Harmful Algal Blooms – Part 1: Who Cares About Harmful Algal Blooms?

It’s a beautiful day in Virginia. The sun is shining, the birds are singing and the water is a beautiful shade of brownish green…

Harmful Algal Bloom
Source: Chesapeake Bay Foundation

The “lovely” color of the water is a harmful algal bloom. An algal bloom is an overgrowth of phytoplankton –  tiny, photosynthetic organisms that live in the water. A harmful algal bloom or HAB is an algal bloom that has some kind of negative effect on other organisms.

In Virginia, harmful algal blooms occur between May and September when the water is warm and full of nutrients like phosphorous and nitrogen – the same nutrients used to fertilize plants. Some of these nutrients come from industry and sewage treatment, but many nutrients are washed into the water when rain falls on farms and yards.  Warm, wet summers are great for plants and for harmful algal blooms.

Algal blooms discolor the water and produce noxious odors. They also block the sunlight that is needed by underwater plants and keep filter feeders like oyster from being able to obtain food. When the phytoplankton die and decompose, they remove large quantities of dissolved oxygen from the water and create anoxic dead zones. The result is massive fish kills because fish, oysters, clams, crabs, and other organisms can’t get the oxygen they need.

Source: Chesapeake Bay Foundaton
Source: Chesapeake Bay Foundation

Scientists in Virginia are especially concerned about two species: Cochlodinium polykrikoides and Alexandrium monilatum. Cochlodinium polykrikoides is native to Virginia. Alexandrium monilatum is an invasive species that wasn’t found north of Florida until 2007. It now occurs regularly in Virginia’s rivers.

Both these species produce red tides, like the bloom in the picture below. They also produce toxins that can kill fish and cause birth defects in shellfish. These toxins may also cause illness in humans.

Image from Virginia Institute of Marine Science (VIMS)
Source: Virginia Institute of Marine Science (VIMS)

HABs are a public health problem. They are also an economic problem because a large bloom can have a big impact on Virginia’s fishing industry and tourist industry. So, Virginia has a Harmful Algal Bloom Task Force. The task force includes representatives from the Virginia Institute of Marine Science (VIMS), the Marine Resource Commission, the Department of Environmental Quality (DEQ), Old Dominion University (ODU) and the Virginia Department of Health. These agencies work together to monitor Virginia’s waters for harmful algal blooms and to respond to bloom events. VIMS and ODU do research on harmful algal bloom species and the biological and environmental conditions that contribute to bloom growth.

Virginia Harmful Algal Bloom Surveillance Map 

But, harmful algal blooms aren’t unique to Virginia. Large blooms and dead zones have also been recorded in the Great Lakes, the Gulf of Mexico, the St. Lawrence Estuary, the Oregon Coast, Monterey Bay, the Baltic Sea and Florida. The total economic impact of harmful algal blooms in the U.S. is estimated at $100 million per year.

Last year, Congress reauthorized and expanded the Harmful Algal Blooms and Hypoxia Research and Control Act of 1998. This act provides funding for the study and monitoring of HABs in U.S. waters.

As climate change causes waters to warm, harmful algal blooms are expected to increase in both frequency and severity. More and more water will be affected. So, who cares about harmful algal blooms? We all should care.

Next week: Harmful Algal Blooms – Part 2: Monitoring Harmful Algal Blooms

Edited on 11/20 to add map.

How Safe Are You? Mapping Disasters

The assignment is take someone else’s map and modify it. I was assigned Asha Katti’s map of wildfire-prone areas in the U.S.


Here is the link to Asha’s map.

Asha is concerned with how wildfires affect people. The other layers on her map include 2014 USA population density and 2009 USA social vulnerability.

Fires aren’t the only natural disasters that impact American lives. When the 1999 Loma Prieta earthquake struck the Bay Area, I was working at a social service agency in Berkeley. The earthquake left thousands of people homeless and jobless. I learned how easily a person’s life can be disrupted by an unexpected event. But, it doesn’t take an earthquake.

It’s been three years since Hurricane Sandy. The category 2 storm flooded neighborhoods along the East Coast. The worst damage was in New York and New Jersey. And, people are still recovering from Sandy’s effects.

So, I amended the map to show the risk of all natural disasters that have a potential major impact on American lives: volcanoes, earthquakes, hurricanes, tsunamis,n floods, tornadoes and wildfires.  Did I leave anything out? Zombie outbreak?

This is Asha’s fire layer in Northern Virginia, where I live. Although we do have wildfire warning days in the summer, our overall risk of fire is low to very low (green and light green).

(Clicking on any of the maps below should take you to esri’s more interactive map viewer, so you can look at your neighborhood.)


While I haven’t experienced a wildfire in Virginia, flooding occurs regularly. The area in purple is the 100 year flood zone. This is the area that has a 1 percent chance of flooding in any given year. The yellows show population density.


Floods in Virginia can be the results of hurricanes. We have a moderately high hurricane risk (orange). This is the same risk as New Jersey.


The other severe weather threat that we worry about is tornadoes.


However, we are less likely to have tornadoes in Virginia than in many other parts of the country.


What about geological disasters? While we do have earthquakes in Virginia, our overall earthquake risk is very low, especially compared to earthquake risk on the West Coast. On the map, light areas indicate low risk while dark areas indicate high risk.


This map of the West Coast shows earthquake and volcanoes. Volcanoes aren’t a risk in Virginia (or most of the United States), but there are active (red) and potentially active (blue) volcanoes in Washington, Oregon and Northern California.  Recent earthquakes are shown as smaller dots. The red markings on the coast are tsunami risk areas.


A natural disaster can change a life without any warning. So, how safe are you?

Where Will I Put the Bottled Water?

When we were in class on Wednesday night, Hurricane Joaquin seemed to be headed straight for Virginia. I’m pretty well prepared, but I donated last year’s bottled water stash in the spring. So, on Thursday morning, I stopped at Target to stock up on bottled water which is now sitting in the hallway because I don’t have space for it.

The latest forecasts show that I didn’t really need to rush and buy water; Joaquin isn’t likely to reach the East Coast. But, thoughts of hurricanes inspired a map.


I mapped esri’s active hurricanes and recent hurricanes as well as hurricane tracks from historic hurricanes (in blue, from Maps.com) on top of a base map. Hurricane Joaquin’s path is shown in black, while the yellow dots represent the tracks of recent hurricanes. As you can see, we might be safe from Hurricane Joaquin, but (historically speaking) it’s only a matter of time until a hurricane does hit Virginia.

You can see the ArcGIS Online map here.

I think I’ll keep the water.