Submerged Aquatic Vegetation (SAV) update

Science, Service, & Stewardship 10/18/2007

Submerged Aquatic Vegetation (SAV) update

Peter Bergstrom, NOAA Chesapeake Bay Office

MASC Workshop, 10/18/07


SAV survey status & results

• 2007 areas will not be ready at least until February– Flight lines completed only recently—see map, next slide

• SAV transects in several rivers; better ground survey data– Done for years by Nancy Rybicki’s group in the Potomac; can show

patterns by species (see examples below)– 2007 transects started in MD by riverkeepers and volunteers in Bush,

Patuxent, Chester, West/Rhode, Severn, South and Magothy rivers– VA transects done by VIMS in 2006-07 in York (6 sites) and Mobjack

Bay (3 sites); also about 100 sites on both VA shores surveyed 2006-07 for eelgrass abundance

• 2006 report incorporates new interactive map– This now contains the ground truth data; these are no longer shown

on the quad maps

• 2006 results show declines from 2004 & 2005 in all zones, including MD & VA coastal bays—why?


2007FlightLines (allare done now)


Collecting SAV transect data

Tools: oyster tongs, graduatedcylinders, GPS, buoys


SAV patterns by species from Potomac transect data

Peak in Hydrilla moved downriver

More TN means less species diversity

Source: Nancy Rybicki, USGS


Sample transect data: abundance by species by distance from shore

SAV volume by distanceSevern River, three transects, 9/11/07

0

50

100

150

200

250

300

350

400

10 20 30 40 50 60

Distance from shore (m)

SA

V v

olu

me

per

sit

e (m

l)

Rm SC

Ppf SC

Rm BP

Ppf BP

Rm AC

Ppf AC


New interactive map in 2006 shows ground truth data

Upper Magothy


Recent SAV patterns

• Baywide area and some zones increased during 2001-2002 drought– Increased in higher salinity zones only (mid

and lower Bay)

• SAV area declined baywide and in all zones, including coastal bays, in 2006– In lower Bay, this was delayed response to

2005 hot summer (photos taken in spring)

– May be some increases in 2007


Baywide area peaked in 2002, declined in 2006

Not including Coastal bays

Drought


SAV area declined in all zones in 2006

Coastal bays not surveyed in 2005; similar declines 05-06 in other zones


SAV Area by zone through 2006 (upper Bay)

Drought

May be up in 2007(Flats, Bush, Gun-powder very healthy)

Probably down in 2007(very little in Chester, Eastern Bay, Choptank,or lower Potomac)


Area by zone through 2006 (lower & coastal bays)

Drought

Up slightly in 2007 (2006 drop caused by 2005summer heat)

May be down in 2007 (only healthybeds near inlets)


Why is SAV declining baywide?

• Declining water clarity

• Are water temperatures increasing?– either on average, or the summer peaks are getting

higher & longer? – Extra-high peak preceded 2005 eelgrass dieback, lower

Bay (see next slide)


Warmer water in 2005 preceded eelgrass dieback

Source: Bob Orth, VIMS


The future of SAV in the Bay

• If summer water temperatures keep climbing, eelgrass (Zostera marina) will continue to have trouble

• If water clarity keeps declining, all species will have trouble • So, what can we do to increase SAV area?

– SAV planting -139 acres planted to date in Bay, but success is low. Some of planted beds are present & expanding, though (6-7 sites)

– Improve water clarity - how??– Introduce other SAV species that can tolerate higher temperatures

and/or lower water clarity?• Shoal grass, Halodule wrightii, grows from NC south at present,

BUT its minimum salinity is 18 ppt vs. 10 ppt for eelgrass, so it could not really replace eelgrass

• Japanese eelgrass, Zostera japonica, is naturalized in Pacific NW, tolerates salinity lower than Z. marina, and may hold promise for the Chesapeake (need to know its ecology better)


Zostera japonica images

Z. marina

Z. japonica

Zostera at Padilla Bay, WA Intertidal Z. japonica

Intertidal Z. japonica in Japan

Z. japonica

Submerged Aquatic Vegetation (SAV) update

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