carbon flux and sink rate (B) Chl-a and sink rate, (S1= Bashbaria, S2= Patenga, S3= Teknaf and M= Monsoon, W= Winter). TDS and salinity also showed correlation in this depth where Water Temperature had no direct correlation with other parameters.
On the other hand, PC 2 and PC 3 together accounted for 19.5% of the total variance, with NO2-N and SiO3-Si correlating with 0-meter depth, PO4-P showing correlation with 5-meter depth and sink rate with 10-meter depth . Both PC 3 and PC 4 together accounted for 19.5% of the total variance, with sinking rate showing positive correlation with station 2. On the other hand, both PC 3 and PC 4 combined accounted for 19.5% of the total variance, where sinking rate showed positive correlation during monsoon and SiO3-Si showed positive correlation in both seasons.
And most rest parameters showed no correlation with the season, but a correlation between them.
CHAPTER FIVE DISCUSSION
- SETCOL method-it’s applicability in field use
- Physico-chemical parameters
- Phytoplankton abundance and parameters effect
- Phytoplankton sinking rate and associated factors
- Carbon flux
Mahmood (1976) who studied in the Karnofully estuary showed that the pH of the water varied between 7.10 and 7.30 during monsoon and winter. A direct correlation between high water discharge during monsoon and water salinity was found. The only reason for the lower salinity during the monsoon is the addition of overland runoff and rainfall that dilutes the water and reduces the salinity.
The lowest value was recorded at Patenga during monsoon because the station is very adjacent to the Karnofully estuary and during monsoon a lot of fresh water was added after rain. According to Noori (1999), the mean value ranged from 0.126 to 1.198 µg/liter during monsoon on the southeastern coast of Bangladesh (Bay of Bengal). But in this study, a higher value was found in both Bashbaria and Patenga due to heavy attrition and growing industries. Noori (1999) also found that the average value of phosphate-phosphorus (PO4-P) during this season was 0.410 to 2.330 µg/liter, while this study showed that during monsoon a higher value was found in both Potenga and Bashbaria due to the high discharge, but reversed in Teknaf.
During this study, the SETCOL method was used to determine the sinking rate of phytoplankton by measuring chl-a. The most likely reason why the rate of diatom subsidence was higher is that the increased density resulting from silicification caused rapid subsidence (Raven, 2004). In winter, this percentage was higher than monsoon at all stations and was considered the proximate reason why the inundation rate was higher in winter than monsoon at that station.
The sinking rate depends on the level of turbulence, and the simple dependence of the sinking rate on the radius can be modified by turbulence (Provenzale, 2010), so during the high turbulent monsoon monsoon, the phytoplankton sinking rate in this study was higher than in winter. The most reliable reason for this was the abundance of phytoplankton and the rate of sinking. During the monsoon, the abundance of dominant species and their total cellular carbon in the water column were higher than in winter.
As a result, the carbon flow from the surface to the bottom was more than one times higher during monsoon than in winter. Of the three stations, Teknaf showed a very positive correlation within Chl-a, CF and TC and Patenga showed a very positive correlation with sink rate. Seasonal PCA showed that salinity, TDS, pH and PO4-P were positively correlated during winter and other two nutrients were positively correlated during monsoon.
CHAPTER SIX CONCLUSION
CHAPTER SEVEN
RECOMMENDATIONS AND FUTURE PERSPECTIVES
Interactions between diatom aggregates, minerals, particulate organic carbon and dissolved organic matter: Further implications for the ballast hypothesis. The role of transparent exopolymer particles (TEP) in the increase in apparent particle stickiness (α) during the decline of a diatom bloom. Air as the renewable carbon source of the future: an overview of CO 2 capture from the atmosphere.
Declining rates of phytoplankton in the Changjiang Estuary (Yangtze River): a comparative study between blooms of Prorocentrum dentatum and Skeletonema dorhnii. Sinking in freshwater phytoplankton: some ecological implications of cell nutrient status and physical mixing processes 1. Factors controlling year-round variability in carbon flux through bacteria in a coastal marine system.
Dynamics of transparent exopolymer particles (TEPs) and contribution to particulate organic carbon (POC) in Jaran Bay, Korea. Seasonal distribution of the phytoplankton community in a subtropical estuary of the southeastern coast of Bangladesh. A study of seasonal variation of micronutrients and standing harvest of phytoplankton in neritic waters off the southeast coast of Bangladesh (thesis, M.
APPENDICES
Table of pairwise comparison of sinking rate
Brief Biography of the author
