SAV Home > 2016 SAV Report > Preliminary Executive Summary

The 2016 distribution of submerged aquatic vegetation (SAV) in Chesapeake Bay and its tributaries was mapped from multispectral digital imagery. These were acquired between May and November 2016, with a resolution of 24 cm, encompassing 171 flight lines. National Agricultural Imagery Program (NAIP) imagery was used to augment the multispectral imagery in a portion of the Potomac, James, and Pamunkey rivers.

CHESAPEAKE BAY

For 2016, 39,429 hectares (97,433 acres) of SAV were mapped in Chesapeake Bay and its tributaries. However, weather conditions and security restrictions in the DC area, over Patuxent Air Base and associated mid-Bay areas prevented acquisition of useable imagery for a portion of the tidal fresh and mesohaline Potomac River, including Piscataway Creek and St. Marys River. A small portion of this area was covered by NAIP imagery under conditions that were appropriate for mapping SAV. The area that was not fully mapped in 2016 supported 801.75 ha of SAV in 2015 (1981.20 acres, 2% of the 2015 Bay total).

In order to ensure a valid analysis of change in SAV distribution and abundance given the reduced region mapped in 2016, all direct comparisons to previous years in this report are restricted to only those regions that were mapped in both years. Partial totals for 2015 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 2016 and 2015. SAV increased 8% from 36,556 ha (90,334 ac) to 39,427 ha (97,427 ac) in the regions mapped for both years.

Bay Chart

SAV increased in the Tidal Fresh and Mesohaline salinity zones and decreased in the Oligohaline and Polyhaline salinity zones in the Chesapeake Bay. In 2016, SAV increased in 41, decreased in 26, and remained unvegetated in 26 of the 93 CBP segments.

Segment Comparision

The 2,871 ha increase in Baywide SAV coverage within the area that was fully mapped makes 2016 the second consecutive year with more area of SAV reported for the Bay than at any prior year in the history of the Baywide annual aerial survey (1984 - 2016). Given the trends in the areas mapped, the SAV in the unmapped areas likely would put the complete Bay area total close to 40,000 ha. This represents a continued recovery from strong declines in 2011 and 2012 that reduced SAV abundance to a level last reported for the Bay in 1986. The 2016 increase was the result of a strong increase in the Tidal Fresh and Mesohaline salinity zones (578 ha and 3,930 ha in fully mapped areas, respectively). In the Mesohaline salinity zone widgeongrass continued to increase. However, this species has had boom and bust cycles throughout the history of this survey. A similar rapid increase in widgeongrass in 2001 and 2002 was followed by an approximately 50% loss the following year. SAV decreased in the Polyhaline salinity zone following several years of recovery of eelgrass from the loss that occurred during the hot summers of 2005 and 2010.

Tidal Fresh Bay Salinity Zone

In the Tidal Fresh Bay Zone (19 CBP segments), 7,008 hectares (17,319 ac) of SAV were mapped for 2016. However, portions of the zone, including the portion of the Potomac River from Broad Creek to Pomoney Creek, those creeks, and Piscataway Creek, representing 643 ha of SAV in 2015 (1,588 ac, 9% of the zone total) were not mapped for 2016. Comparing the same mapped regions between 2015 and 2016, SAV increased 9% from 6,430 hectares (15,889 ac) in 2015 to 7,008 hectares (17,319 ac) in 2016.

Tidal Fresh Salinity Zone Chart

Three of the 19 segments increased by at least 20% and by at least 5 ha from 2015 totals.

up arrow

21%, Northern Chesapeake Bay Segment 1 (CB1TF1), 193 ha (2015) vs. 233 ha (2016)

up arrow

78%, Upper Rappahannock River (RPPTF), 69 ha (2015) vs. 123 ha (2016)

up arrow

2370%, Upper Chester River (CHSTF), 6 ha (2015) vs. 145 ha (2016)

In addition, the Upper Potomac River, though not full mapped, increased by 18% in the area mapped, adding 364 ha (899 ac) to the Tidal Fresh Bay Zone total for 2016.

Three of the 19 segments decreased by at least 20% and by at least 5 ha from 2015 totals.

down arrow

100%, Upper Patuxent River (PAXTF), 38 ha (2015) vs. 0 ha (2016)

down arrow

100%, Upper Mattaponi River (MPNTF), 164 ha (2015) vs. 0 ha (2016)

down arrow

84%, Upper James River Segment 1 (JMSTF1), 229 ha (2015) vs. 37 ha (2016)

Six of the 19 segments remained unvegetated in 2016.

Oligohaline Bay Salinity Zone

In the Oligohaline Bay Zone (25 CBP segments), SAV decreased 16% from 4,091 hectares (10,109 ac) in 2015 to 3,441 hectares (8,503 ac) in 2015.

