The distribution of submerged aquatic vegetation (SAV) in Chesapeake Bay, its tributaries, and the coastal bays of the Delmarva Peninsula, was mapped from black and white aerial photographs. These were taken between May and November 2003, at a scale of 1:24,000, encompassing 193 flight lines. In addition, color aerial photography acquired by St. Mary's County, Maryland and the Metro Washington Council of Governments provided coverage for sections of the lower Potomac River
CHESAPEAKE BAY
For 2003, 24,966 hectares (61,694 ac) of SAV were mapped in Chesapeake Bay and its tributaries. However 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. These regions had 1,220 ha of SAV in 2002 (3,015 ac, 3% of the 2002 total).
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 previous years in the report are restricted to only those regions that were mapped in both years. Partial totals for 2002 have been computed for CBP segments, Bay zones, and the entire Bay using only those regions mapped for both years.
Significant changes in SAV distribution were measured between 2002 and 2003. SAV decreased 30% (10,576 ha, 26,134 ac) in the regions mapped for both years.
SAV decreased in all three zones (Upper, Middle, and Lower) geographic zones delineated for Chesapeake Bay. In 2003, SAV increased in 12, decreased in 42, and remained unvegetated in 24 of the 78 CBP segments (Table 6).
The significant changes in SAV distribution in 2003 appear to be the result of substantial reductions in widgeongrass populations in the lower and mid-bay regions, notably the Rappahannock River (RPPMH, CRRMH) and the region from Tangier Island to Eastern Bay (TANMH, HNGMH, LCHMH, CHOMH1, EASMH). For example, 63% of the loss of SAV in the lower bay zone occurred in the Rappahannock area where widgeongrass was most abundant previously. In addition to these large declines in widgeongrass, major declines in freshwater SAV species occurred in the upper portion the Potomac River (POTTF) and Susquehanna region (CB1TF). While populations of SAV appeared to be present in these segments very early in the growing season, the persistent turbidity resulting from rain occurring thoughout the spring and summer may have contributed to a very early decline, well before Hurricane Isabel affected Chesapeake Bay.
Upper Bay Zone
In the Upper Bay Zone (17 CBP segments extending south from the Susquehanna River to the Chester and Magothy rivers), 4,215 hectares (10,416 ac) of SAV were mapped for 2003. However, portions of the zone, including the upper central Chesapeake Bay and the lower Chester River, representing 64 ha (157 ac, 1.2% of the zone total) of SAV in 2002 were not mapped for 2003. Comparing the same mapped regions between 2002 and 2003, SAV declined from 5,264 hectares (13,009 ac) in 2002 to 4,200 hectares (10,378 ac) in 2003.
Only one of the 17 segments (or mapped portions) increased by at least 20% and by at least 5 hectares from 2002 totals (Table 6). This segment was:
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112%, Bohemia River (BOHOH), 117 ha (2003) vs. 55 ha (2002) |
Six of the 17 segments (or mapped portions) decreased by at least 20% and by at least 5 hectares from 2002 totals (Table 6). These segments were:
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39%, Northeast River (NORTF), 19 ha (2003) vs. 31 ha (2002) |
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21%, Elk River (ELKOH), 140 ha (2003) vs. 176 ha (2002) |
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58%, Upper Chesapeake Bay (CB2OH), 86 ha (2003) vs. 203 ha (2002) |
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55%, Sassafras River (SASOH), 150 ha (2003) vs. 336 ha (2002) |
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38%, Middle River (MIDOH), 158 ha (2003) vs. 255 ha (2002) |
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35%, Lower Chester River (CHSMH), 32 ha (2003) vs. 50 ha (2002) |
Four of the 17 segments remained unvegetated (Table 6).
SAV decreased by 18% from 3,734 hectares (9,227 ac) in 2002 in the Northern Chesapeake Bay segment (CB1TF) to 3,063 ha (7,569 ac).
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), 12,333 hectares (30,475 ac) of SAV were mapped for 2003. However, portions of the zone, including upper Wicomico River; Prentice, Dividing, and Ball creeks; Dameron Marsh; and Great Wicomico River representing 1,157 ha (2,858 ac, 5.4% of the zone total) of SAV in 2002 were not mapped for 2003. Comparing the same mapped regions between 2002 and 2003, SAV decreased 41% from 20,280 (50,115 ac) in 2002 to 11,869 (50,115 ac) in 2003.
