The Background

The Chesapeake Bay watershed is one of the largest in the United States spanning from central New York to Virginia Beach. As is the rest of the world, the Chesapeake Bay is at the whims of climate change. On a macro scale, the changing climate for the Chesapeake Bay watershed will result in an increase in coastal flooding and the submerging of coastal wetlands, an increase in Bay water salinity, an increase in harmful algae, an increase in dead zones, and altered interactions within underwater ecosystems (Najjar, 2000). The Chesapeake Bay has a profound impact on the 17 million people who live within its watershed (National Wildlife Foundation). Much of coastal Maryland uses the waters of the Chesapeake to fish and crab, and the Bay itself is the host of many recreational activities including boating, swimming and sailing. Within the watershed as a whole, nearly 75% of inhabitants get their drinking water either from the bay itself or from a river or stream that will flow into the bay (Solyst, 2021). For all of these important uses, Bay health is crucial to the livelihood of millions on the East Coast of the United states. The current health of the Chesapeake bay is very much in the hands of the inhabitants of the Chesapeake. Unhealthy practices at home will lead to pollution that will run off into the Chesapeake, and unhealthy business practices can be very harmful to Bay Health overall. Throughout the course of this study I hope to explore current polluters of the Bay and look at their direct impacts on Bay Health, as well as offer solutions for the health of the Chesapeake Bay going forward.

Land Segments and Pollution Point Sources

The first map below shows two layers; the first being the Phase 6 Land-River Segments of the Chesapeake Bay. Phase 6 Land-River Segments represent the combination of land segments, which are primarily based on county boundaries, and river segments, which represent watershed boundaries (Maryland Department of the Environment). In my map, I chose to display the 6 major basins which flow into the Chesapeake Bay. The river basins start in the middle of Virginia with the James River Basin and span as high as the middle of New York with the Susquehanna River Basin. To understand differences in water qualities at different parts of the bay, it is important to know where that water is flowing from. The phase 6 data layer comes from USGS and I manipulated it so that it showed by using different colors, the different major basins of the chesapeake bay. The second layer, visible as black dots, shows different major polluting sources of the Bay. When you click on one of these black dots, it tells you a variety of information including the name of the facility, the Basin which the facility falls within, and the type of waste the facility is producing, whether it be municipal or industrial waste. The concentration of these waste producing facilities is noticeably higher within some Basins as it is in others. Noticeably, within the northeast of the potomac basin in comparison to the Susquehanna river basin. This facility point dataset came from the Chesapeake Bay Program, which is a regional partnership that works to meet the agreed upon goals of the Chesapeake Bay Watershed agreement. The Chesapeake Bay watershed agreement is an inclusive, goal-oriented document that addresses emerging environmental concerns and aligns federal directives with state and local goals to work towards the creation of a healthy Bay (Chesapeake Progress, 2022). This dataset was initially very large, but I had cleaning to do to remove unwanted columns. At the end, the columns that remained were the polluting facility’s name, which Basin it was in, the discharge type, the FIPS number, state, and county.

Oxygen, Underwater?

Just like humans on land, underwater plants and animals also need oxygen to survive. Oxygen from the atmosphere dissolves in river and lake water, and it is this same oxygen that fish and aquatic animals breathe. In a polluted water way there may be a dangerously high level of oxygen which bacteria will quickly consume and overpopulate, ultimately leaving the water oxygen deficient . This lack of oxygen in the water can cause aquatic life to suffocate and die. Dissolved oxygen is a good indicator of water health. A healthy waterway will typically have dissolved oxygen concentrations of about 6.5-8 mg/L (Environmental Protection Agency, 2020). Through the process of oxygen uptake, fish expend energy on both locomotion as well as ventilation. These costs along with the risk of predation, vary according to oxygen availability and the type of behavioral response shown. The main changes in behavioral response of fish due to reduced availability of dissolved oxygen are; changes in activity, increased use of air breathing, increased use of aquatic surface respiration, and vertical or horizontal habitat changes (Kramer, 1987). One unfortunate phenomenon that is occurring in the Chesapeake bay is called anoxia, which is a state of total oxygen deprivation. Anoxia occurs in deep waters of the central Chesapeake Bay and currently extends from Baltimore to the mouth of the Potomac estuary. This condition encompasses 5 billion cubic meters of water and lasts from May to September (Officer, 2014). The Chesapeake Bay anoxia appears to have had significant ecological effects on many marine species, including several of economic importance.

Dissolved O2 Levels of Chesapeake Bay

The map below shows the different concentrations of dissolved oxygen in the Chesapeake bay. These readings take place at water monitoring stations in the Bay and are indicators of where water is healthy and can support aquatic life, or is dangerous to aquatic life. The color gradient shows the mg/L of dissolved oxygen, the darker colors representing higher concentrations of dissolved oxygen. Each of these readings come from the same depth of 2.5 meters as to where they were taken because different depths of water will have different oxygen concentrations. This dataset also came from the Chesapeake Bay Program. To process this dataset into one that is compatible to show on a map, I used the st_as_sf function to use the already existing longitude and latitude coordinates to convert it to a spatial feature and set the coordinate reference system to “4326” which is represents the spatial data of the earth’s surface using longitude and latitude.

