http://gulfsci.usgs.gov/tampabay/conf2002/sea_johansson/index.html

U. S. Geological Survey, Florida Integrated Science Center, Center for Coastal & Watershed Studies
600 4th Street South, St. Petersburg, FL 33701, Phone: 727-803-8747

Gulf of Mexico Estuaries Integrated Science
Tampa Bay Pilot Study
2nd Annual Science Conference, St. Petersburg, FL, Sept. 19, 2002
Poster Presentations: Seagrass Section

Task Leader: Kimberly Yates, Email: kyates@usgs.gov

Poster Title: Seagrass Monitoring in Tampa Bay Using Fixed Transects
by Walter Avery, John Pacowta, and J.O.R. Johansson. (City of Tampa, Bay Study Group)

Abstract:
In 1998, a consortium of regional agencies initiated a seagrass monitoring program under the auspices of the Tampa Bay Estuary Program (TBEP). Nearly sixty transects are visited each fall in order to document changes within seagrass communities found in the major subsections of Tampa Bay. Transects generally start at the shoreline, extend seaward, and approach the seagrass restoration depths established by the TBEP for each bay subsection. Seagrass coverage along each transect is estimated at specific intervals using the Braun Blanquet rating criteria. Data on species composition and zonation over a depth gradient may be used to assess restoration goals.

Introduction:
Tampa Bay seagrass meadows have been selected by the TBEP as a biological indicator to help evaluate the progress of the nitrogen reduction strategy implemented for Tampa Bay (TBNEP, 1996). The Technical Advisory Committee (TAC) of the TBEP recognized in the early 1990s the need of local resource managers to obtain timely information about trends and conditions of Tampa Bay seagrass meadows in addition to the aerial photography surveys and mapping information produced every other year by the Southwest Florida Water Management District - Surface Water Improvement Management Department.

In 1997, local scientists convened to establish protocols for a seagrass transect monitoring program in Tampa Bay using guidelines outlined in a 1994 TAC report addressing seagrass studies. Fixed transect monitoring began the following year as local agencies contributed equipment and personnel to the Tampa Bay Interagency Seagrass Monitoring Program. Three years of data have been collected documenting temporal and spatial changes in seagrass species composition and abundance in Tampa Bay.

Methods:
Species composition, abundance, and ancillary data are collected at 25 or 50 meter intervals over the length of the transect. Detailed water column and seagrass data are collected at mid bed, edge bed, and 2m contour as show n based on the depth to which the grass grows.

Results:
Transect data from the year 2000 show the occurrence of each seagrass species and bare bottom expressed as the percent of the total meter square placements (% of N) per transect. Percent data and transect location are expressed on the Tampa Bay map. For more detailed information on each transect please refer to the bay segment notebooks below.

Discussion:
Seagrass species abundance and zonation along the Old Tampa Bay transects has remained relatively stable over the period of monitoring, 1998 to 2000. There were only minor changes in species abundance and zonation at all transects for the five seagrass species. Generally, T. testudinum and S. filiforme are more commonly found on transects located on the eastern side of the bay and H. wrightii generally dominates the species composition on the western side.

H. wrightii was the dominant seagrass found on transects located in Hillsborough Bay. Prior to 1999, H. wrightii was most abundant on the southeastern Hillsborough Bay transects, however, between 1999 and 2000, substantial meadows appeared to be developing along transects located along the Interbay Peninsula in the southwestern portion of the bay.

Between 1998 and 2000, H. wrightii appeared to decline along transects located in eastern Middle Tampa Bay. However, there was a slight increase of T. testudinum abundance on the four transects located between the Little Manatee River and Piney Point, including Cockroach Bay. Generally, H. wrightii is the dominant seagrass species in the northern section of Middle Tampa Bay. T. testudinum and S. filiforme are more commonly found on the transects located in the middle and south sections of this bay subsection.

Seagrass abundance along the transects located in Lower Tampa Bay remained relatively stable between 1998 and 2000, however, minor thinning was noted for T. testudinum along four transects in eastern Lower Tampa Bay. T. testudinum is generally the dominant seagrass species found on the transects in the Lower Tampa Bay proper.

Minor changes in seagrass abundance were noted along the transects located in Boca Ciega Bay between 1998 and 2000. H. wrightii, dominated seagrass species in the northern section of the bay and T. testudinum generally was prevalent in the southern portion.

Results from the Tampa Bay transect monitoring program indicate two major areas with recent and notable changes in seagrass coverage. Seagrass coverage increased along the southeastern Interbay Peninsula as H. wrightii meadows developed between 1998 and 2000. In contrast, a loss of H. wrightii was noted along eastern Tampa Bay from southeastern Hillsborough Bay to Piney Point between 1999 and 2000.

The interagency seagrass monitoring program has proven that multiple agencies with a common goal can effectively combine their resources to generate valuable scientific information that will assist in the protection and restoration of Tampa Bay seagrass meadows.

Acknowledgments:
This project has been made possible through the auspices of the Tampa Bay Estuary Program. Special thanks are extended to Holly Greening who has facilitated the coordination and implementation of the seagrass monitoring program. Also, Dave Tomasko (Southwest Florida Water management District - Surface Water Improvement Management Program), Ray Kurz (Post, Buckley, Schuh, & Jernigan, Inc.), and Tom Reis (Scheda Ecological Associates, inc.) provided guidance in the initial design of the monitoring protocols. Field collections were conducted by personnel from Florida Fish & Wildlife Conservation commission - Florida Marine Research Institute, Hillsborough County Cockroach Bay Aquatic Preserve, Hillsborough County Environmental Protection Commission, Manatee County Environmental Management, Pinellas County Department of Environmental Management, Tampa BayWatch, Inc., and City of Tampa Bay Study Group. The generous contributions from these agencies and the hard work by their personnel have ensured the success of this project. Finally, Robin Lewis (Lewis Environmental Services, Inc.) is acknowledged for early on advocating the need to establish permanent seagrass transects in Tampa Bay and for his continued support of this program. The compilation of the collected information into this report was funded by TBEP and the City of Tampa.

Image Text and Captions:

Percent composition for each seagrass species along each transect during the year 2000.

Methods for transects with seagrass coverage less than 2 meters of depth.

Braun Blanquet
25/50m centers

Mid Bed
a) Short shoot density
b) Blade length
c) Epiphytic cover
d) PAR
e) Mid depth grab
f) Sediment description
g) Hydrographic data
h) Depth
i) Time

Every meter placement:
a) Depth
b) Sediment description
c) Epiphyte cover
d) Braun Blanquet rating for each species
e) Time

Braun Blanquet
10m centers

Edge Bed
a) Short shoot density
b) Blade length
c) Epiphytic cover
d) PAR
e) Mid depth grab
f) Sediment description
g) Hydrographic data
h) Depth
i) Time

2m contour
a) PAR
b) Mid depth grab
c) Secchi depth
d) Hydrographic data

Methods for transects with seagrass coverage greater than 2 meters of depth.

Braun Blanquet
25/50m centers

Mid Bed
a) Short shoot density
b) Blade length
c) Epiphytic cover
d) PAR
e) Mid depth grab
f) Sediment description
g) Hydrographic data
h) Depth
i) Time

Braun Blanquet
10m centers
Coverage <25% in
this 100m segment

2m contour
no sample

Edge Bed
a) Short shoot density
b) Blade length
c) Epiphytic cover
d) PAR
e) Mid depth grab
f) Secchi depth
g) Sediment description
h) Hydrographic data
i) Depth
j) Time

http://gulfsci.usgs.gov/tampabay/conf2002/sea_johansson/index.html