Seventy percent of Florida’s fishery species are dependent on seagrass beds for some portion of their life cycle (FWC) and with the economic value of Sarasota Bay being worth approximately $11.8 billion (SBEP Economic Value Study), we have a lot to be proud of and to protect locally. Sarasota County's Seagrass Monitoring Program aims at better understanding and managing seagrass habitat and the benefits that seagrasses provide.
Use these pages to learn more about our local seagrasses and the important roles that they play in bay health and productivity. To learn more about upcoming volunteer opportunities, visit the Sarasota County Volunteer Seagrass Monitoring Program page.
Seagrasses are marine flowering plants that form underwater meadows that cover about 35% of the bays in Sarasota County. Seagrass beds are vital to maintaining healthy aquatic ecosystems, by providing food and shelter for a variety of wildlife, including scallops, manatees and sea turtles. Seagrasses also improve water clarity by capturing and stabilizing sediments that would otherwise create turbid (cloudy) conditions in our bays. The most common seagrass species found in Sarasota County are Thalassia testudinum (turtle grass), Syringodium filiforme (manatee grass), and Halodule wrightii (shoal grass).
Seagrass acreage is a commonly used indicator of watershed management. Excess nutrients cause algal blooms which block sunlight from reaching the seagrasses on the bottom of the bay. Without sufficient sunlight, photosynthesis is inhibited and the overall acreage of seagrass declines. Globally, seagrasses are declining.
Sarasota County has used seagrass as an internal performance measure for watershed management for many years and the primary watershed effects on the bays are from stormwater runoff and pollution from nutrients in pet waste and fertilizer, oils, other chemicals and even yard debris.
Since 2006, the Sarasota County's Seagrass Monitoring Program has played an important role in assessing the state of the County's seagrass habitat and overall health of the bays. Sarasota County has a strong collaborative partnership with the Southwest Florida Water Management District (SWFWMD), Sarasota Bay Estuary Program (SBEP), Tampa Bay Estuary Program (TBEP), and Charlotte Harbor National Estuary Program (CHNEP), as well as other local environmental organizations.
County-wide, there has been a general increase in seagrass acreage, indicating that successful watershed management is having a positive effect on bay health. Contributions to the increase in acreage includes legislation in 1990 that mandated advanced wastewater treatment (low nitrogen) for discharges of treated sewage to surface waters in southwest Florida and other improved stormwater regulations, such as the Sarasota County Fertilizer Ordinance. Seagrass targets were developed by the three local National Estuary Programs (NEP's) in Southwest Florida and became the foundation of nutrient water quality standards for the County's monitoring program. The seagrass targets are not regulatory standards. Because each bay is different, unique targets were set for each bay and were either based on historic conditions or a recent healthy time period. According to the Sarasota County Seagrass Target Assessment Report, in 2012, there were approximately 1,300 more acres of seagrass than there were in 1948. More recently, SWFWMD’s 2014 Seagrass Mapping Results indicate a 5.7% increase in seagrass acreage for Sarasota Bay segments since 2012. This is great news for our bays and water resources! However, there is much more work to do to maintain and continue to increase this upward trend in seagrass acreage.
As part of the Southwest Florida Water Management Districts's (SWFWMD) SWIM Program, seagrass acreage is mapped via digital aerial photography every two years during the winter when the water clarity is best. Once the aerials are converted to GIS maps, Sarasota County staff members perform underwater field surveys to verify seagrass beds identified in the maps. County staff conduct these surveys on an annual basis during the winter to provide continuity with the time of year that the aerial photographs are taken.
A combined total of 160 random and fixed stations are surveyed by staff in Sarasota County baysheds, in order to assess seagrass presence or absence. If seagrass is present, the species composition and abundance is recorded, as well as presence or absence of attached, rooted, or epiphytic algae. Sediment type and observations of other organisms present are also recorded.
To view the most recent seagrass maps on the Water Atlas Advanced Mapping Application, select the "Layer List" tool and select the checkbox next to "2012 Seagrass".
