Humans have such a huge impact on the quality of our local bodies of water, but in our busy day to day lives, we barely give it a thought. It has long been proven that we have a problem with maintaining a mutually beneficial relationship with the environment. Our blatant disregard for what we have is ultimately going to come back to bite us, and in fact, we are already seeing it because if we aren't exhausting our resources, we are poisoning it.
One would think extra nutrient input into the water would be beneficial, however it has the opposite effect. According to Daniel Conley, a Professor of Quaternary Sciences at Lund University, we are seeing many consequences of eutrophication as a result of nutrient loading. Eutrophication, the enrichment of an ecosystem, has limiting nutrients such as nitrogen, phosphorus, or even both, as co-limiting nutrients (Conley et al). A limiting nutrient is an element that is essential for species growth, in that the availability of this nutrient controls the maximum amount of organisms within an ecosystem. In the event of heavy rainfall, which causes the flooding of waste treatment plants and phosphorus runoff, it creates an ideal environment that usually triggers an algal bloom. Once this happens, Phytoplankton growth is no longer nutrient limited. Some Algae blooms are harmless to humans, while others such as the Red tide produce dangerous toxins that harm aquatic organisms, such as bivalves (filter feeders), and humans.
Once there is a massive amount of phytoplankton growth, the environmental stress causes a drop in dissolved oxygen, which leads to fish killings. Anoxic 'dead zones' are typically caused by respiration and decomposition. It's important to know that dissolved oxygen, in this case, comes from two different sources: diffusion from the air and as a waste product from aquatic primary producers (plants/phytoplankton). At night, however, aquatic autotrophs (plants/phytoplankton) reverse this process and consume oxygen, leaving even less for local marine organisms. In ecosystems with a large amount of algae death, the bacteria that decompose them will also respire. Oxygen is very limited and once the dissolved oxygen drops below a life sustaining level, many aquatic organism die.
Jamaica Bay is located between Brooklyn, Queens, and Nassau County. This urbanized estuary has a significant amount of human activity along its shoreline. It is known that Jamaica Bay receives nitrogen in the form of ammonium, nitrate, nitrite from several sources such as wastewater treatment plants, sewer overflows during heavy rainfall, and landfills lining the shore (Benotti et al). Due to the water pollution, Jamaica bay has been experiencing marsh loss where eutrophication of the Bay is speculated to have caused the decrease in S. alterniflora biomass within peat soil. According to Mark Benotti, Ph .D. in Coastal Oceanography, in addition to the loss structural integrity of the peat, the redistribution of S. alterniflora energy from roots to shoots may have also been a contributing factor in marsh deterioration. In 1995, it was found that the nitrogen concentrations were five time higher in the upper portion of the estuary than the mouth of the estuary. This is because wastewater treatment plants accounts for roughly 89% of the nitrogen loading, three of which are in the upward portion of bay, while one is at the mouth. The highest concentrations of nitrogen was in areas of low mixing or areas that were not well flushed, which are generally to the east near Hempstead Town waters (Benotti et al).
To measure the Phytoplankton biomass, the easiest and effective method is by measuring chlorophyll a. chlorophyll a sensors measure fluorescence in micrograms per liter to roughly estimate the chlorophyll concentration in the sample of water. Therefore, because all Phytoplankton have chlorophyll a, the amount of chlorophyll allows us to estimate the Phytoplankton concentration.
This brings us to how we went about testing the water quality of Jamaica Bay. Our goal was to obtain comprehensive measurements of the water quality by means of the salinity (the amount of salt in the water), chlorophyll a fluorescence, dissolved oxygen, temperature, Secchi depth (water transparency; the depth at which the Secchi Disk was no longer visible), and ammonium levels. We predicted that in areas of low mixing, high wastewater effluent, the high levels of ammonium, a nutrient known to stimulate phytoplankton growth, will result in higher levels of chlorophyll a. Therefore, in areas with a large amount of Phytoplankton, oxygen is significantly reduced, resulting in anoxic 'dead zones'.
During three separate trips, which were approximately 2-3 weeks apart, we accessed the water quality from docks and from transect by boat. The first trip was 3 stops at Inwood Marina, Broad Channel, and Gateway Marina. The second trip was an 8-station transect at approximately the following locations:
Lastly, the third trip was 2 stops at Inwood and gateway just to confirm the overall water quality trend of this area. We took onsite measurements and took water samples back to the lab for further chlorophyll a and chlorophyll testing. In addition to taking raw chlorophyll measurements, we also extracted chlorophyll from the water samples. This was a two-step process where a filtered water sample was put into acetone and frozen overnight, then thawed and measured via laboratory fluorometer. To test the ammonium, we had to prepare the water sample with working reagent and reverse osmosis water. Chlorophyll measurements were then calibrated according to the ammonium standards, which were prepared within a 2 hours to ensure that all of the reactions were in the same phase on the curve.