Oligohaline Salinity Zone Chart

One of the 25 segments increased by at least 20% and by at least 5 ha from 2015 totals:

up arrow

38%, Sassafras River Segment 1 (SASOH1), 49 ha (2015) vs. 68 ha (2016)

Eight of the 25 segments decreased by at least 20% and by at least 5 ha from 2015 totals.

down arrow

21%, Bohemia River (BOHOH), 151 ha (2015) vs. 119 ha (2016)

down arrow

27%, Upper Chesapeake Bay (CB2OH), 172 ha (2015) vs. 126 ha (2016)

down arrow

41%, Sassafras River Segment 2 (SASOH2), 42 ha (2015) vs. 25 ha (2016)

down arrow

83%, Bush River (BSHOH), 148 ha (2015) vs. 25 ha (2016)

down arrow

46%, Gunpowder River Segment 1 (GUNOH1), 139 ha (2015) vs. 75 ha (2016)

down arrow

100%, Middle Patuxent River (PAXOH), 13 ha (2015) vs. 0 ha (2016)

down arrow

66%, Middle Potomac River Segment 2 (POTOH2), 116 ha (2015) vs. 39 ha (2016)

down arrow

62%, Chickahominy River (CHKOH), 527 ha (2015) vs. 199 ha (2016)

Five of the 25 segments remained unvegetated in 2016.

Mesohaline Bay Salinity Zone

In the Mesohaline Bay Salinity Zone (41 CBP segments), 23,220 hectares (57,380 ac) of SAV were mapped for 2016. However, portions of the zone, including the north shore of the Potomac River from Herring Creek to Smith Creek, those creeks, and the St. Marys River, representing 159 ha of SAV in 2015 (393 ac, 1% of the zone total) were not mapped for 2016. Comparing the same mapped regions between 2015 and 2016, SAV increased 20% from 19,290 hectares (47,668 ac) in 2015 to 23,220 hectares (57,380 ac) in 2016.

Mesohaline Salinity Zone Chart

Fifteen of the 41 segments increased by at least 20% and by at least 5 ha from 2015 totals:

up arrow

43%, Lower Chester River (CHSMH), 155 ha (2015) vs. 221 ha (2016)

up arrow

100%, Middle Central Chesapeake Bay (CB4MH), 0 ha (2015) vs. 14 ha (2016)

up arrow

55%, Eastern Bay (EASMH), 609 ha (2015) vs. 942 ha (2016)

up arrow

20%, Mouth of the Choptank River (CHOMH1), 2447 ha (2015) vs. 2938 ha (2016)

up arrow

117%, Little Choptank River (LCHMH), 343 ha (2015) vs. 743 ha (2016)

up arrow

34%, Severn River (SEVMH), 94 ha (2015) vs. 126 ha (2016)

up arrow

40%, Lower Central Chesapeake Bay (CB5MH), 1497 ha (2015) vs. 2095 ha (2016)

up arrow

26%, Honga River (HNGMH), 2516 ha (2015) vs. 3180 ha (2016)

up arrow

169%, Manokin River Segment 2 (MANMH2), 16 ha (2015) vs. 43 ha (2016)

up arrow

26%, Big Annemessex River Segment 1 (BIGMH1), 490 ha (2015) vs. 618 ha (2016)

up arrow

253%, Big Annemessex River Segment 2 (BIGMH2), 4 ha (2015) vs. 15 ha (2016)

up arrow

77%, Lower Patuxent River Segment 1 (PAXMH1), 7 ha (2015) vs. 13 ha (2016)

up arrow

32%, Lower Rappahannock River (RPPMH), 477 ha (2015) vs. 629 ha (2016)

up arrow

36%, Corrotoman River (CRRMH), 110 ha (2015) vs. 150 ha (2016)

up arrow

52%, Piankatank River (PIAMH), 205 ha (2015) vs. 311 ha (2016)

Three of the 41 segments decreased by at least 20% and by at least 5 ha from 2015 totals:

down arrow

91%, Patapsco River (PATMH), 16 ha (2015) vs. 1 ha (2016)

down arrow

64%, Magothy River (MAGMH), 13 ha (2015) vs. 5 ha (2016)

down arrow

87%, Lower Potomac River (POTMH), 114 ha (2015) vs. 14 ha (2016)

Fourteen of the 41 segments remained unvegetated in 2016.

* Segment comparison restricted to areas mapped in both 2015 and 2016

Polyhaline Bay Salinity Zone

In the Polyhaline Bay Zone (8 CBP segments), SAV decreased 15% from 6,745 ha (16,667 ac) in 2015 to 5,757 ha (14,226 ac) in 2016.

Polyhaline Salinity Zone Chart

None of the 8 segments increased by at least 20% and by at least 5 ha from 2015 totals:

Three of the 8 segments decreased by at least 20% and by at least 5 ha from 2015 totals.

down arrow

26%, Mobjack Bay (MOBPH), 3319 ha (2015) vs. 2451 ha (2016)

down arrow

22%, Lower York River (YRKPH), 244 ha (2015) vs. 190 ha (2016)

down arrow

31%, Mouth of the James River (JMSPH), 149 ha (2015) vs. 103 ha (2016)

One of the 8 segments remained unvegetated in 2016.