Dissolved Oxygen) in the Bay’S Mainstem And; 4) Unusually Clear Water and Abundant Aquatic Plant Occurrence in the Upper Bay

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hesapeake Unusual summer conditions in upper Bay C ate Last summer, upper Chesapeake Bay had unusually clear Macroalgae Upd Water Quality 2004 water, abundant submerged aquatic vegetation (SAV) cover, This summer extensive blooms of macroalgae were reported in the This is the first in a series of newsletters to be produced by the Monitoring and Analysis Subcommittee (MASC). MASC elevated macroalgae distribution and localized occurrence of dark upper Bay, covering a 20-mile region. Large blooms of macroalgae are Issue 1 coordinates and supports the monitoring activities of the Chesapeake Bay Program (CBP). Newsletters produced by false mussels. Here we summarize the observations and pose an not typically observed in Chesapeake Bay, with any occurrence normally Jan 05 explanation as to why the conditions occurred. restricted to small, localized patches. The predominant macroalgae MASC will summarize current and significant issues relating to the health of Chesapeake Bay ecosystems, those factors Water clarity present were Cladophora and Rhizoclonium, both green macroalgae. that affect the health of the Bay, and the restoration effort. From June to August 2004, many monitoring stations in the The cyanobacterium Lyngbya was also Macroalgae This newsletter summarizes four important water quality events that affected Chesapeake Bay during 2004. These being: 1) a large turbidity plume in on SAV upper Chesapeake Bay had water clarities at or above the 20-year locally abundant. The bloom fouled crab (MD DNR) the Bay’s mainstem due to the remnants of Hurricane Ivan; 2) The worst harmful algal bloom within the Potomac River for 20 years; 3) A large volume of average for this time of year, with many stations recording record pots and gill nets, forcing watermen anoxic water (no dissolved oxygen) in the Bay’s mainstem and; 4) Unusually clear water and abundant aquatic plant occurrence in the upper Bay. clarities. This is particularly unusual given that river fl ow during the to reduce fi shing effort or move farther summer was consistent with the long-term average and that high south to unimpacted areas. Hurricane Ivan leads to record September river fl ow fl ow rates occurred in the previous year. Mussels The dark false mussel (Mytilopsis Key A. River discharge into Chesapeake Bay River (54%), with the Potomac and James Abundant submerged leucophaeta) is one of several mussel Susquehanna River aquatic vegetation reported during the fi rst six months of 2004 was mouth Rivers being responsible for 19% and 11%, Susquehanna River species native to the Chesapeake Bay, mouth Abundant macroalgae Dark false consistent with the long-term average respectively. reported though not typically considered common mussels (1940s to 2002). However, in September, the The record September discharge also Abundant dark false or abundant. The mussel is small (typically (NOAA) mussels reported remnants of Hurricane Ivan dumped up to follows two years of extreme river fl ow, with Water clarity (June–August): less than one inch or 2.5 cm), attaches 13 inches of rain onto the Chesapeake Bay Sediment plume in very low fl ow in 2002 and high fl ow in 2003. Below average itself to rocks or other hard substrate, and prefers lower salinity waters. watershed leading to record river discharge Chesapeake Bay River fl ow into Chesapeake Bay accounts for Above average During summer 2004, greater than normal abundances of this mussel were Clearest recorded and subsequently very large loads of nutrients approximately 62% of the nitrogen and the observed in the South River, Bear Creek (Patapsco River) and upper Severn and sediments being delivered to the Bay. majority of sediment delivered to the Bay. River. However, the Magothy River was the primary area for a large population Ivan was a category four hurricane that made Bay Bridge Consequently, the quality of the Bay’s water of the mussel extending from the headwater creeks to the mouth. Baltimore landfall early in the morning of September 16 and the health of the Bay’s fl ora and fauna Why are we seeing these conditions? between Mobile, Alabama and Pensacola, Sediment are strongly infl uenced by river fl ow. There has been a slow increase in upper Bay SAV populations over plume Florida. The remnants of the hurricane moved Elevated river fl ow over the past two the past 10–12 years. This has probably been the result of gradually in Potomac northwards to the Appalachian Mountains River Extent of plume years has contributed to a large harmful Chester decreasing amounts of suspended sediments in this portion of the Bay. during satellite River and merged with a cold front on September overpass algal bloom in the Potomac River and low Then, during the spring of 2004, upper Bay water temperatures rose 17, resulting in the record rainfall. dissolved oxygen levels in the Chesapeake Bay 0 5 miles to a 20-year high due to an unusually hot May. This warm water may Bridge B. Consistent with the long-term average, Bay mainstem. Contrary to these negative

