Factors driving production of chlorophyll in phototrophic organisms in Keyport coastal waters, New Jersey
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Benjamin Aharoni
College:
The Dorothy and George Hennings College of Science, Mathematics, and Technology
Major:
Biotechnology/Molecular Biology
Faculty Research Advisor(s):
Shuting Liu
Abstract:
Algal blooms in the New Jersey coastal waters have been happening in recent years and have led to changes in water quality such as increasing turbidity, changing water chemistry, which potentially can indirectly impact wildlife. Therefore it's important to figure out what is causing algal blooms to understand and predict the changes to coast water's biogeochemical cycling.
This study investigates the relationship between nutrients and phototrophic organisms in the marine environment, with a specific interest in the relationship between chlorophyll concentration and the environmental factors measured. Field sampling occurred from April 2023 to January 2024 at four coastal sites in Keyport, New Jersey. Comparing the algal bloom period (late spring-summer) and non-bloom period (winter). Chlorophyll-a concentrations determined through spectrophotometry were significantly higher in the bloom period. SRP (Soluble Reactive Phosphate) concentrations were determined through the ascorbic acid method and spectrophotometry, its concentration was not significantly different between the two periods. Nitrate and nitrite concentrations were determined using cadmium reduction and spectrophotometric measurement and ammonium concentrations were analyzed using fluorometer after o-phthalaldehyde derivatization. Both nitrate+nitrite and ammonium showed significantly lower concentrations in the bloom period compared to the non-bloom period. Dissolved organic nitrogen (DON) was calculated as different between total dissolved nitrogen that was measured by a total organic carbon analyzer equipped with a nitrogen module and inorganic nitrogen. DON concentrations were also significantly lower in the bloom time. Bacteria concentrations were determined via DAPI staining and imaging under epifluorescence microscopy, it was found that there was a significantly higher abundance of bacteria during the bloom period compared to the bacteria population during the non-bloom period.
A Pearson Correlation analysis between the variables was used to determine their relationship’s significance to each other. It was found there was a significant positive relationship between temperature and chlorophyll-a concentrations, while there was a significant negative relationship between the nitrogen concentration (nitrate+nitrite, ammonium, DON) and chlorophyll-a, suggesting algal blooms occurred in warm seasons took up nitrogen nutrients from the New Jersey coastal water. The positive correlation between chlorophyll-a and bacterial abundance suggests phototrophic organisms support the population of bacteria in the water during the bloom period. Studying the changing biogeochemical patterns of New Jersey coastal waters during the bloom and non-bloom periods allows us to gain a deeper understanding of how these variables affect one another and how the presence of nutrients affects phototrophic organisms.
To conclude, this study gives insight into the intricate interactions between phototrophic organisms and biogeochemical cycling dynamics in the New Jersey coastal water. Future studies could further explore what phototrophic organisms contribute to the water column through their exudates and how those will shape the bacterial response.