Springtime showers will result in oxygen-starved water in deep parts of the Chesapeake, at least through the first half of the summer, according to Bay scientists.
High stream flows, along with the nutrients they carry, will likely result in the fourth largest volume of oxygen-depleted water since 1985 in deep portions of the Bay through early summer, according to the annual forecast from a partnership between the University of Maryland Center for Environmental Science and the National Oceanic and Atmospheric Administration.
Freshwater river flows into the Bay were much greater than normal from March through May, according to the U.S. Geological Survey.
Wet conditions typically trigger poor water quality in the Chesapeake as rainfall drives increased amounts of nutrients and sediment into rivers. Nutrients fuel increased algae production; when the algae die and sink to the bottom, they are consumed by bacteria in a process that removes oxygen from the water.
This year, nitrogen from the Susquehanna averaged more than 1.3 million pounds a day in March, more than twice the daily average for the month, according to USGS estimates. Nitrogen loads in April exceeded a million pounds a day, a bit more than twice the normal levels during the month.
In addition to flushing more nutrients into the Bay, strong river flows, especially from the Susquehanna, create a barrier between fresher water on the surface of the Bay, and heavier saltwater on the bottom. This barrier, known as the pycnocline, is particularly strong in spring and early summer and prevents oxygen-starved water on the bottom from mixing with surface waters. As algae on the bottom are consumed by bacteria, oxygen is used up and cannot be replenished, creating a so-called dead zone.
As a result of those factors, the amount of anoxic water in the Bay - water with no oxygen - is worse in high-flow years.
Based on spring flows from the Susquehanna and Potomac rivers and estimated nutrient loads, along with factors such as wind direction and sea-level - which also affect stratification - a team of Bay scientists predict that the first half of the summer, through mid-July, would have the fourth largest volume of anoxic water since Baywide monitoring began in 1985, covering about 2.4 cubic kilometers. That's nearly 5 percent of the mainstem Chesapeake Bay.
The strength of the pycnocline can be greatly influenced during the summer by rainfall, severe storms and wind patterns. Because of those factors, the scientists won't make a prediction about anoxic volume for late summer until mid-July.
Hypoxia - the condition when water contains oxygen at very low levels - afflicts a larger area of the Bay than anoxia. Scientists will not have the information needed to predict the extent of summertime hypoxia until early July.
One thing that could stir up Bay conditions this summer is a hurricane, and NOAA is predicting an active hurricane season for the Atlantic this year. It said this hurricane season, which runs from June 1 through October, has the potential for 12 to 18 named storms in the Atlantic, Caribbean and Gulf of Mexico, of which six to 10 could become hurricanes, including three to six major hurricanes.
The seasonal average is 11 named storms, six hurricanes and two major hurricanes.
The annual Bay summer forecast is made by researchers cooperating with the EcoCheck partnership between UMCES and NOAA's Chesapeake Bay Office.
Updates to the forecast may be found during the summer at the EcoCheck website, www.eco-check.org
High river flows likely to help Chesapeake's striped bass
This spring's high river flows might bring good news for the Bay's striped bass. Juvenile rockfish production should be much better than average this year, according to Ed Martino, a researcher with the National Oceanic and Atmosphere Administration's Cooperative Oxford Laboratory.
Martino bases his prediction on a model that uses springtime river flow and temperature data to predict juvenile rockfish production in Maryland, where the majority of the East Coast striped bass population spawns. The model, he said, can account for more than 70 percent of the annual variability in the number of striped bass juveniles that survive long enough to be "recruited" into the overall stock.
The long-term Maryland striped bass average is 11.6 juvenile per net haul, but Martino said this year's high flows likely set up conditions that will help exceed that number. High flows can expand nursery areas, and spur production of more food for juvenile fish to eat.
If Martino's forecast holds up, it will be good news for fisheries managers as juvenile striped bass production has been below average for the past three years.
The annual Maryland Department of Natural Resources juvenile survey will begin in July and continue through September. In the survey, biologists wade into the water at 22 locations once a month and do two sweeps through the water with a 100-foot seine net, then identify and count the fish caught.
Last year, the average was 5.6 juvenile striped bass per net.