The distribution of submerged aquatic vegetation (SAV) in Chesapeake Bay, its tributaries, and the Maryland and Virginia coastal bays of the Delmarva Peninsula, was mapped from black and white aerial photographs. These were taken between May and December 2004, at a scale of 1:24,000, encompassing 173 flight lines. In addition, color aerial photography acquired by Air Survey Inc. provided coverage for sections of the upper Potomac River.
CHESAPEAKE BAY
For 2004, 29,519 hectares (72,945 acres) of SAV were mapped in Chesapeake Bay and its tributaries (Figure 1). However, in 2003 some portions of the Bay were not flown due to adverse weather in the spring and summer and Hurricane Isabel in the fall. These regions, including Tavern and Swan creeks; lower Chester River; upper Wicomico River; Prentice, Dividing, and Ball creeks; Dameron Marsh; and Great Wicomico River were not fully mapped in 2003.
In order to ensure a valid analysis of change in SAV distribution and abundance given the reduced region mapped in 2003, all direct comparisons to 2003 in the report are restricted to only those regions that were mapped in both years. For comparison purposes, partial totals for 2004 have been computed for CBP segments, Bay zones, and the entire Bay using only those regions mapped for both years.
Notable changes in SAV distribution were measured between 2003 and 2004. SAV increased 14% from 24,888 ha (60,512 ac) in 2003 to 27,891 ha (68,922 ac) in 2004 in the regions mapped for both years.
SAV increased in two (Upper and Middle) and decreased in one (Lower) geographic zones delineated for Chesapeake Bay. In 2004, SAV increased in 39, decreased in 17, and remained unvegetated in 22 of the 78 CBP segments (Table 6).
The notable changes in SAV distribution in 2004 are the result of substantial increases in freshwater species in the upper and mid-bay regions, notably the Susquehanna Flats (CB1TF), Elk River (ELKOH), and Gunpowder River (GUNOH). SAV declined in the higher salinity lower region of the bay. This decline is a result of Hurricane Isabel which heavily impacted some SAV beds in this region in 2003.
Upper Bay Zone
In the Upper Bay Zone (17 CBP segments extending south from the Susquehanna River to the Chester and Magothy rivers), 8,771 ha (21,674 ac) of SAV were mapped for 2004. However, portions of the zone including Tavern and Swan creeks and the lower Chester River were not mapped in 2003. Comparing the same mapped regions between 2003 and 2004, SAV increased from 4,200 ha (10,378 ac) in 2003 to 8,264 ha (20,420 ac) in 2004.
Fourteen of the 17 segments (or mapped portions) increased by at least 20% and by at least 5 ha from 2003 totals (Table 6). These segments were:
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33%, Northern Chesapeake Bay (CB1TF), 4,089 ha (2004) vs. 3,063 ha (2003) |
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83%, Northeast River (NORTF), 34 ha (2004) vs. 19 ha (2003) |
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453%, Elk River (ELKOH), 774 ha (2004) vs. 140 ha (2003) |
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153%, Bohemia River (BOHOH), 295 ha (2004) vs. 117 ha (2003) |
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516%, Upper Chesapeake Bay (CB2OH), 527 ha (2004) vs. 86 ha (2003) |
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243%, Sassafras River (SASOH), 514 ha (2004) vs. 150 ha (2003) |
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163%, Bush River (BSHOH), 414 ha (2004) vs. 158 ha (2003) |
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389%, Gunpowder River (GUNOH), 968 ha (2004) vs.198 (2003) |
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71%, Middle River (MIDOH), 271 ha (2004) vs. 158 ha (2003) |
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100%, Back River (BACOH), 12 ha (2004) vs. 0 ha (2003) |
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77%, Upper Central Chesapeake Bay (CB3MH), 16 ha (2004) vs. 9 ha (2003)* |
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3,004%, Patapsco River (PATMH), 82 ha (2004) vs. 3 ha (2003) |
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78%, Magothy River (MAGMH), 121 ha (2004) vs. 68 ha (2003) |
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338%, Lower Chester River (CHSMH), 140 ha (2004) vs. 32 ha (2003)* |
None of the 17 segments (or mapped portions) decreased by at least 20% and by at least 5 ha from 2003 totals (Table 6).
One of the 17 segments remained unvegetated (Table 6).
Middle Bay Zone
In the Middle Bay Zone (34 CBP segments extending south from the Bay Bridge to the Rappahannock River and Pocomoke Sound, and including the Potomac River), 13,642 ha (33,711 ac) of SAV were mapped for 2004. However, portions of the zone, including upper Wicomico River; Prentice, Dividing, and Ball creeks; Dameron Marsh; and Great Wicomico River were not mapped for 2003. Comparing the same mapped regions between 2003 and 2004, SAV increased 5% from 11,869 ha (29,330 ac) in 2003 to 12,521 ha (30,941 ac) in 2004.