r have allowed SAV and macroalgae populations to get an early start on er er be

Month (2004) r impacts, water clarity in the northern region

y approximately half of the water ﬂ owing mb mb st h be em the growing season enabling the beds to not only survive, but to trap l y rc to ve ce ri ne ly nuar of the Bay reached record levels this summer,

ugu ept into the Bay came from the Susquehanna ebruary No Ju Ju De Ma Oc Ja F Ma A S 0 Ap sediments and nutrients, maintaining high water clarity during the early Minimumumum before the effects of Hurricane Ivan. This m)h: summer. Filtration by the dark false mussels may also have increased James River 0.5 Between James River dept and Potomac River newsletter summarizes these three events. i Average water clarity in localized areas. ch 1 (1985-2003) ec Summer: 1990s to 2003 Summer: 2004 1.5 Potomac River

arity (S River Input Monitoring cl 2 Chesapeakehesapeake BayBay onon 2222 SeptemberSeptember 20042004 shortlyshortly Record July clarity Maximumm stations

Water 2.5 Hurricane Ivan after the heavy rains caused by the remnants of Record August clarity turbidity plume Between Potomac River Hurricane Ivan. Image shows a large sediment River ﬂ ow, pollutant concentration and load and Susquehanna River Susquehanna River A) Upper Chesapeake Bay summer water clarity and occurrences of plume from the Susquehanna River extending monitoring is conducted by the River Input macroalgae, dark false mussels and submerged aquatic vegetation. Relative inﬂ ow of water into Chesapeake Bay south into the central reaches of the Bay. Monitoring (RIM) program, a collaboration B) Secchi depth at upper Chesapeake mainstem site (Turkey(Turkey Point: during 2004. (SourceSource: NASA MODIS/Terra.) between United States Geological Survey, CB2.1). (Source: Maryland Department of Natural Resources.) Virginia Department of Environmental Key to symbols 160,000 Wet year Quality and Maryland Department of Temperature Water clarity Light penetration Dark false mussels Resuspension of Dry year 140,000 th th

Submerged aquatic vegetation difference (Secchi depth) depth attached to structure particulate matter ) 25 to 75 percentile Natural Resources. There are nine RIM -1 Average s 120,000 An abundance of submerged aquatic vegetation beds was Submerged stations in the Chesapeake watershed, aquatic Floating Particulate filtration Mixed macroalgae 100,000 reported in the upper Bay this year by the local community. In some vegetation macroalgae by mussels measuring 80,000 instances it was reported in areas where little or none had been Conceptual diagram comparing the upper Bay during the summer of 2004 to approximately 60,000 observed in the recent past (e.g., Baltimore Harbor basin on the that of more recent summers. (cubic feet 93% of river 40,000 Patapsco River). Species and density shifts within existing beds ﬂ ow into the