Thanks to the 90 citizen scientists who joined us for the 3nd Annual Sarasota County Seagrass Survey on Saturday, April 29, 2017! During the 3 hour event, they visited and collect data for over 115 survey points, providing valuable data and having fun in the process.
Check out the results here:
2016 Seagrass Survey volunteers in action
More News Coverage (courtesy WWSB ABC-7):
On April 30, 2016, 106 volunteers took to Sarasota Bay and Roberts Bay North to record information about seagrass habitat at the 2nd Annual Sarasota County Seagrass Survey. In three brief hours, these intrepid volunteers were able to survey a total of 156 points and covered an extensive 28 acres throughout both bays!
With the aid of a one-hour training and orientation session prior to collecting data in the field, the volunteers were able to collect 125 points of usable data (i.e., data that were correctly referenced to GPS coordinates and contained all necessary information about seagrass presence/absence, seagrass coverage, and seagrass species composition). This year, more than 80% of all data collected were able to be included in the analyzed results. Great job, volunteers and volunteer trainers!
2016 Seagrass Survey Points:
This map shows the distribution and location of the 125 usable points that were surveyed during this year’s Seagrass Survey.
2016 Seagrass Survey Points Used in Results Analysis Compared to 2015 Survey Points:
The increased number of usable points for 2016 is a direct result of improved accuracy of recording GPS coordinates at each survey point, which was emphasized during the volunteer training.
Presence (P) and Absence (A) of Seagrass:
A total of 125 survey points were able to be used in this year’s results analysis. 121 points yielded a presence of seagrass. Four of the 125 survey points yielded an absence of seagrass; however, it was confirmed via GIS that those points were located geographically outside of seagrass bed boundaries (indicated by light and dark green areas in the above map).
Overall Seagrass Coverage:
Of the 121 usable survey points that yielded a presence of seagrass, the majority (42.98%) of seagrass coverage (abundance) was between 75 – 100%. This means that there was more seagrass (regardless of species) than bare bottom and other substrate types. This is great news for the marine life that rely on seagrass habitat because the more seagrass coverage there is, the more habitat and resources they have for food, shelter, and reproduction. It’s also great news for our water quality, since seagrasses help to remove nutrients. And, don’t forget that seagrasses help prevent sediment erosion (i.e., the more seagrass, the more stable our shorelines are)!
Additionally, an analysis of average percent coverage per species yielded these results:
• Thalassia = 61.23% (106 usable points)
• Syringodium = 49.29% (48 usable points)
• Halodule = 49.15% (66 usable points)
This indicates that, for the points analyzed, Thalassia beds were more continuous and lush (i.e., had greater than 50% bottom coverage) than either Syringodium or Halodule beds.
Seagrass Species Composition:
In general, the most common species of seagrass in Sarasota Bay are: Thalassia testudinum (turtle grass), Syringodium filiforme (manatee grass), and Halodule wrightii (shoal grass). All three of these species were found during the survey; the most frequently observed seagrass species overall was Thalassia testudinum at 53.72%, followed by Halodule wrightii at 28.51%, and Syringodium filiforme at 17.77%. Thalassia tends to be located in deeper water, where perhaps it may be safer from boat props, and it tends to be more well-established than the other species. Thalassia is typically the most dominant seagrass species within seagrass beds in this area, and has the deepest roots among the three species. According to Seagrass Communities of the Gulf Coast of Florida: Status and Ecology, August 2004, Halodule has a shallow root system and is typically noted as a successional species (also known as a pioneer species, which is the first seagrass species to colonize an area, eventually leading to the establishment of other species over time). Halodule is also tolerant of lower salinity levels and shallower waters.
Epiphytic Algae Coverage:
119 out of 121 points surveyed had information about the level of epiphytic coverage (i.e., abundance of growth on seagrass blades). The most frequent level of epiphytic growth was moderate. This is a mid-range level, indicating that growth was neither extreme, nor were the blades free of growth. Because warmer weather and water temperatures promote increased algae growth, the level of epiphytic growth on seagrass is expected to increase as water temperatures rise through the summer season. Increased nutrient loads from fertilizers also increase algae growth. Although algae growth can be detrimental to seagrass in extreme cases (because it shades out sunlight necessary for seagrass to photosynthesize), some epiphytic growth is thought to enhance habitat, as it creates more shelter and protected cover for marine life that lives in seagrass beds.
