Impacts of Hurricanes on Phytoplankton Blooms in the Chincoteague Bay

Trudee Jaeger, Department of Biology, York College

Introduction• Due to the climate change, scientists have

predicated increased levels of hurricane intensity. Hurricanes are destructive to the environment with their torrential rainfall and high-velocity winds. These conditions can significantly impact phytoplankton communities.

• Phytoplankton are single-celled organisms which photosynthesize in the ocean. They are the start of the food chain and require plenty of both light and nutrients in order to grow. Often, however, light and nutrients are found in different locations in the water column.

• During the passing of a hurricane, the water column of the bay can mix. This mixing will cause colder, nutrient-rich water on the bottom to be mixed with the warmer nutrient-poor water on top. If the water column restratifies, this can give phytoplankton excess light and nutrients, causing a bloom.

Review of Literature

• They noted that phytoplankton response depended on both the conditions of the storm and the water column beforehand (Wetz and Paerl, 2008).

• The damage to the ecosystem of Pamlico Sound was also much more severe when multiple storms passed in a short period of time (Wetz and Paerl, 2008).

• During the passage of a hurricane, salinity dropped within the bay. The more significant the drop of salinity levels, the larger the noted response of a phytoplankton bloom. They even found a large phytoplankton bloom after a seemingly small hurricane (Wetz and Paerl, 2008).

• Despite this knowledge, there has been minimal research in the relationship between phytoplankton dynamics with the types and magnitudes of storms (Wetz and Paerl, 2008). These findings have not been measured in bays as small as the Chincoteague Bay (of Maryland and Virginia).

• Water stratification is the vertical distribution in water density, dividing the water column.

• Light levels are highest at the surface.

• Nutrient levels increase with depth.

Preliminary Research

• Salinity: As the hurricanes pass the Chincoteague Bay, salinity levels plummet from freshwater rainfall and run-off.

• Temperature: Temperature decreased and then rose again, especially after hurricanes Bonnie and Charley. This may indicate the storms caused mixing of the water column then the water re-stratified, giving phytoplankton access to both excess nutrients and light.

• Chlorophyll: Chlorophyll levels spiked roughly two weeks following hurricane activity which shows the occurrence of a phytoplankton bloom.

Nutrient Data

Figure 1. Temperature, salinity and chlorophyll levels of the Chincoteague Bay, Bishopsville

Prong. Measured roughly one month prior and post Hurricanes Bonnie, Charley and Alex, 2004.

Table 1. levels measured at the University of Maryland Horn Point Laboratory (Technicon AutoAnalyzer II EPA 1979 Method 353.2).

Measurements were observed prior and post storm dates for comparison.

Hurricane Date

Pre-Storm Measurement

Date

Post-Storm Measurement

Date

Change in NO3 levels (mg/ L)

Days Between

Test Dates Hurricane

Alex August 3,

2004 July 24, 2004 September

11, 2004 0.79 – 0.96 49

Hurricane Bonnie

August 13, 2004

July 24, 2004 September 11, 2004

0.79 – 0.96 49

Hurricane Charley

August 14, 2004

July 24, 2004 September 11, 2004

0.79 – 0.96 49

Hurricane Cindy

July 8, 2005

June 11, 2005 August 13, 2005

0.12 – 0.13 63

Hurricane Ernesto

September 1, 2006

August 13, 2006

September 11, 2006

0.09 – 1.19 29

Tropical Storm Hanna

September 7, 2008

August 11, 2008

September 7, 2008

0.33 – 0.14 27

• Nutrient data was collected by volunteers on average once every 28 days in the Chesapeake Bay. These dates did not coincide with storm passage.

• Measurement for post-storm Tropical Storm Hanna was observed the day it hit the bay.

• Measurement dates are too far apart from one another for conclusions to be drawn of storm impact on levels. More data would need to be collected from the bay at a finer time scale

Proposed Hypothesis

Proposed Methods

• Establish a sampling location at Northern, Southern and central regions of the bay. Observe both the top and bottom layers of the water column.

• Automated observations of temperature, salinity and chlorophyll levels with YSI 6600 data loggers every 15 minutes.

• Optical nitrate analyzer - Satlantic SUNA V2 nitrate sensor. Will be on buoy, sampling continuously to increase sampling frequency for nutrients.

• Sampling to be taken for 10 years

• Take a sampling point in Virginia, which has not been historically sampled

• : Impact of a hurricane on phytoplankton growth will not be dependent on the initial conditions within the bay.

• : The passage of a hurricane will increase phytoplankton growth if the water column is stratified within the bay.

• : Levels of phytoplankton will not depend on the number of storms passing per month.

• : Multiple storms will have a larger impact on phytoplankton growth than single storms if the water column is stratified.

Proposed Results

Figure 5. Proposed measurement of chlorophyll levels in the Chincoteague Bay after

a hurricane under differing pre-hurricane stratification conditions. An unpaired t-test

indicated a significant difference (*) between values (p<0.05).

• Phytoplankton levels are expected to significantly increase if the water column is stratified prior to the storm. When the storm passes, mixing occurs which allows phytoplankton to be exposed to higher levels of light and nutrients causing a larger bloom.

Figure 6. Proposed impact of the number of hurricanes passing in a month on subsequent chlorophyll levels in the Chincoteague Bay A

linear regression showed a significant relationship between number of storms and

chlorophyll levels (p<0.05).

• Phytoplankton blooms are expected to increase if there are more hurricanes per month as repeated mixing and runoff result in continued inputs of nutrients to the system.

Importance

Phytoplankton are the start of the food web. When a storm impacts them, the entire bay ecosystem can be affected. Phytoplankton blooms can cause toxicity and hypoxia which would destroy bay life and greatly impact local fisheries.

Works Cited• Hughes, C. (2009). Difficulties in separating hurricane induced effects

from natural benthic succession: Hurricane isabel, a case study from eastern virginia, usa. Estuarine, Coastal and Shelf Science, 85(3), 377-386. Retrieved from http://ac.els-cdn.com/S0272771409003904

• Wetz, M. and Paerl, H. (2008). Estuarine phytoplankton responses to hurricanes and tropical storms with different characteristics (trajectory, rainfall, winds). Estuaries and Coasts, 31(2), 419-429. Retrieved from http://link.springer.com/content/pdf/10

AcknowledgementsI would like to thank Dr. Jessica Nolan for her endless support and

guidance, and extend my gratitude to Joshua Brennan and Emily Springer for statistical advice.

http://www.sciencedirect.com/science/article/pii/S0278434304000810

http://link.springer.com.ezproxy.ycp.edu:8000/article/10.1007%2Fs12237-008-9034-y

• Wetz and Paerl (2008) studied the short-term impacts of five hurricanes, both small and large in scale, in Pamlico Sound, North Carolina.

Figure 2. Original sampling location (Bishopsville Prong) with proposed Northern, Southern and

central sampling locations of the Chincoteague Bay.

Figure 3. YSI 6600 data logger.

Figure 4. Satlantic SUNA V2 nitrate sensor.http://planet-ocean.co.uk/

Bishopsville Prong

Northern Location

Central Location

Southern Location

earth.google.com/

http://mddnr.chesapeakebay.net