Annual average discharge 20,000 may be producing greater coverage and increased diversity of Further information on the unusual conditions in the upper Bay can be found at: Bay. Over the http://www.dnr.state.md.us/bay/index.html 0 next few years, native species. 1940 1950 1960 1970 1980 1990 2000 Year the number Remnants of of monitoring This newsletter was the initiative of the Tidal Monitoring and Analysis Workgroup (TMAW). TMAW is responsible for the Chesapeake 200,000 Hurricane Ivan stations is Bay Program’s (CBP) tidal water quality and biomonitoring programs. The Workgroup coordinates and integrates the State- and Federally- ) 160,000 expanding to funded monitoring programs within the tidal monitoring network, promoting consistency in sample collection and analysis, data management -1 s and reporting. The data collection programs provide quantitative information on a suite of physical and chemical water quality parameters, 120,000 2004 75th percentile obtain better as well as certain biological parameters. estimates of 80,000 Average Current TMAW members and their afﬁ liations: loads entering (cubic feet 40,000 the bay 25th percentile from coastal 0 Monthly average discharge Location of River Input watersheds. Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Monitoring stations. Newsletter prepared by: Month Ben Longstaff (NOAA-UMCES Partnership) River discharge rates into Chesapeake Bay over the past 60 years (top) and during 2004 (bottom). on behalf of TMAW members The past six years are characterized by two years of higher than average discharge (highlighted Further information on river ﬂ ow can be found by thicker bars) preceded by four years of lower than average discharge. The elevated discharge at the US Geological Survey website: in 2004 was largely attributable to September rainfall from Hurricane Ivan. (Source: United States http://va.water.usgs.gov/chesbay/RIMP/index.html Geological Survey.) Potomac River experiences worst harmful algal bloom in 20 years Dissolved oxygen: Large anoxic zone during summer

Last summer, the Potomac River the estuary was affected. The bloom mostly Once again, large areas of Volume of Bay mainstem waters experiencing hypoxic and anoxic average between March and July, then experienced the worst harmful algal bloom consisted of the cyanobacterium (blue-green Chesapeake Bay experienced low conditions this summer. Anoxia was above average during June dropped below the long-term average (HAB) in 20 years. The bloom started at algae) Microcystis aeruginosa, a common dissolved oxygen levels in 2004. and July. Hypoxia and anoxia were below average during August in August and September. The rapid and September. (Source: Chesapeake Bay Program.) Mattawoman Creek and rapidly spread species that typically blooms in summer Lowest oxygen levels occurred in decrease in the volume of hypoxic throughout the middle reaches of the within the fresh and low salinity portions of the deep waters of the central Bay and anoxic waters in August may be estuary. the Chesapeake Bay. region where strong stratiﬁ cation attributable to a wind-driven mixing -1 event three days before the sampling At the peak of the bloom in late July Analyses revealed that the bloom limited exchange between oxygen 30 Volume of hypoxic and anoxic water (<5 mg l dissolved oxygen) cruise. through early August, a 45-mile stretch of consisted of a toxic strain of the cyanobacterium. depleted bottom waters and oxygen 25 -1 When high cell counts (>10,000 cells ml ) rich surface waters. The volume of Maximum Despite large amounts of nutrients 20 and toxin levels (microcystin levels >3 parts anoxic water (less than 0.2 mg l-1) 2004 and organic matter entering the Bay Miles per billion) were recorded at Colonial Beach, was worse than normal during June 15 during high ﬂ ow conditions in 2003,

) the volume of hypoxic water remained the shoreline was closed for several days to and July 2004, with the volumes 3 10 Average Microscopic views of Microcystis aeruginosa. (1985-2002) water-related recreational activities. While recorded being signiﬁ cantly larger at or below the long-term average. Cells 3-4.5 μm diameter. (Source: Department of 5 Minimum the Potomac River has been experiencing than the long-term average. During Why the volume of hypoxic water Biological Sciences, Old Dominion University.) 0 harmful algal blooms in this region for many August and September, anoxic did not increase, but the volume of -1 years (records of HABs in the Potomac date conditions rapidly diminished, 8 Volume of anoxic water (<0.2 mg l dissolved oxygen) anoxic water increased, is still being back to the 1960s), the blooms in the past two 7 investigated. with volumes below the long-term 6 years have been the largest since 1984. average recorded. The volume lume of Bay mainstem (km Vo 5 Maximum Further information on dissolved oxygen of Chesapeake Bay experiencing 4 levels in the Bay can be found at the 120 Microcystis bloom intensity 3 Mattawoman Creek hypoxic and anoxic conditions 20042004 following websites: 100 (dissolved oxygen levels below 5 mg 2 http://www.chesapeakebay.net/wquality.htm 80 -1 1 Average *1000) l , levels which are stressful or lethal http://eyesonthebay.net -1 Minimum (1985-2002) 60 0 for many ﬁ sh species) was close to Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 40 2004 Month (cells ml 20 erage annual cell density No bloom No bloom Av 0 Early summer Mid summer Late summer -1

