Raritan Bay started turning brown after the sunny Palm Sunday weekend, the day before it rained on Tuesday the fifteenth. It's still brown. That's probably an algae bloom.
There are plenty of nutrients in the bay from stormwater and sewage, so all it takes is a few sunny days. According to the USGS gage at Keansburg, the water temperature in the Bay rose about 8o F from April 11th to the 14th before it dropped. The temperature today has risen to where it was on the 14th, in the high fifties.
Phytoplankton in Raritan Bay
According to these reports from the NJDEP and the Monmouth County Health Department, as well as the 1984 report, “ Nutrients, hydrography, and their relationship to phytoflagellates in the Hudson-Raritan Estuary”, some algae commonly return to the Bay every year. Here are a few:
Dactyliosolen fragilissimus, synonym: Rhizosolenia fragilissima
Skeletonema species, e.g. Skeletonema costatum
Heterocapsa species, e.g. H. rotundatum, synonym: Katodinium rotundatum
Heterosigma akashiwo, synonym: Olisthodiscus luteus
Prorocentrum micans, synonym: Prorocentrum redfieldi
Harmful Algal Blooms in Raritan Bay
The diatom Pseudonitzschia seriata is considered toxic and is found in most coastal and estuarine waters on the Atlantic coast. It has been identified in the Bay but not at concentrations that would threaten human health, according to the NJDEP. The same report notes that the Katodinium and Prorocentrum species associated with “red tide” that are common to Raritan Bay are not acutely toxic.
Unlike most large estuaries, Raritan Bay does not have a signature toxic algae, so far; just nuisance blooms. The NJDEP sums it up this way: “Harmful algal blooms may contribute to hypoxia or other negative ecological impacts, but it is important to point out that there are few cases on record of acute human toxicity from phytoplankton in New Jersey waters with some exceptions of moderate bather discomfort and/or illness reported from specific blooms ... It is also important to keep in mind that many incidents of human health complaints (e.g., bather complaints) are not reported and there are few systematic cause/effect studies conducted to assess the ecological consequences of algal blooms.”
There are exceptions - like the one-time, massive die-off of marine life in 1976 off the NJ coast caused by the explosive growth of a normally insignificant species of algae, Ceratium tripos. Worth reading about, on page 13 of this report in the section “1976”.
Diatoms respond rapidly to episodic high-light, high-nutrient pulses. That happened in May of 2007, when there was an extensive bloom of the diatom D. fragilissimus after the water temperature in Raritan Bay rose 20o F in one week.
Diatoms grow very rapidly and have short lifetimes. Blooms “seed” in the shallow waters of the tidal creeks that feed the Bay. Besides nitrogen and phosphorous, diatoms require dissolved silica. Silicon is found in quartz, sand, silt, clay, and glauconite, which is an iron-silicate mineral common to Monmouth County.
The NJ Bayshore’s muddy shoreline is predominantly shaped by runoff from the Raritan River, not the Hudson River, which is silica-poor. The Raritan is also the major source of nitrate, according to the 1962 report, “Environmental Characteristics of Raritan Bay, A Polluted Estuary.”
A paper on silicon and marine eutrophication observes that “In temperate latitudes, silicon in the form of dissolved silicate is usually supplied in plentiful amounts through land weathering to the estuarine and coastal zones.” In other words, stormwater runoff.
In the San Francisco Bay Estuary, blooms happened during moderate flows when there was increasing sunlight. During storms, diatoms were swept out to sea; during the summer drought, diatoms sank to the bottom.
If a bloom grows large enough, the algae will use up all the oxygen in the water and die, producing the signature foaming, scum lines and hydrogen sulfide odor that is often mistaken for sewage.
Links For Bloom-Watching
WATER TEMPERATURE: USGS RARITAN BAY AT KEANSBURG http://waterdata.usgs.gov/usa/nwis/uv?site_no=01407081
SUNLIGHT: EPA – UV INDEX http://epa.gov/sunwise/uvindex.html
RAIN: RUTGERS DAILY WEATHER DATA http://climate.rutgers.edu/njwxnet/dataviewer-stnpt.php
CURRENTS: STEVENS URBAN OCEAN OBSERVATORY AT THE CENTER FOR MARITIME SYSTEMS http://hudson.dl.stevens-tech.edu
TIDES: STEVENS’ STORM SURGE DATA FROM SANDY HOOK http://hudson.dl.stevens-tech.edu/SSWS/
During the Summer
NJDEP CHLORAPHYLL A (graphic flyover reports) http://njdep.marine.rutgers.edu/aircraft/
EPA FLYOVER AND NJDEP ALGAE REPORTS (weekly) http://www.harborestuary.org/surveys.htm
NJDEP BEACH REPORTS www.NJBeaches.org
Cloern, J. and Dufford, R. 2005. Phytoplankton community ecology: principles applied in San Francisco Bay. Marine Ecology Progress Series. Vol. 285: 11-28. http://sfbay.wr.usgs.gov/publications/pdf/cloern_2005_phytoplankton_ecology.pdf
Draxler, A., Waldhauer, R., Matte, A. and Mahoney, J. 1984. Nutrients, hydrography, and their relationship to phytoflagellates in the Hudson-Raritan Estuary. Bulletin NJ Acad Sci. Vol. 29, No.2 pp. 97-120.
Eilertsen, H., Sandberg, S. and Toileisen, H. 1995. Photoperiodic control of diatom spore growth: a theory to explain the onset of phytoplankton blooms. Marine Ecology Progress Series. Vol 116; 303- http://www.int-res.com/articles/meps/116/m116p303.pdf
Gastrich, M. 2000. Harmful algal blooms in coastal waters of NJ. NJDEP. DSRT. http://www.state.nj.us/dep/dsr/coastal/hab2.PDF
Jeffries, H. 1962. “Environmental Characteristics of Raritan Bay, A Polluted Estuary.” Narragansett Marine Laboratory. No. 35. Rhode Island. http://m.aslo.net/lo/toc/vol_7/issue_1/0021.pdf
Officer, C. and Ryther, J. 1980. The possible importance of silicon in marine eutrophication. Marine Ecology Progress Series. Vol 3; 83-91. http://www.int-res.com/articles/meps/3/m003p083.pdf
Steimle, F. and Caracciolo-Ward, J. 1989. A reassessment of the status of the benthic macrofauna of the Raritan Estuary. Estuaries. Vol112, No. 3, p. 145-156. http://link.springer.com/article/10.2307%2F1351819#page-1