Nine of the 34 segments (or mapped portions) increased by at least 20% and by at least 5 ha from 2003 totals (Table 6). These segments include:
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27%, Mouth of the Choptank River (CHOMH1), 1,527 ha (2004) vs.1,202 ha (2003) |
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56%, Little Choptank River (LCHMH), 494 ha (2004) vs. 317 ha (2003) |
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75%, Severn River (SEVMH), 157 ha (2004) vs. 90 ha (2003) |
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238%, South River (SOUMH), 19 ha (2004) vs. 6 ha (2003) |
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21%, Honga River (HNGMH), 1,388 ha (2004) vs. 1,150 ha (2003) |
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24%, Manokin River (MANMH), 118 ha (2004) vs. 95 ha (2003) |
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22%, Big Annemessex River (BIGMH), 222 ha (2004) vs. 182 ha (2003) |
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48%, Upper Potomac River (POTTF), 972 ha (2004) vs. 655 ha (2003) |
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139%, Piscataway Creek (PISTF), 205 ha (2004) vs. 86 ha (2003) |
Four of the 34 segments (or mapped portions) decreased by at least 20% and by at least 5 ha from 2003 totals (Table 6). These segments were:
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37%, Eastern Bay (EASMH), 421 ha (2004) vs. 663 ha (2003) |
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100%, West River (WSTMH), 0 ha (2004) vs. 9 ha (2003) |
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43%, Lower Central Chesapeake Bay (CB5MH), 161 ha (2004) vs. 283 ha (2003)* |
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30%, Lower Pocomoke River (POCMH), 471 ha (2004) vs. 674 ha (2003) |
Eleven of the 34 segments remained unvegetated (Table 6).
Lower Bay Zone
In the Lower Bay Zone (27 CBP segments covering the region south from the Rappahannock River and Pocomoke Sound regions to the mouth of the Bay), 7,107 ha (17,561 ac) were mapped for 2004. SAV decreased 16% from 8,419 ha (20,804 ac) in 2003 to 7,107 ha (17,561 ac) in 2004. Some of this loss was likely caused by Hurricane Isabel.
Three of the 27 segments increased by at least 20% and by at least 5 ha from 2003 totals (Table 6). These segments include:
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416%, Corrotoman River (CRRMH), 91 ha (2004) vs. 18 ha (2003) |
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100%, Upper Rappahannock River (RPPTF), 10 ha (2004) vs. 0 ha (2003) |
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53%, Upper Pamunkey River (PMKTF), 135 ha (2004) vs. 88 ha (2003) |
Five of the 27 segments decreased by at least 20% and by at least 5 ha from 2003 totals (Table 6). These segments were:
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31%, Western Lower Chesapeake Bay (CB6PH), 198 ha (2004) vs. 286 ha (2003) |
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22%, Eastern Lower Chesapeake Bay (CB7PH), 2,896 ha (2004) vs. 3,720 ha (2003) |
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33%, Lower York River (YRKPH), 242 ha (2004) vs. 359 ha (2003) |
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44%, Mouth of the James River (JMSPH), 30 ha (2004) vs. 53 ha (2003) |
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84%, Upper James River (JMSTF), 5 ha (2004) vs. 30 ha (2003) |
Ten segments remained unvegetated in 2004 (Table 6).
DELMARVA PENINSULA COASTAL BAYS ZONE
In the Delmarva Peninsula Coastal Bays Zone (Assawoman, Isle of Wight, Sinepuxent, Chincoteague, and southern Virginia coastal bays) 7,033 ha (17,380 ac) were mapped in 2004, a 5% decrease from the 2003 level of 7,414 ha (18,320 ac) (Table 6).
Two of the five segments increased. These segments include:
| 12%, Assawoman Bay (AAWPH), 228 ha (2004) vs. 204 ha (2003) | |
| 15%, Sinepuxent Bay (SPXPH), 802 ha (2004) vs. 696 ha (2003) |
Three of the five segments decreased. These segments include:
| 7%, Isle of Wight Bay (IOWPH), 126 ha (2004) vs. 136 ha (2003) | |
| 8%, Chincoteague Bay (CHNPH), 5,732 ha (2004) vs. 6,220 ha (2003) | |
| 8%, Southern Virginia Coastal Bays (SVCPH), 146 ha (2004) vs. 158 ha (2003) |
The most notable change was the large decrease in Chincoteague Bay (CHNPH).
Most of the SAV mapped in the Southern Virginia Coastal Bays (or Atlantic Coast Bays) segment were the result of successful restoration efforts initiated in 1997 through the Virginia Coastal Program's Seaside Heritage Program.
* Segment comparison restricted to areas mapped in both 2004 and 2003