Chlorophyll a concentration (μg l ) 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 Year Potomac River Bloom intensity over the past Bloom density and duration (opposite Mattawoman Creek) 20 years (above) and during 1,400 1,200 2004 (right). Bloom intensity *1000) -1 Surface water chlorophyll a concentrations expressed as the number of 1,000 in the upper reaches of the Potomac River cells recorded in a milliliter of 800 illustrate the distribution and intensity of the surface sample water. Note: 600 bloom during its peak. Note: during blooms, no blooms were recorded 400 surface water chlorophyll a concentrations in 1986 and 2002. (Source: 200 can be signiﬁ cantly higher than the underlying Cell density (cells ml 0 Maryland Department of Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec water body. (Source: Morgan State University Natural Resources.) Estuarine Research Center.). Month (2004) Spatial interpolation of dissolved oxygen levels in Chesapeake Bay mainstem during the summer of 2004. Mainstem and tributary interpolation based on ~144 sites, mainstem only interpolation based on 44 sites. There are at least ﬁ ve depths per site. Sample cruises conducted over 4 to 15 day Why was the bloom so severe? periods. (Source: Chesapeake Bay Program.) What causes dissolved oxygen levels to change? This year’s record harmful algal bloom in the Potomac River is attributable to a combination of three factors leading to ideal bloom conditions: Dissolved oxygen (DO) levels in the bottom waters at monitoring a) Elevated nutrient availability due to high river flow rates in 2003, Dissolved oxygen site CB3.3 (opposite Chesapeake Bay bridge) during 2003- Maximum

) 04 illustrate the highly variable nature of Bay DO levels. During -1 b) Warmer than average May 2004 surface water temperatures, l -1 c) Less than average cloud cover in May 2004 leading to greater light availability. Average this period DO levels ranged between 0.2 and 10 mg l . Many Minimum months were below the long-term average and rapid ﬂ uctuations

That an equally large HAB did not occur in 2003, despite elevated nutrient availability from Dissolved occurred. This ﬁ gure illustrates how water temperature (coupled increased flow conditions, may be attributable to less favorable water temperatures and light oxygen (mg with sunlight), river discharge and wind events affect DO levels. o availability. Average water temperature in May 2003 was 2 C less than the long-term average The conceptual diagram illustrates the interaction of these and Water temperature

and cloud cover was 18% greater. C) other factors on DO levels. o ( a) Average spring b) Average May water c) Average May flow temperature cloud cover Sources: a) River ﬂ ow: mperature Average United States Geological Te *1000) Long-term average Survey Potomac River -1 C) ) s o River discharge ( (1986-2002) Long-term average monitoring station; 1000

Surface bloom of the cyanobacterium *

(1984-2000) b) Surface water -1 s Long-term average temperature at Maryland Microcystis aeruginosa in the Potomac River in erence (1970-2002) Department of Natural August 2004. (Source: Morgan State University (di ff - cubic ft River discharge

Resources monitoring site Estuarine Research Center.) from long-term average

ter temperature TF2.4; Wind event

Wa c) Cloud cover at Hurricane Hurricane

erage % of sky obscured by cloud Baltimore-Washington Ivan

River discharge (cubic ft Isabel >15knts) Wind event (hours wind Av International airport: Further information on Potomac River harmful algal blooms can be found at found at the Maryland NOAA National Weather Jan Mar May Jul Sep Nov Jan Mar May Jul Sep Nov Sources: Dissolved oxygen and water temperature data from Maryland Department of Natural Resources 2003 2004 2003 2004 2003 2004 Service. Department of Natural Resources website: monitoring site CB3.3. River discharge data from United States Geological Survey River Input Monitoring Program. Year Year Year http://www.dnr.state.md.us/bay/hab/index.html Wind data from National Oceanographic and Atmospheric Administration – Thomas Point Lighthouse.