The working reagent was prepared according to Holmes's A simple and precise method for measuring ammonium in marine and freshwater ecosystems, which accounted for issues such as matrix effects and background fluorescence. Background fluorescence comes from unwanted substances in the water sample (Holmes, et al. 1999). Matrix effects are essentially intensity alterations caused by OPA reacting with the sample ammonium, though these intensity alterations may be very small, the effect could be significant depending on the water sample. (Holmes, et al 1999).
Though we took measurements for ammonium, salinity, oxygen concentration, Secchi Depth, temperature, the "Results of the Project", this article will mainly focus on chlorophyll a concentrations.
Figure 1 below represents the overall chlorophyll a trend within Jamaica Bay, in that as one moves away from the mouth of the estuary, towards Inwood, the chlorophyll levels increased. From the correlation coefficient, a statistical means of determining correlation and dependence between two variables, it was confirmed that ammonium and chlorophyll a has a strongly positive correlation. In other words, as ammonium levels increases, so does chlorophyll.
To get a better idea of the water quality history, we went to the Department of Environmental Protection, Hempstead who kindly provided us with data from May to October 2015. Their sensors recorded water quality data roughly every 10-12 minutes continuously. We simplified this massive amount of data by reducing recordings to twice daily and entering data into the following graph starting in July of 2015 and ending in October of 2015.
Again we can see the overall water quality gradient where Riis Landing (closest to Gateway Marina and the opening of Jamaica Bay to the Atlantic Ocean) has the lowest chlorophyll a levels, while Inwood has the highest. Interestingly, there is very little difference between Broad Channel and Inwood chlorophyll fluctuations despite the distance. Since chlorophyll and ammonium have a direct relationship, it can be concluded that because our ammonium data increased as you moved toward Inwood, the amount of chlorophyll followed suit. It is possible that ammonium concentration stimulated phytoplankton growth, but another contributor to the obvious difference in chlorophyll level along the transect from Inwood Marina to the oceanic inlet was the amount of mixing. It was observed that in areas like Gateway Marina and Riis landing, they have much more water/nutrient exchange with the sea, while areas like JFK and Inwood, the water was much more stagnant. Those stagnant areas or areas of low mixing hold nutrients for a longer period of time, thus allowing the phytoplankton to culture.
Overall nutrient input into Jamaica Bay, combined with reduced mixing with oxygenated oceanic water will tend to cause anoxic events. These events will be especially frequent in late summer when water temperature is high and wind mixing relatively low. Continuous hypoxic/anoxic conditions caused by algal blooms will cause a reduction of water quality and a major loss in biodiversity and put on additional stress on an marine ecosystem. This stress will impact growth and reproduction, population concentration and cause habitat loss, and a disruption of life cycles. An expansion of the anoxic zone will depend on how climate change affects the water stratification and nutrient runoff (Diaz et al). According to Robert Diaz, Professor of Marine Science, and Rutger Rosenberg, Professor of Marine Ecology, it was predicted that climate change will cause rainfall patterns to increase stratification and agricultural runoff, thus we will see an overall elevated level of nutrient loading. As a result, there will be an increase in primary production, a decrease in dissolved oxygen, and expansion of hypoxic/anoxic zones. It has been said that oxygen-depletion now ranks among overfishing and habitat loss (Diaz et al).
Correcting this problem is definitely difficult because it requires humans to reevaluate what they are doing as far as pollution and also requires further research and effort into reestablishing bivalves communities. Hypoxic conditions can be significantly reversed if we invest in nutrient input management of wastewater treatment plants, sewer overflows, and landfill sites. Such a reduction of nitrogen input is under way in Jamaica Bay but there is much more work to be accomplished. The restoration of the aquatic ecosystems demand a lot of money and time that the government are reluctant to give, which is why men and women of science must not only put forward a collective effort in studying the patterns & causes of the distribution of organisms and their relationship to their environment, but also form political action committees to push for effective legislation and application of new technologies to reduce nutrient input and enhance restoration of natural communities.
Benotti, M., & Abbene, I. (2007). Nitrogen loading in Jamaica Bay, Long Island, New York, predevelopment to 2005. Reston, Va.: U.S. Geological Survey.
Conley, D., Paerl, H., Howarth, R., Boesch, D., Seitzinger, S., Havens, K., . . . Likens, G. (2009).ECOLOGY: Controlling Eutrophication: Nitrogen and Phosphorus. Science,1014-1015.
Diaz, R., & Rosenberg, R. (2008). Spreading Dead Zones and Consequences for Marine Ecosystems. Science, 926-929.
Holmes, R., Aminot, A., Kérouel, R., Hooker, B., & Peterson, B. (1999). A simple and precise method for measuring ammonium in marine and freshwater ecosystems. Canadian Journal of Fisheries and Aquatic Sciences, 56, 1801-1808.