Four of the 34 segments (or mapped portions) increased by at least 20% and by at least 5 hectares from 2002 totals (Table 6). These segments include:
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100%, West River (WSTMH), 9 ha (2003) vs. 0 ha (2002) |
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405%, Middle Patuxent River (PAXOH), 43 ha (2003) vs. 9 ha (2002) |
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27%, Upper Patuxent River (PAXTF), 88 ha (2003) vs. 69 ha (2002) |
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49%, Middle Potomac River (POTOH), 1,349 ha (2003) vs. 904 ha (2002) |
Seventeen of the 34 segments (or mapped portions) decreased by at least 20% and by at least 5 hectares from 2002 totals (Table 6). These segments were:
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92%, Middle Central Chesapeake Bay (CB4MH), 9 ha (2003) vs. 109 ha (2002) |
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41%, Eastern Bay (EASMH), 663 ha (2003) vs. 1,125 ha (2002) |
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55%, Mouth of the Choptank River (CHOMH1), 1,202 ha (2003) vs. 2,665 ha (2002) |
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100%, Lower Choptank River (CHOMH2), 0 ha (2003) vs. 63 ha (2002) |
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73%, Little Choptank River (LCHMH), 317 ha (2003) vs. 1,176 ha (2002) |
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21%, Severn River (SEVMH), 90 ha (2003) vs. 114 ha (2002) |
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62%, South River (SOUMH), 6 ha (2003) vs. 14 ha (2002) |
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67%, Lower Central Chesapeake Bay (CB5MH), 283 ha (2003) vs. 865 ha (2002)* |
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55%, Honga River (HNGMH), 1,150 ha (2003) vs. 2,559 ha (2002) |
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86%, Fishing Bay (FSBMH), 6 ha (2003) vs. 44 ha (2002) |
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37%, Tangier Sound (TANMH), 3,806 ha (2003) vs. 6,079 ha (2002) |
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68%, Manokin River (MANMH), 94 ha (2003) vs. 295 ha (2002) |
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42%, Big Annemessex River (BIGMH), 182 ha (2003) vs. 316 ha (2002) |
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74%, Lower Patuxent River (PAXMH), 15 ha (2003) vs. 57 ha (2002) |
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56%, Upper Potomac River (POTTF), 655 ha (2003) vs. 1,484 ha (2002) |
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23%, Mattawoman Creek (MATTF), 248 ha (2003) vs. 321 ha (2002) |
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66%, Piscataway Creek (PISTF), 86 ha (2003) vs. 256 ha (2002) |
Ten 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), 8,418 hectares (20,803 ac) were mapped for 2003. SAV decreased 12% (1,100 ha, 2,718 ac) in 2003.
Three of the 27 segments (or mapped portions) increased by at least 20% and by at least 5 hectares from 2002 totals (Table 6). These segments include:
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713%, Upper Mattaponi River (MPNTF), 74 ha (2003) vs. 9 ha (2002) |
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27%, Upper Pamunkey River (PMKTF), 88 ha (2003) vs. 69 ha (2002) |
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128%, Chickahominy River (CHKOH), 172 ha (2003) vs. 75 ha (2002) |
Five of the 27 segments decreased by at least 20% and by at least 5 hectares from 2002 totals (Table 6). These segments were:
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98%, Lower Rappahannock River (RPPMH), 9 ha (2003) vs. 407 ha (2002) |
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94%, Corrotoman River (CRRMH), 18 ha (2003) vs. 311 ha (2002) |
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36%, Piankatank River (PIAMH), 181 ha (2003) vs. 284 ha (2002) |
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53%, Mouth of the James River (JMSPH), 53 ha (2003) vs. 114 ha (2002) |
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100%, Lynnhaven & Broad Bays (LYNPH), 0 ha (2003) vs. 16 ha (2002) |
Twelve segments were unvegetated in 2003 (Table 6).
* Segment comparison restricted to areas mapped in both 2003 and 2002
DELMARVA PENINSULA COASTAL BAYS ZONE
In the Delmarva Peninsula Coastal Bays Zone (Assawoman, Isle of Wight, Sinepuxent, Chincoteague, and Southern Virginia Coastal Bays) 7,414 hectares (18,320 ac) were mapped in 2003, a 1% (94 ha, 233 ac) increase from the 2002 level of 7,319 hectares (18,087 ac) (Table 6).
Three of the five segments increased by at least 20% and by at least 5 hectares from 2002 totals (Table 6). These segments include:
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22%, Assawoman Bay (AAWPH), 204 ha (2003) vs. 167 ha (2002) |
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46%, Isle of Wight Bay (IOWPH), 136 ha (2003) vs. 93 ha (2002) |
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94%, Southern Virginia Coastal Bays (SVCPH), 158 ha (2003) vs. 82 ha (2002) |
Most of the SAV mapped in the southern Virginia Seaside 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 2003 and 2002