Drift Algae Coverage:
Data from 120 survey points included information about drift algae coverage. 25 of these points showed no presence of drift algae; 38.33% of the remaining points had a low level of coverage, between 1 – 25%. This indicates that the majority of analyzed points did not have significant drift algae coverage, which is good news for seagrass! Additionally, only 2.5% of the points analyzed had 100% drift algae coverage plus a mass height of greater than 1 foot. Drift algae colonies can prevent sunlight from reaching seagrass beds, eventually killing seagrass or preventing its growth. Drift algae mats can be pushed by currents and wind activity, so they are constantly moving and shifting. Also, because it is not attached directly to seagrass, it can easily wash up on shore, where it decomposes. However, many organisms use drift algae for food and shelter, and oftentimes lay eggs within its mass.
Rooted Algae Coverage:
Of 113 usable data points for rooted algae, the majority of points (82.3%) yielded an absence of rooted algae while only 17.7% of the points indicated a presence of rooted algae. The majority of rooted algae abundance was between 1 – 25% (10.62%). This indicates that the majority of analyzed points did not have significant drift algae coverage. The most common species of rooted algae typically observed in Sarasota Bay is the genus Caulerpa. Volunteers were not asked to identify specific rooted algae species, only whether or not it was present and its percent coverage within each point surveyed.
Marine Life Observed:
Volunteers were asked to record living organisms that they observed within each survey point. A myriad of sea life was observed, including: sea urchins, sponges, whelks, tunicates, sea stars, horseshoe crabs, jellyfish, a wide variety of juvenile fish species, sea squirts, sea anemones, banded tulips, clams, tube worms, crabs, oysters, sea slugs, egg casings, barnacles, and even coral. Although qualitative, these observations emphasize the high productivity that seagrass beds can possess, and what is at stake in maintaining their health.
Conclusion: Data analyzed indicates that the seagrass beds surveyed during this year’s Seagrass Survey are, in general, productive and healthy (have a seagrass coverage of greater than 50% and host a wide variety of marine life, as well as display moderate epiphytic growth and a relatively low abundance of drift and rooted algae). Although seagrass acreage has increased in Sarasota Bay in recent years, it is important to appreciate that it is a fragile system that requires vigilant monitoring and restoration efforts. The individuals that have participated as volunteers and partners in the 2015 and 2016 seagrass surveys are local seagrass stewards, and we greatly appreciate their donation of time and energy in helping us to better understand our amazing seagrass beds!
2015 and 2016 Combined Survey Points
This map shows the distribution and location of usable data points surveyed by volunteers during both 2015 & 2016 Seagrass Survey events. Over the last two years, volunteers have produced 183 usable points of survey data!
The volunteer Seagrass Survey event and the Sarasota Environmental Aquatics (SEA) Team volunteer program are part of the broader Sarasota County Seagrass Monitoring Program. The annual volunteer outreach event aims at promoting awareness and education about the importance of seagrass habitat, and the roles that stormwater and runoff play on our local water resources. The Seagrass Survey event provides a free, fun, and family-oriented opportunity for community members to serve as citizen scientists while experiencing hands-on learning about seagrasses and data collection methods in the field.
The "Charting sea grass growth in the bay" story in the Sarasota Herald-Tribune has information about the 2011 Seagrass Survey volunteer event.
To become a SEA Team volunteer or for more information about the annual Volunteer Seagrass Survey, contact Nicole Iadevaia at 941-861-0635 or firstname.lastname@example.org.
Seagrass acreage is mapped via digital aerial photography by the Southwest Florida Water Management District (SWFWMD) every two years during the winter when the water clarity is the best. Once the aerials are converted to GIS maps, Sarasota County staff members perform underwater field surveys to verify seagrass beds identified in the maps. County staff conduct these surveys on an annual basis during the winter to provide continuity with the time of year that the aerial photographs are taken.
Title Image by James St. John
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