According to the NOAA Chesapeake Bay Office’s Spring 2024 Seasonal Summary, conditions from March through May had good news—but also some bad news—for some of our favorite Chesapeake Bay species. NCBO seasonal summaries include analysis of observations from CBIBS buoys, satellites, and other data sources to determine how Bay conditions compared with the average over the past 20 years. Scientists also discuss how those differences may have affected species that live in the Chesapeake Bay.

Water Temperature

Scientists reviewed data from satellites and CBIBS buoys to see how surface water temperatures compared to long-term averages in the mainstem and tributaries of the Chesapeake Bay. In general, temperatures were warmer than average. The warmer water temperatures may have extended the blue crab growing season. Blue crabs generally emerge from the burrows where they spend the winter when water temperatures reach 50°F. This spring, all buoy locations hit that number by mid-March. Also, warmer temperatures may push the start of striped bass spawning earlier, because they typically begin spawning in the spring when waters reach 60°F. By May 1, water temperatures were above 60°F at the Annapolis, Gooses Reef, and Potomac buoys. These conditions may also have provided more habitat this spring for bay anchovy, because they prefer warmer temperatures. 

Sea surface temperature as observed by NOAA satellites March–May 2024 were warmer than the average for these months in 2007–2024. See the full Spring Seasonal Summary for graphs of water temperature data from the CBIBS buoys.

Salinity

Salinity at the Annapolis, Gooses Reef, and Potomac CBIBS buoys was below average during spring 2024. Blue catfish, an invasive species, can tolerate waters with salinity levels below 14 practical salinity units (PSU). That means this spring, these predatory fish were likely able to thrive in many areas of the Bay while feeding on native species. Salinity also affects the growth, reproduction, and survival of oysters. Oysters grow best in brackish to moderately salty water with a salinity of 10–28 PSU. Oysters produce more young oysters (spat) at higher salinity levels. Salinity below 5 PSU for prolonged periods can cause oysters to die.

Salinity at the Annapolis CBIBS buoy March–May 2024 (blue line) was lower than average at each buoy. See the full Spring Seasonal Summary for graphs of data from other buoy locations.

Precipitation and Freshwater Flow

Parts of Maryland and Virginia experienced high precipitation this spring. Tidewater Virginia had the most precipitation this spring that it had had since 2007: 14.5 inches. Southern Maryland had more precipitation than last year: just under 12 inches. More precipitation (generally in the form of rain in springtime) leads to a higher flow of the water in streams. This improves spawning conditions for striped bass because it increases the area of available habitat. With higher flow, the creeks have a greater volume of water in which fish can spawn.

Precipitation data from 2007–2024 for March–May for Tidewater Virginia. Data from NOAA Centers for Environmental Information.

Precipitation data from 2007–2024 for March–May for southern Maryland. Data from NOAA Centers for Environmental Information.

Hypoxia

Hypoxia is a condition when levels of dissolved oxygen in the water are very low. When nutrient-fueled algae blooms die and decompose, the resulting low-oxygen and hypoxic conditions—known as “dead zones”—can suffocate underwater life and shrink available habitat. This year, hypoxic conditions began in late April. That is earlier than usual. This happened mostly because there was high precipitation and flow, as well as higher temperature and lower winds.

Blue crabs require dissolved oxygen levels of 3mg/L. Larval stages of striped bass may need as much as 6 mg/L of dissolved oxygen. Portions of the Potomac and Choptank rivers that are used for spawning were below 6mg/L by April 22, and part of the main Bay  that includes the blue crab sanctuary was below 3mg/L (Figure 16). These conditions worsened throughout May and may have made it difficult for these animals to live there. 

These maps show how much dissolved oxygen there was in the Bay according to models run by the Virginia Institute of Marine Science. Data from VIMS-CBEFS, Bever (2021)

See More!

For a deeper dive into spring 2024 data, more graphs, and discussion on how conditions may have affected living resources, see the full Spring 2024 Seasonal Summary.