At different parts of the year, the bay will act differently due to a number of different factors; namely, precipitation and temperature. One key seasonal difference of the bay is that summer grazing of primary producers by zooplankton is greatly reduced due to top, down control of zooplankton by sea nettles. Some of the ungrazed phytoplankton is left to fuel the activities of the microbial community, and the remainder falls to the bottom where it augments the deposit, feeding the blue crabs (Baird, 1989). There is a dominant seasonal cycle in the activities of all subcommunities, which is greatest in the summer and least in the cold season.

Dissolved O2 over time at one water quality monitoring station

Over time, the levels of dissolved oxygen in the Chesapeake Bay have changed. Sometimes even within the timespan of one year, natural events including precipitation, storms, and weather events lead to the concentration of oxygen to change in the water. Colder water will typically have more oxygen than does warm water because in warm water oxygen molecules are moving around faster and will more frequently escape than in colder water (Water Science School, 2018).

Conclusions

Protecting the Chesapeake Bay is essential to preserving the natural beauty and resources of the region. The Bay is home to a variety of wildlife, including fish, crabs, oysters, and more. It also provides us with a source of fresh, clean water that is essential for drinking, recreation, and industry. Without its protection, the Bay could be damaged by pollution, unsustainable fishing practices, and other human activities. Preserving the Chesapeake Bay is also important for its cultural value. The Bay has been home to Native American tribes for centuries, and has been a key part of their culture and identity. The Bay also has a rich history of trade, migration, and exploration. By protecting the Bay, we can ensure that these stories and cultures can be shared with generations to come. As seen throughout the course of the study, our polluting actions, specifically in industry, have direct impacts on the water quality of the Chesapeake Bay, and our continued pollution will lead to more “dead zones” of anoxia. It is possible that we reverse these effects, but it is crucial that we start now.

Link to R Script here

Citations:

Baird, D. and Ulanowicz, R.E. (1989), The Seasonal Dynamics of The Chesapeake Bay Ecosystem. Ecological Monographs, 59: 329-364. https://doi.org/10.2307/1943071

Charles B. Officer, Walter R. Boynton, Chesapeake Bay Anoxia: Origin, Development, and Significance, Journal Article, 2014, Science, 22-27, 223, 4631 , 10.1126/science.223.4631.22 [doi] 4099 - https://www.science.org/doi/abs/10.1126/science.223.4631.22

Chesapeake Progress. “Vision.” Chesapeake Progress, https://www.chesapeakeprogress.com/vision#:~:text=The%20Chesapeake%20Bay%20Watershed%20Agreement,to%20create%20a%20healthy%20Bay.

Kramer, D.L. Dissolved oxygen and fish behavior. Environ Biol Fish 18, 81–92 (1987). https://doi.org/10.1007/BF00002597

Maryland Department of the environment. “Map of Maryland’s Chesapeake Bay Land-River Segments - Phase 6.” Department of the Environment, https://mde.maryland.gov/programs/water/TMDL/DataCenter/Pages/CBLandRiverSegments.aspx.

Raymond G. Najjar, Christopher R. Pyke, Mary Beth Adams, Denise Breitburg, Carl Hershner, Michael Kemp, Robert Howarth, Margaret R. Mulholland, Michael Paolisso, David Secor, Kevin Sellner, Denice Wardrop, Robert Wood, Potential climate-change impacts on the Chesapeake Bay, Estuarine, Coastal and Shelf Science, Volume 86, Issue 1, 2010, Pages 1-20, ISSN 0272-7714, https://doi.org/10.1016/j.ecss.2009.09.026.

Solyst, Jake. “Tap into a Chesapeake Drinking Water Lesson.” Chesapeake Bay Program, https://www.chesapeakebay.net/news/blog/tap-into-a-chesapeake-drinking-water-lesson#:~:text=There%20are%20more%20than%2018,New%20York%2C%20Pennsylvania%20and%20Maryland.

Thomas A. Burke, Jill S. Litt, Mary A. Fox, Linking Public Health and the Health of the Chesapeake Bay, Environmental Research, Volume 82, Issue 2, 2000, Pages 143-149, ISSN 013-9351, https://doi.org/10.1006/enrs.1999.3982.

U.S. E.P.A. Dissolved Oxygen and Biochemical Oxygen Demand. http://water.epa.gov/type/rsl/monitoring/vms52.cfm

Water Science School. “Dissolved Oxygen and Water Completed.” Dissolved Oxygen and Water | U.S. Geological Survey, https://www.usgs.gov/special-topics/water-science-school/science/dissolved-oxygen-and-water#:~:text=Cold%20water%20can%20hold%20more,oxygen%20concentration%20is%20often%20lower.