After every season, NOAA Chesapeake Bay Office scientists examine observations from CBIBS buoys, satellites, and other data sources to determine how Bay conditions compared with the average over the past 20 years. Once they identify any instances where conditions were different from average, they explore how those anomalies might affect species that live in the Bay.
NCBO has released its 2024 Summer Seasonal Summary. Here’s a quick overview of what it includes. For more detailed information and graphs/figures, check out the full scientific document.
Anomalies
Water Temperature: Scientists reviewed data from satellites to see how surface water temperatures compared to long-term averages in the mainstem and tributaries of the Chesapeake Bay. For much of the Chesapeake Bay, water temperatures were slightly warmer than average. But for the very southern portion of the Bay, from the Rappahannock River to the mouth of the Bay, temperatures were a bit cooler than average.
Data from NOAA satellites shows slightly warmer-than-average water temperatures over much of the Bay for summer 2024.
Scientists also examine data from several CBIBS buoys. This summer, water temperature was above the long-term average at the Annapolis, Gooses Reef, and Potomac CBIBS buoys from early June to mid July. For the remainder of summer water temperatures fluctuated between above, near-normal, and below the long-term average.
Water temperature at the Potomac CBIBS buoy was warmer than average from June through mid-July, then dropped to average and below average through much of August.
Salinity: Salinity was well below average at the Annapolis, Gooses Reef, and Potomac CBIBS buoys from June through early August. This was not expected, because much of the region was experiencing drier-than-normal weather. In early/mid-August, the remnants of Hurricane Debby moved through the region, and its rainfall and resulting freshwater flow into the Bay dropped salinity even more.
Salinity levels at the Annapolis CBIBS buoy were solidly below average for much of the summer.
Precipitation and Freshwater Flow: Rainfall amounts for tidewater Virginia and southern Maryland were among the lowest since 2007. Lower precipitation generally results in low freshwater flow to the Bay. Stream flow gauges did show a few notable spikes throughout the summer, notably corresponding to the passage of the remnants of Hurricane Debby.
Southern Maryland experienced its third-driest summer since 2007.
Dissolved Oxygen: Discussion of dissolved oxygen levels includes both observed data and modeled information at two locations—one in the mid-Bay and one at the mouth of the Potomac River. At the surface, dissolved oxygen levels were generally above average at the mid-Bay location and below to near average at the mouth of the Potomac.
At the bottom in the mid-Bay, levels were below average for the first part of the summer and then improved to above average. But they were still low enough that fish and crabs would potentially avoid the area. At the bottom at the Potomac station, conditions were variable, but still low enough to negatively affect fish and crabs. Dissolved oxygen levels were even lower here than at the mid-Bay bottom—low enough to be damaging to aquatic worms.
Effects on Living Resources
Striped Bass: Water temperatures were above 82.4° F at the Annapolis, Gooses Reef, and Potomac CBIBS buoys from about mid-July to mid-August. Striped bass avoid areas that are this warm. Also, dissolved oxygen at the bottom was below what is suitable for striped bass from June through August. Poor conditions like these can affect the distribution, growth, and survival of striped bass.
Oysters: Oysters spawn more successfully in higher-salinity waters. Because this year had lower-than-average salinity, that may have led to less spawning in the upper Bay. To counter the lower salinity, the University of Maryland Center for Environmental Science’s Horn Point Laboratory Oyster Hatchery on the Choptank River added salt to its water to encourage spawning. One benefit, though: Lower salinity could mean lower amounts of oyster disease.
Blue Crabs: The low dissolved oxygen at the bottom could have affected blue crabs—especially female blue crab migrations to the lower parts of the Bay. Low dissolved oxygen can also make blue crabs move out of the blue crab sanctuary areas, which cover much of the mainstem Bay from the mouth of the Potomac River to the mouth of the Chesapeake Bay. These waters are deeper and more likely to experience low oxygen. When crabs move out of the sanctuary boundaries to find higher dissolved oxygen levels, they are more likely to be harvested.
Red Drum: Red drum—until recent years, a more southern species— have been increasingly targeted and caught by anglers in the Chesapeake Bay. The species may be shifting north as waters warm. A number of anglers reported good catches of red drum this summer. During field research this summer at Poplar Island, NOAA Chesapeake Bay Office scientists recorded the highest number of red drum since work began there in 1995. This may be related to rising water temperatures linked to climate change. Rising water temperatures may be allowing red drum to move further north in their range for longer periods of time.
The number of red drum caught during routine scientific sampling at Poplar Island, Maryland, has increased in recent years.
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 2024 Summer Seasonal Summary.